Drought and flooding have distinct effects on herbivore-induced responses and resistance in Solanum dulcamara.

Science.gov (United States)

Nguyen, Duy; D'Agostino, Nunzio; Tytgat, Tom O G; Sun, Pulu; Lortzing, Tobias; Visser, Eric J W; Cristescu, Simona M; Steppuhn, Anke; Mariani, Celestina; van Dam, Nicole M; Rieu, Ivo

2016-07-01

In the field, biotic and abiotic stresses frequently co-occur. As a consequence, common molecular signalling pathways governing adaptive responses to individual stresses can interact, resulting in compromised phenotypes. How plant signalling pathways interact under combined stresses is poorly understood. To assess this, we studied the consequence of drought and soil flooding on resistance of Solanum dulcamara to Spodoptera exigua and their effects on hormonal and transcriptomic profiles. The results showed that S. exigua larvae performed less well on drought-stressed plants than on well-watered and flooded plants. Both drought and insect feeding increased abscisic acid and jasmonic acid (JA) levels, whereas flooding did not induce JA accumulation. RNA sequencing analyses corroborated this pattern: drought and herbivory induced many biological processes that were repressed by flooding. When applied in combination, drought and herbivory had an additive effect on specific processes involved in secondary metabolism and defence responses, including protease inhibitor activity. In conclusion, drought and flooding have distinct effects on herbivore-induced responses and resistance. Especially, the interaction between abscisic acid and JA signalling may be important to optimize plant responses to combined drought and insect herbivory, making drought-stressed plants more resistant to insects than well-watered and flooded plants. © 2016 John Wiley & Sons Ltd.

Induction of drought tolerant mutants of rice

International Nuclear Information System (INIS)

El-Hissewy, A.A.; Abd Allah, A.

2001-01-01

The ultimate goal of crop breeding is to develop varieties with a high yield potential and desirable agronomic characteristics. In Egypt, the most important qualities sought by breeders have been high yield potential, resistance to major diseases and insects, and improved grain and eating quality. However, breeding efforts should concentrate on varieties with the potential to minimize yield losses under unfavorable conditions such as drought, and to maximize yields when conditions are favorable. Rice (Oryza sativa L.) in Egypt is completely irrigated and a significant portion of the rice cultivated area is subject to water deficit resulting from an inadequate or insufficient irrigation supply. Drought tolerance is a complex trait in that it results from the interaction of histological and physiological characters of plant with environmental factors, both above-ground and under-ground. Accordingly, root characters are closely related to drought tolerance. Little attention has been paid in Egyptian breeding programs to root characters and their relation to shoot characters. Furthermore, induced mutations are considered as one of the most important methods to induce useful mutants, especially with improved root characters, to overcome the drought problem. The present investigation aimed to study the effect of different doses of gamma rays on several characters of three Egyptian rice varieties, i.e. 'Giza 171', 'Giza 175' and 'Giza 176' and to induce one or more mutants possessing drought tolerance

A multi-species synthesis of physiological mechanisms in drought-induced tree mortality

Energy Technology Data Exchange (ETDEWEB)

Adams, Henry D.; Zeppel, Melanie J. B.; Anderegg, William R. L.; Hartmann, Henrik; Landhäusser, Simon M.; Tissue, David T.; Huxman, Travis E.; Hudson, Patrick J.; Franz, Trenton E.; Allen, Craig D.; Anderegg, Leander D. L.; Barron-Gafford, Greg A.; Beerling, David J.; Breshears, David D.; Brodribb, Timothy J.; Bugmann, Harald; Cobb, Richard C.; Collins, Adam D.; Dickman, L. Turin; Duan, Honglang; Ewers, Brent E.; Galiano, Lucía; Galvez, David A.; Garcia-Forner, Núria; Gaylord, Monica L.; Germino, Matthew J.; Gessler, Arthur; Hacke, Uwe G.; Hakamada, Rodrigo; Hector, Andy; Jenkins, Michael W.; Kane, Jeffrey M.; Kolb, Thomas E.; Law, Darin J.; Lewis, James D.; Limousin, Jean-Marc; Love, David M.; Macalady, Alison K.; Martínez-Vilalta, Jordi; Mencuccini, Maurizio; Mitchell, Patrick J.; Muss, Jordan D.; O’Brien, Michael J.; O’Grady, Anthony P.; Pangle, Robert E.; Pinkard, Elizabeth A.; Piper, Frida I.; Plaut, Jennifer A.; Pockman, William T.; Quirk, Joe; Reinhardt, Keith; Ripullone, Francesco; Ryan, Michael G.; Sala, Anna; Sevanto, Sanna; Sperry, John S.; Vargas, Rodrigo; Vennetier, Michel; Way, Danielle A.; Xu, Chonggang; Yepez, Enrico A.; McDowell, Nate G.

2017-08-07

Widespread tree mortality associated with drought has been observed on all forested continents, and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water, and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analyzed across species and biomes using a standardized physiological framework. Here we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought-induced mortality. All species assessed had 60% or greater loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrates at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in hydraulic deterioration. The consistent Our finding that across species of hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function.

A multi-species synthesis of physiological mechanisms in drought-induced tree mortality.

Science.gov (United States)

Adams, Henry D; Zeppel, Melanie J B; Anderegg, William R L; Hartmann, Henrik; Landhäusser, Simon M; Tissue, David T; Huxman, Travis E; Hudson, Patrick J; Franz, Trenton E; Allen, Craig D; Anderegg, Leander D L; Barron-Gafford, Greg A; Beerling, David J; Breshears, David D; Brodribb, Timothy J; Bugmann, Harald; Cobb, Richard C; Collins, Adam D; Dickman, L Turin; Duan, Honglang; Ewers, Brent E; Galiano, Lucía; Galvez, David A; Garcia-Forner, Núria; Gaylord, Monica L; Germino, Matthew J; Gessler, Arthur; Hacke, Uwe G; Hakamada, Rodrigo; Hector, Andy; Jenkins, Michael W; Kane, Jeffrey M; Kolb, Thomas E; Law, Darin J; Lewis, James D; Limousin, Jean-Marc; Love, David M; Macalady, Alison K; Martínez-Vilalta, Jordi; Mencuccini, Maurizio; Mitchell, Patrick J; Muss, Jordan D; O'Brien, Michael J; O'Grady, Anthony P; Pangle, Robert E; Pinkard, Elizabeth A; Piper, Frida I; Plaut, Jennifer A; Pockman, William T; Quirk, Joe; Reinhardt, Keith; Ripullone, Francesco; Ryan, Michael G; Sala, Anna; Sevanto, Sanna; Sperry, John S; Vargas, Rodrigo; Vennetier, Michel; Way, Danielle A; Xu, Chonggang; Yepez, Enrico A; McDowell, Nate G

2017-09-01

Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere-atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analysed across species and biomes using a standardized physiological framework. Here, we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought-induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function.

A multi-species synthesis of physiological mechanisms in drought-induced tree mortality

Science.gov (United States)

Adams, Henry D.; Zeppel, Melanie; Anderegg, William R.L.; Hartmann, Henrik; Landhäusser, Simon M.; Tissue, David T.; Huxman, Travis E.; Hudson, Patrick J.; Franz, Trenton E.; Allen, Craig D.; Anderegg, Leander D. L.; Barron-Gafford, Greg A.; Beerling, David; Breshears, David D.; Brodribb, Timothy J.; Bugmann, Harald; Cobb, Richard C.; Collins, Adam D.; Dickman, L. Turin; Duan, Honglang; Ewers, Brent E.; Galiano, Lucia; Galvez, David A.; Garcia-Forner, Núria; Gaylord, Monica L.; Germino, Matthew J.; Gessler, Arthur; Hacke, Uwe G.; Hakamada, Rodrigo; Hector, Andy; Jenkins, Michael W.; Kane, Jeffrey M.; Kolb, Thomas E.; Law, Darin J.; Lewis, James D.; Limousin, Jean-Marc; Love, David; Macalady, Alison K.; Martinez-Vilalta, Jordi; Mencuccini, Maurizio; Mitchell, Patrick J.; Muss, Jordan D.; O'Brien, Michael J.; O'Grady, Anthony P.; Pangle, Robert E.; Pinkard, Elizabeth A.; Piper, Frida I.; Plaut, Jennifer; Pockman, William T.; Quirk, Joe; Reinhardt, Keith; Ripullone, Francesco; Ryan, Michael G.; Sala, Anna; Sevanto, Sanna; Sperry, John S.; Vargas, Rodrigo; Vennetier, Michel; Way, Danielle A.; Wu, Chonggang; Yepez, Enrico A.; McDowell, Nate G.

2017-01-01

Widespread tree mortality associated with drought has been observed on all forested continents and global change is expected to exacerbate vegetation vulnerability. Forest mortality has implications for future biosphere–atmosphere interactions of carbon, water and energy balance, and is poorly represented in dynamic vegetation models. Reducing uncertainty requires improved mortality projections founded on robust physiological processes. However, the proposed mechanisms of drought-induced mortality, including hydraulic failure and carbon starvation, are unresolved. A growing number of empirical studies have investigated these mechanisms, but data have not been consistently analysed across species and biomes using a standardized physiological framework. Here, we show that xylem hydraulic failure was ubiquitous across multiple tree taxa at drought-induced mortality. All species assessed had 60% or higher loss of xylem hydraulic conductivity, consistent with proposed theoretical and modelled survival thresholds. We found diverse responses in non-structural carbohydrate reserves at mortality, indicating that evidence supporting carbon starvation was not universal. Reduced non-structural carbohydrates were more common for gymnosperms than angiosperms, associated with xylem hydraulic vulnerability, and may have a role in reducing hydraulic function. Our finding that hydraulic failure at drought-induced mortality was persistent across species indicates that substantial improvement in vegetation modelling can be achieved using thresholds in hydraulic function.

Drought-induced legacy effects in wood growth across the Eastern and Midwestern U.S. are mediated by site climate, tree age, and drought sensitivity

Science.gov (United States)

Kannenberg, S.; Maxwell, J. T.; Pederson, N.; D'Orangeville, L.; Phillips, R.

2017-12-01

While it is widely known that drought reduces carbon (C) uptake in temperate forests, tree growth can also remain stagnant post-drought despite favorable climatic conditions. While such "legacy effects" are well established, the degree to which these effects depend on species identity or variability in site conditions is poorly quantified. We sought to uncover how site, species, climate, and tree age interact to affect the presence and magnitude of legacy effects in temperate trees following drought. To do this, we assembled dendrochronological records of 18 common species across 94 sites in Eastern and Midwestern U.S. forests and quantified drought-induced changes in wood growth in the year of the drought (hereafter "drought sensitivity") and the years after the drought (i.e., legacy effects). We predicted that species particularly prone to hydraulic damage (e.g., oaks) would have the least drought sensitivity yet experience larger legacy effects, and that this effect would be exacerbated at arid sites. Across all species and sites, wood growth was reduced by 14% in the year of the drought and by 7% post-drought. Surprisingly, legacy effects were smaller for oak species and larger across species known to be more drought sensitive (e.g. tulip poplar, maple, birch). As a result, we observed a positive relationship between a species' drought sensitivity and that species' legacy effect. These legacy effects were similar in size across a range of drought severities. Surprisingly, legacy effects were smaller in more arid sites - contrary to previous investigations in dryland ecosystems - perhaps indicating the role of adaptation in mediating a tree's recovery from drought. In addition, many species actually decreased the size of their legacy effects as they aged, despite no change in drought responses. Our results run contrary to our predictions, as species with the greatest drought sensitivity had the least ability to recover, and that younger mesic forests- not arid

Glutathione-induced drought stress tolerance in mung bean: coordinated roles of the antioxidant defence and methylglyoxal detoxification systems

Science.gov (United States)

Nahar, Kamrun; Hasanuzzaman, Mirza; Alam, Md. Mahabub; Fujita, Masayuki

2015-01-01

Drought is considered one of the most acute environmental stresses presently affecting agriculture. We studied the role of exogenous glutathione (GSH) in conferring drought stress tolerance in mung bean (Vigna radiata L. cv. Binamoog-1) seedlings by examining the antioxidant defence and methylglyoxal (MG) detoxification systems and physiological features. Six-day-old seedlings were exposed to drought stress (−0.7 MPa), induced by polyethylene glycol alone and in combination with GSH (1 mM) for 24 and 48 h. Drought stress decreased seedling dry weight and leaf area; resulted in oxidative stress as evidenced by histochemical detection of hydrogen peroxide (H2O2) and O2⋅− in the leaves; increased lipid peroxidation (malondialdehyde), reactive oxygen species like H2O2 content and O2⋅− generation rate and lipoxygenase activity; and increased the MG level. Drought decreased leaf succulence, leaf chlorophyll and relative water content (RWC); increased proline (Pro); decreased ascorbate (AsA); increased endogenous GSH and glutathione disulfide (GSSG) content; decreased the GSH/GSSG ratio; increased ascorbate peroxidase and glutathione S-transferase activities; and decreased the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase. The activities of glyoxalase I (Gly I) and glyoxalase II (Gly II) increased due to drought stress. In contrast to drought stress alone, exogenous GSH enhanced most of the components of the antioxidant and glyoxalase systems in drought-affected mung bean seedlings at 24 h, but GSH did not significantly affect AsA, Pro, RWC, leaf succulence and the activities of Gly I and DHAR after 48 h of stress. Thus, exogenous GSH supplementation with drought significantly enhanced the antioxidant components and successively reduced oxidative damage, and GSH up-regulated the glyoxalase system and reduced MG toxicity, which played a significant role in improving the physiological features and drought

Drought timing and local climate determine the sensitivity of eastern temperate forests to drought.

Science.gov (United States)

D'Orangeville, Loïc; Maxwell, Justin; Kneeshaw, Daniel; Pederson, Neil; Duchesne, Louis; Logan, Travis; Houle, Daniel; Arseneault, Dominique; Beier, Colin M; Bishop, Daniel A; Druckenbrod, Daniel; Fraver, Shawn; Girard, François; Halman, Joshua; Hansen, Chris; Hart, Justin L; Hartmann, Henrik; Kaye, Margot; Leblanc, David; Manzoni, Stefano; Ouimet, Rock; Rayback, Shelly; Rollinson, Christine R; Phillips, Richard P

2018-02-20

Projected changes in temperature and drought regime are likely to reduce carbon (C) storage in forests, thereby amplifying rates of climate change. While such reductions are often presumed to be greatest in semi-arid forests that experience widespread tree mortality, the consequences of drought may also be important in temperate mesic forests of Eastern North America (ENA) if tree growth is significantly curtailed by drought. Investigations of the environmental conditions that determine drought sensitivity are critically needed to accurately predict ecosystem feedbacks to climate change. We matched site factors with the growth responses to drought of 10,753 trees across mesic forests of ENA, representing 24 species and 346 stands, to determine the broad-scale drivers of drought sensitivity for the dominant trees in ENA. Here we show that two factors-the timing of drought, and the atmospheric demand for water (i.e., local potential evapotranspiration; PET)-are stronger drivers of drought sensitivity than soil and stand characteristics. Drought-induced reductions in tree growth were greatest when the droughts occurred during early-season peaks in radial growth, especially for trees growing in the warmest, driest regions (i.e., highest PET). Further, mean species trait values (rooting depth and ψ 50 ) were poor predictors of drought sensitivity, as intraspecific variation in sensitivity was equal to or greater than interspecific variation in 17 of 24 species. From a general circulation model ensemble, we find that future increases in early-season PET may exacerbate these effects, and potentially offset gains in C uptake and storage in ENA owing to other global change factors. © 2018 John Wiley & Sons Ltd.

A dehydrin gene isolated from feral olive enhances drought tolelance

Directory of Open Access Journals (Sweden)

Adriana eChiappetta

2015-06-01

Full Text Available Dehydrins belong to a protein family whose expression may be induced or enhanced by developmental process and environmental stresses that lead to cell dehydratation. A dehydrin gene named OesDHN was isolated and characterized from oleaster (Olea europaea L. subsp. europaea, var. sylvestris, the wild form of olive.To elucidate the contribution of OesDHN in the development of drought tolerance, its expression levels were investigated in oleaster plants during development and under drought stress condition. The involvement of OesDHN in plant stress response was also evaluated in Arabidopsis transgenic lines, engineered to overexpress this gene, and exposed to a controlled mild osmotic stress. OesDHN expression was found to be modulated during development and induced under mild drought stress in oleaster plants. In addition, the Arabidopsis transgenic plants showed a better tolerance to osmotic stress than wild-type plants. The results demonstrated that OesDHN expression is induced by drought stress and is able to confer osmotic stress tolerance. We suggest a role for OesDHN, as a putative functional marker of plant stress tolerance.

Plant Water Content is the Best Predictor of Drought-induced Mortality

Science.gov (United States)

Sapes, G.; Roskilly, B.; Dobrowski, S.; Sala, A.

2017-12-01

Predicting drought-induced forest mortality remains extremely challenging. Recent research has shown that both plant hydraulics and stored non-structural carbohydrates (NSC) interact during drought-induced mortality. The strong interaction between these two variables and the fact that they are both difficult to measure render drought-induced plant mortality extremely difficult to monitor and predict. A variable that is easier to measure and that integrates hydraulic transport and carbohydrate dynamics may, therefore, improve our ability to monitor and predict mortality. Here, we tested whether plant water content is such an integrator variable and, therefore, a better predictor of mortality under drought. We subjected 250 two-year-old ponderosa pine seedlings to drought until they died in a greenhouse experiment. Periodically during the dry down, we measured percent loss of hydraulic conductivity (PLC), NSC concentration (starch and soluble sugars), and tissue volumetric water content (VWC) in roots, stems and leaves. At each measurement time, a separate set of seedlings were re-watered to estimate the probability of mortality at the population level. Linear models were used to explore whether PLC and NSC were linked to VWC and to determine which of the three variables predicted mortality the best. As expected, plants lost hydraulic conductivity in stems and roots during the dry down. Starch concentrations also decreased in all organs as the drought proceeded. In contrast, soluble sugars increased in stems and roots, consistent with the conversion of stored NSCs into osmotically active compounds. Models containing both PLC and NSC concentrations as predictors of VWC were highly significant in all organs and at the whole plant level, indicating that water content is influenced by both PLC and NSCs. PLC, NSC, and VWC explained mortality across organs and at the whole plant level, but VWC was the best predictor (R2 = 0.99). Our results indicate that plant water

Are Scots pine forest edges particularly prone to drought-induced mortality?

Science.gov (United States)

Buras, Allan; Schunk, Christian; Zeiträg, Claudia; Herrmann, Corinna; Kaiser, Laura; Lemme, Hannes; Straub, Christoph; Taeger, Steffen; Gößwein, Sebastian; Klemmt, Hans-Joachim; Menzel, Annette

2018-02-01

Climate change is expected to exacerbate the frequency of drought-induced tree mortality world-wide. To better predict the associated change of species composition and forest dynamics on various scales and develop adequate adaptation strategies, more information on the mechanisms driving the often observed patchiness of tree die-back is needed. Although forest-edge effects may play an important role within the given context, only few corresponding studies exist. Here, we investigate the regional die-back of Scots pine in Franconia, Germany, after a hot and dry summer in 2015, thereby emphasizing possible differences in mortality between forest edge and interior. By means of dendroecological investigations and close-range remote sensing, we assess long-term growth performance and current tree vitality along five different forest-edge distance gradients. Our results clearly indicate a differing growth performance between edge and interior trees, associated with a higher vulnerability to drought, increased mortality rates, and lower tree vitality at the forest edge. Prior long-lasting growth decline of dead trees compared to live trees suggests depletion of carbon reserves in course of a long-term drought persisting since the 1990s to be the cause of regional Scots pine die-back. These findings highlight the forest edge as a potential focal point of forest management adaptation strategies in the context of drought-induced mortality.

Isolation of Mycorrhizal Rhizoctonia as resistance inducer of Dendrobium macrophyllum to drought

Science.gov (United States)

Soelistijono, R.; Daryanti; Handayani, M. T.

2018-03-01

One of the obstacles encountered in the cultivation of orchids Dendrobium macrophyllum is difficult to cultivate in areas with high drought due to the slow absorption of nutrients. Based on previous research, the mycorrhizal binucleate Rhizoctonia (BNR) has the ability to increase the resistance of vanilla (Vanilla planifolia Andrews) to drought, but it has never been tried on orchid Dendrobium macrophyllum. The objectives of this study was to isolate resistance inducer organisms by induced resistance techniques on orchids against drought. It is expected that the administration of mycorrhizal Rhizoctonia can increase the absorption of nutrients in D. macrophyllum which is exposed to high water stress. Each treatment consisted of 3 replications of 3 potted plants. The characterization of mycorrhizal Rhizoctonia isolate from D. macrophyllum root from Surakarta, Kopeng, Magelang, and Yogyakarta did not different morphologically. Character equations are in colony color, cell length and number of cores, while character differences are present in cell width and all isolates are capable of forming a peloton structure.

Characterizing gene responses to drought stress in fourwing saltbush [Atriplex canescens (Pursh.) Nutt.)

Science.gov (United States)

Linda S. Adair; David L. Andrews; John Cairney; Edward A. Funkhouser; Ronald J. Newton; Earl F. Aldon

1992-01-01

New techniques in molecular biology can be used to characterize genes whose expression is induced by drought stress. These techniques can be used to understand responses of range plants to environmental stresses at the biochemical and molecular level. For example, they can be used to characterize genes that respond to drought stress conditions in the native shrub

Abscisic Acid and Cytokinin-Induced Osmotic and Antioxidant Regulation in Two Drought-Tolerant and Drought-Sensitive Cultivars of Wheat During Grain Filling Under Water Deficit in Field Conditions

Directory of Open Access Journals (Sweden)

Mohammad-Reza SARAFRAZ-ARDAKANI

2014-09-01

Full Text Available Phytohormones play critical roles in regulating plant responses to stress. The present study investigates the effect of cytokinin, abscisic acid and cytokinin/abscisic acid interaction on some osmoprotectants and antioxidant parameters induced by drought stress in two wheat cultivars (Triticum aestivum L. of ‘Pishgam’ and ‘MV-17’ as tolerant and sensitive to drought during post-anthesis phase, respectively grown in field conditions. The most considerable effect of the treatments was exhibited 21 days after anthesis. Under drought conditions, the flag leaf soluble carbohydrate content increased in both cultivars while starch content was remarkably decreased in ‘Pishgam’ as compared to ‘MV-17’. Abscisic acid increased total soluble sugar and reduced starch more than other hormonal treatments, although it decreased studied monosaccharaides in ‘Pishgam’, especially. Drought stress induced high proportion of gylycinebetain and free proline in ‘Pishgam’ cultivar. Application of abscisic acid and cytokinin/abscisic acid interaction increased gylycinebetain and proline content in both cultivars under irrigation and drought conditions. The tolerant cultivar exhibited less accumulation of hydrogen peroxide and malondialdehyde in relation to significant increase of catalase and peroxidase activities and α-tocpherol content under drought conditions. All hormonal treatments increased the named enzyme activities under both irrigation and drought conditions, while higher accumulation of α-tocopherol was only showed in case of cytokinin application. Also, abscisic acid and cytokinin/abscisic acid could decrease drought-induced hydrogen peroxide and malondialdehyde level to some extent, although abscisic acid increased both of hydrogen peroxide andmalondialdehyde content in irrigation phase, especially.

[Effects of Ca2+ on nitric oxide-induced adventitious rooting in cucumber under drought stress].

Science.gov (United States)

Li, Chun Lan; Niu, Li Juan; Hu, Lin Li; Liao, Wei Biao; Chen, Yue

2017-11-01

Cucumber (Cucumis sativus L. 'Xinchun 4') was used to explore the relationship between nitric oxide (NO) and calcium (Ca 2+ ) during adventitious rooting under drought stress. Rooting parameters, endogenous Ca 2+ fluorescent intensity and the antioxidant enzymes activity (SOD, CAT and APX) in cucumber explants under drought stress were investigated. The results showed that treatment with 200 μmol·L -1 CaCl 2 and 0.05% PEG significantly improved the number and length of adventitious root in cucumber explants under drought stress, while the application of Ca 2+ chelating agent (EGTA) and channel inhibitor (BAPTA/AM) significantly decreased NO-induced number and length of adventitious root under drought stress. Under drought stress, the fluorescence intensity of Ca 2+ in hypocotyls treated with NO and CaCl 2 was improved, however, the Ca 2+ fluorescence intensity in the hypocotyls treated with NO scavenger (cPTIO) was significantly lower than that in the hypocotyls treated with NO. Under drought stress, the activities of antioxidant enzymes in the cucumber explants were significantly promoted by the treatments with NO and CaCl 2 , however, Ca 2+ chelating agent and channel inhibitor significantly decreased the activity of antioxidant enzymes induced by NO. In conclusion, Ca 2+ might be involved in the process of NO-adjusted antioxidant enzymes activity during adventitious rooting under drought stress, which alleviated the negative effects of drought on the adventitious rooting and promoted the formation of adventitious roots.

Ectomycorrhizal inoculation with Pisolithus tinctorius reduces stress induced by drought in cork oak.

Science.gov (United States)

Sebastiana, Mónica; da Silva, Anabela Bernardes; Matos, Ana Rita; Alcântara, André; Silvestre, Susana; Malhó, Rui

2018-04-01

We investigated whether the performance of cork oak under drought could be improved by colonization with the ectomycorrhizal fungus Pisolithus tinctorius. Results show that inoculation alone had a positive effect on plant height, shoot biomass, shoot basal diameter, and root growth. Under drought, root growth of mycorrhizal plants was significantly increased showing that inoculation was effective in increasing tolerance to drought. In accordance, mycorrhizal plants subjected to drought showed less symptoms of stress when compared to non-mycorrhizal plants, such as lower concentration of soluble sugars and starch, increased ability to maintain fatty acid content and composition, and increased unsaturation level of membrane lipids. After testing some of the mechanisms suggested to contribute to the enhanced tolerance of mycorrhizal plants to drought, we could not find any by which Pisolithus tinctorius could benefit cork oak, at least under the drought conditions imposed in our experiment. Inoculation did not increase photosynthesis under drought, suggesting no effect in sustaining stomatal opening at low soil water content. Similarly, plant water status was not affected by inoculation suggesting that P. tinctorius does not contribute to an increased plant water uptake during drought. Inoculation did increase nitrogen concentration in plants but it was independent of the water status. Furthermore, no significant mycorrhizal effect on drought-induced ROS production or osmotic adjustment was detected, suggesting that these factors are not important for the improved drought tolerance triggered by P. tinctorius.

Precipitation thresholds and drought-induced tree die-off: insights from patterns of Pinus edulis mortality along an environmental stress gradient.

Science.gov (United States)

Clifford, Michael J; Royer, Patrick D; Cobb, Neil S; Breshears, David D; Ford, Paulette L

2013-10-01

Recent regional tree die-off events appear to have been triggered by a combination of drought and heat - referred to as 'global-change-type drought'. To complement experiments focused on resolving mechanisms of drought-induced tree mortality, an evaluation of how patterns of tree die-off relate to highly spatially variable precipitation is needed. Here, we explore precipitation relationships with a die-off event of pinyon pine (Pinus edulis Engelm.) in southwestern North America during the 2002-2003 global-change-type drought. Pinyon die-off and its relationship with precipitation was quantified spatially along a precipitation gradient in north-central New Mexico with standard field plot measurements of die-off combined with canopy cover derived from normalized burn ratio (NBR) from Landsat imagery. Pinyon die-off patterns revealed threshold responses to precipitation (cumulative 2002-2003) and vapor pressure deficit (VPD), with little to no mortality (< 10%) above 600 mm and below warm season VPD of c. 1.7 kPa. [Correction added after online publication 17 June 2013; in the preceding sentence, the word 'below' has been inserted.] Our results refine how precipitation patterns within a region influence pinyon die-off, revealing a precipitation and VPD threshold for tree mortality and its uncertainty band where other factors probably come into play - a response type that influences stand demography and landscape heterogeneity and is of general interest, yet has not been documented. © 2013 No claim to US Government works. New Phytologist © 2013 New Phytologist Trust.

Drought, Agriculture, and Labor: Understanding Drought Impacts and Vulnerability in California

Science.gov (United States)

Greene, C.

2015-12-01

Hazardous drought impacts are a product of not only the physical intensity of drought, but also the economic, social, and environmental characteristics of the region exposed to drought. Drought risk management requires understanding the complex links between the physical and human dimensions of drought. Yet, there is a research gap in identifying and explaining the socio-economic complexities of drought in the context of the first world, especially for economic and socially marginal groups who rely on seasonal and temporary jobs. This research uses the current drought in California as a case study to identify the socioeconomic impacts of drought on farmworker communities in California's San Joaquin Valley, with a specific focus on the relationship between drought and agricultural labor. Through both a narrative analysis of drought coverage in newspaper media, drought policy documents, and interviews with farmworkers, farmers, community based organizations, and government officials in the San Joaquin Valley, this research aims to highlight the different understandings and experiences of the human impacts of drought and drought vulnerability in order to better inform drought risk planning and policy.

California's Drought - Stress test for the future

Science.gov (United States)

Lund, J. R.

2014-12-01

The current California drought is in its third dry years, with this year being the third driest years in a 106-year record. This drought occurs at a time when urban, agricultural, and environmental water demands have never been greater. This drought has revealed the importance of more quantitative evaluation and methods for water assessment and management. All areas of water and environmental management are likely to become increasingly stressed, and have essentially drought-like conditions, in the future, as California's urban, agricultural, and environmental demands continue to expand and as the climate changes. In the historical past, droughts have pre-viewed stresses developing in the future and helped focus policy-makers, the public, and stakeholders on preparing for these developing future conditions. Multi-decade water management strategies are often galvinized by drought. Irrigation was galvanized by California droughts in the 1800s, reservoir systems by the 1928-32 drought, urban water conservation by the 1976-77 drought, and water markets by the 1988-92 drought. With each drought, demands for tighter accounting, rights, and management have increased. This talk reviews the prospects and challenges for increased development and use of water data and systems analysis in the service of human and environmental water demands in California's highly decentralized water management system, and the prospects if these challenges are not more successfully addressed.

Physiological mechanisms of drought-induced tree die-off in relation to carbon, hydraulic and respiratory stress in a drought-tolerant woody plant.

Science.gov (United States)

Saiki, Shin-Taro; Ishida, Atsushi; Yoshimura, Kenichi; Yazaki, Kenichi

2017-06-07

Drought-induced tree die-off related to climate change is occurring worldwide and affects the carbon stocks and biodiversity in forest ecosystems. Hydraulic failure and carbon starvation are two commonly proposed mechanisms for drought-induced tree die-off. Here, we show that inhibited branchlet respiration and soil-to-leaf hydraulic conductance, likely caused by cell damage, occur prior to hydraulic failure (xylem embolism) and carbon starvation (exhaustion of stored carbon in sapwood) in a drought-tolerant woody species, Rhaphiolepis wrightiana Maxim. The ratio of the total leaf area to the twig sap area was used as a health indicator after drought damage. Six adult trees with different levels of tree health and one dead adult tree were selected. Two individuals having the worst and second worst health among the six live trees died three months after our study was conducted. Soil-to-leaf hydraulic conductance and leaf gas exchange rates decreased linearly as tree health declined, whereas xylem cavitation and total non-structural carbon remained unchanged in the branchlets except in the dead and most unhealthy trees. Respiration rates and the number of living cells in the sapwood decreased linearly as tree health declined. This study is the first report on the importance of dehydration tolerance and respiration maintenance in living cells.

Transcriptome Analysis of Induced Systemic Drought Tolerance Elicited by Pseudomonas chlororaphis O6 in Arabidopsis thaliana

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Song-Mi Cho

2013-06-01

Full Text Available Root colonization by Pseudomonas chlororaphis O6 induces systemic drought tolerance in Arabidopsis thaliana. Microarray analysis was performed using the 22,800-gene Affymetrix GeneChips to identify differentially-expressed genes from plants colonized with or without P. chlororaphis O6 under drought stressed conditions or normal growth conditions. Root colonization in plants grown under regular irrigation condition increased transcript accumulation from genes associated with defense, response to reactive oxygen species, and auxin- and jasmonic acid-responsive genes, but decreased transcription factors associated with ethylene and abscisic acid signaling. The cluster of genes involved in plant disease resistance were up-regulated, but the set of drought signaling response genes were down-regulated in the P. chlororaphis O6-colonized under drought stress plants compared to those of the drought stressed plants without bacterial treatment. Transcripts of the jasmonic acid-marker genes, VSP1 and pdf-1.2, the salicylic acid regulated gene, PR-1, and the ethylene-response gene, HEL, also were up-regulated in plants colonized by P. chlororaphis O6, but differed in their responsiveness to drought stress. These data show how gene expression in plants lacking adequate water can be remarkably influenced by microbial colonization leading to plant protection, and the activation of the plant defense signal pathway induced by root colonization of P. chlororaphis O6 might be a key element for induced systemic tolerance by microbes.

Monitoring and Assessing the 2012 Drought in the Great Plains: Analyzing Satellite-Retrieved Solar-Induced Chlorophyll Fluorescence, Drought Indices, and Gross Primary Production

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Siheng Wang

2016-01-01

Full Text Available We examined the relationship between satellite measurements of solar-induced chlorophyll fluorescence (SIF and several meteorological drought indices, including the multi-time-scale standard precipitation index (SPI and the Palmer drought severity index (PDSI, to evaluate the potential of using SIF to monitor and assess drought. We found significant positive relationships between SIF and drought indices during the growing season (from June to September. SIF was found to be more sensitive to short-term SPIs (one or two months and less sensitive to long-term SPI (three months than were the normalized difference vegetation index (NDVI or the normalized difference water index (NDWI. Significant correlations were found between SIF and PDSI during the growing season for the Great Plains. We found good consistency between SIF and flux-estimated gross primary production (GPP for the years studied, and synchronous declines of SIF and GPP in an extreme drought year (2012. We used SIF to monitor and assess the drought that occurred in the Great Plains during the summer of 2012, and found that although a meteorological drought was experienced throughout the Great Plains from June to September, the western area experienced more agricultural drought than the eastern area. Meanwhile, SIF declined more significantly than NDVI during the peak growing season. Yet for senescence, during which time the reduction of NDVI still went on, the reduction of SIF was eased. Our work provides an alternative to traditional reflectance-based vegetation or drought indices for monitoring and assessing agricultural drought.

Large-scale drought-induced vegetation die-off: expanding the ecohydrological emphasis more explicitly on atmospheric demand. (Invited)

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Breshears, D. D.; Adams, H. D.; Eamus, D.; McDowell, N. G.; Law, D. J.; Will, R. E.; Williams, P.; Zou, C.

2013-12-01

Ecohydrology focuses on the interactions of water availability, ecosystem productivity, and biogeochemical cycles via ecological-hydrological connections. These connections can be particularly pronounced and socially relevant when there are large-scale rapid changes in vegetation. One such key change, vegetation mortality, can be triggered by drought and is projected to become more frequent and/or extensive in the future under changing climate. Recent research on drought-induced vegetation die-off has focused primarily on direct drought effects, such as soil moisture deficit, and, to a much lesser degree, the potential for warmer temperatures to exacerbate stress and accelerate mortality. However, temperature is tightly interrelated with atmospheric demand (vapor pressure deficit, VPD) but the latter has rarely been considered explicitly relative to die-off events. Here we highlight the importance of VPD in addition to soil moisture deficit and warmer temperature as an important driver of future die-off. Recent examples highlighting the importance of VPD include mortality patterns corresponding to VPD drivers, a strong dependence of forest growth on VPD, patterns of observed mortality along an environmental gradient, an experimentally-determined climate envelope for mortality, and a suite of modeling simulations segregating the drought effects of VPD from those of temperature. The vast bulk of evidence suggests that atmospheric demand needs to be considered in addition to temperature and soil moisture deficit in predicting risk of future vegetation die-off and associated ecohydrological transformations.

Exogenous Application of GABA Improves PEG-Induced Drought Tolerance Positively Associated with GABA-Shunt, Polyamines, and Proline Metabolism in White Clover.

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Yong, Bin; Xie, Huan; Li, Zhou; Li, Ya-Ping; Zhang, Yan; Nie, Gang; Zhang, Xin-Quan; Ma, Xiao; Huang, Lin-Kai; Yan, Yan-Hong; Peng, Yan

2017-01-01

In order to investigate the physiological effects of exogenous γ-aminobutyric acid (GABA) on drought tolerance in white clover (Trifolium repens), GABA shunt, polyamines (PAs), and proline (Pro) metabolism were examined after plants pretreated with or without GABA (8 mM) and then exposed to water or 15% PEG-induced drought stress in growth chamber. In this study, exogenous application of GABA effectively alleviated drought-induced damage in leaves, as reflected by significantly higher relative water content, lower electrolyte leakage, lipid peroxidation, and leaf wilt. Exogenous GABA further promoted drought-induced increases in GABA transaminase and alpha ketone glutarate dehydrogenase activities, but inhibited glutamate decarboxylase activity under both control and drought conditions, resulting in an increase in endogenous glutamate (Glu) and GABA content. Besides, exogenous GABA could well accelerated PAs synthesis and suppressed PAs catabolism, which lead to the extremely enhanced different types of PAs content (free Put and Spd, insoluble bound Spd and Spm, soluble conjugated Spd and Spm, and total Put, Spd and Spm) under drought stress. In addition, exogenous GABA application further activated drought-induced Δ 1 -pyrroline-5-carboxylate synthetase and proline dehydrogenase activities, but suppressed drought-facilitated ornithine -δ-amino transferase activities, leading to a higher Pro accumulation and metabolism in GABA-pretreated plants in the middle and last period of drought. The results suggested that increased endogenous GABA by exogenous GABA treatment could improve drought tolerance of white clover associated with a positive regulation in the GABA-shunt, PAs and Pro metabolism.

Effect of drought stress induced by polyethylene glycol (PEG) on ...

African Journals Online (AJOL)

use

2011-12-12

Dec 12, 2011 ... Corn is an important cereal crop grown all over the world. (Farhad et al., 2009). Also, it is a stable food and commercial crop (Ti-da et al., 2006). On the other hand, drought stress is one of the most important environmental factors in reduction of growth, development and production of plants. It can be said ...

Stress-inducible expression of AtDREB1A transcription factor greatly improves drought stress tolerance in transgenic indica rice.

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Ravikumar, G; Manimaran, P; Voleti, S R; Subrahmanyam, D; Sundaram, R M; Bansal, K C; Viraktamath, B C; Balachandran, S M

2014-06-01

The cultivation of rice (Oryza sativa L.), a major food crop, requires ample water (30 % of the fresh water available worldwide), and its productivity is greatly affected by drought, the most significant environmental factor. Much research has focussed on identifying quantitative trait loci, stress-regulated genes and transcription factors that will contribute towards the development of climate-resilient/tolerant crop plants in general and rice in particular. The transcription factor DREB1A, identified from the model plant Arabidopsis thaliana, has been reported to enhance stress tolerance against drought stress. We developed transgenic rice plants with AtDREB1A in the background of indica rice cultivar Samba Mahsuri through Agrobacterium-mediated transformation. The AtDREB1A gene was stably inherited and expressed in T1 and T2 plants and in subsequent generations, as indicated by the results of PCR, Southern blot and RT-PCR analyses. Expression of AtDREB1A was induced by drought stress in transgenic rice lines, which were highly tolerant to severe water deficit stress in both the vegetative and reproductive stages without affecting their morphological or agronomic traits. The physiological studies revealed that the expression of AtDREB1A was associated with an increased accumulation of the osmotic substance proline, maintenance of chlorophyll, increased relative water content and decreased ion leakage under drought stress. Most of the homozygous lines were highly tolerant to drought stress and showed significantly a higher grain yield and spikelet fertility relative to the nontransgenic control plants under both stressed and unstressed conditions. The improvement in drought stress tolerance in combination with agronomic traits is very essential in high premium indica rice cultivars, such as Samba Mahsuri, so that farmers can benefit in times of seasonal droughts and water scarcity.

The Arabidopsis transcription factor ABIG1 relays ABA signaled growth inhibition and drought induced senescence.

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Liu, Tie; Longhurst, Adam D; Talavera-Rauh, Franklin; Hokin, Samuel A; Barton, M Kathryn

2016-10-04

Drought inhibits plant growth and can also induce premature senescence. Here we identify a transcription factor, ABA INSENSITIVE GROWTH 1 (ABIG1) required for abscisic acid (ABA) mediated growth inhibition, but not for stomatal closure. ABIG1 mRNA levels are increased both in response to drought and in response to ABA treatment. When treated with ABA, abig1 mutants remain greener and produce more leaves than comparable wild-type plants. When challenged with drought, abig1 mutants have fewer yellow, senesced leaves than wild-type. Induction of ABIG1 transcription mimics ABA treatment and regulates a set of genes implicated in stress responses. We propose a model in which drought acts through ABA to increase ABIG1 transcription which in turn restricts new shoot growth and promotes leaf senescence. The results have implications for plant breeding: the existence of a mutant that is both ABA resistant and drought resistant points to new strategies for isolating drought resistant genetic varieties.

Estimating drought risk across Europe from reported drought impacts, drought indices, and vulnerability factors

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Blauhut, Veit; Stahl, Kerstin; Stagge, James Howard; Tallaksen, Lena M.; De Stefano, Lucia; Vogt, Jürgen

2016-07-01

Drought is one of the most costly natural hazards in Europe. Due to its complexity, drought risk, meant as the combination of the natural hazard and societal vulnerability, is difficult to define and challenging to detect and predict, as the impacts of drought are very diverse, covering the breadth of socioeconomic and environmental systems. Pan-European maps of drought risk could inform the elaboration of guidelines and policies to address its documented severity and impact across borders. This work tests the capability of commonly applied drought indices and vulnerability factors to predict annual drought impact occurrence for different sectors and macro regions in Europe and combines information on past drought impacts, drought indices, and vulnerability factors into estimates of drought risk at the pan-European scale. This hybrid approach bridges the gap between traditional vulnerability assessment and probabilistic impact prediction in a statistical modelling framework. Multivariable logistic regression was applied to predict the likelihood of impact occurrence on an annual basis for particular impact categories and European macro regions. The results indicate sector- and macro-region-specific sensitivities of drought indices, with the Standardized Precipitation Evapotranspiration Index (SPEI) for a 12-month accumulation period as the overall best hazard predictor. Vulnerability factors have only limited ability to predict drought impacts as single predictors, with information about land use and water resources being the best vulnerability-based predictors. The application of the hybrid approach revealed strong regional and sector-specific differences in drought risk across Europe. The majority of the best predictor combinations rely on a combination of SPEI for shorter and longer accumulation periods, and a combination of information on land use and water resources. The added value of integrating regional vulnerability information with drought risk prediction

Genome-wide transcriptional reprogramming under drought stress

KAUST Repository

Chen, Hao

2012-01-01

Soil water deficit is one of the major factors limiting plant productivity. Plants cope with this adverse environmental condition by coordinating the up- or downregulation of an array of stress responsive genes. Reprogramming the expression of these genes leads to rebalanced development and growth that are in concert with the reduced water availability and that ultimately confer enhanced stress tolerance. Currently, several techniques have been employed to monitor genome-wide transcriptional reprogramming under drought stress. The results from these high throughput studies indicate that drought stress-induced transcriptional reprogramming is dynamic, has temporal and spatial specificity, and is coupled with the circadian clock and phytohormone signaling pathways. © 2012 Springer-Verlag Berlin Heidelberg. All rights are reserved.

Nitrogen Deifciency Limited the Improvement of Photosynthesis in Maize by Elevated CO2 Under Drought

Institute of Scientific and Technical Information of China (English)

ZONG Yu-zheng; SHANGGUAN Zhou-ping

2014-01-01

Global environmental change affects plant physiological and ecosystem processes. The interaction of elevated CO2, drought and nitrogen (N) deficiency result in complex responses of C4 species photosynthetic process that challenge our current understanding. An experiment of maize (Zea mays L.) involving CO2 concentrations (380 or 750 µmol mol-1, climate chamber), osmotic stresses (10% PEG-6000, -0.32 MPa) and nitrogen constraints (N deficiency treated since the 144th drought hour) was carried out to investigate its photosynthesis capacity and leaf nitrogen use efficiency. Elevated CO2 could alleviate drought-induced photosynthetic limitation through increasing capacity of PEPC carboxylation (Vpmax) and decreasing stomatal limitations (SL). The N deifciency exacerbated drought-induced photosynthesis limitations in ambient CO2. Elevated CO2 partially alleviated the limitation induced by drought and N deifciency through improving the capacity of Rubisco carboxylation (Vmax) and decreasing SL. Plants with N deifciency transported more N to their leaves at elevated CO2, leading to a high photosynthetic nitrogen-use efifciency but low whole-plant nitrogen-use efifciency. The stress mitigation by elevated CO2 under N deifciency conditions was not enough to improving plant N use efifciency and biomass accumulation. The study demonstrated that elevated CO2 could alleviate drought-induced photosynthesis limitation, but the alleviation varied with N supplies.

Tree-growth analyses to estimate tree species' drought tolerance.

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Eilmann, Britta; Rigling, Andreas

2012-02-01

Climate change is challenging forestry management and practices. Among other things, tree species with the ability to cope with more extreme climate conditions have to be identified. However, while environmental factors may severely limit tree growth or even cause tree death, assessing a tree species' potential for surviving future aggravated environmental conditions is rather demanding. The aim of this study was to find a tree-ring-based method suitable for identifying very drought-tolerant species, particularly potential substitute species for Scots pine (Pinus sylvestris L.) in Valais. In this inner-Alpine valley, Scots pine used to be the dominating species for dry forests, but today it suffers from high drought-induced mortality. We investigate the growth response of two native tree species, Scots pine and European larch (Larix decidua Mill.), and two non-native species, black pine (Pinus nigra Arnold) and Douglas fir (Pseudotsuga menziesii Mirb. var. menziesii), to drought. This involved analysing how the radial increment of these species responded to increasing water shortage (abandonment of irrigation) and to increasingly frequent drought years. Black pine and Douglas fir are able to cope with drought better than Scots pine and larch, as they show relatively high radial growth even after irrigation has been stopped and a plastic growth response to drought years. European larch does not seem to be able to cope with these dry conditions as it lacks the ability to recover from drought years. The analysis of trees' short-term response to extreme climate events seems to be the most promising and suitable method for detecting how tolerant a tree species is towards drought. However, combining all the methods used in this study provides a complete picture of how water shortage could limit species.

Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought

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Adams, Henry D.; Guardiola-Claramonte, Maite; Barron-Gafford, Greg A.; Villegas, Juan Camilo; Breshears, David D.; Zou, Chris B.; Troch, Peter A.; Huxman, Travis E.

2009-01-01

Large-scale biogeographical shifts in vegetation are predicted in response to the altered precipitation and temperature regimes associated with global climate change. Vegetation shifts have profound ecological impacts and are an important climate-ecosystem feedback through their alteration of carbon, water, and energy exchanges of the land surface. Of particular concern is the potential for warmer temperatures to compound the effects of increasingly severe droughts by triggering widespread vegetation shifts via woody plant mortality. The sensitivity of tree mortality to temperature is dependent on which of 2 non-mutually-exclusive mechanisms predominates—temperature-sensitive carbon starvation in response to a period of protracted water stress or temperature-insensitive sudden hydraulic failure under extreme water stress (cavitation). Here we show that experimentally induced warmer temperatures (≈4 °C) shortened the time to drought-induced mortality in Pinus edulis (piñon shortened pine) trees by nearly a third, with temperature-dependent differences in cumulative respiration costs implicating carbon starvation as the primary mechanism of mortality. Extrapolating this temperature effect to the historic frequency of water deficit in the southwestern United States predicts a 5-fold increase in the frequency of regional-scale tree die-off events for this species due to temperature alone. Projected increases in drought frequency due to changes in precipitation and increases in stress from biotic agents (e.g., bark beetles) would further exacerbate mortality. Our results demonstrate the mechanism by which warmer temperatures have exacerbated recent regional die-off events and background mortality rates. Because of pervasive projected increases in temperature, our results portend widespread increases in the extent and frequency of vegetation die-off. PMID:19365070

EFFECT OF DROUGHT STRESS INDUCED BY MANNITOL ON PHYSIOLOGICAL PARAMETERS OF MAIZE (ZEA MAYS L. SEEDLINGS AND PLANTS

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Katarzyna Możdżeń

2015-02-01

Full Text Available Plants are exposed to various stress factors which might lead to structural damage and physiological function abnormalities. Drought is one of the environmental stress factors that reduce the productivity of plants. The aim of our study was to determine the influence of drought stress induced by mannitol (-0.5 and -1.5MPa on selected physiological processes in Z. mays L. In the first stage we studied the effect of mannitol on the germination. In the second stage the effect of mannitol on the growth of plants germinated on distilled water and watered with mannitol in growth phase were measured. Mannitol, which decreased the water content in a concentration-dependent manner, had an inhibitory effect on germination and growth of seedlings and adult plants. Electrolyte leakage of cell membranes of the Z. mays seedlings showed high disturbances in the functioning of the membrane structures in the osmotic drought conditions. Similar results were obtained for maize roots, shoots and leaves in both treatment studies. Chlorophyll content showed only significant differences in plants from treated during the growth phase. Drought stress caused a decrease in chlorophyll content by almost a half compared to the control plants. Measurements of chlorophyll fluorescence of plant leaves from the second stage of experiments showed changes in fluorescence activity parameters Fv/Fm, NPQ, Rfd, qP, ect.; gas exchange measurements also showed changes in activity in each of the two phases.

Transcriptomic Analysis Reveals the Molecular Mechanisms of Drought-Stress-Induced Decreases in Camellia sinensis Leaf Quality

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Wang, Weidong; Xin, Huahong; Wang, Mingle; Ma, Qingping; Wang, Le; Kaleri, Najeeb A.; Wang, Yuhua; Li, Xinghui

2016-01-01

The tea plant [Camellia sinensis (L.) O. Kuntze] is an important commercial crop rich in bioactive ingredients, especially catechins, caffeine, theanine and other free amino acids, which the quality of tea leaves depends on. Drought is the most important environmental stress affecting the yield and quality of this plant. In this study, the effects of drought stress on the phenotype, physiological characteristics and major bioactive ingredients accumulation of C. sinensis leaves were examined, and the results indicated that drought stress resulted in dehydration and wilt of the leaves, and significant decrease in the total polyphenols and free amino acids and increase in the total flavonoids. In addition, HPLC analysis showed that the catechins, caffeine, theanine and some free amino acids in C. sinensis leaves were significantly reduced in response to drought stress, implying that drought stress severely decreased the quality of C. sinensis leaves. Furthermore, differentially expressed genes (DEGs) related to amino acid metabolism and secondary metabolism were identified and quantified in C. sinensis leaves under drought stress using high-throughput Illumina RNA-Seq technology, especially the key regulatory genes of the catechins, caffeine, and theanine biosynthesis pathways. The expression levels of key regulatory genes were consistent with the results from the HPLC analysis, which indicate a potential molecular mechanism for the above results. Taken together, these data provide further insights into the mechanisms underlying the change in the quality of C. sinensis leaves under environmental stress, which involve changes in the accumulation of major bioactive ingredients, especially catechins, caffeine, theanine and other free amino acids. PMID:27066035

Global drought and severe drought-affected populations in 1.5 and 2 °C warmer worlds

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Liu, Wenbin; Sun, Fubao; Lim, Wee Ho; Zhang, Jie; Wang, Hong; Shiogama, Hideo; Zhang, Yuqing

2018-03-01

The 2015 Paris Agreement proposed a more ambitious climate change mitigation target on limiting global warming to 1.5 °C instead of 2 °C above preindustrial levels. Scientific investigations on environmental risks associated with these warming targets are necessary to inform climate policymaking. Based on the Coupled Model Intercomparison Project phase 5 (CMIP5) climate models, we present the first risk-based assessment of changes in global drought and the impact of severe drought on populations from additional 1.5 and 2 °C warming conditions. Our results highlight the risk of drought on a global scale and in several hotspot regions such as the Amazon, northeastern Brazil, southern Africa and Central Europe at both 1.5 and 2 °C global warming relative to the historical period, showing increases in drought durations from 2.9 to 3.2 months. Correspondingly, more total and urban populations would be exposed to severe droughts globally (+132.5 ± 216.2 million and +194.5 ± 276.5 million total population and +350.2 ± 158.8 million and +410.7 ± 213.5 million urban populations in 1.5 and 2 °C warmer worlds) and regionally (e.g., East Africa, West Africa and South Asia). Less rural populations (-217.7 ± 79.2 million and -216.2 ± 82.4 million rural populations in 1.5 and 2 °C warmer worlds) would be exposed to severe drought globally under climate warming, population growth and especially the urbanization-induced population migration. By keeping global warming at 1.5 °C above the preindustrial levels instead of 2 °C, there is a decrease in drought risks (i.e., less drought duration, less drought intensity and severity but relatively more frequent drought) and the affected total, urban and rural populations would decrease globally and in most regions. While challenging for both East Africa and South Asia, the benefits of limiting warming to below 1.5 °C in terms of global drought risk and impact reduction are significant.

Drought, Endurance and Climate Change 'Pioneers': Lived Experience in the Production of Rural Environmental Knowledge

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Deb Anderson

2010-03-01

Full Text Available This article explores the politicisation of environmental knowledge on rural Australia, in an analysis of discourse on the lived experience of drought. It draws on research conducted in dryland farm communities in the Mallee wheat-belt of Victoria – where rural histories have presented spirited sagas of community perseverance in ‘battling’ a harsh climate – during a period of marked shift in public awareness of climate change (2004-07. Indeed climate change projections have intensified debate over rural futures in Australia, where droughts have played a powerful role in the mythologizing of rural battlers and landscapes, and where drought discourse has been dominated by the language of war. Cultural engagement with climate is, however, under constant renegotiation, as rural cultural research is apt to reveal.

Experimental evidence and modelling of drought induced alternative stable soil moisture states

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Robinson, David; Jones, Scott; Lebron, Inma; Reinsch, Sabine; Dominguez, Maria; Smith, Andrew; Marshal, Miles; Emmett, Bridget

2017-04-01

The theory of alternative stable states in ecosystems is well established in ecology; however, evidence from manipulation experiments supporting the theory is limited. Developing the evidence base is important because it has profound implications for ecosystem management. Here we show evidence of the existence of alternative stable soil moisture states induced by drought in an upland wet heath. We used a long-term (15 yrs) climate change manipulation experiment with moderate sustained drought, which reduced the ability of the soil to retain soil moisture by degrading the soil structure, reducing moisture retention. Moreover, natural intense droughts superimposed themselves on the experiment, causing an unexpected additional alternative soil moisture state to develop, both for the drought manipulation and control plots; this impaired the soil from rewetting in winter. Our results show the coexistence of three stable states. Using modelling with the Hydrus 1D software package we are able to show the circumstances under which shifts in soil moisture states are likely to occur. Given the new understanding it presents a challenge of how to incorporate feedbacks, particularly related to soil structure, into soil flow and transport models?

A novel gene of Kalanchoe daigremontiana confers plant drought resistance.

Science.gov (United States)

Wang, Li; Zhu, Chen; Jin, Lin; Xiao, Aihua; Duan, Jie; Ma, Luyi

2018-02-07

Kalanchoe (K.) daigremontiana is important for studying asexual reproduction under different environmental conditions. Here, we describe a novel KdNOVEL41 (KdN41) gene that may confer drought resistance and could thereby affect K. daigremontiana development. The detected subcellular localization of a KdN41/Yellow Fluorescent Protein (YFP) fusion protein was in the nucleus and cell membrane. Drought, salt, and heat stress treatment in tobacco plants containing the KdN41 gene promoter driving β-glucuronidase (GUS) gene transcription revealed that only drought stress triggered strong GUS staining in the vascular tissues. Overexpression (OE) of the KdN41 gene conferred improved drought resistance in tobacco plants compared to wild-type and transformed with empty vector plants by inducing higher antioxidant enzyme activities, decreasing cell membrane damage, increasing abscisic acid (ABA) content, causing reinforced drought resistance related gene expression profiles. The 3,3'-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) staining results also showed less relative oxygen species (ROS) content in KdN41-overexpressing tobacco leaf during drought stress. Surprisingly, by re-watering after drought stress, KdN41-overexpressing tobacco showed earlier flowering. Overall, the KdN41 gene plays roles in ROS scavenging and osmotic damage reduction to improve tobacco drought resistance, which may increase our understanding of the molecular network involved in developmental manipulation under drought stress in K. daigremontiana.

Modelling drought-induced dieback of Aleppo pine at the arid timberline

Science.gov (United States)

Wingate, Lisa; Preisler, Yakir; Bert, Didier; Rotenberg, Eyal; Yakir, Dan; Maseyk, Kadmiel; Ogee, Jerome

2016-04-01

During the mid 1960's an ambitious afforestation programme was initiated in the Negev desert of Israel. After five decades enduring harsh growing conditions, the Aleppo pine forest of Yatir is now exhibiting signs of 'drought-induced' dieback. Since 2010, 5-10% of the entire Yatir population have died, however the pattern of mortality is extremely patchy with some areas exhibiting >80% mortality whilst others display none. In this presentation, we reflect on historic climatic and edaphic conditions that have triggered this landscape mosaic of survival and mortality and how physiological and hydraulic traits vary within this patchwork. In addition, we explore how these pine trees have responded physiologically over recent years (1996-2010) to a series of severe drought events using a combined approach that brings together micrometeorological, dendro-isotopic and dendro-climatological datasets alongside process-based modelling. In particular the dataset trends were investigated with the isotope-enabled ecosystem model MuSICA to explore the consequences of subsequent droughts and embolism on modelled carbohydrate and water pool dynamics and their impact on carbon allocation and ecosystem function.

Involvement of dehydrins in 24-epibrassinolide-induced protection of wheat plants against drought stress.

Science.gov (United States)

Shakirova, Farida; Allagulova, Chulpan; Maslennikova, Dilara; Fedorova, Kristina; Yuldashev, Ruslan; Lubyanova, Alsu; Bezrukova, Marina; Avalbaev, Azamat

2016-11-01

In this study, we performed a comparative analysis of the physiological and biochemical parameters of wheat cultivars with contrasting drought resistance, drought-resistant Omskaya 35 (O-35) and less drought-resistant Salavat Yulaev (SYu), during 7-day germination under drought stress simulated by 5% mannitol. In addition, we evaluated the effectiveness of pre-sowing seed treatment with 0.4 μM 24-epibrassinolide (EBR) used to increase the resistance of plants of both cultivars to drought stress. It was revealed that mannitol has caused significant changes in the hormonal balance of the plants of both cultivars, associated with abscisic acid (ABA) accumulation and decrease in the contents of indoleacetic acid (IAA) and cytokinins (CKs). It should be noted that more dramatic changes in the content of phytohormones were characteristic for seedlings of SYu cultivar, which was reflected in a stronger growth inhibition of these plants. Pretreatment with EBR mitigated the negative effect of drought on the hormonal status and growth of seedlings during their germination. Furthermore, we found that drought caused accumulation of dehydrin (DHN) proteins, especially of low molecular weight DHNs, whose abundance was 2.5 times greater in O-35 cultivar than in SYu plants. EBR-pretreated plants of both cultivars were characterized by the additional accumulation of DHNs, indicating their involvement in the development of the EBR-induced wheat drought resistance. The use of fluridone allowed us to demonstrate ABA-dependent and ABA-independent pathways of regulation of low molecular mass dehydrins accumulation by EBR in wheat plants of both cultivars under drought conditions. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Hydraulic and carbohydrate changes in experimental drought-induced mortality of saplings in two conifer species.

Science.gov (United States)

Anderegg, William R L; Anderegg, Leander D L

2013-03-01

Global patterns of drought-induced forest die-off indicate that many forests may be sensitive to climate-driven mortality, but the lack of understanding of how trees and saplings die during drought hinders the projections of die-off, demographic bottlenecks and ecosystem trajectories. In this study, we performed a severe controlled drought experiment on saplings of Pinus edulis Engelm. and Juniperus osteosperma (Torr.) Little, two species that both experienced die-off in a recent 'climate change-type' drought. We examined the roles of carbohydrate and hydraulic changes in multiple tissues as the saplings died. We found that saplings of both species exhibited large degrees of loss of hydraulic conductivity prior to death. Neither species exhibited significant changes in carbohydrate concentrations in any tissue during the relatively short and severe imposed drought. Native hydraulic conductivity successfully predicted the degree of canopy mortality in both species, highlighting the importance of drought characteristics and tree attributes in influencing physiological pathways to mortality. The relationships elucidated here, as well as the differences between our results and previous findings in adult trees, can help inform mortality mechanisms in climate-vegetation models, especially for young trees, and to understand species response to severe drought across ontogeny.

Examining Severe Drought-Induced Vegetation Change and its Influence on Water Resources

Science.gov (United States)

White, A. B.; Springer, E. P.; Vivoni, E. R.

2007-12-01

A "global-change-type" drought that occurred in the southwestern U.S. from 2000 to 2003, accompanied by increased temperatures and bark beetle infestations, induced large-scale woodland overstory mortality, the consequent redistribution of water, radiation, and nutrients, as well as modification of the ecosystem phenology. Our objectives in this research are to examine these vegetation changes in detail and to determine whether they translated to changes in hydrological processes. We chose the Rio Ojo Caliente, a subbasin of the Rio Grande, as a study site since a significant portion of the woodland ecosystem (piñon-juniper) was affected. Examining a remotely-sensed vegetation index (1-km AVHRR NDVI from 1989 to 2006), there is an increasing trend in the mean NDVI from 1989 to 1998 (pre-drought period), a decreasing trend from 1999 to 2003 (drought period), and a dramatic increasing trend from 2004 to 2006 (post-drought period) in which the mean NDVI rebounds to pre- drought magnitudes. Streamflow records from 1932 to 2006 show the watershed to be primarily spring snowmelt-driven, although monsoonal summer precipitation also plays a significant role. We compare the temporal variability in the streamflow to the NDVI, including the mean, anomalies from the mean, and seasonally- based duration curves, and find significant correlations (correlation coefficient ρ = -0.61) between the streamflow and NDVI at approximately a three-month lag (NDVI lagging streamflow). In analyzing the three phases of the drought, the correlation is slightly stronger during the pre-drought (ρ = -0.64) and drought (ρ = -0.65) periods, yet markedly stronger during the post-drought period (ρ = -0.74). This suggests that the coupling between vegetation water use and streamflow is tighter after the drought. This may be attributable to the reduction in the less-responsive overstory (pinñon mortality) and increase in the more-responsive understory (grasses and shrubs exploiting newly

Trends and Tipping Points of Drought-induced Tree Mortality

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Huang, K.; Yi, C.; Wu, D.; Zhou, T.; Zhao, X.; Blanford, W. J.; Wei, S.; Wu, H.; Du, L.

2014-12-01

Drought-induced tree mortality worldwide has been recently reported in a review of the literature by Allen et al. (2010). However, a quantitative relationship between widespread loss of forest from mortality and drought is still a key knowledge gap. Specifically, the field lacks quantitative knowledge of tipping point in trees when coping with water stress, which inhibits the assessments of how climate change affects the forest ecosystem. We investigate the statistical relationships for different (seven) conifer species between Ring Width Index (RWI) and Standardized Precipitation Evapotranspiration Index (SPEI), based on 411 chronologies from the International Tree-Ring Data Bank across 11 states of the western United States. We found robust species-specific relationships between RWI and SPEI for all seven conifer species at dry condition. The regression models show that the RWI decreases with SPEI decreasing (drying) and more than 76% variation of tree growth (RWI) can be explained by the drought index (SPEI). However, when soil water is sufficient (i.e., SPEI>SPEIu), soil water is no longer a restrictive factor for tree growth and, therefore, the RWI shows a weak correlation with SPEI. Based on the statistical models, we derived the tipping point of SPEI (SPEItp) where the RWI equals 0, which means the carbon efflux by tree respiration equals carbon influx by tree photosynthesis. When the severity of drought exceeds this tipping point(i.e. SPEIsupported by the Fund for Creative Research Groups of National Natural Science Foundation of China (No. 41321001), the National Basic Research Program of China (No. 2012CB955401), the New Century Excellent Talents in University (No. NCET-10-0251), U.S. PSC-CUNY Award (PSC-CUNY-ENHC-44-83) and the High Technology Research and Development Program of China (No. 2013AA122801).

Environmental science: Trends in ecosystem recovery from drought

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Seneviratne, Sonia I.; Ciais, Philippe

2017-08-01

An analysis suggests that the time taken for ecosystems to recover from drought increased during the twentieth century. If the frequency of drought events rises, some ecosystems might never have the chance to fully recover. See Letter p.202

Drought is Coming: Monitoring Vegetation Response to Water Scarcity through Variable Chlorophyll a Fluorescence

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Guadagno, C. R.; Beverly, D.; Pleban, J. R.; Speckman, H. N.; Ewers, B. E.; Weinig, C.

2017-12-01

Aridity is one of the most pronounced environmental limits to plant survival, and understanding how plants respond to drought and recovery is crucial for predicting impacts on managed and natural ecosystems. Changes in soil moisture conditions induce a suite of physiological responses from the cell to ecosystem scale, complicating the assessment of drought effects. Characterizing early indicators of water scarcity across species can inform biophysical models with improved understanding of plant hydraulics. While indexes exist for drought monitoring across scales, many are unable to identify imminent vegetative drought. We explore a method of early diagnosis using leaf-level and kinetic imaging measures of variable chlorophyll a fluorescence. This is a fast and reliable tool capturing leaf physiological changes in advance of changes in NDVI or passive solar induced fluorescence. Both image and leaf level Pulse Amplitude Method (PAM) measurements illustrate the utility of variable chlorophyll a fluorescence for monitoring vegetative drought. Variable fluorescence was monitored across populations of crops, desert shrubs, montane conifers and riparian deciduous trees under variable water regimes. We found a strong correlation (R = 0.85) between the maximum efficiency of photosystem II measured using variable fluorescence (Fv'Fm') and leaf level electrolyte leakage, a proximal cause of drought stress induced by cellular damage in leaves. This association was confirmed in two gymnosperm species (Picea engelmannii and Pinus contorta) and for diverse varieties of the crop species Brassica rapa. The use of chlorophyll a fluorescence per image also allowed for early detection of drought in aspen (Populus tremuloides). These results provide evidence that variable chlorophyll fluorescence decreases between 25% and 70% in mild and severely droughted twigs with respect to ones collected from trees in wet soil conditions. While current systems for monitoring variable fluorescence

Blended Drought Index: Integrated Drought Hazard Assessment in the Cuvelai-Basin

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Robert Luetkemeier

2017-07-01

Full Text Available Drought is one of the major threats to societies in Sub-Saharan Africa, as the majority of the population highly depends on rain-fed subsistence agriculture and traditional water supply systems. Hot-spot areas of potential drought impact need to be identified to reduce risk and adapt a growing population to a changing environment. This paper presents the Blended Drought Index (BDI, an integrated tool for estimating the impact of drought as a climate-induced hazard in the semi-arid Cuvelai-Basin of Angola and Namibia. It incorporates meteorological and agricultural drought characteristics that impair the population’s ability to ensure food and water security. The BDI uses a copula function to combine common standardized drought indicators that describe precipitation, evapotranspiration, soil moisture and vegetation conditions. Satellite remote sensing products were processed to analyze drought frequency, severity and duration. As the primary result, an integrated drought hazard map was built to spatially depict drought hot-spots. Temporally, the BDI correlates well with millet/sorghum yield (r = 0.51 and local water consumption (r = −0.45 and outperforms conventional indicators. In the light of a drought’s multifaceted impact on society, the BDI is a simple and transferable tool to identify areas highly threatened by drought in an integrated manner.

Reduced Drought Tolerance by CRISPR/Cas9-Mediated SlMAPK3 Mutagenesis in Tomato Plants.

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Wang, Liu; Chen, Lin; Li, Rui; Zhao, Ruirui; Yang, Meijing; Sheng, Jiping; Shen, Lin

2017-10-04

Drought stress is one of the most destructive environmental factors that affect tomato plants adversely. Mitogen-activated protein kinases (MAPKs) are important signaling molecules that respond to drought stress. In this study, SlMAPK3 was induced by drought stress, and the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) system was utilized to generate slmapk3 mutants. Two independent T1 transgenic lines and wild-type (WT) tomato plants were used for analysis of drought tolerance. Compared with WT plants, slmapk3 mutants exhibited more severe wilting symptom, higher hydrogen peroxide content, lower antioxidant enzymes activities, and suffered more membrane damage under drought stress. Furthermore, knockout of SlMAPK3 led to up- or down-regulated expressions of drought stress-responsive genes including SlLOX, SlGST, and SlDREB. The results suggest that SlMAPK3 is involved in drought response in tomato plants by protecting cell membranes from oxidative damage and modulating transcription of stress-related genes.

Drought induced changes of leaf-to-root relationships in two tomato genotypes.

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Moles, Tommaso Michele; Mariotti, Lorenzo; De Pedro, Leandro Federico; Guglielminetti, Lorenzo; Picciarelli, Piero; Scartazza, Andrea

2018-07-01

Water deficit triggers a dynamic and integrated cross-talk between leaves and roots. Tolerant plants have developed several physiological and molecular mechanisms to establish new cell metabolism homeostasis, avoiding and/or escaping from permanent impairments triggered by drought. Two tomato genotypes (a Southern Italy landrace called Ciettaicale and the well-known commercial cultivar Moneymaker) were investigated at vegetative stage to assess leaf and root metabolic strategies under 20 days of water deficit. Physiological and metabolic changes, in terms of ABA, IAA, proline, soluble sugars and phenols contents, occurred in both tomato genotypes under water stress. Overall, our results pointed out the higher plasticity of Ciettaicale to manage plant water status under drought in order to preserve the source-sink relationships. This aim was achieved by maintaining a more efficient leaf photosystem II (PSII) photochemistry, as suggested by chlorophyll fluorescence parameters, associated with a major investment towards root growth and activity to improve water uptake. On the contrary, the higher accumulation of carbon compounds, resulting from reduced PSII photochemistry and enhanced starch reserve mobilization, in leaves and roots of Moneymaker under drought could play a key role in the osmotic adjustment, although causing a feedback disruption of the source-sink relations. This hypothesis was also supported by the different drought-induced redox unbalance, as suggested by H 2 O 2 and MDA contents. This could affect both PSII photochemistry and root activity, leading to a major involvement of NPQ and antioxidant system in response to drought in Moneymaker than Ciettaicale. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Positive feedback regulation of a Lycium chinense-derived VDE gene by drought-induced endogenous ABA, and over-expression of this VDE gene improve drought-induced photo-damage in Arabidopsis.

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Guan, Chunfeng; Ji, Jing; Zhang, Xuqiang; Li, Xiaozhou; Jin, Chao; Guan, Wenzhu; Wang, Gang

2015-03-01

Violaxanthin de-epoxidase (VDE) plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V) to intermediate product antheraxanthin (A) and final product zeaxanthin (Z) under light stress. We have cloned a VDE gene (LcVDE) from Lycium chinense, a deciduous woody perennial halophyte, which can grow in a large variety of soil types. The amino acid sequence of LcVDE has high homology with VDEs in other plants. Under drought stress, relative expression of LcVDE and the de-epoxidation ratio (Z+0.5A)/(V+A+Z) increased rapidly, and non-photochemical quenching (NPQ) also rose. Interestingly, these elevations induced by drought stress were reduced by the topical administration of abamine SG, a potent ABA inhibitor via inhibition of NCED in the ABA synthesis pathway. Until now, little has been done to explore the relationship between endogenous ABA and the expression of VDE genes. Since V serves as a common precursor for ABA, these data support the possible involvement of endogenous ABA in the positive feedback regulation of LcVDE gene expression in L. chinense under drought stress. Moreover, the LcVDE may be involved in modulating the level of photosynthesis damage caused by drought stress. Furthermore, the ratio of (Z+0.5A)/(V+A+Z) and NPQ increased more in transgenic Arabidopsis over-expressing LcVDE gene than the wild types under drought stress. The maximum quantum yield of primary photochemistry of PSII (Fv/Fm) in transgenic Arabidopsis decreased more slowly during the stressed period than that in wild types under the same conditions. Furthermore, transgenic Arabidopsis over-expressing LcVDE showed increased tolerance to drought stress. Copyright © 2014 Elsevier GmbH. All rights reserved.

Resilient Leaf Physiological Response of European Beech (Fagus sylvatica L. to Summer Drought and Drought Release

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Ellen E. Pflug

2018-02-01

Full Text Available Drought is a major environmental constraint to trees, causing severe stress and thus adversely affecting their functional integrity. European beech (Fagus sylvatica L. is a key species in mesic forests that is commonly expected to suffer in a future climate with more intense and frequent droughts. Here, we assessed the seasonal response of leaf physiological characteristics of beech saplings to drought and drought release to investigate their potential to recover from the imposed stress and overcome previous limitations. Saplings were transplanted to model ecosystems and exposed to a simulated summer drought. Pre-dawn water potentials (ψpd, stomatal conductance (gS, intercellular CO2 concentration (ci, net-photosynthesis (AN, PSII chlorophyll fluorescence (PItot, non-structural carbohydrate concentrations (NSC; soluble sugars, starch and carbon isotope signatures were measured in leaves throughout the growing season. Pre-dawn water potentials (ψpd, gS, ci, AN, and PItot decreased as drought progressed, and the concentration of soluble sugars increased at the expense of starch. Carbon isotopes in soluble sugars (δ13CS showed a distinct increase under drought, suggesting, together with decreased ci, stomatal limitation of AN. Drought effects on ψpd, ci, and NSC disappeared shortly after re-watering, while full recovery of gS, AN, and PItot was delayed by 1 week. The fast recovery of NSC was reflected by a rapid decay of the drought signal in δ13C values, indicating a rapid turnover of assimilates and a reactivation of carbon metabolism. After recovery, the previously drought-exposed saplings showed a stimulation of AN and a trend toward elevated starch concentrations, which counteracted the previous drought limitations. Overall, our results suggest that the internal water relations of beech saplings and the physiological activity of leaves are restored rapidly after drought release. In the case of AN, stimulation after drought may partially

Elucidation of complex nature of PEG induced drought-stress response in rice root using comparative proteomics approach

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Lalit Agrawal

2016-09-01

Full Text Available Along with many adaptive strategies, dynamic changes in protein abundance seem to be the common strategy to cope up with abiotic stresses which can be best explored through proteomics. Understanding of drought response is the key to decipher regulatory mechanism of better adaptation. Rice (Oryza sativa L. proteome represents a phenomenal source of proteins that govern traits of agronomic importance, such as drought tolerance. In this study, a comparison of root cytoplasmic proteome was done for a drought tolerant rice (Heena cultivar in PEG induced drought conditions. A total of 510 protein spots were observed by PDQuest analysis and 125 differentially regulated spots were subjected for MALDI-TOF MS-MS analysis out of which 102 protein spots identified which further led to identification of 78 proteins with a significant score. These 78 differentially expressed proteins appeared to be involved in different biological pathways. The largest percentage of identified proteins was involved in bioenergy and metabolism (29% and mainly consists of malate dehydrogenase, succinyl-CoA, putative acetyl-CoA synthetase and pyruvate dehydrogenase etc. This was followed by proteins related to cell defense and rescue (22% such as monodehydroascorbate reductase and stress-induced protein sti1, then by protein biogenesis and storage class (21% e.g. putative thiamine biosynthesis protein, putative beta-alanine synthase and cysteine synthase. Further, cell signaling (9% proteins like actin and prolyl endopeptidase and proteins with miscellaneous function (19% like Sgt1 and some hypothetical protein were also represented a large contribution towards drought regulatory mechanism in rice. We propose that protein biogenesis, cell defense and superior homeostasis may render better drought-adaptation. These findings might expedite the functional determination of the drought-responsive proteins and their prioritisation as potential molecular targets for perfect adaptation.

Arbuscular mycorrhizal symbiosis induces strigolactone biosynthesis under drought and improves drought tolerance in lettuce and tomato.

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Ruiz-Lozano, Juan Manuel; Aroca, Ricardo; Zamarreño, Ángel María; Molina, Sonia; Andreo-Jiménez, Beatriz; Porcel, Rosa; García-Mina, José María; Ruyter-Spira, Carolien; López-Ráez, Juan Antonio

2016-02-01

Arbuscular mycorrhizal (AM) symbiosis alleviates drought stress in plants. However, the intimate mechanisms involved, as well as its effect on the production of signalling molecules associated with the host plant-AM fungus interaction remains largely unknown. In the present work, the effects of drought on lettuce and tomato plant performance and hormone levels were investigated in non-AM and AM plants. Three different water regimes were applied, and their effects were analysed over time. AM plants showed an improved growth rate and efficiency of photosystem II than non-AM plants under drought from very early stages of plant colonization. The levels of the phytohormone abscisic acid, as well as the expression of the corresponding marker genes, were influenced by drought stress in non-AM and AM plants. The levels of strigolactones and the expression of corresponding marker genes were affected by both AM symbiosis and drought. The results suggest that AM symbiosis alleviates drought stress by altering the hormonal profiles and affecting plant physiology in the host plant. In addition, a correlation between AM root colonization, strigolactone levels and drought severity is shown, suggesting that under these unfavourable conditions, plants might increase strigolactone production in order to promote symbiosis establishment to cope with the stress. © 2015 John Wiley & Sons Ltd.

Post-Fire Seedling Recruitment and Morpho-Ecophysiological Responses to Induced Drought and Salvage Logging in Pinus halepensis Mill. Stands

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Daniel Moya

2015-05-01

Full Text Available Salvage logging is the commonest post-fire emergency action, but has unclear ecological effects. In the Mediterranean Basin, drought periods and fire regimes are changing and forest management should be adapted. In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine (Pinus halepensis Mill. forest in southeast Spain, which was submitted to salvage logging six months later. In spring 2010, plots were set in untreated and logged areas to monitor the recruitment and survival of the main tree species and three companion species: Stipa tenacissima L. (resprouter, Cistus clusii Dunal and Rosmarinus officinalis L. (obligate seeders. We evaluated responses to different scenarios in relation to intensification of summer droughts and forest management to obtain differences in water stress, growth, and gas exchange to cope with summer drought. Drought was induced by using rain-exclusion shelters and recorded ecophysiological characteristics were obtained with a portable gas exchange system. The main tree species recruitment was poor, but companion species showed a high survival ratio. Lower water stress was found for obligate seeder seedlings, which was higher in logged areas with induced drought. The initial post-fire stage was similar for the studied areas. However, after two drought periods (2010 and 2011, significant differences were found in the morphological and ecophysiological responses. In the unmanaged area, the biggest size of individuals due to the most marked increases in height and coverage were observed mainly in resprouter S. tenacissima. In the area submitted to salvage logging, the growth ratios in plots with induced drought were lower, mainly for seeders. Greater productivity was related to higher transpiration, stomatal conductance, and net photosynthetic ratio, but lower water use efficiency was found in obligate seeders with no drought induction, and S. tenacissima obtained higher values in untreated areas. Our results

An impact perspective on pan-European drought sensitivity

NARCIS (Netherlands)

Stahl, K.; Kohn, I.; Stefano, De L.; Tallaksen, L.M.; Rego, F.C.; Seneviratne, S.I.; Andreu, J.; Lanen, van H.A.J.

2015-01-01

In the past decades, Europe experienced several severe drought events with diverse environmental and socio-economic impacts. The EU FP-7 project DROUGHT R&SPI has investigated past drought impacts across different European countries and geoclimatic regions based on different approaches:

Elevated [CO2] does not ameliorate the negative effects of elevated temperature on drought-induced mortality in Eucalyptus radiata seedlings.

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Duan, Honglang; Duursma, Remko A; Huang, Guomin; Smith, Renee A; Choat, Brendan; O'Grady, Anthony P; Tissue, David T

2014-07-01

It has been reported that elevated temperature accelerates the time-to-mortality in plants exposed to prolonged drought, while elevated [CO(2)] acts as a mitigating factor because it can reduce stomatal conductance and thereby reduce water loss. We examined the interactive effects of elevated [CO(2)] and temperature on the inter-dependent carbon and hydraulic characteristics associated with drought-induced mortality in Eucalyptus radiata seedlings grown in two [CO(2)] (400 and 640 μL L(-1)) and two temperature (ambient and ambient +4 °C) treatments. Seedlings were exposed to two controlled drying and rewatering cycles, and then water was withheld until plants died. The extent of xylem cavitation was assessed as loss of stem hydraulic conductivity. Elevated temperature triggered more rapid mortality than ambient temperature through hydraulic failure, and was associated with larger water use, increased drought sensitivities of gas exchange traits and earlier occurrence of xylem cavitation. Elevated [CO(2)] had a negligible effect on seedling response to drought, and did not ameliorate the negative effects of elevated temperature on drought. Our findings suggest that elevated temperature and consequent higher vapour pressure deficit, but not elevated [CO(2)], may be the primary contributors to drought-induced seedling mortality under future climates. © 2013 John Wiley & Sons Ltd.

Comparative proteome analysis of drought-sensitive and drought-tolerant rapeseed roots and their hybrid F1 line under drought stress.

Science.gov (United States)

Mohammadi, Payam Pour; Moieni, Ahmad; Komatsu, Setsuko

2012-11-01

Rapeseed (Brassica napus L.), which is the third leading source of vegetable oil, is sensitive to drought stress during the early vegetative growth stage. To investigate the initial response of rapeseed to drought stress, changes in the protein expression profiles of drought-sensitive (RGS-003) and drought-tolerant lines (SLM-003), and their F1 hybrid, were analyzed using a proteomics approach. Seven-day-old rapeseed seedlings were treated with drought stress by restricting water for 7 days, and proteins were extracted from roots and separated by two-dimensional polyacrylamide gel electrophoresis. In the sensitive rapeseed line, 35 protein spots were differentially expressed under drought stress, and proteins related to metabolism, energy, disease/defense, and transport were decreased. In the tolerant line, 32 protein spots were differentially expressed under drought stress, and proteins involved in metabolism, disease/defense, and transport were increased, while energy-related proteins were decreased. Six protein spots in F1 hybrid were common among expressed proteins in the drought-sensitive and -tolerant lines. Notably, tubulin beta-2 and heat shock protein 70 were decreased in the drought-sensitive line and hybrid F1 plants, while jasmonate-inducible protein and 20S proteasome subunit PAF1 were increased in the F1 hybrids and drought-tolerant line. These results indicate that (1) V-type H(+) ATPase, plasma-membrane associated cation-binding protein, HSP 90, and elongation factor EF-2 have a role in the drought tolerance of rapeseed; (2) The decreased levels of heat shock protein 70 and tubulin beta-2 in the drought-sensitive and hybrid F1 lines might explain the reduced growth of these lines in drought conditions.

A hot future for European droughts

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Teuling, Adriaan J.

2018-05-01

Low soil moisture conditions can induce drought but also elevate temperatures. Detailed modelling of the drought-temperature link now shows that rising global temperature will bring drier soils and higher heatwave temperatures in Europe.

Drought coping strategies in cotton: increased crop per drop.

Science.gov (United States)

Ullah, Abid; Sun, Heng; Yang, Xiyan; Zhang, Xianlong

2017-03-01

The growth and yield of many crops, including cotton, are affected by water deficit. Cotton has evolved drought specific as well as general morpho-physiological, biochemical and molecular responses to drought stress, which are discussed in this review. The key physiological responses against drought stress in cotton, including stomata closing, root development, cellular adaptations, photosynthesis, abscisic acid (ABA) and jasmonic acid (JA) production and reactive oxygen species (ROS) scavenging, have been identified by researchers. Drought stress induces the expression of stress-related transcription factors and genes, such as ROS scavenging, ABA or mitogen-activated protein kinases (MAPK) signalling genes, which activate various drought-related pathways to induce tolerance in the plant. It is crucial to elucidate and induce drought-tolerant traits via quantitative trait loci (QTL) analysis, transgenic approaches and exogenous application of substances. The current review article highlights the natural as well as engineered drought tolerance strategies in cotton. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

Drought as a natural disaster

Energy Technology Data Exchange (ETDEWEB)

Maybank, J. [Agvironics Consulting, SK (Canada); Bonsal, B. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Geography; Jones, K. [Environment Canada, Downsview, ON (Canada). Canadian Climate Centre; Lawford, R. [Canadian Climate Centre, Saskatoon, SK (Canada). National Hydrology Research Centre; O`Brien, E.G. [Agriculture Canada, Ottawa, ON (Canada). Energy Analysis and Policy Div.; Ripley, E.A. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Soil Science; Wheaton, E. [Saskatchewan Research Council, Saskatoon, SK (Canada)

1995-12-31

A discussion of droughts as a major natural disaster in dry areas such as the Canadian Prairies where precipitation patterns are seasonal, was presented. Environmental damages include soil degradation and erosion, vegetation damage, slough and lake deterioration and wildlife loss. The development and application of specific soil moisture and drought indices based on cumulative precipitation deficits have enhanced drought monitoring programs. The identification of precursor conditions raises the possibility that the likelihood of a drought occurring in a particular year or growing season might be predictable. The ability to forecast seasonal temperature and precipitation anomalies is potentially feasible using a suitable merging of precursor parameters and modelling methodologies. Research activity to identify and evaluate new mitigative measure should be increased to keep pace with the prospects of drought predictability. 90 refs., 1 tab., 7 figs.

Stress inducible overexpression of AtHDG11 leads to improved drought and salt stress tolerance in peanut (Arachis hypogaea L.)

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Banavath, Jayanna N.; Chakradhar, Thammineni; Pandit, Varakumar; Konduru, Sravani; Guduru, Krishna K.; Akila, Chandra S.; Podha, Sudhakar; Puli, Chandra O. R.

2018-03-01

Peanut is an important oilseed and food legume cultivated as a rain-fed crop in semi-arid tropics. Drought and high salinity are the major abiotic stresses limiting the peanut productivity in this region. Development of drought and salt tolerant peanut varieties with improved yield potential using biotechnological approach is highly desirable to improve the peanut productivity in marginal geographies. As abiotic stress tolerance and yield represent complex traits, engineering of regulatory genes to produce abiotic stress-resilient transgenic crops appears to be a viable approach. In the present study, we developed transgenic peanut plants expressing an Arabidopsis homeodomain-leucine zipper transcription factor (AtHDG11) under stress inducible rd29Apromoter. A stress-inducible expression of AtHDG11 in three independent homozygous transgenic peanut lines resulted in improved drought and salt tolerance through up-regulation of known stress responsive genes(LEA, HSP70, Cu/Zn SOD, APX, P5CS, NCED1, RRS5, ERF1, NAC4, MIPS, Aquaporin, TIP, ELIP ) in the stress gene network , antioxidative enzymes, free proline along with improved water use efficiency traits such as longer root system, reduced stomatal density, higher chlorophyll content, increased specific leaf area, improved photosynthetic rates and increased intrinsic instantaneous WUE. Transgenic peanut plants displayed high yield compared to non-transgenic plants under both drought and salt stress conditions. Holistically, our study demonstrates the potentiality of stress-induced expression of AtHDG11 to improve the drought, salt tolerance in peanut.

Global drought and severe drought-affected populations in 1.5 and 2 °C warmer worlds

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W. Liu

2018-03-01

Full Text Available The 2015 Paris Agreement proposed a more ambitious climate change mitigation target on limiting global warming to 1.5 °C instead of 2 °C above preindustrial levels. Scientific investigations on environmental risks associated with these warming targets are necessary to inform climate policymaking. Based on the Coupled Model Intercomparison Project phase 5 (CMIP5 climate models, we present the first risk-based assessment of changes in global drought and the impact of severe drought on populations from additional 1.5 and 2 °C warming conditions. Our results highlight the risk of drought on a global scale and in several hotspot regions such as the Amazon, northeastern Brazil, southern Africa and Central Europe at both 1.5 and 2 °C global warming relative to the historical period, showing increases in drought durations from 2.9 to 3.2 months. Correspondingly, more total and urban populations would be exposed to severe droughts globally (+132.5 ± 216.2 million and +194.5 ± 276.5 million total population and +350.2 ± 158.8 million and +410.7 ± 213.5 million urban populations in 1.5 and 2 °C warmer worlds and regionally (e.g., East Africa, West Africa and South Asia. Less rural populations (−217.7 ± 79.2 million and −216.2 ± 82.4 million rural populations in 1.5 and 2 °C warmer worlds would be exposed to severe drought globally under climate warming, population growth and especially the urbanization-induced population migration. By keeping global warming at 1.5 °C above the preindustrial levels instead of 2 °C, there is a decrease in drought risks (i.e., less drought duration, less drought intensity and severity but relatively more frequent drought and the affected total, urban and rural populations would decrease globally and in most regions. While challenging for both East Africa and South Asia, the benefits of limiting warming to below 1.5 °C in terms of global drought risk

Groundwater potential for water supply during droughts in Korea

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Hyun, Y.; Cha, E.; Moon, H. J.

2016-12-01

Droughts have been receiving much attention in Korea because severe droughts occurred in recent years, causing significant social, economic and environmental damages in some regions. Residents in agricultural area, most of all, were most damaged by droughts with lack of available water supplies to meet crop water demands. In order to mitigate drought damages, we present a strategy to keep from agricultural droughts by using groundwater to meet water supply as a potential water resource in agricultural areas. In this study, we analyze drought severity and the groundwater potential to mitigate social and environmental damages caused by droughts in Korea. We evaluate drought severity by analyzing spatial and temporal meteorological and hydrological data such as rainfall, water supply and demand. For drought severity, we use effective drought index along with the standardized precipitation index (SPI) and standardized runoff index(SRI). Water deficit during the drought period is also quantified to consider social and environmental impact of droughts. Then we assess the feasibility of using groundwater as a potential source for groundwater impact mitigation. Results show that the agricultural areas are more vulnerable to droughts and use of groundwater as an emergency water resource is feasible in some regions. For a case study, we select Jeong-Sun area located in Kangwon providence having well-developed Karst aquifers and surrounded by mountains. For Jeong-Sun area, we quantify groundwater potential use, design the method of water supply by using groundwater, and assess its economic benefit. Results show that water supply system with groundwater abstraction can be a good strategy when droughts are severe for an emergency water supply in Jeong-Sun area, and groundwater can also be used not only for a dry season water supply resource, but for everyday water supply system. This case study results can further be applicable to some regions with no sufficient water

Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change?

Science.gov (United States)

Savi, Tadeja; Bertuzzi, Stefano; Branca, Salvatore; Tretiach, Mauro; Nardini, Andrea

2015-02-01

Urban trees help towns to cope with climate warming by cooling both air and surfaces. The challenges imposed by the urban environment, with special reference to low water availability due to the presence of extensive pavements, result in high rates of mortality of street trees, that can be increased by climatic extremes. We investigated the water relations and xylem hydraulic safety/efficiency of Quercus ilex trees growing at urban sites with different percentages of surrounding impervious pavements. Seasonal changes of plant water potential and gas exchange, vulnerability to cavitation and embolism level, and morpho-anatomical traits were measured. We found patterns of increasing water stress and vulnerability to drought at increasing percentages of impervious pavement cover, with a consequent reduction in gas exchange rates, decreased safety margins toward embolism development, and increased vulnerability to cavitation, suggesting the occurrence of stress-induced hydraulic deterioration. The amount of impermeable surface and chronic exposure to water stress influence the site-specific risk of drought-induced dieback of urban trees under extreme drought. Besides providing directions for management of green spaces in towns, our data suggest that xylem hydraulics is key to a full understanding of the responses of urban trees to global change. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Experimental drought induces short-term changes in soil functionality and microbial community structure after fire in a Mediterranean shrubland

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Hinojosa, M. B.; Parra, A.; Laudicina, V. A.; Moreno, J. M.

2014-10-01

Fire is a major ecosystem driver, causing significant changes in soil nutrients and microbial community structure and functionality. Post-fire soil dynamics can vary depending on rainfall patterns, although variations in response to drought are poorly known. This is particularly important in areas with poor soils and limited rainfall, like arid and semiarid ones. Furthermore, climate change projections in many such areas anticipate reduced precipitation and longer drought, together with an increase in fire severity. The effects of experimental drought and fire were studied on soils in a Mediterranean Cistus-Erica shrubland in Central Spain. A replicated (n = 4) field experiment was carried out in which four levels of rainfall pattern were implemented by means of a rain-out shelters and irrigation system. The treatments were: environmental control (natural rainfall), historical control (long-term average rainfall, 2 months drought), moderate drought (25% reduction of historical control, 5 months drought) and severe drought (45% reduction, 7 months drought). After one growing season, the plots were burned with high fire intensity, except a set of unburned plots that served as control. Soils were collected seasonally during one year and variables related to soil nutrient availability and microbial community structure and functionality were studied. Burned soils increased nutrient availability (P, N, K) with respect to unburned ones, but drought reduced such an increase in P, while it further increased N and K. Such changes in available soil nutrients were short-lived. Drought caused a further decrease of enzyme activities, carbon mineralization rate and microbial biomass. Fire decreased the relative abundance of fungi and actinomycetes. However, fire and drought caused a further reduction in fungi, with bacteria becoming relatively more abundant. Arguably, increasing drought and fires due to climate change will likely shift soil recovery after fire.

Overexpression of an ABA biosynthesis gene using a stress inducible promoter enhances drought resistance in petunia

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Plants respond to drought stress by closing their stomata and reducing transpirational water loss. The plant hormone abscisic acid (ABA) regulates growth and stomatal closure particularly when the plant is under environmental stresses. One of the key enzymes in the ABA biosynthesis of higher plants ...

Noninvasive Measurement of Vulnerability to Drought-Induced Embolism by X-Ray Microtomography.

Science.gov (United States)

Choat, Brendan; Badel, Eric; Burlett, Regis; Delzon, Sylvain; Cochard, Herve; Jansen, Steven

2016-01-01

Hydraulic failure induced by xylem embolism is one of the primary mechanisms of plant dieback during drought. However, many of the methods used to evaluate the vulnerability of different species to drought-induced embolism are indirect and invasive, increasing the possibility that measurement artifacts may occur. Here, we utilize x-ray computed microtomography (microCT) to directly visualize embolism formation in the xylem of living, intact plants with contrasting wood anatomy (Quercus robur, Populus tremula × Populus alba, and Pinus pinaster). These observations were compared with widely used centrifuge techniques that require destructive sampling. MicroCT imaging provided detailed spatial information regarding the dimensions and functional status of xylem conduits during dehydration. Vulnerability curves based on microCT observations of intact plants closely matched curves based on the centrifuge technique for species with short vessels (P. tremula × P. alba) or tracheids (P. pinaster). For ring porous Q. robur, the centrifuge technique significantly overestimated vulnerability to embolism, indicating that caution should be used when applying this technique to species with long vessels. These findings confirm that microCT can be used to assess the vulnerability to embolism on intact plants by direct visualization. © 2016 American Society of Plant Biologists. All Rights Reserved.

Groundwater quality surrounding Lake Texoma during short-term drought conditions

International Nuclear Information System (INIS)

Kampbell, Donald H.; An, Youn-Joo; Jewell, Ken P.; Masoner, Jason R.

2003-01-01

Stressors such as nitrates and total salts in ground water could potentially become a health or environmental problem during drought conditions. - Water quality data from 55 monitoring wells during drought conditions surrounding Lake Texoma, located on the border of Oklahoma and Texas, was compared to assess the influence of drought on groundwater quality. During the drought month of October, water table levels were three feet (0.9 m) lower compared with several months earlier under predrought climate conditions. Detection frequencies of nitrate (> 0.1 mg/l), orthophosphates (> 0.1 mg/l), chlorides (> MCL), and sulfates (> MCL) all increased during drought. Orthophosphate level was higher during drought. Largest increases in concentration were nitrate under both agriculture lands and in septic tank areas. An increase in ammonium-nitrogen was only detected in the septic tank area. The study showed that stressors such as nitrate and total salts could potentially become a health or environmental problem during drought

A new multi-sensor integrated index for drought monitoring

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Jiao, W.; Wang, L.; Tian, C.

2017-12-01

Drought is perceived as one of the most expensive and least understood natural disasters. The remote-sensing-based integrated drought indices, which integrate multiple variables, could reflect the drought conditions more comprehensively than single drought indices. However, most of current remote-sensing-based integrated drought indices focus on agricultural drought (i.e., deficit in soil moisture), their application in monitoring meteorological drought (i.e., deficit in precipitation) was limited. More importantly, most of the remote-sensing-based integrated drought indices did not take into consideration of the spatially non-stationary nature of the related variables, so such indices may lose essential local details when integrating multiple variables. In this regard, we proposed a new mathematical framework for generating integrated drought index for meteorological drought monitoring. The geographically weighted regression (GWR) model and principal component analysis were used to composite Moderate-resolution Imaging Spectroradiometer (MODIS) based temperature condition index (TCI), the Vegetation Index based on the Universal Pattern Decomposition method (VIUPD) based vegetation condition index (VCI), tropical rainfall measuring mission (TRMM) based Precipitation Condition Index (PCI) and Advanced Microwave Scanning Radiometer-EOS (AMSR-E) based soil moisture condition index (SMCI). We called the new remote-sensing-based integrated drought index geographical-location-based integrated drought index (GLIDI). We examined the utility of the GLIDI for drought monitoring in various climate divisions across the continental United States (CONUS). GLIDI showed high correlations with in-situ drought indices and outperformed most other existing drought indices. The results also indicate that the performance of GLIDI is not affected by environmental factors such as land cover, precipitation, temperature and soil conditions. As such, the GLIDI has considerable potential for

Synergistic effects of drought stress and photoperiods on phenology and secondary metabolism of Silybum marianum.

Science.gov (United States)

Zahir, Adnan; Abbasi, Bilal Haider; Adil, Muhammad; Anjum, Sumaira; Zia, Muhammad; Ihsan-Ul-Haq

2014-09-01

Silybum marianum is an important medicinal plant of the family Asteraceae, well known for its set of bioactive isomeric mixture of secondary metabolites "silymarin", primarily acting as a hepato-protective agent. Abiotic stress augments plant secondary metabolism in different plant tissues to withstand harsh environmental fluctuations. In the current study, our aim was to induce drought stress in vitro on S. marianum under the influence of different photoperiod treatments to study the effects, with respect to variations in secondary metabolic profile and plant growth and development. S. marianum was extremely vulnerable to different levels of mannitol-induced drought stress. Water deficiency inhibited root induction completely and retarded plant growth was observed; however, phytochemical analysis revealed enhanced accumulation of total phenolic content (TPC), total flavonoid content (TFC), and total protein content along with several antioxidative enzymes. Secondary metabolic content was positively regulated with increasing degree of drought stress. A dependent correlation of seed germination frequency at mild drought stress and antioxidative activities was established with 2 weeks dark + 2 weeks 16/8 h photoperiod treatment, respectively, whereas a positive correlation existed for TPC and TFC when 4 weeks 16/8 h photoperiod treatment was applied. The effects of drought stress are discussed in relation to phenology, seed germination frequency, biomass build up, antioxidative potential, and secondary metabolites accumulation.

Potato Annexin STANN1 Promotes Drought Tolerance and Mitigates Light Stress in Transgenic Solanum tuberosum L. Plants

Science.gov (United States)

Szalonek, Michal; Sierpien, Barbara; Rymaszewski, Wojciech; Gieczewska, Katarzyna; Garstka, Maciej; Lichocka, Malgorzata; Sass, Laszlo; Paul, Kenny; Vass, Imre; Vankova, Radomira; Dobrev, Peter; Szczesny, Pawel; Marczewski, Waldemar; Krusiewicz, Dominika; Strzelczyk-Zyta, Danuta; Hennig, Jacek; Konopka-Postupolska, Dorota

2015-01-01

Annexins are a family of calcium- and membrane-binding proteins that are important for plant tolerance to adverse environmental conditions. Annexins function to counteract oxidative stress, maintain cell redox homeostasis, and enhance drought tolerance. In the present study, an endogenous annexin, STANN1, was overexpressed to determine whether crop yields could be improved in potato (Solanum tuberosum L.) during drought. Nine potential potato annexins were identified and their expression characterized in response to drought treatment. STANN1 mRNA was constitutively expressed at a high level and drought treatment strongly increased transcription levels. Therefore, STANN1 was selected for overexpression analysis. Under drought conditions, transgenic potato plants ectopically expressing STANN1 were more tolerant to water deficit in the root zone, preserved more water in green tissues, maintained chloroplast functions, and had higher accumulation of chlorophyll b and xanthophylls (especially zeaxanthin) than wild type (WT). Drought-induced reductions in the maximum efficiency and the electron transport rate of photosystem II (PSII), as well as the quantum yield of photosynthesis, were less pronounced in transgenic plants overexpressing STANN1 than in the WT. This conferred more efficient non-photochemical energy dissipation in the outer antennae of PSII and probably more efficient protection of reaction centers against photooxidative damage in transgenic plants under drought conditions. Consequently, these plants were able to maintain effective photosynthesis during drought, which resulted in greater productivity than WT plants despite water scarcity. Although the mechanisms underlying this stress protection are not yet clear, annexin-mediated photoprotection is probably linked to protection against light-induced oxidative stress. PMID:26172952

Potato Annexin STANN1 Promotes Drought Tolerance and Mitigates Light Stress in Transgenic Solanum tuberosum L. Plants.

Science.gov (United States)

Szalonek, Michal; Sierpien, Barbara; Rymaszewski, Wojciech; Gieczewska, Katarzyna; Garstka, Maciej; Lichocka, Malgorzata; Sass, Laszlo; Paul, Kenny; Vass, Imre; Vankova, Radomira; Dobrev, Peter; Szczesny, Pawel; Marczewski, Waldemar; Krusiewicz, Dominika; Strzelczyk-Zyta, Danuta; Hennig, Jacek; Konopka-Postupolska, Dorota

2015-01-01

Annexins are a family of calcium- and membrane-binding proteins that are important for plant tolerance to adverse environmental conditions. Annexins function to counteract oxidative stress, maintain cell redox homeostasis, and enhance drought tolerance. In the present study, an endogenous annexin, STANN1, was overexpressed to determine whether crop yields could be improved in potato (Solanum tuberosum L.) during drought. Nine potential potato annexins were identified and their expression characterized in response to drought treatment. STANN1 mRNA was constitutively expressed at a high level and drought treatment strongly increased transcription levels. Therefore, STANN1 was selected for overexpression analysis. Under drought conditions, transgenic potato plants ectopically expressing STANN1 were more tolerant to water deficit in the root zone, preserved more water in green tissues, maintained chloroplast functions, and had higher accumulation of chlorophyll b and xanthophylls (especially zeaxanthin) than wild type (WT). Drought-induced reductions in the maximum efficiency and the electron transport rate of photosystem II (PSII), as well as the quantum yield of photosynthesis, were less pronounced in transgenic plants overexpressing STANN1 than in the WT. This conferred more efficient non-photochemical energy dissipation in the outer antennae of PSII and probably more efficient protection of reaction centers against photooxidative damage in transgenic plants under drought conditions. Consequently, these plants were able to maintain effective photosynthesis during drought, which resulted in greater productivity than WT plants despite water scarcity. Although the mechanisms underlying this stress protection are not yet clear, annexin-mediated photoprotection is probably linked to protection against light-induced oxidative stress.

Potato Annexin STANN1 Promotes Drought Tolerance and Mitigates Light Stress in Transgenic Solanum tuberosum L. Plants.

Directory of Open Access Journals (Sweden)

Michal Szalonek

Full Text Available Annexins are a family of calcium- and membrane-binding proteins that are important for plant tolerance to adverse environmental conditions. Annexins function to counteract oxidative stress, maintain cell redox homeostasis, and enhance drought tolerance. In the present study, an endogenous annexin, STANN1, was overexpressed to determine whether crop yields could be improved in potato (Solanum tuberosum L. during drought. Nine potential potato annexins were identified and their expression characterized in response to drought treatment. STANN1 mRNA was constitutively expressed at a high level and drought treatment strongly increased transcription levels. Therefore, STANN1 was selected for overexpression analysis. Under drought conditions, transgenic potato plants ectopically expressing STANN1 were more tolerant to water deficit in the root zone, preserved more water in green tissues, maintained chloroplast functions, and had higher accumulation of chlorophyll b and xanthophylls (especially zeaxanthin than wild type (WT. Drought-induced reductions in the maximum efficiency and the electron transport rate of photosystem II (PSII, as well as the quantum yield of photosynthesis, were less pronounced in transgenic plants overexpressing STANN1 than in the WT. This conferred more efficient non-photochemical energy dissipation in the outer antennae of PSII and probably more efficient protection of reaction centers against photooxidative damage in transgenic plants under drought conditions. Consequently, these plants were able to maintain effective photosynthesis during drought, which resulted in greater productivity than WT plants despite water scarcity. Although the mechanisms underlying this stress protection are not yet clear, annexin-mediated photoprotection is probably linked to protection against light-induced oxidative stress.

Futuragua: Fostering Cross-Scale Knowledge to Inform Social-Environmental Decision Processes for Building Drought Resilience in Highly Seasonal Environments

Science.gov (United States)

McDaniels, T.; Steyn, D. G.; Johnson, M. S.; Small, M.; Leclerc, G.; Vignola, R.; Chan, K.; Grossmann, I.; Wong-Parodi, G.

2014-12-01

Improving resilience to drought in complex social-environmental systems (SES) is extraordinarily important, particularly for rural tropical locations where small changes in climate regimes can have dramatic SES impacts. Efforts to build drought resilience must necessarily be planned and implemented within SES governance systems that involve linkages in water and land use administration from local to national levels. These efforts require knowledge and understanding that links climate and weather forecasts to regional and local hydrology, to social-economic and environmental systems, and to governance processes. In order to provide structure for such complex choices and investments, we argue that a focus on structured decision processes that involve linkages among science, technological perspectives, and public values conducted with agencies and stakeholders will provide a crucial framework for comparing and building insight for pursuing alternative courses of action to build drought resilience. This paper focuses on a regional case study in the seasonally-dry northwest region of Costa Rica, in watersheds rated as most threatened in the country in terms of drought. We present the overall framework guiding the transdisciplinary efforts to link scientific and technical understanding to public values, in order to foster civil society actions that lead to improved drought resilience. Initial efforts to characterize hydrological and climate regimes will be reported along with our approach to linking natural science findings, social inventories in terms of perspectives on SES, and the psychology and patterns of reliance on forecast information that provide the basis for characterizing public understanding. The overall linkage of technical and value information is focused on creating and comparing alternative actions that can potentially build resilience in short and long time frames by building decision making processes involving stakeholders, agencies and interested

Modeling drought impact occurrence based on climatological drought indices for four European countries

Science.gov (United States)

Stagge, James H.; Kohn, Irene; Tallaksen, Lena M.; Stahl, Kerstin

2014-05-01

The relationship between atmospheric conditions and the likelihood of a significant drought impact has, in the past, been difficult to quantify, particularly in Europe where political boundaries and language have made acquiring comprehensive drought impact information difficult. As such, the majority of studies linking meteorological drought with the occurrence or severity of drought impacts have previously focused on specific regions, very detailed impact types, or both. This study describes a new methodology to link the likelihood of drought impact occurrence with climatological drought indices across different European climatic regions and impact sectors using the newly developed European Drought Impact report Inventory (EDII), a collaborative database of drought impact information (www.geo.uio.no/edc/droughtdb/). The Standardized Precipitation Index (SPI) and Standardized Precipitation-Evapotranspiration Index (SPEI) are used as predictor variables to quantify meteorological drought severity over prior time periods (here 1, 2, 3, 6, 9, 12, and 24 months are used). The indices are derived using the gridded WATCH Forcing Datasets, covering the period 1958-2012. Analysis was performed using logistic regression to identify the climatological drought index and accumulation period, or linear combination of drought indices, that best predicts the likelihood of a documented drought impact, defined by monthly presence/absence. The analysis was carried out for a subset of four European countries (Germany, UK, Norway, Slovenia) and four of the best documented impact sectors: Public Water Supply, Agriculture and Livestock Farming, Energy and Industry, and Environmental Quality. Preliminary results show that drought impacts in these countries occur most frequently due to a combination of short-term (2-6 month) precipitation deficits and long-term (12-24 month) potential evapotranspiration anomaly, likely associated with increased temperatures. Agricultural drought impacts

Low Temperature-Induced 30 (LTI30 positively regulates drought stress resistance in Arabidopsis: effect on abscisic acid sensitivity and hydrogen peroxide accumulation

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Haitao eShi

2015-10-01

Full Text Available As a dehydrin belonging to group II late embryogenesis abundant protein (LEA family, Arabidopsis Low Temperature-Induced 30 (LTI30/XERO2 has been shown to be involved in plant freezing stress resistance. However, the other roles of AtLTI30 remain unknown. In this study, we found that the expression of AtLTI30 was largely induced by drought stress and abscisic acid (ABA treatments. Thereafter, AtLTI30 knockout mutants and overexpressing plants were isolated to investigate the possible involvement of AtLTI30 in ABA and drought stress responses. AtLTI30 knockout mutants were less sensitive to ABA-mediated seed germination, while AtLTI30 overexpressing plants were more sensitive to ABA compared with wild type (WT. Consistently, the AtLTI30 knockout mutants displayed decreased drought stress resistance, while the AtLTI30 overexpressing plants showed improved drought stress resistance compared with WT, as evidenced by a higher survival rate and lower leaf water loss than WT after drought stress. Moreover, manipulation of AtLTI30 expression positively regulated the activities of catalases (CATs and endogenous proline content, as a result, negatively regulated drought stress-triggered hydrogen peroxide (H2O2 accumulation. All these results indicate that AtLTI30 is a positive regulator of plant drought stress resistance, partially through the modulation of ABA sensitivity, H2O2 and proline accumulation.

Fire-induced deforestation in drought-prone Mediterranean forests : drivers and unknowns from leaves to communities

NARCIS (Netherlands)

Karavani, Asaf; Boer, Matthias M.; Baudena, Mara|info:eu-repo/dai/nl/340303867; Colinas, Carlos; Díaz-Sierra, Rubén; Pemán, Jesús; de Luis, Martín; Enríquez-de-Salamanca, Álvaro; Resco de Dios, Víctor

Over the past 15 years, 3 million hectares of forests have been converted into shrublands or grasslands in the Mediterranean countries of the European Union. Fire and drought are the main drivers underlying this deforestation. Here we present a conceptual framework for the process of fire-induced

The U.S./Canadian GEO Bilateral Drought Indices and Definitions Study: Implications for the Canadian Drought Monitor and a Global Drought Early Warning System

Science.gov (United States)

Hadwen, T.; Heim, R. R.; Howard, A.

2011-12-01

Drought is a difficult phenomenon to define; the way in which it is monitored, measured, assessed and even the very definition of drought vary from location to location based on the regional climate and the potential impacts. Drought is not an absolute condition but an evolving state brought on by relatively dry weather, growing more severe over time. There are many factors that define a drought and many more that define its impacts. Many definitions and indices are based solely on meteorological characteristics. Although this approach has merit, it is often necessary to go further to define those meteorological conditions in a way that is relevant to the land and water use in a region. A Drought Indices and Definitions Study was initiated in 2010 as part of a GEO Bilateral effort to examine drought across the U.S. and Canada. The Study's deliverables will include a survey of the drought indices used to monitor drought, and a bibliography of research addressing the nature of drought, across the diverse climates of the continent. With an increasing pressure to utilize drought monitoring as a primary indicator of need for disaster assistance, the reliability of drought indices must be validated and utilized in appropriate in various regions. In 2009, following over five years of participation in the North American Drought Monitor (NA-DM), the National Agroclimate Information Service of Agriculture and Agri-Food Canada initiated a project to develop a Canadian Drought Monitor (Can-DM), based on primary principles used in the NA-DM and the US Drought Monitor (US-DM). The process of developing an operational monitoring tool and using drought indices in a vast and environmentally diverse country has been challenging. in Canada, many of the commonly used indices are not appropriate in certain regions or data densities do not allow for proper use. This paper will discuss the experiences that the Can-DM team has had dealing with these challenges, how these experiences

Income breeding allows an aquatic snake Seminatrix pygaea to reproduce normally following prolonged drought-induced aestivation.

Science.gov (United States)

Winne, Christopher T; Willson, John D; Gibbons, J Whitfield

2006-11-01

1. Capital breeding is an ideal reproductive strategy for many ectotherms because it provides a disassociation between feeding and reproduction, a necessary requirement for animals that become anorexic during pregnancy. Among ectotherms, some viviparous snakes (e.g. Viperidae) exemplify the capital breeding strategy because many species (i) do not feed during pregnancy due to behavioural conflicts between reproduction and foraging, and (ii) take more than one season to accumulate sufficient energetic stores for reproduction. 2. Isolated wetlands often exhibit extreme annual fluctuations in environmental conditions with prolonged droughts periodically leaving wetlands completely dry and devoid of prey. Following droughts, however, wetlands can be extremely productive, rendering prey resources virtually unlimited for some species. 3. This study examines drought survival strategy and reproductive ecology of a small aquatic snake Seminatrix pygaea (Cope) in an isolated wetland. Seminatrix pygaea are atypical from most sympatric snake species in that (i) their small body size, reliance on aquatic prey, and high rates of evaporative water loss make them ill-suited to overland movement, and (ii) they may not be subject to costs typically associated with feeding during pregnancy. 4. We hypothesized that S. pygaea would survive periodic multiyear droughts by aestivating within the dried wetland, a survival strategy heretofore undocumented in snakes. Further, we hypothesized that if S. pygaea rely on 'typical' snake reproductive strategies of 'adaptive anorexia' and capital breeding, reproductive output would be reduced in the first wet year following drought. 5. By encircling a 10-ha wetland with a continuous drift fence before it refilled we were able to demonstrate that S. pygaea were present within the dried wetland prior to the onset of spring rains that refilled the wetland in 2003. Our results suggest that S. pygaea are capable of surviving multiyear droughts by

Estimating drought risk across Europe from reported drought impacts, hazard indicators and vulnerability factors

Science.gov (United States)

Blauhut, V.; Stahl, K.; Stagge, J. H.; Tallaksen, L. M.; De Stefano, L.; Vogt, J.

2015-12-01

Drought is one of the most costly natural hazards in Europe. Due to its complexity, drought risk, the combination of the natural hazard and societal vulnerability, is difficult to define and challenging to detect and predict, as the impacts of drought are very diverse, covering the breadth of socioeconomic and environmental systems. Pan-European maps of drought risk could inform the elaboration of guidelines and policies to address its documented severity and impact across borders. This work (1) tests the capability of commonly applied hazard indicators and vulnerability factors to predict annual drought impact occurrence for different sectors and macro regions in Europe and (2) combines information on past drought impacts, drought hazard indicators, and vulnerability factors into estimates of drought risk at the pan-European scale. This "hybrid approach" bridges the gap between traditional vulnerability assessment and probabilistic impact forecast in a statistical modelling framework. Multivariable logistic regression was applied to predict the likelihood of impact occurrence on an annual basis for particular impact categories and European macro regions. The results indicate sector- and macro region specific sensitivities of hazard indicators, with the Standardised Precipitation Evapotranspiration Index for a twelve month aggregation period (SPEI-12) as the overall best hazard predictor. Vulnerability factors have only limited ability to predict drought impacts as single predictor, with information about landuse and water resources as best vulnerability-based predictors. (3) The application of the "hybrid approach" revealed strong regional (NUTS combo level) and sector specific differences in drought risk across Europe. The majority of best predictor combinations rely on a combination of SPEI for shorter and longer aggregation periods, and a combination of information on landuse and water resources. The added value of integrating regional vulnerability information

Potential involvement of drought-induced Ran GTPase CLRan1 in root growth enhancement in a xerophyte wild watermelon.

Science.gov (United States)

Akashi, Kinya; Yoshimura, Kazuya; Kajikawa, Masataka; Hanada, Kouhei; Kosaka, Rina; Kato, Atsushi; Katoh, Akira; Nanasato, Yoshihiko; Tsujimoto, Hisashi; Yokota, Akiho

2016-10-01

Enhanced root growth is known as the survival strategy of plants under drought. Previous proteome analysis in drought-resistant wild watermelon has shown that Ran GTPase, an essential regulator of cell division and proliferation, was induced in the roots under drought. In this study, two cDNAs were isolated from wild watermelon, CLRan1 and CLRan2, which showed a high degree of structural similarity with those of other plant Ran GTPases. Quantitative RT-PCR and promoter-GUS assays suggested that CLRan1 was expressed mainly in the root apex and lateral root primordia, whereas CLRan2 was more broadly expressed in other part of the roots. Immunoblotting analysis confirmed that the abundance of CLRan proteins was elevated in the root apex region under drought stress. Transgenic Arabidopsis overexpressing CLRan1 showed enhanced primary root growth, and the growth was maintained under osmotic stress, indicating that CLRan1 functions as a positive factor for maintaining root growth under stress conditions.

Overexpression of Nitrate Reductase in Tobacco Delays Drought-Induced Decreases in Nitrate Reductase Activity and mRNA1

Science.gov (United States)

Ferrario-Méry, Sylvie; Valadier, Marie-Hélène; Foyer, Christine H.

1998-01-01

Transformed (cauliflower mosaic virus 35S promoter [35S]) tobacco (Nicotiana plumbaginifolia L.) plants constitutively expressing nitrate reductase (NR) and untransformed controls were subjected to drought for 5 d. Drought-induced changes in biomass accumulation and photosynthesis were comparable in both lines of plants. After 4 d of water deprivation, a large increase in the ratio of shoot dry weight to fresh weight was observed, together with a decrease in the rate of photosynthetic CO2 assimilation. Foliar sucrose increased in both lines during water stress, but hexoses increased only in leaves from untransformed controls. Foliar NO3− decreased rapidly in both lines and was halved within 2 d of the onset of water deprivation. Total foliar amino acids decreased in leaves of both lines following water deprivation. After 4 d of water deprivation no NR activity could be detected in leaves of untransformed plants, whereas about 50% of the original activity remained in the leaves of the 35S-NR transformants. NR mRNA was much more stable than NR activity. NR mRNA abundance increased in the leaves of the 35S-NR plants and remained constant in controls for the first 3 d of drought. On the 4th d, however, NR mRNA suddenly decreased in both lines. Rehydration at d 3 caused rapid recovery (within 24 h) of 35S-NR transcripts, but no recovery was observed in the controls. The phosphorylation state of the protein was unchanged by long-term drought. There was a strong correlation between maximal extractable NR activity and ambient photosynthesis in both lines. We conclude that drought first causes increased NR protein turnover and then accelerates NR mRNA turnover. Constitutive NR expression temporarily delayed drought-induced losses in NR activity. 35S-NR expression may therefore allow more rapid recovery of N assimilation following short-term water deficit. PMID:9576799

Proteomic studies of drought stress response in Fabaceae

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Tanja ZADRAŽNIK

2015-11-01

Full Text Available Drought stress is a serious threat to crop production that influences plant growth and development and subsequently causes reduced quantity and quality of the yield. Plant stress induces changes in cell metabolism, which includes differential expression of proteins. Proteomics offer a powerful approach to analyse proteins involved in drought stress response of plants. Analyses of changes in protein abundance of legumes under drought stress are very important, as legumes play an important role in human and animal diet and are often exposed to drought. The presented results of proteomic studies of selected legumes enable better understanding of molecular mechanisms of drought stress response. The study of drought stress response of plants with proteomic approach may contribute to the development of potential drought-response markers and to the development of drought-tolerant cultivars of different legume crop species.

CO2 and temperature effects on morphological and physiological traits affecting risk of drought-induced mortality.

Science.gov (United States)

Duan, Honglang; Chaszar, Brian; Lewis, James D; Smith, Renee A; Huxman, Travis E; Tissue, David T

2018-04-26

Despite a wealth of eco-physiological assessments of plant response to extreme drought, few studies have addressed the interactive effects of global change factors on traits driving mortality. To understand the interaction between hydraulic and carbon metabolic traits influencing tree mortality, which may be independently influenced by atmospheric [CO2] and temperature, we grew Eucalyptus sideroxylon A. Cunn. ex Woolls from seed in a full-factorial [CO2] (280, 400 and 640 μmol mol-1, Cp, Ca and Ce, respectively) and temperature (ambient and ambient +4 °C, Ta and Te, respectively) experiment. Prior to drought, growth across treatment combinations resulted in significant variation in physiological and morphological traits, including photosynthesis (Asat), respiration (Rd), stomatal conductance, carbohydrate storage, biomass and leaf area (LA). Ce increased Asat, LA and leaf carbohydrate concentration compared with Ca, while Cp generated the opposite response; Te reduced Rd. However, upon imposition of drought, Te hastened mortality (9 days sooner compared with Ta), while Ce significantly exacerbated drought stress when combined with Te. Across treatments, earlier time-to-mortality was mainly associated with lower (more negative) leaf water potential (Ψl) during the initial drought phase, along with higher water loss across the first 3 weeks of water limitation. Among many variables, Ψl was more important than carbon status in predicting time-to-mortality across treatments, yet leaf starch was associated with residual variation within treatments. These results highlight the need to carefully consider the integration, interaction and hierarchy of traits contributing to mortality, along with their responses to environmental drivers. Both morphological traits, which influence soil resource extraction, and physiological traits, which affect water-for-carbon exchange to the atmosphere, must be considered to adequately predict plant response to drought. Researchers have

Predicting the release of metals from ombrotrophic peat due to drought-induced acidification

Energy Technology Data Exchange (ETDEWEB)

Tipping, E.; Smith, E.J.; Lawlor, A.J.; Hughes, S.; Stevens, P.A

2003-05-01

Metals stored in peats can be remobilised by sulphuric acid, generated by the drought-induced oxidation of reduced sulphur. - Ombrotrophic peats in northern England and Scotland, close to industrial areas, have substantial contents of potentially toxic metals (Al, Ni, Cu, Zn, Cd and Pb) and of pollutant sulphur, all derived from atmospheric deposition. The peat sulphur, ordinarily in reduced form, may be converted to sulphuric acid under drought conditions, due to the entry of oxygen into the peats. The consequent lowering of soil solution pH is predicted to cause the release of metals held on ligand sites of the peat organic matter. The purpose of the present study was to explore, by simulation modelling, the extent of the metal response. Chemical variables (elemental composition, pH, metal contents) were measured for samples of ombrotrophic peats from three locations. Water extracts of the peats, and samples of local surface water, were also analysed, for pH, dissolved organic carbon (DOC) and metals. Metal release from peats due to acidification was demonstrated experimentally, and could be accounted for reasonably well using a speciation code (WHAM/Model VI). These data, together with information on metal and S deposition, and meteorology, were used to construct a simple description of peat hydrochemistry, based on WHAM/Model VI, that takes into account ion-binding by humic substances (assumed to be the 'active' constituents of the peat with respect to ion-binding). The model was used to simulate steady state situations that approximated the observed soil pH, metal pools and dissolved metal concentrations. Then, drought conditions were imposed, to generate increased concentrations of H{sub 2}SO{sub 4}, in line with those observed during the drought of 1995. The model calculations suggest that the pH will decrease from the initial steady state value of 4.3 to 3.3-3.6 during rewetting periods following droughts, depending upon assumptions about the

Relationship of Climatic and Forest Factors to Drought- and Heat-Induced Tree Mortality.

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Qingyin Zhang

Full Text Available Tree mortality due to warming and drought is a critical aspect of forest ecosystem in responding to climate change. Spatial patterns of tree mortality induced by drought and its influencing factors, however, have yet to be documented at the global scale. We collected observations from 248 sites globally where trees have died due to drought and then assessed the effects of climatic and forest factors on the rate of tree mortality. The global mean annual mortality rate was 5.5%. The rate of tree mortality was significantly and negatively correlated with mean annual precipitation (P 2000 mm and was severe in regions with mean annual precipitation <1000 mm. Mortality rates varied amongst species. The global annual rate of mortality was much higher for gymnosperms (7.1% than angiosperms (4.8% but did not differ significantly between evergreen (6.2% and deciduous (6.1% species. Stand age and wood density affected the mortality rate. Saplings (4.6% had a higher mortality rate than mature trees (3.2%, and mortality rates significantly decreased with increasing wood density for all species (P < 0.01. We therefore concluded that the tree mortality around the globe varied with climatic and forest factors. The differences between tree species, wood density, stand density, and stand age should be considered when evaluating tree mortality at a large spatial scale during future climatic extremes.

Effect of polyethylene glycol induced drought stress on physio-hormonal attributes of soybean

International Nuclear Information System (INIS)

Hamayun, M.; Khan, A.L.; Ahmad, N.; Lee, In-Jung; Khan, S.A.; Shinwari, Z.K.

2010-01-01

Drought stress is a major abiotic constraint limiting crop production world wide. In current study, we investigated the adverse effects of drought stress on growth, yield and endogenous phytohormones of soybean. Polyethylene glycol (PEG) solutions of elevated strength (8% and 16%) were used for drought stress induction. Drought stress period span for two weeks each at pre and post flowering growth stage. It was observed that soybean growth and yield attributes significantly reduced under drought stress at both pre and post flowering period, while maximum reduction was caused by PEG (16%) applied at pre flowering time. The endogenous bioactive GA/sub 1/ and GA/sub 4/ content decreased under elevated drought stress. On the other hand, jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA) content increased under drought stress. On the basis of current study, we concluded that application of earlier drought stress severely reduced growth and yield attributes of soybean when compared to its later application. Furthermore, increases in the endogenous contents of JA, SA and ABA in response to drought stress demonstrate the involvement of these hormones in drought stress resistance. (author)

Environmental Sustainability of Agriculture Stressed by Changing Extremes of Drought and Excess Moisture: A Conceptual Review

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Elaine Wheaton

2017-06-01

Full Text Available As the climate changes, the effects of agriculture on the environment may change. In the future, an increasing frequency of climate extremes, such as droughts, heat waves, and excess moisture, is expected. Past research on the interaction between environment and resources has focused on climate change effects on various sectors, including agricultural production (especially crop production, but research on the effects of climate change using agri-environmental indicators (AEI of environmental sustainability of agriculture is limited. The aim of this paper was to begin to address this knowledge gap by exploring the effects of future drought and excess moisture on environmental sustainability of agriculture. Methods included the use of a conceptual framework, literature reviews, and an examination of the climate sensitivities of the AEI models. The AEIs assessed were those for the themes of soil and water quality, and farmland management as developed by Agriculture and Agri-Food Canada. Additional indicators included one for desertification and another for water supply and demand. The study area was the agricultural region of the Canadian Prairie Provinces. We found that the performance of several indicators would likely decrease in a warming climate with more extremes. These indicators with declining performances included risks for soil erosion, soil salinization, desertification, water quality and quantity, and soil contamination. Preliminary trends of other indicators such as farmland management were not clear. AEIs are important tools for measuring climate impacts on the environmental sustainability of agriculture. They also indicate the success of adaptation measures and suggest areas of operational and policy development. Therefore, continued reporting and enhancement of these indicators is recommended.

Arabidopsis calcium-dependent protein kinase AtCPK1 plays a positive role in salt/drought-stress response.

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Huang, Kui; Peng, Lu; Liu, Yingying; Yao, Rundong; Liu, Zhibin; Li, Xufeng; Yang, Yi; Wang, Jianmei

2018-03-25

The calcium-dependent protein kinases (CDPKs) play vital roles in plant response to various environmental stimuli. Here, we investigated the function of Arabidopsis AtCPK1 in response to salt and drought stress. The loss-of-function cpk1 mutant displayed hypersensitive to salt and drought stress, whereas overexpressing AtCPK1 in Arabidopsis plants significantly enhanced the resistance to salt or drought stress. The reduced or elevated tolerance of cpk1 mutant and AtCPK1-overexpressing lines was confirmed by the changes of proline, malondialdehyde (MDA) and H 2 O 2 . Real-time PCR analysis revealed that the expression of several stress-inducible genes (RD29A, COR15A, ZAT10, APX2) down-regulated in cpk1 mutant and up-regulated in AtCPK1-overexpressing plants. These results are likely to indicate that AtCPK1 positively regulates salt and drought stress in Arabidopsis. Copyright © 2017 Elsevier Inc. All rights reserved.

Estimating drought induced tree mortality in the Amazon rainforest: A simulation study with a focus on plant hydraulic processes

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Papastefanou, P.; Fleischer, K.; Hickler, T.; Grams, T.; Lapola, D.; Quesada, C. A.; Zang, C.; Rammig, A.

2017-12-01

The Amazon basin was recently hit by severe drought events that were unprecedented in their severity and spatial extent, e.g. during 2005, 2010 and 2015/2016. Significant amounts of biomass were lost, turning large parts of the rainforest from a carbon sink into a carbon source. It is assumed that drought-induced tree mortality from hydraulic failure played an important role during these events and may become more frequent in the Amazon region in the future. Many state-of-the-art dynamic vegetation models do not include plant hydraulic processes and fail to reproduce observed rainforest responses to drought events, such as e.g. increased tree mortality. We address this research gap by developing a simple plant-hydraulic module for the dynamic vegetation model LPJ-GUESS. This plant-hydraulic module uses leaf water potential and cavitation as baseline processes to simulate tree mortality under drought stress. Furthermore, we introduce different plant strategies in the model, which describe e.g. differences in the stomatal regulation under drought stress. To parameterize and evaluate our hydraulic module, we use a set of available observational data from the Amazon region. We apply our model to the Amazon Basin and highlight similarities and differences across other measured and predicted drought responses, e.g. extrapolated observations and data derived from satellite measurements. Our results highlight the importance of including plant hydraulic processes in dynamic vegetation models to correctly predict vegetation dynamics under drought stress and show major differences on the vegetation dynamics depending on the selected plant strategies. We also identify gaps in process understanding of the triggering factors, the extent and the consequences of drought responses that hampers our ability to predict potential impact of future drought events on the Amazon rainforest.

Disentangling drought-induced variation in ecosystem and soil respiration using stable carbon isotopes.

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Unger, Stephan; Máguas, Cristina; Pereira, João S; Aires, Luis M; David, Teresa S; Werner, Christiane

2010-08-01

Combining C flux measurements with information on their isotopic composition can yield a process-based understanding of ecosystem C dynamics. We studied the variations in both respiratory fluxes and their stable C isotopic compositions (delta(13)C) for all major components (trees, understory, roots and soil microorganisms) in a Mediterranean oak savannah during a period with increasing drought. We found large drought-induced and diurnal dynamics in isotopic compositions of soil, root and foliage respiration (delta(13)C(res)). Soil respiration was the largest contributor to ecosystem respiration (R (eco)), exhibiting a depleted isotopic signature and no marked variations with increasing drought, similar to ecosystem respired delta(13)CO(2), providing evidence for a stable C-source and minor influence of recent photosynthate from plants. Short-term and diurnal variations in delta(13)C(res) of foliage and roots (up to 8 and 4 per thousand, respectively) were in agreement with: (1) recent hypotheses on post-photosynthetic fractionation processes, (2) substrate changes with decreasing assimilation rates in combination with increased respiratory demand, and (3) decreased phosphoenolpyruvate carboxylase activity in drying roots, while altered photosynthetic discrimination was not responsible for the observed changes in delta(13)C(res). We applied a flux-based and an isotopic flux-based mass balance, yielding good agreement at the soil scale, while the isotopic mass balance at the ecosystem scale was not conserved. This was mainly caused by uncertainties in Keeling plot intercepts at the ecosystem scale due to small CO(2) gradients and large differences in delta(13)C(res) of the different component fluxes. Overall, stable isotopes provided valuable new insights into the drought-related variations of ecosystem C dynamics, encouraging future studies but also highlighting the need of improved methodology to disentangle short-term dynamics of isotopic composition of R (eco).

Influence of PEG induced drought stress on molecular and biochemical constituents and seedling growth of Egyptian barley cultivars

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F.A. Hellal

2018-06-01

Full Text Available In order to investigate the effects of drought stress on germination components of barley cultivars, a laboratory experiment was conducted in a factorial randomized complete design with four replications. The controlled experiment included ten of Egyptian barley cultivars namely; (Giza 123, 124, 125, 126, 127, 129, 130, 134, 135 and 2000 as first factor. The second factor included 4 levels of drought stress inducer by applying 0, 5, 10 and 20% of polyethylene glycol-6000 (PEG which is equivalent to four osmotic potential levels including −0.001, −0.27, −0.54 and −1.09 MPa, respectively. The results showed that, the highest reduction was related to the drought level of 20% PEG among the barley cultivars. The best cultivars in terms of germination traits were Giza 134, Giza 127, and Giza 126 this indicate their tolerance to drought stress and Giza 130, 135, 2000 cultivars was moderately tolerance and remaining is less tolerance. The protein band 27 kDa and 78 kDa showed high intensity after stress in almost all cultivars. Those two protein bands their exciting was very clear in treated barley leaf tissue. It could be related to dehydrine and oxygen evolving enhancer protein 2 (OEE2 which involved in drought stress tolerance response. Cultivars Giza 127, 130 and 134 showed highest tolerance response under drought stress. The antioxidant enzymes PAGE pattern of Peroxidase (POX, Sodium dismutase (SOD and Ascorbate peroxidase (APX for Barley cultivars under drought stress revealed a high activities for Giza 126, 127, 134, 136 and 2000 under −0.5 MPa osmotic stress by PEG in most of their isoforms. Based on similarity coefficient values the highest values were 1.0 with 100% similarly between tolerant cultivars Giza 130 and Giza 127. Similarly between the susceptible cultivars 125 and Giza 129 was 60%.These data confirmed by the growth parameters which we ranked as tolerant to drought stress. Keywords: Barley, Drought stress, Seed germination

Global drought watch from space at work: Crop losses and food security

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Kogan, F.

2012-12-01

Drought is one of the most adverse environmental disasters. It affects countries economies, environment a very large number of people in the world. Only in the USA drought costs taxpayers nearly $6 billion each year. Drought is a very unusual phenomenon because unlike other environmental disaster it starts unnoticeably, develop cumulatively, the impact is also cumulative and by the time when the effect of drought is observable it is too late to mitigate the consequences. Therefore, it is difficult to mitigate droughts using in situ data. The National Oceanic and Atmospheric Administration (NOAA) developed new method for drought detection and monitoring from reflectance measured by the Advanced Very High Resolution Radiometer flown on NOAA polar-orbiting operational environmental satellites. The method calculates Vegetation Health (VH) indices, which estimate vegetation condition (health) on a scale from extreme stress to favorable conditions based on intensity of greenness, vigor and thermal condition of vegetation canopy. The VH is estimated every week for each 4 by 4 km earth surface and is delivered to the NOAA/NESDIS web site in digital and color-coded form. The web site address is the following http://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/index.php In addition to drought and vegetation health monitoring, the VH indices are applied in agriculture, forestry, mosquito-borne diseases, climate, invasive species and others. During the first seven months of 2009, drought was observed in the southern US (especially Texas), Argentina (very intensive drought), some of the countries of sub-Sahara Africa, India (central and eastern), Kazakhstan and Australia.

Drought-induced vegetation stress in southwestern North America

International Nuclear Information System (INIS)

Zhang Xiaoyang; Goldberg, Mitchell; Tarpley, Dan; Kogan, Felix; Yu Yunyue; Friedl, Mark A; Morisette, Jeffrey

2010-01-01

Trends towards earlier greenup and increased average greenness have been widely reported in both humid and dry ecosystems. By analyzing NOAA (National Oceanic and Atmospheric Administration) AVHRR (Advanced Very High Resolution Radiometer) data from 1982 to 2007, we report complex trends in both the growing season amplitude and seasonally integrated vegetation greenness in southwestern North America and further highlight regions consistently experiencing drought stress. In particular, greenness measurements from 1982 to 2007 show an increasing trend in grasslands but a decreasing trend in shrublands. However, vegetation greenness in this period has experienced a strong cycle, increasing from 1982 to 1993 but decreasing from 1993 to 2007. The significant decrease during the last decade has reduced vegetation greenness by 6% in shrublands and 13% in grasslands (16% and 21%, respectively, in the severe drought years). The greenness cycle correlates to both annual precipitation and dry season length derived from NOAA North America Regional Reanalysis data. If drought events continue as predicted by climate models, they will exacerbate ecosystem degradation and reduce carbon uptake.

Responses of photosynthetic parameters to drought in subtropical forest ecosystem of China

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Zhou, Lei; Wang, Shaoqiang; Chi, Yonggang; Li, Qingkang; Huang, Kun; Yu, Quanzhou

2015-12-01

The mechanism underlying the effect of drought on the photosynthetic traits of leaves in forest ecosystems in subtropical regions is unclear. In this study, three limiting processes (stomatal, mesophyll and biochemical limitations) that control the photosynthetic capacity and three resource use efficiencies (intrinsic water use efficiency (iWUE), nitrogen use efficiency (NUE) and light use efficiency (LUE)), which were characterized as the interactions between photosynthesis and environmental resources, were estimated in two species (Schima superba and Pinus massoniana) under drought conditions. A quantitative limitation analysis demonstrated that the drought-induced limitation of photosynthesis in Schima superba was primarily due to stomatal limitation, whereas for Pinus massoniana, both stomatal and non-stomatal limitations generally exhibited similar magnitudes. Although the mesophyll limitation represented only 1% of the total limitation in Schima superba, it accounted for 24% of the total limitations for Pinus massoniana. Furthermore, a positive relationship between the LUE and NUE and a marginally negative relationship or trade-off between the NUE and iWUE were observed in the control plots. However, drought disrupted the relationships between the resource use efficiencies. Our findings may have important implications for reducing the uncertainties in model simulations and advancing the understanding of the interactions between ecosystem functions and climate change.

Resilience of freshwater communities of small microbial eukaryotes undergoing severe drought events

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Marianne eSimon

2016-05-01

Full Text Available Small and shallow aquatic ecosystems such as ponds and streams constitute a significant proportion of continental surface waters, especially in temperate zones. In comparison with bigger lakes and rivers, they harbor higher biodiversity but they also exhibit reduced buffering capacity face to environmental shifts, such that climate global change can affect them in a more drastic way. For instance, many temperate areas are predicted to undergo droughts with increasing frequency in the near future, which may lead to the temporal desiccation of streams and ponds. In this work, we monitored temporal dynamics of planktonic communities of microbial eukaryotes (cell size range 0.2-5 µm in one brook and one pond that experienced recurrent droughts from 1 to 5 consecutive months during a temporal survey carried out monthly for two years based on high-throughput 18S rDNA metabarcoding. During drought-induced desiccation events, protist communities present in the remaining dry sediment, though highly diverse, differed radically from their planktonic counterparts. However, after water refill, the aquatic protist assemblages recovered their original structure within a month. This rapid recovery indicates that these eukaryotic communities are resilient to droughts, most likely via the entrance in dormancy. This property is essential for the long-term survival and functional stability of small freshwater ecosystems.

Exploring standardized precipitation evapotranspiration index for drought assessment in Bangladesh.

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Miah, Md Giashuddin; Abdullah, Hasan Muhammad; Jeong, Changyoon

2017-10-09

Drought is a critical issue, and it has a pressing, negative impact on agriculture, ecosystems, livelihoods, food security, and sustainability. The problem has been studied globally, but its regional or even local dimension is sometimes overlooked. Local-level drought assessment is necessary for developing adaptation and mitigation strategies for that particular region. Keeping this in understanding, an attempt was made to create a detailed assessment of drought characteristics at the local scale in Bangladesh. Standardized precipitation evapotranspiration (SPEI) is a new drought index that mainly considers the rainfall and evapotranspiration data set. Globally, SPEI has become a useful drought index, but its local scale application is not common. SPEI base (0.5° grid data) for 110 years (1901-2011) was utilized to overcome the lack of long-term climate data in Bangladesh. Available weather data (1955-2011) from Bangladesh Meteorology Department (BMD) were analyzed to calculate SPEI weather station using the SPEI calculator. The drivers for climate change-induced droughts were characterized by residual temperature and residual rainfall data from different BMD stations. Grid data (SPEI base ) of 26 stations of BMD were used for drought mapping. The findings revealed that the frequency and intensity of drought are higher in the northwestern part of the country which makes it vulnerable to both extreme and severe droughts. Based on the results, the SPEI-based drought intensity and frequency analyses were carried out, emphasizing Rangpur (northwest region) as a hot spot, to get an insight of drought assessment in Bangladesh. The findings of this study revealed that SPEI could be a valuable tool to understand the evolution and evaluation of the drought induced by climate change in the country. The study also justified the immediate need for drought risk reduction strategies that should lead to relevant policy formulations and agricultural innovations for developing

GhWRKY68 reduces resistance to salt and drought in transgenic Nicotiana benthamiana.

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Haihong Jia

Full Text Available The WRKY transcription factors modulate numerous physiological processes, including plant growth, development and responses to various environmental stresses. Currently, our understanding of the functions of the majority of the WRKY family members and their possible roles in signalling crosstalk is limited. In particular, very few WRKYs have been identified and characterised from an economically important crop, cotton. In this study, we characterised a novel group IIc WRKY gene, GhWRKY68, which is induced by different abiotic stresses and multiple defence-related signalling molecules. The β-glucuronidase activity driven by the GhWRKY68 promoter was enhanced after exposure to drought, salt, abscisic acid (ABA and H2O2. The overexpression of GhWRKY68 in Nicotiana benthamiana reduced resistance to drought and salt and affected several physiological indices. GhWRKY68 may mediate salt and drought responses by modulating ABA content and enhancing the transcript levels of ABA-responsive genes. GhWRKY68-overexpressing plants exhibited reduced tolerance to oxidative stress after drought and salt stress treatments, which correlated with the accumulation of reactive oxygen species (ROS, reduced enzyme activities, elevated malondialdehyde (MDA content and altered ROS-related gene expression. These results indicate that GhWRKY68 is a transcription factor that responds to drought and salt stresses by regulating ABA signalling and modulating cellular ROS.

Intensification of hydrological drought due to human activity in the middle reaches of the Yangtze River, China.

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Zhang, Dan; Zhang, Qi; Qiu, Jiaming; Bai, Peng; Liang, Kang; Li, Xianghu

2018-10-01

Hydrological extremes are changing under the impacts of environmental change, i.e., climate variation and human activity, which can substantially influence ecosystems and the living environment of humans in affected region. This study investigates the impacts of environmental change on hydrological drought in the middle reaches of the Yangtze River in China based on hydrological modelling. Change points for streamflow into two major lakes and a reservoir in the study area were detected in the late 1980s using the Mann-Kendall test. Streamflow simulation by a water balance model was performed, and the resulting Kling-Gupta efficiency value was >0.90. Hydrological drought events were identified based on the simulated streamflow under different scenarios. The results show that the hydrological drought occurrence was increased by precipitation, whereas the drought peak value was increased by potential evapotranspiration. The impacts of precipitation and potential evapotranspiration on drought severity and duration varied in the study area. However, hydrological drought was intensified by the influence of human activity, which increased the severity, duration and peak value of droughts. The dominant factor for hydrological drought severity is precipitation, followed by potential evapotranspiration and human activity. The impacts of climate variation and human activity on drought severity are larger than on drought duration. In addition, environmental change is shown to have an "accumulation effect" on hydrological drought, demonstrating that the indirect impacts of environmental change on hydrological drought are much larger than the direct impacts on streamflow. This study improves our understanding of the responses of hydrological extremes to environmental change, which is useful for the management of water resources and the prediction of hydrological disasters. Copyright © 2018 Elsevier B.V. All rights reserved.

Drought-induced recharge promotes long-term storage of porewater salinity beneath a prairie wetland

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Levy, Zeno F.; Rosenberry, Donald O.; Moucha, Robert; Mushet, David M.; Goldhaber, Martin B.; LaBaugh, James W.; Fiorentino, Anthony J.; Siegel, Donald I.

2018-02-01

Subsurface storage of sulfate salts allows closed-basin wetlands in the semiarid Prairie Pothole Region (PPR) of North America to maintain moderate surface water salinity (total dissolved solids [TDS] from 1 to 10 g L-1), which provides critical habitat for communities of aquatic biota. However, it is unclear how the salinity of wetland ponds will respond to a recent shift in mid-continental climate to wetter conditions. To understand better the mechanisms that control surface-subsurface salinity exchanges during regional dry-wet climate cycles, we made a detailed geoelectrical study of a closed-basin prairie wetland (P1 in the Cottonwood Lake Study Area, North Dakota) that is currently experiencing record wet conditions. We found saline lenses of sulfate-rich porewater (TDS > 10 g L-1) contained in fine-grained wetland sediments 2-4 m beneath the bathymetric low of the wetland and within the currently ponded area along the shoreline of a prior pond stand (c. 1983). During the most recent drought (1988-1993), the wetland switched from a groundwater discharge to recharge function, allowing salts dissolved in surface runoff to move into wetland sediments beneath the bathymetric low of the basin. However, groundwater levels during this time did not decline to the elevation of the saline lenses, suggesting these features formed during more extended paleo-droughts and are stable in the subsurface on at least centennial timescales. We hypothesize a "drought-induced recharge" mechanism that allows wetland ponds to maintain moderate salinity under semiarid climate. Discharge of drought-derived saline groundwater has the potential to increase the salinity of wetland ponds during wet climate.

Herbaceous Angiosperms Are Not More Vulnerable to Drought-Induced Embolism Than Angiosperm Trees.

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Lens, Frederic; Picon-Cochard, Catherine; Delmas, Chloé E L; Signarbieux, Constant; Buttler, Alexandre; Cochard, Hervé; Jansen, Steven; Chauvin, Thibaud; Doria, Larissa Chacon; Del Arco, Marcelino; Delzon, Sylvain

2016-10-01

The water transport pipeline in herbs is assumed to be more vulnerable to drought than in trees due to the formation of frequent embolisms (gas bubbles), which could be removed by the occurrence of root pressure, especially in grasses. Here, we studied hydraulic failure in herbaceous angiosperms by measuring the pressure inducing 50% loss of hydraulic conductance (P 50 ) in stems of 26 species, mainly European grasses (Poaceae). Our measurements show a large range in P 50 from -0.5 to -7.5 MPa, which overlaps with 94% of the woody angiosperm species in a worldwide, published data set and which strongly correlates with an aridity index. Moreover, the P 50 values obtained were substantially more negative than the midday water potentials for five grass species monitored throughout the entire growing season, suggesting that embolism formation and repair are not routine and mainly occur under water deficits. These results show that both herbs and trees share the ability to withstand very negative water potentials without considerable embolism formation in their xylem conduits during drought stress. In addition, structure-function trade-offs in grass stems reveal that more resistant species are more lignified, which was confirmed for herbaceous and closely related woody species of the daisy group (Asteraceae). Our findings could imply that herbs with more lignified stems will become more abundant in future grasslands under more frequent and severe droughts, potentially resulting in lower forage digestibility. © 2016 American Society of Plant Biologists. All Rights Reserved.

JUNGBRUNNEN1 Confers Drought Tolerance Downstream of the HD-Zip I Transcription Factor AtHB13

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Saghar Ebrahimian-Motlagh

2017-12-01

Full Text Available Low water availability is the major environmental factor limiting growth and productivity of plants and crops and is therefore considered of high importance for agriculture affected by climate change. Identifying regulatory components controlling the response and tolerance to drought stress is thus of major importance. The NAC transcription factor (TF JUNGBRUNNEN1 (JUB1 from Arabidopsis thaliana extends leaf longevity under non-stress growth conditions, lowers cellular hydrogen peroxide (H2O2 level, and enhances tolerance against heat stress and salinity. Here, we additionally find that JUB1 strongly increases tolerance to drought stress in Arabidopsis when expressed from both, a constitutive (CaMV 35S and an abiotic stress-induced (RD29A promoter. Employing a yeast one-hybrid screen we identified HD-Zip class I TF AtHB13 as an upstream regulator of JUB1. AtHB13 has previously been reported to act as a positive regulator of drought tolerance. AtHB13 and JUB1 thereby establish a joint drought stress control module.

Heme oxygenase-1 delays gibberellin-induced programmed cell death of rice aleurone layers subjected to drought stress by interacting with nitric oxide

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Huangming eWu

2016-01-01

Full Text Available Cereal aleurone layers undergo a gibberellin (GA-regulated process of programmed cell death (PCD following germination. Heme oxygenase-1 (HO-1 is known as a rate-liming enzyme in the degradation of heme to biliverdin IXα (BV, carbon monoxide (CO, and free iron ions (Fe2+. It is a critical component in plant development and adaptation to environment stresses. Our previous studies confirmed that HO-1 inducer hematin (Ht promotes the germination of rice seeds in drought (20% polyethylene glycol-6000, PEG conditions, but the corresponding effects of HO-1 on the alleviation of germination-triggered PCD in GA-treated rice aleurone layers remain unknown. The present study has determined that GA co-treated with PEG results in lower HO-1 transcript levels and HO activity, which in turn results in the development of vacuoles in aleurone cells, followed by PCD. The pharmacology approach illustrated that up- or down-regulated HO-1 gene expression and HO activity delayed or accelerated GA-induced PCD. Furthermore, the application of the HO-1 inducer hematin and nitric oxide (NO donor sodium nitroprusside (SNP not only activated HO-1 gene expression, HO activity, and endogenous NO content, but also blocked GA-induced rapid vacuolation and accelerated aleurone layers PCD under drought stress. However, both HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX and NO scavenger 2-(4-carboxyphenyl0-4, 4, 5, 5-tetramethylimidazoline-l-oxyl-3-oxide potassium salt (cPTIO reserved the effects of hematin and SNP on rice aleurone layer PCD under drought stress by down-regulating endogenous HO-1 and NO, respectively. The inducible effects of hematin and SNP on HO-1 gene expression, HO activity, and NO content were blocked by cPTIO. Together, these results clearly suggest that HO-1 is involved in the alleviation of GA-induced PCD of drought-triggered rice aleurone layers by associating with NO.

Drought-induced defoliation and long periods of near-zero gas exchange play a key role in accentuating metabolic decline of Scots pine.

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Poyatos, Rafael; Aguadé, David; Galiano, Lucía; Mencuccini, Maurizio; Martínez-Vilalta, Jordi

2013-10-01

Drought-induced defoliation has recently been associated with the depletion of carbon reserves and increased mortality risk in Scots pine (Pinus sylvestris). We hypothesize that defoliated individuals are more sensitive to drought, implying that potentially higher gas exchange (per unit of leaf area) during wet periods may not compensate for their reduced photosynthetic area. We measured sap flow, needle water potentials and whole-tree hydraulic conductance to analyse the drought responses of co-occurring defoliated and nondefoliated Scots pines in northeast Spain during typical (2010) and extreme (2011) drought conditions. Defoliated Scots pines showed higher sap flow per unit leaf area during spring, but were more sensitive to summer drought, relative to nondefoliated pines. This pattern was associated with a steeper decline in soil-to-leaf hydraulic conductance with drought and an enhanced sensitivity of canopy conductance to soil water availability. Near-homeostasis in midday water potentials was observed across years and defoliation classes, with minimum values of -2.5 MPa. Enhanced sensitivity to drought and prolonged periods of near-zero gas exchange were consistent with low levels of carbohydrate reserves in defoliated trees. Our results support the critical links between defoliation, water and carbon availability, and their key roles in determining tree survival and recovery under drought. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Deciduous forest responses to temperature, precipitation, and drought imply complex climate change impacts.

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Xie, Yingying; Wang, Xiaojing; Silander, John A

2015-11-03

Changes in spring and autumn phenology of temperate plants in recent decades have become iconic bio-indicators of rapid climate change. These changes have substantial ecological and economic impacts. However, autumn phenology remains surprisingly little studied. Although the effects of unfavorable environmental conditions (e.g., frost, heat, wetness, and drought) on autumn phenology have been observed for over 60 y, how these factors interact to influence autumn phenological events remain poorly understood. Using remotely sensed phenology data from 2001 to 2012, this study identified and quantified significant effects of a suite of environmental factors on the timing of fall dormancy of deciduous forest communities in New England, United States. Cold, frost, and wet conditions, and high heat-stress tended to induce earlier dormancy of deciduous forests, whereas moderate heat- and drought-stress delayed dormancy. Deciduous forests in two eco-regions showed contrasting, nonlinear responses to variation in these explanatory factors. Based on future climate projection over two periods (2041-2050 and 2090-2099), later dormancy dates were predicted in northern areas. However, in coastal areas earlier dormancy dates were predicted. Our models suggest that besides warming in climate change, changes in frost and moisture conditions as well as extreme weather events (e.g., drought- and heat-stress, and flooding), should also be considered in future predictions of autumn phenology in temperate deciduous forests. This study improves our understanding of how multiple environmental variables interact to affect autumn phenology in temperate deciduous forest ecosystems, and points the way to building more mechanistic and predictive models.

Evidence That Drought-Induced Stomatal Closure Is Not an Important Constraint on White Spruce Performance Near the Arctic Treeline in Alaska

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Sullivan, P.; Brownlee, A.; Ellison, S.; Sveinbjornsson, B.

2014-12-01

Tree cores collected from trees growing at high latitudes have long been used to reconstruct past climates, because of close positive correlations between temperature and tree growth. However, in recent decades and at many sites, these relationships have deteriorated and have even become negative in some instances. The observation of declining tree growth in response to rising temperature has prompted many investigators to suggest that high latitude trees may be increasingly exhibiting drought-induced stomatal closure. In the Brooks Range of northern Alaska, the observation of low and declining growth of white spruce is more prevalent in the central and eastern parts of the range, where precipitation is lower, providing superficial support for the drought stress hypothesis. In this study, we investigated the occurrence of white spruce drought-induced stomatal closure in four watersheds along a west to east gradient near the Arctic treeline in the Brooks Range. We obtained a historical perspective on tree growth and water relations by collecting increment cores for analysis of ring widths and carbon isotopes in tree-ring alpha-cellulose. Meanwhile, we made detailed assessments of contemporary water relations at the scales of the whole canopy and the needle. All of our data indicate that drought-induced stomatal closure is probably not responsible for low and declining growth in the central and eastern Brooks Range. Carbon isotope discrimination has generally increased over the past century and our calculations indicate that needle inter-cellular CO2 concentration is much greater now than it was in the early 1900's. Measurements of needle gas exchange are consistent with the tree core record, in the sense that instances of low photosynthesis at our sites are not coincident with similarly low stomatal conductance and low inter-cellular CO2 concentration. Finally, hourly measurements of xylem sap flow indicate that trees at our study sites are able to maintain near

Drought tolerant wheat varieties developed through mutation ...

African Journals Online (AJOL)

In search for higher yielding drought tolerant wheat varieties, one of the Kenyan high yielding variety 'Pasa' was irradiated with gamma rays (at 150, 200, and 250gy) in 1997 so as to induce variability and select for drought tolerance. Six mutants ((KM10, KM14, KM15, KM18, KM20 and KM21) were selected at M4 for their ...

Natural recovery and leaf water potential after fire influenced by salvage logging and induced drought stress

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D. Moya

2013-01-01

Full Text Available Salvage logging is one of the most common emergency actions in the short-term management after a fire. Several studies have been carried out and some obtained positive results which incite to carry it out but other, found negative effects on seedling establishment and regeneration. In addition, climatic changes will have large impacts on vegetation productivity and resilience since the regional models for south-eastern Spain predicts a rainfall decrease of about 20% and temperature increase of 4.5 ºC. Our aim was to determine how short-term forest management and induced drought affect the ecosystem recovery in Aleppo pine stands naturally recovered after a fire.In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine (Pinus halepensis Mill. forest in south-eastern Spain. Six months later, a salvage logging was carried out. The Aleppo pine recruitment was negligible. During summer 2010, twelve square plots (2m x 2m were set in the three scenarios: control, salvaged and drought induced. The surface cover and soil water availability for three dominant understory species were recorded in four field campaigns: Spring-2010, Fall-2010, Spring-2011 and Fall-2011.The season, management and the target species showed significant differences in growing and water stress. In general, Esparto grass showed lower water stress, mainly in Fall, a higher increase of total coverage. Both effects were showing their highest values in non-salvaged areas and no drought. Changes in leaf water potential and soil water content after the drought season influence the survival and development of individuals.Our results indicate that soil water content and ecosystem response can be modified by short-term silvicultural treatments. Therefore, management after fire could cause opposite effects to those initially foreseen, since they depend on fire severity, and type of ecosystem management response. So, their application must be evaluated and assessed before

Stress-inducible expression of an F-box gene TaFBA1 from wheat enhanced the drought tolerance in transgenic tobacco plants without impacting growth and development

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Xiangzhu Kong

2016-09-01

Full Text Available E3 ligase plays an important role in the response to many environment stresses in plants. In our previous study, constitutive overexpression of an F-box protein gene TaFBA1 driven by 35S promoter improved the drought tolerance in transgenic tobacco plants, but the growth and development in transgenic plants was altered in normal conditions. In this study, we used stress-inducible promoter RD29A instead of 35S promoter, as a results, the stress-inducible transgenic tobacco plants exhibit a similar phenotype with WT plants. However, the drought tolerance of the transgenic plants with stress-inducible expressed TaFBA1 was enhanced. The improved drought tolerance of transgenic plants was indicated by their higher seed germination rate and survival rate, greater biomass and photosynthesis than those of WT under water stress, which may be related to their greater water retention capability and osmotic adjustment. Moreover, the transgenic plants accumulated less reactive oxygen species (ROS, kept lower MDA content and membrane leakage under water stress, which may be related to their higher levels of antioxidant enzyme activity and upregulated gene expression of some antioxidant enzymes. These results suggest that stress induced expression of TaFBA1 confers drought tolerance via the improved water retention and antioxidative compete abilibty. Meanwhile, this stress-inducible expression strategy by RD29A promoter can minimize the unexpectable effects by 35S constitutive promoter on phenotypes of the transgenic plants.

Stress-Inducible Expression of an F-box Gene TaFBA1 from Wheat Enhanced the Drought Tolerance in Transgenic Tobacco Plants without Impacting Growth and Development.

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Kong, Xiangzhu; Zhou, Shumei; Yin, Suhong; Zhao, Zhongxian; Han, Yangyang; Wang, Wei

2016-01-01

E3 ligase plays an important role in the response to many environment stresses in plants. In our previous study, constitutive overexpression of an F-box protein gene TaFBA1 driven by 35S promoter improved the drought tolerance in transgenic tobacco plants, but the growth and development in transgenic plants was altered in normal conditions. In this study, we used stress-inducible promoter RD29A instead of 35S promoter, as a results, the stress-inducible transgenic tobacco plants exhibit a similar phenotype with wild type (WT) plants. However, the drought tolerance of the transgenic plants with stress-inducible expressed TaFBA1 was enhanced. The improved drought tolerance of transgenic plants was indicated by their higher seed germination rate and survival rate, greater biomass and photosynthesis than those of WT under water stress, which may be related to their greater water retention capability and osmotic adjustment. Moreover, the transgenic plants accumulated less reactive oxygen species, kept lower MDA content and membrane leakage under water stress, which may be related to their higher levels of antioxidant enzyme activity and upregulated gene expression of some antioxidant enzymes. These results suggest that stress induced expression of TaFBA1 confers drought tolerance via the improved water retention and antioxidative compete ability. Meanwhile, this stress-inducible expression strategy by RD29A promoter can minimize the unexpectable effects by 35S constitutive promoter on phenotypes of the transgenic plants.

Initiating rain water harvest technology for climate change induced drought resilient agriculture: scopes and challenges in Bangladesh

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Hasan Muhammad Abdullah

2015-12-01

Full Text Available Bangladesh is primarily an agrarian economy. Agriculture is the single largest producing sector of the economy since it comprises about 18.6% of the country's GDP and employs around 45% of the total labor force. The performance of this sector has an overwhelming impact on major macroeconomic indicators like employment generation, poverty alleviation, human resource development and food security. The agriculture sector is extremely vulnerable to disaster and climate induced risks. Climate change is anticipated to aggravate the frequency and intensity of extreme weather events in Bangladesh. Drought is one of the major setbacks for the agriculture and its development. Therefore, disaster and climatic risk, especially drought management in agriculture is a major challenge for Bangladesh in achieving sustainable agricultural development. There are some regions in Bangladesh where every steps of agriculture from field preparation to ripening of crops dependents on rainfall. Consequently, drought affects annually 2.5 million ha in kharif (wet season and 1.2 million ha in dry season. Water is a natural resource with spatial scarcity and availability. Additionally, Cross-country anthropogenic activities caused a severe negative impact on water resources and eco-systems of Bangladesh in the recent years. The rivers and cannels dry up during the dry season and make the people completely dependent on groundwater (Abdullah, 2015. Accordingly the contribution of groundwater as a source of irrigation has increased and surface water has declined. It is now inevitable to look for alternate water source for agriculture. Water harvest technologies (WHTs can play an important role in this regard. WHTs can provide an additional source of water for crop production at the most critical stages of the growing season, thereby increasing yields and food security. The study is consists of drought scenario analysis, GIS based drought mapping and systematic literature

Soil Selenium (Se) Biofortification Changes the Physiological, Biochemical and Epigenetic Responses to Water Stress in Zea mays L. by Inducing a Higher Drought Tolerance.

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Bocchini, Marika; D'Amato, Roberto; Ciancaleoni, Simona; Fontanella, Maria C; Palmerini, Carlo A; Beone, Gian M; Onofri, Andrea; Negri, Valeria; Marconi, Gianpiero; Albertini, Emidio; Businelli, Daniela

2018-01-01

plays a central role in biochemical adaptation to environmental stress. In conclusion, Se-biofortification could help maize plants to cope with drought stress conditions, by inducing a higher drought tolerance.

Soil Selenium (Se) Biofortification Changes the Physiological, Biochemical and Epigenetic Responses to Water Stress in Zea mays L. by Inducing a Higher Drought Tolerance

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Bocchini, Marika; D’Amato, Roberto; Ciancaleoni, Simona; Fontanella, Maria C.; Palmerini, Carlo A.; Beone, Gian M.; Onofri, Andrea; Negri, Valeria; Marconi, Gianpiero; Albertini, Emidio; Businelli, Daniela

2018-01-01

plays a central role in biochemical adaptation to environmental stress. In conclusion, Se-biofortification could help maize plants to cope with drought stress conditions, by inducing a higher drought tolerance. PMID:29636765

Soil Selenium (Se Biofortification Changes the Physiological, Biochemical and Epigenetic Responses to Water Stress in Zea mays L. by Inducing a Higher Drought Tolerance

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Marika Bocchini

2018-03-01

activity plays a central role in biochemical adaptation to environmental stress. In conclusion, Se-biofortification could help maize plants to cope with drought stress conditions, by inducing a higher drought tolerance.

Identifying the role of human-induced land-use change while assessing drought effects on groundwater recharge

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Verbeiren, Boud; Weerasinghe, Imeshi; Vanderhaegen, Sven; Canters, Frank; Uljee, Inge; Engelen, Guy; Jacquemin, Ingrid; Tychon, Bernard; Vangelis, Harris; Tsakiris, George; Batelaan, Okke; Huysmans, Marijke

2015-04-01

Drought is mainly regarded as a purely natural phenomenon, driven by the natural variation in precipitation or rather the lack of precipitation. Nowadays many river catchments are, however, altered by human activities having direct effects on the catchment landscape and hydrological response. In case of the occurrence of drought events in those catchments it becomes more complex to determine the effects of drought. To what extent is the hydrological response a direct result of the natural phenomenon and what is the role of the human factor? In this study we focus on the effects of droughts on groundwater recharge. Reliable estimation of groundwater recharge in space and time is of utmost importance for sustainable management of groundwater resources. Groundwater recharge forms the main source for replenishing aquifers. The main factors influencing groundwater recharge are the soil and topographic characteristics, land use and climate. While the first two influencing factors are relatively static, the latter two are (highly) dynamic. Differentiating between the contributions of each of these influencing factors to groundwater recharge is a challenging but important task. On the one hand, the occurrence of meteorological drought events is likely to cause direct, potentially deteriorating, effects on groundwater recharge. On the other hand, this is also the case for on-going land-use dynamics such as extensive urbanisation. The presented methodology aims at distinguishing in space and time between climate (drought-related) and land-use (human-induced) effects, enabling to assess the effects of drought on groundwater recharge. The physically-based water balance model WetSpass is used to calculate groundwater recharge in a distributed way (space and time) for the Dijle-Demer catchments in Belgium. The key issue is to determine land-use dynamics in a consistent way. A land-use timeseries is build based on four base maps. Via a change trajectory analysis the consistency

ASSESSING URBAN DROUGHTS IN A SMART CITY FRAMEWORK

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R. Obringer

2016-06-01

Full Text Available This study aims to integrate environmental data for drought monitoring to reduce uncertainty in urban drought characterization as part of the smart city framework. Currently, drought monitoring in urban areas is a challenge. This is due, in part, to a lack of knowledge on the subject of urban droughts and urban drought vulnerability. A critical part to assessing urban drought and implementing the necessary policies is determining drought conditions. Often the timing and severity of the drought can leave cities to enforce water restrictions, so accuracy of this determination has socioeconomic implications. To determine drought conditions, we need to know the water balance over the urban landscape, of which evapotranspiration (ET is a key variable. However, ET data and models have high uncertainty when compared to other hydrological variables (i.e., precipitation. This is largely due to ill-defined empirical models for characterizing the urban surface resistance parameter (rs that is used in ET calculations. We propose a method to estimate rs values using a combination of the Surface Temperature Initiated Closure (STIC method that calculates regional evapotranspiration data and an inverted version of the Penman-Monteith equation. We use this approach across the region surrounding Indianapolis, IN (USA from 2010-2014. We discuss the potential for this method to be integrated in to smart city framework to improve urban drought assessment.

Drought definitions and processes: how do humans fit in?

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Van Loon, Anne; Van Lanen, Henny; Gleeson, Tom

2015-04-01

Drought is commonly defined as a temporary lack of water compared to normal conditions. In the traditional definition used in the natural sciences (climate science, hydrology, earth science) only natural drivers are included and the human effect on water resources is excluded. Drought impact studies, however, using observed crop yields, wildfire data, reservoir information, etc., can hardy make this division. The interdisciplinarity of drought asks for a broader definition that considers the interplay between the hazard, impacts and management. In flood research, human effects on the volume and timing of the flood event are traditionally taken into account and there is the awareness that human factors like channel modification, land surface changes and water supply engineering can both intensify and reduce flooding. Drought researchers can learn from the flooding community and try to elucidate the effects of human factors on drought duration and severity. This is not only a necessary step to answer relevant societal questions in the anthropocene, but also the IAHS Panta Rhei initiative urges hydrologists to include the connection with human systems. We propose a paradigm shift in the definition of drought, namely to expand it to include the effects of human action. Here, we will present a conceptual diagram that will do justice to the interdisciplinarity of drought. We will discuss the complex interconnected system of climate - hydrology - society - ecosystem and which processes in that system are most relevant to take into consideration when studying drought. The revised definition provides recognition and a common ground to researchers in all fields of research and is better aligned with drought impacts and with stakeholders' and policy maker's views on drought. We will also go into some of the pitfalls and challenges that come with applying this revised definition. For example, the natural and human-induced processes related to drought can have different scales

Tree mortality predicted from drought-induced vascular damage

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Anderegg, William R.L.; Flint, Alan L.; Huang, Cho-ying; Flint, Lorraine E.; Berry, Joseph A.; Davis, Frank W.; Sperry, John S.; Field, Christopher B.

2015-01-01

The projected responses of forest ecosystems to warming and drying associated with twenty-first-century climate change vary widely from resiliency to widespread tree mortality1, 2, 3. Current vegetation models lack the ability to account for mortality of overstorey trees during extreme drought owing to uncertainties in mechanisms and thresholds causing mortality4, 5. Here we assess the causes of tree mortality, using field measurements of branch hydraulic conductivity during ongoing mortality in Populus tremuloides in the southwestern United States and a detailed plant hydraulics model. We identify a lethal plant water stress threshold that corresponds with a loss of vascular transport capacity from air entry into the xylem. We then use this hydraulic-based threshold to simulate forest dieback during historical drought, and compare predictions against three independent mortality data sets. The hydraulic threshold predicted with 75% accuracy regional patterns of tree mortality as found in field plots and mortality maps derived from Landsat imagery. In a high-emissions scenario, climate models project that drought stress will exceed the observed mortality threshold in the southwestern United States by the 2050s. Our approach provides a powerful and tractable way of incorporating tree mortality into vegetation models to resolve uncertainty over the fate of forest ecosystems in a changing climate.

Drought-induced changes in Amazon forest structure from repeat airborne lidar

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Morton, D. C.; Leitold, V.; Longo, M.; Keller, M.; dos-Santos, M. N.; Scaranello, M. A., Sr.

2017-12-01

Drought events in tropical forests, including the 2015-2016 El Niño, may reduce net primary productivity and increase canopy tree mortality, thereby altering the short and long-term net carbon balance of tropical forests. Given the broad extent of drought impacts, forest inventory plots or eddy flux towers may not capture regional variability in forest response to drought. Here, we analyzed repeat airborne lidar data to evaluate canopy turnover from branch and tree fall before (2013-2014) and during (2014-2016) the recent El Niño drought in the eastern and central Brazilian Amazon. Coincident field surveys for a 16-ha subset of the lidar coverage provided complementary information to classify turnover areas by mechanism (branch, multiple branch, tree fall, multiple tree fall) and estimate the total coarse woody debris volume from canopy and understory tree mortality. Annualized rates of canopy turnover increased by 50%, on average, during the drought period in both intact and fragmented forests near Santarém, Pará. Turnover increased uniformly across all size classes, and there was limited evidence that taller trees contributed a greater proportion of turnover events in any size class in 2014-2016 compared to 2013-2014. This short-term increase in canopy turnover differs from findings in multi-year rainfall exclusion experiments that large trees were more sensitive to drought impacts. Field measurements confirmed the separability of the smallest (single branch) and largest damage classes (multiple tree falls), but single tree and multiple branch fall events generated similar coarse woody debris production and lidar-derived changes in canopy volume. Large-scale sampling possible with repeat airborne lidar data also captured strong local and regional gradients in canopy turnover. Differences in slope partially explained the north-south gradient in canopy turnover dynamics near Santarém, with larger increases in turnover on flatter terrain. Regional variability

The roles of reactive oxygen metabolism in drought: not so cut and dried.

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Noctor, Graham; Mhamdi, Amna; Foyer, Christine H

2014-04-01

Drought is considered to cause oxidative stress, but the roles of oxidant-induced modifications in plant responses to water deficit remain obscure. Key unknowns are the roles of reactive oxygen species (ROS) produced at specific intracellular or apoplastic sites and the interactions between the complex, networking antioxidative systems in restricting ROS accumulation or in redox signal transmission. This Update discusses the physiological aspects of ROS production during drought, and analyzes the relationship between oxidative stress and drought from different but complementary perspectives. We ask to what extent redox changes are involved in plant drought responses and discuss the roles that different ROS-generating processes may play. Our discussion emphasizes the complexity and the specificity of antioxidant systems, and the likely importance of thiol systems in drought-induced redox signaling. We identify candidate drought-responsive redox-associated genes and analyze the potential importance of different metabolic pathways in drought-associated oxidative stress signaling.

Green Leaf Volatile Emissions during High Temperature and Drought Stress in a Central Amazon Rainforest.

Science.gov (United States)

Jardine, Kolby J; Chambers, Jeffrey Q; Holm, Jennifer; Jardine, Angela B; Fontes, Clarissa G; Zorzanelli, Raquel F; Meyers, Kimberly T; de Souza, Vinicius Fernadez; Garcia, Sabrina; Gimenez, Bruno O; Piva, Luani R de O; Higuchi, Niro; Artaxo, Paulo; Martin, Scot; Manzi, Antônio O

2015-09-15

Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C₅ and C₆ GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C₆ GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress.

Effects of biotic and abiotic factors on resistance versus resilience of Douglas fir to drought.

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Gunnar Carnwath

Full Text Available Significant increases in tree mortality due to drought-induced physiological stress have been documented worldwide. This trend is likely to continue with increased frequency and severity of extreme drought events in the future. Therefore, understanding the factors that influence variability in drought responses among trees will be critical to predicting ecosystem responses to climate change and developing effective management actions. In this study, we used hierarchical mixed-effects models to analyze drought responses of Pseudotsuga menziesii in 20 unmanaged forests stands across a broad range of environmental conditions in northeastern Washington, USA. We aimed to 1 identify the biotic and abiotic attributes most closely associated with the responses of individual trees to drought and 2 quantify the variability in drought responses at different spatial scales. We found that growth rates and competition for resources significantly affected resistance to a severe drought event in 2001: slow-growing trees and trees growing in subordinate canopy positions and/or with more neighbors suffered greater declines in radial growth during the drought event. In contrast, the ability of a tree to return to normal growth when climatic conditions improved (resilience was unaffected by competition or relative growth rates. Drought responses were significantly influenced by tree age: older trees were more resistant but less resilient than younger trees. Finally, we found differences between resistance and resilience in spatial scale: a significant proportion (approximately 50% of the variability in drought resistance across the study area was at broad spatial scales (i.e. among different forest types, most likely due to differences in the total amount of precipitation received at different elevations; in contrast, variation in resilience was overwhelmingly (82% at the level of individual trees within stands and there was no difference in drought resilience

Germinaton performance of selected local soybean (Glycine max (L.) Merrills) cultivars during drought stress induced by Polyethylene Glycol (PEG)

Science.gov (United States)

Pane, R. F.; Damanik, R. I.; Khardinata, E. H.

2018-02-01

Drought stress is one of the factors that can decreased growth and production, so that required a variety that has the ability to sustain cellular metabolism, and growth during the stress. This research was aimed to investigated the involvement of germination performance invitro of five local soybean cultivars, Grobogan, Kaba, Anjasmoro, Argomulyo, and Dering to drought stress induced by polyethylene glycol (PEG) 6000 (0%, 2%, 4%, and 6%). The measurable seedling traits as the day appearance of shoots and roots, total of leaves, shoot length, root length, fresh plant weight, dry plant weight, fresh root weight, and dry root weight under control as well as water stress condition were recorded. The experiment units were arranged in factorial completely randomized design with four replications. The result showed that the value for most parameters was recorded highest for Argomulyo cultivar compared with Dering cultivar which is known to be tolerant to drought. In terms of roots performance, Grobogan and Argomulyo cultivars produced the longest and heaviest of roots, while Grobogan cultivar had no significant different for root length compared with control. In conclusion, the root length and fresh weight root parameters can be used as quick criteria for drought tolerance.

Physiological and photosynthetic response of quinoa to drought stress

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Rachid Fghire

2015-06-01

Full Text Available Water shortage is a critical problem touching plant growth and yield in semi-arid areas, for instance the Mediterranean región. For this reason was studied the physiological basis of drought tolerance of a new, drought tolerant crop quinoa (Chenopodium quinoa Willd. tested in Morocco in two successive seasons, subject to four irrigation treatments (100, 50, and 33%ETc, and rainfed. The chlorophyll a fluorescence transients were analyzed by the JIP-test to transíate stress-induced damage in these transients to changes in biophysical parameter's allowing quantification of the energy flow through the photosynthetic apparatus. Drought stress induced a significant decrease in the maximum quantum yield of primary photochemistry (Φpo = Fv/Fm, and the quantum yield of electron transport (Φeo. The amount of active Photosystem II (PSII reaction centers (RC per excited cross section (RC/CS also decreased when exposed to the highest drought stress. The effective antenna size of active RCs (ABS/RC increased and the effective dissipation per active reaction centers (DIo/RC increased by increasing drought stress during the growth season in comparison to the control. However the performance index (PI, was a very sensitive indicator of the physiological status of plants. Leaf area index, leaf water potential and stomatal conductance decreased as the drought increased. These results indicate that, in quinoa leaf, JIP-test can be used as a sensitive method for measuring drought stress effects.

Gene expression analysis of Solanum lycopersicum and Solanum habrochaites under drought conditions

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Upama Mishra

2016-09-01

Full Text Available Drought is one of the limiting environmental factors that affect crop production worldwide. Understanding the molecular mechanism of drought stress is the key to developing drought tolerant crop. In this experiment we performed expression profiling of tomato plants under water deficit conditions using microarray technology. The data set we generated (available in the NCBI/GEO database under GSE22304 has been analyzed to identify genes that are involved in the regulation of tomato's responses to drought.

Genetic variation of drought tolerance in Pinus pinaster at three hierarchical levels: a comparison of induced osmotic stress and field testing.

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Gaspar, Maria João; Velasco, Tania; Feito, Isabel; Alía, Ricardo; Majada, Juan

2013-01-01

Understanding the survival capacity of forest trees to periods of severe water stress could improve knowledge of the adaptive potential of different species under future climatic scenarios. In long lived organisms, like forest trees, the combination of induced osmotic stress treatments and field testing can elucidate the role of drought tolerance during the early stages of establishment, the most critical in the life of the species. We performed a Polyethylene glycol-osmotic induced stress experiment and evaluated two common garden experiments (xeric and mesic sites) to test for survival and growth of a wide range clonal collection of Maritime pine. This study demonstrates the importance of additive vs non additive effects for drought tolerance traits in Pinus pinaster, and shows differences in parameters determining the adaptive trajectories of populations and family and clones within populations. The results show that osmotic adjustment plays an important role in population variation, while biomass allocation and hydric content greatly influence survival at population level. Survival in the induced osmotic stress experiment presented significant correlations with survival in the xeric site, and height growth at the mesic site, at population level, indicating constraints of adaptation for those traits, while at the within population level no significant correlation existed. These results demonstrate that population differentiation and within population genetic variation for drought tolerance follow different patterns.

Genetic variation of drought tolerance in Pinus pinaster at three hierarchical levels: a comparison of induced osmotic stress and field testing.

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Maria João Gaspar

Full Text Available Understanding the survival capacity of forest trees to periods of severe water stress could improve knowledge of the adaptive potential of different species under future climatic scenarios. In long lived organisms, like forest trees, the combination of induced osmotic stress treatments and field testing can elucidate the role of drought tolerance during the early stages of establishment, the most critical in the life of the species. We performed a Polyethylene glycol-osmotic induced stress experiment and evaluated two common garden experiments (xeric and mesic sites to test for survival and growth of a wide range clonal collection of Maritime pine. This study demonstrates the importance of additive vs non additive effects for drought tolerance traits in Pinus pinaster, and shows differences in parameters determining the adaptive trajectories of populations and family and clones within populations. The results show that osmotic adjustment plays an important role in population variation, while biomass allocation and hydric content greatly influence survival at population level. Survival in the induced osmotic stress experiment presented significant correlations with survival in the xeric site, and height growth at the mesic site, at population level, indicating constraints of adaptation for those traits, while at the within population level no significant correlation existed. These results demonstrate that population differentiation and within population genetic variation for drought tolerance follow different patterns.

Plasticity and stress tolerance override local adaptation in the responses of Mediterranean holm oak seedlings to drought and cold.

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Gimeno, Teresa E; Pías, Beatriz; Lemos-Filho, José P; Valladares, Fernando

2009-01-01

Plant populations of widely distributed species experience a broad range of environmental conditions that can be faced by phenotypic plasticity or ecotypic differentiation and local adaptation. The strategy chosen will determine a population's ability to respond to climate change. To explore this, we grew Quercus ilex (L.) seedlings from acorns collected at six selected populations from climatically contrasting localities and evaluated their response to drought and late season cold events. Maximum photosynthetic rate (A(max)), instantaneous water use efficiency (iWUE), and thermal tolerance to freeze and heat (estimated from chlorophyll fluorescence versus temperature curves) were measured in 5-month-old seedlings in control (no stress), drought (water-stressed), and cold (low suboptimal temperature) conditions. The observed responses were similar for the six populations: drought decreased A(max) and increased iWUE, and cold reduced A(max) and iWUE. All the seedlings maintained photosynthetic activity under adverse conditions (drought and cold), and rapidly increased their iWUE by closing stomata when exposed to drought. Heat and freeze tolerances were similarly high for seedlings from all the populations, and they were significantly increased by drought and cold, respectively; and were positively related to each other. Differences in seedling performance across populations were primarily induced by maternal effects mediated by seed size and to a lesser extent by idiosyncratic physiologic responses to drought and low temperatures. Tolerance to multiple stresses together with the capacity to physiologically acclimate to heat waves and cold snaps may allow Q. ilex to cope with the increasingly stressful conditions imposed by climate change. Lack of evidence of physiologic seedling adaptation to local climate may reflect opposing selection pressures to complex, multidimensional environmental conditions operating within the distribution range of this species.

Systemic and intensifying drought induces collapse and replacement of native fishes: a time-series approach

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Ruhi, A.; Olden, J. D.; Sabo, J. L.

2015-12-01

In the American Southwest, hydrologic drought has become a new normal as a result of increasing human appropriation of freshwater resources and increased aridity associated with global warming. Although drought has often been touted to threaten freshwater biodiversity, connecting drought to extinction risk of highly-imperiled faunas remains a challenge. Here we combine time-series methods from signal processing and econometrics to analyze a spatially comprehensive and long-term dataset to link discharge variation and community abundance of fish across the American Southwest. This novel time series framework identifies ongoing trends in daily discharge anomalies across the Southwest, quantifies the effect of the historical hydrologic drivers on fish community abundance, and allows us to simulate species trajectories and range-wide risk of decline (quasiextinction) under scenarios of future climate. Spectral anomalies are declining over the last 30 years in at least a quarter of the stream gaging stations across the American Southwest and these anomalies are robust predictors of historical abundance of native and non-native fishes. Quasiextinction probabilities are high (>50 %) for nearly ¾ of the native species across several large river basins in the same region; and the negative trend in annual anomalies increases quasiextinction risk for native but reduces this risk for non-native fishes. These findings suggest that ongoing drought is causing range-wide collapse and replacement of native fish faunas, and that this homogenization of western fish faunas will continue given the prevailing negative trend in discharge anomalies. Additionally, this combination of methods can be applied elsewhere as long as environmental and biological long-term time-series data are available. Collectively, these methods allow identifying the link between hydroclimatic forcing and ecological responses and thus may help anticipating the potential impacts of ongoing and future hydrologic

Association of candidate genes with drought tolerance traits in diverse perennial ryegrass accessions

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Xiaoqing Yu; Guihua Bai; Shuwei Liu; Na Luo; Ying Wang; Douglas S. Richmond; Paula M. Pijut; Scott A. Jackson; Jianming Yu; Yiwei. Jiang

2013-01-01

Drought is a major environmental stress limiting growth of perennial grasses in temperate regions. Plant drought tolerance is a complex trait that is controlled by multiple genes. Candidate gene association mapping provides a powerful tool for dissection of complex traits. Candidate gene association mapping of drought tolerance traits was conducted in 192 diverse...

For a Limited Time Only? How Long Can Trees Maintain Enhanced Chemical Defenses During Pre-Mortality Heat and Drought Stress

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Trowbridge, A.; Adams, H. D.; Cook, A. A.; Hofland, M.; Weaver, D.; McDowell, N. G.

2016-12-01

The relative contribution of forest pests to climate and drought-induced tree mortality is complex and largely absent from current process-based models. Recent efforts have focused on developing frameworks to integrate insects into models of tree mortality, citing the need for a better mechanistic understanding of the links between stress-induced tree physiology and insect behavior and population dynamics. Secondary plant metabolites (SPMs) play a critical role in plant resistance and their synthesis and mobilization are coupled to carbon assimilation, hydraulic conductivity, and herbivory itself. Insect host choice also depends in part on behavioral responses to host SPMs. Monoterpenes are the dominant SPMs in conifers, and while high concentrations of monoterpenes are toxic to bark beetles, lower concentrations serve as precursors for a number of aggregation pheromones. Thus, the impact of monoterpenes on bark beetle behavior is complex and is impacted by environmental effects on primary metabolism including heat and drought stress. Here, we quantify the dynamics of piñon pine monoterpene chemistry as a function of predicted and prolonged drought stress implemented at the SUrvival MOrtality (SUMO) experimental site at the Los Alamos National Laboratory, NM, USA. In both woody and needle tissues, total monoterpene concentrations in ambient trees were not significantly different from those observed in trees exposed to heat stress, but drought trees showed higher total concentration while heat+drought trees were observed to have the highest levels (2 fold increase over ambient). These treatment effects were sustained over a two-year period despite seasonal variation in tree water status; however, total concentration in the xylem and phloem were closely coupled to tree water potential and treatment effects took longer to manifest relative to the needles. Individual compounds responded differently to the treatments, suggesting cyclase-level enzyme regulation, while �

Drought Stress Results in a Compartment-Specific Restructuring of the Rice Root-Associated Microbiomes

Directory of Open Access Journals (Sweden)

Christian Santos-Medellín

2017-07-01

Full Text Available Plant roots support complex microbial communities that can influence plant growth, nutrition, and health. While extensive characterizations of the composition and spatial compartmentalization of these communities have been performed in different plant species, there is relatively little known about the impact of abiotic stresses on the root microbiota. Here, we have used rice as a model to explore the responses of root microbiomes to drought stress. Using four distinct genotypes, grown in soils from three different fields, we tracked the drought-induced changes in microbial composition in the rhizosphere (the soil immediately surrounding the root, the endosphere (the root interior, and unplanted soils. Drought significantly altered the overall bacterial and fungal compositions of all three communities, with the endosphere and rhizosphere compartments showing the greatest divergence from well-watered controls. The overall response of the bacterial microbiota to drought stress was taxonomically consistent across soils and cultivars and was primarily driven by an enrichment of multiple Actinobacteria and Chloroflexi, as well as a depletion of several Acidobacteria and Deltaproteobacteria. While there was some overlap in the changes observed in the rhizosphere and endosphere communities, several drought-responsive taxa were compartment specific, a pattern likely arising from preexisting compositional differences, as well as plant-mediated processes affecting individual compartments. These results reveal that drought stress, in addition to its well-characterized effects on plant physiology, also results in restructuring of root microbial communities and suggest the possibility that constituents of the altered plant microbiota might contribute to plant survival under extreme environmental conditions.

Experimental Warming Aggravates Degradation-Induced Topsoil Drought in Alpine Meadows of The Qinghai-Tibetan Plateau

Science.gov (United States)

Xue, X.

2017-12-01

Climatic warming is presumed to cause topsoil drought by increasing evapotranspiration and water infiltration, and by progressively inducing land degradation in alpine meadows of the Qinghai-Tibetan Plateau. However, how soil moisture and temperature patterns of degraded alpine meadows respond to climate warming remains unclear. A six-year continuous warming experiment was carried out in both degraded and undegraded alpine meadows in the source region of the Yangtze River. The goal was to identify the effects of climatic warming and land degradation on soil moisture (θ), soil surface temperature (Tsfc), and soil temperature (Ts). In the present study, land degradation significantly reduced θ by 4.5-6.1% at a depth of 0-100 cm (P soil surface. Experimental warming aggravated topsoil drought caused by land degradation, intensified the magnitude of degradation, and caused a positive feedback in the degraded alpine meadow ecosystem. Therefore, an immediate need exists to restore degraded alpine meadow grasslands in the Qinghai-Tibetan Plateau in anticipation of a warmer future.

Remotely sensed predictors of conifer tree mortality during severe drought

Science.gov (United States)

Brodrick, P. G.; Asner, G. P.

2017-11-01

Widespread, drought-induced forest mortality has been documented on every forested continent over the last two decades, yet early pre-mortality indicators of tree death remain poorly understood. Remotely sensed physiological-based measures offer a means for large-scale analysis to understand and predict drought-induced mortality. Here, we use laser-guided imaging spectroscopy from multiple years of aerial surveys to assess the impact of sustained canopy water loss on tree mortality. We analyze both gross canopy mortality in 2016 and the change in mortality between 2015 and 2016 in millions of sampled conifer forest locations throughout the Sierra Nevada mountains in California. On average, sustained water loss and gross mortality are strongly related, and year-to-year water loss within the drought indicates subsequent mortality. Both relationships are consistent after controlling for location and tree community composition, suggesting that these metrics may serve as indicators of mortality during a drought.

Losing the Warning Signal: Drought Compromises the Cross-Talk of Signaling Molecules in Quercus ilex Exposed to Ozone

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Lorenzo Cotrozzi

2017-06-01

Full Text Available Understanding the interactions between drought and acute ozone (O3 stress in terms of signaling molecules and cell death would improve the predictions of plant responses to climate change. The aim was to investigate whether drought stress influences the responses of plants to acute episodes of O3 exposure. In this study, the behavior of 84 Mediterranean evergreen Quercus ilex plants was evaluated in terms of cross-talk responses among signaling molecules. Half of the sample was subjected to drought (20% of the effective daily evapotranspiration, for 15 days and was later exposed to an acute O3 exposure (200 nL L-1 for 5 h. First, our results indicate that in well-water conditions, O3 induced a signaling pathway specific to O3-sensitive behavior. Second, different trends and consequently different roles of phytohormones and signaling molecules (ethylene, ET; abscisic acid, ABA; salycilic acid, SA and jasmonic acid, JA were observed in relation to water stress and O3. A spatial and functional correlation between these signaling molecules was observed in modulating O3-induced responses in well-watered plants. In contrast, in drought-stressed plants, these compounds were not involved either in O3-induced signaling mechanisms or in leaf senescence (a response observed in water-stressed plants before the O3-exposure. Third, these differences were ascribable to the fact that in drought conditions, most defense processes induced by O3 were compromised and/or altered. Our results highlight how Q. ilex plants suffering from water deprivation respond differently to an acute O3 episode compared to well-watered plants, and suggest new effect to be considered in plant responses to environmental changes. This poses the serious question as to whether or not multiple high-magnitude O3 events (as predicted can change these cross-talk responses, thus opening it up possible further investigations.

Analysis of natural variation in bermudagrass (Cynodon dactylon) reveals physiological responses underlying drought tolerance.

Science.gov (United States)

Shi, Haitao; Wang, Yanping; Cheng, Zhangmin; Ye, Tiantian; Chan, Zhulong

2012-01-01

Bermudagrass (Cynodon dactylon) is a widely used warm-season turfgrass and one of the most drought tolerant species. Dissecting the natural variation in drought tolerance and physiological responses will bring us powerful basis and novel insight for plant breeding. In the present study, we evaluated the natural variation of drought tolerance among nine bermudagrass varieties by measuring physiological responses after drought stress treatment through withholding water. Three groups differing in drought tolerance were identified, including two tolerant, five moderately tolerant and two susceptible varieties. Under drought stress condition, drought sensitive variety (Yukon) showed relative higher water loss, more severe cell membrane damage (EL), and more accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), while drought tolerant variety (Tifgreen) exhibited significantly higher antioxidant enzymes activities. Further results indicated that drought induced cell injury in different varieties (Yukon, SR9554 and Tifgreen) exhibited liner correlation with leaf water content (LWC), H₂O₂ content, MDA content and antioxidant enzyme activities. Additionally, Tifgreen plants had significantly higher levels of osmolytes (proline level and soluble sugars) when compared with Yukon and SR9554 under drought stress condition. Taken together, our results indicated that natural variation of drought stress tolerance in bermudagrass varieties might be largely related to the induced changes of water status, osmolyte accumulation and antioxidant defense system.

75 FR 19989 - Final Environmental Impact Statement for Drought Management Planning at the Kerr Hydroelectric...

Science.gov (United States)

2010-04-16

... Drought Management Planning at the Kerr Hydroelectric Project, Flathead Lake, MT AGENCY: Bureau of Indian... Impact Statement (FEIS) for Drought Management Planning at the Kerr Hydroelectric Project, Flathead Lake... drought management planning at the Kerr Hydroelectric Project no sooner than 30 days following the...

Isoprene emission response to drought and the impact on global atmospheric chemistry

Science.gov (United States)

Jiang, Xiaoyan; Guenther, Alex; Potosnak, Mark; Geron, Chris; Seco, Roger; Karl, Thomas; Kim, Saewung; Gu, Lianhong; Pallardy, Stephen

2018-06-01

Biogenic isoprene emissions play a very important role in atmospheric chemistry. These emissions are strongly dependent on various environmental conditions, such as temperature, solar radiation, plant water stress, ambient ozone and CO2 concentrations, and soil moisture. Current biogenic emission models (i.e., Model of Emissions of Gases and Aerosols from Nature, MEGAN) can simulate emission responses to some of the major driving variables, such as short-term variations in temperature and solar radiation, but the other factors are either missing or poorly represented. In this paper, we propose a new modelling approach that considers the physiological effects of drought stress on plant photosynthesis and isoprene emissions for use in the MEGAN3 biogenic emission model. We test the MEGAN3 approach by integrating the algorithm into the existing MEGAN2.1 biogenic emission model framework embedded into the global Community Land Model of the Community Earth System Model (CLM4.5/CESM1.2). Single-point simulations are compared against available field measurements at the Missouri Ozarks AmeriFlux (MOFLUX) field site. The modelling results show that the MEGAN3 approach of using of a photosynthesis parameter (Vcmax) and soil wetness factor (βt) to determine the drought activity factor leads to better simulated isoprene emissions in non-drought and drought periods. The global simulation with the MEGAN3 approach predicts a 17% reduction in global annual isoprene emissions, in comparison to the value predicted using the default CLM4.5/MEGAN2.1 without any drought effect. This reduction leads to changes in surface ozone and oxidants in the areas where the reduction of isoprene emissions is observed. Based on the results presented in this study, we conclude that it is important to simulate the drought-induced response of biogenic isoprene emission accurately in the coupled Earth System model.

Drought impacts on cereal yields in Iberia

Science.gov (United States)

Gouveia, Célia; Liberato, Margarida L. R.; Russo, Ana; Montero, Irene

2014-05-01

In the present context of climate change, land degradation and desertification it becomes crucial to assess the impact of droughts to determine the environmental consequences of a potential change of climate. Large drought episodes in Iberian Peninsula have widespread ecological and environmental impacts, namely in vegetation dynamics, resulting in significant crop yield losses. During the hydrological years of 2004/2005 and 2011/2012 Iberia was affected by two extreme drought episodes (Garcia-Herrera et al., 2007; Trigo et al., 2013). This work aims to analyze the spatial and temporal behavior of climatic droughts at different time scales using spatially distributed time series of drought indicators, such as the Standardized Precipitation Evapotranspiration Index (SPEI) (Vicente-Serrano et al., 2010). This climatic drought index is based on the simultaneous use of precipitation and temperature. We have used CRU TS3 dataset to compute SPEI and the Standardized Precipitation Index (SPI). Results will be analyzed in terms of the mechanisms that are responsible by these drought events and will also be used to assess the impact of droughts in crops. Accordingly an analysis is performed to evaluate the large-scale conditions required for a particular extreme anomaly of long-range transport of water vapor from the subtropics. We have used the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA Interim reanalyses, namely, the geopotential height fields, temperature, wind, divergence data and the specific humidity at all pressure levels and mean sea level pressure (MSLP) and total column water vapor (TCWV) for the Euro-Atlantic sector (100°W to 50°E, 0°N-70°N) at full temporal (six hourly) and spatial (T255; interpolated to 0.75° regular horizontal grid) resolutions available to analyse the large-scale conditions associated with the drought onset. Our analysis revealed severe impacts on cereals crop productions and yield (namely wheat) for Portugal and

A Global Drought Observatory for Emergency Response

Science.gov (United States)

Vogt, Jürgen; de Jager, Alfred; Carrão, Hugo; Magni, Diego; Mazzeschi, Marco; Barbosa, Paulo

2016-04-01

Droughts are occurring on all continents and across all climates. While in developed countries they cause significant economic and environmental damages, in less developed countries they may cause major humanitarian catastrophes. The magnitude of the problem and the expected increase in drought frequency, extent and severity in many, often highly vulnerable regions of the world demand a change from the current reactive, crisis-management approach towards a more pro-active, risk management approach. Such approach needs adequate and timely information from global to local scales as well as adequate drought management plans. Drought information systems are important for continuous monitoring and forecasting of the situation in order to provide timely information on developing drought events and their potential impacts. Against this background, the Joint Research Centre (JRC) is developing a Global Drought Observatory (GDO) for the European Commission's humanitarian services, providing up-to-date information on droughts world-wide and their potential impacts. Drought monitoring is achieved by a combination of meteorological and biophysical indicators, while the societal vulnerability to droughts is assessed through the targeted analysis of a series of social, economic and infrastructural indicators. The combination of the information on the occurrence and severity of a drought, on the assets at risk and on the societal vulnerability in the drought affected areas results in a likelihood of impact, which is expressed by a Likelihood of Drought Impact (LDI) indicator. The location, extent and magnitude of the LDI is then further analyzed against the number of people and land use/land cover types affected in order to provide the decision bodies with information on the potential humanitarian and economic bearings in the affected countries or regions. All information is presented through web-mapping interfaces based on OGC standards and customized reports can be drawn by the

Nonstructural leaf carbohydrate dynamics of Pinus edulis during drought-induced tree mortality reveal role for carbon metabolism in mortality mechanism.

Science.gov (United States)

Adams, Henry D; Germino, Matthew J; Breshears, David D; Barron-Gafford, Greg A; Guardiola-Claramonte, Maite; Zou, Chris B; Huxman, Travis E

2013-03-01

Vegetation change is expected with global climate change, potentially altering ecosystem function and climate feedbacks. However, causes of plant mortality, which are central to vegetation change, are understudied, and physiological mechanisms remain unclear, particularly the roles of carbon metabolism and xylem function. We report analysis of foliar nonstructural carbohydrates (NSCs) and associated physiology from a previous experiment where earlier drought-induced mortality of Pinus edulis at elevated temperatures was associated with greater cumulative respiration. Here, we predicted faster NSC decline for warmed trees than for ambient-temperature trees. Foliar NSC in droughted trees declined by 30% through mortality and was lower than in watered controls. NSC decline resulted primarily from decreased sugar concentrations. Starch initially declined, and then increased above pre-drought concentrations before mortality. Although temperature did not affect NSC and sugar, starch concentrations ceased declining and increased earlier with higher temperatures. Reduced foliar NSC during lethal drought indicates a carbon metabolism role in mortality mechanism. Although carbohydrates were not completely exhausted at mortality, temperature differences in starch accumulation timing suggest that carbon metabolism changes are associated with time to death. Drought mortality appears to be related to temperature-dependent carbon dynamics concurrent with increasing hydraulic stress in P. edulis and potentially other similar species. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Water Scarcity, Food Insecurity and Drought Induced Displacement in an Arid Ecosystem: A Case Study in Indian Desert

Science.gov (United States)

Rehman Siddiqui, Azizur

2017-04-01

Indian Arid Ecosystem is characterised by scare as well as seasonal precipitation that have led to long term stress in a fragile ecosystem. In addition to this, over the years, Indian desert has experienced varying magnitude of drought, which have considerably influenced food and fodder production and led to the depletion of surface and ground water table. All these factors mean that the production potential of land is hardly sufficient to feed human as well as livestock population of the desert and this has led to extensive rural to urban migration in Indian Desert. In the present study, satellite data from Landsat TM, AWiFS, NOAA AVHRR have been used to detect the intensity and severity of drought condition, and data collected through primary survey has been used to measure the impact of water scarcity on food insecurity and drought induced migration. Rainfall trend analysis of the study area has been done with the help of Man Kendall Method to assess the meteorological vulnerability. In addition to these, NDVI, VCI, TCI, and VHI have also been used to find out the long term vegetation health in the study area. With the help of these scientific techniques, the paper focuses on the moisture deficiency during growing period and its effect on human population and livestock population. Keywords: Arid Ecosystem, Indian Desert, Drought, Migration

Analysis of drought-tolerant sugar beet (Beta vulgaris L.) mutants induced with gamma radiation using SDS-PAGE and ISSR markers.

Science.gov (United States)

Sen, Ayse; Alikamanoglu, Sema

2012-01-01

Drought is one of the major environmental stresses which greatly affect the plant growth and productivity. In the present study, various doses (0-75Gy) of gamma rays were applied to investigate the effect of radiation on shoot tip explants. It was observed that the regeneration rates and plant fresh weights decreased significantly with an increase in radiation dose. The optimal irradiation doses for mutation induction were determined at 15 and 20Gy. Afterwards, the induction of somatic mutation in sugar beet (Beta vulgaris L.) was investigated by irradiation of shoot tips with 15 and 20Gy gamma rays. Irradiated shoot tips were sub-cultured and M(1)V(1)-M(1)V(3) generations were obtained. Mutants tolerant to drought stress were selected on MS medium, supplemented with 10 and 20gl(-1) PEG6000. Of the M(1)V(3) plantlets, drought-tolerant mutants were selected. Leaf soluble proteins obtained from the control and drought-tolerant mutants were analyzed by SDS-PAGE. A total of 22 protein bands were determined and 2 of them were observed to be drought-tolerant mutants except the control. Polymorphism was also detected among the control and drought-tolerant mutants by DNA fingerprinting using ISSR markers. A total of 106 PCR fragments were amplified with 19 ISSR primers and 91 of them were polymorphic. The dendrograms were separated into two main clusters. First cluster included M8 mutant plant, which was applied 20Gy gamma radiation and regenerated on selective culture media containing 10gl(-1) PEG6000 concentration, and the second cluster was further divided into five sub-clusters. Copyright © 2012 Elsevier B.V. All rights reserved.

Analysis of drought-tolerant sugar beet (Beta vulgaris L.) mutants induced with gamma radiation using SDS-PAGE and ISSR markers

International Nuclear Information System (INIS)

Sen, Ayse; Alikamanoglu, Sema

2012-01-01

Drought is one of the major environmental stresses which greatly affect the plant growth and productivity. In the present study, various doses (0–75 Gy) of gamma rays were applied to investigate the effect of radiation on shoot tip explants. It was observed that the regeneration rates and plant fresh weights decreased significantly with an increase in radiation dose. The optimal irradiation doses for mutation induction were determined at 15 and 20 Gy. Afterwards, the induction of somatic mutation in sugar beet (Beta vulgaris L.) was investigated by irradiation of shoot tips with 15 and 20 Gy gamma rays. Irradiated shoot tips were sub-cultured and M 1 V 1 –M 1 V 3 generations were obtained. Mutants tolerant to drought stress were selected on MS medium, supplemented with 10 and 20 gl −1 PEG6000. Of the M 1 V 3 plantlets, drought-tolerant mutants were selected. Leaf soluble proteins obtained from the control and drought-tolerant mutants were analyzed by SDS-PAGE. A total of 22 protein bands were determined and 2 of them were observed to be drought-tolerant mutants except the control. Polymorphism was also detected among the control and drought-tolerant mutants by DNA fingerprinting using ISSR markers. A total of 106 PCR fragments were amplified with 19 ISSR primers and 91 of them were polymorphic. The dendrograms were separated into two main clusters. First cluster included M8 mutant plant, which was applied 20 Gy gamma radiation and regenerated on selective culture media containing 10 g l −1 PEG6000 concentration, and the second cluster was further divided into five sub-clusters.

Analysis of drought-tolerant sugar beet (Beta vulgaris L.) mutants induced with gamma radiation using SDS-PAGE and ISSR markers

Energy Technology Data Exchange (ETDEWEB)

Sen, Ayse, E-mail: senayse@istanbul.edu.tr [Istanbul University, Faculty of Science, Department of Biology, 34459 Vezneciler, Istanbul (Turkey); Alikamanoglu, Sema [Istanbul University, Faculty of Science, Department of Biology, 34459 Vezneciler, Istanbul (Turkey)

2012-10-15

Drought is one of the major environmental stresses which greatly affect the plant growth and productivity. In the present study, various doses (0-75 Gy) of gamma rays were applied to investigate the effect of radiation on shoot tip explants. It was observed that the regeneration rates and plant fresh weights decreased significantly with an increase in radiation dose. The optimal irradiation doses for mutation induction were determined at 15 and 20 Gy. Afterwards, the induction of somatic mutation in sugar beet (Beta vulgaris L.) was investigated by irradiation of shoot tips with 15 and 20 Gy gamma rays. Irradiated shoot tips were sub-cultured and M{sub 1}V{sub 1}-M{sub 1}V{sub 3} generations were obtained. Mutants tolerant to drought stress were selected on MS medium, supplemented with 10 and 20 gl{sup -1} PEG6000. Of the M{sub 1}V{sub 3} plantlets, drought-tolerant mutants were selected. Leaf soluble proteins obtained from the control and drought-tolerant mutants were analyzed by SDS-PAGE. A total of 22 protein bands were determined and 2 of them were observed to be drought-tolerant mutants except the control. Polymorphism was also detected among the control and drought-tolerant mutants by DNA fingerprinting using ISSR markers. A total of 106 PCR fragments were amplified with 19 ISSR primers and 91 of them were polymorphic. The dendrograms were separated into two main clusters. First cluster included M8 mutant plant, which was applied 20 Gy gamma radiation and regenerated on selective culture media containing 10 g l{sup -1} PEG6000 concentration, and the second cluster was further divided into five sub-clusters.

ThPOD3, a truncated polypeptide from Tamarix hispida, conferred drought tolerance in Escherichia coli.

Science.gov (United States)

Guo, Xiao-Hong; Jiang, Jing; Wang, Bai-Chen; Li, Hui-Yu; Wang, Yu-Cheng; Yang, Chuan-Ping; Liu, Gui-Feng

2010-03-01

The ThPOD1 gene encodes a peroxidase and was isolated from a Tamarix hispida NaCl-stress root cDNA library. We found that ThPOD1 expression could be induced by abiotic stresses such as cold, salt, drought and exogenous abscisic acid. These findings suggested that ThPOD1 might be involved in the plant response to environmental stresses and ABA treatment. To elucidate the function of this gene, recombinant plasmids expressing full-length ThPOD1 as well as ThPOD2 (aa 41-337), and ThPOD3 (aa 73-337) truncated polypeptides were constructed. SDS-PAGE and Western blot analyses of the fusion proteins revealed that the molecular weights of ThPOD1, ThPOD2 and ThPOD3 were approximately 57, approximately 50 and approximately 47 kDa, respectively. Stress assays of E. coli treated with the recombinant plasmids indicated that ThPOD3 could improve resistance to drought stress. This finding could potentially be used to improve plant tolerance to drought stress via gene transfer.

Co-expression of NCED and ALO improves vitamin C level and tolerance to drought and chilling in transgenic tobacco and stylo plants.

Science.gov (United States)

Bao, Gegen; Zhuo, Chunliu; Qian, Chunmei; Xiao, Ting; Guo, Zhenfei; Lu, Shaoyun

2016-01-01

Abscisic acid (ABA) regulates plant adaptive responses to various environmental stresses, while L-ascorbic acid (AsA) that is also named vitamin C is an important antioxidant and involves in plant stress tolerance and the immune system in domestic animals. Transgenic tobacco (Nicotiana tabacum L.) and stylo [Stylosanthes guianensis (Aublet) Swartz], a forage legume, plants co-expressing stylo 9-cis-epoxycarotenoid dioxygenase (SgNCED1) and yeast D-arabinono-1,4-lactone oxidase (ALO) genes were generated in this study, and tolerance to drought and chilling was analysed in comparison with transgenic tobacco overexpressing SgNCED1 or ALO and the wild-type plants. Compared to the SgNCED1 or ALO transgenic plants, in which only ABA or AsA levels were increased, both ABA and AsA levels were increased in transgenic tobacco and stylo plants co-expressing SgNCED1 and ALO genes. Compared to the wild type, an enhanced drought tolerance was observed in SgNCED1 transgenic tobacco plants with induced expression of drought-responsive genes, but not in ALO plants, while an enhanced chilling tolerance was observed in ALO transgenic tobaccos with induced expression of cold-responsive genes, but not in SgNCED1 plants. Co-expression of SgNCED1 and ALO genes resulted in elevated tolerance to both drought and chilling in transgenic tobacco and stylo plants with induced expression of both drought and cold-responsive genes. Our result suggests that co-expression of SgNCED1 and ALO genes is an effective way for use in forage plant improvement for increased tolerance to drought and chilling and nutrition quality. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

Seed treatments with essential oils protect radish seedlings against drought

Directory of Open Access Journals (Sweden)

Joshua D. Klein

2017-10-01

Full Text Available Establishment of seedlings of economic crops is often reduced if there is not a steady supply of water. Essential oils (EO from plants are increasingly used instead of synthetic chemicals to protect plant and animal products against biotic and abiotic stresses. We investigated priming radish seeds by soaking or by matriconditioning with synthetic or natural compounds as a means of inducing resistance to drought stress, thus maintaining crop yield. Priming radish seeds for two hours in solutions of essential oils (EO thymol and carvacrol derived from Origanum syriacum, with “oregano natural product” (ONP; a solution of the residue remaining after EO extraction, or with the gibberellin synthesis inhibitor trinexapac ethyl (TE, was much more effective in inducing drought resistance than was matriconditioning with the same compounds in sawdust for two days. The latter treatment induced considerable fungal and bacterial infection in treated seeds if the substrate-matrix was not heat-treated beforehand. The increase in specific leaf area in plants from treated seeds was mostly consistent with an increase in leaf water content. Seed treatments with EO, ONP, and especially TE led to a three-fold increase in radish seedling survival compared with water-treated controls, when 21 day-old seedlings were irrigated after 6 days of drought. Under drought conditions, seedlings from treated seeds had a 2–3-fold increase in relative water content increased 2–3-fold, while membrane permeability decreased 20–50-fold as a result of the treatments. However, the physical benefits of the treatments often did not correlate with treatment-induced increases in physiological parameters such as pigments (chlorophyll, carotenoid, anthocyanin, pigment ratios (chlorophyll a/b, carotenoid/chlorophyll, or antioxidant activity. Seed treatments with biostimulants can be as effective as treatments with synthetic compounds in inducing drought resistance in seedlings.

Identification of the influencing factors on groundwater drought in Bangladesh

Science.gov (United States)

Touhidul Mustafa, Syed Md.; Huysmans, Marijke

2015-04-01

Groundwater drought is a specific type of drought that concerns groundwater bodies. It may have a significant adverse effect on the socio-economic, agricultural, and environmental conditions. Investigating the effect of response different climatic and manmade factors on groundwater drought provides essential information for sustainable planning and management of water resources. The aim of this study is to identify the influencing factors on groundwater drought in a drought prone region in Bangladesh to understand the forcing mechanisms. The Standardised Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) have been used to quantify the aggregated deficit between precipitation and the evaporative demand of the atmosphere. The influence of land use patterns on the groundwater drought has been identified by calculating spatially distributed groundwater recharge as a function of land use. The result shows that drought intensity is more severe during the dry season (November to April) compared to the rainy season (May to October). The evapotranspiration and rainfall deficit has a significant effect on meteorological drought which has a direct relation with groundwater drought. Urbanization results in a decrease of groundwater recharge which increases groundwater drought severity. Overexploitation of groundwater for irrigation and recurrent meteorological droughts are the main causes of groundwater drought in the study area. Efficient irrigation management is essential to reduce the growing pressure on groundwater resources and ensure sustainable water management. More detailed studies on climate change and land use change effects on groundwater drought are recommended. Keywords: Groundwater drought, SPI & RDI, Spatially distributed groundwater recharge, Irrigation, Bangladesh

Assessment of Drought Severity Techniques - A Historical Perspective

Science.gov (United States)

Panu, U. S.; Crinklaw, T.

2011-12-01

Droughts are natural phenomenon experienced by all nations across the globe. Drought inherently means a scarcity of water, which adversely affects various sectors of human socio-economic spectrum, e.g. agriculture, hydropower generation, water supply, industry, recreation, navigation, fish production etc. The prime cause of droughts is the occurrence of less than optimal (below normal) precipitation, which has its origin to various natural reasons, the most important being the global climatic forcing. Droughts are also referred to as sustained and regionally extensive occurrences of below average water availability which invariably cultivate into environmental disasters. The evolution of a drought event is defined into four types; meteorological, agricultural, hydrological, and socio-economic. Drought affects all aspects of societal systems irrespective of how it is defined. This has led to a wide range of studies conducted by meteorologists, ecologists, environmentalists, hydrologists, geologists and agricultural scientists in attempts to understand drought processes as required to analyze and predict the impacts of droughts. A conceptual definition, such as a shortage of water relied on by human activity, avoids quantification of a drought event. On the other hand, the purpose of an operational definition is to determine the beginning, termination, and severity of a drought event. The severity assessment of droughts is of primary importance for allocation and management of available water resources. The progression and impact of historical droughts in a region is helpful for developing relationships and techniques to investigate relevant characteristics of droughts. For optimum drought preparedness and mitigative responses, professional bodies need to provide information to private and government agencies in a manner that may also be understood by their employers, stakeholders and the general public. Drought indicators bridge this communication gap between all

heritability analysis of putative drought adaptation traits

African Journals Online (AJOL)

ACSS

2014-02-11

Feb 11, 2014 ... College of Agricultural and Environmental Sciences, School of Agricultural ... effects is most appropriate for drought tolerance improvement in sweetpotato. ..... GCA, SCA mean squares and heritability values for the various ...

Analysis of Natural Variation in Bermudagrass (Cynodon dactylon) Reveals Physiological Responses Underlying Drought Tolerance

Science.gov (United States)

Cheng, Zhangmin; Ye, Tiantian; Chan, Zhulong

2012-01-01

Bermudagrass (Cynodon dactylon) is a widely used warm-season turfgrass and one of the most drought tolerant species. Dissecting the natural variation in drought tolerance and physiological responses will bring us powerful basis and novel insight for plant breeding. In the present study, we evaluated the natural variation of drought tolerance among nine bermudagrass varieties by measuring physiological responses after drought stress treatment through withholding water. Three groups differing in drought tolerance were identified, including two tolerant, five moderately tolerant and two susceptible varieties. Under drought stress condition, drought sensitive variety (Yukon) showed relative higher water loss, more severe cell membrane damage (EL), and more accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA), while drought tolerant variety (Tifgreen) exhibited significantly higher antioxidant enzymes activities. Further results indicated that drought induced cell injury in different varieties (Yukon, SR9554 and Tifgreen) exhibited liner correlation with leaf water content (LWC), H2O2 content, MDA content and antioxidant enzyme activities. Additionally, Tifgreen plants had significantly higher levels of osmolytes (proline level and soluble sugars) when compared with Yukon and SR9554 under drought stress condition. Taken together, our results indicated that natural variation of drought stress tolerance in bermudagrass varieties might be largely related to the induced changes of water status, osmolyte accumulation and antioxidant defense system. PMID:23285294

Bacterial mediated amelioration of drought stress in drought tolerant ...

African Journals Online (AJOL)

Bacterial mediated amelioration of drought stress in drought tolerant and susceptible cultivars of rice ( Oryza sativa L.) ... and IR-64 (drought sensitive) cultivars of rice (Oryza sativa L.) under different level of drought stress. ... from 32 Countries:.

Empirical Analysis of Farmers' Drought Risk Perception: Objective Factors, Personal Circumstances and Social Influence

NARCIS (Netherlands)

van Duinen, Rianne; Filatova, Tatiana; Geurts, Petrus A.T.M.; van der Veen, A.

2014-01-01

Drought-induced water shortage and salinization are a global threat to agricultural production. With climate change, drought risk is expected to increase as drought events are assumed to occur more frequently and to become more severe. The agricultural sector's adaptive capacity largely depends on

Developing drought impact functions for drought risk management

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S. Bachmair

2017-11-01

Full Text Available Drought management frameworks are dependent on methods for monitoring and prediction, but quantifying the hazard alone is arguably not sufficient; the negative consequences that may arise from a lack of precipitation must also be predicted if droughts are to be better managed. However, the link between drought intensity, expressed by some hydrometeorological indicator, and the occurrence of drought impacts has only recently begun to be addressed. One challenge is the paucity of information on ecological and socioeconomic consequences of drought. This study tests the potential for developing empirical drought impact functions based on drought indicators (Standardized Precipitation and Standardized Precipitation Evaporation Index as predictors and text-based reports on drought impacts as a surrogate variable for drought damage. While there have been studies exploiting textual evidence of drought impacts, a systematic assessment of the effect of impact quantification method and different functional relationships for modeling drought impacts is missing. Using Southeast England as a case study we tested the potential of three different data-driven models for predicting drought impacts quantified from text-based reports: logistic regression, zero-altered negative binomial regression (hurdle model, and an ensemble regression tree approach (random forest. The logistic regression model can only be applied to a binary impact/no impact time series, whereas the other two models can additionally predict the full counts of impact occurrence at each time point. While modeling binary data results in the lowest prediction uncertainty, modeling the full counts has the advantage of also providing a measure of impact severity, and the counts were found to be reasonably predictable. However, there were noticeable differences in skill between modeling methodologies. For binary data the logistic regression and the random forest model performed similarly well based on

Analysis of DNA methylation of perennial ryegrass under drought using the methylation-sensitive amplification polymorphism (MSAP) technique.

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Tang, Xiao-Mei; Tao, Xiang; Wang, Yan; Ma, Dong-Wei; Li, Dan; Yang, Hong; Ma, Xin-Rong

2014-12-01

Perennial ryegrass (Lolium perenne), an excellent grass for forage and turf, is widespread in temperate regions. Drought is an important factor that limits its growth, distribution, and yield. DNA methylation affects gene expression and plays an important role in adaptation to adverse environments. In this study, the DNA methylation changes in perennial ryegrass under drought stress were assessed using methylation-sensitive amplified polymorphism (MSAP). After 15 days of drought stress treatment, the plant height was less than half of the control, and the leaves were smaller and darker. Genome-wide, a total of 652 CCGG sites were detected by MSAP. The total methylation level was 57.67 and 47.39 % in the control and drought treatment, respectively, indicating a decrease of 10.28 % due to drought exposure. Fifteen differentially displayed DNA fragments in MSAP profiles were cloned for sequencing analysis. The results showed that most of the genes involved in stress responses. The relative expression levels revealed that three demethylated fragments were up-regulated. The expression of a predicted retrotransposon increased significantly, changing from hypermethylation to non-methylation. Although the extent of methylation in two other genes decreased, the sites of methylation remained, and the expression increased only slightly. All of these results suggested that drought stress decreased the total DNA methylation level in perennial ryegrass and demethylation up-regulated related gene expressions and that the extent of methylation was negatively correlated with expression. Overall, the induced epigenetic changes in genome probably are an important regulatory mechanism for acclimating perennial ryegrass to drought and possibly other environmental stresses.

Pretreatment of seed with H2O2 enhances drought tolerance of ...

African Journals Online (AJOL)

Drought is an important environmental constraint limiting the productivity of many crops worldwide. Seedling tolerance to drought is crucial for crop growth and development through the whole season under water-limited condition. Experiments were conducted to investigate the effects of seed pretreatment by hydrogen ...

Roles of gibberellin catabolism and signaling in growth and physiological response to drought and short-day photoperiods in Populus trees.

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Christine Zawaski

Full Text Available Survival and productivity of perennial plants in temperate zones are dependent on robust responses to prolonged and seasonal cycles of unfavorable conditions. Here we report whole-genome microarray, expression, physiological, and transgenic evidence in hybrid poplar (Populus tremula × Populus alba showing that gibberellin (GA catabolism and repressive signaling mediates shoot growth inhibition and physiological adaptation in response to drought and short-day (SD induced bud dormancy. Both water deprivation and SDs elicited activation of a suite of poplar GA2ox and DELLA encoding genes. Poplar transgenics with up-regulated GA 2-oxidase (GA2ox and DELLA domain proteins showed hypersensitive growth inhibition in response to both drought and SDs. In addition, the transgenic plants displayed greater drought resistance as evidenced by increased pigment concentrations (chlorophyll and carotenoid and reductions in electrolyte leakage (EL. Comparative transcriptome analysis using whole-genome microarray showed that the GA-deficiency and GA-insensitivity, SD-induced dormancy, and drought response in poplar share a common regulon of 684 differentially-expressed genes, which suggest GA metabolism and signaling plays a role in plant physiological adaptations in response to alterations in environmental factors. Our results demonstrate that GA catabolism and repressive signaling represents a major route for control of growth and physiological adaptation in response to immediate or imminent adverse conditions.

A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests

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Allen, Craig D.; Macalady, A.K.; Chenchouni, H.; Bachelet, D.; McDowell, N.; Vennetier, Michel; Kitzberger, T.; Rigling, A.; Breshears, D.D.; Hogg, E.H.(T.); Gonzalez, P.; Fensham, R.; Zhang, Z.; Castro, J.; Demidova, N.; Lim, J.-H.; Allard, G.; Running, S.W.; Semerci, A.; Cobb, N.

2010-01-01

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are potential increases in tree mortality associated with climate-induced physiological stress and interactions with other climate-mediated processes such as insect outbreaks and wildfire. Despite this risk, existing projections of tree mortality are based on models that lack functionally realistic mortality mechanisms, and there has been no attempt to track observations of climate-driven tree mortality globally. Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world's forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks. Our review also identifies key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system. Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide.

Risk assessment of drought disaster in southern China

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Wang, Y.

2015-12-01

Abstract: Drought has become an increasing concern in southern China, but the drought risk has not been adequately studied. This study presents a method for the spatial assessment of drought risk in southern China using a conceptual framework that emphasizes the combined role of hazard, vulnerability, and exposure.A drought hazard map was retrieved with a compound index of meteorological drought method in a GIS environment. Normally, a large variation in the disaster-inducing factor implies a high probability of economic/social losses caused by a drought disaster. The map indicated that areas with a higher risk of drought hazard were mainly distributed in mid-east Yunnan and the basins in eastern Sichuan.The vulnerability indices were based on climate factors as well as land use, geomorphological types, soil properties, and drainage density. The water preserving capability of purple calcareous soil in the basins in Sichuan and mid-east Yunnan, and the lateritic red soil in northeastern Guangdong is relatively weak. The main geomorphological features in Guangxi and Guangdong are hills, which leads to a serious expectation of soil and water losses. Thus, the main areas with a high risk of drought vulnerability are mid-east Yunnan and the basins in eastern Sichuan.The exposure indices were based on population density and agricultural production because population and agriculture experience the main impacts of a drought disaster. Higher exposure indices mean higher economic/social losses due to drought disasters. Areas with high exposure indices were mainly distributed in Guangdong and southern Guangxi.The overall risk was then calculated as the product of the hazard, vulnerability, and exposure. The results indicated a higher risk of drought disaster in the basins in eastern Sichuan,, northeastern Yunnan, and northeastern Guangdong. The main factor influencing the risk of a drought disaster was the hazard, but the vulnerability and exposure also played important roles.

Genotypic variation in growth and physiological response to drought stress and re-watering reveals the critical role of recovery in drought adaptation in maize seedlings

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Daoqian eChen

2016-01-01

Full Text Available Non-irrigated crops in temperate climates and irrigated crops in arid climates are subjected to continuous cycles of water stress and re-watering. Thus, fast and efficient recovery from water stress may be among the key determinants of plant drought adaptation. The present study was designed to comparatively analyze the roles of drought resistance and drought recovery in drought adaptation and to investigate the physiological basis of genotypic variation in drought adaptation in maize (Zea mays seedlings. As the seedlings behavior in growth associate with yield under drought, it could partly reflect the potential of drought adaptability. Growth and physiological responses to progressive drought stress and recovery were observed in seedlings of ten maize lines. The results showed that drought adaptability is closely related to drought recovery (r = 0.714**, but not to drought resistance (r = 0.332. Drought induced decreases in leaf water content, water potential, osmotic potential, gas exchange parameters, chlorophyll content, Fv/Fm and nitrogen content, and increased H2O2 accumulation and lipid peroxidation. After recovery, most of these physiological parameters rapidly returned to normal levels. The physiological responses varied between lines. Further correlation analysis indicated that the physiological bases of drought resistance and drought recovery are definitely different, and that maintaining higher chlorophyll content (r = 0.874*** and Fv/Fm (r = 0.626* under drought stress contributes to drought recovery. Our results suggest that both drought resistance and recovery are key determinants of plant drought adaptation, and that drought recovery may play a more important role than previously thought. In addition, leaf water potential, chlorophyll content and Fv/Fm could be used as efficient reference indicators in the selection of drought-adaptive genotypes.

Spatiotemporal Drought Analysis and Drought Indices Comparison in India

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Janardhanan, A.

2017-12-01

Droughts and floods are an ever-occurring phenomenon that has been wreaking havoc on humans since the start of time. As droughts are on a very large scale, studying them within a regional context can minimize confounding factors such as climate change. Droughts and floods are extremely erratic and very difficult to predict and therefore necessitate modeling through advanced statistics. The SPI (Standard Precipitation Index) and the SPEI (Standard Precipitation Evapotranspiration Index) are two ways to temporally model drought and flood patterns across each metrological sub basin in India over a variety of different time scales. SPI only accounts for precipitation values, while the SPEI accounts for both precipitation and temperature and is commonly regarded as a more reliable drought index. Using monthly rainfall and temperature data from 1871-2016, these two indices were calculated. The results depict the drought and flood severity index, length of drought, and average SPI or SPEI value for each meteorological sub region in India. A Wilcox Ranksum test was then conducted to determine whether these two indices differed over the long term for drought analysis. The drought return periods were analyzed to determine if the population mean differed between the SPI and SPEI values. Our analysis found no statistical difference between SPI and SPEI with regards to long-term drought analysis. This indicates that temperature is not needed when modeling drought on a long-term time scale and that SPI is just as effective as SPEI, which has the potential to save a lot of time and resources on calculating drought indices.

Risk identification of agricultural drought for sustainable Agroecosystems

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Dalezios, N. R.; Blanta, A.; Spyropoulos, N. V.; Tarquis, A. M.

2014-09-01

Drought is considered as one of the major natural hazards with a significant impact on agriculture, environment, society and economy. Droughts affect sustainability of agriculture and may result in environmental degradation of a region, which is one of the factors contributing to the vulnerability of agriculture. This paper addresses agrometeorological or agricultural drought within the risk management framework. Risk management consists of risk assessment, as well as a feedback on the adopted risk reduction measures. And risk assessment comprises three distinct steps, namely risk identification, risk estimation and risk evaluation. This paper deals with risk identification of agricultural drought, which involves drought quantification and monitoring, as well as statistical inference. For the quantitative assessment of agricultural drought, as well as the computation of spatiotemporal features, one of the most reliable and widely used indices is applied, namely the vegetation health index (VHI). The computation of VHI is based on satellite data of temperature and the normalized difference vegetation index (NDVI). The spatiotemporal features of drought, which are extracted from VHI, are areal extent, onset and end time, duration and severity. In this paper, a 20-year (1981-2001) time series of the National Oceanic and Atmospheric Administration/advanced very high resolution radiometer (NOAA/AVHRR) satellite data is used, where monthly images of VHI are extracted. Application is implemented in Thessaly, which is the major agricultural drought-prone region of Greece, characterized by vulnerable agriculture. The results show that agricultural drought appears every year during the warm season in the region. The severity of drought is increasing from mild to extreme throughout the warm season, with peaks appearing in the summer. Similarly, the areal extent of drought is also increasing during the warm season, whereas the number of extreme drought pixels is much less than

Modulation of Antioxidant Defense System Is Associated with Combined Drought and Heat Stress Tolerance in Citrus.

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Zandalinas, Sara I; Balfagón, Damián; Arbona, Vicent; Gómez-Cadenas, Aurelio

2017-01-01

Drought and high temperatures are two major abiotic stress factors that often occur simultaneously in nature, affecting negatively crop performance and yield. Moreover, these environmental challenges induce oxidative stress in plants through the production of reactive oxygen species (ROS). Carrizo citrange and Cleopatra mandarin are two citrus genotypes with contrasting ability to cope with the combination of drought and heat stress. In this work, a direct relationship between an increased antioxidant activity and stress tolerance is reported. According to our results, the ability of Carrizo plants to efficiently coordinate superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR) activities involved in ROS detoxification along with the maintenance of a favorable GSH/GSSG ratio could be related to their relative tolerance to this stress combination. On the other hand, the increment of SOD activity and the inefficient GR activation along with the lack of CAT and APX activities in Cleopatra plants in response to the combination of drought and heat stress, could contribute to an increased oxidative stress and the higher sensibility of this citrus genotype to this stress combination.

Transcriptome analysis of Pinus halepensis under drought stress and during recovery.

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Fox, Hagar; Doron-Faigenboim, Adi; Kelly, Gilor; Bourstein, Ronny; Attia, Ziv; Zhou, Jing; Moshe, Yosef; Moshelion, Menachem; David-Schwartz, Rakefet

2018-03-01

Forest trees use various strategies to cope with drought stress and these strategies involve complex molecular mechanisms. Pinus halepensis Miller (Aleppo pine) is found throughout the Mediterranean basin and is one of the most drought-tolerant pine species. In order to decipher the molecular mechanisms that P. halepensis uses to withstand drought, we performed large-scale physiological and transcriptome analyses. We selected a mature tree from a semi-arid area with suboptimal growth conditions for clonal propagation through cuttings. We then used a high-throughput experimental system to continuously monitor whole-plant transpiration rates, stomatal conductance and the vapor pressure deficit. The transcriptomes of plants were examined at six physiological stages: pre-stomatal response, partial stomatal closure, minimum transpiration, post-irrigation, partial recovery and full recovery. At each stage, data from plants exposed to the drought treatment were compared with data collected from well-irrigated control plants. A drought-stressed P. halepensis transcriptome was created using paired-end RNA-seq. In total, ~6000 differentially expressed, non-redundant transcripts were identified between drought-treated and control trees. Cluster analysis has revealed stress-induced down-regulation of transcripts related to photosynthesis, reactive oxygen species (ROS)-scavenging through the ascorbic acid (AsA)-glutathione cycle, fatty acid and cell wall biosynthesis, stomatal activity, and the biosynthesis of flavonoids and terpenoids. Up-regulated processes included chlorophyll degradation, ROS-scavenging through AsA-independent thiol-mediated pathways, abscisic acid response and accumulation of heat shock proteins, thaumatin and exordium. Recovery from drought induced strong transcription of retrotransposons, especially the retrovirus-related transposon Tnt1-94. The drought-related transcriptome illustrates this species' dynamic response to drought and recovery and unravels

Building the vegetation drought response index for Canada (VegDRI-Canada) to monitor agricultural drought: first results

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Tadesse, Tsegaye; Champagne, Catherine; Wardlow, Brian D.; Hadwen, Trevor A.; Brown, Jesslyn; Demisse, Getachew B.; Bayissa, Yared A.; Davidson, Andrew M.

2017-01-01

Drought is a natural climatic phenomenon that occurs throughout the world and impacts many sectors of society. To help decision-makers reduce the impacts of drought, it is important to improve monitoring tools that provide relevant and timely information in support of drought mitigation decisions. Given that drought is a complex natural hazard that manifests in different forms, monitoring can be improved by integrating various types of information (e.g., remote sensing and climate) that is timely and region specific to identify where and when droughts are occurring. The Vegetation Drought Response Index for Canada (VegDRI-Canada) is a recently developed drought monitoring tool for Canada. VegDRI-Canada extends the initial VegDRI concept developed for the conterminous United States to a broader transnational coverage across North America. VegDRI-Canada models are similar to those developed for the United States, integrating satellite observations of vegetation status, climate data, and biophysical information on land use and land cover, soil characteristics, and other environmental factors. Collectively, these different types of data are integrated into the hybrid VegDRI-Canada to isolate the effects of drought on vegetation. Twenty-three weekly VegDRI-Canada models were built for the growing season (April–September) through the weekly analysis of these data using a regression tree-based data mining approach. A 15-year time series of VegDRI-Canada results (s to 2014) was produced using these models and the output was validated by randomly selecting 20% of the historical data, as well as holdout year (15% unseen data) across the growing season that the Pearson’s correlation ranged from 0.6 to 0.77. A case study was also conducted to evaluate the VegDRI-Canada results over the prairie region of Canada for two drought years and one non-drought year for three weekly periods of the growing season (i.e., early-, mid-, and late season). The comparison of the Veg

SDI and Markov Chains for Regional Drought Characteristics

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Chen-Feng Yeh

2015-08-01

Full Text Available In recent years, global climate change has altered precipitation patterns, causing uneven spatial and temporal distribution of precipitation that gradually induces precipitation polarization phenomena. Taiwan is located in the subtropical climate zone, with distinct wet and dry seasons, which makes the polarization phenomenon more obvious; this has also led to a large difference between river flows during the wet and dry seasons, which is significantly influenced by precipitation, resulting in hydrological drought. Therefore, to effectively address the growing issue of water shortages, it is necessary to explore and assess the drought characteristics of river systems. In this study, the drought characteristics of northern Taiwan were studied using the streamflow drought index (SDI and Markov chains. Analysis results showed that the year 2002 was a turning point for drought severity in both the Lanyang River and Yilan River basins; the severity of rain events in the Lanyang River basin increased after 2002, and the severity of drought events in the Yilan River basin exhibited a gradual upward trend. In the study of drought severity, analysis results from periods of three months (November to January and six months (November to April have shown significant drought characteristics. In addition, analysis of drought occurrence probabilities using the method of Markov chains has shown that the occurrence probabilities of drought events are higher in the Lanyang River basin than in the Yilan River basin; particularly for extreme events, the occurrence probability of an extreme drought event is 20.6% during the dry season (November to April in the Lanyang River basin, and 3.4% in the Yilan River basin. This study shows that for analysis of drought/wet occurrence probabilities, the results obtained for the drought frequency and occurrence probability using short-term data with the method of Markov chains can be used to predict the long-term occurrence

Drought occurence

Science.gov (United States)

John W. Coulston

2007-01-01

Why Is Drought Important? Drought is an important forest disturbance that occurs regularly in the Western United States and irregularly in the Eastern United States (Dale and others 2001). Moderate drought stress tends to slow plant growth while severedrought stress can also reduce photosynthesis (Kareiva and others 1993). Drought can also interact with...

Canopy Transpiration and Stomatal Responses to Prolonged Drought by a Dominant Desert Species in Central Asia

Directory of Open Access Journals (Sweden)

Daxing Gu

2017-06-01

Full Text Available In arid and semiarid lands, canopy transpiration and its dynamics depend largely on stomatal sensitivity to drought. In this study, the sap flow of a dominant species, Haloxylon ammodendron growing in Central Asian deserts, was monitored using Granier-type sensors, from which the canopy stomatal conductance was derived. The responses of canopy transpiration and stomatal conductance to environmental variables during the second half of the growing season, when annual prolonged drought occurred, was analyzed for four continuous years, from 2013 to 2016. A soil water content (SWC of 3% was identified as the lower soil water threshold for this species, below which the plant lost the ability for stomatal regulation on water loss and suffered the risk of mortality. Above this threshold, the sensitivity of canopy transpiration to vapor pressure deficit, VPD (K, was linearly correlated with SWC, which mainly resulted from different stomatal behaviors at varying drought intensities. Stomatal sensitivity to VPD (m/Gsref increased linearly with soil moisture deficit, inducing a shift from more anisohydric to a more isohydric stomatal behavior. The flexibility of stomatal behavior regarding soil drought was one key element facilitating the survival of H. ammodendron in such an extreme dry environment.

Comprehensive drought characteristics analysis based on a nonlinear multivariate drought index

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Yang, Jie; Chang, Jianxia; Wang, Yimin; Li, Yunyun; Hu, Hui; Chen, Yutong; Huang, Qiang; Yao, Jun

2018-02-01

It is vital to identify drought events and to evaluate multivariate drought characteristics based on a composite drought index for better drought risk assessment and sustainable development of water resources. However, most composite drought indices are constructed by the linear combination, principal component analysis and entropy weight method assuming a linear relationship among different drought indices. In this study, the multidimensional copulas function was applied to construct a nonlinear multivariate drought index (NMDI) to solve the complicated and nonlinear relationship due to its dependence structure and flexibility. The NMDI was constructed by combining meteorological, hydrological, and agricultural variables (precipitation, runoff, and soil moisture) to better reflect the multivariate variables simultaneously. Based on the constructed NMDI and runs theory, drought events for a particular area regarding three drought characteristics: duration, peak, and severity were identified. Finally, multivariate drought risk was analyzed as a tool for providing reliable support in drought decision-making. The results indicate that: (1) multidimensional copulas can effectively solve the complicated and nonlinear relationship among multivariate variables; (2) compared with single and other composite drought indices, the NMDI is slightly more sensitive in capturing recorded drought events; and (3) drought risk shows a spatial variation; out of the five partitions studied, the Jing River Basin as well as the upstream and midstream of the Wei River Basin are characterized by a higher multivariate drought risk. In general, multidimensional copulas provides a reliable way to solve the nonlinear relationship when constructing a comprehensive drought index and evaluating multivariate drought characteristics.

Cytokinins induce transcriptional reprograming and improve Arabidopsis plant performance under drought and salt stress conditions.

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Natali Shirron

2016-10-01

Full Text Available In nature, annual plants respond to abiotic stresses by activating a specific genetic program leading to early flowering and accelerated senescence. Although, in nature, this phenomenon supports survival under unfavorable environmental conditions, it may have negative agro-economic impacts on crop productivity. Overcoming this genetic programing by cytokinins (CK has recently been shown in transgenic plants that overproduce CK. These transgenic plants displayed a significant increase in plant productivity under drought stress conditions. We investigated the role of CK in reverting the transcriptional program that is activated under abiotic stress conditions and allowing sustainable plant growth. We employed 2 complementary approaches: Ectopic overexpression of CK, and applying exogenous CK to detached Arabidopsis leaves. Transgenic Arabidopsis plants transformed with the isopentyltransferase (IPT gene under the regulation of the senescence associated receptor kinase (SARK promoter displayed a significant drought resistance. A transcriptomic analysis using RNA sequencing was performed to explore the response mechanisms under elevated CK levels during salinity stress. This analysis showed that under such stress, CK triggered transcriptional reprograming that resulted in attenuated stress-dependent inhibition of vegetative growth and delayed premature plant senescence. Our data suggest that elevated CK levels led to stress tolerance by retaining the expression of genes associated with plant growth and metabolism whose expression typically decreases under stress conditions. In conclusion, we hypothesize that CK allows sustainable plant growth under unfavorable environmental conditions by activating gene expression related to growth processes and by preventing the expression of genes related to the activation of premature senescence.

Evaluation of different drought stress periods on Hevea brasiliensis ...

African Journals Online (AJOL)

As global demand for natural rubber increases, a major challenge for cultivation of rubber plants is their inability to withstand unfavorable environmental conditions in the context of global climate change. Drought remains one of the most biologically demanding and ecologically limiting factors among all environmental ...

Proteomic responses of drought-tolerant and drought-sensitive cotton varieties to drought stress.

Science.gov (United States)

Zhang, Haiyan; Ni, Zhiyong; Chen, Quanjia; Guo, Zhongjun; Gao, Wenwei; Su, Xiujuan; Qu, Yanying

2016-06-01

Drought, one of the most widespread factors reducing agricultural crop productivity, affects biological processes such as development, architecture, flowering and senescence. Although protein analysis techniques and genome sequencing have made facilitated the proteomic study of cotton, information on genetic differences associated with proteomic changes in response to drought between different cotton genotypes is lacking. To determine the effects of drought stress on cotton seedlings, we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry to comparatively analyze proteome of drought-responsive proteins during the seedling stage in two cotton (Gossypium hirsutum L.) cultivars, drought-tolerant KK1543 and drought-sensitive Xinluzao26. A total of 110 protein spots were detected on 2-DE maps, of which 56 were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry. The identified proteins were mainly associated with metabolism (46.4 %), antioxidants (14.2 %), and transport and cellular structure (23.2 %). Some key proteins had significantly different expression patterns between the two genotypes. In particular, 5-methyltetrahydropteroyltriglutamate-homocysteine methyltransferase, UDP-D-glucose pyrophosphorylase and ascorbate peroxidase were up-regulated in KK1543 compared with Xinluzao26. Under drought stress conditions, the vacuolar H(+)-ATPase catalytic subunit, a 14-3-3g protein, translation initiation factor 5A and pathogenesis-related protein 10 were up-regulated in KK1543, whereas ribosomal protein S12, actin, cytosolic copper/zinc superoxide dismutase, protein disulfide isomerase, S-adenosylmethionine synthase and cysteine synthase were down-regulated in Xinluzao26. This work represents the first characterization of proteomic changes that occur in response to drought in roots of cotton plants. These differentially expressed proteins may be related to

β-aminobutyric acid mediated drought stress alleviation in maize (Zea mays L.).

Science.gov (United States)

Shaw, Arun K; Bhardwaj, Pardeep K; Ghosh, Supriya; Roy, Sankhajit; Saha, Suman; Sherpa, Ang R; Saha, Samir K; Hossain, Zahed

2016-02-01

The present study highlights the role of β-aminobutyric acid (BABA) in alleviating drought stress effects in maize (Zea mays L.). Chemical priming was imposed by pretreating 1-week-old plants with 600 μM BABA prior to applying drought stress. Specific activities of key antioxidant enzymes and metabolites (ascorbate and glutathione) levels of ascorbate-glutathione cycle were studied to unravel the priming-induced modulation of plant defense system. Furthermore, changes in endogenous ABA and JA concentrations as well as mRNA expressions of key genes involved in their respective biosynthesis pathways were monitored in BABA-primed (BABA+) and non-primed (BABA-) leaves of drought-challenged plants to better understand the mechanistic insights into the BABA-induced hormonal regulation of plant response to water-deficit stress. Accelerated stomatal closure, high relative water content, and less membrane damage were observed in BABA-primed leaves under water-deficit condition. Elevated APX and SOD activity in non-primed leaves found to be insufficient to scavenge all H2O2 and O2 (·-) resulting in oxidative burst as evident after histochemical staining with NBT and DAB. A higher proline accumulation in non-primed leaves also does not give much protection against drought stress. Increased GR activity supported with the enhanced mRNA and protein expressions might help the BABA-primed plants to maintain a high GSH pool essential for sustaining balanced redox status to counter drought-induced oxidative stress damages. Hormonal analysis suggests that in maize, BABA-potentiated drought tolerance is primarily mediated through JA-dependent pathway by the activation of antioxidant defense systems while ABA biosynthesis pathway also plays an important role in fine-tuning of drought stress response.

Extreme drought decouples silicon and carbon geochemical linkages in lakes.

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Li, Tianyang; Li, Siyue; Bush, Richard T; Liang, Chuan

2018-09-01

Silicon and carbon geochemical linkages were usually regulated by chemical weathering and organism activity, but had not been investigated under the drought condition, and the magnitude and extent of drought effects remain poorly understood. We collected a comprehensive data set from a total of 13 sampling sites covering the main water body of the largest freshwater lake system in Australia, the Lower Lakes. Changes to water quality during drought (April 2008-September 2010) and post-drought (October 2010-October 2013) were compared to reveal the effects of drought on dissolved silica (DSi) and bicarbonate (HCO 3 - ) and other environmental factors, including sodium (Na + ), pH, electrical conductivity (EC), chlorophyll a (Chl-a), total dissolved solids (TDS), dissolved inorganic nitrogen (DIN), total nitrogen (TN), total phosphorus (TP) and water levels. Among the key observations, concentrations of DSi and DIN were markedly lower in drought than in post-drought period while pH, EC and concentrations of HCO 3 - , Na + , Chl-a, TDS, TN, TP and the ratio TN:TP had inverse trends. Stoichiometric ratios of DSi:HCO 3 - , DSi:Na + and HCO 3 - :Na + were significantly lower in the drought period. DSi exhibited significantly negative relationships with HCO 3 - , and DSi:Na + was strongly correlated with HCO 3 - :Na + in both drought and post-drought periods. The backward stepwise regression analysis that could avoid multicollinearity suggested that DSi:HCO 3 - ratio in drought period had significant relationships with fewer variables when compared to the post-drought, and was better predictable using nutrient variables during post-drought. Our results highlight the drought effects on variations of water constituents and point to the decoupling of silicon and carbon geochemical linkages in the Lower Lakes under drought conditions. Copyright © 2018 Elsevier B.V. All rights reserved.

Drought-induced weakening of growth-temperature associations in high-elevation Iberian pines

Science.gov (United States)

Diego Galván, J.; Büntgen, Ulf; Ginzler, Christian; Grudd, Håkan; Gutiérrez, Emilia; Labuhn, Inga; Julio Camarero, J.

2015-01-01

The growth/climate relationship of theoretically temperature-controlled high-elevation forests has been demonstrated to weaken over recent decades. This is likely due to new tree growth limiting factors, such as an increasing drought risk for ecosystem functioning and productivity across the Mediterranean Basin. In addition, declining tree growth sensitivity to spring temperature may emerge in response to increasing drought stress. Here, we evaluate these ideas by assessing the growth/climate sensitivity of 1500 tree-ring width (TRW) and 102 maximum density (MXD) measurement series from 711 and 74 Pinus uncinata trees, respectively, sampled at 28 high-elevation forest sites across the Pyrenees and two relict populations of the Iberian System. Different dendroclimatological standardization and split period approaches were used to assess the high- to low-frequency behavior of 20th century tree growth in response to temperature means, precipitation totals and drought indices. Long-term variations in TRW track summer temperatures until about 1970 but diverge afterwards, whereas MXD captures the recent temperature increase in the low-frequency domain fairly well. On the other hand summer drought has increasingly driven TRW along the 20th century. Our results suggest fading temperature sensitivity of Iberian high-elevation P. uncinata forest growth, and reveal the importance of summer drought that is becoming the emergent limiting factor of tree ring width formation in many parts of the Mediterranean Basin.

Simulation of Drought-induced Tree Mortality Using a New Individual and Hydraulic Trait-based Model (S-TEDy)

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Sinha, T.; Gangodagamage, C.; Ale, S.; Frazier, A. G.; Giambelluca, T. W.; Kumagai, T.; Nakai, T.; Sato, H.

2017-12-01

Drought-related tree mortality at a regional scale causes drastic shifts in carbon and water cycling in Southeast Asian tropical rainforests, where severe droughts are projected to occur more frequently, especially under El Niño conditions. To provide a useful tool for projecting the tropical rainforest dynamics under climate change conditions, we developed the Spatially Explicit Individual-Based (SEIB) Dynamic Global Vegetation Model (DGVM) applicable to simulating mechanistic tree mortality induced by the climatic impacts via individual-tree-scale ecophysiology such as hydraulic failure and carbon starvation. In this study, we present the new model, SEIB-originated Terrestrial Ecosystem Dynamics (S-TEDy) model, and the computation results were compared with observations collected at a field site in a Bornean tropical rainforest. Furthermore, after validating the model's performance, numerical experiments addressing a future of the tropical rainforest were conducted using some global climate model (GCM) simulation outputs.

Faba bean drought responsive gene identification and validation

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Megahed H. Ammar

2017-01-01

Full Text Available This study was carried out to identify drought-responsive genes in a drought tolerant faba bean variety (Hassawi 2 using a suppressive subtraction hybridization approach (SSH. A total of 913 differentially expressed clones were sequenced from a differential cDNA library that resulted in a total of 225 differentially expressed ESTs. The genes of mitochondrial and chloroplast origin were removed, and the remaining 137 EST sequences were submitted to the gene bank EST database (LIBEST_028448. A sequence analysis identified 35 potentially drought stress-related ESTs that regulate ion channels, kinases, and energy production and utilization and transcription factors. Quantitative PCR on Hassawi 2 genotype confirmed that more than 65% of selected drought-responsive genes were drought-related. Among these induced genes, the expression levels of eight highly up-regulated unigenes were further analyzed across 38 selected faba bean genotypes that differ in their drought tolerance levels. These unigenes included ribulose 1,5-bisphosphate carboxylase (rbcL gene, non-LTR retroelement reverse related, probable cyclic nucleotide-gated ion channel, polyubiquitin, potassium channel, calcium-dependent protein kinase and putative respiratory burst oxidase-like protein C and a novel unigene. The expression patterns of these unigenes were variable across 38 genotypes however, it was found to be very high in tolerant genotype. The up-regulation of these unigenes in majority of tolerant genotypes suggests their possible role in drought tolerance. The identification of possible drought responsive candidate genes in Vicia faba reported here is an important step toward the development of drought-tolerant genotypes that can cope with arid environments.

Plant physiology and proteomics reveals the leaf response to drought in alfalfa (Medicago sativa L.).

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Aranjuelo, Iker; Molero, Gemma; Erice, Gorka; Avice, Jean Christophe; Nogués, Salvador

2011-01-01

Despite its relevance, protein regulation, metabolic adjustment, and the physiological status of plants under drought is not well understood in relation to the role of nitrogen fixation in nodules. In this study, nodulated alfalfa plants were exposed to drought conditions. The study determined the physiological, metabolic, and proteomic processes involved in photosynthetic inhibition in relation to the decrease in nitrogenase (N(ase)) activity. The deleterious effect of drought on alfalfa performance was targeted towards photosynthesis and N(ase) activity. At the leaf level, photosynthetic inhibition was mainly caused by the inhibition of Rubisco. The proteomic profile and physiological measurements revealed that the reduced carboxylation capacity of droughted plants was related to limitations in Rubisco protein content, activation state, and RuBP regeneration. Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by N(ase) activity inhibition. In this context, drought induced the decrease in Rubisco binding protein content at the leaf level and proteases were up-regulated so as to degrade Rubisco protein. This degradation enabled the reallocation of the Rubisco-derived N to the synthesis of amino acids with osmoregulant capacity. Rubisco degradation under drought conditions was induced so as to remobilize Rubisco-derived N to compensate for the decrease in N associated with N(ase) inhibition. Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential (Ψ(s)). At the nodule level, drought had an inhibitory effect on N(ase) activity. This decrease in N(ase) activity was not induced by substrate shortage, as reflected by an increase in total soluble sugars (TSS) in the nodules. Proline accumulation

Species biogeography predicts drought responses in a seasonally dry tropical forest

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Schwartz, N.; Powers, J. S.; Vargas, G.; Xu, X.; Smith, C. M.; Brodribb, T.; Werden, L. K.; Becknell, J.; Medvigy, D.

2017-12-01

The timing, distribution, and amount of rainfall in the seasonal tropics have shifted in recent years, with consequences for seasonally dry tropical forests (SDTF). SDTF are sensitive to changing rainfall regimes and drought conditions, but sensitivity to drought varies substantially across species. One potential explanation of species differences is that species that experience dry conditions more frequently throughout their range will be better able to cope with drought than species from wetter climates, because species from drier climates will be better adapted to drought. An El-Niño induced drought in 2015 presented an opportunity to assess species-level differences in mortality in SDTF, and to ask whether the ranges of rainfall conditions species experience and the average rainfall regimes in species' ranges predict differences in mortality rates in Costa Rican SDTF. We used field plot data from northwest Costa Rica to determine species' level mortality rates. Mortality rates ranged substantially across species, with some species having no dead individuals to as high as 50% mortality. To quantify rainfall conditions across species' ranges, we used species occurrence data from the Global Biodiversity Information Facility, and rainfall data from the Chelsa climate dataset. We found that while the average and range of mean annual rainfall across species ranges did not predict drought-induced mortality in the field plots, across-range averages of the seasonality index, a measure of rainfall seasonality, was strongly correlated with species-level drought mortality (r = -0.62, p < 0.05), with species from more strongly seasonal climates experiencing less severe drought mortality. Furthermore, we found that the seasonality index was a stronger predictor of mortality than any individual functional trait we considered. This result shows that species' biogeography may be an important factor for how species will respond to future drought, and may be a more integrative

Drought Risk Identification: Early Warning System of Seasonal Agrometeorological Drought

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Dalecios, Nicolas; Spyropoulos, Nicos V.; Tarquis, Ana M.

2014-05-01

By considering drought as a hazard, drought types are classified into three categories, namely meteorological or climatological, agrometeorological or agricultural and hydrological drought and as a fourth class the socioeconomic impacts can be considered. This paper addresses agrometeorological drought affecting agriculture within the risk management framework. Risk management consists of risk assessment, as well as a feedback on the adopted risk reduction measures. And risk assessment comprises three distinct steps, namely risk identification, risk estimation and risk evaluation. This paper deals with the quantification and monitoring of agrometeorological drought, which constitute part of risk identification. For the quantitative assessment of agrometeorological or agricultural drought, as well as the computation of spatiotemporal features, one of the most reliable and widely used indices is applied, namely the Vegetation Health Index (VHI). The computation of VHI is based on satellite data of temperature and the Normalized Difference Vegetation Index (NDVI). The spatiotemporal features of drought, which are extracted from VHI are: areal extent, onset and end time, duration and severity. In this paper, a 20-year (1981-2001) time series of NOAA/AVHRR satellite data is used, where monthly images of VHI are extracted. Application is implemented in Thessaly, which is the major agricultural region of Greece characterized by vulnerable and drought-prone agriculture. The results show that every year there is a seasonal agrometeorological drought with a gradual increase in the areal extent and severity with peaks appearing usually during the summer. Drought monitoring is conducted by monthly remotely sensed VHI images. Drought early warning is developed using empirical relationships of severity and areal extent. In particular, two second-order polynomials are fitted, one for low and the other for high severity drought, respectively. The two fitted curves offer a seasonal

Chapter 8: Droughts, Floods, and Wildfires

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Wehner, M. F.; Arnold, J. R.; Knutson, T.; Kunkel, K. E.; LeGrande, A. N.

2017-01-01

Recent droughts and associated heat waves have reached record intensity in some regions of the United States; however, by geographical scale and duration, the Dust Bowl era of the 1930s remains the benchmark drought and extreme heat event in the historical record (very high confidence). While by some measures drought has decreased over much of the continental United States in association with long-term increases in precipitation, neither the precipitation increases nor inferred drought decreases have been confidently attributed to anthropogenic forcing. The human effect on recent major U.S. droughts is complicated. Little evidence is found for a human influence on observed precipitation deficits, but much evidence is found for a human influence on surface soil moisture deficits due to increased evapotranspiration caused by higher temperatures. Future decreases in surface (top 10 cm) soil moisture from anthropogenic forcing over most of the United States are likely as the climate warms under higher scenarios. Substantial reductions in western U.S. winter and spring snowpack are projected as the climate warms. Earlier spring melt and reduced snow water equivalent have been formally attributed to human-induced warming (high confidence) and will very likely be exacerbated as the climate continues to warm (very high confidence). Under higher scenarios, and assuming no change to current water resources management, chronic, long-duration hydrological drought is increasingly possible by the end of this century. Detectable changes in some classes of flood frequency have occurred in parts of the United States and are a mix of increases and decreases. Extreme precipitation, one of the controlling factors in flood statistics, is observed to have generally increased and is projected to continue to do so across the United States in a warming atmosphere. However, formal attribution approaches have not established a significant connection of increased riverine flooding to human-induced

Application of Mutation Techniques in the Development of Drought Tolerant Wheat Varieties in Kenya

International Nuclear Information System (INIS)

Kinyua, M.G.; Wanga, H.

1998-01-01

Development of drought tolerant wheat is very important for Kenya as it could lead to utilisation of a large area of the country, which is otherwise under-utilised for crop production. At present there is no crop of economic importance, which being grown in this area. Mutation technique form one of the breeding methods, which can be used to produce suitable wheat varieties for drought prone areas in this country. Wheat seed variety ''pasa'' was irradiated with 160 gy from cobalt source. These irradiated seed were planted at the cage at Njoro, in the main season of 1996. At M2, 4 heads were harvested from 20 selected plants in each row. These were threshed singly. Three of the heads were planted in three sites which experience drought (Katumani, Naivasha and Narok), while one was kept as reserve. Selections of M3 plants, which showed tolerance to drought as compared to the parent variety were made.The parent scored 2 on a 1 to 5 scale for drought tolerance. On this scale 1 indicates susceptibility to drought while 5 indicates drought tolerance. Twenty-one M3 selections scored 4 or 5 on this scale. These therefore showed higher degree of drought tolerance than pasa. For those to score higher than pasa, mutation should have induced some higher degree of drought tolerance.There is indication that, mutation techniques could be used in inducing drought tolerance to wheat growing in Kenya (author)

Genome-wide Differences in DNA Methylation Changes in Two Contrasting Rice Genotypes in Response to Drought Conditions

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Wensheng Wang

2016-11-01

Full Text Available Differences in drought stress tolerance within diverse rice genotypes have been attributed to genetic diversity and epigenetic alterations. DNA methylation is an important epigenetic modification that influences diverse biological processes, but its effects on rice drought stress tolerance are poorly understood. In this study, methylated DNA immunoprecipitation sequencing and an Affymetrix GeneChip rice genome array were used to profile the DNA methylation patterns and transcriptomes of the drought-tolerant introgression line DK151 and its drought-sensitive recurrent parent IR64 under drought and control conditions. The introgression of donor genomic DNA induced genome-wide DNA methylation changes in DK151 plants. A total of 1190 differentially methylated regions (DMRs were detected between the two genotypes under normal growth conditions, and the DMR-associated genes in DK151 plants were mainly related to stress response, programmed cell death, and nutrient reservoir activity, which are implicated to constitutive drought stress tolerance. A comparison of the DNA methylation changes in the two genotypes under drought conditions indicated that DK151 plants have a more stable methylome, with only 92 drought-induced DMRs, than IR64 plants with 506 DMRs. Gene ontology analyses of the DMR-associated genes in drought-stressed plants revealed that changes to the DNA methylation status of genotype-specific genes are associated with the epigenetic regulation of drought stress responses. Transcriptome analysis further helped to identify a set of 12 and 23 DMR-associated genes that were differentially expressed in DK151 and IR64, respectively, under drought stress compared with respective controls. Correlation analysis indicated that DNA methylation has various effects on gene expression, implying that it affects gene expression directly or indirectly through diverse regulatory pathways. Our results indicate that drought-induced alterations to DNA

Simulating US Agriculture in a Modern Dust Bowl Drought

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Glotter, Michael; Elliott, Joshua

2016-01-01

Drought-induced agricultural loss is one of the most costly impacts of extreme weather, and without mitigation, climate change is likely to increase the severity and frequency of future droughts. The Dust Bowl of the 1930s was the driest and hottest for agriculture in modern US history. Improvements in farming practices have increased productivity, but yields today are still tightly linked to climate variation and the impacts of a 1930s-type drought on current and future agricultural systems remain unclear. Simulations of biophysical process and empirical models suggest that Dust-Bowl-type droughts today would have unprecedented consequences, with yield losses approx.50% larger than the severe drought of 2012. Damages at these extremes are highly sensitive to temperature, worsening by approx.25% with each degree centigrade of warming. We find that high temperatures can be more damaging than rainfall deficit, and, without adaptation, warmer mid-century temperatures with even average precipitation could lead to maize losses equivalent to the Dust Bowl drought. Warmer temperatures alongside consecutive droughts could make up to 85% of rain-fed maize at risk of changes that may persist for decades. Understanding the interactions of weather extremes and a changing agricultural system is therefore critical to effectively respond to, and minimize, the impacts of the next extreme drought event.

Socioeconomic Drought in a Changing Climate: Modeling and Management

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AghaKouchak, Amir; Mehran, Ali; Mazdiyasni, Omid

2016-04-01

Drought is typically defined based on meteorological, hydrological and land surface conditions. However, in many parts of the world, anthropogenic changes and water management practices have significantly altered local water availability. Socioeconomic drought refers to conditions whereby the available water supply cannot satisfy the human and environmental water needs. Surface water reservoirs provide resilience against local climate variability (e.g., droughts), and play a major role in regional water management. This presentation focuses on a framework for describing socioeconomic drought based on both water supply and demand information. We present a multivariate approach as a measure of socioeconomic drought, termed Multivariate Standardized Reliability and Resilience Index (MSRRI; Mehran et al., 2015). This model links the information on inflow and surface reservoir storage to water demand. MSRRI integrates a "top-down" and a "bottom-up" approach for describing socioeconomic drought. The "top-down" component describes processes that cannot be simply controlled or altered by local decision-makers and managers (e.g., precipitation, climate variability, climate change), whereas the "bottom-up" component focuses on the local resilience, and societal capacity to respond to droughts. The two components (termed, Inflow-Demand Reliability (IDR) indicator and Water Storage Resilience (WSR) indicator) are integrated using a nonparametric multivariate approach. We use this framework to assess the socioeconomic drought during the Australian Millennium Drought (1998-2010) and the 2011-2014 California Droughts. MSRRI provides additional information on socioeconomic drought onset, development and termination based on local resilience and human demand that cannot be obtained from the commonly used drought indicators. We show that MSRRI can be used for water management scenario analysis (e.g., local water availability based on different human water demands scenarios). Finally

Melatonin enhances cold tolerance in drought-primed wild-type and abscisic acid-deficient mutant barley.

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Li, Xiangnan; Tan, Dun-Xian; Jiang, Dong; Liu, Fulai

2016-10-01

Melatonin is involved in multiple plant developmental processes and various stress responses. To explore the roles of melatonin played as well as its association with abscisic acid (ABA) in a process of drought priming-induced cold tolerance (DPICT), a wild-type barley and its ABA-deficient mutant Az34 counterpart were selected for comparison, in which the effects of melatonin application (either foliarly or rhizospherically) and/or drought priming on the cold tolerance of both types of barleys were systematically investigated. It was demonstrated that the early drought priming induced an increase of endogenous melatonin production, which is not ABA dependent. In addition, exogenously applied melatonin resulted in higher ABA concentration in the drought-primed plants than in the nonprimed plants when exposed to cold stress, indicating that ABA responded in a drought-dependent manner. The interplay of melatonin and ABA leads to plants maintaining better water status. Drought priming-induced melatonin accumulation enhanced the antioxidant capacity in both chloroplasts and mitochondria, which sustained the photosynthetic electron transport in photosynthetic apparatus of the plants under cold stress. These results suggest that the exogenous melatonin application enhances the DPICT by modulating subcellular antioxidant systems and ABA levels in barley. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Assessment of tree response to drought: validation of a methodology to identify and test proxies for monitoring past environmental changes in trees.

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Tene, A; Tobin, B; Dyckmans, J; Ray, D; Black, K; Nieuwenhuis, M

2011-03-01

A thinning experiment stand at Avoca, Ballinvalley, on the east coast of the Republic of Ireland was used to test a developed methodology aimed at monitoring drought stress, based on the analysis of growth rings obtained by coring. The stand incorporated six plots representing three thinning regimes (light, moderate and heavy) and was planted in the spring of 1943 on a brown earth soil. Radial growth (early- and latewood) was measured for the purpose of this study. A multidisciplinary approach was used to assess historic tree response to climate: specifically, the application of statistical tools such as principal component and canonical correlation analysis to dendrochronology, stable isotopes, ring density proxy, blue reflectance and forest biometrics. Results showed that radial growth was a good proxy for monitoring changes to moisture deficit, while maximum density and blue reflectance were appropriate for assessing changes in accumulated temperature for the growing season. Rainfall also influenced radial growth changes but not significantly, and was a major factor in stable carbon and oxygen discrimination, mostly in the latewood formation phase. Stable oxygen isotope analysis was more accurate than radial growth analysis in drought detection, as it helped detect drought signals in both early- and latewood while radial growth analysis only detected the drought signal in earlywood. Many studies have shown that tree rings provide vital information for marking past climatic events. This work provides a methodology to better identify and understand how commonly measured tree proxies relate to environmental parameters, and can best be used to characterize and pinpoint drought events (variously described using parameters such as like moisture deficit, accumulated temperature, rainfall and potential evaporation).

Drought tolerance strategies highlighted by two Sorghum bicolor races in a dry-down experiment

NARCIS (Netherlands)

Fracasso, Alessandra; Trindade, Luisa; Amaducci, Stefano

2016-01-01

Drought stress is the major environmental stress that affects more and more frequently plant growth and productivity due to the current climate change scenario. Unravelling the physiological mechanism underlying the response of plants to water stress and discover traits related to drought

Arbuscular mycorrhizal symbiosis induces strigolactone biosynthesis under drought and improves drought tolerance in lettuce and tomato

NARCIS (Netherlands)

Ruiz-Lozano, J.M.; Aroca, R.; Zamarreno, A.M.; Molina, S.; Andreo Jimenez, B.; Porcel, R.; Garcia-Mina, J.M.; Ruyter-Spira, C.P.; Lopez-Raez, J.A.

2016-01-01

Arbuscular mycorrhizal (AM) symbiosis alleviates drought stress in plants. However, the intimate mechanisms involved, as well as its effect on the production of signalling molecules associated with the host plant–AM fungus interaction remains largely unknown. In the present work, the effects of

Activated Expression of WRKY57 Confers Drought Tolerance in Arabidopsis

Institute of Scientific and Technical Information of China (English)

Yanjuan Jiang; Gang Liang; Diqiu Yu

2012-01-01

Drought is one of the most serious environmental factors that limit the productivity of agricultural crops worldwide.However,the mechanism underlying drought tolerance in plants is unclear.WRKY transcription factors are known to function in adaptation to abiotic stresses.By screening a pool of WRKY-associated T-DNA insertion mutants,we isolated a gain-of-function mutant,acquired drought tolerance (adt),showing improved drought tolerance.Under drought stress conditions,adt accumulated higher levels of ABA than wild-type plants.Stomatal aperture analysis indicated that adt was more sensitive to ABA than wild-type plants.Molecular genetic analysis revealed that a T-DNA insertion in adt led to activated expression of a WRKY gene that encodes the WRKR57 protein.Constitutive expression of WRKY57 also conferred similar drought tolerance.Consistently with the high ABA content and enhanced drought tolerance,three stress-responsive genes (RD29A,NCED3,and ABA3) were up-regulated in adt.ChIP assays demonstrated that WRKY57 can directly bind the W-box of RD29A and NCED3 promoter sequences.In addition,during ABA treatment,seed germination and early seedling growth of adt were inhibited,whereas,under high osmotic conditions,adt showed a higher seed germination frequency.In summary,our results suggested that the activated expression of WRKY57 improved drought tolerance of Arabidopsis by elevation of ABA levels.Establishment of the functions of WRKY57 will enable improvement of plant drought tolerance through gene manipulation approaches.

Drought and flood effects on macrobenthic communities in the estuary of Australia's largest river system

Science.gov (United States)

Dittmann, Sabine; Baring, Ryan; Baggalley, Stephanie; Cantin, Agnes; Earl, Jason; Gannon, Ruan; Keuning, Justine; Mayo, Angela; Navong, Nathavong; Nelson, Matt; Noble, Warwick; Ramsdale, Tanith

2015-11-01

Estuaries are prone to drought and flood events, which can vary in frequency and intensity depending on water management and climate change. We investigated effects of two different drought and flow situations, including a four year long drought (referred to as Millennium drought) and a major flood event, on the macrobenthic community in the estuary and coastal lagoon of the Murray Mouth and Coorong, where freshwater inflows are strictly regulated. The analysis is based on ten years of annual monitoring of benthic communities and environmental conditions in sediment and water. The objectives were to identify changes in diversity, abundance, biomass and distribution, as well as community shifts and environmental drivers for the respective responses. The Millennium drought led to decreased taxonomic richness, abundance and biomass of macrobenthos as hypersaline conditions developed and water levels dropped. More taxa were found under very high salinities than predicted from the Remane diagram. When a flood event broke the Millennium drought, recovery took longer than from a shorter drought followed by small flows. A flow index was developed to assess the biological response subject to the duration of the preceding drought and flow volumes. The index showed higher taxonomic richness, abundance and biomass at intermediate and more continuous flow conditions. Abundance increased quickly after flows were restored, but the benthic community was initially composed of small bodied organisms and biomass increased only after several years once larger organisms became more abundant. Individual densities and constancy of distribution dropped during the drought for almost all macrobenthic taxa, but recoveries after the flood were taxon specific. Distinct benthic communities were detected over time before and after the drought and flood events, and spatially, as the benthic community in the hypersaline Coorong was split off with a salinity threshold of 64 identified by LINKTREE

Comparative transcriptomic analysis of roots of contrasting Gossypium herbaceum genotypes revealing adaptation to drought

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Ranjan Alok

2012-11-01

Full Text Available Abstract Background Root length and its architecture govern the adaptability of plants to various stress conditions, including drought stress. Genetic variations in root growth, length, and architecture are genotypes dependent. In this study, we compared the drought-induced transcriptome of four genotypes of Gossypium herbaceum that differed in their drought tolerance adaptability. Three different methodologies, namely, microarray, pyrosequencing, and qRT–PCR, were used for transcriptome analysis and validation. Results The variations in root length and growth were found among four genotypes of G.herbaceum when exposed to mannitol-induced osmotic stress. Under osmotic stress, the drought tolerant genotypes Vagad and GujCot-21 showed a longer root length than did by drought sensitive RAHS-14 and RAHS-IPS-187. Further, the gene expression patterns in the root tissue of all genotypes were analyzed. We obtained a total of 794 differentially expressed genes by microarray and 104928 high-quality reads representing 53195 unigenes from the root transcriptome. The Vagad and GujCot-21 respond to water stress by inducing various genes and pathways such as response to stresses, response to water deprivation, and flavonoid pathways. Some key regulatory genes involved in abiotic stress such as AP2 EREBP, MYB, WRKY, ERF, ERD9, and LEA were highly expressed in Vagad and GujCot-21. The genes RHD3, NAP1, LBD, and transcription factor WRKY75, known for root development under various stress conditions, were expressed specifically in Vagad and GujCot-21. The genes related to peroxidases, transporters, cell wall-modifying enzymes, and compatible solutes (amino acids, amino sugars, betaine, sugars, or sugar alcohols were also highly expressed in Vagad and Gujcot-21. Conclusion Our analysis highlights changes in the expression pattern of genes and depicts a small but highly specific set of drought responsive genes induced in response to drought stress. Some of these

Linking events, science and media for flood and drought management

Science.gov (United States)

Ding, M.; Wei, Y.; Zheng, H.; Zhao, Y.

2017-12-01

Throughout history, floods and droughts have been closely related to the development of human riparian civilization. The socio-economic damage caused by floods/droughts appears to be on the rise and the frequency of floods/droughts increases due to global climate change. In this paper, we take a fresh perspective to examine the (dis)connection between events (floods and droughts), research papers and media reports in globally 42 river basins between 1990 and 2012 for better solutions in floods and droughts management. We collected hydrological data from NOAA/ESPL Physical Sciences Division (PSD) and CPC Merged Analysis of Precipitation (CMAP), all relevant scientific papers from Web of Science (WOS) and media records from Emergency Events Database (EM-DAT) during the study period, presented the temporal variability at annual level of these three groups of data, and analysed the (connection) among these three groups of data in typical river basins. We found that 1) the number of flood related reports on both media and research is much more than those on droughts; 2) the concerns of media reports just focused on partial topics (death, severity and damage) and partial catchments (Mediterranean Sea and Nile River); 3) the scientific contribution on floods and droughts were limited within some river basins such as Nile River Basin, Parana River Basin, Savannah River Basin and Murray-Darling River Basin; 4) the scientific contribution on floods and droughts were limited within only a few of disciplines such as Geology, Environmental Sciences & Ecology, Agriculture, Engineering and Forestry. It is recommended that multiple disciplinary contribution and collaboration should be promoted to achieve comprehensive flood/drought management, and science and media should interactively play their valuable roles and in flood/drought issues. Keywords: Floods, droughts, events, science, media, flood and drought management

The transcriptional regulatory network in the drought response and its crosstalk in abiotic stress responses including drought, cold and heat

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Kazuo eNakashima

2014-05-01

Full Text Available Drought negatively impacts plant growth and the productivity of crops around the world. Understanding the molecular mechanisms in the drought response is important for improvement of drought tolerance using molecular techniques. In plants, abscisic acid (ABA is accumulated under osmotic stress conditions caused by drought, and has a key role in stress responses and tolerance. Comprehensive molecular analyses have shown that ABA regulates the expression of many genes under osmotic stress conditions, and the ABA-responsive element (ABRE is the major cis-element for ABA-responsive gene expression. Transcription factors (TFs are master regulators of gene expression. ABRE-binding protein (AREB and ABRE-binding factor (ABF TFs control gene expression in an ABA-dependent manner. SNF1-related protein kinases 2, group A 2C-type protein phosphatases, and ABA receptors were shown to control the ABA signaling pathway. ABA-independent signaling pathways such as dehydration-responsive element-binding protein (DREB TFs and NAC TFs are also involved in stress responses including drought, heat and cold. Recent studies have suggested that there are interactions between the major ABA signaling pathway and other signaling factors in stress responses. The important roles of these transcription factors in crosstalk among abiotic stress responses will be discussed. Control of ABA or stress signaling factor expression can improve tolerance to environmental stresses. Recent studies using crops have shown that stress-specific overexpression of TFs improves drought tolerance and grain yield compared with controls in the field.

The transcriptional regulatory network in the drought response and its crosstalk in abiotic stress responses including drought, cold, and heat.

Science.gov (United States)

Nakashima, Kazuo; Yamaguchi-Shinozaki, Kazuko; Shinozaki, Kazuo

2014-01-01

Drought negatively impacts plant growth and the productivity of crops around the world. Understanding the molecular mechanisms in the drought response is important for improvement of drought tolerance using molecular techniques. In plants, abscisic acid (ABA) is accumulated under osmotic stress conditions caused by drought, and has a key role in stress responses and tolerance. Comprehensive molecular analyses have shown that ABA regulates the expression of many genes under osmotic stress conditions, and the ABA-responsive element (ABRE) is the major cis-element for ABA-responsive gene expression. Transcription factors (TFs) are master regulators of gene expression. ABRE-binding protein and ABRE-binding factor TFs control gene expression in an ABA-dependent manner. SNF1-related protein kinases 2, group A 2C-type protein phosphatases, and ABA receptors were shown to control the ABA signaling pathway. ABA-independent signaling pathways such as dehydration-responsive element-binding protein TFs and NAC TFs are also involved in stress responses including drought, heat, and cold. Recent studies have suggested that there are interactions between the major ABA signaling pathway and other signaling factors in stress responses. The important roles of these TFs in crosstalk among abiotic stress responses will be discussed. Control of ABA or stress signaling factor expression can improve tolerance to environmental stresses. Recent studies using crops have shown that stress-specific overexpression of TFs improves drought tolerance and grain yield compared with controls in the field.

CONSIDERATIONS ON THE DROUGHT PHENOMENON IN CLUJ COUNTY

Directory of Open Access Journals (Sweden)

CORNEL BLAGA

2011-03-01

Full Text Available Considerations on the drought phenomenon in Cluj County. Cluj county area is 6674 km², and is located in the northwestern part of Romania. The climate is temperate continental with oceanic influences, relatively humid, but there are also periods of drought and even years with deficient rainfall, as there are periods of excess rainfall. Dryness and drought phenomena are caused by cosmic, climatic, hydrological (groundwater depth, the existence of surface water sources factors, features of the underlying surface, vegetation coverage, soil texture and structure. The relief determines a climate elevation with differences in terms of precipitation and temperatures quantities. To calculate the dryness degree of the climate at weather stations in the Cluj county, the Emmanuel de Martonne aridity index was used. Drought do not induce into the substrate the geomorphologic processes per se, however, they pave the way for starting the deflation process, surface erosion and ravine, by reducing the cohesion between the particles and the formation of deep cracks in the soil and even rock. In these climatic conditions, droughts are less frequent in the county of Cluj, in relation to the extra-Carpathian regions and are distributed unevenly across the county. The number of periods of drought decreases with the increase of the altitude, from an average of 2.6 drought periods a year at Dej (altitude of 232 m to an annual average of 0.3 draught periods at Vlădeasa Peak (altitude of 1836 m.

Drought in a human-modified world: reframing drought definitions, understanding, and analysis approaches

Science.gov (United States)

Van Loon, Anne F.; Stahl, Kerstin; Di Baldassarre, Giuliano; Clark, Julian; Rangecroft, Sally; Wanders, Niko; Gleeson, Tom; Van Dijk, Albert I. J. M.; Tallaksen, Lena M.; Hannaford, Jamie; Uijlenhoet, Remko; Teuling, Adriaan J.; Hannah, David M.; Sheffield, Justin; Svoboda, Mark; Verbeiren, Boud; Wagener, Thorsten; Van Lanen, Henny A. J.

2016-09-01

In the current human-modified world, or Anthropocene, the state of water stores and fluxes has become dependent on human as well as natural processes. Water deficits (or droughts) are the result of a complex interaction between meteorological anomalies, land surface processes, and human inflows, outflows, and storage changes. Our current inability to adequately analyse and manage drought in many places points to gaps in our understanding and to inadequate data and tools. The Anthropocene requires a new framework for drought definitions and research. Drought definitions need to be revisited to explicitly include human processes driving and modifying soil moisture drought and hydrological drought development. We give recommendations for robust drought definitions to clarify timescales of drought and prevent confusion with related terms such as water scarcity and overexploitation. Additionally, our understanding and analysis of drought need to move from single driver to multiple drivers and from uni-directional to multi-directional. We identify research gaps and propose analysis approaches on (1) drivers, (2) modifiers, (3) impacts, (4) feedbacks, and (5) changing the baseline of drought in the Anthropocene. The most pressing research questions are related to the attribution of drought to its causes, to linking drought impacts to drought characteristics, and to societal adaptation and responses to drought. Example questions include (i) What are the dominant drivers of drought in different parts of the world? (ii) How do human modifications of drought enhance or alleviate drought severity? (iii) How do impacts of drought depend on the physical characteristics of drought vs. the vulnerability of people or the environment? (iv) To what extent are physical and human drought processes coupled, and can feedback loops be identified and altered to lessen or mitigate drought? (v) How should we adapt our drought analysis to accommodate changes in the normal situation (i.e. what

Modulation of Antioxidant Defense System Is Associated with Combined Drought and Heat Stress Tolerance in Citrus

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Sara I. Zandalinas

2017-06-01

Full Text Available Drought and high temperatures are two major abiotic stress factors that often occur simultaneously in nature, affecting negatively crop performance and yield. Moreover, these environmental challenges induce oxidative stress in plants through the production of reactive oxygen species (ROS. Carrizo citrange and Cleopatra mandarin are two citrus genotypes with contrasting ability to cope with the combination of drought and heat stress. In this work, a direct relationship between an increased antioxidant activity and stress tolerance is reported. According to our results, the ability of Carrizo plants to efficiently coordinate superoxide dismutase (SOD, ascorbate peroxidase (APX, catalase (CAT, and glutathione reductase (GR activities involved in ROS detoxification along with the maintenance of a favorable GSH/GSSG ratio could be related to their relative tolerance to this stress combination. On the other hand, the increment of SOD activity and the inefficient GR activation along with the lack of CAT and APX activities in Cleopatra plants in response to the combination of drought and heat stress, could contribute to an increased oxidative stress and the higher sensibility of this citrus genotype to this stress combination.

The Destabilization of Protected Soil Organic Carbon Following Experimental Drought at the Pore and Core scale

Science.gov (United States)

Smith, A. P.; Bond-Lamberty, B. P.; Tfaily, M. M.; Todd-Brown, K. E.; Bailey, V. L.

2015-12-01

The movement of water and solutes through the pore matrix controls the distribution and transformation of carbon (C) in soils. Thus, a change in the hydrologic connectivity, such as increased saturation, disturbance or drought, may alter C mineralization and greenhouse gas (GHG) fluxes to the atmosphere. While these processes occur at the pore scale, they are often investigated at coarser scale. This project investigates pore- and core-scale soil C dynamics with varying hydrologic factors (simulated precipitation, groundwater-led saturation, and drought) to assess how climate-change induced shifts in hydrologic connectivity influences the destabilization of protected C in soils. Surface soil cores (0-15 cm depth) were collected from the Disney Wilderness Preserve, Florida, USA where water dynamics, particularly water table rise and fall, appear to exert a strong control on the emissions of GHGs and the persistence of soil organic matter in these soils. We measured CO2 and CH4 from soils allowed to freely imbibe water from below to a steady state starting from either field moist conditions or following experimental drought. Parallel treatments included the addition of similar quantities of water from above to simulate precipitation. Overall respiration increased in soil cores subjected to drought compared to field moist cores independent of wetting type. Cumulative CH4 production was higher in drought-induced soils, especially in the soils subjected to experimental groundwater-led saturation. Overall, the more C (from CO2 and CH4) was lost in drought-induced soils compared to field moist cores. Our results indicate that future drought events could have profound effects on the destabilization of protected C, especially in groundwater-fed soils. Our next steps focus on how to accurately capture drought-induced C destabilization mechanisms in earth system models.

Evaluation of physiological screening techniques for drought ...

African Journals Online (AJOL)

This paper summarizes the results of a project aimed to evaluate the use of physiological traits (such as canopy temperature and chlorophyll content) in determining drought tolerance of durum wheat genotypes under a variety of environmental conditions. Six durum wheat genotypes were planted in rainfed and ...

Analysis of meteorological drought for Dagua river basin, Valle del Cauca, Colombia

Directory of Open Access Journals (Sweden)

Nathalia González López

2016-06-01

Full Text Available Context: Extreme climatic events causes great challenges for social, economic and environmental sustainability of a region. Droughts affect agricultural activities significantly thus endangering the livelihoods and food security of rural populations, this is especially crucial for developing countries. The objective of this study is to characterize meteorological drought in Dagua river basin, Valle del Cauca. Method:  Intensity, magnitude, duration and frequency of drought events was estimated using the Standardized Precipitation Index (SPI, for semi-annual and annual groupings with records of 19 stations, during the period 1982-2011 Results: At least one drought was identified in each series; the area near to the subxerofític Basin region, exhibits more frequency of extremely strong drought and lower threshold of minimum precipitation; the largest percentage of spatial coverage of drought coincides with El Niño phenomena events, such as those that occurred in 91-92 to 09-10. Conclusions: The results obtained provide an approach for prediction and characterization of drought, and offer inputs to generate strategies for planning and mitigation of their impacts.

Dissecting rice polyamine metabolism under controlled long-term drought stress.

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Phuc Thi Do

Full Text Available A selection of 21 rice cultivars (Oryza sativa L. ssp. indica and japonica was characterized under moderate long-term drought stress by comprehensive physiological analyses and determination of the contents of polyamines and selected metabolites directly related to polyamine metabolism. To investigate the potential regulation of polyamine biosynthesis at the transcriptional level, the expression of 21 genes encoding enzymes involved in these pathways were analyzed by qRT-PCR. Analysis of the genomic loci revealed that 11 of these genes were located in drought-related QTL regions, in agreement with a proposed role of polyamine metabolism in rice drought tolerance. The cultivars differed widely in their drought tolerance and parameters such as biomass and photosynthetic quantum yield were significantly affected by drought treatment. Under optimal irrigation free putrescine was the predominant polyamine followed by free spermidine and spermine. When exposed to drought putrescine levels decreased markedly and spermine became predominant in all cultivars. There were no correlations between polyamine contents and drought tolerance. GC-MS analysis revealed drought-induced changes of the levels of ornithine/arginine (substrate, substrates of polyamine synthesis, proline, product of a competing pathway and GABA, a potential degradation product. Gene expression analysis indicated that ADC-dependent polyamine biosynthesis responded much more strongly to drought than the ODC-dependent pathway. Nevertheless the fold change in transcript abundance of ODC1 under drought stress was linearly correlated with the drought tolerance of the cultivars. Combining metabolite and gene expression data, we propose a model of the coordinate adjustment of polyamine biosynthesis for the accumulation of spermine under drought conditions.

A Novel Non-coding RNA Regulates Drought Stress Tolerance in Arabidopsis thaliana

KAUST Repository

Albesher, Nour H.

2014-05-01

Drought (soil water deficit) as a major adverse environmental condition can result in serious reduction in plant growth and crop production. Plants respond and adapt to drought stresses by triggering various signalling pathways leading to physiological, metabolic and developmental changes that may ultimately contribute to enhanced tolerance to the stress. Here, a novel non-coding RNA (ncRNA) involved in plant drought stress tolerance was identified. We showed that increasing the expression of this ncRNA led to enhanced sensitivity during seed germination and seedling growth to the phytohormone abscisic acid. The mutant seedlings are also more sensitive to osmotic stress inhibition of lateral root growth. Consistently, seedlings with enhanced expression of this ncRNA exhibited reduced transiprational water loss and were more drought-tolerant than the wild type. Future analyses of the mechanism for its role in drought tolerance may help us to understand how plant drought tolerance could be further regulated by this novel ncRNA.

Global Synthesis of Drought Effects on Food Legume Production.

Science.gov (United States)

Daryanto, Stefani; Wang, Lixin; Jacinthe, Pierre-André

2015-01-01

Food legume crops play important roles in conservation farming systems and contribute to food security in the developing world. However, in many regions of the world, their production has been adversely affected by drought. Although water scarcity is a severe abiotic constraint of legume crops productivity, it remains unclear how the effects of drought co-vary with legume species, soil texture, agroclimatic region, and drought timing. To address these uncertainties, we collected literature data between 1980 and 2014 that reported monoculture legume yield responses to drought under field conditions, and analyzed this data set using meta-analysis techniques. Our results showed that the amount of water reduction was positively related with yield reduction, but the extent of the impact varied with legume species and the phenological state during which drought occurred. Overall, lentil (Lens culinaris), groundnut (Arachis hypogaea), and pigeon pea (Cajanus cajan) were found to experience lower drought-induced yield reduction compared to legumes such as cowpea (Vigna unguiculata) and green gram (Vigna radiate). Yield reduction was generally greater when legumes experienced drought during their reproductive stage compared to during their vegetative stage. Legumes grown in soil with medium texture also exhibited greater yield reduction compared to those planted on soil of either coarse or fine texture. In contrast, regions and their associated climatic factors did not significantly affect legume yield reduction. In the face of changing climate, our study provides useful information for agricultural planning and research directions for development of drought-resistant legume species to improve adaptation and resilience of agricultural systems in the drought-prone regions of the world.

Drought-Stressed Tomato Plants Trigger Bottom-Up Effects on the Invasive Tetranychus evansi.

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Miguel G Ximénez-Embún

Full Text Available Climate change will bring more drought periods that will have an impact on the irrigation practices of some crops like tomato, from standard water regime to deficit irrigation. This will promote changes in plant metabolism and alter their interactions with biotic stressors. We have tested if mild or moderate drought-stressed tomato plants (simulating deficit irrigation have an effect on the biological traits of the invasive tomato red spider mite, Tetranychus evansi. Our data reveal that T evansi caused more leaf damage to drought-stressed tomato plants (≥1.5 fold for both drought scenarios. Mite performance was also enhanced, as revealed by significant increases of eggs laid (≥2 fold at 4 days post infestation (dpi, and of mobile forms (≥2 fold and 1.5 fold for moderate and mild drought, respectively at 10 dpi. The levels of several essential amino acids (histidine, isoleucine, leucine, tyrosine, valine and free sugars in tomato leaves were significantly induced by drought in combination with mites. The non-essential amino acid proline was also strongly induced, stimulating mite feeding and egg laying when added to tomato leaf disks at levels equivalent to that estimated on drought-infested tomato plants at 10 dpi. Tomato plant defense proteins were also affected by drought and/or mite infestation, but T. evansi was capable of circumventing their potential adverse effects. Altogether, our data indicate that significant increases of available free sugars and essential amino acids, jointly with their phagostimulant effect, created a favorable environment for a better T. evansi performance on drought-stressed tomato leaves. Thus, drought-stressed tomato plants, even at mild levels, may be more prone to T evansi outbreaks in a climate change scenario, which might negatively affect tomato production on area-wide scales.

TaSK5, an abiotic stress-inducible GSK3/shaggy-like kinase from wheat, confers salt and drought tolerance in transgenic Arabidopsis.

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Christov, Nikolai Kirilov; Christova, Petya Koeva; Kato, Hideki; Liu, Yuelin; Sasaki, Kentaro; Imai, Ryozo

2014-11-01

A novel cold-inducible GSK3/shaggy-like kinase, TaSK5, was isolated from winter wheat using a macroarray-based differential screening approach. TaSK5 showed high similarity to Arabidopsis subgroup I GSK3/shaggy-like kinases ASK-alpha, AtSK-gamma and ASK-epsilon. RNA gel blot analyses revealed TaSK5 induction by cold and NaCl treatments and to a lesser extent by drought treatment. TaSK5 functionally complemented the cold- and salt-sensitive phenotypes of a yeast GSK3/shaggy-like kinase mutant, △mck1. Transgenic Arabidopsis plants overexpressing TaSK5 cDNA showed enhanced tolerance to salt and drought stresses. By contrast, the tolerance of the transgenic plants to freezing stress was not altered. Microarray analysis revealed that a number of abiotic stress-inducible genes were constitutively induced in the transgenic Arabidopsis plants, suggesting that TaSK5 may function in a novel signal transduction pathway that appears to be unrelated to DREB1/CBF regulon and may involve crosstalk between abiotic and hormonal signals. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

An assessment of global meteorological droughts based on HAPPI experiments

Science.gov (United States)

Liu, Wenbin; Sun, Fubao; Lim, Wee Ho; Zhang, Jie

2017-04-01

Droughts caused water shortages could lead to serious consequences on the socioeconomic and environmental well-being. In the context of changing climate, droughts monitoring, attributions and impact assessments have been performed using observations (e.g., Sun et al., 2012; Zhang et al., 2016) and climate model projections (e.g., Liu et al., 2016, 2017); with expectation that such scientific knowledge would feed into long-term adaptation and mitigation plans to tackle potentially unfavorable future drought impacts in a warming world. Inspired by the 2015 Paris Agreement, the HAPPI (Half a degree Additional warming, Projections, Prognosis and Impacts) experiments were set up to better inform international policymakers about the socioeconomic and environmental impacts under less severe global warming conditions. This study aims to understand the potential shift in meteorological droughts from the past into the future on a global scale. Based on the HAPPI data, we evaluate the change in drought related indices (i.e., PET/P, PDSI) from the past to the future scenarios (1.5 and 2 degrees Celsius warming). Here we present some early results (MIROC5 as demonstration) on identified hotspots and discuss the differences in severity of droughts between these warming worlds and associated consequences. References: Liu W, and Sun F, 2017. Projecting and attributing future changes of evaporative demand over China in CMIP5 climate models, Journal of Hydrometeorology, doi: 10.1175/JHM-D-16-0204.1 Liu W, and Sun F, 2016. Assessing estimates of evaporative demand in climate models using observed pan evaporation over China. Journal of Geophysical Research-Atmosphere 121, 8329-8349 Zhang J, Sun F, Xu J, Chen Y, Sang Y, -F, and Liu C, 2016. Dependence of trends in and sensitivity of drought over China (1961-2013) on potential evaporation model. Geophysical Research Letters 43, 206-213 Sun F, Roderick M, Farquhar G, 2012. Changes in the variability of global land precipitation

The effect of severe drought and management after drought on the ...

African Journals Online (AJOL)

The False Thornveld of the Eastern Cape experienced a particularly intense drought during the 1982/1983 growing season. Extensive grass mortality took place during the drought. After the drought, recovery was particularly sensitive to the post-drought management treatment applied. Veld that was grazed immediately ...

Drought stress tolerance strategies revealed by RNA-Seq in two sorghum genotypes with contrasting WUE

NARCIS (Netherlands)

Fracasso, Alessandra; Trindade, Luisa M.; Amaducci, Stefano

2016-01-01

Background: Drought stress is the major environmental stress that affects plant growth and productivity. It triggers a wide range of responses detectable at molecular, biochemical and physiological levels. At the molecular level the response to drought stress results in the differential

Differential accumulation of dehydrins in response to water stress for hybrid and common bermudagrass genotypes differing in drought tolerance.

Science.gov (United States)

Hu, Longxing; Wang, Zhaolong; Du, Hongmei; Huang, Bingru

2010-01-15

Expression of dehydrin proteins may be induced or enhanced by environmental stresses that lead to cell dehydration. The objective of the this study was to investigate genetic variation in dehydrin protein accumulation in response to drought stress of whole-plants or dehydration of detached leaves and to identify dehydrins differentially expressed in bermudagrass (Cynodon spp.) genotypes differing in drought tolerance. Plants of four hybrid bermudagrass (Cynodondactylon L. xCynodontransvaalensis L.) ('Tifway', 'Tifdwarf', 'Tifeagle', 'Kan1') and four common bermudagrass (Cynodon dactylon) ('C299', 'Sportbermuda', 'H10', and 'H19') genotypes were subjected to 14d of drought stress and detached leaves of two genotypes were exposed to dehydration in growth chambers. Turf quality and leaf relative water content (RWC) decreased while electrolyte leakage (EL) increased during whole-plant drought stress for all genotypes, with more pronounced changes in each parameter for 'C299' and 'Tifeagle' than those for other genotypes ('Tifway', 'Kan 1', 'Sportbermuda', 'H10', and H19'), suggesting that the former two genotypes were more sensitive to drought stress than the other genotypes. During dehydration of detached leaves, relative water loss rate (RWL) was significantly lower in drought-tolerant 'Tifway' than in drought-sensitive 'C299'. Immunoblotting analysis indicated that no dehydrin polypeptides were detected in all genotypes under well-watered conditions. A 24-kDa polypeptide was detected in 'C299' at 6 d of drought, but not in the other genotypes. The dehydrin polypeptides of about 14-74kDa accumulated at 10d of drought stress and in a range of RWL for detached leaves, and two dehydrins (31 and 40kDa) exhibited differential accumulation in the drought-sensitive 'C299' and tolerant 'Tifway', as demonstrated by the whole-plant drought responses. The 31-kDa dehydrin polypeptide was present only in 'Tifway' and 'H19' at 10d of drought stress, and accumulated with the

An index for drought induced financial risk in the mining industry

Science.gov (United States)

Bonnafous, L.; Lall, U.; Siegel, J.

2017-02-01

Water scarcity has emerged as a potential risk for mining operations. High capital spending for desalination and water conflicts leading to asset stranding have recently occurred. Investors in mining companies are interested in the exposure to such risks across portfolios of mining assets (whether the practical at-site consequences are foregone production, higher OPEX and CAPEX and ensuing lost revenues, or asset-stranding). In this paper, an index of the potential financial exposure of a portfolio is developed and its application is illustrated. Since the likely loss at each mine is hard to estimate a priori, one needs a proxy for potential loss. The index considers drought duration, severity and frequency (defined by a return-level in years) at each mining asset, and provides a measure of financial exposure through weighing of production or Net Asset Value. Changes in human needs are not considered, but are relevant, and could be incorporated if global data on mine and other water use were available at the appropriate resolution. Potential for contemporaneous drought incidence across sites in a portfolio is considered specifically. Through an appropriate choice of drought thresholds, an analyst can customize a scenario to assess potential losses in production value or profits, or whether conflicts could emerge that would lead to stranded assets or capital expenditure to secure alternate water supplies. Global climate data sets that allow a customized development of such an index are identified, and selected mining company portfolios are scored as to the risk associated with one publicly available drought index.

A cross-scale approach to understand drought-induced variability of sagebrush ecosystem productivity

Science.gov (United States)

Assal, T.; Anderson, P. J.

2016-12-01

Sagebrush (Artemisia spp.) mortality has recently been reported in the Upper Green River Basin (Wyoming, USA) of the sagebrush steppe of western North America. Numerous causes have been suggested, but recent drought (2012-13) is the likely mechanism of mortality in this water-limited ecosystem which provides critical habitat for many species of wildlife. An understanding of the variability in patterns of productivity with respect to climate is essential to exploit landscape scale remote sensing for detection of subtle changes associated with mortality in this sparse, uniformly vegetated ecosystem. We used the standardized precipitation index to characterize drought conditions and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery (250-m resolution) to characterize broad characteristics of growing season productivity. We calculated per-pixel growing season anomalies over a 16-year period (2000-2015) to identify the spatial and temporal variability in productivity. Metrics derived from Landsat satellite imagery (30-m resolution) were used to further investigate trends within anomalous areas at local scales. We found evidence to support an initial hypothesis that antecedent winter drought was most important in explaining reduced productivity. The results indicate drought effects were inconsistent over space and time. MODIS derived productivity deviated by more than four standard deviations in heavily impacted areas, but was well within the interannual variability in other areas. Growing season anomalies highlighted dramatic declines in productivity during the 2012 and 2013 growing seasons. However, large negative anomalies persisted in other areas during the 2014 growing season, indicating lag effects of drought. We are further investigating if the reduction in productivity is mediated by local biophysical properties. Our analysis identified spatially explicit patterns of ecosystem properties altered by severe drought which are consistent with

Physiological and molecular responses of springtails exposed to phenanthrene and drought

International Nuclear Information System (INIS)

Holmstrup, Martin; Slotsbo, Stine; Schmidt, Stine N.; Mayer, Philipp; Damgaard, Christian; Sørensen, Jesper G.

2014-01-01

Interaction between effects of hazardous chemicals in the environment and adverse climatic conditions is a problem that receives increased attention in the light of climate change. We studied interactive effects of phenanthrene and drought using a test system in which springtails (Folsomia candida Willem) were concurrently exposed to a sublethal phenanthrene level via passive dosing from silicone (chemical activity of 0.010), and sublethal drought from aqueous NaCl solutions (water activity of 0.988). Previous studies have shown that the combined effects of high levels of phenanthrene and drought, respectively, interact synergistically when using lethality as an end-point. Here, we hypothesized that phenanthrene interferes with physiological mechanisms involved in drought tolerance, and that drought influences detoxification of phenanthrene. However, this hypothesis was not supported by data since phenanthrene had no effect on drought-protective accumulation of myo-inositol, and normal water conserving mechanisms of F. candida were functioning despite the near-lethal concentrations of the toxicant. Further, detoxifying induction of cytochrome P 450 and glutathione-S-transferase was not impeded by drought. Both phenanthrene and drought induced transcription of heat shock protein (hsp70) and the combined effect of the two stressors on hsp70 transcription was additive, suggesting that the cellular stress and lethality imposed by these levels of phenanthrene and drought were also additive. -- Highlights: • New methods are needed for physiological studies of multiple stressor effects. • Springtails were exposed to combined stress from phenanthrene and drought. • Induction of CYP 450 and glutathione-S-transferase was not impeded by drought. • Drought-protective accumulation of myo-inositol was not challenged by phenanthrene. • The combined effect of phenanthrene and drought on hsp70 transcription was additive. -- Drought does not hamper detoxification of

Effects of drought season length on live moisture content dynamic in Mediterranean shrubs: 8 years of data

Science.gov (United States)

Pellizzaro, Grazia; Ventura, Andrea; Bortolu, Sara; Duce, Pierpaolo

2017-04-01

Mediterranean shrubs are an important component of Mediterranean vegetation communities. In this kind of vegetation, live fuel is a relevant component of the available fuel which catches fire and, consequently, its water content plays an important role in determining fire occurrence and spread. In live plant, water content patterns are related to both environmental conditions (e.g. meteorological variables, soil water availability) and ecophysiological characteristics of the plant species. According to projections on future climate, an increase in risk of summer droughts is likely to take place in Southern Europe. More prolonged drought seasons induced by climatic changes are likely to influence general flammability characteristics of fuel. In addition, variations in precipitation and mean temperature could directly affect fuel water status and length of critical periods of high ignition danger for Mediterranean ecosystems. The aims of this work were to analyse the influence of both weather seasonality and inter-annual weather variability on live fuel moisture content within and among some common Mediterranean species, and to investigate the effects of prolonged drought season on live moisture content dynamic. The study was carried out in North Sardinia (Italy). Measurements of LFMC seasonal pattern of two really common and flammable Mediterranean shrub species (Cistus monspeliensis and Rosmarinus officinalis) were performed periodically for 8 years. Meteorological variables were also recorded. Relationships between live fuel moisture content and environmental conditions (i.e. rainfall, air temperature and soil moisture) were investigated and effects of different lengths of drought season on LFMC pattern were analysed. Results showed that distribution and amount of rainfall affected seasonal variation of live fuel moisture content. In particular more prolonged drought seasons caused a longer period in which LFMC was below 95 -100% that is commonly considered as

Drought, Climate Change and the Canadian Prairies

Science.gov (United States)

Stewart, R. E.

2010-03-01

employment losses exceeded 41,000 jobs for 2001 and 2002. This drought also contributed to a negative or zero net farm income for several provinces for the first time in 25 years with agricultural production over Canada dropping an estimated 3.6 billion in 2001/2002. Previously reliable water supplies such as streams, wetlands, dugouts, reservoirs, and groundwater were placed under stress and often failed. Despite their enormous economic, environmental, and societal impacts, there has never been a coordinated and integrated drought research program in Canada. To begin to address these issues related to drought, the Drought Research Initiative, DRI was established. The overall objective of DRI is "to better understand the physical characteristics of and processes influencing Canadian Prairie droughts, and to contribute to their better prediction, through a focus on the recent severe drought that began in 1999 and largely ended in 2005". DRI is focused on five research objectives: 1. Quantify the physical features of this recent drought 2. Improve the understanding of the processes and feedbacks governing the formation, evolution, cessation and structure of the drought 3. Assess and reduce uncertainties in the prediction of drought and its structure 4. Compare the similarities and differences of the recent drought to previous and future droughts 5. Apply progress to address critical issues of importance to society Major progress is being made within each of these research areas. These coordinated studies furthermore represent an essential step towards our ultimate goal which is to better assess whether there will be more droughts in the future over this region due to climate change, what features these droughts will exhibit, and how we can best prepare for them. The focus of these activities is on changes to occur over the next several decades and significant progress is being made in addressing these issues as well. The purpose of this presentation is to provide an overview

NAC transcription factor JUNGBRUNNEN1 enhances drought tolerance in tomato

KAUST Repository

Thirumalaikumar, Venkatesh P.

2017-06-22

Water deficit (drought stress) massively restricts plant growth and the yield of crops; reducing the deleterious effects of drought is therefore of high agricultural relevance. Drought triggers diverse cellular processes including the inhibition of photosynthesis, the accumulation of cell-damaging reactive oxygen species, and gene expression reprogramming, besides others. Transcription factors (TF) are central regulators of transcriptional reprogramming and expression of many TF genes is affected by drought, including members of the NAC family. Here, we identify the NAC factor JUNGBRUNNEN1 (JUB1) as a regulator of drought tolerance in tomato (Solanum lycopersicum). Expression of tomato JUB1 (SlJUB1) is enhanced by various abiotic stresses, including drought. Inhibiting SlJUB1 by virus-induced gene silencing drastically lowers drought tolerance concomitant with an increase in ion leakage, an elevation of hydrogen peroxide (H2 O2 ) levels, and a decrease of the expression of various drought-responsive genes. In contrast, overexpression of AtJUB1 from Arabidopsis thaliana increases drought tolerance in tomato, alongside with a higher relative leaf water content during drought and reduced H2 O2 levels. AtJUB1 was previously shown to stimulate expression of DREB2A, a TF involved in drought responses, and of the DELLA genes GAI and RGL1. We show here that SlJUB1 similarly controls the expression of the tomato orthologs SlDREB1, SlDREB2, and SlDELLA. Furthermore, AtJUB1 directly binds to the promoters of SlDREB1, SlDREB2 and SlDELLA in tomato. Our study highlights JUB1 as a transcriptional regulator of drought tolerance and suggests considerable conservation of the abiotic stress-related gene regulatory networks controlled by this NAC factor between Arabidopsis and tomato. This article is protected by copyright. All rights reserved.

Regional applicability of seven meteorological drought indices in China

Institute of Scientific and Technical Information of China (English)

YANG Qing; LI MingXing; ZHENG ZiYan; MA ZhuGuo

2017-01-01

The definition of a drought index is the foundation of drought research.However,because of the complexity of drought,there is no a unified drought index appropriate for different drought types and objects at the same time.Therefore,it is crucial to determine the regional applicability of various drought indices.Using terrestrial water storage obtained from the Gravity Recovery And Climate Experiment,and the observed soil moisture and streamflow in China,we evaluated the regional applicability of seven meteorological drought indices:the Palmer Drought Severity Index(PDSI),modified PDSI(PDSI_CN) based on observations in China,self-calibrating PDSI(scPDSI),Surface Wetness Index(SWI),Standardized Precipitation Index(SPI),Standardized Precipitation Evapotranspiration Index(SPEI),and soil moisture simulations conducted using the community land model driven by observed atmospheric forcing(CLM3.5/ObsFC).The results showed that the scPDSI is most appropriate for China.However,it should be noted that the scPDSI reduces the value range slightly compared with the PDSI and PDSI_CN;thus,the classification of dry and wet conditions should be adjusted accordingly.Some problems might exist when using the PDSI and PDSI_CN in humid and arid areas because of the unsuitability of empiricalparameters.The SPI and SPEI are more appropriate for humid areas than arid and semiarid areas.This is because contributions of temperature variation to drought are neglected in the SPI,but overestimated in the SPEI,when potential evapotranspiration is estimated by the Thornthwaite method in these areas.Consequently,the SPI and SPEI tend to induce wetter and drier results,respectively.The CLM3.5/ObsFC is suitable for China before 2000,but not for arid and semiarid areas after 2000.Consistent with other drought indices,the SWI shows similar interannual and decadal change characteristics in detecting annual dry/wet variations.Although the long-term trends of drought areas in China detected by these seven

A chloroplast-localized and auxin-induced glutathione S-transferase from phreatophyte Prosopis juliflora confer drought tolerance on tobacco.

Science.gov (United States)

George, Suja; Venkataraman, Gayatri; Parida, Ajay

2010-03-01

Plant growth and productivity are adversely affected by various abiotic stress factors. In our previous study, we used Prosopis juliflora, a drought-tolerant tree species of Fabaceae, as a model plant system for mining genes functioning in abiotic stress tolerance. Large-scale random EST sequencing from a cDNA library obtained from drought-stressed leaves of 2-month-old P. juliflora plants resulted in identification of three different auxin-inducible glutathione S-transferases. In this paper, we report the cellular localization and the ability to confer drought tolerance in transgenic tobacco of one of these GSTs (PjGSTU1). PjGSTU1 was overexpressed in Escherichia coli and GST and GPX activities in total protein samples were assayed and compared with controls. The results indicated that PjGSTU1 protein forms a functional homo-dimer in recombinant bacteria with glutathione transferase as well as glutathione peroxidase activities. PjGSTU1 transgenic tobacco lines survived better under conditions of 15% PEG stress compared with control un-transformed plants. In vivo localization studies for PjGSTU1 using GFP fusion revealed protein localization in chloroplasts of transgenic plants. The peroxidase activity of PjGSTU1 and its localization in the chloroplast indicates a possible role for PjGSTU1 in ROS removal. Copyright 2009 Elsevier GmbH. All rights reserved.

Global Synthesis of Drought Effects on Food Legume Production.

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Stefani Daryanto

Full Text Available Food legume crops play important roles in conservation farming systems and contribute to food security in the developing world. However, in many regions of the world, their production has been adversely affected by drought. Although water scarcity is a severe abiotic constraint of legume crops productivity, it remains unclear how the effects of drought co-vary with legume species, soil texture, agroclimatic region, and drought timing. To address these uncertainties, we collected literature data between 1980 and 2014 that reported monoculture legume yield responses to drought under field conditions, and analyzed this data set using meta-analysis techniques. Our results showed that the amount of water reduction was positively related with yield reduction, but the extent of the impact varied with legume species and the phenological state during which drought occurred. Overall, lentil (Lens culinaris, groundnut (Arachis hypogaea, and pigeon pea (Cajanus cajan were found to experience lower drought-induced yield reduction compared to legumes such as cowpea (Vigna unguiculata and green gram (Vigna radiate. Yield reduction was generally greater when legumes experienced drought during their reproductive stage compared to during their vegetative stage. Legumes grown in soil with medium texture also exhibited greater yield reduction compared to those planted on soil of either coarse or fine texture. In contrast, regions and their associated climatic factors did not significantly affect legume yield reduction. In the face of changing climate, our study provides useful information for agricultural planning and research directions for development of drought-resistant legume species to improve adaptation and resilience of agricultural systems in the drought-prone regions of the world.

Drought, pollen and nectar availability, and pollination success.

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Waser, Nickolas M; Price, Mary V

2016-06-01

Pollination success of animal-pollinated flowers depends on rate of pollinator visits and on pollen deposition per visit, both of which should vary with the pollen and nectar "neighborhoods" of a plant, i.e., with pollen and nectar availability in nearby plants. One determinant of these neighborhoods is per-flower production of pollen and nectar, which is likely to respond to environmental influences. In this study, we explored environmental effects on pollen and nectar production and on pollination success in order to follow up a surprising result from a previous study: flowers of Ipomopsis aggregata received less pollen in years of high visitation by their hummingbird pollinators. A new analysis of the earlier data indicated that high bird visitation corresponded to drought years. We hypothesized that drought might contribute to the enigmatic prior result if it decreases both nectar and pollen production: in dry years, low nectar availability could cause hummingbirds to visit flowers at a higher rate, and low pollen availability could cause them to deposit less pollen per visit. A greenhouse experiment demonstrated that drought does reduce both pollen and nectar production by I. aggregata flowers. This result was corroborated across 6 yr of variable precipitation and soil moisture in four unmanipulated field populations. In addition, experimental removal of pollen from flowers reduced the pollen received by nearby flowers. We conclude that there is much to learn about how abiotic and biotic environmental drivers jointly affect pollen and nectar production and availability, and how this contributes to pollen and nectar neighborhoods and thus influences pollination success.

Linking definitions, mechanisms, and modeling of drought-induced tree death.

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Anderegg, William R L; Berry, Joseph A; Field, Christopher B

2012-12-01

Tree death from drought and heat stress is a critical and uncertain component in forest ecosystem responses to a changing climate. Recent research has illuminated how tree mortality is a complex cascade of changes involving interconnected plant systems over multiple timescales. Explicit consideration of the definitions, dynamics, and temporal and biological scales of tree mortality research can guide experimental and modeling approaches. In this review, we draw on the medical literature concerning human death to propose a water resource-based approach to tree mortality that considers the tree as a complex organism with a distinct growth strategy. This approach provides insight into mortality mechanisms at the tree and landscape scales and presents promising avenues into modeling tree death from drought and temperature stress. Copyright © 2012 Elsevier Ltd. All rights reserved.

Detecting Drought-Induced Tree Mortality in Sierra Nevada Forests with Time Series of Satellite Data

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Sarah Byer

2017-09-01

Full Text Available A five-year drought in California led to a significant increase in tree mortality in the Sierra Nevada forests from 2012 to 2016. Landscape level monitoring of forest health and tree dieback is critical for vegetation and disaster management strategies. We examined the capability of multispectral imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS in detecting and explaining the impacts of the recent severe drought in Sierra Nevada forests. Remote sensing metrics were developed to represent baseline forest health conditions and drought stress using time series of MODIS vegetation indices (VIs and a water index. We used Random Forest algorithms, trained with forest aerial detection surveys data, to detect tree mortality based on the remote sensing metrics and topographical variables. Map estimates of tree mortality demonstrated that our two-stage Random Forest models were capable of detecting the spatial patterns and severity of tree mortality, with an overall producer’s accuracy of 96.3% for the classification Random Forest (CRF and a RMSE of 7.19 dead trees per acre for the regression Random Forest (RRF. The overall omission errors of the CRF ranged from 19% for the severe mortality class to 27% for the low mortality class. Interpretations of the models revealed that forests with higher productivity preceding the onset of drought were more vulnerable to drought stress and, consequently, more likely to experience tree mortality. This method highlights the importance of incorporating baseline forest health data and measurements of drought stress in understanding forest response to severe drought.

Linking meteorological drivers of spring-summer drought regimes to agricultural drought risk in China

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Dai, L.; Wright, J. S.; Yu, C.; Huang, W. Y.

2017-12-01

As a drought prone country, China has experienced frequent severe droughts in recent decades. Drought frequency and severity are projected to increase in China under climate change. An understanding of the physical processes that contribute to extreme droughts is essential for seasonal forecasting, but the dominant physical mechanisms responsible for droughts in most parts of China are still unclear. Moreover, despite numerous studies on droughts in China, there are few clear connections between the meteorological and climatological drivers of extreme droughts and the associated agricultural consequences. This knowledge gap limits the capacity for decision-making support in drought management. The objectives of this study are (1) to identify robust spring-summer drought regimes over China, (2) to investigate the physical mechanisms associated with each regime, and (3) to better clarify connections between meteorological drought regimes and agricultural drought risk. First, we identify six drought regimes over China by applying an area-weighted k-means clustering technique to spatial patterns of spring-summer Standardized Precipitation Index (SPI) obtained from the ten-member ERA-20CM ensemble for 1900-2010. Second, we project these drought regimes onto agricultural drought risk maps for the three major cereal crops (rice, maize, and wheat) in China. Taking into account historical harvest areas for these crops, we then evaluate the potential impact of each drought regime on agricultural production. Third, the physical mechanisms and meteorological context behind each drought regimes are investigated based on monthly outputs from ERA20CM. We analyze the preceding and concurrent atmospheric circulation anomalies associated with each regime, and propose mechanistic explanations for drought development. This work provides a new perspective on diagnosing the physical mechanisms behind seasonal droughts, and lays a foundation for improving seasonal drought prediction and

GRACE-Assimilated Drought Indicators for the U.S. Drought Monitor

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Rui, Hualan; Vollmer, Bruce; Teng, Bill; Loeser, Carlee; Beaudoing, Hiroko; Rodell, Matt

2018-01-01

The Gravity Recovery and Climate Experiment (GRACE) mission detects changes in Earth's gravity field by precisely monitoring the changes in distance between two satellites orbiting the Earth in tandem. Scientists at NASA's Goddard Space Flight Center generate GRACE-assimilated groundwater and soil moisture drought indicators each week, for drought monitor-related studies and applications. The GRACE-assimilated Drought Indicator Version 2.0 data product (GRACE-DA-DM V2.0) is archived at, and distributed by, the NASA GES DISC (Goddard Earth Sciences Data and Information Services Center). More information about the data and data access is available on the data product landing page at https://disc.gsfc.nasa.gov/datasets /GRACEDADM_CLSM0125US_7D_2.0/summary. The GRACE-DA-DM V2.0 data product contains three drought indicators: Groundwater Percentile, Root Zone Soil Moisture Percentile, and Surface Soil Moisture Percentile. The drought indicators are of wet or dry conditions, expressed as a percentile, indicating the probability of occurrence within the period of record from 1948 to 2012. These GRACE-assimilated drought indicators, with improved spatial and temporal resolutions, should provide a more comprehensive and objective identification of drought conditions. This presentation describes the basic characteristics of the data and data services at NASA GES DISC and collaborative organizations, and uses a few examples to demonstrate the simple ways to explore the GRACE-assimilated drought indicator data.

Tropical Drosophila ananassae of wet-dry seasons show cross resistance to heat, drought and starvation

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Chanderkala Lambhod

2017-11-01

Full Text Available Plastic responses to multiple environmental stressors in wet or dry seasonal populations of tropical Drosophila species have received less attention. We tested plastic effects of heat hardening, acclimation to drought or starvation, and changes in trehalose, proline and body lipids in Drosophila ananassae flies reared under wet or dry season-specific conditions. Wet season flies revealed significant increase in heat knockdown, starvation resistance and body lipids after heat hardening. However, accumulation of proline was observed only after desiccation acclimation of dry season flies while wet season flies elicited no proline but trehalose only. Therefore, drought-induced proline can be a marker metabolite for dry-season flies. Further, partial utilization of proline and trehalose under heat hardening reflects their possible thermoprotective effects. Heat hardening elicited cross-protection to starvation stress. Stressor-specific accumulation or utilization as well as rates of metabolic change for each energy metabolite were significantly higher in wet-season flies than dry-season flies. Energy metabolite changes due to inter-related stressors (heat versus desiccation or starvation resulted in possible maintenance of energetic homeostasis in wet- or dry-season flies. Thus, low or high humidity-induced plastic changes in energy metabolites can provide cross-protection to seasonally varying climatic stressors.

Improved tolerance to post-anthesis drought stress by pre-drought priming at vegetative stages in drought-tolerant and -sensitive wheat cultivars.

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Abid, Muhammad; Tian, Zhongwei; Ata-Ul-Karim, Syed Tahir; Liu, Yang; Cui, Yakun; Zahoor, Rizwan; Jiang, Dong; Dai, Tingbo

2016-09-01

Wheat crop endures a considerable penalty of yield reduction to escape the drought events during post-anthesis period. Drought priming under a pre-drought stress can enhance the crop potential to tolerate the subsequent drought stress by triggering a faster and stronger defense mechanism. Towards these understandings, a set of controlled moderate drought stress at 55-60% field capacity (FC) was developed to prime the plants of two wheat cultivars namely Luhan-7 (drought tolerant) and Yangmai-16 (drought sensitive) during tillering (Feekes 2 stage) and jointing (Feekes 6 stage), respectively. The comparative response of primed and non-primed plants, cultivars and priming stages was evaluated by applying a subsequent severe drought stress at 7 days after anthesis. The results showed that primed plants of both cultivars showed higher potential to tolerate the post-anthesis drought stress through improved leaf water potential, more chlorophyll, and ribulose-1, 5-bisphosphate carboxylase/oxygenase contents, enhanced photosynthesis, better photoprotection and efficient enzymatic antioxidant system leading to less yield reductions. The primed plants of Luhan-7 showed higher capability to adapt the drought stress events than Yangmai-16. The positive effects of drought priming to sustain higher grain yield were pronounced in plants primed at tillering than those primed at jointing. In consequence, upregulated functioning of photosynthetic apparatus and efficient enzymatic antioxidant activities in primed plants indicated their superior potential to alleviate a subsequently occurring drought stress, which contributed to lower yield reductions than non-primed plants. However, genotypic and priming stages differences in response to drought stress also contributed to affect the capability of primed plants to tolerate the post-anthesis drought stress conditions in wheat. Copyright © 2016. Published by Elsevier Masson SAS.

Hydraulic adjustments underlying drought resistance of Pinus halepensis.

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Klein, Tamir; Cohen, Shabtai; Yakir, Dan

2011-06-01

Drought-induced tree mortality has increased over the last decades in forests around the globe. Our objective was to investigate under controlled conditions the hydraulic adjustments underlying the observed ability of Pinus halepensis to survive seasonal drought under semi-arid conditions. One hundred 18-month saplings were exposed in the greenhouse to 10 different drought treatments, simulating combinations of intensities (fraction of water supply relative to control) and durations (period with no water supply) for 30 weeks. Stomata closed at a leaf water potential (Ψ(l)) of -2.8 MPa, suggesting isohydric stomatal regulation. In trees under extreme drought treatments, stomatal closure reduced CO(2) uptake to -1 µmol m(-2) s(-1), indicating the development of carbon starvation. A narrow hydraulic safety margin of 0.3 MPa (from stomatal closure to 50% loss of hydraulic conductivity) was observed, indicating a strategy of maximization of CO2 uptake in trees otherwise adapted to water stress. A differential effect of drought intensity and duration was observed, and was explained by a strong dependence of the water stress effect on the ratio of transpiration to evapotranspiration T/ET and the larger partitioning to transpiration associated with larger irrigation doses. Under intense or prolonged drought, the root system became the main target for biomass accumulation, taking up to 100% of the added biomass, while the stem tissue biomass decreased, associated with up to 60% reduction in xylem volume.

Adverse effects of increasing drought on air quality via natural processes

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Wang, Yuxuan; Xie, Yuanyu; Dong, Wenhao; Ming, Yi; Wang, Jun; Shen, Lu

2017-10-01

Drought is a recurring extreme of the climate system with well-documented impacts on agriculture and water resources. The strong perturbation of drought to the land biosphere and atmospheric water cycle will affect atmospheric composition, the nature and extent of which are not well understood. Here we present observational evidence that US air quality is significantly correlated with drought severity. Severe droughts during the period of 1990-2014 were found associated with growth-season (March-October) mean enhancements in surface ozone and PM2.5 of 3.5 ppbv (8 %) and 1.6 µg m-3 (17 %), respectively. The pollutant enhancements associated with droughts do not appear to be affected by the decreasing trend of US anthropogenic emissions, indicating natural processes as the primary cause. Elevated ozone and PM2.5 are attributed to the combined effects of drought on deposition, natural emissions (wildfires, biogenic volatile organic compounds (BVOCs), and dust), and chemistry. Most climate-chemistry models are not able to reproduce the observed correlations of ozone and PM2.5 to drought severity. The model deficiencies are partly attributed to the lack of drought-induced changes in land-atmosphere exchanges of reactive gases and particles and misrepresentation of cloud changes under drought conditions. By applying the observed relationships between drought and air pollutants to climate model projected drought occurrences, we estimate an increase of 1-6 % for ground-level O3 and 1-16 % for PM2.5 in the US by 2100 compared to the 2000s due to increasing drought alone. Drought thus poses an important aspect of climate change penalty on air quality, and a better prediction of such effects would require improvements in model processes.

Drought-associated changes in climate and their relevance for ecosystem experiments and models

Directory of Open Access Journals (Sweden)

H. J. De Boeck

2011-05-01

Full Text Available Drought periods can have important impacts on plant productivity and ecosystem functioning, but climatic conditions other than the lack of precipitation during droughts have never been quantified and have therefore not been considered explicitly in both experimental and modeling studies. Here, we identify which climatic characteristics deviate from normal during droughts and how these deviations could affect plant responses. Analysis of 609 years of daily data from nine Western European meteorological stations reveals that droughts in the studied region are consistently associated with more sunshine (+45 %, increased mean (+1.6 °C and maximum (+2.8 °C air temperatures and vapour pressure deficits that were 51 % higher than under normal conditions. These deviations from normal increase significantly as droughts progress. Using the process-model ORCHIDEE, we simulated droughts consistent with the results of the dataset analysis and compared water and carbon exchange of three different vegetation types during such natural droughts and droughts in which only the precipitation was affected. The comparison revealed contrasting responses: carbon loss was higher under natural drought in grasslands, while increased carbon uptake was found especially in decidious forests. This difference was attributed to better access to water reserves in forest ecosystems which prevented drought stress. This demonstrates that the warmer and sunnier conditions naturally associated with droughts can either improve growth or aggravate drought-related stress, depending on water reserves. As the impacts of including or excluding climatic parameters that correlate with drought are substantial, we propose that both experimental and modeling efforts should take into account other environmental factors than merely precipitation.

Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions.

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Mo, Yanling; Wang, Yongqi; Yang, Ruiping; Zheng, Junxian; Liu, Changming; Li, Hao; Ma, Jianxiang; Zhang, Yong; Wei, Chunhua; Zhang, Xian

2016-01-01

Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and [Formula: see text] compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes

The influence of drought on flow‐ecology relationships in Ozark Highland streams

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Lynch, Dustin T.; Leasure, D. R.; Magoulick, Daniel D.

2018-01-01

Drought and summer drying can have strong effects on abiotic and biotic components of stream ecosystems. Environmental flow‐ecology relationships may be affected by drought and drying, adding further uncertainty to the already complex interaction of flow with other environmental variables, including geomorphology and water quality.Environment–ecology relationships in stream communities in Ozark Highland streams, USA, were examined over two years with contrasting environmental conditions, a drought year (2012) and a flood year (2013). We analysed fish, crayfish and benthic macroinvertebrate assemblages using two different approaches: (1) a multiple regression analysis incorporating predictor variables related to habitat, water quality, geomorphology and hydrology and (2) a canonical ordination procedure using only hydrologic variables in which forward selection was used to select predictors that were most related to our response variables.Reach‐scale habitat quality and geomorphology were found to be the most important influences on community structure, but hydrology was also important, particularly during the flood year. We also found substantial between‐year variation in environment–ecology relationships. Some ecological responses differed significantly between drought and flood years, while others remained consistent. We found that magnitude was the most important flow component overall, but that there was a shift in relative importance from low flow metrics during the drought year to average flow metrics during the flood year, and the specific metrics of importance varied markedly between assemblages and years.Findings suggest that understanding temporal variation in flow‐ecology relationships may be crucial for resource planning. While some relationships show temporal variation, others are consistent between years. Additionally, different kinds of hydrologic variables can differ greatly in terms of which assemblages they affect and how they affect

TRANSCRIPTOMIC CHANGES DRIVE PHYSIOLOGICAL RESPONSES TO PROGRESSIVE DROUGHT STRESS AND REHYDRATION IN TOMATO

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Paolo eIovieno

2016-03-01

Full Text Available Tomato is a major crop in the Mediterranean basin, where the cultivation in the open field is often vulnerable to drought. In order to adapt and survive to naturally occurring cycles of drought stress and recovery, plants employ a coordinated array of physiological, biochemical and molecular responses. Transcriptomic studies on tomato responses to drought and subsequent recovery are few in number. As the search for novel traits to improve the genetic tolerance to drought increases, a better understanding of these responses is required. To address this need we designed a study in which we induced two cycles of prolonged drought stress and a single recovery by rewatering in tomato. In order to dissect the complexity of plant responses to drought, we analyzed the physiological responses (stomatal conductance, CO2 assimilation and chlorophyll fluorescence, abscisic acid (ABA and proline contents. In addition to the physiological and metabolite assays, we generated transcriptomes for multiple points during the stress and recovery cycles. Cluster analysis of differentially expressed genes between the conditions has revealed potential novel components in stress response. The observed reduction in leaf gas exchanges and efficiency of the photosystem PSII was concomitant with a general down-regulation of genes belonging to the photosynthesis, light harvesting and photosystem I and II category induced by drought stress. Gene ontology (GO categories such as cell proliferation and cell cycle were also significantly enriched in the down-regulated fraction of genes upon drought stress, which may contribute to explain the observed growth reduction. Several histone variants were also repressed during drought stress, indicating that chromatin associated processes are also affected by drought. As expected, ABA accumulated after prolonged water deficit, driving the observed enrichment of stress related GOs in the up-regulated gene fractions, which included

Drought effects on soil COcacao agroforestry system in Sulawesi, Indonesia

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van Straaten, O.; Veldkamp, E.; Köhler, M.; Anas, I.

2009-12-01

Climate change induced droughts pose a serious threat to ecosystems across the tropics and sub-tropics, particularly to those areas not adapted to natural dry periods. In order to study the vulnerability of cacao (Theobroma cacao) - Gliricidia sepium agroforestry plantations to droughts a large scale throughfall displacement roof was built in Central Sulawesi, Indonesia. In this 19-month replicated experiment, we measured soil surface CO2 efflux (soil respiration) in three simulated drought plots compared with three adjacent control plots. Soil respiration rates peaked at intermediate soil moisture and decreased under increasingly dry conditions (drought induced), but also decreased when soils became water saturated, as evidenced in control plots. The simulated drought plots exhibited a slight decrease in soil respiration compared to the control plots (average 13% decrease). The strength of the drought effect was spatially variable - while some measurement chamber sites reacted strongly ("responsive") to the decrease in soil water content (up to R2=0.70) (n=11), others did not react at all ("non-responsive") (n=7). The degree of soil CO2 respiration drought response was highest around cacao tree stems and decreased with distance from the stem (R2=0.22). A significant correlation was measured between "responsive" soil respiration chamber sites and sap flux density ratios of cacao (R=0.61) and Gliricidia (R=0.65). Leaf litter CO2 respiration decreased as conditions became drier. During dry periods the litter layer contributed approximately 3-4% of the total CO2 efflux and up to 40% during wet periods. A CO2 flush was recorded during the rewetting phase that lasted for approximately two weeks, during which time accumulated labile carbon stocks mineralized. The net effect on soil CO2 emissions over the duration of the experiment was neutral, control plots respired 11.1±0.5 Mg C ha-1 yr-1, while roof plots respired 10.5±0.5 Mg C ha-1 yr-1.

Overexpression of AtEDT1/HDG11 in Chinese Kale (Brassica oleracea var. alboglabra) Enhances Drought and Osmotic Stress Tolerance.

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Zhu, Zhangsheng; Sun, Binmei; Xu, Xiaoxia; Chen, Hao; Zou, Lifang; Chen, Guoju; Cao, Bihao; Chen, Changming; Lei, Jianjun

2016-01-01

Plants are constantly challenged by environmental stresses, including drought and high salinity. Improvement of drought and osmotic stress tolerance without yield decrease has been a great challenge in crop improvement. The Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a protein of the class IV HD-Zip family, has been demonstrated to significantly improve drought tolerance in Arabidopsis, rice, and pepper. Here, we report that AtEDT1/HDG11 confers drought and osmotic stress tolerance in the Chinese kale. AtEDT1/HDG11-overexpression lines exhibit auxin-overproduction phenotypes, such as long hypocotyls, tall stems, more root hairs, and a larger root system architecture. Compared with the untransformed control, transgenic lines have significantly reduced stomatal density. In the leaves of transgenic Chinese kale plants, proline (Pro) content and reactive oxygen species-scavenging enzyme activity was significantly increased after drought and osmotic stress, particularly compared to wild kale. More importantly, AtEDT1/HDG11-overexpression leads to abscisic acid (ABA) hypersensitivity, resulting in ABA inhibitor germination and induced stomatal closure. Consistent with observed phenotypes, the expression levels of auxin, ABA, and stress-related genes were also altered under both normal and/or stress conditions. Further analysis showed that AtEDT1/HDG11, as a transcription factor, can target the auxin biosynthesis gene YUCC6 and ABA response genes ABI3 and ABI5. Collectively, our results provide a new insight into the role of AtEDT1/HDG11 in enhancing abiotic stress resistance through auxin- and ABA-mediated signaling response in Chinese kale.

CreativeDrought: An interdisciplinary approach to building resilience to drought

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Rangecroft, Sally; Van Loon, Anne; Rohse, Melanie; Day, Rosie; Birkinshaw, Stephen; Makaya, Eugine

2017-04-01

Drought events cause severe water and food insecurities in many developing countries where resilience to natural hazards and change is low due to a number of reasons (including poverty, social and political inequality, and limited access to information). Furthermore, with climate change and increasing pressures from population and societal change, populations are expected to experience future droughts outside of their historic range. Integrated water resources management is an established tool combining natural science, engineering and management to help address drought and associated impacts. However, it often lacks a strong social and cultural aspect, leading to poor implementation on the ground. For a more holistic approach to building resilience to future drought, a stronger interdisciplinary approach is required which can incorporate the local cultural context and perspectives into drought and water management, and communicate information effectively to communities. In this pilot project 'CreativeDrought', we use a novel interdisciplinary approach aimed at building resilience to future drought in rural Africa by combining hydrological modelling with rich local information and engaging communicative approaches from social sciences. The work is conducted through a series of steps in which we i) engage with local rural communities to collect narratives on drought experiences; ii) generate hydrological modelling scenarios based on IPCC projections, existing data and the collected narratives; iii) feed these back to the local community to gather their responses to these scenarios; iv) iteratively adapt them to obtain hypothetical future drought scenarios; v) engage the community with the scenarios to formulate new future drought narratives; and vi) use this new data to enhance local water resource management. Here we present some of the indigenous knowledge gathered through narratives and the hydrological modelling scenarios for a rural community in Southern Africa

Evaluation of drought tolerance in different growth stages of maize ...

African Journals Online (AJOL)

Jane

2011-10-12

Oct 12, 2011 ... stability under drought stress conditions is to develop ... of multi-environmental traits (Ahmadzadeh, 1997; Shiri et ... principal component analysis was performed. ... Analysis of variance of mean squares of grain yield trait.

Perceptions of drought among rural farmers in the Savelugu district ...

African Journals Online (AJOL)

Drought is one of the most constraining climate extremes to livelihoods particularly in ... and interpretation of environmental phenomena have an immense influence on people's ..... The smoke is said to dissipate rain-clouds, resulting in.

Mountains in the third millennium - a decade of droughts and water scarcity?

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de Jong, C.; Shaban, A.; Belete, T.

2012-04-01

Droughts and water scarcity have touched the Alps, Mediterranean and East African mountain chains more intensively since the beginning of the third millennium and pose a major challenge for water management. The year 2011 has been no exception, with the lowest river levels on record over the past 50 years even for alpine rivers. Although considerable climate fluctuations and persistent droughts have occurred in the past, it is quite remarkable that the five hottest summers over the past 500 years in Europe and the Alps have all been concentrated after 2002, falling far outside their normal historical distribution. In most mountain chains drought phenomena are persistent over large areas and over a variety of scales. The hydrological consequences, such as decreased rain- and snowfall, drying of springs, decreased river and groundwater discharge, lowering of lake levels and excessive evaporation etc. are considerable. Seasonality has been considerably affected, with the summer extending well into the spring and autumn. Mountain-fed rivers have experienced unusually low discharge over the last 10 years, with a decreasing trend both in summer and winter discharge. These hydrological changes have multiple impacts on availability of drinking water and the energy sector, decreasing hydroelectric production and availability of cooling water for the nuclear industry and negatively effecting river navigation, irrigation agriculture as well as winter tourism in mountains. Despite these naturally-induced shortcomings, adaptation has not always been rational. In some cases, maladaptation has led to overexploitation of water resources during drought conditions, exasperating water scarcity. For example, for the tourism sector in the Alps, water demand for drinking water and artificial snow making lies far above the available resources during the winter season for numerous resorts. This has long term environmental and socio-economic impacts such as destruction of wetlands

Screening for Osmotic Stress Responses in Rice Varieties under Drought Condition

OpenAIRE

Simon Swapna; Korukkanvilakath Samban Shylaraj

2017-01-01

Drought is the major abiotic stress factor that limits rice production worldwide. To evaluate the osmotic stress responses in rice varieties under drought condition, a total of 42 high-yielding rice varieties were collected from various research stations of Kerala Agricultural University in India. The experimental setup comprises of initial hydroponic treatments at different osmotic potentials, artificially induced by desired strengths of polyethylene glycol (PEG6000), and followed by the pot...

The current California drought through EDDI's eyes: early warning and monitoring of agricultural and hydrologic drought with the new Evaporative Demand Drought Index.

Science.gov (United States)

Hobbins, M.; McEvoy, D.; Huntington, J. L.; Wood, A. W.; Morton, C.; Verdin, J. P.

2015-12-01

We have developed a physically based, multi-scalar drought index—the Evaporative Demand Drought Index (EDDI)—to improve treatment of evaporative dynamics in drought monitoring. Existing popular drought indices—such as the Palmer Drought Severity Index that informs much of the US Drought Monitor (USDM)—have primarily relyied on precipitation and temperature (T) to represent hydroclimatic anomalies, leaving evaporative demand (E0) most often derived from poorly performing T-based parameterizations then used to derive actual evapotranspiration (ET) from LSMs. Instead, EDDI leverages the inter-relations of E0 and ET, measuring E0's physical response to surface drying anomalies due to two distinct land surface/atmosphere interactions: (i) in sustained drought, limited moisture availability forces E0 and ET into a complementary relation, whereby ET declines as E0 increases; and (ii) in "flash" droughts, E0 increases due to increasing advection or radiation. E0's rise in response to both drought types suggests EDDI's robustness as a monitor and leading indicator of drought. To drive EDDI, we use for E0 daily reference ET from the ASCE Standardized Reference ET equation forced by North American Land Data Assimilation System drivers. EDDI is derived by aggregating E0 anomalies from its long-term mean across a period of interest and normalizing them to a Z-score. Positive EDDI indicates drier than normal conditions (and so drought). We use the current historic California drought as a test-case in which to examine EDDI's performance in monitoring agricultural and hydrologic drought. We observe drought development and decompose the behavior of drought's evaporative drivers during in-drought intensification periods and wetting events. EDDI's performance as a drought leading indicator with respect to the USDM is tested in important agricultural regions. Comparing streamflow from several USGS gauges in the Sierra Nevada to EDDI, we find that EDDI tracks most major

Effects of Recurring Droughts on Extracellular Enzyme Activity in Mountain Grassland

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Fuchslueger, L.; Bahn, M.; Kienzl, S.; Hofhansl, F.; Schnecker, J.; Richter, A.

2015-12-01

Water availability is a key factor for biogeochemical processes and determines microbial activity and functioning, and thereby organic matter decomposition in soils by affecting the osmotic potential, soil pore connectivity, substrate diffusion and nutrient availability. Low water availability during drought periods therefore directly affects microbial activity. Recurring drought periods likely induce shifts in microbial structure that might be reflected in altered responses of microbial turnover of organic matter by extracellular enzymes. To study this we measured a set of potential extracellular enzyme activity rates (cellobiohydrolase CBH; leucine-amino-peptidase LAP; phosphatase PHOS; phenoloxidase POX), in grassland soils that were exposed to extreme experimental droughts during the growing seasons of up to five subsequent years. During the first drought period after eight weeks of rain exclusion all measured potential enzyme activities were significantly decreased. In parallel, soil extractable organic carbon and nitrogen concentrations increased and microbial community structure, determined by phospholipid fatty acid analysis, changed. In soils that were exposed to two and three drought periods only PHOS decreased. After four years of drought again CBH, PHOS and POX decreased, while LAP was unaffected; after five years of drought PHOS and POX decreased and CBH and LAP remained stable. Thus, our results suggest that recurring extreme drought events can cause different responses of extracellular enzyme activities and that the responses change over time. We will discuss whether and to what degree these changes were related to shifts in microbial community composition. However, independent of whether a solitary or a recurrent drought was imposed, in cases when enzyme activity rates were altered during drought, they quickly recovered after rewetting. Overall, our data suggest that microbial functioning in mountain grassland is sensitive to drought, but highly

Overexpression of CaDSR6 increases tolerance to drought and salt stresses in transgenic Arabidopsis plants.

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Kim, Eun Yu; Seo, Young Sam; Park, Ki Youl; Kim, Soo Jin; Kim, Woo Taek

2014-11-15

The partial CaDSR6 (Capsicum annuum Drought Stress Responsive 6) cDNA was previously identified as a drought-induced gene in hot pepper root tissues. However, the cellular role of CaDSR6 with regard to drought stress tolerance was unknown. In this report, full-length CaDSR6 cDNA was isolated. The deduced CaDSR6 protein was composed of 234 amino acids and contained an approximately 30 amino acid-long Asp-rich domain in its central region. This Asp-rich domain was highly conserved in all plant DSR6 homologs identified and shared a sequence identity with the N-terminal regions of yeast p23(fyp) and human hTCTP, which contain Rab protein binding sites. Transgenic Arabidopsis plants overexpressing CaDSR6 (35S:CaDSR6-sGFP) were tolerant to high salinity, as identified by more vigorous root growth and higher levels of total chlorophyll than wild type plants. CaDSR6-overexpressors were also more tolerant to drought stress compared to wild type plants. The 35S:CaDSR6-sGFP leaves retained their water content and chlorophyll more efficiently than wild type leaves in response to dehydration stress. The expression of drought-induced marker genes, such as RD20, RD22, RD26, RD29A, RD29B, RAB18, KIN2, ABF3, and ABI5, was markedly increased in CaDSR6-overexpressing plants relative to wild type plants under both normal and drought conditions. These results suggest that overexpression of CaDSR6 is associated with increased levels of stress-induced genes, which, in turn, conferred a drought tolerant phenotype in transgenic Arabidopsis plants. Overall, our data suggest that CaDSR6 plays a positive role in the response to drought and salt stresses. Copyright © 2014 Elsevier B.V. All rights reserved.

Screening for Osmotic Stress Responses in Rice Varieties under Drought Condition

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Simon Swapna

2017-09-01

Full Text Available Drought is the major abiotic stress factor that limits rice production worldwide. To evaluate the osmotic stress responses in rice varieties under drought condition, a total of 42 high-yielding rice varieties were collected from various research stations of Kerala Agricultural University in India. The experimental setup comprises of initial hydroponic treatments at different osmotic potentials, artificially induced by desired strengths of polyethylene glycol (PEG6000, and followed by the pot planted experiments in the rain-out-zone. The activities of antioxidant enzymes, relative water content, cell membrane stability, photosynthetic pigments, proline content, along with plant growth parameters of the varieties under drought condition were evaluated. Moreover, the standard scores of these rice varieties were assessed under stress and recovery conditions based on the scoring scale of the Standard Evaluation System for rice. Among the 42 rice varieties, we identified 2 rice varieties, Swarnaprabha and Kattamodan, with less leaf rolling, better drought recovery ability as well as relative water content, increased membrane stability index, osmolyte accumulation, and antioxidant enzyme activities pointed towards their degree of tolerance to drought stress. The positive adaptive responses of these rice varieties towards drought stress can be used in the genetic improvement of rice drought resistance breeding program.

Extreme wildfire events are linked to global-change-type droughts in the northern Mediterranean

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Ruffault, Julien; Curt, Thomas; Martin-StPaul, Nicolas K.; Moron, Vincent; Trigo, Ricardo M.

2018-03-01

Increasing drought conditions under global warming are expected to alter the frequency and distribution of large and high-intensity wildfires. However, our understanding of the impact of increasing drought on extreme wildfires events remains incomplete. Here, we analyzed the weather conditions associated with the extreme wildfires events that occurred in Mediterranean France during the exceptionally dry summers of 2003 and 2016. We identified that these fires were related to two distinct shifts in the fire weather space towards fire weather conditions that had not been explored before and resulting from specific interactions between different types of drought and different fire weather types. In 2016, a long-lasting press drought intensified wind-driven fires. In 2003, a hot drought combining a heat wave with a press drought intensified heat-induced fires. Our findings highlight that increasing drought conditions projected by climate change scenarios might affect the dryness of fuel compartments and lead to a higher frequency of extremes wildfires events.

Combined effect of salt and drought on boron toxicity in Puccinellia tenuiflora.

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Liu, Chunguang; Dai, Zheng; Xia, Jingye; Chang, Can; Sun, Hongwen

2018-08-15

Boron toxicity is a worldwide problem, usually accompanied by salt (NaCl) and drought. The combined stresses may induce complex toxicity to the plant. The aim of the present study was to investigate how the combined stresses of salt and drought affect B toxicity in plants. Puccinellia tenuiflora seedlings were planted in vermiculite. A three (B) × three (salt) × three (drought) factorial experiment (for a total of 27 treatments) was conducted. After a 30-day cultivation, plants were harvested to determine dry weight and the concentrations of B, Na + , K + , Ca 2+ , and Mg 2+ . Plant growth was inhibited by B toxicity, which was alleviated by salt and drought. B stress enhanced B uptake and transport of the plant, which was inhibited by salt and drought. B stress had a little effect on K + and Na + concentration and caused Ca 2+ and Mg 2+ accumulation in the plant. Salt addition increased Na + concentration and inhibited Ca 2+ and Mg 2+ accumulation. Drought addition inhibited Na + accumulation and enhanced Ca 2+ and Mg 2+ accumulation. The combined stresses of salt and drought had a greater alleviation on the inhibition of dry weight caused by B than individual salt and drought. Besides, the combined stresses of salt and drought also enhanced B uptake and inhibited B transport. The results indicate that salt, drought, and the combined stresses of salt and drought all can alleviate B toxicity in P. tenuiflora, the main mechanism of which is the restriction of B and Na + uptake caused by salt and drought. The combined stresses of salt and drought have a greater effect on B toxicity than individual salt and drought. Copyright © 2018 Elsevier Inc. All rights reserved.

Drought responses of three closely related Caragana species: implication for their vicarious distribution.

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Ma, Fei; Na, Xiaofan; Xu, Tingting

2016-05-01

Drought is a major environmental constraint affecting growth and distribution of plants in the desert region of the Inner Mongolia plateau. Caragana microphylla, C. liouana, and C. korshinskii are phylogenetically close but distribute vicariously in Mongolia plateau. To gain a better understanding of the ecological differentiation between these three species, we examined the leaf gas exchange, growth, water use efficiency, biomass accumulation and allocation by subjecting their seedlings to low and high drought treatments in a glasshouse. Increasing drought stress had a significant effect on many aspects of seedling performance in all species, but the physiology and growth varied with species in response to drought. C. korshinskii exhibited lower sensitivity of photosynthetic rate and growth, lower specific leaf area, higher biomass allocation to roots, higher levels of water use efficiency to drought compared with the other two species. Only minor interspecific differences in growth performances were observed between C. liouana and C. microphylla. These results indicated that faster seedling growth rate and more efficient water use of C. korshinskii should confer increased drought tolerance and facilitate its establishment in more severe drought regions relative to C. liouana and C. microphylla.

Forest Growth Responses to Drought at Short- and Long-Term Scales in Spain: Squeezing the Stress Memory from Tree Rings

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J. Julio Camarero

2018-02-01

Full Text Available Drought-triggered declines in forest productivity and associated die-off events have increased considerably due to climate warming in the last decades. There is an increasing interest in quantifying the resilience capacity of forests against climate warming and drought to uncover how different stands and tree species will resist and recover after more frequent and intense droughts. Trees form annual growth rings that represent an accurate record of how forest growth responded to past droughts. Here we use dendrochronology to quantify the radial growth of different forests subjected to contrasting climatic conditions in Spain during the last half century. Particularly, we considered four climatically contrasting areas where dominant forests showed clear signs of drought-induced dieback. Studied forests included wet sites dominated by silver fir (Abies alba in the Pyrenees and beech (Fagus sylvatica stands in northern Spain, and drought-prone sites dominated by Scots pine (Pinus sylvestris in eastern Spain and black pine (Pinus nigra in the semi-arid south-eastern Spain. We quantified the growth reduction caused by different droughts and assessed the short-and long-term resilience capacity of declining vs. non-declining trees in each forest. In all cases, drought induced a marked growth reduction regardless tree vigor. However, the capacity to recover after drought (resilience at short- and long-term scales varied greatly between declining and non-declining individuals. In the case of beech and silver fir, non-declining individuals presented greater growth rates and capacity to recover after drought than declining individuals. For Scots pine, the resilience to drought was found to be lower in recent years regardless the tree vigor, but the growth reduction caused by successive droughts was more pronounced in declining than in non-declining individuals. In the black pine forest an extreme drought induced a marked growth reduction in declining

Limited growth recovery after drought-induced forest dieback in very defoliated trees of two pine species

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Guillermo eGuada

2016-04-01

Full Text Available Mediterranean pine forests display high resilience after extreme climatic events such as severe droughts. However, recent dry spells causing growth decline and triggering forest dieback challenge the capacity of some forests to recover following major disturbances. To describe how resilient the responses of forests to drought can be, we quantified growth dynamics in plantations of two pine species (Scots pine, black pine located in south-eastern Spain and showing drought-triggered dieback. Radial growth was characterized at inter- (tree-ring width and intra-annual (xylogenesis scales in three defoliation levels. It was assumed that the higher defoliation the more negative the impact of drought on tree growth. Tree-ring width chronologies were built and xylogenesis was characterized three years after the last severe drought occurred. Annual growth data and the number of tracheids produced in different stages of xylem formation were related to climate data at several time scales. Drought negatively impacted growth of the most defoliated trees in both pine species. In Scots pine, xylem formation started earlier in the non-defoliated than in the most defoliated trees. Defoliated trees presented the shortest duration of the radial-enlargement phase in both species. On average the most defoliated trees formed 60% of the number of mature tracheids formed by the non-defoliated trees in both species. Since radial enlargement is the xylogenesis phase most tightly related to final growth, this explains why the most defoliated trees grew the least due to their altered xylogenesis phases. Our findings indicate a very limited resilience capacity of drought-defoliated Scots and black pines. Moreover, droughts produce legacy effects on xylogenesis of highly defoliated trees which could not recover previous growth rates and are thus more prone to die.

Ascophyllum nodosum Seaweed Extract Alleviates Drought Stress in Arabidopsis by Affecting Photosynthetic Performance and Related Gene Expression

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Antonietta Santaniello

2017-08-01

Full Text Available Drought represents one of the most relevant abiotic stress affecting growth and yield of crop plants. In order to improve the agricultural productivity within the limited water and land resources, it is mandatory to increase crop yields in presence of unfavorable environmental stresses. The use of biostimulants, often containing seaweed extracts, represents one of the options for farmers willing to alleviate abiotic stress consequences on crops. In this work, we investigated the responses of Arabidopsis plants treated with an extract from the brown alga Ascophyllum nodosum (ANE, under drought stress conditions, demonstrating that ANE positively influences Arabidopsis survival. Pre-treatment with ANE induced a partial stomatal closure, associated with changes in the expression levels of genes involved in ABA-responsive and antioxidant system pathways. The pre-activation of these pathways results in a stronger ability of ANE-treated plants to maintain a better photosynthetic performance compared to untreated plants throughout the dehydration period, combined with a higher capacity to dissipate the excess of energy as heat in the reaction centers of photosystem II. Our results suggest that drought stressed plants treated with ANE are able to maintain a strong stomatal control and relatively higher values of both water use efficiency (WUE and mesophyll conductance during the last phase of dehydration. Simultaneously, the activation of a pre-induced antioxidant defense system, in combination with a more efficient energy dissipation mechanism, prevents irreversible damages to the photosynthetic apparatus. In conclusion, pre-treatment with ANE is effective to acclimate plants to the incoming stress, promoting an increased WUE and dehydration tolerance.

Heat and drought stresses in crops and approaches for their mitigation

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Lamaoui, Mouna; Jemo, Martin; Datla, Raju; Bekkaoui, Faouzi

2018-02-01

Drought and heat are major abiotic stresses that reduce crop productivity and weaken global food security, especially given the current and growing impacts of climate change and increases in the occurrence and severity of both stress factors. Plants have developed dynamic responses at the morphological, physiological and biochemical levels allowing them to escape and/or adapt to unfavourable environmental conditions. Nevertheless, even the mildest heat and drought stress negatively affects crop yield. Further, several independent studies have shown that increased temperature and drought can reduce crop yields by as much as 50%. Response to stress is complex and involves several factors including signaling, transcription factors, hormones, and secondary metabolites. The reproductive phase of development, leading to the grain production is shown to be more sensitive to heat stress in several crops. Advances coming from biotechnology including progress in genomics and information technology may mitigate the detrimental effects of heat and drought through the use of agronomic management practices and the development of crop varieties with increased productivity under stress. This review presents recent progress in key areas relevant to plant drought and heat tolerance. Furthermore, an overview and implications of physiological, biochemical and genetic aspects in the context of heat and drought are presented. Potential strategies to improve crop productivity are discussed.

Heat and Drought Stresses in Crops and Approaches for Their Mitigation

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Mouna Lamaoui

2018-02-01

Full Text Available Drought and heat are major abiotic stresses that reduce crop productivity and weaken global food security, especially given the current and growing impacts of climate change and increases in the occurrence and severity of both stress factors. Plants have developed dynamic responses at the morphological, physiological and biochemical levels allowing them to escape and/or adapt to unfavorable environmental conditions. Nevertheless, even the mildest heat and drought stress negatively affects crop yield. Further, several independent studies have shown that increased temperature and drought can reduce crop yields by as much as 50%. Response to stress is complex and involves several factors including signaling, transcription factors, hormones, and secondary metabolites. The reproductive phase of development, leading to the grain production is shown to be more sensitive to heat stress in several crops. Advances coming from biotechnology including progress in genomics and information technology may mitigate the detrimental effects of heat and drought through the use of agronomic management practices and the development of crop varieties with increased productivity under stress. This review presents recent progress in key areas relevant to plant drought and heat tolerance. Furthermore, an overview and implications of physiological, biochemical and genetic aspects in the context of heat and drought are presented. Potential strategies to improve crop productivity are discussed.

Global patterns of drought recovery

Energy Technology Data Exchange (ETDEWEB)

Schwalm, Christopher R.; Anderegg, William R. L.; Michalak, Anna M.; Fisher, Joshua B.; Biondi, Franco; Koch, George; Litvak, Marcy; Ogle, Kiona; Shaw, John D.; Wolf, Adam; Huntzinger, Deborah N.; Schaefer, Kevin; Cook, Robert; Wei, Yaxing; Fang, Yuanyuan; Hayes, Daniel; Huang, Maoyi; Jain, Atul; Tian, Hanqin

2017-08-09

Drought is a recurring multi-factor phenomenon with major impacts on natural and human systems1-3. Drought is especially important for land carbon sink variability, influencing climate regulation of the terrestrial biosphere4. While 20th Century trends in drought regime are ambiguous, “more extreme extremes” as well as more frequent and severe droughts3,7 are expected in the 21st Century. Recovery time, the length of time an ecosystem requires to revert to its pre-drought functional state, is a critical metric of drought impact. Yet the spatiotemporal patterning and controls of drought recovery are largely unknown. Here we use three distinct global datasets of gross primary productivity to show that across diverse terrestrial ecosystems drought recovery times are driven by biological productivity and biodiversity, with drought length and severity of secondary importance. Recovery time, especially for extreme droughts, and the areal extent of ecosystems in recovery from drought generally increase over the 20th Century, supporting an increase globally in drought impact8. Our results indicate that if future Anthropocene droughts become more widespread as expected, that droughts will become more frequent relative to recovery time. This increases the risk of entering a new regime where vegetation never recovers to its original state and widespread degradation of the land carbon sink ensues.

Up-regulation of abscisic acid signaling pathway facilitates aphid xylem absorption and osmoregulation under drought stress.

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Guo, Huijuan; Sun, Yucheng; Peng, Xinhong; Wang, Qinyang; Harris, Marvin; Ge, Feng

2016-02-01

The activation of the abscisic acid (ABA) signaling pathway reduces water loss from plants challenged by drought stress. The effect of drought-induced ABA signaling on the defense and nutrition allocation of plants is largely unknown. We postulated that these changes can affect herbivorous insects. We studied the effects of drought on different feeding stages of pea aphids in the wild-type A17 of Medicago truncatula and ABA signaling pathway mutant sta-1. We examined the impact of drought on plant water status, induced plant defense signaling via the abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways, and on the host nutritional quality in terms of leaf free amino acid content. During the penetration phase of aphid feeding, drought decreased epidermis/mesophyll resistance but increased mesophyll/phloem resistance of A17 but not sta-1 plants. Quantification of transcripts associated with ABA, JA and SA signaling indicated that the drought-induced up-regulation of ABA signaling decreased the SA-dependent defense but increased the JA-dependent defense in A17 plants. During the phloem-feeding phase, drought had little effect on the amino acid concentrations and the associated aphid phloem-feeding parameters in both plant genotypes. In the xylem absorption stage, drought decreased xylem absorption time of aphids in both genotypes because of decreased water potential. Nevertheless, the activation of the ABA signaling pathway increased water-use efficiency of A17 plants by decreasing the stomatal aperture and transpiration rate. In contrast, the water potential of sta-1 plants (unable to close stomata) was too low to support xylem absorption activity of aphids; the aphids on sta-1 plants had the highest hemolymph osmolarity and lowest abundance under drought conditions. Taken together this study illustrates the significance of cross-talk between biotic-abiotic signaling pathways in plant-aphid interaction, and reveals the mechanisms leading to alter

Environmentally induced epigenetic toxicity: potential public health concerns.

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Marczylo, Emma L; Jacobs, Miriam N; Gant, Timothy W

2016-09-01

Throughout our lives, epigenetic processes shape our development and enable us to adapt to a constantly changing environment. Identifying and understanding environmentally induced epigenetic change(s) that may lead to adverse outcomes is vital for protecting public health. This review, therefore, examines the present understanding of epigenetic mechanisms involved in the mammalian life cycle, evaluates the current evidence for environmentally induced epigenetic toxicity in human cohorts and rodent models and highlights the research considerations and implications of this emerging knowledge for public health and regulatory toxicology. Many hundreds of studies have investigated such toxicity, yet relatively few have demonstrated a mechanistic association among specific environmental exposures, epigenetic changes and adverse health outcomes in human epidemiological cohorts and/or rodent models. While this small body of evidence is largely composed of exploratory in vivo high-dose range studies, it does set a precedent for the existence of environmentally induced epigenetic toxicity. Consequently, there is worldwide recognition of this phenomenon, and discussion on how to both guide further scientific research towards a greater mechanistic understanding of environmentally induced epigenetic toxicity in humans, and translate relevant research outcomes into appropriate regulatory policies for effective public health protection.

Comparative Analysis of Drought Indices for Drought Zone Scheme of Northern Khorasan Province of Iran

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Ehsan EYSHI REZAEI

2011-08-01

Full Text Available Drought is one of the natural disasters which deeply influenced agricultural production. Drought monitoring programs could help to forecast and mitigate the impacts of drought. In this study occurrence, severity, and duration of drought were evaluated by monthly rainfall data (1986-2005 that were recorded at all meteorological stations in north Khorasan province of Iran. Drought indices include Standard Rainfall Index (SPI, Decades Index (DI and Percent of Normal (PNI calculated and compared to determine drought severity, duration and drought occurrence for all stations. In addition, drought maps were prepared by Inverse Distance Weighted (IDW method, for each study zone. Based on these indices, the most extensive drought occurred in 1989, 1990, 1995, 1996, 2000, and 2001 years. The longest duration of drought based on SPI happened in 1994 and 1997 years. Furthermore, the extreme drought occurred in 1990 and 2001 in all stations. In conclusion, Central part of this province was more exposed to extreme drought during study period than other parts of this region.

Dead or Alive? Using Membrane Failure and Chlorophyll a Fluorescence to Predict Plant Mortality from Drought.

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Guadagno, Carmela R; Ewers, Brent E; Speckman, Heather N; Aston, Timothy Llewellyn; Huhn, Bridger J; DeVore, Stanley B; Ladwig, Joshua T; Strawn, Rachel N; Weinig, Cynthia

2017-09-01

Climate models predict widespread increases in both drought intensity and duration in the next decades. Although water deficiency is a significant determinant of plant survival, limited understanding of plant responses to extreme drought impedes forecasts of both forest and crop productivity under increasing aridity. Drought induces a suite of physiological responses; however, we lack an accurate mechanistic description of plant response to lethal drought that would improve predictive understanding of mortality under altered climate conditions. Here, proxies for leaf cellular damage, chlorophyll a fluorescence, and electrolyte leakage were directly associated with failure to recover from drought upon rewatering in Brassica rapa (genotype R500) and thus define the exact timing of drought-induced death. We validated our results using a second genotype (imb211) that differs substantially in life history traits. Our study demonstrates that whereas changes in carbon dynamics and water transport are critical indicators of drought stress, they can be unrelated to visible metrics of mortality, i.e. lack of meristematic activity and regrowth. In contrast, membrane failure at the cellular scale is the most proximate cause of death. This hypothesis was corroborated in two gymnosperms ( Picea engelmannii and Pinus contorta ) that experienced lethal water stress in the field and in laboratory conditions. We suggest that measurement of chlorophyll a fluorescence can be used to operationally define plant death arising from drought, and improved plant characterization can enhance surface model predictions of drought mortality and its consequences to ecosystem services at a global scale. © 2017 American Society of Plant Biologists. All Rights Reserved.

Comparative proteomic responses of two bermudagrass (Cynodon dactylon (L). Pers.) varieties contrasting in drought stress resistance.

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Shi, Haitao; Ye, Tiantian; Chan, Zhulong

2014-09-01

Drought (water-deficit) stress is a serious environmental problem in plant growth and cultivation. As one of widely cultivated warm-season turfgrass, bermudagrass (Cynodon dactylon (L). Pers.) exhibits drastic natural variation in the drought stress resistance in leaves and stems of different varieties. In this study, proteomic analysis was performed to identify drought-responsive proteins in both leaves and stems of two bermudagrass varieties contrasting in drought stress resistance, including drought sensitive variety (Yukon) and drought tolerant variety (Tifgreen). Through comparative proteomic analysis, 39 proteins with significantly changed abundance were identified, including 3 commonly increased and 2 decreased proteins by drought stress in leaves and stems of Yukon and Tifgreen varieties, 2 differentially regulated proteins in leaves and stems of two varieties after drought treatment, 23 proteins increased by drought stress in Yukon variety and constitutively expressed in Tifgreen variety, and other 3 differentially expressed proteins under control and drought stress conditions. Among them, proteins involved in photosynthesis (PS), glycolysis, N-metabolism, tricarboxylicacid (TCA) and redox pathways were largely enriched, which might be contributed to the natural variation of drought resistance between Yukon and Tifgreen varieties. These studies provide new insights to understand the molecular mechanism underlying bermudagrass response to drought stress. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

European drought under climate change and an assessment of the uncertainties in projections

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Yu, R. M. S.; Osborn, T.; Conway, D.; Warren, R.; Hankin, R.

2012-04-01

Extreme weather/climate events have significant environmental and societal impacts, and anthropogenic climate change has and will continue to alter their characteristics (IPCC, 2011). Drought is one of the most damaging natural hazards through its effects on agricultural, hydrological, ecological and socio-economic systems. Climate change is stimulating demand, from public and private sector decision-makers and also other stakeholders, for better understanding of potential future drought patterns which could facilitate disaster risk management. There remain considerable levels of uncertainty in climate change projections, particularly in relation to extreme events. Our incomplete understanding of the behaviour of the climate system has led to the development of various emission scenarios, carbon cycle models and global climate models (GCMs). Uncertainties arise also from the different types and definitions of drought. This study examines climate change-induced changes in European drought characteristics, and illustrates the robustness of these projections by quantifying the effects of using different emission scenarios, carbon cycle models and GCMs. This is achieved by using the multi-institutional modular "Community Integrated Assessment System (CIAS)" (Warren et al., 2008), a flexible integrated assessment system for modelling climate change. Simulations generated by the simple climate model MAGICC6.0 are assessed. These include ten C4MIP carbon cycle models and eighteen CMIP3 GCMs under five IPCC SRES emission scenarios, four Representative Concentration Pathway (RCP) scenarios, and three mitigation scenarios with CO2-equivalent levels stabilising at 550 ppm, 500 ppm and 450 ppm. Using an ensemble of 2160 future precipitation scenarios, we present an analysis on both short (3-month) and long (12-month) meteorological droughts based on the Standardised Precipitation Index (SPI) for the baseline period (1951-2000) and two future periods of 2001-2050 and 2051

Evaluation Of Some Induced Gamma Ray Mutations In Bread Wheat For Drought Tolerance In The Newly Cultivated Sandy Soil

International Nuclear Information System (INIS)

EL-Sayed, S.; Sobieh, S.; Ragab, A. I.

2004-01-01

Two field experiments were out during two successive growing seasons (2001/2002 and 2002/2003) in the experimental farm of Plant Research Department, Nuclear Research Center, Abu Zaabal, to study the effect of two irrigation intervals on yield and its attributes of four induced mutations (Mutant 7, Mutant 8, Mutant 12 and Mutant 19) and two commercial varieties (Giza 164 and Sahel 1). The obtained results showed that : 1- Leaf temperature and protein content were significantly increased by increasing irrigation interval in the two seasons. 2- Longer irrigation interval significantly decreased plant height, spike length, No. of spikelets/spike, No. of spikes/m2, grain yield ton/hectare, straw yield ton/hectare and biological yield ton/hectare. While the mean values of all characters were increased in the two seasons when irrigation interval was shorter. 3- he mean value of grain yield ton/hectare for Mutant 7 and Mutant 19 was higher the other genotypes under long irrigation interval in the two seasons. 4- The interaction between irrigation intervals and wheat genotypes showed significant effect on spike length, No. of spikes/m2, 1000 grain weight, grain yield ton/hectare, straw yield ton/hectare, biological yield ton/hectare and harvest index. 5- Stress susceptibility index the different genotypes showed differences in their tolerance to drought. Mut. 7, Mut. 8 and Mut. 19 were more tolerant to drought than the other genotypes. 6- The highest water use efficiency (WUE) were obtained for Mut. 19 and Mut. 7 with long irrigation interval (20 days). 7- The Mutant 19 and Mutant 7 were more tolerant to drought than the other genotypes, due to higher yield and higher water use efficiency under drought and to their lowest values for stress susceptibility indices. (Authors)

Drought and Epidemic Typhus, Central Mexico, 1655–1918

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Acuna-Soto, Rudofo; Stahle, David W.

2014-01-01

Epidemic typhus is an infectious disease caused by the bacterium Rickettsia prowazekii and transmitted by body lice (Pediculus humanus corporis). This disease occurs where conditions are crowded and unsanitary. This disease accompanied war, famine, and poverty for centuries. Historical and proxy climate data indicate that drought was a major factor in the development of typhus epidemics in Mexico during 1655–1918. Evidence was found for 22 large typhus epidemics in central Mexico, and tree-ring chronologies were used to reconstruct moisture levels over central Mexico for the past 500 years. Below-average tree growth, reconstructed drought, and low crop yields occurred during 19 of these 22 typhus epidemics. Historical documents describe how drought created large numbers of environmental refugees that fled the famine-stricken countryside for food relief in towns. These refugees often ended up in improvised shelters in which crowding encouraged conditions necessary for spread of typhus. PMID:24564928

Future Drought Projections over the Iberian Peninsula using Drought Indices

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Garcia-Valdecasas Ojeda, M.; Yeste Donaire, P.; Góngora García, T. M.; Gámiz-Fortis, S. R.; Castro-Diez, Y.; Esteban-Parra, M. J.

2017-12-01

Currently, drought events are the cause of numerous annual economic losses. In a context of climate change, it is expected an increase in the severity and the frequency of drought occurrences, especially in areas such as the Mediterranean region. This study makes use of two drought indices in order to analyze the potential changes on future drought events and their effects at different time scales over a vulnerable region, the Iberian Peninsula. The indices selected were the Standardized Precipitation Evapotranspiration Index (SPEI), which takes into account the global warming through the temperature, and the Standardized Precipitation Index (SPI), based solely on precipitation data, at a spatial resolution of 0.088º ( 10 km). For their computation, current (1980-2014) and future (2021-2050 and 2071-2100) high resolution simulations were carried out using the Weather Research and Forecasting (WRF) model over a domain centered in the Iberian Peninsula, and nested in the 0.44 EUROCORDEX region. WRF simulations were driven by two different global bias-corrected climate models: the version 1 of NCAR's Community Earth System Model (CESM1) and the Max Planck Institute's Earth System Model (MPI-ESM-LR), and under two different Representative Concentration Pathway (RCP) scenarios: RCP 4.5 and RCP 8.5. Future projections were analyzed regarding to changes in mean, median and variance of drought indices with respect to the historical distribution, as well as changes in the frequency and duration of moderate and severe drought events. In general, results suggest an increase in frequency and severity of drought, especially for 2071-2100 period in the RCP 8.5 scenario. Results also shown an increase of drought phenomena more evident using the SPEI. Conclusions from this study could provide a valuable contribution to the understanding of how the increase of the temperature would affect the drought variability in the Mediterranean regions which is necessary for a suitable

Regulation of Plant Growth, Photosynthesis, Antioxidation and Osmosis by an Arbuscular Mycorrhizal Fungus in Watermelon Seedlings under Well-Watered and Drought Conditions

Science.gov (United States)

Mo, Yanling; Wang, Yongqi; Yang, Ruiping; Zheng, Junxian; Liu, Changming; Li, Hao; Ma, Jianxiang; Zhang, Yong; Wei, Chunhua; Zhang, Xian

2016-01-01

Drought stress has become an increasingly serious environmental issue that influences the growth and production of watermelon. Previous studies found that arbuscular mycorrhizal (AM) colonization improved the fruit yield and water use efficiency (WUE) of watermelon grown under water stress; however, the exact mechanisms remain unknown. In this study, the effects of Glomus versiforme symbiosis on the growth, physio-biochemical attributes, and stress-responsive gene expressions of watermelon seedlings grown under well-watered and drought conditions were investigated. The results showed that AM colonization did not significantly influence the shoot growth of watermelon seedlings under well-watered conditions but did promote root development irrespective of water treatment. Drought stress decreased the leaf relative water content and chlorophyll concentration, but to a lesser extent in the AM plants. Compared with the non-mycorrhizal seedlings, mycorrhizal plants had higher non-photochemical quenching values, which reduced the chloroplast ultrastructural damage in the mesophyll cells and thus maintained higher photosynthetic efficiency. Moreover, AM inoculation led to significant enhancements in the enzyme activities and gene expressions of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and monodehydroascorbate reductase in watermelon leaves upon drought imposition. Consequently, AM plants exhibited lower accumulation of MDA, H2O2 and O2− compared with non-mycorrhizal plants. Under drought stress, the soluble sugar and proline contents were significantly increased, and further enhancements were observed by pre-treating the drought-stressed plants with AM. Taken together, our findings indicate that mycorrhizal colonization enhances watermelon drought tolerance through a stronger root system, greater protection of photosynthetic apparatus, a more efficient antioxidant system and improved osmoregulation. This study contributes to advances

Diurnal oscillations of soybean circadian clock and drought responsive genes.

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Juliana Marcolino-Gomes

Full Text Available Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i drought stress affects gene expression of circadian clock components and (ii several stress responsive genes display diurnal oscillation in soybeans.

Strategies for Developing Drought Tolerant Cowpea varieties for the Semi-Arid regions of Nigeria

International Nuclear Information System (INIS)

Ishiyaku, M. F.

2000-10-01

Drought, meaning the deviation of the total amount and or distribution of precipitation from the normal is an important factor that cause untold human suffering as well as social and economic loss for any nation. Its effects are often felt by places so remote from the area of occurrence. In the agricultural sector, where its effect are most felt, drought risk greatly reduce investment in agriculture. This will no doubt contribute to national food insecurity and social unrest. Of the measures often prescribed to combat the menace of drought include the development and planting of drought resistant/tolerant crop varieties. This paper discusses the strategies for developing drought tolerant cowpea varieties for the drought-prone regions of Nigeria. These strategies include the introduction and screening of candidate drought tolerant cowpea germplasm and their utilization in developing new improved genotypes. The screening of populations will be carried out by adopting novel screening techniques in the lab as well as in the field. In addition to utilizing existing genetic variation to develop varieties with tolerance to drought, new sources of variation will be created artificially for the various traits known to confer tolerance to drought in cowpea. In creating genetic variability for drought tolerance traits artificially, the potential of irradiation induced mutation will be exploited

Carbon dynamics of Acer pseudoplatanus seedlings under drought and complete darkness.

Science.gov (United States)

Piper, Frida I; Fajardo, Alex

2016-11-01

Carbon (C) storage is considered a key component to plant survival under drought and shade, although the combined effects of these factors on survival remain poorly understood. We investigated how drought and shade alter the C dynamics and survival of tree seedlings, and whether drought limits the access to or usage of stored C. We experimentally applied two levels of soil humidity (well-watered versus drought, the latter induced by dry-down) and light availability (light versus complete darkness) on 1-year-old seedlings of Acer pseudoplatanus L. for 3 months. We quantified the survival, biomass, growth rate and non-structural carbohydrates (NSC) of seedlings at their time of death or at the end of the experiment for those that survived. We found that the soil dried out faster when drought was combined with light than when it was combined with complete darkness. Seedlings subjected to both drought and light showed reduced growth and reached 100% mortality earlier than any other treatment, with the highest NSC concentrations at the time of death. Seedlings exposed to both drought and complete darkness died significantly earlier than seedlings exposed to complete darkness only, but had similar NSC concentrations at time of their death, suggesting that drought accelerated the use of stored C under complete darkness. Complete darkness significantly reduced seedling growth and whole-plant NSC concentrations regardless of soil humidity, while root NSC concentrations were significantly more reduced when complete darkness was combined with drought conditions. Thus, the C dynamics in A. pseudoplatanus seedlings under complete darkness was not hindered by drought, i.e., the access and use of stored C was not limited by drought. The contrasting growth and C storage responses driven by drought under light versus complete darkness are consistent with a key role of the drought progression in the C dynamics of trees. © The Author 2016. Published by Oxford University Press. All

Overexpression of a maize plasma membrane intrinsic protein ZmPIP1;1 confers drought and salt tolerance in Arabidopsis.

Science.gov (United States)

Zhou, Lian; Zhou, Jing; Xiong, Yuhan; Liu, Chaoxian; Wang, Jiuguang; Wang, Guoqiang; Cai, Yilin

2018-01-01

Drought and salt stress are major abiotic stress that inhibit plants growth and development, here we report a plasma membrane intrinsic protein ZmPIP1;1 from maize and identified its function in drought and salt tolerance in Arabidopsis. ZmPIP1;1 was localized to the plasma membrane and endoplasmic reticulum in maize protoplasts. Treatment with PEG or NaCl resulted in induced expression of ZmPIP1;1 in root and leaves. Constitutive overexpression of ZmPIP1;1 in transgenic Arabidopsis plants resulted in enhanced drought and salt stress tolerance compared to wild type. A number of stress responsive genes involved in cellular osmoprotection in ZmPIP1;1 overexpression plants were up-regulated under drought or salt condition. ZmPIP1;1 overexpression plants showed higher activities of reactive oxygen species (ROS) scavenging enzymes such as catalase and superoxide dismutase, lower contents of stress-induced ROS such as superoxide, hydrogen peroxide and malondialdehyde, and higher levels of proline under drought and salt stress than did wild type. ZmPIP1;1 may play a role in drought and salt stress tolerance by inducing of stress responsive genes and increasing of ROS scavenging enzymes activities, and could provide a valuable gene for further plant breeding.

Genetic improvement of drought tolerance in semi-dwarf wheat

International Nuclear Information System (INIS)

Sial, M.A.; Laghari, K.A.

2012-01-01

Water stress is one of the main environmental constraints for the wheat crop. Drought stress from anthesis to maturity, especially if accompanied by heat stress, affects every morphological and physiological aspect of wheat plant and significantly reduces final yield. Genetic improvement for drought tolerance in wheat could be possible through conventional and mutation breeding tools. There is a dire need to identify stress tolerant genotypes which can grow and flourish well under harsh environments (low water requirements). Twelve newly evolved bread wheat genotypes alongwith 3 drought-tolerant commercial check varieties, viz., Sarsabz, Khirman and Chakwal-86 were screened under three water stresses (zero, single and two irrigations). Different yield associated traits were studied. At severe water stress (zero irrigation), six genotypes (BWM-3, NIA-8/7, NIA-9/5, NIA-28/4, NIA-25/5, MSH-36) produced significantly higher grain yield (ranged from 1522 to 2022 kg/ha) than check varieties. These genotypes had higher seed index and less spike sterility at severe stress, which indicated that these genotypes were less responsive to water stress and possessed more tolerance to drought stress. (author)

The effect of triazole induced photosynthetic pigments and biochemical constituents of Zea mays L. (Maize) under drought stress

Science.gov (United States)

Rajasekar, Mahalingam; Rabert, Gabriel Amalan; Manivannan, Paramasivam

2016-06-01

In this investigation, pot culture experiment was carried out to estimate the ameliorating effect of triazole compounds, namely Triadimefon (TDM), Tebuconazole (TBZ), and Propiconazole (PCZ) on drought stress, photosynthetic pigments, and biochemical constituents of Zea mays L. (Maize). From 30 days after sowing (DAS), the plants were subjected to 4 days interval drought (DID) stress and drought with TDM at 15 mg l-1, TBZ at 10 mg l-1, and PCZ at 15 mg l-1. Irrigation at 1-day interval was kept as control. Irrigation performed on alternative day. The plant samples were collected on 40, 50, and 60 DAS and separated into root, stem, and leaf for estimating the photosynthetic pigments and biochemical constituents. Drought and drought with triazole compounds treatment increased the biochemical glycine betaine content, whereas the protein and the pigments contents chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid, and anthocyanin decreased when compared to control. The triazole treatment mitigated the adverse effects of drought stress by increasing the biochemical potentials and paved the way to overcome drought stress in corn plant.

Managing vulnerability to drought and enhancing livelihood resilience in sub-Saharan Africa: Technological, institutional and policy options

Directory of Open Access Journals (Sweden)

Bekele Shiferaw

2014-06-01

Full Text Available Agriculture and the economies of Sub-Saharan Africa (SSA are highly sensitive to climatic variability. Drought, in particular, represents one of the most important natural factors contributing to malnutrition and famine in many parts of the region. The overall impact of drought on a given country/region and its ability to recover from the resulting social, economic and environmental impacts depends on several factors. The economic, social and environmental impacts of drought are huge in SSA and the national costs and losses incurred threaten to undermine the wider economic and development gains made in the last few decades in the region. There is an urgent need to reduce the vulnerability of countries to climate variability and to the threats posed by climate change. This paper attempts to highlight the challenges of drought in SSA and reviews the current drought risk management strategies, especially the promising technological and policy options for managing drought risks to protect livelihoods and reduce vulnerability. The review suggests the possibilities of several ex ante and ex post drought management strategies in SSA although their effectiveness depends on agro-climatic and socio-economic conditions. Existing technological, policy and institutional risk management measures need to be strengthened and integrated to manage drought ex ante and to minimize the ex post negative effects for vulnerable households and regions. A proactive approach that combines promising technological, institutional and policy solutions to manage the risks within vulnerable communities implemented by institutions operating at different levels (community, sub-national, and national is considered to be the way forward for managing drought and climate variability.

Characteristics and drivers of drought in Europe-a summary of the DROUGHT-R&SPI project

NARCIS (Netherlands)

Tallaksen, Lena M.; Stagge, James H.; Stahl, Kerstin; Gudmundsson, Lukas; Orth, Rene; Seneviratne, Sonia I.; Loon, van Anne F.; Lanen, van Henny A.J.

2015-01-01

A prerequisite to mitigate the wide range of drought impacts is to establish a good understanding of the drought generating mechanisms from their initiation as a meteorological drought through to their development as soil moisture and hydrological drought. The DROUGHT-R&SPI project has

Information Mining from Heterogeneous Data Sources: A Case Study on Drought Predictions

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Getachew B. Demisse

2017-07-01

Full Text Available The objective of this study was to develop information mining methodology for drought modeling and predictions using historical records of climate, satellite, environmental, and oceanic data. The classification and regression tree (CART approach was used for extracting drought episodes at different time-lag prediction intervals. Using the CART approach, a number of successful model trees were constructed, which can easily be interpreted and used by decision makers in their drought management decisions. The regression rules produced by CART were found to have correlation coefficients from 0.71–0.95 in rules-alone modeling. The accuracies of the models were found to be higher in the instance and rules model (0.77–0.96 compared to the rules-alone model. From the experimental analysis, it was concluded that different combinations of the nearest neighbor and committee models significantly increase the performances of CART drought models. For more robust results from the developed methodology, it is recommended that future research focus on selecting relevant attributes for slow-onset drought episode identification and prediction.

Improving the Performance of Water Policies: Evidence from Drought in Spain

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Mohamed Taher Kahil

2016-01-01

Full Text Available Water scarcity is a critical environmental issue worldwide, especially in arid and semiarid regions. In those regions, climate change projections suggest further reductions in freshwater supplies and increases of the recurrence, longevity and intensity of drought events. At present, one important question for policy debate is the identification of water policies that could address the mounting water scarcity problems. Suitable policies should improve economic efficiency, achieve environmental sustainability, and meet equity needs. This paper develops and applies an integrated hydro-economic model that links hydrological, economic and environmental elements to such issues. The model is used to conduct a direct comparison of water markets, water pricing and institutional cooperation, based on their economic, environmental and equity outcomes. The analysis is performed in the Jucar Basin of Spain, which is a good natural experiment for studying water scarcity and climate change policies. Results indicate that both institutional and water market policies are high performing instruments to limit the economic damage costs of droughts, achieving almost the same social benefits. However, the environmental effects of water markets are worrying. Another important finding is that water pricing is a poor policy option not only in terms of private and environmental benefits but also in terms of equity.

Soil microbial activity in Aleppo pine stands naturally regenerated after fire: silvicultural management and induced drought

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D. Moya

2013-01-01

Full Text Available In post-fire restoration, early monitoring is mandatory to check impacts and ecosystem responses to apply proper management according to social standards and ecological conditions. In areas where the natural regeneration was successful, excessive tree density can be found which induces to high intraspecific competence and assisted restoration management could be adequate. In addition, climatic changes will have large impacts on vegetation productivity and resilience since the regional models for south-eastern Spain predicts a rainfall decrease of about 20% and temperature increase of 4.5 ºC. The microbial biomass could be used as indicator of ecosystem recovery, since it is negatively affected by wildfires and depends on fire characteristics, vegetation and soil properties. Our aim is to determine how forest management may affect the ecosystem recovery in different climatic scenarios, included drought scenarios with and without forest management (thinning.We compared soil physicochemical properties and microbial activity in four scenarios: unmanaged and thinned stands in two rainfall scenarios (under induced drought. The study areas were set close to Yeste (Albacete where Aleppo pine forest were burned in summer 1994 (nearly 14000 ha. We set sixteen rectangular plots (150 m2; 15 m ×10 m implementing experimental silvicultural treatments: thinning eight plots in 2004, reducing the naturally recovered tree density from about 12000 to 1600 pine trees ha-1. In addition, in half the plots, we induced drought conditions from about 500 to 400 mm (20% from March 2009. In every plot, we monitored temperature at ground level (Ts, 10 cm depth (T10d and soil relative humidity (RH. Taking into account season of the year and canopy coverage, we collected soil samples in mid-winter (ending January 2011 and mid-spring (ending May 2011 under pine trees and in bare soil. The soil samples were used to evaluate soil physicochemical properties and soil microbial

Amazon Forests Response to Droughts: A Perspective from the MAIAC Product

Science.gov (United States)

Bi, Jian; Myneni, Ranga; Lyapustin, Alexei; Wang, Yujie; Park, Taejin; Chi, Chen; Yan, Kai; Knyazikhin, Yuri

2016-01-01

Amazon forests experienced two severe droughts at the beginning of the 21st century: one in 2005 and the other in 2010. How Amazon forests responded to these droughts is critical for the future of the Earth's climate system. It is only possible to assess Amazon forests' response to the droughts in large areal extent through satellite remote sensing. Here, we used the Multi-Angle Implementation of Atmospheric Correction (MAIAC) Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation index (VI) data to assess Amazon forests' response to droughts, and compared the results with those from the standard (Collection 5 and Collection 6) MODIS VI data. Overall, the MAIAC data reveal more realistic Amazon forests inter-annual greenness dynamics than the standard MODIS data. Our results from the MAIAC data suggest that: (1) the droughts decreased the greenness (i.e., photosynthetic activity) of Amazon forests; (2) the Amazon wet season precipitation reduction induced by El Niño events could also lead to reduced photosynthetic activity of Amazon forests; and (3) in the subsequent year after the water stresses, the greenness of Amazon forests recovered from the preceding decreases. However, as previous research shows droughts cause Amazon forests to reduce investment in tissue maintenance and defense, it is not clear whether the photosynthesis of Amazon forests will continue to recover after future water stresses, because of the accumulated damages caused by the droughts.

Extreme Weather and Civil War in Somalia: Does Drought Fuel Conflict through Livestock Price Shocks?

OpenAIRE

Maystadt, Jean-Francois; Ecker, Olivier; Mabiso, Athur

2013-01-01

Climate change leads to more frequent and more intense droughts in Somalia. In a global context, weather shocks have been found to perpetuate poverty and fuel civil conflict. By relating regional and temporal variations in violent conflict outbreaks with drought incidence and severity, we show that this causality is valid also for Somalia at the local level. We find that livestock price shocks drive drought-induced conflicts through reducing the opportunity costs of conflict participation. Ou...

Seasonal exposure to drought and air warming affects soil Collembola and mites.

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Guo-Liang Xu

Full Text Available Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4 °C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length ≤ 0.20 mm increased, but the percentage of large mites (body length >0.40 mm decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type.

Seasonal Exposure to Drought and Air Warming Affects Soil Collembola and Mites

Science.gov (United States)

Xu, Guo-Liang; Kuster, Thomas M.; Günthardt-Goerg, Madeleine S.; Dobbertin, Matthias; Li, Mai-He

2012-01-01

Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment) at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4°C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length 0.20 mm) increased, but the percentage of large mites (body length >0.40 mm) decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type. PMID:22905210

Seasonal exposure to drought and air warming affects soil Collembola and mites.

Science.gov (United States)

Xu, Guo-Liang; Kuster, Thomas M; Günthardt-Goerg, Madeleine S; Dobbertin, Matthias; Li, Mai-He

2012-01-01

Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment) at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4 °C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length ≤ 0.20 mm) increased, but the percentage of large mites (body length >0.40 mm) decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type.

Woody plant richness and NDVI response to drought events in Catalonian (northeastern Spain) forests.

Science.gov (United States)

Lloret, F; Lobo, A; Estevan, H; Maisongrande, P; Vayreda, J; Terradas, J

2007-09-01

The role of species diversity on ecosystem resistance in the face of strong environmental fluctuations has been addressed from both theoretical and experimental viewpoints to reveal a variety of positive and negative relationships. Here we explore empirically the relationship between the richness of forest woody species and canopy resistance to extreme drought episodes. We compare richness data from an extensive forest inventory to a temporal series of satellite imagery that estimated drought impact on forest canopy as NDVI (normalized difference vegetation index) anomalies of the dry summer in 2003 in relation to records of previous years. We considered five different types of forests that are representative of the main climatic and altitudinal gradients of the region, ranging from lowland Mediterranean to mountain boreal-temperate climates. The observed relationship differed among forest types and interacted with the climate, summarised by the Thorntwaite index. In Mediterranean Pinus halepensis forests, NDVI decreased during the drought. This decrease was stronger in forests with lower richness. In Mediterranean evergreen forests of Quercus ilex, drought did not result in an overall NDVI loss, but lower NDVI values were observed in drier localities with lower richness, and in more moist localities with higher number of species. In mountain Pinus sylvestris forests NDVI decreased, mostly due to the drought impact on drier localities, while no relation to species richness was observed. In moist Fagus sylvatica forests, NDVI only decreased in plots with high richness. No effect of drought was observed in the high mountain Pinus uncinata forests. Our results show that a shift on the diversity-stability relationship appears across the regional, climatic gradient. A positive relationship appears in drier localities, supporting a null model where the probability of finding a species able to cope with drier conditions increases with the number of species. However, in

Diffusive and Metabolic Constraints to Photosynthesis in Quinoa during Drought and Salt Stress

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Dilek Killi

2017-10-01

Full Text Available Quinoa (Chenopodium quinoa Willd. has been proposed as a hardy alternative to traditional grain crops in areas with warm-to-hot climates that are likely to experience increased drought and salt stress in the future. We characterised the diffusive and metabolic limitations to photosynthesis in quinoa exposed to drought and salt stress in isolation and combination. Drought-induced pronounced stomatal and mesophyll limitations to CO2 transport, but quinoa retained photosynthetic capacity and photosystem II (PSII performance. Saline water (300 mmol NaCl-equivalent to 60% of the salinity of sea-water supplied in identical volumes to the irrigation received by the control and drought treatments induced similar reductions in stomatal and mesophyll conductance, but also reduced carboxylation of ribulose-1,5-bisphosphate carboxylase/oxygenase, regeneration of ribulose-1,5-bisphosphate, increased non-photochemical dissipation of energy as heat and impaired PSII electron transport. This suggests that ion toxicity reduced PN via interference with photosynthetic enzymes and degradation of pigment–protein complexes within the thylakoid membranes. The results of this study demonstrate that the photosynthetic physiology of quinoa is resistant to the effects of drought, but quinoa may not be a suitable crop for areas subject to strong salt stress or irrigation with a concentration of saline water equivalent to a 300 mmol NaCl solution.

Diffusive and Metabolic Constraints to Photosynthesis in Quinoa during Drought and Salt Stress

Science.gov (United States)

Killi, Dilek; Haworth, Matthew

2017-01-01

Quinoa (Chenopodium quinoa Willd.) has been proposed as a hardy alternative to traditional grain crops in areas with warm-to-hot climates that are likely to experience increased drought and salt stress in the future. We characterised the diffusive and metabolic limitations to photosynthesis in quinoa exposed to drought and salt stress in isolation and combination. Drought-induced pronounced stomatal and mesophyll limitations to CO2 transport, but quinoa retained photosynthetic capacity and photosystem II (PSII) performance. Saline water (300 mmol NaCl-equivalent to 60% of the salinity of sea-water) supplied in identical volumes to the irrigation received by the control and drought treatments induced similar reductions in stomatal and mesophyll conductance, but also reduced carboxylation of ribulose-1,5-bisphosphate carboxylase/oxygenase, regeneration of ribulose-1,5-bisphosphate, increased non-photochemical dissipation of energy as heat and impaired PSII electron transport. This suggests that ion toxicity reduced PN via interference with photosynthetic enzymes and degradation of pigment–protein complexes within the thylakoid membranes. The results of this study demonstrate that the photosynthetic physiology of quinoa is resistant to the effects of drought, but quinoa may not be a suitable crop for areas subject to strong salt stress or irrigation with a concentration of saline water equivalent to a 300 mmol NaCl solution. PMID:29039809

Drought effects on reproductive and growth characteristics in seed orchards

International Nuclear Information System (INIS)

Varol, T.; Ozel, H. B.; Bilir, N.

2017-01-01

Global climate change is one of the most important environmental problems, and it is also known that this change will lead to negative effects such as drought and increase in global temperature. This change is also estimated to increase its episodic effects negatively on growth and reproduction of the forest trees. In order to estimate the episodic or continuous effects of the drought, it is necessary to carry out studies based on long-term data. One of these studies are the investigation to be carried out on seed orchards that are one of the most important seed resources in forestry. Within this context, in this study, we determined to the reproductive and growth responses of the clones to the drought that continued in the most drought season (2012) for 2 subsequent years along with 65-year climate data for Red Pine (Pinus brutia Ten.) and Taurus Cedar (Cedrus libani Rich.). The relationships of SPEI values with seed characteristics and cone production were examined by using Spearman Correlation Analysis. According to the results obtained from this study, it was found that the severe drought was effected the reproductive characteristics of both of red pine and cedar. The effect of drought on the number of cone (r=-0.810, P=0.022) in red pine and on the number of 1-year-old cones (r=-0.40, P=0.027) and on cone moisture (r=-0.715, P=0.022) in cedar was quite evident. These results indicate that approximately 65% of the change in number of cone in Red Pine and approximately 51% of the change in moisture content of the cones in cedar can be explained with the drought. From the data, it is clear that the drought is effective on the cone yield and seed characteristics in seed orchards of both of Red Pine and Taurus Cedar species. (author)

Exploring traditional aus-type rice for metabolites conferring drought tolerance.

Science.gov (United States)

Casartelli, Alberto; Riewe, David; Hubberten, Hans Michael; Altmann, Thomas; Hoefgen, Rainer; Heuer, Sigrid

2018-01-25

Traditional varieties and landraces belonging to the aus-type group of rice (Oryza sativa L.) are known to be highly tolerant to environmental stresses, such as drought and heat, and are therefore recognized as a valuable genetic resource for crop improvement. Using two aus-type (Dular, N22) and two drought intolerant irrigated varieties (IR64, IR74) an untargeted metabolomics analysis was conducted to identify drought-responsive metabolites associated with tolerance. The superior drought tolerance of Dular and N22 compared with the irrigated varieties was confirmed by phenotyping plants grown to maturity after imposing severe drought stress in a dry-down treatment. Dular and N22 did not show a significant reduction in grain yield compared to well-watered control plants, whereas the intolerant varieties showed a significant reduction in both, total spikelet number and grain yield. The metabolomics analysis was conducted with shoot and root samples of plants at the tillering stage at the end of the dry-down treatment. The data revealed an overall higher accumulation of N-rich metabolites (amino acids and nucleotide-related metabolites allantoin and uridine) in shoots of the tolerant varieties. In roots, the aus-type varieties were characterised by a higher reduction of metabolites representative of glycolysis and the TCA cycle, such as malate, glyceric acid and glyceric acid-3-phosphate. On the other hand, the oligosaccharide raffinose showed a higher fold increase in both, shoots and roots of the sensitive genotypes. The data further showed that, for certain drought-responsive metabolites, differences between the contrasting rice varieties were already evident under well-watered control conditions. The drought tolerance-related metabolites identified in the aus-type varieties provide a valuable set of protective compounds and an entry point for assessing genetic diversity in the underlying pathways for developing drought tolerant rice and other crops.

Specific and unspecific responses of plants to cold and drought stress

Indian Academy of Sciences (India)

Madhu Sudhan

2007-03-22

Mar 22, 2007 ... Introduction. Cold, drought and salinity are those environmental stressors which affect .... The general stress concept emphasizing the incidence of a specific primary and a less specific secondary strain by a specific stressor.

Stand-structural effects on Heterobasidion abietinum-related mortality following drought events in Abies pinsapo.

Science.gov (United States)

Linares, Juan Carlos; Camarero, Jesús Julio; Bowker, Matthew A; Ochoa, Victoria; Carreira, José Antonio

2010-12-01

Climate change may affect tree-pathogen interactions. This possibility has important implications for drought-prone forests, where stand dynamics and disease pathogenicity are especially sensitive to climatic stress. In addition, stand structural attributes including density-dependent tree-to-tree competition may modulate the stands' resistance to drought events and pathogen outbreaks. To assess the effects of stand structure on root-rot-related mortality after severe droughts, we focused on Heterobasidion abietinum mortality in relict Spanish stands of Abies pinsapo, a drought-sensitive fir. We compared stand attributes and tree spatial patterns in three plots with H. abietinum root-rot disease and three plots without root-rot. Point-pattern analyses were used to investigate the scale and extent of mortality patterns and to test hypotheses related to the spread of the disease. Dendrochronology was used to date the year of death and to assess the association between droughts and growth decline. We applied a structural equation modelling approach to test if tree mortality occurs more rapidly than predicted by a simple distance model when trees are subjected to high tree-to-tree competition and following drought events. Contrary to expectations of drought mortality, the effect of precipitation on the year of death was strong and negative, indicating that a period of high precipitation induced an earlier tree death. Competition intensity, related to the size and density of neighbour trees, also induced an earlier tree death. The effect of distance to the disease focus was negligible except in combination with intensive competition. Our results indicate that infected trees have decreased ability to withstand drought stress, and demonstrate that tree-to-tree competition and fungal infection act as predisposing factors of forest decline and mortality.

A hybrid framework for assessing maize drought vulnerability in Sub-Saharan Africa

Science.gov (United States)

Kamali, B.; Abbaspour, K. C.; Wehrli, B.; Yang, H.

2017-12-01

Drought has devastating impacts on crop yields. Quantifying drought vulnerability is the first step to better design of mitigation policies. The vulnerability of crop yield to drought has been assessed with different methods, however they lack a standardized base to measure its components and a procedure that facilitates spatial and temporal comparisons. This study attempts to quantify maize drought vulnerability through linking the Drought Exposure Index (DEI) to the Crop Failure Index (CFI). DEI and CFI were defined by fitting probability distribution functions to precipitation and maize yield respectively. To acquire crop drought vulnerability index (CDVI), DEI and CFI were combined in a hybrid framework which classifies CDVI with the same base as DEI and CFI. The analysis were implemented on Sub-Saharan African countries using maize yield simulated with the Environmental Policy Integrated Climate (EPIC) model at 0.5° resolution. The model was coupled with the Sequential Uncertainty Fitting algorithm for calibration at country level. Our results show that Central Africa and those Western African countries located below the Sahelian strip receive higher amount of precipitation, but experience high crop failure. Therefore, they are identified as more vulnerable regions compared to countries such as South Africa, Tanzania, and Kenya. We concluded that our hybrid approach complements information on crop drought vulnerability quantification and can be applied to different regions and scales.

More than just consumers: Integrating local observations into drought monitoring to better support decision making

Science.gov (United States)

Ferguson, D. B.; Masayesva, A.; Meadow, A. M.; Crimmins, M.

2016-12-01

Drought monitoring and drought planning are complex endeavors. Measures of precipitation or streamflow provide little context for understanding how social and environmental systems impacted by drought are responding. In arid and semi-arid regions of the world, this challenge is particularly acute since social-ecological systems are already well-adapted to dry conditions. Understanding what drought means in these regions is an important first step in developing a decision-relevant monitoring system. Traditional drought indices may be of some use, but local observations may ultimately be more relevant for informing difficult decisions in response to unusually dry conditions. This presentation will focus on insights gained from a collaborative project between the University of Arizona and the Hopi Tribe-a Native American community in the U.S. Southwest-to develop a drought information system that is responsive to local needs. The primary goal of the project was to develop a system that: is based on how drought is experienced by Hopi citizens and resource managers, can incorporate local observations of drought impacts as well as conventional indicators, and brings together local expertise with conventional science-based observations. This kind of drought monitoring system can harnesses as much available information as possible to inform resource managers, political leaders, and citizens about drought conditions, but such a system can also engage these local drought stakeholders in observing, thinking about, and helping guide planning for drought.

Identification of conserved drought-adaptive genes using a cross-species meta-analysis approach.

Science.gov (United States)

Shaar-Moshe, Lidor; Hübner, Sariel; Peleg, Zvi

2015-05-03

Drought is the major environmental stress threatening crop-plant productivity worldwide. Identification of new genes and metabolic pathways involved in plant adaptation to progressive drought stress at the reproductive stage is of great interest for agricultural research. We developed a novel Cross-Species meta-Analysis of progressive Drought stress at the reproductive stage (CSA:Drought) to identify key drought adaptive genes and mechanisms and to test their evolutionary conservation. Empirically defined filtering criteria were used to facilitate a robust integration of 17 deposited microarray experiments (148 arrays) of Arabidopsis, rice, wheat and barley. By prioritizing consistency over intensity, our approach was able to identify 225 differentially expressed genes shared across studies and taxa. Gene ontology enrichment and pathway analyses classified the shared genes into functional categories involved predominantly in metabolic processes (e.g. amino acid and carbohydrate metabolism), regulatory function (e.g. protein degradation and transcription) and response to stimulus. We further investigated drought related cis-acting elements in the shared gene promoters, and the evolutionary conservation of shared genes. The universal nature of the identified drought-adaptive genes was further validated in a fifth species, Brachypodium distachyon that was not included in the meta-analysis. qPCR analysis of 27, randomly selected, shared orthologs showed similar expression pattern as was found by the CSA:Drought.In accordance, morpho-physiological characterization of progressive drought stress, in B. distachyon, highlighted the key role of osmotic adjustment as evolutionary conserved drought-adaptive mechanism. Our CSA:Drought strategy highlights major drought-adaptive genes and metabolic pathways that were only partially, if at all, reported in the original studies included in the meta-analysis. These genes include a group of unclassified genes that could be involved

Anatomy of an interrupted irrigation season: Micro-drought at the Wind River Indian Reservation

Directory of Open Access Journals (Sweden)

Shannon M. McNeeley

Full Text Available Drought is a complex phenomenon manifested through interactions between biophysical and social factors. At the Wind River Indian Reservation (WRIR in west-central Wyoming, water shortages have become increasingly common since the turn of the 21st century. Here we discuss the 2015 water year as an exemplar year, which was characterized by wetter-than-normal conditions across the reservation and, according to the U.S. Drought Monitor, remained drought-free throughout the year. Yet parts of the reservation experienced harmful water shortages, or “micro-drought” conditions, during the growing season in 2015. In this assessment of the 2015 water year at the WRIR we: (1 describe the hydroclimatic and social processes under way that contributed to the 2015 water year micro-drought in the Little Wind Basin; (2 compare water availability conditions within and between other basins at the WRIR to illustrate how micro-droughts can result from social and environmental features unique to local systems; and (3 describe how a collaborative project is supporting drought preparedness at the WRIR. We combine a social science assessment with an analysis of the hydroclimate to deconstruct how shortages manifest at the WRIR. We provide insights from this study to help guide drought assessments at local scales. Keywords: Drought, Climate vulnerability, Drought preparedness, Indigenous adaptation, Co-production

Arabidopsis Vacuolar Pyrophosphatase gene (AVP1) induces drought and salt tolerance in Nicotiana tabacum plants (abstract)

International Nuclear Information System (INIS)

Arif, A.; Mohsin, A.M.; Shafiq, S.; Zafar, Y.; Hameed, S.M.; Arif, M.; Javed, M.; Gaxiola, R.A.

2005-01-01

/sup +/ ions from the soil to the vacoules by providing energy gradient to the cation exchangers. It was also found that K/sup +/ concentration decreased below detection limit in salt treated transgenic plants. Sodium and potassium ion uptake in the dehydrated AVP1 transgenic plant was two times more when compared to the dehydrated wild type plants. Relative water contents of dehydrated AVP1 transgenic plants was higher than that of dehydrated wild type which indicates that accumulation of solutes retain more water in the cell which helps to maintain the turgor and allows the plants to survive in saline and water deficit environments. Electron microscopic ultra structure studies of leaves showed that there is an increase of starch synthesis in the chloroplasts of AVP1 transgenic plants when compared to control. Immunogold labeling of AVP1 protein in transgenic and control leaf cells and some other physiological studies are in progress. AVP1 gene is encoded by a single gene so it is more feasible to produce transgenic crop plants with AVP1 to induce salt and drought tolerance unlike P type ATPAases which are encoded by at least 26 genes. (author)

Social, economic and environmental assessment of energy and water desalination options for the Brazilian polygon of drought using the IRIS reactor

International Nuclear Information System (INIS)

Baptista Filho, D. P.; Cegalla, M.; Raduan, R. N.; Barroso, A. C. O.; Molnary, L.; Lima, F. R. A.; Lira, C. A. B. O.; Lima, R. C. F.

2004-01-01

The paper discuss a project conceived to perform a social, economic and environmental assessment of the use of IRIS Reactor for electricity generation and water desalination in the most dry region of Brazil, the Polygon of Drought. The project is financed by the Fund of Energy of the Brazilian Council on Research and Development (CNPq) of the Brazilian Ministry of Science and Technology (MCT), and it will be performed by the Federal University of Pernambuco (UFPe) and the Energetic and Nuclear Research Institute (IPEN) of the Brazilian Nuclear Energy Commission (CNEN). The project will provide comparisons between nuclear and gas options. The final objective of the project is to offer effective evaluations considering the total costs (direct and externalisation) of the different energy options and also the social and environmental aspects associated with them.(author)

Cysteine proteases and wheat (Triticum aestivum L) under drought: A still greatly unexplored association.

Science.gov (United States)

Botha, Anna-Maria; Kunert, Karl J; Cullis, Christopher A

2017-09-01

Bread wheat (Triticum aestivum L.) provides about 19% of global dietary energy. Environmental stress, such as drought, affects wheat growth causing premature plant senescence and ultimately plant death. A plant response to drought is an increase in protease-mediated proteolysis with rapid degradation of proteins required for metabolic processes. Among the plant proteases that are increased in their activity following stress, cysteine proteases are the best characterized. Very little is known about particular wheat cysteine protease sequences, their expression and also localization. The current knowledge on wheat cysteine proteases belonging to the five clans (CA, CD, CE, CF and CP) is outlined, in particular their expression and possible function under drought. The first successes in establishing an annotated wheat genome database are further highlighted which has allowed more detailed mining of cysteine proteases. We also share our thoughts on future research directions considering the growing availability of genomic resources of this very important food crop. Finally, we also outline future application of developed knowledge in transgenic wheat plants for environmental stress protection and also as senescence markers to monitor wheat growth under environmental stress conditions. © 2017 John Wiley & Sons Ltd.

Drought in the Emerald City

International Nuclear Information System (INIS)

Babcock, S.D.

1993-01-01

This paper discusses a drought preparedness study being conducted for the Cedar River and Green River basins in western Washington state. The study is one of four regional case studies being managed by the U.S. Army Corps of Engineers as part of the National Study of Water Management During Drought. The overriding objective of the drought preparedness study is to leave the region better prepared for drought, through demonstration and test of drought preparedness tools and strategies. The study has served as a vehicle to promote a greater regional focus on drought related water supply problem solving. The 1992 drought in the Seattle/Tacoma metropolitan area provided a unique opportunity for the study team to demonstrate approaches to drought management being researched and tested as part of the study

Mapping Drought Sensitivity of Ecosystem Functioning in Mountainous Watersheds: Spatial Heterogeneity and Geological-Geomorphological Control

Science.gov (United States)

Wainwright, H. M.; Steefel, C. F.; Williams, K. H.; Hubbard, S. S.; Enquist, B. J.; Steltzer, H.; Sarah, T.

2016-12-01

Mountainous watersheds in the Upper Colorado River Basin play a critical role in supplying water and nutrients to western North America. Ecosystem functioning in those regions - including plant dynamics and biogeochemical cycling - is known to be limited by water availability. Under the climate change, early snowmelt and increasing temperature are expected to intensify the drought conditions in early growing seasons. Although the impact of early-season drought has been documented in plot-scale experiments, ascertaining its significance in mountainous watersheds is challenging given the highly heterogeneous nature of the systems with complex terrain and diverse plant functional types (PFTs). The objectives of this study are (1) to map the regions where the plant dynamics are relatively more sensitive to drought conditions based on historical satellite and climate data, and (2) to identify the environmental controls (e.g., geomorphology, elevation, geology, snow and PFT) on drought sensitivity. We characterize the spatial heterogeneity of drought sensitivity in four watersheds (a 15 x 15 km domain) near the Rocky Mountain Biological Laboratory in Colorado, USA. Following previous plot-scale studies, we first define the drought sensitivity based on annual peak NDVI (Landsat 5) and climatic datasets. Non-parametric tree-based machine learning methods are used to identify the significant environmental controls, using high-resolution LiDAR digital elevation map and peak snow-water-equivalent distribution from NASA airborne snow observatory. Results show that the drought sensitivity is negatively correlated with elevation, suggesting increased water limitations in lower elevation (less snow, higher temperature). The drought sensitivity is more spatially variable in shallow-rooted plant types, affected by local hydrological conditions. We also found geomorphological and geological controls, such as high sensitivity in the steep well-drained glacial moraine regions. Our

Effect of drought/irrigation on proximate composition and ...

African Journals Online (AJOL)

Enset [Ensete ventricosum (Welw.) Cheesman] is an important root crop serving as a carbohydrate rich food source in Ethiopia. Perennial crops, like enset, are often exposed to recurrent dry periods which could greatly affect their growth, physiology and yield. The effect of induced drought/irrigation on the proximate ...

Sorghum (Sorghum bicolor) varieties adopt strongly contrasting strategies in response to drought.

Science.gov (United States)

Ogbaga, Chukwuma C; Stepien, Piotr; Johnson, Giles N

2014-10-01

Sorghum is one of the most drought tolerant crops but surprisingly, little is known about the mechanisms achieving this. We have compared physiological and biochemical responses to drought in two sorghum cultivars with contrasting drought tolerance. These closely related cultivars have starkly contrasting responses to water deficit. In the less tolerant Samsorg 40, drought induced progressive loss of photosynthesis. The more drought tolerant Samsorg 17 maintained photosynthesis, transpiration and chlorophyll content until the most extreme conditions. In Samsorg 40, there was a highly specific down-regulation of selected proteins, with loss of PSII and Rubisco but maintenance of PSI and cytochrome b6 f, allowing plants to maintain ATP synthesis. The nitrogen released allows for accumulation of glycine betaine and proline. To the best of our knowledge, this is the first example of specific reengineering of the photosynthetic apparatus in response to drought. In contrast, in Samsorg 17 we detected no substantial change in the photosynthetic apparatus. Rather, plants showed constitutively high soluble sugar concentration, enabling them to maintain transpiration and photosynthesis, even in extremely dry conditions. The implications for these strikingly contrasted strategies are discussed in relation to agricultural and natural systems. © 2014 Scandinavian Plant Physiology Society.

Understanding the land-atmospheric interaction in drought forecast from CFSv2 for the 2011 Texas and 2012 Upper Midwest US droughts

Science.gov (United States)

Zhang, Y.; Roundy, J. K.; Ek, M. B.; Wood, E. F.

2015-12-01

Prediction and thus preparedness in advance of hydrological extremes, such as drought and flood events, is crucial for proactively reducing their social and economic impacts. In the summers of 2011 Texas, and 2012 the Upper Midwest, experienced intense droughts that affected crops and the food market in the US. It is expected that seasonal forecasts with sufficient skill would reduce the negative impacts through planning and preparation. However, the forecast skill from models such as Climate Forecast System Version 2 (CFSv2) from National Centers for Environmental Prediction (NCEP) is low over the US, especially during the warm season (Jun - Sep), which restricts their practical use for drought prediction. This study analyzes the processes that lead to premature termination of 2011 and 2012 US summer droughts in CFSv2 forecast resulting in its low forecast skill. Using the North American Land Data Assimilation System version 2 (NLDAS2) and Climate Forecast System Reanalysis (CFSR) as references, this study investigates the forecast skills of CFSv2 initialized at 00, 06, 12, 18z from May 15 - 31 (leads out to September) for each event in terms of land-atmosphere interaction, through a recently developed Coupling Drought Index (CDI), which is based on the Convective Triggering Potential-Humidity Index-soil moisture (CTP-HI-SM) classification of four climate regimes: wet coupling, dry coupling, transitional and atmospherically controlled. A recycling model is used to trace the moisture sources in the CFSv2 forecasts of anomalous precipitation, which lead to the breakdown of drought conditions and a lack of drought forecasting skills. This is then compared with tracing the moisture source in CFSR with the same recycling model, which is used as the verification for the same periods. This helps to identify the parameterization that triggered precipitation in CFSv2 during 2011 and 2012 summer in the US thus has the potential to improve the forecast skill of CSFv2.

Overexpression of an Arabidopsis heterogeneous nuclear ribonucleoprotein gene, AtRNP1, affects plant growth and reduces plant tolerance to drought and salt stresses

International Nuclear Information System (INIS)

Wang, Zhenyu; Zhao, Xiuyang; Wang, Bing; Liu, Erlong; Chen, Ni; Zhang, Wei; Liu, Heng

2016-01-01

Heterogeneous nuclear ribonucleoproteins (hnRNPs) participate in diverse regulations of plant growth and environmental stress responses. In this work, an Arabidopsis hnRNP of unknown function, AtRNP1, was investigated. We found that AtRNP1 gene is highly expressed in rosette and cauline leaves, and slightly induced under drought, salt, osmotic and ABA stresses. AtRNP1 protein is localized to both the nucleus and cytoplasm. We performed homologous overexpression of AtRNP1 and found that the transgenic plants showed shortened root length and plant height, and accelerated flowering. In addition, the transgenic plants also showed reduced tolerance to drought, salt, osmotic and ABA stresses. Further studies revealed that under both normal and stress conditions, the proline contents in the transgenic plants are markedly decreased, associated with reduced expression levels of a proline synthase gene and several stress-responsive genes. These results suggested that the overexpression of AtRNP1 negatively affects plant growth and abiotic stress tolerance. - Highlights: • AtRNP1 is a widely expressed gene and its expression is slightly induced under abiotic stresses. • AtRNP1 protein is localized to both the nucleus and cytoplasm. • Overexpression of AtRNP1 affects plant growth. • Overexpression of AtRNP1 reduces plant tolerance to drought and salt stresses. • AtRNP1 overexpression plants show decreased proline accumulation and stress-responsive gene expressions.

Overexpression of an Arabidopsis heterogeneous nuclear ribonucleoprotein gene, AtRNP1, affects plant growth and reduces plant tolerance to drought and salt stresses

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhenyu, E-mail: wzy72609@163.com [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China); Zhao, Xiuyang, E-mail: xiuzh@psb.vib-ugent.be [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China); Wang, Bing, E-mail: wangbing@ibcas.ac.cn [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China); Liu, Erlong, E-mail: liuel14@lzu.edu.cn [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China); Chen, Ni, E-mail: 63710156@qq.com [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China); Zhang, Wei, E-mail: wzhang1216@yahoo.com [Shanghai Key Laboratory of Bio-Energy Crops, School of Life Sciences, Shanghai University, Shanghai 200444 (China); Liu, Heng, E-mail: hengliu@lzu.edu.cn [Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730030 (China)

2016-04-01

Heterogeneous nuclear ribonucleoproteins (hnRNPs) participate in diverse regulations of plant growth and environmental stress responses. In this work, an Arabidopsis hnRNP of unknown function, AtRNP1, was investigated. We found that AtRNP1 gene is highly expressed in rosette and cauline leaves, and slightly induced under drought, salt, osmotic and ABA stresses. AtRNP1 protein is localized to both the nucleus and cytoplasm. We performed homologous overexpression of AtRNP1 and found that the transgenic plants showed shortened root length and plant height, and accelerated flowering. In addition, the transgenic plants also showed reduced tolerance to drought, salt, osmotic and ABA stresses. Further studies revealed that under both normal and stress conditions, the proline contents in the transgenic plants are markedly decreased, associated with reduced expression levels of a proline synthase gene and several stress-responsive genes. These results suggested that the overexpression of AtRNP1 negatively affects plant growth and abiotic stress tolerance. - Highlights: • AtRNP1 is a widely expressed gene and its expression is slightly induced under abiotic stresses. • AtRNP1 protein is localized to both the nucleus and cytoplasm. • Overexpression of AtRNP1 affects plant growth. • Overexpression of AtRNP1 reduces plant tolerance to drought and salt stresses. • AtRNP1 overexpression plants show decreased proline accumulation and stress-responsive gene expressions.

Silicon alleviates the adverse effects of salinity and drought stress on growth and endogenous plant growth hormones of soybean (glycine max L.)

International Nuclear Information System (INIS)

Hamzyun, M.; Sohn, Eun-Young; Khan, A.L.; Lee, In-Jung

2010-01-01

Agricultural industry is subjected to enormous environmental constraints, particularly due to salinity and drought. We evaluated the role of silicon (Si) in alleviating salinity and drought induced physio-hormonal changes in soybean grown in perlite. The plant growth attributes i.e., shoot length, plant fresh weight and dry weight parameters of soybean improved with elevated Si nutrition, while they decreased with NaCl and polyethylene glycol (PEG) application. The adverse effects of NaCl and PEG on plant growth were alleviated by adding 100 mg L/sup -1/ and 200 mg L/sup -1/ Si to salt and drought stressed treatments. It was observed that Si effectively mitigated the adverse effects of NaCl on soybean than that of PEG. The chlorophyll contents were found to be least affected as an insignificant increase was observed with Si application. Bioactive GA1 and GA4 contents of soybean leaves increased, when Si was added to control or stressed plants. Jasmonic acid (JA) contents sharply increased under salinity and drought stress but declined when the plants were supplemented with Si. Similarly, free salicylic acid (SA) level also increased with NaCl and PEG application. However, free SA level further increased with the addition of Si to salt treated plants, but decreased when Si was given to PEG treated plants. It was concluded that Si improves physio-hormonal attributes of soybean and mitigate adverse effects of salt and drought stress. (author)

Unprecedented drought over tropical South America in 2016: significantly under-predicted by tropical SST.

Science.gov (United States)

Erfanian, Amir; Wang, Guiling; Fomenko, Lori

2017-07-19

Tropical and sub-tropical South America are highly susceptible to extreme droughts. Recent events include two droughts (2005 and 2010) exceeding the 100-year return value in the Amazon and recurrent extreme droughts in the Nordeste region, with profound eco-hydrological and socioeconomic impacts. In 2015-2016, both regions were hit by another drought. Here, we show that the severity of the 2015-2016 drought ("2016 drought" hereafter) is unprecedented based on multiple precipitation products (since 1900), satellite-derived data on terrestrial water storage (since 2002) and two vegetation indices (since 2004). The ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic are used to assess the role of tropical oceanic variability in the observed precipitation anomalies. Our results indicate that warmer-than-usual SSTs in the Tropical Pacific (including El Niño events) and Atlantic were the main drivers of extreme droughts in South America, but are unable to explain the severity of the 2016 observed rainfall deficits for a substantial portion of the Amazonia and Nordeste regions. This strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought.

Identification of the influencing factors on groundwater drought and depletion in north-western Bangladesh

Science.gov (United States)

Mustafa, Syed Md. Touhidul; Abdollahi, Khodayar; Verbeiren, Boud; Huysmans, Marijke

2017-08-01

Groundwater drought is a specific type of hydrological drought that concerns groundwater bodies. It may have a significant adverse effect on the socio-economic, agricultural, and environmental conditions. Investigating the effect of different climatic and anthropogenic factors on groundwater drought provides essential information for sustainable planning and management of (ground) water resources. The aim of this study is to identify the influencing factors on groundwater drought in north-western Bangladesh, to understand the forcing mechanisms. A multi-step methodology is proposed to achieve this objective. The standardised precipitation index (SPI) and reconnaissance drought index (RDI) have been used to quantify the aggregated deficit between precipitation and the evaporative demand of the atmosphere, i.e. meteorological drought. The influence of land-cover patterns on the groundwater drought has been identified by calculating spatially distributed groundwater recharge as a function of land cover. Groundwater drought is defined by a threshold method. The results show that the evapotranspiration and rainfall deficits are determining meteorological drought, which shows a direct relation with groundwater recharge deficits. Land-cover change has a small effect on groundwater recharge but does not seem to be the main cause of groundwater-level decline (depletion) in the study area. The groundwater depth and groundwater-level deficit (drought) is continuously increasing with little correlation to meteorological drought or recharge anomalies. Overexploitation of groundwater for irrigation seems to be the main cause of groundwater-level decline in the study area. Efficient irrigation management is essential to reduce the growing pressure on groundwater resources and ensure sustainable water management.

Integration of transcriptomic and metabolic data reveals hub transcription factors involved in drought stress response in sunflower (Helianthus annuus L.).

Science.gov (United States)

Moschen, Sebastián; Di Rienzo, Julio A; Higgins, Janet; Tohge, Takayuki; Watanabe, Mutsumi; González, Sergio; Rivarola, Máximo; García-García, Francisco; Dopazo, Joaquin; Hopp, H Esteban; Hoefgen, Rainer; Fernie, Alisdair R; Paniego, Norma; Fernández, Paula; Heinz, Ruth A

2017-07-01

By integration of transcriptional and metabolic profiles we identified pathways and hubs transcription factors regulated during drought conditions in sunflower, useful for applications in molecular and/or biotechnological breeding. Drought is one of the most important environmental stresses that effects crop productivity in many agricultural regions. Sunflower is tolerant to drought conditions but the mechanisms involved in this tolerance remain unclear at the molecular level. The aim of this study was to characterize and integrate transcriptional and metabolic pathways related to drought stress in sunflower plants, by using a system biology approach. Our results showed a delay in plant senescence with an increase in the expression level of photosynthesis related genes as well as higher levels of sugars, osmoprotectant amino acids and ionic nutrients under drought conditions. In addition, we identified transcription factors that were upregulated during drought conditions and that may act as hubs in the transcriptional network. Many of these transcription factors belong to families implicated in the drought response in model species. The integration of transcriptomic and metabolomic data in this study, together with physiological measurements, has improved our understanding of the biological responses during droughts and contributes to elucidate the molecular mechanisms involved under this environmental condition. These findings will provide useful biotechnological tools to improve stress tolerance while maintaining crop yield under restricted water availability.

Global Reprogramming of Transcription in Chinese Fir (Cunninghamia lanceolata during Progressive Drought Stress and after Rewatering

Directory of Open Access Journals (Sweden)

Ruiyang Hu

2015-07-01

Full Text Available Chinese fir (Cunninghamia lanceolata, an evergreen conifer, is the most commonly grown afforestation species in southeast China due to its rapid growth and good wood qualities. To gain a better understanding of the drought-signalling pathway and the molecular metabolic reactions involved in the drought response, we performed a genome-wide transcription analysis using RNA sequence data. In this study, Chinese fir plantlets were subjected to progressively prolonged drought stress, up to 15 d, followed by rewatering under controlled environmental conditions. Based on observed morphological changes, plantlets experienced mild, moderate, or severe water stress before rehydration. Transcriptome analysis of plantlets, representing control and mild, moderate, and severe drought-stress treatments, and the rewatered plantlets, identified several thousand genes whose expression was altered in response to drought stress. Many genes whose expression was tightly coupled to the levels of drought stress were identified, suggesting involvement in Chinese fir drought adaptation responses. These genes were associated with transcription factors, signal transport, stress kinases, phytohormone signalling, and defence/stress response. The present study provides the most comprehensive transcriptome resource and the first dynamic transcriptome profiles of Chinese fir under drought stress. The drought-responsive genes identified in this study could provide further information for understanding the mechanisms of drought tolerance in Chinese fir.

Assessing Agricultural Drought in the Anthropocene: A Modified Palmer Drought Severity Index

Directory of Open Access Journals (Sweden)

Mingzhi Yang

2017-09-01

Full Text Available In the current human-influenced era, drought is initiated by natural and human drivers, and human activities are as integral to drought as meteorological factors. In large irrigated agricultural regions with high levels of human intervention, where the natural farmland soil moisture has usually been changed significantly by high-frequency irrigation, the actual severity of agricultural drought is distorted in traditional drought indices. In this work, an agricultural drought index that considering irrigation processes based on the Palmer drought severity index (IrrPDSI was developed to interpret the real agricultural drought conditions in irrigated regions, with a case study in the Haihe River Basin in northeast China. The water balance model in the original PDSI was revised by an auto-irrigation threshold method combined with a local irrigation schedule. The auto-irrigation setting of the index was used by taking irrigation quotas during specific growth stages of specific crops (wheat–corn into consideration. A series of weekly comparative analyses are as follows: (1 The soil moisture analyses showed that soil moisture values calculated by the modified water balance model were close to the real values; (2 The statistical analyses indicated that most of the stations in the study area based on IrrPDSI had nearly normal distributed values; (3 The time series and spatial analyses showed that the results of the IrrPDSI-reported dry-wet evaluation were more consistent with documented real conditions. All the results revealed that IrrPDSI performed well when used to assess agricultural drought. This work has direct significance for agricultural drought management in large irrigated areas heavily disturbed by human activity.

Analysis of Droughts of Northwest of Iran Using the Reconnaissance Drought Index

Directory of Open Access Journals (Sweden)

behrouz hosseini

2016-02-01

Full Text Available Introduction: Drought is a creeping natural phenomenon, which can occur in any region. Such phenomenon not only affects the region subjected to drought, but its adverse effects can also be extended to other adjacent regions. This phenomenon mainly starts with water deficiency (say less than long- term mean of variable under study such as rainfall, streamflow, groundwater level or soil moisture and progress in time. This period can be ended by increasing the rainfall and reaching the mean level. Even after the ending of a drought period, its adverse effects can be continued for several months. Although, it is not possible (at least at this time to prevent the occurrence of drought in a given region, it is not impossible to alleviate the drought consequences by scientific water management. Such a management should be employed before drought initiation as well as during it and continue on even after the end of the drought period. The frequency of the main drought characteristics is a major concern of this study. The Northwest of Iran recently encountered severe and prolonged droughts, such that a major portion of the Urmia Lake surface disappeared during the last drought in recent years. In order to study drought characteristics, we used the Reconnaissance Drought Index (RDI. This index is based on annual rainfall and potential reference crop evapotranspiration (abbreviated by PET here. This study employed the Monte Carlo simulation technique for synthetic data generation for analysis. Materials and Methods: The information from the 17 synoptic weather stations located in the North-west of Iran was used for drought analysis. Data was gathered from the Islamic Republic of Iran’s Meteorological Organization (IRIMO. In the first stage of research, the ratio of long term mean annual precipitation to evapotranspiration was calculated for each of the stations. For this purpose, the Penman-Montheis (FAO 56 method was selected for PET estimation. In the

Effect of SiO2 nanoparticles on drought resistance in hawthorn seedlings

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Ashkavand Peyman

2015-12-01

Full Text Available Drought is a significant factor limiting crop production in arid regions while hawthorns (Crataegus sp. are an important component of such region’s forests. Therefore, treatments that increase hawthorn drought resistance may also increase transplanting success. Thus, the physiological and biochemical responses of hawthorn seedlings to a factorial combination of different concentrations of silica nanoparticles (SNPs at 0, 10, 50 and 100 mg L−1 and three soil moisture treatments (without stress, moderate stress and severe stress were investigated. Seedlings were irrigated with one of the four concentrations of SNPs for 45 days before exposing them to drought stress. Photosynthesis parameters, malondialdehyde (MDA, relative water content (RWC, membrane electrolyte leakage (ELI as well as chlorophyll, carotenoid, carbohydrate and proline content were determined. At the end of the experiment, positive effects by SNP pre-treatment on physiological indexes were observed during drought stress. Under drought conditions, the effect of SNPs on photosynthetic rate and stomatal conductance was evident. Although the SNPs increased plant biomass, xylem water potential and MDA content, especially under drought conditions, RWC and ELI were not affected by the SNP pre-treatments. Seedlings pre-treated with SNPs had a decreased carbohydrate and proline content under all water regimes, but especially so under drought. Total chlorophyll content and carotenoid content did not change among the treatments. Generally, the findings imply that SNPs play a positive role in maintaining critical physiological and biochemical functions in hawthorn seedlings under drought stress conditions. However, more studies are needed before the physiological and biochemical basis of induced drought resistance can be determined.

Changing household responses to drought in Tharaka, Kenya: vulnerability, persistence and challenge.

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Smucker, Thomas A; Wisner, Ben

2008-06-01

Drought is a recurring challenge to the livelihoods of those living in Tharaka District, Kenya, situated in the semi-arid zone to the east of Mount Kenya, from the lowest slopes of the mountain to the banks of the Tana River. This part of Kenya has been marginal to the economic and political life of Kenya from the colonial period until the present day. A study of more than 30 years of change in how people in Tharaka cope with drought reveals resilience in the face of major macro-level transformations, which include privatisation of landownership, population growth, political decentralisation, increased conflict over natural resources, different market conditions, and environmental shifts. However, the study also shows troubling signs of increased use of drought responses that are incompatible with long-term agrarian livelihoods. Government policy needs to address the challenge of drought under these new macro conditions if sustainable human development is to be achieved.

Climate Changes and the Role of Recent Droughts on Agricultural Economy of Sistan

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ISSA EBRAHIMZADEH

2013-01-01

Full Text Available Regional economy is usually affected by the operation and interaction of environment and human beings in geographical spaces. Warm and dry areas create special economic conditions, which have particular functions, quite different from the characteristics of humid and cold hilly areas or those of the Mediterranean areas. The Sistan Region is located in South East of Iran. Until recent droughts (1999-2005, agriculture sector was the basis of all economic activities in Sistan area, a major share of rural as well as urban income came directly and indirectly from agricultural activities. In accordance with the latest census before the drought period (1996, about 55 percent of the rural population directly depended on the agriculture sector for their income and employment. In addition, almost 24 percent of rural population was depended to cottage and rural industries for their employments. In urban areas, 70 percent of population was linked to service sector as a source of employment. The results of this research show that the environmental changes resulting from drought in Sistan area have had deep impacts on the socio-economic factors in the region. It is clearer in the Hamoon Lake area, which, before the onset drought, had produced crops like fodders, mat, bird meat and fish. The livestock sector also suffered to a great extent. Out of the total of 1.6 million livestock units in the area, more than 0.5 million remained in the production cycle nowadays. The production of these crops reduced to zero with drought. The total direct loss resulted from the drought amounts to 14,057,332 million Rails or 1,561 billion US$. To sum up, the environmental changes resulting from drought caused more than 80 percent of agricultural and livestock activities in the region come to halt, which, in turn, due to a reduced income multiplier effect of agriculture sector resulted in greater damage to socio-economic factors in rural, as well as in urban areas.

Comparative Physiological and Molecular Analyses of Two Contrasting Flue-Cured Tobacco Genotypes under Progressive Drought Stress

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Xinhong Su

2017-05-01

Full Text Available Drought is a major environmental factor that limits crop growth and productivity. Flue-cured tobacco (Nicotiana tabacum is one of the most important commercial crops worldwide and its productivity is vulnerable to drought. However, comparative analyses of physiological, biochemical and gene expression changes in flue-cured tobacco varieties differing in drought tolerance under long-term drought stress are scarce. In this study, drought stress responses of two flue-cured tobacco varieties, LJ851 and JX6007, were comparatively studied at the physiological and transcriptional levels. After exposing to progressive drought stress, the drought-tolerant LJ851 showed less growth inhibition and chlorophyll reduction than the drought-sensitive JX6007. Moreover, higher antioxidant enzyme activities and lower levels of H2O2, Malondialdehyde (MDA, and electrolyte leakage after drought stress were found in LJ851 when compared with JX6007. Further analysis showed that LJ851 plants had much less reductions than the JX6007 in the net photosynthesis rate and stomatal conductance during drought stress; indicating that LJ851 had better photosynthetic performance than JX6007 during drought. In addition, transcriptional expression analysis revealed that LJ851 exhibited significantly increased transcripts of several categories of drought-responsive genes in leaves and roots under drought conditions. Together, these results indicated that LJ851 was more drought-tolerant than JX6007 as evidenced by better photosynthetic performance, more powerful antioxidant system, and higher expression of stress defense genes during drought stress. This study will be valuable for the development of novel flue-cured tobacco varieties with improved drought tolerance by exploitation of natural genetic variations in the future.

Amazon Forests’ Response to Droughts: A Perspective from the MAIAC Product

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Jian Bi

2016-04-01

Full Text Available Amazon forests experienced two severe droughts at the beginning of the 21st century: one in 2005 and the other in 2010. How Amazon forests responded to these droughts is critical for the future of the Earth’s climate system. It is only possible to assess Amazon forests’ response to the droughts in large areal extent through satellite remote sensing. Here, we used the Multi-Angle Implementation of Atmospheric Correction (MAIAC Moderate Resolution Imaging Spectroradiometer (MODIS vegetation index (VI data to assess Amazon forests’ response to droughts, and compared the results with those from the standard (Collection 5 and Collection 6 MODIS VI data. Overall, the MAIAC data reveal more realistic Amazon forests inter-annual greenness dynamics than the standard MODIS data. Our results from the MAIAC data suggest that: (1 the droughts decreased the greenness (i.e., photosynthetic activity of Amazon forests; (2 the Amazon wet season precipitation reduction induced by El Niño events could also lead to reduced photosynthetic activity of Amazon forests; and (3 in the subsequent year after the water stresses, the greenness of Amazon forests recovered from the preceding decreases. However, as previous research shows droughts cause Amazon forests to reduce investment in tissue maintenance and defense, it is not clear whether the photosynthesis of Amazon forests will continue to recover after future water stresses, because of the accumulated damages caused by the droughts.

Experimental droughts: Are precipitation variability and methodological trends hindering our understanding of ecological sensitivities to drought?

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Hoover, D. L.; Wilcox, K.; Young, K. E.

2017-12-01

Droughts are projected to increase in frequency and intensity with climate change, which may have dramatic and prolonged effects on ecosystem structure and function. There are currently hundreds of published, ongoing, and new drought experiments worldwide aimed to assess ecosystem sensitivities to drought and identify the mechanisms governing ecological resistance and resilience. However, to date, the results from these experiments have varied widely, and thus patterns of drought sensitivities have been difficult to discern. This lack of consensus at the field scale, limits the abilities of experiments to help improve land surface models, which often fail to realistically simulate ecological responses to extreme events. This is unfortunate because models offer an alternative, yet complementary approach to increase the spatial and temporal assessment of ecological sensitivities to drought that are not possible in the field due to logistical and financial constraints. Here we examined 89 published drought experiments, along with their associated historical precipitation records to (1) identify where and how drought experiments have been imposed, (2) determine the extremity of drought treatments in the context of historical climate, and (3) assess the influence of precipitation variability on drought experiments. We found an overall bias in drought experiments towards short-term, extreme experiments in water-limited ecosystems. When placed in the context of local historical precipitation, most experimental droughts were extreme, with 61% below the 5th, and 43% below the 1st percentile. Furthermore, we found that interannual precipitation variability had a large and potentially underappreciated effect on drought experiments due to the co-varying nature of control and drought treatments. Thus detecting ecological effects in experimental droughts is strongly influenced by the interaction between drought treatment magnitude, precipitation variability, and key

Spatiotemporal dynamics of historical droughts over Canada: role of observational uncertainties and teleconnections

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Asong, Z. E.; Wheater, H. S.; Bonsal, B. R.; Razavi, S.; Kurkute, S.

2017-12-01

Drought is a naturally occurring environmental phenomenon, and a major costly natural hazard that can have devastating impacts on regional water resources, agriculture, energy and other social-ecological systems. Of particular interest here is drought occurrence over Canada, where drought is both a frequent and damaging phenomenon, particularly in the interior Prairie region. However, nation-wide drought assessments are currently lacking and hampered partly by observational uncertainties. Therefore, this study aims to fill these gaps by providing a comprehensive analysis of historical droughts over the whole of Canada, including the role of observational uncertainties and teleconnectivity. This is carried out by analysing different monthly precipitation and temperature products for the period 1950 - 2013. Drought events are characterized by the Standardized Precipitation-Evapotranspiration Index (SPEI) over various temporal scales (1, 3, 6, and 12 consecutive months and 6 months from April to September and 12 months from October to September). First, trends in the SPEI are investigated by means of the Modified Mann Kendall test, while the Pettitt test was used to detect change points/transition years during the period of record. Major spatial patterns of long-term change, inter/intra-annual variability and periodicity of drought events are then characterized using the Rotated Empirical Orthogonal Function, and Continuous Wavelet Transform techniques. In addition, potential key drivers of drought are investigated using Wavelet Coherence Analysis, with a special emphasis on the role played by large-scale modes of climate variability. This provides important insight into the physical and dynamical mechanisms associated with the variability of drought events over different Canadian sub-regions.

Drought impacts on vegetation dynamics in the Mediterranean based on remote sensing and multi-scale drought indices

Science.gov (United States)

Trigo, Ricardo; Gouveia, Celia M.; Beguería, Santiago; Vicente-Serrano, Sergio

2015-04-01

Sciences, 12, 3123-3137, 2012. Trigo R.M., Añel J., Barriopedro D., García-Herrera R., Gimeno L., Nieto R., Castillo R., Allen M.R., Massey N. (2013), The record Winter drought of 2011-12 in the Iberian Peninsula [in "Explaining Extreme Events of 2012 from a Climate Perspective". [Peterson, T. C., M. P. Hoerling, P.A. Stott and S. Herring, Eds.] Bulletin of the American Meteorological Society, 94 (9), S41-S45. Vicente-Serrano S.M., López-Moreno J.I., Beguería S., Lorenzo-Lacruz J., Sanchez-Lorenzo A., García-Ruiz J.M., Azorin-Molina C., Móran-Tejeda E., Revuelto J., Trigo R., Coelho F., Espejo F.: Evidence of increasing drought severity caused by temperature rise in southern Europe. Environmental Research Letters, 9, 044001, 2014. Acknowledgements: This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project QSECA (PTDC/AAGGLO/4155/2012).

Virus-induced down-regulation of GmERA1A and GmERA1B genes enhances the stomatal response to abscisic acid and drought resistance in soybean.

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Takuya Ogata

Full Text Available Drought is a major threat to global soybean production. The limited transformation potential and polyploid nature of soybean have hindered functional analysis of soybean genes. Previous research has implicated farnesylation in the plant's response to abscisic acid (ABA and drought tolerance. We therefore used virus-induced gene silencing (VIGS to evaluate farnesyltransferase genes, GmERA1A and GmERA1B (Glycine max Enhanced Response to ABA1-A and -B, as potential targets for increasing drought resistance in soybean. Apple latent spherical virus (ALSV-mediated GmERA1-down-regulated soybean leaves displayed an enhanced stomatal response to ABA and reduced water loss and wilting under dehydration conditions, suggesting that GmERA1A and GmERA1B negatively regulate ABA signaling in soybean guard cells. The findings provide evidence that the ALSV-VIGS system, which bypasses the need to generate transgenic plants, is a useful tool for analyzing gene function using only a single down-regulated leaf. Thus, the ALSV-VIGS system could constitute part of a next-generation molecular breeding pipeline to accelerate drought resistance breeding in soybean.

Physiological and molecular responses to drought in Petunia: the importance of stress severity

Science.gov (United States)

Kim, Jongyun

2012-01-01

Plant responses to drought stress vary depending on the severity of stress and the stage of drought progression. To improve the understanding of such responses, the leaf physiology, abscisic acid (ABA) concentration, and expression of genes associated with ABA metabolism and signalling were investigated in Petunia × hybrida. Plants were exposed to different specific substrate water contents (θ = 0.10, 0.20, 0.30, or 0.40 m3·m–3) to induce varying levels of drought stress. Plant responses were investigated both during the drying period (θ decreased to the θ thresholds) and while those threshold θ were maintained. Stomatal conductance (gs) and net photosynthesis (A) decreased with decreasing midday leaf water potential (Ψleaf). Leaf ABA concentration increased with decreasing midday Ψleaf and was negatively correlated with gs (r = –0.92). Despite the increase in leaf ABA concentration under drought, no significant effects on the expression of ABA biosynthesis genes were observed. However, the ABA catabolism-related gene CYP707A2 was downregulated, primarily in plants under severe drought (θ = 0.10 m3∙m–3), suggesting a decrease in ABA catabolism under severe drought. Expression of phospholipase Dα (PLDα), involved in regulating stomatal responses to ABA, was enhanced under drought during the drying phase, but there was no relationship between PLDα expression and midday Ψleaf after the θ thresholds had been reached. The results show that drought response of plants depends on the severity of drought stress and the phase of drought progression. PMID:23077204

Effect of Experimentally Manipulated Fire Regimes on the Response of Forests to Drought

Science.gov (United States)

Refsland, T. K.; Knapp, B.; Fraterrigo, J.

2017-12-01

Climate change is expected to increase drought stress in many forests and alter fire regimes. Fire can reduce tree density and thus competition for limited water, but the effects of changing fire regimes on forest productivity during drought remain poorly understood. We measured the annual ring-widths of adult oak (Quercus spp.) trees in Mark Twain National Forest, Missouri USA that experienced unburned, annual or periodic (every 4 years) surface fire treatments from 1951 - 2015. Severe drought events were identified using the BILJOU water balance model. We determined the effect of fire treatment on stand-level annual growth rates as well as stand-level resistance and resilience to drought, defined as the drought-induced reduction in growth and post-drought recovery in growth, respectively. During favorable wet years, annual and periodic fire treatments reduced annual growth rates by approximately 10-15% relative to unburned controls (P burned stands during favorable wet years was likely caused by increased nitrogen (N) limitation in burned plots. After 60 years of treatment, burned plots experienced 30% declines in total soil N relative to unburned plots. Our finding that drought resistance and resilience were similar across all treatments suggest that fire-driven reductions in stand density may have negligible effects on soil moisture availability during drought. Our results highlight that climate-fire interactions can have important long-term effects on forest productivity.

Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought

NARCIS (Netherlands)

Carnicer, Jofre; Coll, Marta; Ninyerola, Miquel; Pons, Xavier; Sanchez, Gerardo; Penuelas, Josep

2011-01-01

Climate change is progressively increasing severe drought events in the Northern Hemisphere, causing regional tree die-off events and contributing to the global reduction of the carbon sink efficiency of forests. There is a critical lack of integrated community-wide assessments of drought-induced

USGS integrated drought science

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Ostroff, Andrea C.; Muhlfeld, Clint C.; Lambert, Patrick M.; Booth, Nathaniel L.; Carter, Shawn L.; Stoker, Jason M.; Focazio, Michael J.

2017-06-05

Project Need and OverviewDrought poses a serious threat to the resilience of human communities and ecosystems in the United States (Easterling and others, 2000). Over the past several years, many regions have experienced extreme drought conditions, fueled by prolonged periods of reduced precipitation and exceptionally warm temperatures. Extreme drought has far-reaching impacts on water supplies, ecosystems, agricultural production, critical infrastructure, energy costs, human health, and local economies (Milly and others, 2005; Wihlite, 2005; Vörösmarty and others, 2010; Choat and others, 2012; Ledger and others, 2013). As global temperatures continue to increase, the frequency, severity, extent, and duration of droughts are expected to increase across North America, affecting both humans and natural ecosystems (Parry and others, 2007).The U.S. Geological Survey (USGS) has a long, proven history of delivering science and tools to help decision-makers manage and mitigate effects of drought. That said, there is substantial capacity for improved integration and coordination in the ways that the USGS provides drought science. A USGS Drought Team was formed in August 2016 to work across USGS Mission Areas to identify current USGS drought-related research and core capabilities. This information has been used to initiate the development of an integrated science effort that will bring the full USGS capacity to bear on this national crisis.

A Look into the National Drought Mitigation Center: Providing 15 Years of Drought Services (Invited)

Science.gov (United States)

Svoboda, M. D.; Hayes, M. J.; Knutson, C. L.; Wardlow, B. D.

2009-12-01

The National Drought Mitigation Center (NDMC) was formed in 1995 at the University of Nebraska-Lincoln. Over the past 15 years, the NDMC has made it a priority to work with various local, state, tribal and federal entities to provide a suite of drought/climate services, with a goal of bringing research to fruition through applications and operations. Through our research and outreach projects, the NDMC has worked to reduce risk to drought by developing several mitigation strategies, monitoring and decision making tools and other services aimed at enhancing our nation’s capacity to cope with drought. Two of the earliest NDMC activities were the creation of a website and assessing drought conditions around the United States. An electronic drought clearinghouse was built in 1995 at drought.unl.edu. The site was designed, and still concentrates, on the concepts of drought monitoring, planning, and mitigation and also serves as a repository of information from around the world. The NDMC’s electronic quarterly newsletter, DroughtScape, disseminates information about all things drought to people across the country. In addition, the NDMC has developed and is home to websites for the U.S. Drought Monitor (USDM), Drought Impact Reporter (DIR), and the Vegetation Drought Response Index (VegDRI). In an effort to inform decision makers, the NDMC continually pursues ways to raise the awareness and visibility of drought as one of the most costly hazards we face. This began in the mid-1990s with the creation of a state-based drought impact assessment map that would help lead to the formation of the USDM in 1999 and the DIR in 2005. The NDMC plays a key role in producing the weekly USDM and the monthly North American Drought Monitor (NADM). The USDM was created out of collaborations between the NDMC, United States Department of Agriculture (USDA) and National Oceanic and Atmospheric Administration (NOAA) and has quickly become one of the most widely used products in assessing

Towards Improved Understanding of Drought and Drought Impacts from Long Term Earth Observation Records

Science.gov (United States)

Champagne, C.; Wang, S.; Liu, J.; Hadwen, T. A.

2017-12-01

Drought is a complex natural disaster, which often emerges slowly, but can occur at various time scales and have impacts that are not well understood. Long term observations of drought intensity and frequency are often quantified from precipitation and temperature based indices or modelled estimates of soil water storage. The maturity of satellite based observations has created the potential to enhance the understanding of drought and drought impacts, particularly in regions where traditional data sets are limited by remoteness or inaccessibility, and where drought processes are not well-quantified by models. Long term global satellite data records now provide observations of key hydrological variables, including evaporation modelled from thermal sensors, soil moisture from microwave sensors, ground water from gravity sensors and vegetation condition that can be modelled from optical sensors. This study examined trends in drought frequency, intensity and duration over diverse ecoregions in Canada, including agricultural, grassland, forested and wetland areas. Trends in drought were obtained from the Canadian Drought Monitor as well as meteorological based indices from weather stations, and evaluated against satellite derived information on evaporative stress (Anderson et al. 2011), soil moisture (Champagne et al. 2015), terrestrial water storage (Wang and Li 2016) and vegetation condition (Davidson et al. 2009). Data sets were evaluated to determine differences in how different sensors characterize the hydrology and impacts of drought events from 2003 to 2016. Preliminary results show how different hydrological observations can provide unique information that can tie causes of drought (water shortages resulting from precipitation, lack of moisture storage or evaporative stress) to impacts (vegetation condition) that hold the potential to improve the understanding and classification of drought events.

Modeling water scarcity and droughts for policy adaptation to climate change in arid and semiarid regions

Science.gov (United States)

Kahil, Mohamed Taher; Dinar, Ariel; Albiac, Jose

2015-03-01

Growing water extractions combined with emerging demands for environment protection increase competition for scarce water resources worldwide, especially in arid and semiarid regions. In those regions, climate change is projected to exacerbate water scarcity and increase the recurrence and intensity of droughts. These circumstances call for methodologies that can support the design of sustainable water management. This paper presents a hydro-economic model that links a reduced form hydrological component, with economic and environmental components. The model is applied to an arid and semiarid basin in Southeastern Spain to analyze the effects of droughts and to assess alternative adaptation policies. Results indicate that drought events have large impacts on social welfare, with the main adjustments sustained by irrigation and the environment. The water market policy seems to be a suitable option to overcome the negative economic effects of droughts, although the environmental effects may weaken its advantages for society. The environmental water market policy, where water is acquired for the environment, is an appealing policy to reap the private benefits of markets while protecting ecosystems. The current water management approach in Spain, based on stakeholders' cooperation, achieves almost the same economic outcomes and better environmental outcomes compared to a pure water market. These findings call for a reconsideration of the current management in arid and semiarid basins around the world. The paper illustrates the potential of hydro-economic modeling for integrating the multiple dimensions of water resources, becoming a valuable tool in the advancement of sustainable water management policies.

Drought stress had a predominant effect over heat stress on three tomato cultivars subjected to combined

DEFF Research Database (Denmark)

Zhou, Rong; Yu, Xiaqing; Ottosen, Carl-Otto

2017-01-01

and relative water content of all cultivars significantly decreased under drought and combined stress as compared to control. The net photosynthesis and starch content were significantly lower under drought and combined stress than control in the three cultivars. Stomata and pore length of the three cultivars......BACKGROUND: Abiotic stresses due to environmental factors could adversely affect the growth and development of crops. Among the abiotic stresses, drought and heat stress are two critical threats to crop growth and sustainable agriculture worldwide. Considering global climate change, incidence...... of combined drought and heat stress is likely to increase. The aim of this study was to shed light on plant growth performance and leaf physiology of three tomatoes cultivars ('Arvento', 'LA1994' and 'LA2093') under control, drought, heat and combined stress. RESULTS: Shoot fresh and dry weight, leaf area...

Questioning ‘drought displacement’: environment, politics and migration in Somalia

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Anna Lindley

2014-02-01

Full Text Available The role of the recent drought in producing migration cannot be understood in isolation from human practices and past and concurrent political processes. The environmental dimensions of recent displacement prompt a series of policy challenges in relation to prevention, response and rights protection.

Growth and physiological responses to drought and elevated ultraviolet-B in two contrasting populations of Hippophae rhamnoides

Energy Technology Data Exchange (ETDEWEB)

Yongqing Yang; Yinan Yao; Gang Xu [Chinese Academy of Sciences, Chengdu Inst. of Biology, Chengdu (China); Chunyang Li [Graduate School of the Chinese Academy of Sciences, Beijing (China)

2005-08-01

In the southeast of the Qinghai-Tibetan Plateau of China, sea buckthorn (Hippophae rhamnoides L.), which is a thorny nitrogen-fixing deciduously perennial shrub, has been widely used in forest restoration as the pioneer species. In our study, two contrasting populations from the low and high altitudinal regions were employed to investigate the effects of drought, ultraviolet-B (UV-B) and their combination on sea buckthorn. The experimental design included two watering regimes (well watered and drought stressed) and two levels of UV-B (with and without UV-B supplementation). Drought significantly decreased total biomass, total leaf area and specific leaf area (SLA), and increased root/shoot ratio, fine root/coarse root ratio and abscisic acid content (ABA) in both populations. However, the high altitudinal population was more responsive to drought than the low altitudinal population. On the other hand, elevated UV-B induced increase in anthocyanins in both populations, whereas he accumulation of UV-absorbing compounds occurred only in the low altitudinal population. The drought-induced enhancement of ABA in the high altitudinal population was significantly suppressed in the combination of drought and elevated UV-B. Moreover, significant drought x UV-B interaction was detected on total biomass in both populations, total leaf area and fine root/coarse root in the low altitudinal population, and SLA in the high altitudinal population. These results demonstrated that there were different adaptive responses between two contrasting populations, the high altitudinal population exhibited higher tolerance to drought and UV-B than the low altitudinal population. (au)

Why Different Drought Indexes Show Distinct Future Drought Risk Outcomes in the U.S. Great Plains?

Science.gov (United States)

Feng, S.; Hayes, M. J.; Trnka, M.

2015-12-01

Vigorous discussions and disagreements about the future changes in drought intensity in the US Great Plains have been taking place recently within the literature. These discussions have involved widely varying estimates based on drought indices and model-based projections of the future. To investigate and understand the causes for such a disparity between these previous estimates, we analyzed 10 commonly-used drought indexes using the output from 26 state-of-the-art climate models. These drought indices were computed using potential evapotranspiration estimated by the physically-based Penman-Monteith method (PE_pm) and the empirically-based Thornthwaite method (PE_th). The results showed that the short-term drought indicators are similar to modeled surface soil moisture and show a small but consistent drying trend in the future. The long-term drought indicators and the total column soil moisture, however, are consistent in projecting more intense future drought. When normalized, the drought indices with PE_th all show unprecedented and possibly unrealistic future drying, while the drought indices with PE_pm show comparable dryness with the modeled soil moisture. Additionally, the drought indices with PE_pm are closely related to soil moisture during both the 20th and 21st Centuries. Overall, the drought indices with PE_pm, as well as the modeled total column soil moisture, suggest a widespread and very significant drying of the Great Plains region toward the end of the Century. Our results suggested that the sharp contracts about future drought risk in the Great Plains discussed in previous studies are caused by 1) comparing the projected changes in short-term droughts with that of the long-term droughts, and/or 2) computing the atmospheric evaporative demand using the empirically-based method (e.g., PE_th). Our analysis may be applied for drought projections in other regions across the globe.

Protective Antioxidant Enzyme Activities are Affected by Drought in Quinoa (Chenopodium Quinoa Willd)

DEFF Research Database (Denmark)

Fghire, Rachid; Ali, Oudou Issa; Anaya, Fatima

2013-01-01

Changes in water availability are responsible for a variety of biochemical stress responses in plant organisms. Stress induced by this factor may be associated with enhanced reactive oxygen species (ROS) generations, which cause oxidative damage. In the present study we investigated the activities...... increased in all treatments. These results suggest that antioxidant enzymes play important roles in reducing oxidative stress in quinoa plant exposed to drought stress....... of antioxidant enzymes superoxide dismutase (SOD), polyphenoloxydase (PPO), peroxidase (POD) and catalase (CAT), measured at flowering in quinoa, subjected to varying levels of drought stress. Drought levels were 100, 50 and 33% of evapotranspiration (ETc), and rainfed. Compared to full water supply (100%ETc...

Germination Characteristics of Marshmallow (Althea officinalis L. as Influenced by Drought and Salinity Stress

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R Yazdani Biuki

2012-07-01

Full Text Available Drought and salinity are two important environmental stresses limiting the crop production. In order to study the influence of drought and salinity stresses on germination characteristics of Marshmallow plant seeds, two separate experiments were conducted based on completely randomized design with four replications in controlled conditions. Drought stress levels were 0, -2, -4, -6 and -8 bar in the first experiment and salinity stress levels were 0, -2, -4, -6, -8 and -10 bar in the second experiment which were accomplished using PEG 6000 and sodium chloride, respectively. The results indicated a decrease in germination rate and percentage, as well as in lengths and fresh and dry weights of both plumules and radicles, as the osmotic potential was reduced in both experiments. Marshmallow seeds showed an overall higher tolerance against salinity stress compared to drought stress, with germination occurring at as low osmotic potentials as -10 bars in salinity treatments, while only until -8 bar drought stress. In osmotic potentials of -2 and -4 bar the decrease in germination percentage was more sever in the salinity stress compared to drought stress; whereas in higher levels of stress (-6 and -8 bar drought stress brought about a higher decrease in germination percentage than did the salinity stress; illustrated by the percentage of germination decrease at -6 bar, i.e. 63% for drought and 80% for salinity treatments. At the treatments of higher potential (-2, -4 and -6 bar the decrease in radicle length was greater in response to salinity than to drought stress, but the length of plumule was more influenced by drought stress and also showed the highest sensitivity to drought, among all measured characteristics.

Comparative Analysis of Drought Indices for Drought Zone Scheme of Northern Khorasan Province of Iran

OpenAIRE

Ehsan EYSHI REZAEI; Azade MOHAMMADIAN; Mansoreh KOOHI; Mohammad BANNAYAN

2011-01-01

Drought is one of the natural disasters which deeply influenced agricultural production. Drought monitoring programs could help to forecast and mitigate the impacts of drought. In this study occurrence, severity, and duration of drought were evaluated by monthly rainfall data (1986-2005) that were recorded at all meteorological stations in north Khorasan province of Iran. Drought indices include Standard Rainfall Index (SPI), Decades Index (DI) and Percent of Normal (PNI) calculated and compa...

The innovation inducement impact of environmental regulations on maritime transport

DEFF Research Database (Denmark)

Makkonen, Teemu; Repka, Sari

2016-01-01

, contrasting views, arguing that environmental regulations will, in fact, enhance firms’ competitiveness by inducing innovation, have also been voiced. Here this issue is examined through a literature review on the innovation inducement impact of environmental regulations (i.e. the Porter Hypothesis......), in general, and the economic impacts of environmental regulations (here Annex VI of the MARPOL Convention) as it applies to shipping in Northern Europe, in particular. According to the review, the literature is still inconclusive and lacks a clear consensus on the economic and innovation inducement impacts......Maritime transport is facing wide-ranking challenges due to stricter environmental regulations. It has been positioned that these stricter environmental regulations will significantly hamper the competitiveness of the shipping industry and other export/import oriented industries. However...

Subtle shifts in microbial communities occur alongside the release of carbon induced by drought and rewetting in contrasting peatland ecosystems.

Science.gov (United States)

Potter, Caitlin; Freeman, Chris; Golyshin, Peter N; Ackermann, Gail; Fenner, Nathalie; McDonald, James E; Ehbair, Abdassalam; Jones, Timothy G; Murphy, Loretta M; Creer, Simon

2017-09-12

Peat represents a globally significant pool of sequestered carbon. However, peatland carbon stocks are highly threatened by anthropogenic climate change, including drought, which leads to a large release of carbon dioxide. Although the enzymatic mechanisms underlying drought-driven carbon release are well documented, the effect of drought on peatland microbial communities has been little studied. Here, we carried out a replicated and controlled drought manipulation using intact peat 'mesocosm cores' taken from bog and fen habitats, and used a combination of community fingerprinting and sequencing of marker genes to identify community changes associated with drought. Community composition varied with habitat and depth. Moreover, community differences between mesocosm cores were stronger than the effect of the drought treatment, emphasising the importance of replication in microbial marker gene studies. While the effect of drought on the overall composition of prokaryotic and eukaryotic communities was weak, a subset of the microbial community did change in relative abundance, especially in the fen habitat at 5 cm depth. 'Drought-responsive' OTUs were disproportionately drawn from the phyla Bacteroidetes and Proteobacteria. Collectively, the data provide insights into the microbial community changes occurring alongside drought-driven carbon release from peatlands, and suggest a number of novel avenues for future research.

Suitability Assessment of Satellite-Derived Drought Indices for Mongolian Grassland

Directory of Open Access Journals (Sweden)

Sheng Chang

2017-06-01

Full Text Available In Mongolia, drought is a major natural disaster that can influence and devastate large regions, reduce livestock production, cause economic damage, and accelerate desertification in association with destructive human activities. The objective of this article is to determine the optimal satellite-derived drought indices for accurate and real-time expression of grassland drought in Mongolia. Firstly, an adaptability analysis was performed by comparing nine remote sensing-derived drought indices with reference indicators obtained from field observations using several methods (correlation, consistency percentage (CP, and time-space analysis. The reference information included environmental data, vegetation growth status, and region drought-affected (RDA information at diverse scales (pixel, county, and region for three types of land cover (forest steppe, steppe, and desert steppe. Second, a meteorological index (PED, a normalized biomass (NorBio reference indicator, and the RDA-based drought CP method were adopted for describing Mongolian drought. Our results show that in forest steppe regions the normalized difference water index (NDWI is most sensitive to NorBio (maximum correlation coefficient (MAX_R: up to 0.92 and RDA (maximum CP is 87%, and is most consistent with RDA spatial distribution. The vegetation health index (VHI and temperature condition index (TCI are most correlated with the PED index (MAX_R: 0.75 and soil moisture (MAX_R: 0.58, respectively. In steppe regions, the NDWI is most closely related to soil moisture (MAX_R: 0.69 and the VHI is most related to the PED (MAX_R: 0.76, NorBio (MCC: 0.95, and RDA data (maximum CP is 89%, exhibiting the most consistency with RDA spatial distribution. In desert steppe areas, the vegetation condition index (VCI correlates best with NorBio (MAX_R: 0.92, soil moisture (MAX_R: 0.61, and RDA spatial distribution, while TCI correlates best with the PED (MAX_R: 0.75 and the RDA data (maximum CP is 79

Climate Change Decouples Drought from Early Wine Grape Harvests in France

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Cook, Benjamin I.; Wolkovich, Elizabeth M.

2016-01-01

Across the world, wine grape phenology has advanced in recent decades, in step with climate-change-induced trends in temperature - the main driver of fruit maturation - and drought. Fully understanding how climate change contributes to changes in harvest dates, however, requires analysing wine grape phenology and its relationship to climate over a longer-term context, including data predating anthropogenic interference in the climate system. Here, we investigate the climatic controls of wine grape harvest dates from 1600-2007 in France and Switzerland using historical harvest and climate data. Early harvests occur with warmer temperatures (minus 6 days per degree Centigrade) and are delayed by wet conditions (plus 0.07 days per millimeter; plus 1.68 days per PDSI (Palmer drought severity index)) during spring and summer. In recent decades (1981-2007), however, the relationship between harvest timing and drought has broken down. Historically, high summer temperatures in Western Europe, which would hasten fruit maturation, required drought conditions to generate extreme heat. The relationship between drought and temperature in this region, however, has weakened in recent decades and enhanced warming from anthropogenic greenhouse gases can generate the high temperatures needed for early harvests without drought. Our results suggest that climate change has fundamentally altered the climatic drivers of early wine grape harvests in France, with possible ramifications for viticulture management and wine quality.

Landscape-scale variation in canopy water content of giant sequoias during drought

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Paz-Kagan, Tarin; Vaughn, Nicolas R.; Martin, Roberta E.; Brodrick, Philip G.; Stephenson, Nathan L.; Das, Adrian; Nydick, Koren R.; Asner, Gregory P.

2018-01-01

Recent drought (2012–2016) caused unprecedented foliage dieback in giant sequoias (Sequoiadendron giganteum), a species endemic to the western slope of the southern Sierra Nevada in central California. As part of an effort to understand and map sequoia response to droughts, we studied the patterns of remotely sensed canopy water content (CWC), both within and among sequoia groves in two successive years during the drought period (2015 and 2016). Our aims were: (1) to quantify giant sequoia responses to severe drought stress at a landscape scale using CWC as an indicator of crown foliage status, and (2) to estimate the effect of environmental correlates that mediate CWC change within and among giant sequoia groves. We utilized airborne high fidelity imaging spectroscopy (HiFIS) and light detection and ranging (LiDAR) data from the Carnegie Airborne Observatory to assess giant sequoia foliage status during 2015 and 2016 of the 2012–2016 droughts. A series of statistical models were generated to classify giant sequoias and to map their location in Sequoia and Kings Canyon National Parks (SEKI) and vicinity. We explored the environmental correlates and the spatial patterns of CWC change at the landscape scale. The mapped CWC was highly variable throughout the landscape during the two observation years, and proved to be most closely related to geological substrates, topography, and site-specific water balance. While there was an overall net gain in sequoia CWC between 2015 and 2016, certain locations (lower elevations, steeper slopes, areas more distant from surface water sources, and areas with greater climate water deficit) showed CWC losses. In addition, we found greater CWC loss in shorter sequoias and those growing in areas with lower sequoia stem densities. Our results suggest that CWC change indicates sequoia response to droughts across landscapes. Long-term monitoring of giant sequoia CWC will likely be useful for modeling and predicting their population

Drought in Africa 2

Energy Technology Data Exchange (ETDEWEB)

Dalby, D; Harrison-Church, R J; Berzaz, F [eds.

1977-01-01

The second edition of Drought in Africa is reviewed. The book, which has been greatly expanded, looks at the Sahelian and Ethiopian droughts from a long-term perspective. Among the subjects included are: a description of the meteorological aspects of the drought; changes in animal and human populations; overpopulation of areas of nomadic pastoralism and of crop-producing areas; and mechanisms by which people survived. Cash crops, taxes, the market economy and over-centralized planning receive much of the blame for the effects of the drought.

[Physiological responses of mycorrhizal Pinus massoniana seedlings to drought stress and drought resistance evaluation].

Science.gov (United States)

Wang, Yi; Ding, Gui-jie

2013-03-01

A greenhouse pot experiment was conducted to study the effects of inoculating Pisolithus tinctorius, Cenococcum geophilum, Cantharellus cibarius, and Suillus luteus on the physiological characteristics of Pinus massoniana seedlings under the conditions of drought stress and re-watering, with the drought resistance of the mycorrhizal seedlings evaluated. Under drought stress, the MDA content and membrane' s relative permeability of P. massoniana seedlings increased, but these two indices in the inoculated (mycorrhizal) seedlings were significantly lower than these in the un-inoculated (control) seedlings. After re-watering, the MDA content and membrane's relative permeability of mycorrhizal seedlings had a rapid decrease, as compared with the control. In the first 21 days of drought stress, the production rate of superoxide radical of the seedlings increased, and the SOD, POD and NR activities of mycorrhizal seedlings increased significantly. With the extending of drought stress, the seedlings after re-watering had different recovery ability. Under the re-watering after 14 days drought stress, the SOD, POD and NR activities recovered. The drought resistance of the mycorrhizal seedlings was in the order of Suillus luteus 1 > Suillus luteus 7 > Cantharellus cibarius > Cenococcum geophilum > Pisolithus tinctorius. The SOD and MDA activities had a greater correlation with the mycorrhizal seedlings drought resistance, being able to be used as the indicators to evaluate the drought resistance of mycorrhizal seedlings.

Performing drought indices to identify the relationship between agricultural losses and drought events in Spain.

Science.gov (United States)

Peña Gallardo, Marina; Serrano, Sergio Martín Vicente; Portugués Santiago, Beguería; Burguera Miquel, Tomás

2017-04-01

Drought leads to crop failures reducing the productivity. For this reason, the need of appropriate tool for recognize dry periods and evaluate the impact of drought on crop production is important. In this study, we provide an assessment of the relationship between drought episodes and crop failures in Spain as one of the direct consequences of drought is the diminishing of crop yields. First, different drought indices [the Standardized Precipitation and Evapotranspiration Index (SPEI); the Standardized Precipitation Index (SPI); the self-calibrated Palmer Moisture Anomaly Index (Z-Index), the self-calibrated Crop Moisture Index (CMI) and the Standardized Palmer Drought Index (SPDI)] have been calculated at different time scales in order to identify the dry events occurred in Spain and determine the duration and intensity of each event. Second, the drought episodes have been correlated with crop production estimated and final crop production data provided by the Spanish Crop Insurance System for the available period from 1995 to 2014 at the municipal spatial scale, with the purpose of knowing if the characteristics of the drought episodes are reflected on the agricultural losses. The analysis has been carried out in particular for two types of crop, wheat and barley. The results indicate the existence of an agreement between the most important drought events in Spain and the response of the crop productions and the proportion of hectare insurance. Nevertheless, this agreement vary depending on the drought index applied. Authors found a higher competence of the drought indices calculated at different time scales (SPEI, SPI and SPDI) identifying the begging and end of the drought events and the correspondence with the crop failures.

Effects of Drought Stress and Ozone Exposure on Isoprene Emissions from Oak Seedlings in Texas

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Madronich, M. B.; Harte, A.; Schade, G. W.

2014-12-01

Isoprene is the dominant hydrocarbon emitted by plants to the atmosphere with an approximate global emission of 550 Tg C yr-1. Isoprene emission studies have elucidated plants' isoprene production capacity, and the controlling factors of instantaneous emissions. However, it is not yet well understood how long-term climatic factors such as drought and increasing ozone concentrations affect isoprene emission rates. Drought reduces photosynthetic activity and is thus expected to reduce isoprene emission rate, since isoprene production relies on photosynthates. On the other hand, ozone is also known to negatively affect photosynthesis rates, but can instead increase isoprene emissions. These apparent inconsistencies and a lack of experimental data make it difficult to accurately parameterize isoprene emission responses to changing environmental conditions. The objective of this work is to reduce some of these uncertainties, using oak seedlings as a study system. Our project focuses on isoprene emission responses of oak trees to typical summer drought and high ozone conditions in Texas. We report on experiments conducted using a laboratory whole-plant chamber and leaf-level data obtained from greenhouse-grown seedlings. The chamber experiment studied the effects of ozone and drought on isoprene emissions from >3 year old oak seedlings under controlled conditions of photosynthetically active radiation (PAR), temperature, soil-moisture and the chamber's air composition. Stress in plants was induced by manipulating potted soil-moisture and ozone concentration in the chamber. The greenhouse study focused on understanding the effects of drought under Texas climatic conditions. For this study we used two year old seedlings of water oak (Quercus nigra) and post oak (Quercus stellata). Temperature, humidity and light in the greenhouse followed local conditions. Leaf-level conductance, photosynthesis measurements and isoprene sampling were carried out under controlled leaf

A Global Perspective on Warmer Droughts as a Key Driver of Forest Disturbances and Tree Mortality (Invited)

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Allen, C. D.

2013-12-01

Recent global warming, in concert with episodic droughts, is causing elevated levels of both chronic and acute forest water stress across large regions. Such increases in water stress affect forest dynamics in multiple ways, including by amplifying the incidence and severity of many significant forest disturbances, particularly drought-induced tree mortality, wildfire, and outbreaks of damaging insects and diseases. Emerging global-scale patterns of drought-related forest die-off are presented, including a newly updated map overview of documented drought- and heat-induced tree mortality events from around the world, demonstrating the vulnerability of all major forest types to forest drought stress, even in typically wet environments. Comparative patterns of drought stress and associated forest disturbances are reviewed for several regions (southwestern Australia, Inner Asia, western North America, Mediterranean Basin), including interactions among climate and various disturbance processes. From the Southwest USA, research is presented that derives a tree-ring-based Forest Drought Stress Index (FDSI) for the most regionally-widespread conifer species (Pinus edulis, Pinus ponderosa, and Pseudotsuga menziesii), demonstrating recent escalation of FDSI to extreme levels relative to the past 1000 years, due to both drought and especially warming. This new work further highlights strong correlations between drought stress and amplified forest disturbances (fire, bark beetle outbreaks), and projects that by CE 2050 anticipated regional warming will cause mean FDSI values to reach historically unprecedented levels that may exceed thresholds for the survival of current tree species in large portions of their current range in the Southwest. Similar patterns of recent climate-amplified forest disturbance risk are apparent from a variety of relatively dry regions across this planet, and given climate projections for substantially warmer temperatures and greater drought stress

Metabolites and hormones are involved in the intraspecific variability of drought hardening in radiata pine.

Science.gov (United States)

De Diego, N; Saiz-Fernández, I; Rodríguez, J L; Pérez-Alfocea, P; Sampedro, M C; Barrio, R J; Lacuesta, M; Moncaleán, P

2015-09-01

Studies of metabolic and physiological bases of plant tolerance and hardening against drought are essential to improve genetic breeding programs, especially in productive species such as Pinus radiata. The exposure to different drought cycles is a highly effective tool that improves plant conditioning, but limited information is available about the mechanisms that modulate this process. To clarify this issue, six P. radiata breeds with well-known differences in drought tolerance were analyzed after two consecutive drought cycles. Survival rate, concentration of several metabolites such as free soluble amino acids and polyamines, and main plant hormones varied between them after drought hardening, while relative growth ratio and water potential at both predawn and dawn did not. Hardening induced a strong increase in total soluble amino acids in all breeds, accumulating mainly those implicated in the glutamate metabolism (GM), especially L-proline, in the most tolerant breeds. Other amino acids from GM such as γ-aminobutyric acid (GABA) and L-arginine (Arg) were also strongly increased. GABA pathway could improve the response against drought, whereas Arg acts as precursor for the synthesis of spermidine. This polyamine showed a positive relationship with the survival capacity, probably due to its role as antioxidant under stress conditions. Finally, drought hardening also induced changes in phytohormone content, showing each breed a different profile. Although all of them accumulated indole-3-acetic acid and jasmonic acid and reduced zeatin content in needles, significant differences were observed regarding abscisic acid, salicylic acid and mainly zeatin riboside. These results confirm that hardening is not only species-dependent but also an intraspecific processes controlled through metabolite changes. Copyright © 2015 Elsevier GmbH. All rights reserved.

Effects of drought stress on some agronomic and morphological ...

African Journals Online (AJOL)

ajl yemi

2011-10-19

Oct 19, 2011 ... has a vital usage. Being aware of ... world. Most countries in the world are facing the problem of drought. ... yield over a wide range of environmental condition is very important. ... grain yield and straw weight decreases with water stress ... Each plastic pot had been filled with cultivated soil, sand and manure ...

Physiological response to drought stress in Camptotheca acuminata seedlings from two provenances

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Yeqing eYing

2015-05-01

Full Text Available Drought stress is a key environmental factor limiting the growth and productivity of plants. The purpose of this study was to investigate the physiological responses of Camptotheca acuminata (C. acuminata to different drought stresses and compare the drought tolerance between the provenances Kunming (KM and Nanchang (NC, which are naturally distributed in different rainfall zones with annual rainfalls of 1000-1100 mm and 1600-1700 mm, respectively. We determined relative water content (RWC, chlorophyll content (Chl(a+b, net photosynthesis (Pn, gas exchange parameters, relative leakage conductivity (REC, malondialdehyde (MDA content and superoxide dismutase (SOD and peroxidase (POD activities of C. acuminata seedlings under both moderate (50% of maximum field capacity and severe drought stress (30% of maximum field capacity. As the degree of water stress increased, RWC, Chl(a+b content, Pn, stomatal conductance (Gs, transpiration rate (Tr and intercellular CO2 concentration (Ci values decreased, but water use efficiency (WUE, REC, MDA content and SOD and POD activities increased in provenances KM and NC. Under moderate and severe drought stress, provenance KM had higher RWC, Chl(a+b, Pn, WUE, SOD and POD and lower Gs, Tr, Ci and REC in leaves than provenance NC. The results indicated that provenance KM may maintain stronger drought tolerance via improvements in water-retention capacity, antioxidant enzyme activity and membrane integrity.

Adaptation to high temperature mitigates the impact of water deficit during combined heat and drought stress in C3 sunflower and C4 maize varieties with contrasting drought tolerance.

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Killi, Dilek; Bussotti, Filippo; Raschi, Antonio; Haworth, Matthew

2017-02-01

Heat and drought stress frequently occur together, however, their impact on plant growth and photosynthesis (P N ) is unclear. The frequency, duration and severity of heat and drought stress events are predicted to increase in the future, having severe implications for agricultural productivity and food security. To assess the impact on plant gas exchange, physiology and morphology we grew drought tolerant and sensitive varieties of C3 sunflower (Helianthus annuus) and C4 maize (Zea mays) under conditions of elevated temperature for 4 weeks prior to the imposition of water deficit. The negative impact of temperature on P N was most apparent in sunflower. The drought tolerant sunflower retained ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity under heat stress to a greater extent than its drought sensitive counterpart. Maize exhibited no varietal difference in response to increased temperature. In contrast to previous studies, where a sudden rise in temperature induced an increase in stomatal conductance (G s ), we observed no change or a reduction in G s with elevated temperature, which alongside lower leaf area mitigated the impact of drought at the higher temperature. The drought tolerant sunflower and maize varieties exhibited greater investment in root-systems, allowing greater uptake of the available soil water. Elevated temperatures associated with heat-waves will have profound negative impacts on crop growth in both sunflower and maize, but the deleterious effect on P N was less apparent in the drought tolerant sunflower and both maize varieties. As C4 plants generally exhibit water use efficiency (WUE) and resistance to heat stress, selection on the basis of tolerance to heat and drought stress would be more beneficial to the yields of C3 crops cultivated in drought prone semi-arid regions. © 2016 Scandinavian Plant Physiology Society.

Designing basin-customized combined drought indices via feature extraction

Science.gov (United States)

Zaniolo, Marta; Giuliani, Matteo; Castelletti, Andrea

2017-04-01

The socio-economic costs of drought are progressively increasing worldwide due to the undergoing alteration of hydro-meteorological regimes induced by climate change. Although drought management is largely studied in the literature, most of the traditional drought indexes fail in detecting critical events in highly regulated systems, which generally rely on ad-hoc formulations and cannot be generalized to different context. In this study, we contribute a novel framework for the design of a basin-customized drought index. This index represents a surrogate of the state of the basin and is computed by combining the available information about the water available in the system to reproduce a representative target variable for the drought condition of the basin (e.g., water deficit). To select the relevant variables and how to combine them, we use an advanced feature extraction algorithm called Wrapper for Quasi Equally Informative Subset Selection (W-QEISS). The W-QEISS algorithm relies on a multi-objective evolutionary algorithm to find Pareto-efficient subsets of variables by maximizing the wrapper accuracy, minimizing the number of selected variables (cardinality) and optimizing relevance and redundancy of the subset. The accuracy objective is evaluated trough the calibration of a pre-defined model (i.e., an extreme learning machine) of the water deficit for each candidate subset of variables, with the index selected from the resulting solutions identifying a suitable compromise between accuracy, cardinality, relevance, and redundancy. The proposed methodology is tested in the case study of Lake Como in northern Italy, a regulated lake mainly operated for irrigation supply to four downstream agricultural districts. In the absence of an institutional drought monitoring system, we constructed the combined index using all the hydrological variables from the existing monitoring system as well as the most common drought indicators at multiple time aggregations. The soil

The Drought Monitor.

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Svoboda, Mark; Lecomte, Doug; Hayes, Mike; Heim, Richard; Gleason, Karin; Angel, Jim; Rippey, Brad; Tinker, Rich; Palecki, Mike; Stooksbury, David; Miskus, David; Stephens, Scott

2002-08-01

information about drought and to receive regional and local input that is in turn incorporated into the product. This paper describes the Drought Monitor and the interactive process through which it is created.

Drought Characteristic Analysis Based on an Improved PDSI in the Wei River Basin of China

Directory of Open Access Journals (Sweden)

Lei Zou

2017-03-01

Full Text Available In this study, to improve the efficiency of the original Palmer Drought Severity Index (PDSI_original, we coupled the Soil and Water Assessment tool (SWAT and PDSI_original to construct a drought index called PDSI_SWAT. The constructed PDSI_SWAT is applied in the Wei River Basin (WRB of China during 1960–2012. The comparison of the PDSI_SWAT with four other commonly used drought indices reveals the effectiveness of the PDSI_SWAT in describing the drought propagation processes in WRB. The whole WRB exhibits a dry trend, with more significant trends in the northern, southeastern and western WRB than the remaining regions. Furthermore, the drought frequencies show that drought seems to occur more likely in the northern part than the southern part of WRB. The principle component analysis method based on the PDSI_SWAT reveals that the whole basin can be further divided into three distinct sub-regions with different drought variability, i.e., the northern, southeastern and western part. Additionally, these three sub-regions are also consistent with the spatial pattern of drought shown by the drought frequency. The wavelet transform analysis method indicates that the El Niño-Southern Oscillation (ENSO events have strong impacts on inducing droughts in the WRB. The results of this study could be beneficial for a scientific water resources management and drought assessment in the current study area and also provide a valuable reference for other areas with similar climatic characteristics.

Drought sensitivity changes over the last century at the North American savanna-forest boundary

Science.gov (United States)

Heilman, K.; McLachlan, J. S.

2017-12-01

Future environmental changes can affect the sensitivity of tree growth to climate. Theses changes are of particular concern at biome boundaries where tree distribution could shift as a result of changes in both drought and drought sensitivity. One such region is the North American savanna-forest boundary, where increased CO2 and droughts could alter savanna and forest ecosystem distributions in two contrasting ways: 1). More severe droughts may increase drought sensitivity, favoring open savanna ecosystems or, 2). Increases in water use efficiency resulting from higher atmospheric CO2 may decrease drought sensitivity, promoting forest expansion. This study sought to understand whether the past 100 years of climate and CO2 changes have impacted regional tree growth-climate sensitivity. To test for these climate sensitivity changes, we measured the sensitivity of Quercus spp. radial growth to Palmer Drought Severity Index (PDSI). Tree growth sensitivity to climate can vary according to many factors, including: stand structure, available moisture, and tree age. To control for these factors, we sampled tree growth-climate responses at sites in both open and closed forests, and at both low and high annual precipitation. Within each site, we compared growth responses to climate between trees established under high CO2 conditions after 1950 (high CO2 young), and tree established before 1950 under low CO2 levels (low CO2 young). At most sites, low CO2 young have a higher drought sensitivity than higher CO2 young. These changes in the sensitivity to drought are consistent with CO2 enhancement of water use efficiency. Furthermore, these differences in drought sensitivity are higher at sites with high temperature and low precipitation, suggesting that the alleviation of drought is more likely in hot and dry regions. Thus, if CO2 enhancement is indeed occurring in these systems, lower growth sensitivity to drought in hot and dry regions could favor increased forest growth. If

Effect of simultaneously induced environmental stimuli on electrical signalling and gas exchange in maize plants.

Science.gov (United States)

Vuralhan-Eckert, Jasmin; Lautner, Silke; Fromm, Jörg

2018-04-01

Electrical signalling in response to environmental stimuli is a well-known phenomenon in higher plants. For example, in maize, different stimuli, such as wounding or re-irrigation after drought, incite characteristic electrical signals which have quite particular effects on gas exchange. What is less well understood is how plants (specifically maize) respond when two different environmental stimuli are applied simultaneously. To explore this, a three-stage experiment was designed. In the first stage, drought conditions were simulated by decreasing the soil water content to 30-40 % of field capacity. In these conditions, and in contrast to well-watered plants, the maize exhibited only 60-70% of the original level of stomatal conductance and 50-60 % of the original photosynthesis rate. In the second stage of the experiment the plants were re-irrigated and heat stimulated separately. Re-irrigation led to specific electrical signals followed by a gradual increase of gas exchange. In contrast, after heat stimulation of a leaf an electrical signal was evoked that reduced the net CO 2 -uptake rate as well as stomatal conductance. In the third stage, to elucidate how plants process simultaneous re-irrigation and heat stimulation, the drought-stressed maize plants were re-watered and heat-stimulated at the same time. Results showed a two phase response. In the first phase there was a rapid decrease in both the CO 2 uptake rate and the stomatal conductance, while in the second phase each of these parameters increased gradually. Thus, the results strongly support the view that the responses from both stimuli were combined, indicating that maize plants can process simultaneously applied stimuli. Copyright © 2018 Elsevier GmbH. All rights reserved.

iTRAQ-based quantitative proteomic analysis reveals proteomic changes in leaves of cultivated tobacco (Nicotiana tabacum) in response to drought stress.

Science.gov (United States)

Xie, He; Yang, Da-Hai; Yao, Heng; Bai, Ge; Zhang, Yi-Han; Xiao, Bing-Guang

2016-01-15

Drought is one of the most severe forms of abiotic stresses that threaten the survival of plants, including crops. In turn, plants dramatically change their physiology to increase drought tolerance, including reconfiguration of proteomes. Here, we studied drought-induced proteomic changes in leaves of cultivated tobacco (Nicotiana tabacum), a solanaceous plant, using the isobaric tags for relative and absolute quantitation (iTRAQ)-based protein labeling technology. Of identified 5570 proteins totally, drought treatment increased and decreased abundance of 260 and 206 proteins, respectively, compared with control condition. Most of these differentially regulated proteins are involved in photosynthesis, metabolism, and stress and defense. Although abscisic acid (ABA) levels greatly increased in drought-treated tobacco leaves, abundance of detected ABA biosynthetic enzymes showed no obvious changes. In contrast, heat shock proteins (HSPs), thioredoxins, ascorbate-, glutathione-, and hydrogen peroxide (H2O2)-related proteins were up- or down-regulated in drought-treated tobacco leaves, suggesting that chaperones and redox signaling are important for tobacco tolerance to drought, and it is likely that redox-induced posttranslational modifications play an important role in modulating protein activity. This study not only provides a comprehensive dataset on overall protein changes in drought-treated tobacco leaves, but also shed light on the mechanism by which solanaceous plants adapt to drought stress. Copyright © 2015 Yunnan Academy of Tobacco Agricultural Sciences. Published by Elsevier Inc. All rights reserved.

Multi-basin, Multi-sector Drought Economic Impact Model in Python: Development and Applications

Science.gov (United States)

Gutenson, J. L.; Zhu, L.; Ernest, A. N. S.; Oubeidillah, A.; Bearden, B.; Johnson, T. G.

2015-12-01

Drought is one of the most economically disastrous natural hazards, one whose impacts are exacerbated by the lack of abrupt onset and offset that define tornados and hurricanes. In the United States, about 30 billion dollars losses is caused by drought in 2012, resulting in widespread economic impacts for societies, industries, agriculture, and recreation. And in California, the drought cost statewide economic losses about 2.2 billion, with a total loss of 17,100 seasonal and part-time jobs. Driven by a variety of factors including climate change, population growth, increased water demands, alteration to land cover, drought occurs widely all over the world. Drought economic consequence assessment tool are greatly needed to allow decision makers and stakeholders to anticipate and manage effectively. In this study, current drought economic impact modeling methods were reviewed. Most of these models only deal with the impact in the agricultural sector with a focus on a single basin; few of these models analyze long term impact. However, drought impacts are rarely restricted to basin boundaries, and cascading economic impacts are likely to be significant. A holistic approach to multi-basin, multi-sector drought economic impact assessment is needed.In this work, we developed a new model for drought economic impact assessment, Drought Economic Impact Model in Python (PyDEM). This model classified all business establishments into thirteen categories based on NAICS, and using a continuous dynamic social accounting matrix approach, coupled with calculation of the indirect consequences for the local and regional economies and the various resilience. In addition, Environmental Policy Integrated Climate model was combined for analyzing drought caused soil erosion together with agriculture production, and then the long term impacts of drought were achieved. A visible output of this model was presented in GIS. In this presentation, Choctawhatchee-Pea-Yellow River Basins, Alabama

Diverging Drought Resistance of Scots Pine Provenances Revealed by Infrared Thermography

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Hannes Seidel

2016-08-01

Full Text Available With recent climate changes, Scots pine (Pinus sylvestris L. forests have been affected by die-off events. Assisted migration of adapted provenances mitigates drought impacts and promotes forest regeneration. Although suitable provenances are difficult to identify by traditional ecophysiological techniques, which are time consuming and invasive, plant water status can be easily assessed by infrared thermography. Thus, we examined the stress responses of 2-year-old potted Scots pine seedlings from six provenances (Bulgaria, France, Germany, Italy, Poland, and Spain based on two thermal indices (crop water stress index and stomatal conductance index. Both indices were derived from infrared images during a six-week drought/control treatment in a greenhouse in the summer of 2013. The pines were monitored during the stress and subsequent recovery period. After controlling for fluctuating environmental conditions, soil moisture or treatment-specific water supply was the most important driver of drought stress. The stress magnitude and response to soil water deficit depended on provenance. Under moderate drought conditions, pines from western and eastern Mediterranean provenances (Bulgaria, France, and Spain expressed lower stress levels than those from both continental provenances (Germany and Poland. In pines from the Spanish and Bulgarian provenances, the stress level differences were significantly lower than in continental pines. Moreover, pines from continental provenances were less resilient (showed less recovery after the stress period than Mediterranean pines. Under extreme drought, all provenances were equally stressed with almost no significant differences in their thermal indices. Provenance-specific differences in drought resistance, which are associated with factors such as summer precipitation at the origin of Scots pine seedlings, may offer promising tracks of adaptation to future drought risks.

Salicylic acid and methyl jasmonate enhance drought tolerance in chamomile plants

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Nazarli Hossein

2014-04-01

Full Text Available Introduction: The dried flowers of chamomile contain many terpenoids and flavonoids contributing to its medicinal properties. Salicylic acid (SA and methyl jasmonate (MeJA have antioxidant properties and function as direct radical scavengers. Two Matricaria chamomilla cultivars (Bodgold and Hungary breed seeds were used in this study to investigate the effects of exogenous application of SA and MeJA on protection against drought stress as well as on changes of malone dialdehyde (MDA and electrolyte leakage index (ELI, and the fluctuation of proline and soluble sugars content in the leaves under drought stress. Methods: The experiment was conducted in a factorial design based on randomized complete blocks with three replicates. Chamomile plants were treated by two levels of drought stress as well as two different levels of MeJA (i.e., 0.0 and 100 μM and SA (i.e., 0.0 and 0.5 mM solutions. Results: There was a dramatic drought induced increase in the MDA content (128% and ELI (49% in the leaves. Deleterious effect of drought stress was more severe in untreated plants than in treated ones. Treatments with SA and MeJA significantly improved drought tolerance in chamomile plants. These treatments effectively maintained membrane integrity, thereby retarding electrolyte leakage and membrane lipid peroxidation (MDA. Treatments with SA and MeJA were also effective in enhancing the antioxidant concentrations of proline and soluble sugars. Conclusion: The production of these antioxidants could have been part of a defence system against drought damage, reducing MDA and ELI and maintaining membrane stability.

Early Differential Responses of Co-dominant Canopy Species to Sudden and Severe Drought in a Mediterranean-climate Type Forest

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Katinka X. Ruthrof

2015-06-01

Full Text Available Globally, drought and heat-induced forest disturbance is garnering increasing concern. Species from Mediterranean forests have resistance and resilience mechanisms to cope with drought and differences in these ecological strategies will profoundly influence vegetation composition in response to drought. Our aim was to contrast the early response of two co-occurring forest species, Eucalyptus marginata and Corymbia calophylla, in the Northern Jarrah Forest of southwestern Australia, following a sudden and severe drought event. Forest plots were monitored for health and response, three and 16 months following the drought. Eucalyptus marginata was more susceptible to partial and complete crown dieback compared to C. calophylla, three months after the drought. However, resprouting among trees exhibiting complete crown dieback was similar between species. Overall, E. marginata trees were more likely to die from the impacts of drought, assessed at 16 months. These short-term differential responses to drought may lead to compositional shifts with increases in frequency of drought events in the future.

Drought assessment in the Dongliao River basin: traditional approaches vs. generalized drought assessment index based on water resources systems

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Weng, B. S.; Yan, D. H.; Wang, H.; Liu, J. H.; Yang, Z. Y.; Qin, T. L.; Yin, J.

2015-08-01

Drought is firstly a resource issue, and with its development it evolves into a disaster issue. Drought events usually occur in a determinate but a random manner. Drought has become one of the major factors to affect sustainable socioeconomic development. In this paper, we propose the generalized drought assessment index (GDAI) based on water resources systems for assessing drought events. The GDAI considers water supply and water demand using a distributed hydrological model. We demonstrate the use of the proposed index in the Dongliao River basin in northeastern China. The results simulated by the GDAI are compared to observed drought disaster records in the Dongliao River basin. In addition, the temporal distribution of drought events and the spatial distribution of drought frequency from the GDAI are compared with the traditional approaches in general (i.e., standard precipitation index, Palmer drought severity index and rate of water deficit index). Then, generalized drought times, generalized drought duration, and generalized drought severity were calculated by theory of runs. Application of said runs at various drought levels (i.e., mild drought, moderate drought, severe drought, and extreme drought) during the period 1960-2010 shows that the centers of gravity of them all distribute in the middle reaches of Dongliao River basin, and change with time. The proposed methodology may help water managers in water-stressed regions to quantify the impact of drought, and consequently, to make decisions for coping with drought.

21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions.

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Aragão, Luiz E O C; Anderson, Liana O; Fonseca, Marisa G; Rosan, Thais M; Vedovato, Laura B; Wagner, Fabien H; Silva, Camila V J; Silva Junior, Celso H L; Arai, Egidio; Aguiar, Ana P; Barlow, Jos; Berenguer, Erika; Deeter, Merritt N; Domingues, Lucas G; Gatti, Luciana; Gloor, Manuel; Malhi, Yadvinder; Marengo, Jose A; Miller, John B; Phillips, Oliver L; Saatchi, Sassan

2018-02-13

Tropical carbon emissions are largely derived from direct forest clearing processes. Yet, emissions from drought-induced forest fires are, usually, not included in national-level carbon emission inventories. Here we examine Brazilian Amazon drought impacts on fire incidence and associated forest fire carbon emissions over the period 2003-2015. We show that despite a 76% decline in deforestation rates over the past 13 years, fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. The 2015 drought had the largest ever ratio of active fire counts to deforestation, with active fires occurring over an area of 799,293 km 2 . Gross emissions from forest fires (989 ± 504 Tg CO 2 year -1 ) alone are more than half as great as those from old-growth forest deforestation during drought years. We conclude that carbon emission inventories intended for accounting and developing policies need to take account of substantial forest fire emissions not associated to the deforestation process.

Local Perception of Drought Impacts in a Changing Climate: The Mega-Drought in Central Chile

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Paulina Aldunce

2017-11-01

Full Text Available Droughts are a recurrent and complex natural hazard whose frequency and magnitude are expected to increase with climate change. Despite the advances in responding and adapting to droughts (with the development of new policies, for example, droughts continue to cause serious impacts and suffering. Developing well-targeted public policies requires further research on adaptation. Specifically, understanding the public perception of drought can help to identify drivers of and barriers to adaptation and options. This research seeks to understand the public perception of drought in central Chile in order to inform adaptation-related policies and decision-making processes. This study focused on the Mega-drought, which was a protracted dry spell afflicting central Chile since 2010.

Coordinate changes in photosynthesis, sugar accumulation and antioxidative enzymes improve the performance of Jatropha curcas plants under drought stress

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Silva, Evandro N.; Ribeiro, Rafael V.; Ferreira-Silva, Sérgio L.; Vieira, Suyanne A.; Ponte, Luiz F.A.; Silveira, Joaquim A.G.

2012-01-01

The aim of this study was to assess the relationships between photosynthesis, sugars and photo-oxidative protection mechanisms in Jatropha curcas under drought stress. Leaf CO 2 assimilation rate (P N ) and instantaneous carboxylation efficiency decreased progressively as the water deficit increased. The sucrose and reducing sugar concentrations were negatively and highly correlated with photosynthesis indicating a modulation by negative feedback mechanism. The alternative electron sinks (ETR s '/P N ), relative excess of light energy (EXC) and non-photochemical quenching were strongly increased by drought, indicating effective mechanisms of energy excess dissipation. The photochemistry data indicate partial preservation of photosystem II integrity and function even under severe drought. EXC was positively correlated with superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities evidencing an effective role of these enzymes in the oxidative protection against excess of reactive oxygen species in chloroplasts. Leaf H 2 O 2 content and lipid peroxidation were inversely and highly correlated with catalase (CAT) activity indicating that drought-induced inhibition of this enzyme might have allowed oxidative damage. Our data suggest that drought triggers a coordinate down-regulation in photosynthesis through sucrose and reducing sugar accumulation and an energy excess dissipation at PSII level by non-photochemical mechanisms associate with enhancement in photorespiration, restricting photo-damages. In parallel, drought up-regulates SOD and APX activities avoiding accumulation of reactive oxygen species, while CAT activity is not able to avoid H 2 O 2 accumulation in drought-stressed J. curcas leaves. -- Highlights: ► Drought triggers a down-regulation in photosynthesis by sucrose and reducing sugar. ► Drought induces energy dissipation at PSII level and increase in photorespiration. ► Drought up-regulates SOD and APX activities avoiding accumulation of

Physiological Responses to Prolonged Drought Differ Among Three Oak (Quercus) Species

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Cooper, C. E.; Moore, G. W.; Vogel, J. G.; Muir, J. P.

2015-12-01

The physiological response of plants to water stress provides insights into which species may survive in exceptional drought conditions. This study conducted on a remnant post oak savanna site in College Station, Texas, examined how drought affected the physiology of three native oak species. In June 2014, after a period of equal watering, we subjected three year old Quercus shumardii (Shumard oak; SO), Q. virginiana (live oak; LO), and Q. macrocarpa (bur oak; BO) saplings to one of two watering treatments: 1) watered, receiving the equivalent of theaverage precipitation rate and 2) droughted, receiving a 100% reduction in precipitation. We measured predawn (ΨPD) and midday (ΨMD) leaf water potential; midday gas exchange (MGE) parameters including photosynthesis (Al), transpiration (T), stomatal conductance (gsw); and leaf soluble (SS) and non-soluble sugar (NSS) concentrations monthly between June and October 2014. Drought stress responses were evident after only one month of induced drought. Droughted saplings showed reduced ΨPD, ΨMD, and MGE (P ≤ 0.05) in comparison to watered saplings of the same species. LO saplings exhibited greater MGE (P ≤ 0.05) while maintaining similar LWP to their respective watered and droughted BO and SO counterparts. Droughted LO exhibited MGE rates similar to those of watered BO and SO (P ≤ 0.05), while watered LO adjusted its MGE rates to changes in water availability better than BO and LO during short-term drought. Compared to water saplings, droughted saplings had greater leaf SS (P = 0.08) and lower NSS concentrations (P = 0.10), possibly due to the conversion of NSS to SS and other simple compounds and reduced consumption of SS for growth by the droughted saplings. Although SO and BO exhibited similar photosynthesis rates, leaf total sugar (SS+NSS) concentration was greater in SO (P ≤ 0.05). By displaying the greatest average photosynthesis rate (P ≤ 0.05), LO should have accumulated the greatest amount of carbon

Adaptive transgenerational plasticity in an annual plant: grandparental and parental drought stress enhance performance of seedlings in dry soil.

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Herman, Jacob J; Sultan, Sonia E; Horgan-Kobelski, Tim; Riggs, Charlotte

2012-07-01

significantly greater survivorship in very dry soil than did seedlings with no history of drought. These findings show that plastic responses to naturalistic resource stresses experienced by grandparents and parents can "preadapt" offspring for functioning under the same stresses in ways that measurably influence realized fitness. Possible implications of these environmentally-induced, inherited adaptations are discussed with respect to ecological distribution, persistence under novel stresses, and evolution in natural populations.

Drought preparedness and drought mitigation in the developing world׳s drylands

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Mahmoud Solh

2014-06-01

Drought is a climatic event that cannot be prevented, but interventions and preparedness to drought can help to: (i be better prepared to cope with drought; (ii develop more resilient ecosystems (iii improve resilience to recover from drought; and (iv mitigate the impacts of droughts. Preparedness strategies to drought include: (a geographical shifts of agricultural systems; (b climate-proofing rainfall-based systems; (c making irrigated systems more efficient; (d expanding the intermediate rainfed–irrigated systems. The paper presents successful research results and case studies applying some innovative techniques where clear impact is demonstrated to cope with drought and contribute to food security in dry areas. The CGIAR Consortium Research Program (CRP on “Integrated and Sustainable Agricultural Production Systems for Improved Food Security and Livelihoods in Dry Areas” (in short, “Dryland Systems”, led by ICARDA, was launched in May 2013 with many partners and stakeholders from 40 countries. It addresses farming systems in dry areas, at a global level, involving 80 partner institutions. The Dryland Systems Program aims at coping with drought and water scarcity to enhance food security and reduce poverty in dry areas through an integrated agro-ecosystem approach. It will also deliver science-based solutions that can be adopted in regions that are not yet experiencing extreme shocks, but will be affected in the medium to long-term. The approach entails shifting the thinking away from the traditional focus on a small number of research components to take an integrated approach aiming to address agro-ecosystems challenges. Such an approach involves crops, livestock, rangeland, trees, soils, water and policies. It is one of the first global research for development efforts that brings “systems thinking” to farming innovations leading to improved livelihoods in the developing world. The new technique uses modern innovation platforms to involve all

Monthly hydrometeorological ensemble prediction of streamflow droughts and corresponding drought indices

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F. Fundel

2013-01-01

Full Text Available Streamflow droughts, characterized by low runoff as consequence of a drought event, affect numerous aspects of life. Economic sectors that are impacted by low streamflow are, e.g., power production, agriculture, tourism, water quality management and shipping. Those sectors could potentially benefit from forecasts of streamflow drought events, even of short events on the monthly time scales or below. Numerical hydrometeorological models have increasingly been used to forecast low streamflow and have become the focus of recent research. Here, we consider daily ensemble runoff forecasts for the river Thur, which has its source in the Swiss Alps. We focus on the evaluation of low streamflow and of the derived indices as duration, severity and magnitude, characterizing streamflow droughts up to a lead time of one month.

The ECMWF VarEPS 5-member ensemble reforecast, which covers 18 yr, is used as forcing for the hydrological model PREVAH. A thorough verification reveals that, compared to probabilistic peak-flow forecasts, which show skill up to a lead time of two weeks, forecasts of streamflow droughts are skilful over the entire forecast range of one month. For forecasts at the lower end of the runoff regime, the quality of the initial state seems to be crucial to achieve a good forecast quality in the longer range. It is shown that the states used in this study to initialize forecasts satisfy this requirement. The produced forecasts of streamflow drought indices, derived from the ensemble forecasts, could be beneficially included in a decision-making process. This is valid for probabilistic forecasts of streamflow drought events falling below a daily varying threshold, based on a quantile derived from a runoff climatology. Although the forecasts have a tendency to overpredict streamflow droughts, it is shown that the relative economic value of the ensemble forecasts reaches up to 60%, in case a forecast user is able to take preventive

Monthly hydrometeorological ensemble prediction of streamflow droughts and corresponding drought indices

Science.gov (United States)

Fundel, F.; Jörg-Hess, S.; Zappa, M.

2013-01-01

Streamflow droughts, characterized by low runoff as consequence of a drought event, affect numerous aspects of life. Economic sectors that are impacted by low streamflow are, e.g., power production, agriculture, tourism, water quality management and shipping. Those sectors could potentially benefit from forecasts of streamflow drought events, even of short events on the monthly time scales or below. Numerical hydrometeorological models have increasingly been used to forecast low streamflow and have become the focus of recent research. Here, we consider daily ensemble runoff forecasts for the river Thur, which has its source in the Swiss Alps. We focus on the evaluation of low streamflow and of the derived indices as duration, severity and magnitude, characterizing streamflow droughts up to a lead time of one month. The ECMWF VarEPS 5-member ensemble reforecast, which covers 18 yr, is used as forcing for the hydrological model PREVAH. A thorough verification reveals that, compared to probabilistic peak-flow forecasts, which show skill up to a lead time of two weeks, forecasts of streamflow droughts are skilful over the entire forecast range of one month. For forecasts at the lower end of the runoff regime, the quality of the initial state seems to be crucial to achieve a good forecast quality in the longer range. It is shown that the states used in this study to initialize forecasts satisfy this requirement. The produced forecasts of streamflow drought indices, derived from the ensemble forecasts, could be beneficially included in a decision-making process. This is valid for probabilistic forecasts of streamflow drought events falling below a daily varying threshold, based on a quantile derived from a runoff climatology. Although the forecasts have a tendency to overpredict streamflow droughts, it is shown that the relative economic value of the ensemble forecasts reaches up to 60%, in case a forecast user is able to take preventive action based on the forecast.

Managing the Health Impacts of Drought in Brazil

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Sena, Aderita; Barcellos, Christovam; Freitas, Carlos; Corvalan, Carlos

2014-01-01

Drought is often a hidden risk with the potential to become a silent public health disaster. It is difficult to define precisely when it starts or when it is over, and although it is a climatological event, its impacts depend on other human activities, and are intensified by social vulnerability. In Brazil, half of all natural disaster events are drought related, and they cause half of the impacts in number of affected persons. One large affected area is the semiarid region of Brazil’s Northeast, which has historically been affected by drought. Many health and well-being indicators in this region are worse than the rest of the country, based on an analysis of 5565 municipalities using available census data for 1991, 2000 and 2010, which allowed separating the 1133 municipalities affected by drought in order to compare them with the rest of the country. Although great progress has been made in reducing social and economic vulnerability, climate change and the expected changes in the semiarid region in the next few decades call for a review of current programs, particularly in public health, and the planning of new interventions with local communities. This study reviews the literature, analyzes available data and identifies possible actions and actors. The aim is to ensure there will be sufficient and sustainable local adaptive capacity and resilience, for a population already living within the limits of environmental vulnerability. PMID:25325358

Managing the Health Impacts of Drought in Brazil

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Aderita Sena

2014-10-01

Full Text Available Drought is often a hidden risk with the potential to become a silent public health disaster. It is difficult to define precisely when it starts or when it is over, and although it is a climatological event, its impacts depend on other human activities, and are intensified by social vulnerability. In Brazil, half of all natural disaster events are drought related, and they cause half of the impacts in number of affected persons. One large affected area is the semiarid region of Brazil’s Northeast, which has historically been affected by drought. Many health and well-being indicators in this region are worse than the rest of the country, based on an analysis of 5565 municipalities using available census data for 1991, 2000 and 2010, which allowed separating the 1133 municipalities affected by drought in order to compare them with the rest of the country. Although great progress has been made in reducing social and economic vulnerability, climate change and the expected changes in the semiarid region in the next few decades call for a review of current programs, particularly in public health, and the planning of new interventions with local communities. This study reviews the literature, analyzes available data and identifies possible actions and actors. The aim is to ensure there will be sufficient and sustainable local adaptive capacity and resilience, for a population already living within the limits of environmental vulnerability.

Isolation of a cotton NADP(H oxidase homologue induced by drought stress

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NEPOMUCENO ALEXANDRE LIMA

2000-01-01

Full Text Available The aim of this study was to identify and isolate genes that are differentially expressed in four selected cotton (Gossypium hirsutum L. genotypes contrasting according to their tolerance to water deficit. The genotypes studied were Siokra L-23, Stoneville 506, CS 50 and T-1521. Physiological, morphological and developmental changes that confer drought tolerance in plants must have a molecular genetic basis. To identify and isolate the genes, the mRNA Differential Display (DD technique was used. Messenger RNAs differentially expressed during water deficit were identified, isolated, cloned and sequenced. The cloned transcript A12B15-5, a NADP(H oxidase homologue, was up regulated only during the water deficit stress and only in Siokra L-23, a drought tolerant genotype. Ribonuclease protection assay confirmed that transcription.

Operationalising resilience to drought: Multi-layered safety for flooding applied to droughts

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Rijke, Jeroen; Smith, Jennifer Vessels; Gersonius, Berry; van Herk, Sebastiaan; Pathirana, Assela; Ashley, Richard; Wong, Tony; Zevenbergen, Chris

2014-11-01

This paper sets out a way of thinking about how to prepare for and respond to droughts in a holistic way using a framework developed for managing floods. It shows how the multi-layered safety (MLS) approach for flood resilience can be utilised in the context of drought in a way that three layers of intervention can be distinguished for operationalising drought resilience: (1) protection against water shortage through augmentation and diversification of water supplies; (2) prevention of damage in case of water shortage through increased efficiency of water use and timely asset maintenance; (3) preparedness for future water shortages through mechanisms to reduce the use of water and adopt innovative water technologies. Application of MLS to the cities of Adelaide, Melbourne and Sydney shows that recent water reforms in these cities were primarily focused on protection measures that aim to reduce the hazard source or exposure to insufficient water supplies. Prevention and preparedness measures could be considered in defining interventions that aim to further increase the drought resilience of these cities. Although further research is needed, the application suggests that MLS can be applied to the context of drought risk management. The MLS framework can be used to classify the suite of plans deployed by a city to manage future drought risks and can be considered a planning tool to identify opportunities for increasing the level of redundancy and hence resilience of the drought risk management system.

Drought tolerance and proteomics studies of transgenic wheat containing the maize C4 phosphoenolpyruvate carboxylase (PEPC) gene.

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Qin, Na; Xu, Weigang; Hu, Lin; Li, Yan; Wang, Huiwei; Qi, Xueli; Fang, Yuhui; Hua, Xia

2016-11-01

Enhancing drought tolerance of crops has been a great challenge in crop improvement. Here, we report the maize phosphoenolpyruvate carboxylase (PEPC) gene was able to confer drought tolerance and increase grain yield in transgenic wheat (Triticum aestivum L.) plants. The improved of drought tolerance was associated with higher levels of proline, soluble sugar, soluble protein, and higher water use efficiency. The transgenic wheat plants had also a more extensive root system as well as increased photosynthetic capacity during stress treatments. The increased grain yield of the transgenic wheat was contributed by improved biomass, larger spike and grain numbers, and heavier 1000-grain weight under drought-stress conditions. Under non-stressed conditions, there were no significant increases in these of the measured traits except for photosynthetic rate when compared with parental wheat. Proteomic research showed that the expression levels of some proteins, including chlorophyll A-B binding protein and pyruvate, phosphate dikinase, which are related to photosynthesis, PAP fibrillin, which is involved in cytoskeleton synthesis, S-adenosylmethionine synthetase, which catalyzes methionine synthesis, were induced in the transgenic wheat under drought stress. Additionally, the expression of glutamine synthetase, which is involved in ammonia assimilation, was induced by drought stress in the wheat. Our study shows that PEPC can improve both stress tolerance and grain yield in wheat, demonstrating the efficacy of PEPC in crop improvement.

Drought's legacy: multiyear hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk.