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1

Diminished mercury emission from waters with duckweed cover  

Science.gov (United States)

Duckweeds (Lemnaceae) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and limits gas exchange at the water-air interface by decreasing the area of open water surface. Experiments were conducted to determine whether duckweed decreases mercury emission by limiting gas diffusion across the water-air interface and attenuating light, or, conversely, enhances emission via transpiration of mercury vapor. Microcosm flux chamber experiments indicate that duckweed decreases mercury emission from the water surface compared to open water controls. Fluxes under duckweed were 17-67% lower than in controls, with lower fluxes occurring at higher percent cover. The decrease in mercury emission suggests that duckweed may limit emission through one of several mechanisms, including limited gas transport across the air-water interface, decreased photoreactions due to light attenuation, and plant-mercury interactions. The results of this experiment were applied to a model lake system to illustrate the magnitude of potential effects on mercury cycling. The mercury retained in the lake as a result of hindered emission may increase bioaccumulation potential in lakes with duckweed cover.

Wollenberg, Jennifer L.; Peters, Stephen C.

2009-06-01

2

Diminished Mercury Emission From Water Surfaces by Duckweed (Lemna minor)  

Science.gov (United States)

Aquatic plants of the family Lemnaceae (generally referred to as duckweeds) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and decreases the amount of exposed water surface. These two factors would be expected to reduce mercury emission by limiting a) direct photoreduction of Hg(II), b) indirect reduction via coupled DOC photooxidation-Hg(II) reduction, and c) gas diffusion across the water-air interface. Conversely, previous studies have demonstrated transpiration of Hg(0) by plants, so it is therefore possible that the floating vegetative mat would enhance emission via transpiration of mercury vapor. The purpose of this experiment was to determine whether duckweed limits mercury flux to the atmosphere by shading and the formation of a physical barrier to diffusion, or whether it enhances emission from aquatic systems via transpiration of Hg(0). Deionized water was amended with mercury to achieve a final concentration of approximately 35 ng/L and allowed to equilibrate prior to the experiment. Experiments were conducted in rectangular polystyrene flux chambers with measured UV-B transmittance greater than 60% (spectral cutoff approximately 290 nm). Light was able to penetrate the flux chamber from the sides as well as the top throughout the experiment, limiting the effect of shading by duckweed on the water surface. Flux chambers contained 8L of water with varying percent duckweed cover, and perforated plastic sheeting was used as an abiotic control. Exposures were conducted outside on days with little to no cloud cover. Real time mercury flux was measured using atomic absorption (Mercury Instruments UT-3000). Total solar and ultraviolet radiation, as well as a suite of meteorological parameters, were also measured. Results indicate that duckweed diminishes mercury emission from the water surface as compared to open water controls. Decreases in emission rate varied linearly with percent duckweed cover, with lower fluxes occurring at higher percent cover. Mercury flux in the duckweed treatments as compared to open water treatments decreased from 17% in the lowest percent cover treatment to 67% in the highest percent cover treatment. The observed decrease in mercury emission suggests that duckweed limits emission via the formation of a physical barrier to diffusion.

Wollenberg, J. L.; Peters, S. C.

2007-12-01

3

Catalytic upgrading of duckweed biocrude in subcritical water.  

Science.gov (United States)

Herein, a duckweed biocrude produced from the hydrothermal liquefaction of Lemna minor was treated in subcritical water with added H2. Effects of several different commercially available materials such as Ru/C, Pd/C, Pt/C, Pt/?-Al2O3, Pt/C-sulfide, Rh/?-Al2O3, activated carbon, MoS2, Mo2C, Co-Mo/?-Al2O3, and zeolite on the yields of product fractions and the deoxygenation, denitrogenation, and desulfurization of biocrude at 350°C were examined, respectively. All the materials showed catalytic activity for deoxygenation and desulfurization of the biocrude and only Ru/C showed activity for denitrogenation. Of those catalysts examined, Pt/C showed the best performance for deoxygenation. Among all the upgraded oils, the oil produced with Ru/C shows the lowest sulfur, the highest hydrocarbon content (25.6%), the highest energy recovery (85.5%), and the highest higher heating value (42.6MJ/kg). The gaseous products were mainly unreacted H2, CH4, CO2, and C2H6. PMID:24880811

Zhang, Caicai; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

2014-08-01

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Potential of duckweed in the conversion of wastewater nutrients to valuable biomass: A pilot-scale comparison with water hyacinth.  

Science.gov (United States)

The application potential of duckweed (Lemna japonica 0234) and water hyacinth (Eichhornia crassipes) were compared in two pilot-scale wastewater treatment systems for more than one year. The results indicated duckweed had the same total nitrogen (TN) recovery rate as water hyacinth (0.4g/m(2)/d) and a slightly lower total phosphorus (TP) recovery rate (approximately 0.1g/m(2)/d) even though its biomass production was half that of water hyacinth. The higher content of crude protein (33.34%), amino acids (25.80%), starch (40.19%), phosphorus (1.24%), flavonoids (2.91%) and lower fiber content provided duckweed with more advantages in resource utilization. Additionally, microbial community discovered by 454 pyrosequencing indicated that less nitrifying bacteria and more nitrogen-fixing bacteria in rhizosphere of duckweed provided it with higher nitrogen recovery efficiency (60%) than water hyacinth (47%). Under the presented condition, duckweed has more application advantages than water hyacinth because it more effectively converted the wastewater nutrients into valuable biomass. PMID:24787320

Zhao, Yonggui; Fang, Yang; Jin, Yanling; Huang, Jun; Bao, Shu; Fu, Tian; He, Zhiming; Wang, Feng; Zhao, Hai

2014-07-01

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Feasibility of Producing Selenium-Enriched Water Lettuce (Pistia stratiotes L.)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The feasibility of producing selenium-enriched water lettuce (Pistia stratiotes L.) was studied by cultivating water lettuce in Hoagland's solution containing 0, 20, 40, 60 and 80 mg Se from sodium selenite/L. There were 4 replicates in each Se concentration. Each replicate consisted of 30 plants of water lettuce. Three plants of water lettuce in each replicate were sampled on day 0, 1, 2, 3 and 4 of the experiment. The samples were washed with deionized water, separated for lea...

Anut Chantiratikul; Panida Atiwetin; Piyanete Chantiratikul

2008-01-01

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Plant growth-promoting bacterium Acinetobacter calcoaceticus P23 increases the chlorophyll content of the monocot Lemna minor (duckweed) and the dicot Lactuca sativa (lettuce).  

Science.gov (United States)

Acinetobacter calcoaceticus P23 is a plant growth-promoting bacterium that was isolated from the surface of duckweed (Lemna aoukikusa). The bacterium was observed to colonize on the plant surfaces and increase the chlorophyll content of not only the monocotyledon Lemna minor but also the dicotyledon Lactuca sativa in a hydroponic culture. This effect on the Lactuca sativa was significant in nutrient-poor (×1/100 dilution of H2 medium) and not nutrient-rich (×1 or ×1/10 dilutions of H2 medium) conditions. Strain P23 has the potential to play a part in the future development of fertilizers and energy-saving hydroponic agricultural technologies. PMID:24468072

Suzuki, Wakako; Sugawara, Masayuki; Miwa, Kyoko; Morikawa, Masaaki

2014-07-01

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Prevalence and transmission of antimicrobial resistance among Aeromonas populations from a duckweed aquaculture based hospital sewage water recycling system in Bangladesh.  

Science.gov (United States)

In order to investigate the influence of a duckweed aquaculture based hospital sewage water recycling plant on the prevalence and dissemination of antibiotic resistance, we made use of an existing collection of 1,315 Aeromonas isolates that were previously typed by the biochemical fingerprinting PhP-AE system. In these treatment plant, hospital raw sewage water is first collected in a settlement pond (referred to as sewage water in this study) and is then transferred to a lagoon, where the duckweed (Lemnaceae) is grown (referred to as lagoon). The duckweed is harvested and used as feed for the fish in a separate pond (referred to as fish pond). From this collection, representatives of 288 PhP types were subjected to antibiotic susceptibility testing for eight antimicrobials by broth microdilution method. The overall resistance rates among Aeromonas isolates from the treatment plant were highest for ampicillin (87%) and erythromycin (79%) followed by cephalothin (58%), nalidixic acid (52%), streptomycin (51%), tetracycline (31%), chloramphenicol (13%) and gentamicin (8%). A significantly lower prevalence of antibiotic resistance was found in Aeromonas from environmental control water, patient stool samples, duckweed and fish compared to sewage water isolates. The prevalence of resistance in the sewage water was not significantly reduced compared to the lagoon water and fish pond. Throughout the treatment system, the frequencies of resistant strains were found to diminish during the sewage water purification process, i.e. in the lagoon where sewage water is used to grow the duckweed. However, the frequency of resistant strains again increased in the fish pond where sewage grown duckweed is used for aquaculture. Among the selected isolates, two multiresistant clonal groups of Aeromonas caviae HG4 were identified that exhibited indistinguishable PhP and amplified fragment length polymorphism fingerprints and shared a common plasmid of approximately 5 kb. Representatives of both groups were recovered from almost every part of the sewage treatment plant but not in the control ponds nor in human samples, which suggests that specific multiresistant Aeromonas clones are able to persist and spread throughout the entire purification process. PMID:19459063

Rahman, Mokhlasur; Huys, Geert; Kühn, Inger; Rahman, Motiur; Möllby, Roland

2009-10-01

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Persistence, Transmission, and Virulence Characteristics of Aeromonas Strains in a Duckweed Aquaculture-Based Hospital Sewage Water Recycling Plant in Bangladesh?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The persistence and transmission of Aeromonas in a duckweed aquaculture-based hospital sewage water treatment plant in Bangladesh was studied. A total of 670 samples from different sites of the hospital sewage water treatment plant, from feces of hospitalized children suffering from diarrhea, from environmental control ponds, and from feces of healthy humans were collected over a period of three years. In total, 1,315 presumptive Aeromonas isolates were biochemically typed by the PhenePlate r...

2007-01-01

9

Wastewater-grown duckweed may be safely used as fish feed.  

Science.gov (United States)

Duckweed has been used for the treatment of wastewater and as fish feed. A comparative study was carried out to determine (i) the efficacy of duckweed in treating hospital-based wastewater and (ii) the level of the microbial contamination of fish fed on wastewater-grown duckweed. There were two groups of ponds where fish farming was done. In one group of ponds (control ponds), duckweed that was grown using artificial fertilizer was used as fish feed; in another group (study ponds), wastewater-grown duckweed was used as fish feed. The faecal contamination of water, duckweed, and fish from study and control ponds were monitored by faecal coliform estimation. The presence of enteric pathogens among handlers, water, duckweed, and fish samples was also examined. It was observed that the faecal coliform counts of raw wastewater were 4.7 Log10 CFU/mL, which was reduced to duckweed. There was no significant difference (P > 0.05) in faecal coliform counts in water collected from duckweed ponds and fish ponds of study and control areas. The wastewater-grown duckweed did not pose any health hazard to the handlers. These results demonstrated that the wastewater-treated duckweed may be safely used as fish feed. PMID:15052321

Islam, M S; Kabir, M S; Khan, S I; Ekramullah, M; Nair, G B; Sack, R B; Sack, D A

2004-01-01

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Modeling duckweed growth in wastewater treatment systems  

Science.gov (United States)

Species of the genera Lemnaceae, or duckweeds, are floating aquatic plants that show great promise for both wastewater treatment and livestock feed production. Research conducted in the Southern High Plains of Texas has shown that Lemna obscura grew well in cattle feedlot runoff water and produced leaf tissue with a high protein content. A model or mathematical expression derived from duckweed growth data was used to fit data from experiments conducted in a greenhouse in Lubbock, Texas. The relationship between duckweed growth and the total nitrogen concentration in the mediium follows the Mitscherlich Function and is similar to that of other plants. Empirically derived model equations have successfully predicted the growth response of Lemna obscura.

Landesman, L.; Parker, N. C.; Fedler, C. B.; Konikoff, M.

2005-01-01

11

Persistence of Escherichia coli on injured iceberg lettuce in the field, overhead irrigated with contaminated water.  

Science.gov (United States)

Fresh produce is increasingly implicated in food-related illnesses. Escherichia coli can survive in soil and water and can be transferred onto plant surfaces through farm management practices such as irrigation. A trial was conducted to evaluate the impact of field conditions on E. coli persistence on iceberg lettuce irrigated with contaminated water, and the impact of plant injury on the persistence of E. coli. Lettuce heads were injured at 14, 7, 3, 2, 1, and 0 days before inoculation, with uninjured heads used as a control. All lettuce heads (including controls) were overhead irrigated with a mixture of nonpathogenic E. coli strains (10(7) CFU/ml). E. coli counts were measured on the day of inoculation and 5 days after, and E. coli was detected on all lettuce head samples. Injury immediately prior to inoculation and harvest significantly (P = 0.00067) increased persistence of E. coli on lettuce plants. Harsh environmental conditions (warm temperatures, limited rainfall) over 5 days resulted in a 2.2-log reduction in E. coli counts on uninjured lettuce plants, and lettuce plants injured more than 2 days prior to inoculation had similar results. Plants with more recent injuries (up to 2 days prior to inoculation) had significantly (P = 7.6 x 10(-6)) greater E. coli persistence. Therefore, growers should postpone contaminated water irrigation of lettuce crops with suspected injuries for a minimum of 2 days, or if unavoidable, use the highest microbiological quality of water available, to minimize food safety risks. PMID:19343931

Barker-Reid, Fiona; Harapas, Dean; Engleitner, Siegfried; Kreidl, Simone; Holmes, Robert; Faggian, Robert

2009-03-01

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Potential cross-contamination of E. coli between lettuce and wash water simulating an industrial fresh-cut lettuce wash process  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim was to provide information about E. coli contamination of washing water to prevent water becoming a vehicle for transfer of microbial contamination to lettuce and to get insight on the factors affecting proper water management. A lettuce wash process was simulated to determine (1) the ability to use “clean” water and the tolerable E. coli levels for “clean” water and its’ potential to respect it upon re-use of water in the first washing bath, (2) the need and effect of using...

Holvoet, Kevin; Sampers, Imca; Haute, Sam; Jacxsens, Liesbeth; Uyttendaele, Mieke

2012-01-01

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Optimizing water management to control respiration rate and reduce browning and microbial load of fresh-cut romaine lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We studied the influence of both deficit and excess irrigation on the quality of fresh-cut romaine lettuce, the second most important type of lettuce after iceberg. The influence of different irrigation regimes on respiration rate, browning and microbial quality of fresh-cut romaine lettuce (Lactuca sativa L.) was studied in 6 different harvests during 3 consecutive years. The total amount of water supplied to the crop was calculated taking into account the irrigation water and rainfall. Six ...

2013-01-01

14

THE ROLE OF DUCKWEED (LEMNA MINOR L. IN SECONDARY CLARIFIER TANKS  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the effects of duckweed (Lemna minor L. presence on the effluent water quality and settling characteristics in the secondary clarifier tank of a conventional biological treatment plant were investigated. For this purpose, the performances of the secondary clarifier with and without duckweed were compared. In the secondary clarifier tank with duckweed, COD, BOD5, ammonium and phosphate removal efficiencies were higher by 15, 25, 35 and 45%, respectively. SS concentration of effluent and values of sludge volume index (SVI were the same. The results showed that duckweed contributes to treatment efficiency of conventional biological treatment plant, which reduces the need of tertiary nutrients removal.

Engin Gürtekin

2008-01-01

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Predicting perchlorate uptake in greenhouse lettuce from perchlorate, nitrate, and chloride irrigation water concentrations.  

Science.gov (United States)

Perchlorate (ClO) has been detected in edible leafy vegetables irrigated with Colorado River water. The primary concern has been the ClO concentration in lettuce ( L. var. L.). There has been a limited number of studies on ClO uptake, but the interactive effect of other anions on ClO uptake is not known in detail. We conducted a greenhouse ClO uptake experiment using two types of lettuce (iceberg and butterhead) to investigate the interaction of uptake of ClO, Cl, and NO on ClO uptake under controlled conditions. We examined three concentrations of ClO, 40, 220, and 400 nmol/L; Cl at 2.5, 13.75, and 25 mmol/L; and NO at 2, 11, and 20 mmol/L. Perchlorate was taken up the most in lettuce when ClO was the greatest and NO and Cl were lowest in concentration in the irrigation water. More ClO was detected in leafy material than in root tissue. In general, the outer leaves of iceberg and butterhead lettuce contained more ClO than did the inner leaves. The results indicate that selective ClO uptake occurs for green leaf lettuce. A predictive model was developed to describe the ClO concentration in lettuce as related to the Cl, NO, and ClO concentration in the irrigation water. Research results can be utilized to elucidate the effect of salts on the accumulation and uptake of ClO by edible leafy vegetables. PMID:23673756

Ha, Wonsook; Suarez, Donald L; Lesch, Scott M

2013-01-01

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Assessment of Heavy Metals in Waste-Water Irrigated Lettuce in Ghana: The Case of Tamale Municipality  

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Full Text Available An assessment of some heavy metals concentrations in lettuce in irrigated with waste water in Tamale Metropolis in Ghana has been carried out. Analysis of water and lettuce samples revealed that the mean concentrations of Fe, Mn, Cu, Zn, Cd and Pb in lettuce were 0.436, 0.345, 0.068, 0.017, 0.04 and 0.038 mg/L and 0.167, 0.163, 0.104, 0.127, 0.142 respectively. With exception of Mn and Cd, the concentrations of heavy metals in the irrigation water, irrigated soils and irrigated lettuce, were within the FAO recommended levels. The mean concentrations of nutrients (NO3-N, SO4 and PO4-P in the wastewater-irrigated lettuce, and well water-irrigated lettuce were 15.36, 0.88, 0.28 and 19.09, 1.117, 0.0573 respectively. Though, heavy metals concentrations in the lettuce were low, regular monitoring are required to prevent heavy metal accumulation with their attendant health implications in the consuming public.

Maxwell Anim Gyampo

2012-10-01

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Differences in the binding of human norovirus to and from romaine lettuce and raspberries by water and electrolyzed waters.  

Science.gov (United States)

Food contamination by human norovirus (hNoV) is a major cause of gastrointestinal disease. We evaluated the effectiveness of removing inoculated hNoV from the surfaces of raspberries and romaine lettuce by a simple wash in tap water and in different forms of electrolyzed water (EW), including acidic EW (AEW), neutral EW (NEW), and basic EW (BEW). A simple rinsing or soaking in water was able to remove >95% of hNoV from surface-inoculated raspberries. In contrast, only 75% of hNoV was removed from surface-inoculated romaine lettuce by rinsing in tap water. An AEW wash enhanced the binding of hNoV to raspberries and lettuce. Only 7.5% (±10%) and 4% (±3.1%) of hNoV were removed by AEW wash from surface-inoculated raspberries and lettuce, respectively. When raspberries and lettuce were prewashed with NEW or BEW prior to surface inoculation, an AEW wash likewise resulted in significantly less removal of hNoV compared with untreated samples. A prewash with AEW significantly decreased the removal of hNoV from raspberries and lettuce when they were washed with NEW, from 90.6 to 51% and from 76 to 51.3% , respectively. There are minimal or no improvements gained by use of any of the EWs instead of a regular tap water wash in removal of hNoV from produce. However, use of AEW shows a significant decrease in the removal of hNoV from contaminated produce compared with other water rinses. The ability to remove hNoV from different types of produce varies, possibly due to differences among types of ligand-like molecules that bind hNoV. The distribution of hNoV on raspberries and lettuce was studied using recombinant Norwalk-like particles (rNVLP). By immunofluorescence microscopy, we were able to observe binding of rNVLP only to vein areas of romaine lettuce, suggesting that the virus was binding to specific molecules in these areas. Random binding of rNVLP occurred only with raspberries prewashed with AEW or washed with AEW. PMID:21819668

Tian, Peng; Yang, David; Mandrell, Robert

2011-08-01

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Duck-Weed as an ecotoxicological biotest  

International Nuclear Information System (INIS)

Since 1989 duck-weed (Spirodela polyrrhiza) has been used as an ecotoxicological biotest at the Radioecological Section of Institute of Botany. It was used to estimate precipitation toxicity of Mazheikiai and Akmene regions, waste waters of industrial galvanic departments, water reservoirs of the Ignalina and Leningrad NPP, also the Dniepr cascade. The data obtained showed Spirodela polyrrhiza to be a rather sensitive and specific biotest for the estimation of contamination with heavy metals. Spirodela polyrrhiza is advisable to estimate pollution of the air, waste-waters and solutions of heavy metals. (author). 12 refs., 3 figs., 4 tabs

1997-01-01

19

Literature review on duckweed toxicity testing.  

Science.gov (United States)

Duckweed commonly refers to a group of floating, flowering plants of the family Lemnaceae. Duckweed plants are fast growing and widely distributed. They are easy to culture and to test. Some reports suggest that duckweed plants are tolerant to environmental toxicity. Other studies, however, indicate that duckweed plants are as sensitive to toxicity as other aquatic species. Duckweed plants are especially suitable for use in complex effluent bioassays, and for testing herbicide pollution in the aquatic environment, lake and river pollution, sediment toxicity, and the like. Duckweed and algae represent different levels of complexity in the plant kingdom. They complement each other as phytotoxicity test organisms, instead of mutually excluding each other. Many duckweed species have been studied, primarily of the Lemna and Spirodela genera. Lemna minor and L. gibba have been recommended as standard test species. Differences in duckweed test methodology occur with regard to test types, test vessels, control tests, nutrient media, end points, and applications. PMID:2190824

Wang, W

1990-06-01

20

Literature review on duckweed toxicity testing  

Energy Technology Data Exchange (ETDEWEB)

Duckweed commonly refers to a group of floating, flowering plants of the family Lemnaceae. Duckweed plants are fast growing and widely distributed. They are easy to culture and to test. Some reports suggest that duckweed plants are tolerant to environmental toxicity. Other studies, however, indicate that duckweed plants are as sensitive to toxicity as other aquatic species. Duckweed plants are especially suitable for use in complex effluent bioassays, and for testing herbicide pollution in the aquatic environment, lake and river pollution, sediment toxicity, and the like. Duckweed and algae represent different levels of complexity in the plant kingdom. They complement each other as phytotoxicity test organisms, instead of mutually excluding each other. Many duckweed species have been studied, primarily of the Lemna and Spirodela genera. Lemna minor and L. gibba have been recommended as standard test species. Differences in duckweed test methodology occur with regard to test types, test vessels, control tests, nutrient media, end points, and applications. 76 references.

Wang, W. (Illinois State Water Survey, Peoria (USA))

1990-06-01

 
 
 
 
21

EFFECT OF WATER EXTRACTS FROM TISSUES OF COMMON BUCKWHEAT ON SEED GERMINATION AND SEEDLING GROWTH OF WINTER WHEAT AND LETTUCE  

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The effect of water extracts from common buckwheat (Fagopyrum esculentum Moench) tissues on seed germination and seedling growth of winter wheat and lettuce was examined. Two kinds of extracts were evaluated: from the aboveground parts and roots of common buckwheat (cv. Hruszowska). The effect of extracts was dependent on their kind, the time of action and the species of studied plants. Lettuce seeds were more sensitive to treating with extracts from buckwheat tissues than wheat seeds. Extrac...

Halina Mioduszewska; Józef Klocek; Marcin Horbowicz; Katarzyna Wolska

2013-01-01

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EFFECTIVENESS OF ELECTROLYZED OXIDIZING WATER FOR INACTIVATING Listeria monocytogenes IN LETTUCE  

Directory of Open Access Journals (Sweden)

Full Text Available The effectiveness of electrolyzed oxidizing (EO water for the inactivation of L. monocytogenes in suspension and when inoculated on lettuce leaves was evaluated. An electrolytic cell for the production of EO water was built and a solution of 5% NaCl was used. The EO water produced had a residual chlorine concentration of 29 parts per million (ppm and pH 2.83. Ten strains of L. monocytogenes isolated from processed chicken (109 CFU/ml were inoculated into 9 ml of EO water or 9 ml of deionized water (control and incubated at 15°C for 5, 10, 15 and 20 min. The surviving population of each strain was determined on Columbia agar. An exposure time of 5 min reduced the populations by approximately 6.6 log CFU/ml. The most resistant strains to sodium hypochlorite (NaOCl were selected and used in a strain mixture (9.56 log CFU/ml, 109UFC/ml approximately for the inoculation of 35 lettuce samples, by the dip inoculation method using distilled water as control. The population mean of L. monocytogenes after treatment with EO water and distilled water was reduced by 3.92 and 2.46 log CFU/ml respectively (p=0.00001. EO water and 6% acetic acid (vinegar were combined to improve the EO water effect on L. monocytogenes inoculated in lettuce; the effectiveness of this combination was examined. The results showed that there was a synergistic effect of both antimicrobial agents (population reduction by 5.49 log CFU/ml approximately on the viability of L. monocytogenes cells.

Casadiego Laíd Paola

2005-06-01

23

Arbuscular mycorrhizal symbiosis alleviates detrimental effects of saline reclaimed water in lettuce plants.  

Science.gov (United States)

The present study evaluated the effects of inoculation with arbuscular mycorrhizal fungi (AMF; Glomus iranicum var. tenuihypharum sp. nova) on the physiological performance and production of lettuce plants grown under greenhouse conditions and supplied with reclaimed water (RW; urban-treated wastewater with high electrical conductivity; 4.19 dS m(-1)). Four treatments, fresh water, fresh water plus AMF inoculation, RW and RW plus AMF inoculation, were applied and their effects, over time, analyzed. Root mycorrhizal colonization, plant biomass, leaf-ion content, stomatal conductance and net photosynthesis were assessed. Overall, our results highlight the significance of the AMF in alleviation of salt stress and their beneficial effects on plant growth and productivity. Inoculated plants increased the ability to acquire N, Ca, and K from both non-saline and saline media. Moreover, mycorrhization significantly reduced Na plant uptake. Under RW conditions, inoculated plants also showed a better performance of physiological parameters such as net photosynthesis, stomatal conductance and water-use efficiency than non-mycorrhizal plants. Additionally, the high concentration of nutrients already dissolved in reclaimed water suggested that adjustments in the calculation of the fertigation should be conducted by farmers. Finally, this experiment has proved that mycorrhization could be a suitable way to induce salt stress resistance in iceberg lettuce crops as plants supplied with reclaimed water satisfied minimum legal commercial size thresholds. Moreover, the maximum values of Escherichia coli in the reclaimed water were close to but never exceeded the international thresholds established (Spanish Royal Decree 1620/2007; Italian Decree, 2003) and hence lettuces were apt for sale. PMID:24287607

Vicente-Sánchez, J; Nicolás, E; Pedrero, F; Alarcón, J J; Maestre-Valero, J F; Fernández, F

2014-07-01

24

Duckweed rising at Chengdu: summary of the 1st International Conference on Duckweed Application and Research.  

Science.gov (United States)

Duckweeds, plants of the Lemnaceae family, have the distinction of being the smallest angiosperms in the world with the fastest doubling time. Together with its naturally ability to thrive on abundant anthropogenic wastewater, these plants hold tremendous potential to helping solve critical water, climate and fuel issues facing our planet this century. With the conviction that rapid deployment and optimization of the duckweed platform for biomass production will depend on close integration between basic and applied research of these aquatic plants, the first International Conference on Duckweed Research and Applications (ICDRA) was organized and took place in Chengdu, China, from October 7th to 10th of 2011. Co-organized with Rutgers University of New Jersey (USA), this Conference attracted participants from Germany, Denmark, Japan, Australia, in addition to those from the US and China. The following are concise summaries of the various oral presentations and final discussions over the 2.5 day conference that serve to highlight current research interests and applied research that are paving the way for the imminent deployment of this novel aquatic crop. We believe the sharing of this information with the broad Plant Biology community is an important step toward the renaissance of this excellent plant model that will have important impact on our quest for sustainable development of the world. PMID:22318677

Zhao, Hai; Appenroth, Klaus; Landesman, Louis; Salmeán, Armando A; Lam, Eric

2012-04-01

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Dried duckweed and commercial feed promote adequate growth performance of tilapia fingerlings  

Directory of Open Access Journals (Sweden)

Full Text Available The present study evaluated Nile tilapia when fed on dried duckweed in combination with commercial feed, aiming at reducing production costs. Three diets, which consisted of commercial feed (40% crude protein, dried duckweed or a combination of commercial feed and dried duckweed were fed to triplicate groups of 20 tilapia (Oreochromis niloticus fingerlings. Fish weighing 3.2 ± 0.94g were stocked in nine 1-m3 net cages and fed twice a day for 50 days. The final average weights of fingerlings fed commercial feed (21.67g and50% feed + 50% dried duckweed (19.53g were not different (p<0.05. Likewise, the specific growth rate did not differ between fish receiving these dietary treatments. Weight gain decreased as water temperature decreased along the experimental period, increasing feed conversion mainly for fingerlings fed on dried duckweed only. Also, when fed alone dried duckweed promoted the lowest weight gain and specific growth rate. It was confirmed that dried duckweed can replace 50% (1:1 dry weight tilapia fingerling 40% crude protein feed for a period of at least 50 days, without reducing growth.

Juan Esquivel

2008-09-01

26

Assessment of Heavy Metals in Lettuce Grown in Soils Irrigated with Different Water Sources in the Accra Metropolis  

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Full Text Available This study was carried out to assess the levels of different heavy metals like Iron, Manganese, Copper, Zinc, Cadmium and Lead in three different irrigation water sources, irrigated soils and irrigated lettuce. The result indicates positive and significant correlation of heavy metals concentrations between the irrigation water, irrigated soils and irrigated lettuce. The range of various heavy metals in drained water irrigated lettuce was 162.00-190.00, 60.25-78.25, 6.03-8.80 and 23.88-52.00 mg/kg in Fe, Mn, Cu and Zn, respectively. Generally, mean heavy metal concentrations of the water, soil and lettuce from two vegetable growing sites were within the FAO/WHO recommended maximum concentrations for crop production. Although the levels of heavy metals in the irrigation water, irrigated soils and irrigated lettuce were below the recommended limits, regular monitoring of these metal levels from these sources is essential to prevent excessive heavy metal buildup in vegetables in general.

Mark O. Akrong

2012-05-01

27

Improving Water Use Efficiency of Lettuce (Lactuca sativa L.) Using Phosphorous Fertilizers.  

Science.gov (United States)

A greenhouse pot experiment was conducted to evaluate the effect of phosphorous (P) fertilizers application to an alkaline calcareous soil on the water use efficiency (WUE) of lettuce cultivar "robinson" of iceberg type. Head fresh and dry weights, total water applied and WUE were affected significantly by the P fertilizer type and rate. P fertilizers addition induced a significant enhancement in the WUE and fresh and dry weights of the crop. A local phosphate rock (PR) applied directly was found to be inferior to the other types of P fertilizers (Mono ammonium phosphate (MAP), Single superphosphate (SSP), and Di ammonium phosphate ((DAP)). MAP fertilizer at 375 and 500 kg P2O5/ha application rates recorded the highest significant values of head fresh weight and WUE, respectively. PMID:24255857

Alkhader, Asad M F; Abu Rayyan, Azmi M

2013-01-01

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Assessing water hyacinth (Eichhornia crassopes) and lettuce (Pistia stratiotes) effectiveness in aquaculture wastewater treatment.  

Science.gov (United States)

Water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) were analyzed to determine their effectiveness in aquaculture wastewater treatment in Malaysia. Wastewater from fish farm in Semanggol Perak, Malaysia was sampled and the parameters determined included, the pH, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrite phosphate (PO4(3-)), nitrate (NO(3-)), nitrite (NO(-2)), ammonia (NH3), and total kjedahl nitrogen (TKN). Also, hydroponics system was set up and was added with fresh plants weights of 150 +/- 20 grams Eichhornia crassipes and 50 +/- 10 grams Pistia stratiotes during the 30 days experiment. The phytoremediation treatment with Eichhornia crassipes had pH ranging from 5.52 to 5.59 and from 4.45 to 5.5 while Pistia stratiotes had its pH value from 5.76 to 6.49 and from 6.24 to 7.07. Considerable percentage reduction was observed in all the parameters treated with the phytoremediators. Percentage reduction of turbidity for Eichhornia crassipes were 85.26% and 87.05% while Pistia stratiotes were 92.70% and 93.69% respectively. Similar reductions were observed in COD, TKN, NO(3-), NH3, and PO4(3-). The capability of these plants in removing nutrients was established from the study. Removal of aquatic macrophytes from water bodies is recommended for efficient water purification. PMID:22567705

Akinbile, C O; Yusoff, Mohd S

2012-03-01

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Determination of nitrate in lettuce by ion chromatography after microwave water extraction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lettuce is worldwide known as the most important vegetable. In this context, most farmers are searching new techniques for best quality products including hydropony. However, nitrate is of great concern, since it has a negative impact on human metabolism. The main objective of the present work was to evaluate the nitrate content of lettuce produced by conventional and hydroponic systems. The determination was conducted by ion chromatography and a new method of extraction was tested using micr...

Humberto Brevilato Novaes; Delmo Santiago Vaitsman; Paulo Bechara Dutra; Daniel Vidal Pérez

2009-01-01

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Determination of nitrate in lettuce by ion chromatography after microwave water extraction  

Directory of Open Access Journals (Sweden)

Full Text Available Lettuce is worldwide known as the most important vegetable. In this context, most farmers are searching new techniques for best quality products including hydropony. However, nitrate is of great concern, since it has a negative impact on human metabolism. The main objective of the present work was to evaluate the nitrate content of lettuce produced by conventional and hydroponic systems. The determination was conducted by ion chromatography and a new method of extraction was tested using microwave oven digestion. The results indicated that nitrate level produced in the conventional system was lower than in the hydroponic system.

Humberto Brevilato Novaes

2009-01-01

31

Biofortification of lettuce (Lactuca sativa L.) with iodine: The effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce grown in water culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

BACKGROUND: Iodine is an essential trace element for humans. Two billion individuals have insufficient iodine intake. Biofortification of vegetables with iodine offers an excellent opportunity to increase iodine intake by humans. The main aim was to study the effect of iodine form and concentration in the nutrient solution on growth, development and iodine uptake of lettuce, grown in water culture. RESULTS: In both a winter and summer trial, dose rates of 0, 13, 39, 65, and 90 or 129 µg iod...

Voogt, W.; Holwerda, H. T.; Khodabaks, M. R.

2010-01-01

32

Efficacy of chlorine, acidic electrolyzed water and aqueous chlorine dioxide solutions to decontaminate Escherichia coli O157:H7 from lettuce leaves.  

Science.gov (United States)

This study compared the efficacy of chlorine (20-200 ppm), acidic electrolyzed water (50 ppm chlorine, pH 2.6), acidified sodium chlorite (20-200 ppm chlorite ion concentration, Sanova), and aqueous chlorine dioxide (20-200 ppm chlorite ion concentration, TriNova) washes in reducing populations of Escherichia coli O157:H7 on artificially inoculated lettuce. Fresh-cut leaves of Romaine or Iceberg lettuce were inoculated by immersion in water containing E. coli O157:H7 (8 log CFU/ml) for 5 min and dried in a salad spinner. Leaves (25 g) were then washed for 2 min, immediately or following 24 h of storage at 4 degrees C. The washing treatments containing chlorite ion concentrations of 100 and 200 ppm were the most effective against E. coli O157:H7 populations on Iceberg lettuce, with log reductions as high as 1.25 log CFU/g and 1.05 log CFU/g for TriNova and Sanova wash treatments, respectively. All other wash treatments resulted in population reductions of less than 1 log CFU/g. Chlorine (200 ppm), TriNova, Sanova, and acidic electrolyzed water were all equally effective against E. coli O157:H7 on Romaine, with log reductions of approximately 1 log CFU/g. The 20 ppm chlorine wash was as effective as the deionized water wash in reducing populations of E. coli O157:H7 on Romaine and Iceberg lettuce. Scanning electron microscopy indicated that E. coli O157:H7 that was incorporated into biofilms or located in damage lettuce tissue remained on the lettuce leaf, while individual cells on undamaged leaf surfaces were more likely to be washed away. PMID:19428137

Keskinen, Lindsey A; Burke, Angela; Annous, Bassam A

2009-06-30

33

BIOSORPTIVE REMOVAL OF HEAVY METALS FROM WASTEWATER USING DUCKWEED  

Directory of Open Access Journals (Sweden)

Full Text Available Water pollution has been recognized as a problem for decades. The use of heavy metals in industries and their regular mining increases their concentration in water bodies. Unlike organic compounds, metals cannot degrade, and therefore effective cleanup requires their immobilization to reduce or remove toxicity. A few conventional methods employed to remove heavy metals from wastewater are expensive, require skilled labors and maintenance. Therefore, the use of aquatic plants has come up since the last few decades. Duckweed is onesuch plant employed as a biosorbent and has been considered a better alternative than any other aquatic plant because of high tolerance to cold than water hyacinth, more easilyharvested than algae, capable of rapid growth (0.1 to 0.5 g g-1 day-1 and small size of plant. This study aims to determine the suitability of this plant for biosorbing toxic heavy metalscommonly found in industrial wastewater, domestic wastewater, and seepage water.

Ankita Suhag

2011-10-01

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Using full-scale duckweed ponds as the finish stage for swine waste treatment with a focus on organic matter degradation.  

Science.gov (United States)

The rapid increase in the number of swine has caused pronounced environmental impacts worldwide, especially on water resources. As an aggregate, smallholdings have an important role in South American pork production, contributing to the net diffusion of pollution. Thus, duckweed ponds have been successfully used for swine waste polishing, mainly for nutrient removal. Few studies have been carried out to assess organic matter degradation in duckweed ponds. Hence, the present study evaluated the efficiency of two full-scale duckweed ponds for organic matter reduction of swine waste on small pig farms. Duckweed ponds, in series, received the effluent after an anaerobic biodigester and storage pond, with a flow rate of 1 m(3) day(-1). After 1 year of monitoring, an improvement in effluent quality was observed, with a reduction in biochemical oxygen demand (BOD) and total chemical oxygen demand (tCOD), respectively, of 94.8 and 96.7%, operating at a loading rate of approximately 27 kgBOD ha(-1) day(-1) and 131 kgCOD ha(-1) day(-1). Algae inhibition due to duckweed coverage was strongly observed in the pond effluent, where chlorophyll a and turbidity remained below 25 ?g L(-1) and 10 NTU. Using the study conditions described herein, duckweed ponds were shown to be a suitable technology for swine waste treatment, contributing to the environmental sustainability of rural areas. PMID:24845333

Mohedano, R A; Costa, R H R; Hofmann, S M; Belli Filho, P

2014-01-01

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Shoot growth, root growth and resource capture under limiting water and N supply for two cultivars of lettuce (Lactuca sativa L.) (online first)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background and aims - To improve vegetable crops adapted to low input and variable resource availability, better understanding is needed of root system functioning, including nitrogen and water capture. Methods - This study quantified shoot and root development and patterns of water and nitrate capture of two lettuce cultivars subjected to temporary drought at two development stages (Trial 1) or to continuous, localized drought and/or nitrate shortage (Trial 2). Results - In Trial 1, early dr...

2013-01-01

36

Duckweed Aquaculture: A New Aquatic Farming System for Developing Countries.  

Science.gov (United States)

The purpose of the booklet is to present a group of tiny aquatic plants commonly known as 'duckweeds' as a promising new commercial aquaculture crop. Duckweed species are members of the taxonomic family Lemnaceae. They are ubiquitous, hardy, and grow rapi...

P. Skillicorn W. Spira W. Journey

1993-01-01

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Tapioca-starch wastewater toxicity characterized by Microtox and duckweed tests  

Energy Technology Data Exchange (ETDEWEB)

The toxicity of treated and untreated effluents from a tapioca (cassava), Manihot esculenta, starch industry in Thailand were tested on Microtox and a subtropical duckweed, Lemna aequinoctialis. Untreated samples demonstrated high toxicity in both tests, but also the treated effluent was toxic to duckweed. Aging of wastewater resulted in decreased toxicity which was partly correlated to cyanide content, but other (unidentified) components of the tapioca tubers also contribute to the toxicity. Considering the present findings and the fact that the majority of the tapioca starch industries in Southeast Asia have no effluent treatment there is a great risk for severe effects on crops (e.g. young stages of rice, vegetables, etc.) when the wastewater in traditional way is used for irrigation of farmland. Negative effects on local aquaculture and/or sensitive stages of valuable feral fish and crustacea populations in receiving water bodies can also be expected. 32 refs, 6 tabs

Bengtsson, Bengt-Erik (Stockholm University, Institute of Applied Environmental Research, Laboratory for Aquatic Ecotoxicology, Nykoeping (Sweden)); Triet, T. (University of Wisconsin, Institute for Environmental Studies, Madison, WI (United States))

1994-12-01

38

Crescimento, consumo hídrico e composição mineral de alface cultivada em hidroponia com águas salinas / Growth, water consumption and mineral composition of lettuce in hydroponic system with saline water  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Objetivou-se, com este trabalho, avaliar o crescimento, o consumo hídrico e a extração de nutrientes, por alface (Lactuca sativa L.) em sistema hidropônico NFT (fluxo laminar de nutrientes), com a utilização de águas salinas no preparo da solução nutritiva e reposição da lâmina diária evapotranspira [...] da. Foram conduzidos dois experimentos, em ambiente protegido. O delineamento experimental foi em blocos ao acaso, sendo estudados os efeitos de cinco níveis de salinidade da água, utilizando-se NaCl. O aumento da salinidade da água reduziu, de forma linear, o crescimento e o consumo hídrico da alface. A salinidade reduziu a concentração de macronutrientes na parte aérea, mas não se observaram sintomas de deficiência nutricional. O rendimento (massa de matéria fresca da parte aérea) foi reduzido entre 6 e 6,5% por dS m-1, no primeiro e segundo cultivo, respectivamente. Os resultados obtidos em sistema de cultivo NFT podem indicar a possibilidade do uso da água salina como alternativa para produção de hortaliças, para produtores que têm disponibilidade restrita de água doce, porém, com redução de produtividade. Abstract in english The objective of this study was to evaluate the growth, water consumption and extraction of nutrients of lettuce (Lactuca sativa L.) in a NFT (nutrient film technique) in hydroponic system using saline water. Two experiments were conducted in a protected environment. The experiment was arranged in a [...] completely randomized design with five replications and five levels of salinity in the irrigation water using NaCl. Increasing water salinity reduced the growth and water consumption of lettuce linearly. The salinity reduced the macronutrient concentration, but symptoms of nutritional deficiency were not observed. The lettuce yield (shoot fresh matter) was reduced by 6% and 6.5% per dS m¹, in the first and second crops, respectively. The results obtained in the NFT system indicate the possibility of using saline water as an alternative for the production of vegetables by farmers who have freshwater restriction, although with a reduction in the yield.

Dalva, Paulus; Eloi, Paulus; Gilmar Antônio, Nava; Cláudia Andrade, Moura.

39

Estratégias de uso de água salobra na produção de alface em hidroponia NFT / Strategies for use of brackish water in NFT hydroponic lettuce production  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Plantas de alface crespa 'Verônica' foram cultivadas em condições hidropônicas, objetivando avaliar três diferentes estratégias de emprego de águas salobras: 1) águas salobras para reposição das perdas por evapotranspiração (ETc) e água doce para o preparo da solução nutritiva (SN); 2) águas salobra [...] s para o preparo da SN e água doce para reposição da ETc; 3) águas salobras para o preparo da SN e reposição da ETc. Os níveis de salinidade da água foram obtidos pela adição de NaCl à água doce (0,27 dS m-1): 1,45; 2,51; 3,6; 5,41 e 7,5 dS m-1. O experimento foi conduzido em quatro blocos aleatorizados, com quatro repetições por tratamento. Uma estrutura de pesquisa foi construída com 72 parcelas que simulam a técnica do fluxo laminar de nutrientes (NFT). O uso de água salobra apenas para repor a ETc não produziu efeito sobre a produção da alface. Por outro lado, o uso de águas salobras para o preparo da SN e água doce para reposição da ETc, reduziu o rendimento da alface (massa de matéria fresca da parte aérea) em 4,99% por (dS m-1). O rendimento foi reduzido em 7% por dS m-1 quando águas salobras foram usadas tanto para o preparo da SN quanto para reposição da ETc. Apesar da redução linear da produção da alface com o aumento da salinidade da água, sintomas depreciativos para a qualidade da alface hidropônica não foram registrados. Abstract in english Plants of crisphead lettuce cv. 'Verônica' were grown under hydroponic conditions aiming to evaluate three different strategies of brackish waters utilization: 1) brackish waters to replace the evapotranspiration loss (ETc) and fresh water to prepare nutrient solution (NS); 2) brackish waters to pre [...] pare NS and fresh water to replace the ETc; 3) brackish waters to prepare NS and replace ETc. The levels of water salinity were obtained by addition of NaCl to fresh water (0.27 dS m-1): 1.45; 2.51; 3.6; 5.41 and 7.5 dS m-1. The experiment was conducted in randomized blocks with four replications per treatment. A research structure was built with 72 experimental units which simulate the nutrient film technique (NFT). The use of brackish water only to replace the ETc did not affect the lettuce yield. On the other hand, the use of brackish waters to prepare NS, and fresh water to replace the ETc loss, reduce the lettuce yield (shoot fresh matter) by 4.99% per (dS m-1). The lettuce yield was reduced by 7% per dS m-1 as brackish water was used to prepare NS and replace ETc loss. Despite the linear decline of lettuce yield as the water salinity increased, depreciative symptoms for quality of hydroponic lettuce were not registered.

Márcio S., Alves; Tales M., Soares; Luana T., Silva; Joseane P., Fernandes; Mariana L. A., Oliveira; Vital P. S., Paz.

40

Nitrogen Fixation (Acetylene Reduction) Associated with Duckweed (Lemnaceae) Mats  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Duckweed (Lemnaceae) mats in Texas and Florida were investigated, using the acetylene reduction assay, to determine whether nitrogen fixation occurred in these floating aquatic macrophyte communities. N2-fixing microorganisms were enumerated by plating or most-probable-number techniques, using appropriate N-free media. Results of the investigations indicated that substantial N2-fixation (C2H2) was associated with duckweed mats in Texas and Florida. Acetylene reduction values ranged from 1 to ...

Zuberer, D. A.

1982-01-01

 
 
 
 
41

Relationship between lead uptake by lettuce and water-soluble low-molecular-weight organic acids in rhizosphere as influenced by transpiration.  

Science.gov (United States)

The relationship between Pb uptake by leaf lettuce ( Lactuca sativa L.) and water-soluble low-molecular-weight organic acids (LMWOAs) in rhizosphere, as influenced by transpiration (high and low), has been studied. Studies were carried out by culturing lettuce plants grown for 2 weeks in pots filled with quartz sand mixed with anion-exchange resin and then for 30 days in a greenhouse. The potted lettuce plants were subjected to stress by the addition of Pb(NO 3) 2 solutions (100, 200, and 300 mg of Pb L (-1)) and by high and low transpiration treatments for another 10-day period. Blank experiments (without addition of Pb(NO 3) 2 solutions to the pots) were also run. There were no significant differences in the growth of the plants with the addition of Pb(NO 3) 2 solutions in either of the transpirations studies. Uptake of Pb by the shoots and roots of the plants was found to be proportional to the concentration of Pb solutions added, and more accumulation was observed in the roots than in the shoots at the end of days 3 and 10. High transpiration caused more Pb uptake than did low transpiration. One volatile acid (propionic acid) and nine nonvolatile acids (lactic, glycolic, oxalic, succinic, fumaric, oxalacetic, d-tartaric, trans-aconitic, and citric acids) in rhizosphere quartz sand or anion-exchange resin were identified and quantified by gas chromatography analysis with a flame ionization detector. The amount of LMWOAs in rhizosphere quartz sand or anion-exchange resin increased with higher amounts of Pb in quartz sand solution and also with longer duration of the study. The total quantities of the LMWOAs in the rhizosphere quartz sand or anion-exchange resin were significantly higher under high and low transpiration with a 300 mg of Pb L (-1) solution addition at the end of day 10. Compared with our previous related studies (published work), the present study shows that the presence of LMWOAs in rhizosphere does not significantly affect Pb uptake by lettuce plants under high and low transpiration. A physiological mechanism of the roots of lettuce plants governing the relationship between Pb contamination level and quantity of water-soluble LMWOAs in rhizosphere quartz sand and resin, as influenced by transpiration, was proposed. PMID:17894455

Liao, Yuan Chung; Chang Chien, Shui-Wen; Wang, Min-Chao; Shen, Yuan; Seshaiah, Kalluru

2007-10-17

42

Modeling growth of Escherichia coli O157:H7 in fresh-cut lettuce treated with neutral electrolyzed water and under modified atmosphere packaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study was to evaluate and model the growth of Escherichia coli O157:H7 in fresh-cut lettuce submitted to a neutral electrolyzed water (NEW) treatment, packaged in passive modified atmosphere and subsequently stored at different temperatures (4, 8, 13,16 degrees C) for a maximum of 27 days. Results indicated that E. coli O157:H7 was able to grow at 8, 13, and 16 degrees C, and declined at 4 degrees C. However at 8 degrees C, the lag time lasted 19 days, above the typical sh...

2014-01-01

43

Growing duckweed to recover nutrients from wastewaters and for production of fuel ethanol and animal feed  

Energy Technology Data Exchange (ETDEWEB)

Lemnaceae or duckweed is an aquatic plant that can be used to recover nutrients from wastewaters. The grown duckweed can be a good resource of proteins and starch, and utilized for the production of value-added products such as animal feed and fuel ethanol. In the last eleven years we have been working on growing duckweed on anaerobically treated swine wastewater and utilizing the duckweed for fuel ethanol production. Duckweed strains that grew well on the swine wastewater were screened in laboratory and greenhouse experiments. The selected duckweed strains were then tested for nutrient recovery under laboratory and field conditions. The rates of nitrogen and phosphorus uptake by the duckweed growing in the laboratory and field systems were determined in the study. The mechanisms of nutrient uptake by the duckweed and the growth of duckweed in a nutrient-limited environment have been studied. When there are nutrients (N and P) available in the wastewater, duckweed takes the nutrients from the wastewater to support its growth and to store the nutrients in its tissue. When the N and P are completely removed from the wastewater, duckweed can use its internally stored nutrients to keep its growth for a significant period of time. A modified Monod model has been developed to describe nitrogen transport in a duckweed-covered pond for nutrient recovery from anaerobically treated swine wastewater. Nutrient reserve in the duckweed biomass has been found the key to the kinetics of duckweed growth. Utilization of duckweed for value-added products has a good potential. Using duckweed to feed animals, poultry, and fish has been extensively studied with promising results. Duckweed is also an alternative starch source for fuel ethanol production. Spirodela polyrrhiza grown on anaerobically treated swine wastewater was found to have a starch content of 45.8% (dry weight). Enzymatic hydrolysis of the duckweed biomass with amylases yielded a hydrolysate with a reducing sugar content corresponding to 50.9% of the original dry duckweed biomass. Fermentation of the hydrolysate using yeast gave an ethanol yield of 25.8% of the original dry duckweed biomass. These results indicate that the duckweed biomass can produce significant quantities of starch that can be readily converted into ethanol. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Cheng, Jay J. [Department of Biological and Agricultural Engineering, North Carolina State University, Raleigh, North Carolina (United States); Stomp, Anne M. [Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, North Carolina (United States)

2009-01-15

44

Effect of Grape Seed Extract on Human Norovirus GII.4 and Murine Norovirus 1 in Viral Suspensions, on Stainless Steel Discs, and in Lettuce Wash Water  

Science.gov (United States)

The anti-norovirus (anti-NoV) effect of grape seed extract (GSE) was examined by plaque assay for murine norovirus 1 (MNV-1), cell-binding reverse transcription-PCR for human NoV GII.4, and saliva-binding enzyme-linked immunosorbent assay for human NoV GII.4 P particles, with or without the presence of interfering substances (dried milk and lettuce extract). GSE at 0.2 and 2 mg/ml was shown to reduce the infectivity of MNV-1 (>3-log PFU/ml) and the specific binding ability of NoV GII.4 to Caco-2 cells (>1-log genomic copies/ml), as well as of its P particles to salivary human histo-blood group antigen receptors (optical density at 450 nm of >0.8). These effects were decreased as increasing concentrations of dried milk (0.02 and 0.2%) or lettuce extract were added. Under an electron microscope, human NoV GII.4 virus-like particles showed inflation and deformation after treatment with GSE. Under conditions that simulated applications in the food industry, the anti-NoV effect of GSE using MNV-1 as a target organism was shown to be limited in surface disinfection (<1-log PFU/ml, analyzed in accordance with EN 13697:2001). However, a 1.5- to 2-log PFU/ml reduction in MNV-1 infectivity was noted when 2 mg of GSE/ml was used to sanitize water in the washing bath of fresh-cut lettuce, and this occurred regardless of the chemical oxygen demand (0 to 1,500 mg/ml) of the processing water.

Baert, Leen; Zhang, Dongsheng; Xia, Ming; Zhong, Weiming; Van Coillie, Els; Jiang, Xi; Uyttendaele, Mieke

2012-01-01

45

Ecophysiological tolerance of duckweeds exposed to copper  

Energy Technology Data Exchange (ETDEWEB)

Although essential for plants, copper can be toxic when present in supra-optimal concentrations. Metal polluted sites, due to their extreme conditions, can harbour tolerant species and/or ecotypes. In this work we aimed to compare the physiological responses to copper exposure and the uptake capacities of two species of duckweed, Lemna minor (Lm(EC1)) and Spirodela polyrrhiza (SP), from an abandoned uranium mine with an ecotype of L. minor (Lm(EC2)) from a non-contaminated pond. From the lowest Cu concentration exposure (25 {mu}M) to the highest (100 {mu}M), Lm(EC2) accumulated higher amounts of copper than Lm(EC1) and SP. Dose-response curves showed that Cu content accumulated by Lm(EC2) increases linearly with Cu treatment concentrations (r{sup 2} = 0.998) whereas quadratic models were more suitable for Lm(EC1) and SP (r{sup 2} = 0.999 and r{sup 2} = 0.998 for Lm(EC1) and SP, respectively). A significant concentration-dependent decline of chlorophyll a (chl a) and carotenoid occurred as a consequence of Cu exposure. These declines were significant for Lm(EC2) exposed to the lowest Cu concentration (25 {mu}M) whereas for Lm(EC1) and SP a significant decrease in chl a and carotenoids was observed only at 50 and 100 {mu}M-Cu. Electric conductivity (EC) and malondialdehyde (MDA) content increased after Cu exposure, indicating oxidative stress. Significant increase of EC was observed in Lm(EC2) for all Cu concentrations whereas the increase for Lm(EC1) and SP became significant only after an exposure to 50 {mu}M-Cu. On the contrary, for Lm(EC1), SP, and Lm(EC2), MDA content significantly increased even at the lowest concentration. Protein content and catalase (CAT) activity showed a decrease with an increase in Cu concentration. For the species Lm(EC1) and SP, a significant effect of copper on CAT activity was observed only at the highest concentration (100 {mu}M-Cu) whereas, for Lm(EC2), this effect started to be significant after an exposure to 50 {mu}M-Cu. Superoxide dismutase (SOD) activity increased with increasing concentrations of Cu, with a very similar trend between the three populations of duckweed. However, due to the facts that enzyme activity is expressed as units of activity per gram of protein and that protein content decreased with Cu exposure, the increase in SOD activity might partly result from a relative increase of this enzyme inside the pool of proteins. Consequently, the results obtained in our experimental conditions strongly suggest that duckweed species from the uranium-polluted area have developed mechanisms to cope with metal toxicity and that this tolerance is based on the existence of protective mechanism to limit the metal uptake rather than on an enhancement of the antioxidative metabolism.

Kanoun-Boule, Myriam [Centre for Functional Ecology, Department of Botany, University of Coimbra, Coimbra 3000-456 (Portugal)], E-mail: mkb@ci.uc.pt; Vicente, Joaquim A.F.; Nabais, Cristina [Centre for Functional Ecology, Department of Botany, University of Coimbra, Coimbra 3000-456 (Portugal); Prasad, M.N.V. [Department of Plant Sciences, University of Hyderabad, Hyderabad 500046 (India); Freitas, Helena [Centre for Functional Ecology, Department of Botany, University of Coimbra, Coimbra 3000-456 (Portugal)

2009-01-18

46

Elemental mapping of As and other elements in rootless duckweed Wolffia globosa  

International Nuclear Information System (INIS)

Distribution of arsenic and the relationship with other elements in aquatic macrophytes Wolffia globosa is helpful in understanding mechanisms of arsenic accumulation and detoxification, which will be important for arsenic phytofiltration in contaminated water by aquatic macrophytes. In this paper, we study the distribution features of As and seven more elements in rootless duckweed Wolffia globosa by means of ?XRF. The results indicated that the distribution of As was similar to that of K, Mn and Zn while differs from that of Cu, Fe, Ni and Ca. (authors)

2010-06-01

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Efficacy of sodium hypochlorite and peroxyacetic acid to reduce murine norovirus 1, B40-8, Listeria monocytogenes, and Escherichia coli O157:H7 on shredded iceberg lettuce and in residual wash water.  

Science.gov (United States)

The efficiency of sodium hypochlorite (NaOCl) and peroxyacetic acid (PAA) to reduce murine norovirus 1 (MNV-1), a surrogate for human norovirus, and Bacteroides fragilis HSP40-infecting phage B40-8 on shredded iceberg lettuce was investigated. The levels of removal of viruses MNV-1 and B40-8 were compared with the reductions observed for bacterial pathogens Listeria monocytogenes and Escherichia coli O157:H7. Two inoculation levels, one with a high organic load and the other containing a 10-fold lower number of pathogens and organic matter, showed that the effectiveness of NaOCl was greatly influenced by the presence of organic material, which was not observed for PAA. Moreover, the present study showed that 200 mg/liter NaOCl or 250 mg/liter PAA is needed to obtain an additional reduction of 1 log (compared with tap water) of MNV-1 on shredded iceberg lettuce, whereas only 250 mg/liter PAA achieved this for bacterial pathogens. None of the treatments resulted in a supplementary 1-log PFU/g reduction of B40-8 compared with tap water. B40-8 could therefore be useful as an indicator of decontamination processes of shredded iceberg lettuce based on NaOCl or PAA. Neither MNV-1, B40-8, nor bacterial pathogens could be detected in residual wash water after shredded iceberg lettuce was treated with NaOCl and PAA, whereas considerable numbers of all these microorganisms were found in residual wash water consisting solely of tap water. This study illustrates the usefulness of PAA and NaOCl in preventing cross-contamination during the washing process rather than in causing a reduction of the number of pathogens present on lettuce. PMID:19517733

Baert, Leen; Vandekinderen, Isabelle; Devlieghere, Frank; Van Coillie, Els; Debevere, Johan; Uyttendaele, Mieke

2009-05-01

48

Nitrogen fixation (acetylene reduction) associated with duckweed (lemnaceae) mats.  

Science.gov (United States)

Duckweed (Lemnaceae) mats in Texas and Florida were investigated, using the acetylene reduction assay, to determine whether nitrogen fixation occurred in these floating aquatic macrophyte communities. N(2)-fixing microorganisms were enumerated by plating or most-probable-number techniques, using appropriate N-free media. Results of the investigations indicated that substantial N(2)-fixation (C(2)H(2)) was associated with duckweed mats in Texas and Florida. Acetylene reduction values ranged from 1 to 18 mumol of C(2)H(4) g (dry weight) day for samples incubated aerobically in light. Dark N(2) fixation was always two- to fivefold lower. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (7 to 10 muM) reduced acetylene reduction to levels intermediate between light and dark incubation. Acetylene reduction was generally greatest for samples incubated anaerobically in the light. It was estimated that 15 to 20% of the N requirement of the duckweed could be supplied through biological nitrogen fixation. N(2)-fixing heterotrophic bacteria (10 cells g [wet weight] and cyanobacteria (10 propagules g [wet weight] were associated with the duckweed mats. Azotobacter sp. was not detected in these investigations. One diazotrophic isolate was classified as Klebsiella. PMID:16345992

Zuberer, D A

1982-04-01

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Microbiological quality and safety assessment of lettuce production in Brazil.  

Science.gov (United States)

The microbiological quality and safety of lettuce during primary production in Brazil were determined by enumeration of hygiene indicators Escherichia coli, coliforms and enterococci and detection of enteric pathogens Salmonella and E. coli O157:H7 in organic fertilizers, soil, irrigation water, lettuce crops, harvest boxes and worker's hands taken from six different lettuce farms throughout the crop growth cycle. Generic E. coli was a suitable indicator for the presence of Salmonella and E. coli O157:H7, while coliforms and enterococci were not. Few pathogens were detected: 5 salmonellae and 2 E. coli O157:H7 from 260 samples, of which only one was lettuce and the others were manure, soil and water. Most (5/7) pathogens were isolated from the same farm and all were from organic production. Statistical analysis revealed the following environmental and agro-technical risk factors for increased microbial load and pathogen prevalence in lettuce production: high temperature, flooding of lettuce fields, application of contaminated organic fertilizer, irrigation with water of inferior quality and large distances between the field and toilets. Control of the composting process of organic fertilizers and the irrigation water quality appear most crucial to improve and/or maintain the microbiological quality and safety during the primary production of lettuce. PMID:24829142

Ceuppens, Siele; Hessel, Claudia Titze; de Quadros Rodrigues, Rochele; Bartz, Sabrina; Tondo, Eduardo César; Uyttendaele, Mieke

2014-07-01

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NITRATE AND SODIUM CONTAMINATION IN PERCOLATED WATER AND LEAF TISSUE IN LETTUCE CROP IRRIGATED WITH DOMESTIC SEWAGE WATER = CONTAMINAÇÃO POR NITRATO E SÓDIO DA ÁGUA PERCOLADA E DA PLANTA DE ALFACE IRRIGADA COM ÁGUA RESIDUÁRIA  

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Full Text Available With the objective of characterizing and simulating the contamination of the percolated water in the soil, were analyzed lettuce crops fertilized with organic and mineral compounds and irrigated along furrows with residual water contaminated by total and fecal coliforms that originated from the dilution of domestic sewers with treated water. The experiment was conducted using thirty 500L amianthus boxes with a surface area of 1 m2 per box filled with sifted soil with a bottom layer of broken stones, 10cm thick. Three lettuce crops were used. The incorporation of organic and mineral fertilizers occurred during the first and third crops. Four irrigation furrows were used, which resulted in five rows of planted lettuce. Collectors of percolated water were made using ½ inch plastic tubes, sawed length-wise and covered with a sieve, and were installed at depths of 15 and 30 cm. A water collector was placed at 60cm depth of at the bottom of the boxes, and remained closed except for when collecting the two water samples taken during each crop cycle: 15 days after plantingthe lettuce seedlings and right before harvesting the lettuce. Chemical, physical and bacteriological analyses of the water collected at depth were carried out. The average concentration of nitrate and sodium in the three crops is indicative that feathers ofcontamination move slowly at depth in agricultural soils and in areas of organic and inorganic residue deposition. The microbial analyses of the water collected from the lower layer at a depth of 60 cm did not show contamination from fecal coliforms. = O trabalho foi desenvolvido no Centro de Estudos Ambientais/UNESP (CEA, em ambiente protegido, com o objetivo de se estudar os efeitos da fertilizaçãoorgânica, da fertilização mineral e da irrigação por sulcos, com água tratada e servida, em cultura da alface (Lactuca sativa L., observando-se a presença de nitrato (NO3- e sódio (Na+ no tecido foliar e bactérias coliformes totais (CT e coliformes fecais (CFna água percolada. As parcelas experimentais distribuídas em um delineamento experimental em blocos casualizados, constituíram-se de 30 caixas de amianto com volume de 500 L e área superficial de 1 m2 , preenchidas com solo previamente peneirado. Os tratamentos caracterizaram-se pela associação entre fertilizantes e água contaminada e tratada. Três cultivos de alface foram realizados. Coletores de água foram instalados a 15, 30 e 60 cm de profundidade. Duas coletas de água foram realizadas em cada cultivo, 15 dias após o transplante e uma na colheita, para verificar a presença de NO3-, Na+, CT e CF. Ao término de cada cultivo realizaram-se amostragens de tecido vegetal das folhas para análises químicas. As concentrações médias de NO3- e Na+ na solução percolada foram indicadoras de que plumas de contaminação avançaram lentamente em profundidade nos solos estudados. As análises de CF da água realizadas a 60 cm de profundidade não apresentaram contaminação. O tratamento fertilizado com cama de frango apresentou os maiores valores de NO3-.

João Antonio Galbiatti

2004-01-01

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Aplicação de doses de CO2 via água de irrigação na cultura da alface / Application of doses of CO2 by means of irrigation water for lettuce  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A concentração de CO2 na atmosfera vem aumentado significativamente desde a revolução industrial, estando hoje próximo de 365 mmol mol-1, com tendência de aumento. Este trabalho teve como objetivo estudar a influência de doses crescentes de CO2 via água de irrigação por gotejamento sobre o crescimen [...] to, o desenvolvimento, a fotossíntese e a produtividade da alface cultivar Elisa, bem como seus efeitos sobre a condutividade elétrica. O experimento foi conduzido sob túneis plásticos, em delineamento experimental inteiramente casualizado. Os tratamentos foram compostos por doses de CO2: 0 (testemunha), 52; 155 e 310 kg ha-1, aplicadas via água de irrigação. As irrigações foram realizadas diariamente com base na evaporação do tanque classe A, corrigida pelo coeficiente da cultura e do tanque. O número de folhas e a matéria seca da parte aérea da planta foram influenciados pela aplicação de CO2 via água de irrigação, não ocorrendo o mesmo para matéria fresca e índice de área foliar. Os resultados indicaram a dose mensal de 153 kg ha-1 de CO2 como a mais adequada para ser empregada na cultura da alface via água de irrigação, com um aumento de aproximadamente 20,5% de produtividade, quando comparado à testemunha. Abstract in english Carbon dioxide concentration in the atmosphere has been increasing since the industrial revolution. Nowadays it is approximately 365 mmol mol-1, with a tendency to increase. The effect of CO2 dosis, supplied by drip irrigation on lettuce development, plants growth, photosynthesis and productivity, a [...] nd also the effects on electrical conductivity were evaluated. The experiment was conduced under plastic tunnels in a completely randomized block design. The treatments included CO2 rates: 0 (control), 52; 155 and 310 kg ha-1. Water was delivered daily to plants in order to replace lost volumes by evapotranspiration, based on estimates from class A evaporation pan, corrected by the crop and tank coefficients (Kc and Kp, respectively). The CO2 use, via irrigation water, changed the leaves number and the shoot dry weight, but not the leaf area index and the fresh dry weight. The monthly use of 153 kg ha-1 of CO2, via irrigation water, is proper for lettuce since it increased the productivity in 20.5% when compared to the control.

Gomes, Tamara Maria; Modolo, Valéria A.; Botrel, Tarlei A.; Oliveira, Ricardo F. de.

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Dual application of duckweed and azolla plants for wastewater treatment and renewable fuels and petrochemicals production  

Science.gov (United States)

Background Shortages in fresh water supplies today affects more than 1 billion people worldwide. Phytoremediation strategies, based on the abilities of aquatic plants to recycle nutrients offer an attractive solution for the bioremediation of water pollution and represents one of the most globally researched issues. The subsequent application of the biomass from the remediation for the production of fuels and petrochemicals offers an ecologically friendly and cost-effective solution for water pollution problems and production of value-added products. Results In this paper, the feasibility of the dual application of duckweed and azolla aquatic plants for wastewater treatment and production of renewable fuels and petrochemicals is explored. The differences in absorption rates of the key wastewater nutrients, ammonium and phosphorus by these aquatic macrophytes were used as the basis for optimization of the composition of wastewater effluents. Analysis of pyrolysis products showed that azolla and algae produce a similar range of bio-oils that contain a large spectrum of petrochemicals including straight-chain C10-C21 alkanes, which can be directly used as diesel fuel supplement, or a glycerin-free component of biodiesel. Pyrolysis of duckweed produces a different range of bio-oil components that can potentially be used for the production of “green” gasoline and diesel fuel using existing techniques, such as catalytic hydrodeoxygenation. Conclusions Differences in absorption rates of the key wastewater nutrients, ammonium and phosphorus by different aquatic macrophytes can be used for optimization of composition of wastewater effluents. The generated data suggest that the composition of the petrochemicals can be modified in a targeted fashion, not only by using different species, but also by changing the source plants’ metabolic profile, by exposing them to different abiotic or biotic stresses. This study presents an attractive, ecologically friendly and cost-effective solution for efficient bio-filtration of swine wastewater and petrochemicals production from generated biomass.

2014-01-01

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Integrated analysis for a carbon- and water-constrained future: an assessment of drip irrigation in a lettuce production system in eastern Australia.  

Science.gov (United States)

The Australian Government is meeting the challenge of water scarcity and climate change through significant on-farm infrastructure investment to increase water use efficiency and productivity, and secure longer term water supplies. However, it is likely that on-farm infrastructure investment will alter energy consumption and therefore generate considerable greenhouse gas (GHG) emissions, suggesting potential conflicts in terms of mitigation and adaptation policies. In particular, the introduction of a price on carbon may influence the extent to which new irrigation technologies are adopted. This study evaluated trade-offs between water savings, GHG emissions and economic gain associated with the conversion of a sprinkler (hand shift) irrigation system to a drip (trickle) irrigation system for a lettuce production system in the Lockyer Valley, one of the major vegetable producing regions in Australia. Surprisingly, instead of trade-offs, this study found positive synergies - a win-win situation. The conversion of the old hand-shift sprinkler irrigation system to a drip irrigation system resulted in significant water savings of almost 2 ML/ha, as well as an overall reduction in GHG emissions. Economic modelling, at a carbon price of $ 30/t CO(2)e, indicated that there was a net benefit of adoption of the drip irrigation system of about $ 4620/ML/year. We suggest priority should be given, in the implementation of on-farm infrastructure investment policy, to replacing older inefficient and energy-intensive sprinkler irrigation systems such as hand shift and roll-line. The findings of the study support the use of an integrated approach to avoid possible conflicts in designing national climate change mitigation and adaptation policies, both of which are being developed in Australia. PMID:22935628

Maraseni, T N; Mushtaq, S; Reardon-Smith, K

2012-11-30

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Desempenho de cultivares de alface submetidas a diferentes níveis de salinidade da água de irrigação / Performance of lettuce cultivars under different salinity levels of irrigation water  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Este trabalho foi desenvolvido em ambiente protegido objetivando avaliar o desempenho de cultivares de alface em condições de salinidade. O delineamento utilizado foi inteiramente casualizado, e os tratamentos foram distribuídos em esquema fatorial 5 x 5, com cinco cultivares de alface (Mônica SF31, [...] Grandes Lagos 659, Veneranda, Folha Roxa Quatro Estações e Stella) e cinco níveis de salinidade de água (0,5; 1,5; 2,5; 3,5 e 4,5 dS m-1) e três repetições. As plantas foram colhidas aos 35 dias após o transplantio e avaliados as principais características morfofisiológicas de crescimento: número de folhas, área foliar, comprimento do caule, massa fresca e massa seca das plantas. Verificou-se efeito significativo dos fatores isolados e da interação, para todas as características de crescimento. O maior desempenho foi obtido na cultivar Folha Roxa Quatro Estações. O número de folhas, a área foliar e a fitomassa da parte aérea, foram reduzidos linearmente com o aumento da salinidade, sendo os maiores valores obtidos nas cultivares Folha Roxa Quatro Estações e Stella. Abstract in english This study was carried out in greenhouse to evaluate the performance of different cultivars of lettuce under saline conditions. The experimental design was a completely randomized in factorial scheme, with five cultivars of lettuce (Mônica SF31, Grandes Lagos 659, Veneranda, Folha Roxa Quatro Estaçõ [...] es e Stella) and five levels of water salinity (0.5 , 1.5, 2.5, 3.5 and 4.5 dS m-1) and three replications. The plants were harvested at 35 days after transplanting and the main morphophysiological growth parameters, that is, the number of leaves, leaf area, stem length, fresh weight and dry weight of plants were evaluated. Significant effect of the isolated factors and of the interaction for all parameters was found. The best performance was obtained in cultivar Folha Roxa Quatro Estações. The number of leaves, leaf area and biomass of shoots were reduced linearly with increasing salinity, with higher values in cultivars Folha Roxa Quatro Estações and Stella.

Oliveira, Francisco de A. de; Carrilho, Maria J. S. de O.; Medeiros, José F. de; Maracajá, Patrício B.; Oliveira, Mychelle K. T. de.

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EFEITO DO CLORO NA ÁGUA DE LAVAGEM PARA DESINFECÇÃO DE ALFACE MINIMAMENTE PROCESSADA EFFECT OF CHLORINE IN THE WASHING WATER FOR DESINFECTION OF MINIMALLY PROCESSED LETTUCE  

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Full Text Available Este trabalho de pesquisa foi desenvolvido com o objetivo de verificar a eficácia de diferentes concentrações de cloro utilizadas como agente sanitizante na água de lavagem de alface(Lactuca sativa L., do tipo americana, minimamente processada. Na matéria-prima foram realizadas contagens de bolores, leveduras e coliformes totais. No produto final foram realizadas contagens de bolores e leveduras, coliformes totais e avaliação sensorial. O processamento mínimo da alface compreendeu as seguintes etapas: corte do talo, desfolhamento da cabeça, primeira seleção, primeira lavagem, segunda seleção, corte em tiras, segunda lavagem, tratamento de imersão em soluções contendo 70, 100 e 130mg/L de cloro, centrifugação, acondicionamento em sacos plásticos e armazenamento a 2°C e a 20°C. Os resultados mostraram que a imersão em solução contendo 70mg/L de cloro confere a alface minimamente processada uma vida-útil de seis dias e em solução contendo 100 e 130mg/L, nove dias e que o seu aroma, textura e gosto não foram afetados por estes tratamentos.This research was carried out aiming at evaluating the efficacy of different concentrations of chlorine used as a sanitizer in the washing water of minimally processed lettuce (Lactuca sativa L.. Total coliform and mould and yeast counts were performed on the raw material. The same microbiological exams plus a sensory evaluation were performed on the final product. The minimal processing of the lettuce consisted of cutting, shredding, first selection of leaves, first washing, second selection, manual slicing, second washing, dipping in solutions of 70,100 and 130mg/L of chlorine, spin drying, packaging in polyethylene bags and storage at 2(0C and at 20(0C.The results showed that the chlorine solution containing 70mg/L promoted a shelf-life of 6 days under refrigeration, and the 100 and 130mg/L solutions, 9 days. The sensory characteristics such as texture and flavor were not affected by the treatments studied.

Shirley Aparecida Garcia BERBARI

2001-08-01

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Evaluation of the oil Produced from lettuce crop cultivated under three irrigation conditions  

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Three oil lettuce seed samples (lactuca Sativa LS10, LS20, LS30) were cultivated under three irrigation conditions (well, normal and water deficient conditions, after 10, 20 and 30 days respectively) to evaluate their oils and to see to what extent the oil lettuce plant resists draught conditions. The oils extracted from the three seed samples were evaluated by determining eight lipid profiles using HPLC in conjunction with capillary GLC. Lettuce seed oils are characterized...

Hassan El-mallah, M.; El-shami, S. M.

2012-01-01

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Moderate and high doses of sodium hypochlorite, neutral electrolyzed oxidizing water, peroxyacetic acid, and gaseous chlorine dioxide did not affect the nutritional and sensory qualities of fresh-cut Iceberg lettuce (Lactuca sativa Var. capitata L.) after washing.  

Science.gov (United States)

Besides the traditionally used sodium hypochlorite (20 and 200 mg L(-1)), alternative sanitizers such as peroxyacetic acid (80 and 250 mg L(-1)) and neutral electrolyzed oxidizing water (4.5 and 30 mg L(-1) free chlorine) as well as chlorine dioxide gas (1.54 mg L(-1)) were evaluated for their efficiency in reducing the microbial load of fresh-cut iceberg lettuce. An additional rinsing step with tap water and cooling of the sanitizing solutions, which are obvious for the fresh-cut industry, were not performed within the current study. The high doses of sodium hypochlorite and peroxyacetic acid tested within this study do not conform to the normally used concentrations within the fresh-cut industry. Neutral electrolyzed oxidizing water (30 mg L(-1)), peroxyacetic acid (250 mg L(-1)), and gaseous chlorine dioxide significantly reduced the total aerobic plate count of cut lettuce in comparison with water wash treatments alone. None of the treatments significantly affected the sensory quality of the lettuce, although small color changes were observed after colorimetric measurements. From a nutritional point of view water rinsing significantly decreased the vitamin C (maximum 35%) and phenol (maximum 17%) contents, but did not affect the carotenoid and ?-tocopherol contents. Additional effects caused by adding a sanitizer to the wash water were not observed for vitamin C and phenols. Conversely, washing with 250 mg L(-1) peroxyacetic acid reduced the ?-carotene content by about 30%, whereas using 200 mg L(-1) sodium hypochlorite reduced both the lactucaxanthin and the lutein contents by about 60%. Use of gaseous chlorine dioxide also had an impact on the lutein content (-18%). Furthermore, the ?-tocopherol content was reduced by 19.7 and 15.4% when the two concentrations of neutral electrolyzed oxidizing water were used, respectively. These data represent the situation on day 0. In a next phase, shelf-life studies considering microbial and sensory quality and nutrient content should be conducted. PMID:19371140

Vandekinderen, Isabelle; Van Camp, John; De Meulenaer, Bruno; Veramme, Kim; Bernaert, Nathalie; Denon, Quenten; Ragaert, Peter; Devlieghere, Frank

2009-05-27

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Controlled Atmosphere Storage of Lettuce.  

Science.gov (United States)

Studies were conducted on the effect of controlled atmosphere storage as well as chemical pretreatments on the quality of lettuce as well as biochemical composition of lettuce leaves, Lactuca sativa L., cultivar 'Great Lakes.' In a CA of 2.5% CO2 and 2.5%...

B. Singh C. C. Yang D. J. Wang D. K. Salunkhe

1971-01-01

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Microflora of partially processed lettuce.  

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Bacteria, yeasts, and molds isolated from partially processed iceberg lettuce were taxonomically classified. The majority of bacterial isolates were gram-negative rods. Pseudomonas, Erwinia, and Serratia species were commonly found. Yeasts most frequently isolated from lettuce included members of the genera Candida, Cryptococcus, Pichia, Torulaspora, and Trichosporon. Comparatively few molds were isolated; members of the genera Rhizopus, Cladosporium, Phoma, Aspergillus, and Penicillium were ...

Magnuson, J. A.; King, A. D.; To?ro?k, T.

1990-01-01

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Vertical Pricing Relationships for Lettuce.  

Science.gov (United States)

The study examines weekly lettuce prices between 1986 and 1991 in 12 U.S. cities to see how quickly and completely price changes were transmitted from the shipping point to the wholesalers and then to the retailers. Wholesale iceberg lettuce prices, for e...

N. J. Powers

1994-01-01

 
 
 
 
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The logistic growth of duckweed (Lemna minor) and kinetics of ammonium uptake.  

Science.gov (United States)

Mathematical models have been developed to describe nitrogen uptake and duckweed growth experimentally to study the kinetics of ammonium uptake under various concentrations. The kinetics of duckweed ammonium uptake was investigated using the modified depletion method after plants were grown for two weeks at different ammonium concentrations (0.5-14 mg/L) in the culture medium. The maximum uptake rate and Michaelis-Menten constant for ammonium were estimated as 0.082 mg/(g fresh weight x h) and 1.877 mg/L, respectively. Duckweed growth was assessed when supplied at different total nitrogen (TN) concentrations (1-5 mg/L) in the culture medium. The results showed that the intrinsic growth rate was from 0.22 to 0.26 d(-1), and TN concentrations had no significant influence on the duckweed growth rate. PMID:24645435

Zhang, Kun; Chen, You-Peng; Zhang, Ting-Ting; Zhao, Yun; Shen, Yu; Huang, Lei; Gao, Xu; Guo, Jin-Song

2014-01-01

62

Qualidade química da água residual da criação de peixes para cultivo de alface em hidroponia / Chemical quality of residual water from fish breeding tanks for cultivation of hydroponic lettuce  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Com o objetivo de avaliar a associação do cultivo de alface em hidroponia com utilização dos resíduos do sistema de criação intensiva de peixe, desenvolveu-se um trabalho no Centro de Aqüicultura, na FCAV-UNESP, Campus de Jaboticabal, SP. A integração foi projetada para que a água circulasse de mane [...] ira fechada entre os sistemas, passando pelos tanques de criação de peixes, por um decantador, para remoção dos resíduos por um reservatório para conversão biológica da amônia em nitrato e pelo sistema hidropônico, retornando aos tanques de criação dos peixes. Foram avaliadas três cultivares de alface, que constituíram os tratamentos com quatro repetições. Os resultados da análise química da água residual da criação indicaram a presença da maioria dos nutrientes minerais necessários ao desenvolvimento vegetal, em concentração próxima aos valores encontrados em soluções nutritivas utilizadas para o cultivo da alface em hidroponia, exceto potássio e magnésio. A baixa concentração de magnésio na água não impediu o desenvolvimento da alface; entretanto, as plantas indicaram sintomas visuais de deficiência deste nutriente. Não houve diferenças entre as cultivares quanto à produtividade e ao peso fresco de plantas. Abstract in english Aiming to evaluate the association of hydroponic lettuce cultivation with residues from a fish intensive breeding system, a project was carried out in the Aquaculture Center in the FCAV-UNESP at Jaboticabal, SP, Brazil. A closed system was designed in order to allow the water to circulate through th [...] e fish tanks, a clarifier tank for removal of residues, a reservoir for biological conversion of ammonia into nitrate, and the hydroponic system. After this process, water returned back to the fish tanks. Three varieties of lettuce, constituting the treatments with four repetitions were evaluated. The results of the chemical analysis of the residual water from the fish tanks indicated the presence of the majority of the mineral nutrients necessary for vegetable development. Their concentration was close to that found in nutrient solutions, used for lettuce hydroponic cultivation, except for potassium and magnesium. The low concentration of magnesium in the water did not prevent lettuce development, although the plants presented visual symptoms of deficiency of this nutrient. Differences were not found between the varieties produced, regarding productivity and the mean weight of fresh plants.

Glauco E. P., Cortez; Jairo A. C. de, Araújo; Paulo A., Bellingieri; Alexandre B., Dalri.

63

Qualidade química da água residual da criação de peixes para cultivo de alface em hidroponia Chemical quality of residual water from fish breeding tanks for cultivation of hydroponic lettuce  

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Full Text Available Com o objetivo de avaliar a associação do cultivo de alface em hidroponia com utilização dos resíduos do sistema de criação intensiva de peixe, desenvolveu-se um trabalho no Centro de Aqüicultura, na FCAV-UNESP, Campus de Jaboticabal, SP. A integração foi projetada para que a água circulasse de maneira fechada entre os sistemas, passando pelos tanques de criação de peixes, por um decantador, para remo??ão dos resíduos por um reservatório para conversão biológica da amônia em nitrato e pelo sistema hidropônico, retornando aos tanques de criação dos peixes. Foram avaliadas três cultivares de alface, que constituíram os tratamentos com quatro repetições. Os resultados da análise química da água residual da criação indicaram a presença da maioria dos nutrientes minerais necessários ao desenvolvimento vegetal, em concentração próxima aos valores encontrados em soluções nutritivas utilizadas para o cultivo da alface em hidroponia, exceto potássio e magnésio. A baixa concentração de magnésio na água não impediu o desenvolvimento da alface; entretanto, as plantas indicaram sintomas visuais de deficiência deste nutriente. Não houve diferenças entre as cultivares quanto à produtividade e ao peso fresco de plantas.Aiming to evaluate the association of hydroponic lettuce cultivation with residues from a fish intensive breeding system, a project was carried out in the Aquaculture Center in the FCAV-UNESP at Jaboticabal, SP, Brazil. A closed system was designed in order to allow the water to circulate through the fish tanks, a clarifier tank for removal of residues, a reservoir for biological conversion of ammonia into nitrate, and the hydroponic system. After this process, water returned back to the fish tanks. Three varieties of lettuce, constituting the treatments with four repetitions were evaluated. The results of the chemical analysis of the residual water from the fish tanks indicated the presence of the majority of the mineral nutrients necessary for vegetable development. Their concentration was close to that found in nutrient solutions, used for lettuce hydroponic cultivation, except for potassium and magnesium. The low concentration of magnesium in the water did not prevent lettuce development, although the plants presented visual symptoms of deficiency of this nutrient. Differences were not found between the varieties produced, regarding productivity and the mean weight of fresh plants.

Glauco E. P. Cortez

2009-08-01

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Water use and crop coefficient of subsurface drip-irrigated lettuce in Central Arizona Demanda hídrica e coeficiente de cultura da alface irrigada por gotejamento sub-superficial na região central do Arizona  

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A two year field study (1996/97 and 1997/98 growing seasons) was carried out at the Maricopa Agricultural Center (33º04'07" N; 111º57'18" W) of the University of Arizona, USA, to investigate the water use and to derive Kc's for subsurface drip-irrigated head lettuce grown in small weighable lysimeters. Measurement periods ranged from 480 to 1100 ºC-day (96/97) and from 439 to 1098 ºC-day (97/98). These intervals corresponded essentially to the second half of the crop cycle which amounted ...

Oliveira, Aureo S.; Martin, Edward C.; Slack, Donald C.; Pegelow, Edward J.; Folta, Allen D.

2005-01-01

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Improving Production of Bioethanol from Duckweed (Landoltia punctata) by Pectinase Pretreatment  

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Landoltia punctata, a widely distributed duckweed strain with the ability to accumulate starch, was used as a novel feedstock for bioethanol production by Saccharomyces cerevisiae. To improve ethanol production, pectinase pretreatment was used to release much more glucose from L. punctata mash and the pretreatment conditions (enzyme loading, temperature and pretreatment time) for the duckweed were optimized by using a surface resp...

Qian Chen; Yanling Jin; Guohua Zhang; Yang Fang; Yao Xiao; Hai Zhao

2012-01-01

66

Nitrogen transformations and removal mechanisms in algal and duckweed stabilisation ponds  

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This thesis describes the results of a comparative study of the performance of algae-based ponds (ABPs) and duckweed-based ponds (DBPs) for wastewater treatment, with emphasis on nitrogen transformations and removal mechanisms.Batch experiments simulating algae and duckweed ( Lemna gibba ) stabilisation ponds for domestic wastewater treatment were conducted to quantify the importance of various nitrogen removal mechanisms under controlled conditions of pH and DO. N-removal in both systems by ...

Zimmo, O.

2003-01-01

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Produção e indicadores fisiológicos de alface sob hidroponia com água salina Production and physiologic indicators of lettuce grown in hydroponics with saline water  

Directory of Open Access Journals (Sweden)

Full Text Available O uso de água salina na produção de hortaliças constitui no momento atividade essencial, tendo em vista o aumento da demanda de água doce, tanto pela atividade agrícola quanto pelo abastecimento urbano e industrial. O objetivo do trabalho foi avaliar a produção e os indicadores fisiológicos de alface cultivada em hidroponia com a utilização de água salina. O experimento foi conduzido em ambiente protegido, em Piracicaba-SP. O delineamento experimental foi de blocos ao acaso, sendo estudados os efeitos de cinco níveis de salinidade da água de irrigação, utilizando-se NaCl [Condutividade elétrica (Cea: 0,42, 1,53, 3,52, 5,55 e 7,43 dS m-1] em duas cultivares de alface (Verônica e Pira Roxa, em esquema fatorial. Foram determinadas massa fresca e seca de folhas, caule, raízes e da parte aérea; teor de nitrato, prolina e clorofila. O aumento da salinidade da água reduziu linearmente as massas fresca e seca das folhas, caule, raízes e da parte aérea. As massas fresca e seca foram 36% e 57% superiores na cultivar Verônica, respectivamente. A cultivar Pira Roxa apresentou maior teor de nitrato 25% (3008 mg L-1, clorofila total 50% (1,46 mg g-1massa fresca e prolina, 71,43% (0,21 µM g-1massa fresca-1 em relação à Verônica, o que pode ser um mecanismo de adaptação daquela cultivar ao estresse salino. Com relação à produtividade comercial, obteve-se uma perda de 69 e 64% para as cultivares Pira Roxa e Verônica, quando se utilizou água mais salina (7,43 dS m-1. Em relação à produção de massa seca, a perda pelo uso dessa água foi de 53% e 44%, respectivamente. Os resultados obtidos em sistema de cultivo hidropônico podem indicar a possibilidade do uso da água salina como alternativa para produção de hortaliças para produtores que têm disponibilidade de água salina e restrita disponibilidade de água doce, embora com redução na produtividade.The use of saline water in the production of vegetables constitutes at the moment an essential activity, facing the rising demand of fresh water, as for the agricultural activity as for the urban and industrial supplying. This study aimed to evaluate production and physiologic indicators of lettuce in hydroponic system with the use of saline waters. The experiment was carried out in a greenhouse in the period from December 2007 to January 2008, in Piracicaba, Brazil. The experimental design was randomized blocks in factorial scheme - five salinity levels obtained with the addition of NaCl, which resulted in different water electrical conductivity levels (dS m-1: 0,42, 1,53, 3,52, 5,55, 7,43 - and two cultivars of lettuce - Veronica and Pira Roxa. It was determined the fresh and dry mass of leaves, stem, roots and shoot and the content of nitrate, proline and chlorophyll. The increase of water salinity reduced lineally the fresh and dry mass of leaves, stem, roots and shoot. The cv Verônica produced 36% and 57% more shoot fresh and dry mass, respectively, than Pira Roxa. The cv. Pira Roxa accumulated 25% more nitrate (3008 mg L-1, presented 50% more total chlorophyll (1,46 mg g-1fresh mass and 71,43% more proline (0,21 µM g fresh mass- 1 than the cv Verônica, showing a mechanism of avoiding salinity stress. Cultivars Pira Roxa and Veronica presented loss of 69% and 64% of commercial productivity, respectively, when the most saline water (7,43 dS m-1 was used. In the other hand dry matter was reduced in 53% and 44%, respectively, for cv. Pira Roxa and Verônica in the most saline water. The results obtained in this study can indicate the possibility of using saline water as an alternative for the production of vegetables, specially for growers that have saline water available but restricted fresh water, even with reduction of productivity.

Dalva Paulus

2010-03-01

68

Produção e indicadores fisiológicos de alface sob hidroponia com água salina / Production and physiologic indicators of lettuce grown in hydroponics with saline water  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O uso de água salina na produção de hortaliças constitui no momento atividade essencial, tendo em vista o aumento da demanda de água doce, tanto pela atividade agrícola quanto pelo abastecimento urbano e industrial. O objetivo do trabalho foi avaliar a produção e os indicadores fisiológicos de alfac [...] e cultivada em hidroponia com a utilização de água salina. O experimento foi conduzido em ambiente protegido, em Piracicaba-SP. O delineamento experimental foi de blocos ao acaso, sendo estudados os efeitos de cinco níveis de salinidade da água de irrigação, utilizando-se NaCl [Condutividade elétrica (Cea): 0,42, 1,53, 3,52, 5,55 e 7,43 dS m-1] em duas cultivares de alface (Verônica e Pira Roxa), em esquema fatorial. Foram determinadas massa fresca e seca de folhas, caule, raízes e da parte aérea; teor de nitrato, prolina e clorofila. O aumento da salinidade da água reduziu linearmente as massas fresca e seca das folhas, caule, raízes e da parte aérea. As massas fresca e seca foram 36% e 57% superiores na cultivar Verônica, respectivamente. A cultivar Pira Roxa apresentou maior teor de nitrato 25% (3008 mg L-1), clorofila total 50% (1,46 mg g-1massa fresca) e prolina, 71,43% (0,21 µM g-1massa fresca-1) em relação à Verônica, o que pode ser um mecanismo de adaptação daquela cultivar ao estresse salino. Com relação à produtividade comercial, obteve-se uma perda de 69 e 64% para as cultivares Pira Roxa e Verônica, quando se utilizou água mais salina (7,43 dS m-1). Em relação à produção de massa seca, a perda pelo uso dessa água foi de 53% e 44%, respectivamente. Os resultados obtidos em sistema de cultivo hidropônico podem indicar a possibilidade do uso da água salina como alternativa para produção de hortaliças para produtores que têm disponibilidade de água salina e restrita disponibilidade de água doce, embora com redução na produtividade. Abstract in english The use of saline water in the production of vegetables constitutes at the moment an essential activity, facing the rising demand of fresh water, as for the agricultural activity as for the urban and industrial supplying. This study aimed to evaluate production and physiologic indicators of lettuce [...] in hydroponic system with the use of saline waters. The experiment was carried out in a greenhouse in the period from December 2007 to January 2008, in Piracicaba, Brazil. The experimental design was randomized blocks in factorial scheme - five salinity levels obtained with the addition of NaCl, which resulted in different water electrical conductivity levels (dS m-1): 0,42, 1,53, 3,52, 5,55, 7,43 - and two cultivars of lettuce - Veronica and Pira Roxa. It was determined the fresh and dry mass of leaves, stem, roots and shoot and the content of nitrate, proline and chlorophyll. The increase of water salinity reduced lineally the fresh and dry mass of leaves, stem, roots and shoot. The cv Verônica produced 36% and 57% more shoot fresh and dry mass, respectively, than Pira Roxa. The cv. Pira Roxa accumulated 25% more nitrate (3008 mg L-1), presented 50% more total chlorophyll (1,46 mg g-1fresh mass) and 71,43% more proline (0,21 µM g fresh mass- 1) than the cv Verônica, showing a mechanism of avoiding salinity stress. Cultivars Pira Roxa and Veronica presented loss of 69% and 64% of commercial productivity, respectively, when the most saline water (7,43 dS m-1) was used. In the other hand dry matter was reduced in 53% and 44%, respectively, for cv. Pira Roxa and Verônica in the most saline water. The results obtained in this study can indicate the possibility of using saline water as an alternative for the production of vegetables, specially for growers that have saline water available but restricted fresh water, even with reduction of productivity.

Dalva, Paulus; Durval, Dourado Neto; José Antônio, Frizzone; Tales M, Soares.

69

Browning control of fresh-cut lettuce by phytoncide treatment.  

Science.gov (United States)

Phytoncide essential oil derived from pine leaves was applied for the control of enzymatic browning of fresh-cut lettuce. Changes in the browning characteristics of cut lettuce treated with phytoncide in an water or ethanol solution (1%, v/v) at 10°C were investigated for 12days at 4°C. Other samples dipped in distilled water or 95% ethanol were used as the controls. The samples treated with phytoncide in an ethanol solution showed significantly higher L(*) values and lower a(*) values, ?E values, browning index, phenolic compounds, and enzyme activities (PPO, POD, PAL) related to browning. The samples dipped in distilled water showed the opposite tendency. On the basis of changes in the browning characteristics, anti-browning effects of each treatment, phytoncide in an ethanol solution was the most effective treatment applied. These results suggest that phytoncide treatment could be used as an effective method for controlling enzymatic browning in fresh-cut lettuce. PMID:24767043

Kim, Do-Hee; Kim, Han-Bit; Chung, Hun-Sik; Moon, Kwang-Deog

2014-09-15

70

Modification of chromate toxicity by sulphate in duckweeds (Lemnaceae).  

Science.gov (United States)

Two duckweed species, Spirodela polyrhiza and Lemna minor, were used to measure the toxicity of chromate (100 microM) at three levels of sulphate (13 microM, low sulphate=LS; 410 microM, normal sulphate=NS; 10,000 microM, high sulphate=HS). Growth rates calculated on the basis of dry weight, chlorophyll and carotenoid content were all reduced by chromate. This inhibition was the strongest under LS conditions and the weakest under HS conditions. Thus, sulphate decreases chromate toxicity-which conforms with its influence on chromate uptake reported previously (Kaszycki, P., Gabrys, H., Appenroth, K.-J., Jaglarz, A., Sedziwy, S., Walczak, T., Koloczek, H., 2005. Exogenously applied sulphate as a tool to investigate transport and reduction of chromate in the duckweed Spirodela polyrhiza. Plant Cell Environ. 28, 260-269). The three levels of sulphate were also applied during pre-cultivation of both species for 2 weeks and the consequences for chromate toxicity were tested thereafter. When S. polyrhiza was pre-cultivated in NS medium, the growth inhibition by chromate was approximately 80% of the control (no chromate) in the subsequently applied LS medium, and approximately 50% in HS. L. minor showed similar relationships but a lower overall chromate sensitivity. In comparison to the plants pre-treated in NS medium, those pre-treated in LS were more sensitive whereas those pre-treated in HS were less sensitive toward chromate. The present data demonstrate that chromate is taken up into cells of the two duckweed species by sulphate transporter(s). The rather weak influence of sulphate on chromate toxicity indicates that chromate binds to the transporters much stronger than sulphate. Moreover, the relative effects of sulphate on the chromate toxicity remain very similar regardless of pre-treatment. This confirms the conclusion from uptake experiments that pre-treatment with different levels of sulphate changes the number of sulphate transporters but their affinity remains unchanged. In summary, the influence of sulphate on the toxicity of chromate reflects mainly its influence on chromate uptake, with a negligible impact of other physiological processes. PMID:18675470

Appenroth, Klaus-J; Luther, Alexandra; Jetschke, Gottfried; Gabrys, Halina

2008-09-17

71

Impact of phytopathogen infection and extreme weather stress on internalization of Salmonella Typhimurium in lettuce.  

Science.gov (United States)

Internalization of human pathogens, common in many types of fresh produce, is a threat to human health since the internalized pathogens cannot be fully inactivated/removed by washing with water or sanitizers. Given that pathogen internalization can be affected by many environmental factors, this study was conducted to investigate the influence of two types of plant stress on the internalization of Salmonella Typhimurium in iceberg lettuce during pre-harvest. The stresses were: abiotic (water stress induced by extreme weather events) and biotic (phytopathogen infection by lettuce mosaic virus [LMV]). Lettuce with and without LMV infection were purposefully contaminated with green fluorescence protein-labeled S. Typhimurium on the leaf surfaces. Lettuce was also subjected to water stress conditions (drought and storm) which were simulated by irrigating with different amounts of water. The internalized S. Typhimurium in the different parts of the lettuce were quantified by plate count and real-time quantitative PCR and confirmed with a laser scanning confocal microscope. Salmonella internalization occurred under the conditions outlined above; however internalization levels were not significantly affected by water stress alone. In contrast, the extent of culturable S. Typhimurium internalized in the leafy part of the lettuce decreased when infected with LMV under water stress conditions and contaminated with high levels of S. Typhimurium. On the other hand, LMV-infected lettuce showed a significant increase in the levels of culturable bacteria in the roots. In conclusion, internalization was observed under all experimental conditions when the lettuce surface was contaminated with S. Typhimurium. However, the extent of internalization was only affected by water stress when lettuce was infected with LMV. PMID:24220663

Ge, Chongtao; Lee, Cheonghoon; Nangle, Ed; Li, Jianrong; Gardner, David; Kleinhenz, Matthew; Lee, Jiyoung

2014-01-01

72

Biological Removal of Chlorinated Hydrocarbons from Water.  

Science.gov (United States)

With the hope of finding an inexpensive and simple solution to the problem of cleanup of contaminated water, the project investigated the role of freshwater plants in wastewater treatment. The use of duckweeds (lemnaceae) to remove phenol and 2-chlorophen...

P. H. Templet M. Valez

1985-01-01

73

Effects of homeopathic arsenicum album, nosode, and gibberellic acid preparations on the growth rate of arsenic-impaired duckweed (Lemna gibba L.).  

Science.gov (United States)

This study evaluated the effects of homeopathically potentized Arsenicum album, nosode, and gibberellic acid in a bioassay with arsenic-stressed duckweed (Lemna gibba L.). The test substances were applied in nine potency levels (17x, 18x, 21x-24x, 28x, 30x, 33x) and compared with controls (unsuccussed and succussed water) regarding their influence on the plant's growth rate. Duckweed was stressed with arsenic(V) for 48 h. Afterwards, plants grew in either potentized substances or water controls for 6 days. Growth rates of frond (leaf) area and frond number were determined with a computerized image analysis system for different time intervals (days 0-2, 2-6, 0-6). Five independent experiments were evaluated for each test substance. Additionally, five water control experiments were analyzed to investigate the stability of the experimental setup (systematic negative control experiments). All experiments were randomized and blinded. The test system exhibited a low coefficient of variation (approximately equal to 1%). Unsuccussed and succussed water did not result in any significant differences in duckweed growth rate. Data from the control and treatment groups were pooled to increase statistical power. Growth rates for days 0-2 were not influenced by any homeopathic preparation. Growth rates for days 2-6 increased after application of potentized Arsenicum album regarding both frond area (p positive results can be excluded with high certainty. To conclude, the test system with L. gibba impaired by arsenic(V) was stable and reliable. It yielded evidence for specific effects of homeopathic Arsenicum album preparations and it will provide a valuable tool for future experiments that aim at revealing the mode of action of homeopathic preparations. It may also be useful to investigate the influence of external factors (e.g., heat, electromagnetic radiation) on the effects of homeopathic preparations. PMID:21057725

Jäger, Tim; Scherr, Claudia; Simon, Meinhard; Heusser, Peter; Baumgartner, Stephan

2010-01-01

74

Efeito de velocidades de rebaixamento do nível freático em diferentes períodos de desenvolvimento da cultura da alface Effect of water table drawdown velocities in different stages of lettuce crop  

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Full Text Available Através deste trabalho objetivou-se determinar os efeitos do encharcamento do solo nas variáveis fenológicas e na produtividade da cultura da alface, identificar o estádio fenológico em que ocorre a maior diminuição da produtividade e obter uma relação entre a produtividade relativa da cultura e o índice diário de estresse. O delineamento experimental adotado foi inteiramente casualizado, arranjado em esquema fatorial [(3x4+1], com 3 repetições. Os tratamentos consistiram do período de inundação (12, 22 e 32 DAT, de velocidades de rebaixamento do nível freático (30 cm em 24, 48, 72 e 96 horas e uma testemunha, na qual não foi aplicado estresse por elevação do lençol freático. A alface apresentou-se como cultura sensível ao encharcamento; entretanto, não foi possível se definir um valor para o coeficiente de drenagem pois, mesmo com a maior velocidade de rebaixamento testada, ocorreu decréscimo de cerca de 50% da produção. Dentre os três períodos nos quais o estresse causado pela elevação do nível freático foi aplicado, o primeiro foi o que ocasionou maiores perdas. A produtividade das plantas de alface apresentou correlação linear negativa com o índice diário de estresse (IDS.The work had the objectives of determining the effect of water table drawdown velocities on the growth and yield of lettuce crop in a flooded soil, identifying the stage of the crop cycle with the highest reduction in the productivity and obtaining a relation between the crop relative productivity and the daily stress index. The statistical experimental design was completely randomized in factorial scheme [(3 x 4 + 1], with three replications. The water table was lowered at 3 stages of the crop cycle (12, 22 and 32 days after the transplanting, four drawdown velocities (30 cm during 24, 48, 72 and 96 h and a 13 treatment in which stress was not applied with the elevation of the water table. The lettuce presented as a sensible crop to the water-logging, although, it was not possible to define a value for the drainage coefficient because the highest drawdown velocity tested presented 50% of loss in the yield. Among the three crop stages in witch the stress caused by the water table elevation was applied, the first one caused the highest loss in the yield. The relative yield of lettuce plant had a negative linear relation with the daily stress index.

Rafael Mingoti

2006-03-01

75

Efeito de velocidades de rebaixamento do nível freático em diferentes períodos de desenvolvimento da cultura da alface / Effect of water table drawdown velocities in different stages of lettuce crop  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Através deste trabalho objetivou-se determinar os efeitos do encharcamento do solo nas variáveis fenológicas e na produtividade da cultura da alface, identificar o estádio fenológico em que ocorre a maior diminuição da produtividade e obter uma relação entre a produtividade relativa da cultura e o í [...] ndice diário de estresse. O delineamento experimental adotado foi inteiramente casualizado, arranjado em esquema fatorial [(3x4)+1], com 3 repetições. Os tratamentos consistiram do período de inundação (12, 22 e 32 DAT), de velocidades de rebaixamento do nível freático (30 cm em 24, 48, 72 e 96 horas) e uma testemunha, na qual não foi aplicado estresse por elevação do lençol freático. A alface apresentou-se como cultura sensível ao encharcamento; entretanto, não foi possível se definir um valor para o coeficiente de drenagem pois, mesmo com a maior velocidade de rebaixamento testada, ocorreu decréscimo de cerca de 50% da produção. Dentre os três períodos nos quais o estresse causado pela elevação do nível freático foi aplicado, o primeiro foi o que ocasionou maiores perdas. A produtividade das plantas de alface apresentou correlação linear negativa com o índice diário de estresse (IDS). Abstract in english The work had the objectives of determining the effect of water table drawdown velocities on the growth and yield of lettuce crop in a flooded soil, identifying the stage of the crop cycle with the highest reduction in the productivity and obtaining a relation between the crop relative productivity a [...] nd the daily stress index. The statistical experimental design was completely randomized in factorial scheme [(3 x 4) + 1], with three replications. The water table was lowered at 3 stages of the crop cycle (12, 22 and 32 days after the transplanting), four drawdown velocities (30 cm during 24, 48, 72 and 96 h) and a 13 treatment in which stress was not applied with the elevation of the water table. The lettuce presented as a sensible crop to the water-logging, although, it was not possible to define a value for the drainage coefficient because the highest drawdown velocity tested presented 50% of loss in the yield. Among the three crop stages in witch the stress caused by the water table elevation was applied, the first one caused the highest loss in the yield. The relative yield of lettuce plant had a negative linear relation with the daily stress index.

Rafael, Mingoti; Pablo A. N., Flecha; Sérgio N., Duarte; Décio E., Cruciani.

76

Growth and photosynthesis of lettuce  

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Butterhead lettuce is an important glass-house crop in the poor light period in The Netherlands. Fundamental data about the influence of temperature, light and CO 2 on growth and photosynthesis are important e.g. to facilitate selection criteria for new cultivars. In this study on lettuce emphasis has been given to light interception in the poor light period, the relationship of growth rate and relative growth rate with time, dry weight and soil cover, and to photosynthesis propert...

1981-01-01

77

Mechanical Harvesting and Packing of Iceberg Lettuce.  

Science.gov (United States)

This report describes the operations and costs of existing and alternative mechanized lettuce harvesting systems. For mechanization, the immediate prospect is to substitute a harvest machine for the workers who select, cut, and trim the lettuce. Mechanizi...

S. S. Johnson M. Zahara

1977-01-01

78

Evaluación de tratamientos para disminuir cadmio en lechuga (Lactuca sativa L.) regada con agua del río Bogotá / Evaluation of treatments to reduce cadmium concentration in lettuce (Lactuca sativa L.) irrigated with water from the Bogota River  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish Las aguas del río Bogotá presentan altos niveles de contaminación, incluyendo metales pesados, y sus aguas son utilizadas para el riego de importantes extensiones agrícolas. El presente estudio se realizó en el Centro Agropecuario Marengo (Mosquera, Cundinamarca) y su objetivo fue evaluar tratamient [...] os sencillos para disminuir la acumulación de cadmio en lechuga. Los tratamientos fueron: (1) crecimiento selectivo de arvenses en las parcelas; (2) aplicación de CaCO3 antes de trasplante; (3) incorporación de compost antes de trasplante, y (4) control. Se aplicó un diseño de bloques completos al azar con tres repeticiones. Se realizaron mediciones de cadmio en agua, suelo y lechuga. Se tomaron medidas de crecimiento de la lechuga, y se midió el pH y la conductividad eléctrica del suelo. Se encontraron altas concentraciones iniciales de cadmio en suelo (3,97 mg kg-1). Estas concentraciones bajaron significativamente a los 46 días después del trasplante en el tratamiento con arvenses (3,38 mg kg-1). El tratamiento con compost disminuyó significativamente la concentración de cadmio en lechuga (0,26 mg kg-1) respecto a los otros tratamientos (0,45?0,60 mg kg-1) y en corto tiempo aumentó significativamente el peso fresco de las lechugas respecto a los demás tratamientos sin fertilizar; no se encontró relación de esta disminución con el aumento del pH. Abstract in english The water of the Bogota River has high levels of contamination including heavy metals and its waters are used to irrigate crops in important areas. The present study was conducted in the Marengo Agricultural Center (Mosquera, Cundinamarca) and its objective was to evaluate easy treatments to reduce [...] cadmium accumulation in lettuce. The treatments used were: (1) Selective weed growth in the plots, (2) CaCO3 application before plant transplanting, (3) Compost application before plant transplanting and (4) the Control. This study was performed with a randomized complete block design with three repetitions. Amounts of cadmium in the water, soil and lettuce were measured. Measurements of plant growth, pH and electrical conductivity of the soil were also taken. The results showed high initial concentrations of cadmium in the soil (3.97 mg kg-1). These concentrations were found to be significantly lower 46 days after transplanting in the weed treatment (3.38 mg kg-1). The compost treatment significantly lowered the concentration of cadmium in lettuce compared to the other treatments and quickly, significantly increased fresh weight compared to the other treatments without fertilizer; no relationship between the decrease of cadmium and increased pH was found.

RUIZ, JULIANA.

79

Agronomic efficiency of intercropping tomato and lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Four experiments were carried out at the São Paulo State University, Brazil, with the aim of determining the agronomic viability of intercropping tomato and lettuce, under greenhouse conditions. The studied intercropping systems were established by transplanting lettuce at 0, 10, 20 and 30 days after transplanting (DAT) tomato and by transplanting tomato at 0, 10, 20 and 30 DAT lettuce. Intercropped tomato and lettuce were evaluated during two seasons and compared to their sole cropping. The...

Ceci?lio Filho, Arthur B.; Rezende, Bra?ulio L. A.; Barbosa, Jose? C.; Grangeiro, Leilson C.

2011-01-01

80

Replacement of Sesame Oil Cake by Duckweed (Lemna minor in Broiler Diet  

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Full Text Available An experiment was conducted with 120, seven-day old Vencobb commercial broiler chick feeding ad libitum upto 42 days of age on 4 different iso-nitrogenous and iso-energetic diet formulated by replacing dietary sesame oil cake (SOC by duckweed (DW to have its effect on performance of broilers. Live weight, feed conversion and profitability increased when sesame oil cake was partially replaced by duck weed. Complete SOC replaced diet significantly reduced live weight gain, feed intake, feed conversion and profitability, as compared with partial replacement of SOC by duckweed and SOC based control diet. Partial replacement of SOC by DW did not affect survivability of broiler. So it might be concluded that replacement of costly SOC partially by cheaper unconventional DW in broiler diet resulted in increased profitability. Therefore, cheaper duckweed could be practiced in formulating economic balanced diet for broiler.

M.U. Ahammad

2003-01-01

 
 
 
 
81

Microbial Profile of Soil-Free versus In-Soil Grown Lettuce and Intervention Methodologies to Combat Pathogen Surrogates and Spoilage Microorganisms on Lettuce  

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Full Text Available Aquaponics is an effective method to practice sustainable agriculture and is gaining popularity in the US; however, the microbial safety of aquaponically grown produce needs to be ascertained. Aquaponics is a unique marriage of fish production and soil-free produce (e.g., leafy greens production. Fish are raised in fresh water tanks that are connected to water filled beds where fruits and vegetables are grown. The fish bi-products create nutrient-rich water that provides the key elements for the growth of plants and vegetables. The objective of this study was to perform a comparative analysis of the microbial safety and quality of aquaponic lettuce and soil grown lettuce (conventional, bagged, certified organic, and field lettuce. Following this, an intervention study was performed to combat foodborne pathogen surrogates (Salmonella and E. coli, spoilage, and fecal microorganisms using 2.5% acetic acid. The results of the comparative analysis study showed that aquaponically grown lettuce had significantly lower concentration of spoilage and fecal microorganisms compared to in-soil grown lettuce. The intervention study showed that diluted vinegar (2.5% acetic acid significantly reduced Salmonella, E. coli, coliforms, and spoilage microorganisms on fresh lettuce by 2 to 3 log CFU/g. Irrespective of growing methods (in-soil or soilless, it is crucial to incorporate good agricultural practices to reduce microbial contamination on fresh produce. The intervention employed in this study can be proposed to small farmers and consumers to improve quality and safety of leafy greens.

Sujata A. Sirsat

2013-11-01

82

Activity of aphids associated with lettuce and broccoli in Spain and their efficiency as vectors of Lettuce mosaic virus.  

Science.gov (United States)

This research sought to identify the aphid virus vector species associated with lettuce and broccoli crops in Spain, and to determine their population dynamics and ability to transmit Lettuce mosaic virus (LMV). Green tile traps and Moericke yellow water-pan traps were used to monitor aphid flights during the spring and autumn growing seasons of 2001. Aphid species feeding on lettuce were counted weekly. The transmission efficiencies of LMV were determined for the aphid species caught most frequently. The Moericke traps generally caught more aphid species than the tile trap, but the latter was the most suitable to estimate flight activity of species involved in virus spread. Spring aphid catches indicated that the main aphid species landing on lettuce in the regions of Madrid and Murcia was Hyperomyzus lactucae, but Brachycaudus helichrysi was also abundant in both regions. In broccoli in the Navarra region, the most abundant species in spring were Aphis fabae, B. helichrysi and H. lactucae. In autumn-sown crops, the main species landing on lettuce in the Madrid region were Hyadaphis coriandri and Aphis spiraecola. In Murcia, A. spiraecola and Myzus persicae were the most abundant, while in Navarra, Therioaphis trifolii, and various Aphis spp. were the most numerous landing on broccoli. The main aphid species colonising lettuce was Nasonovia ribisnigri, but other less abundant colonising species were Aulacorthum solani and Macrosiphum euphorbiae. The most efficient vectors of LMV were M. persicae, Aphis gossypii and M. euphorbiae, while A. fabae and H. lactucae transmitted with low efficiency, and Rhopalosiphum padi and N. ribisnigri did not transmit. Occurrence of LMV epidemics in central Spain in relation to aphid flights and the role of weeds as virus reservoirs is discussed. PMID:15036838

Nebreda, M; Moreno, A; Pérez, N; Palacios, I; Seco-Fernández, V; Fereres, A

2004-03-01

83

Experimental study and process parameters analysis on the vacuum cooling of iceberg lettuce  

Energy Technology Data Exchange (ETDEWEB)

The vacuum cooling of iceberg lettuce was described in this paper. Based on the energy and mass balance, a mathematical model was developed to analyze the performance of the vacuum cooler and the evaporation-boiling phenomena during vacuum cooling of iceberg lettuce. The temporal trends of total system pressure, produce temperature such as surface temperature, center temperature, mass-average temperature, the weight loss of iceberg lettuce during vacuum cooling were predicted. Validation experimentation is achieved in the designed vacuum cooler. The experimental data were compared with the simulation results. It was found that the differences of the temperature between the simulation and the experiments were within 1 deg. C. The amount of water evaporated from the iceberg lettuce by simulation was 3.32% during the whole vacuum cooling, while the tested water loss rate was 2.97%, the maximal deviation of weight loss was within 0.59%. The simulation results agreed well with the experimental data.

He Suyan [School of Mechanical and Electrical Engineering, Qingdao University, Qingdao 266071 (China)], E-mail: hesuyan67829@sina.com; Li Yunfei [Department of Food Science and Engineering, School of Agriculture and Biology, Shanghai Jiao Tong University (China)

2008-10-15

84

Genetic structure of duckweed population of Spirodela, Landoltia and Lemna from Lake Tai, China.  

Science.gov (United States)

Duckweed is widely used in environmental biotechnology and has recently emerged as a potential feedstock for biofuels due to its high growth rate and starch content. The genetic diversity and composition of a natural duckweed population in genera Spirodela, Landoltia and Lemna from Lake Tai, China, were investigated using probabilistic analysis of multilocus sequence typing (MLST). The 78 strains were categorized into five lineages, among which strains representing L. aequinoctialis and S. polyrhiza were predominant. Among the five lineages, interlineage transfers of markers were infrequent and no recombination was statistically detected. Tajima's D tests determined that all loci are subject to population bottlenecks, which is likely one of the main reasons for the low genetic diversity observed within the lineages. Interestingly, strains of L. turionifera are found to contain small admixture from L. minor, providing rare evidence of transfer of genetic materials in duckweed. This was discussed with respect to the hypothesis that a cross of these two gave rise to L. japonica. Moreover, the conventional maximum-likelihood phylogenetic analysis clearly recognized all the species in the three genera with high bootstrap supports. In conclusion, this work offers a basic framework for using MLST to characterize Spirodela, Landoltia and in particular Lemna strains at the species level, and to study population genetics and evolution history of natural duckweed populations. PMID:24663442

Tang, Jie; Zhang, Fei; Cui, Weihua; Ma, Jiong

2014-06-01

85

GROWTH RESPONSE OF THE DUCKWEED LEMNA MINOR TO HEAVY METAL POLLUTION  

Directory of Open Access Journals (Sweden)

Full Text Available To assess the tolerance and effect of heavy metals pollution on the duckweed Lemna minor, the aquatic plants were exposed to different concentrations of copper (Cu, nickel (Ni, cadmium (Cd and zinc (Zn in a quarter Coïc and Lessaint solution at pH = 6.1 (± 0.1 and under a daily regime of 16 h light (101 ?mol/m2.s1. Copper at 0.2 mg/L and nickel at 0.5 mg/L promoted the growth of Lemna fronds. At higher concentrations, Cu and Ni inhibited the growth of duckweed; the EC50 (concentration causing 50% inhibition were 0.47 mg/L for Cu and 1.29 mg/L for Ni. Cadmium and zinc decreased by 50% the growth of fronds when the medium contained respectively 0.64 and 5.64 mg/L (EC50. Duckweed tolerated Cu, Ni, Cd and Zn at concentrations of 0.4, 3.0, 0.4 and 15.0 mg/L respectively without showing any visible signs of toxicity (chlorosis, frond disconnection and necrosis. On the basis of visible symptoms and the EC50 values, the toxicity of the metals on Lemna. minor was in decreasing order of damage: Cu > Cd > Ni > Zn. It was concluded that the duckweed Lemna. minor is very sensitive to copper and cadmium pollution.

N. Khellaf ? M. Zerdaoui

2009-07-01

86

Selenium speciation using HPLC-ICP-MS in selenium-enriched duckweed (Lemna minor)  

International Nuclear Information System (INIS)

Complete text of publication follows. The HPLC-ICP-MS for speciation analysis of selenium was developed and applied to selenium enriched duckweed (Lemna minor). The duckweed in Hoagland's E-medium containing Se from sodium selenate in the concentration of 0, 5, 10, 15 and 20 mg/L was cultured. The effect of selenium supplemented concentration and cultured periods (0-8 days) were studied. The results revealed that the optimum concentration of supplemented Se and cultured period were 10 mg/L and 6 days, respectively. The Se-enriched duckweed samples (whole plant) were dried and homogenized. The 0.1 M HCl in 10% methanol extracts were analyzed. Selenium speciation was carried out by ion-pairing HPLC (2.5 mM sodium 1-butanesulfonate, 8 mM tetramethyl ammonium hydroxide and trifluoro acetic acid at pH 4.5). The organic selenium species found in the extract was selenomethylcysteine, selenomethionine and others unknown species. The percentage contributions of selenium in both species of the total selenium were 0.6 and 1.0%, respectively. It can be seen that Se-enriched duckweed can feasibility be a dietary source of Se. The authors would like to thank Center of Excellence for Innovation in Chemistry (PERCH-CIC), Commission on Higher Education, Ministry of Education for financial support.

2009-09-03

87

Antimicrobial activity of plant essential oils against Escherichia coli O157:H7 and Salmonella on lettuce.  

Science.gov (United States)

Foodborne outbreaks associated with the consumption of fresh produce have increased. In an effort to identify natural antimicrobial agents as fresh produce-wash, the effect of essential oils in reducing enteric pathogens on iceberg and romaine lettuce was investigated. Lettuce pieces were inoculated with a five-strain cocktail of Escherichia coli O157:H7 or Salmonella enterica (5 log CFU/g) and then immersed in a treatment solution containing 5 ppm free chlorine, cinnamaldehyde, or Sporan(®) (800 and 1000 ppm) alone or in combination with 200 ppm acetic acid (20%) for 1 min. Treated leaves were spin-dried and stored at 4°C. Samples were taken to determine the surviving populations of E. coli O157:H7, Salmonella, total coliforms, mesophilic and psychrotrophic bacteria, and yeasts and molds during the 14-day storage period. The effect of treatments on lettuce color and texture was also determined. Cinnamaldehyde-Tween (800 ppm, 800T) reduced E. coli O157:H7 by 2.89 log CFU/g (piceberg lettuce at day 0; Sporan(®)-acetic acid (1000SV) reduced E. coli O157:H7 and Salmonella on iceberg and romaine lettuce by 2.68 and 1.56 log CFU/g (piceberg and romaine lettuce throughout the storage time. The natural microbiota on treated lettuce leaves increased during the storage time, but remained similar (p>0.05) to those treated with chlorine and control (water). The texture and the color of iceberg and romaine lettuce treated with essential oils were not different from the control lettuce after 14 days of storage. This study demonstrates the potential of Sporan(®) and cinnamaldehyde as effective lettuce washes that do not affect lettuce color and texture. PMID:23256843

Yossa, Nadine; Patel, Jitendra; Millner, Patricia; Ravishankar, Sadhana; Lo, Y Martin

2013-01-01

88

Nutritional Efficiency of Phosphorus in Lettuce  

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This work aimed to evaluate the efficiency of phosphorus absorption, translocation, and utilization in lettuce. A greenhouse experiment was arranged in a completely randomized design in a 5x2 factorial scheme to test five phosphorus doses (0, 100, 200, 300, and 500 mg dm-3) and two lettuce varieties (Lisa and Americana). The soil was incubated with limestone for pH correction. Following this procedure, a phosphate fertilization was carried and the lettuce seedlings were transplante...

Ana Paula Almeida Bertossi; André Thomazini; Abel Souza da Fonseca; José Francisco Teixeira do Amaral

2013-01-01

89

Water plants A/W  

…and water milfoil (Myriophyllum spp). A few, however, are free-floating below the water surface, such as ivy leaved duckweed (Lemna trisulca) and hornwort (Ceratophyllum). When flowering, most extend their flowering shoots above the water. Water milfoil (Myriophyllum spp) and mare's tail (Hippuris vulgaris…

90

Response of hydroponically grown head lettuce on residual monomer from polyacrylamide.  

Science.gov (United States)

The aim was to assess acrylamide monomer (AMD) uptake by hydroponically grown lettuce. Lettuce was cultivated by applying plant tissue testing in a recycled system by the use of nutrient solutions prepared with two water-soluble flocculants F3 and F4 containing 176 and 763 mg kg(-1) of AMD, respectively. The effects on growth, fresh weight and plant leaf quality were evaluated by comparing these treatments and one control standard nutrient solution typically recommended for lettuce hydroponic cultivation. To assess the nutritional status of lettuce, samples were collected and lyophilised before determination of the selected micro- and macro-element contents. An HPLC with photodiode array detector method was applied to determine AMD in both selected flocculants and dried plant samples. Results show that lettuces cultivated under the conditions described above absorb AMD from nutrient solutions into their leaves. The AMD presence in recycled nutrient solutions has a negative influence on the growth of lettuce, reducing their average fresh weight and average number of leaves. The study confirmed that the problem of AMD mobility and its accumulation risk in plants should to be an important topic with respect to safe polyacrylamide (PAM) handling in the agro food area. PMID:24916210

Mroczek, E; Konieczny, P; Kleiber, T; Wa?kiewicz, A

2014-08-01

91

The influence of duckweed species diversity on biomass productivity and nutrient removal efficiency in swine wastewater.  

Science.gov (United States)

The effect of temperature, light intensity, nitrogen and phosphorus concentrations on the biomass and starch content of duckweed (Landoltia punctata OT, Lemna minor OT) in monoculture and mixture were assessed. Low light intensity promoted more starch accumulation in mixture than in monoculture. The duckweed in mixture had higher biomass and nutrient removal efficiency than those in monoculture in swine wastewater. Moreover, the ability of L. punctata C3, L. minor C2, Spirodela polyrhiza C1 and their mixtures to recovery nutrients and their biomass were analyzed. Results showed that L. minor C2 had the highest N and P content, while L. punctata C3 had the highest starch content, and the mixture of L. punctata C3 and L. minor C2 had the greatest nutrient removal rate and the highest biomass. Compared with L. punctata C3 and L. minor C2 in monoculture, their biomass in mixture increased by 17.0% and 39.8%, respectively. PMID:24998479

Zhao, Zhao; Shi, Huijuan; Liu, Yang; Zhao, Hai; Su, Haifeng; Wang, Maolin; Zhao, Yun

2014-09-01

92

Differential sensitivity of duckweeds (Lemnaceae) to sulfite: I. Carbon assimilation and frond replication rate as factors influencing sulfite phytotoxicity  

Energy Technology Data Exchange (ETDEWEB)

The thiol content and hydrogen sulfide emission responses of duckweeds (Lemnaceae) differentially sensitive to sulfite enrichment were studied, at two levels of irradiance. The objectives were to examine the relationship of selected parameters of sulfite metabolism to sulfite sensitivity, and the role of light level on modifying sulfite metabolic responses and duckweed sulfite sensitivity. Under low light, thiol contents were increased 30 to 40% by sulfite in all three duckweeds examined. Hydrogen sulfide was emitted by all three species, and emission rates were up to four times higher in the sulfite tolerant duckweed Lemna valdiviana. Under high light, sulfite increased thiol contents by an average of 40% in L. valdiviana and Spirodela oligorhiza, but only 20% in Lemna gibba. The greater light enhancement of thiol content exhibited by L. valdiviana and S. oligorhiza may be indicative of larger or more numerous sulfur sinks. Hydrogen sulfide emission rates were also enhanced under high light, and L. gibba exhibited a 17% increase relative to its low light rate. In comparison, L. valdiviana and S. oligorhiza exhibited 55% and 60% increases, respectively. The ability to form elevated internal thiols and hydrogen sulfide were found to be important to sulfite tolerance in duckweeds. Enhancement of both processes under high light may contribute to increased tolerance of sulfite in L. gibba and S. oligorhiza. It is hypothesized that thiol production and hydrogen sulfide emission are important sulfite detoxification processes in duckweeds, and enhancement of sulfite detoxification is fundamental to the modification of duckweed sulfite sensitivity by the photoenvironment. 25 refs., 3 tabs.

Takemoto, B.K.; Noble, R.D.

1986-01-01

93

Análise sensorial, teores de nitrato e de nutrientes de alface cultivada em hidroponia sob águas salinas / Sensory analysis, nitrate and nutrient concentration of lettuce grown in hydroponics under saline water  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O presente trabalho teve como objetivos determinar os teores de nutrientes e de nitrato e realizar análise sensorial de alface cultivada em sistema hidropônico sob água salina. O experimento foi conduzido em ambiente protegido no período de dezembro de 2007 a janeiro de 2008, em Piracicaba (SP). O d [...] elineamento experimental foi de blocos ao acaso, sendo estudados cinco níveis de salinidade da água de irrigação, utilizando-se NaCl (Condutividade elétrica da água (CEa): 0,42, 1,53, 3,52, 5,55 e 7,43 dS m-1) em duas cultivares de alface (Verônica e Pira Roxa), em esquema fatorial. Foram avaliados a análise sensorial aplicando escala hedônica e através dessa, o que os provadores mais apreciaram e o que menos gostaram de cada amostra, intenção de compra e consumo, teor de nitrato, absorção de nutrientes pela folhas e determinação dos nutrientes presentes na solução nutritiva. Para o atributo sabor a cultivar Verônica recebeu as melhores notas no nível de salinidade 1,53 e 5,55 dS m-1. Para a cultivar Pira Roxa a melhor nota foi atribuída para a alface produzida na água não salina. Para os demais atributos não houve diferença significativa nos diferentes níveis de salinidade. Com relação à intenção de compra, constatou-se que as alfaces cv. Verônica e Pira Roxa apresentaram boa aceitação de mercado. Os menores níveis de nitrato (1960 mg kg-1 e 2620 mg kg-1 de massa de matéria fresca), da Verônica e Pira Roxa, respectivamente, foram relacionados à condutividade elétrica de 0,42 dS m-1, aumentando a salinidade da água para 7,43 dS m-1, o teor foliar de nitrato aumentou para 2500 mg kg-1 e 3420 mg kg-1 para as cultivares Verônica e Pira Roxa. Como o tempo de exposição da alface à salinidade em sistema hidropônico foi curto, em torno de 25 dias, não se verificou sintomas de deficiência nutricional e toda alface foi classificada como apropriada para consumo humano. Abstract in english This study aimed to evaluate the content of nutrients and nitrate and perform sensory analysis of lettuce in hydroponic system under saline water. The experiment was carried out in a greenhouse from December, 2007 to January, 2008, in Piracicaba. The experimental design was randomized blocks and fac [...] torial scheme (five salinity levels obtained with the addition of NaCl that resulted in different electrical conductivities of the water (dS m-1): 0.42, 1.53, 3.52, 5.55, 7.43 and two cultivas of lettuce (Veronica and Pira Roxa). The evaluations were: sensory analysis applying hedonic scale and through this, which sample presented the best and the least taste, the purchase intent and consumption, nitrate, absorption of nutrients by leaves and determination of nutrients in the nutrient solution. For the attribute of cultivars, Veronica received the highest marks in salt level 1.53 and 5.55 dS m-1. For cultivar Pira Roxa was awarded the best grade for lettuce grown in non-saline water. For other attributes there was no significant difference in levels of salinity. To purchase intention, it was found that cv. Verônica and Pira Roxa had good market acceptance. The lowest levels of nitrate (1960 mg kg-1 and 2620 mg kg-1 fresh weight) of Verônica and Pira Roxa, respectively, were related to the electrical conductivity of 0.42 dS m-1, increasing water salinity to 7.43 dS m-1, the leaf content of nitrate increased to 2500 mg kg-1 and 3420 mg kg-1 for the cultivars Verônica and Pira Roxa. As the time of exposure to salt in a hydroponic system was short, around 25 days, there were no symptoms of nutrient deficiency and whole lettuce was classified as suitable for human consumption.

Dalva, Paulus; Durval, Dourado Neto; Eloi, Paulus.

94

Replacement of Sesame Oil Cake by Duckweed (Lemna minor) in Broiler Diet  

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An experiment was conducted with 120, seven-day old Vencobb commercial broiler chick feeding ad libitum upto 42 days of age on 4 different iso-nitrogenous and iso-energetic diet formulated by replacing dietary sesame oil cake (SOC) by duckweed (DW) to have its effect on performance of broilers. Live weight, feed conversion and profitability increased when sesame oil cake was partially replaced by duck weed. Complete SOC replaced diet significantly reduced live weight gain, feed intake,...

Ahammad, M. U.; Swapon, M. S. R.; Yeasmin, T.; Rahman, M. S.; Ali, M. S.

2003-01-01

95

Leaf Age as a Risk Factor in Contamination of Lettuce with Escherichia coli O157:H7 and Salmonella enterica?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Outbreaks of Escherichia coli O157:H7 infections have been linked increasingly to leafy greens, particularly to lettuce. We present here the first evidence that this enteric pathogen can multiply on the leaves of romaine lettuce plants. The increases in population size of E. coli O157:H7 in the phyllosphere of young lettuce plants ranged from 16- to 100-fold under conditions of warm temperature and the presence of free water on the leaves and varied significantly with leaf age. The population...

Brandl, M. T.; Amundson, R.

2008-01-01

96

Relación porosidad-retención de humedad en mezclas de sustratos y su efecto sobre variables respuesta en plántulas de lechuga / Porosity-water retention relationship in substrate mixtures and its effect on response variables in lettuce seedlings  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish Se estudió la relación entre la porosidad, el tamaño y distribución de partícula (1-2 mm y 2-3.36 mm) con la retención de humedad para diferentes mezclas de materiales: fibra de coco (Fc): piedra (P) o tezontle (T), combinados en proporciones variables (0:100, 25:75, 50:50, 75:25 y 100:0 v/v). Ademá [...] s, se analizó el efecto de la combinación Fc:P con un tamaño de partícula (1-2 mm) sobre variables respuesta en plántulas de lechuga var. Summertime. Se determinó la curva de retención de humedad. Los tipos de poros y el patrón de distribución de las partículas de las mezclas, se analizaron a través de secciones delgadas y la porosidad se cuantificó con un analizador de imágenes. Los resultados mostraron que las mezclas Fc:T y Fc:P (75:25 v/v), presentaron la mayor capacidad de retención de humedad gravimétrica (230 %) y volumétrica (98 %). Además, un sistema de poros heterogéneo o anisotrópico (macro y micro), y una distribución en bandas, que permitieron percolación y retención de humedad óptima para el desarrollo de las plántulas de lechuga, expresada en las mejores variables respuesta y calidad del cepellón. En contraste, el resto de las mezclas con un sistema de poros homogéneo o isotrópico, ya sea de poros de empaquetamiento simple o compuesto, y una distribución básica aleatoria de partículas, generaron más percolación o más retención de humedad, que limitaron el crecimiento de las plántulas. La micromorfología puede ser útil para comprender las propiedades físicas de los sustratos al determinar directamente el tipo, tamaño y continuidad de los poros, características que afectan la disponibilidad de agua-aire. Abstract in english The relationship among porosity, size and particle distribution (1-2 mm and 2-3.36 mm) with water retention for different mixtures of materials: coir (Fc), stone (P) or volcanic stone (T), combined in variables proportions (0:100, 25:75, 50:50, 75:25 and 100:0 v/v) was studied. The effect of the com [...] bination Fc:P with a particle size (1-2 mm) on response variables in lettuce seedlings var. Summertime was analyzed. The water retention curve was determined. The types of pores and the particle distribution pattern of the mixtures was analyzed though thin sections. Porosity was quantified using an image analyzer. Results showed that Fc:T and Fc:P mixtures (75:25 v/v), showed the highest volumetric (98 %) and gravimetric (230 %) water retention capacity, as well as an anisotropic or heterogeneous pore system (macro and micro), and a band distribution, that allowed percolation and optimal water retention for the development of lettuce seedlings, represented in the best response variables and quality of root ball. In contrast, the rest of the mixture with an isotropic or homogeneous pore system, either simple or compound packing pores, and a basic random distribution of particles, generating more percolation or more water retention, that limited the growth of seedlings. Micromorphology can be useful for understanding the physical properties of the substrates by directly determining the type, size and continuity of pores, characteristics that affect water-air availability.

Ma. Del Carmen, Gutiérrez-Castorena; Jorge, Hernández Escobar; Carlos Alberto, Ortiz-Solorio; Rosa, Anicua Sánchez; Ma. Encarnación, Hernández Lara.

97

Efeito de pontas de pulverização e de arranjos populacionais de plantas de Eichhornia crassipes e Salvinia auriculata na deposição de calda de pulverização sobre plantas de Pistia stratiotes Effect of spray tips and water hyacinth and water lettuce plant population arrangements of watermoss plant spray mix deposition  

Directory of Open Access Journals (Sweden)

Full Text Available Este trabalho teve por objetivo avaliar o depósito de calda pulverizada por dois tipos de pontas de pulverização sob plantas de alface-d'água (Pistia stratiotes dispostas em diferentes arranjos populacionais com plantas de aguapé (Eichhornia crassipes e salvínia (Salvinia auriculata. Para isso, foi conduzido um experimento em condições de caixas-d'água em delineamento experimental inteiramente casualizado, com quatro repetições. Os tratamentos estiveram dispostos em esquema fatorial 2 x 8, sendo dois tipos de pontas de pulverização (ConeJet TXVK-8 e TeeJet DG 11002 VS e oito proporções entre as plantas aquáticas, a saber: dominância total da área correspondente a 100% de cobertura da caixa-d'água pelas plantas de alface-d'água; e as proporções entre plantas de alface-d'água e plantas de aguapé ou salvínia a 75%:25%, 50%:50% e 25%:75%. Também foi utilizada uma densidade tripla, na qual as três espécies estiveram igualmente dispostas na proporção de 33,33%. Soluções dos corantes Amarelo Tartrasina FDC-5 a 3.500 ppm e Azul Brilhante FDC-1 a 1.000 ppm foram utilizadas como traçadores para as pontas TXVK-8 e DG 11002VS, respectivamente. A pulverização de ambas as soluções foi efetuada na mesma unidade experimental, com um intervalo de 30 minutos entre si, utilizando-se um pulverizador costal pressurizado com CO2, calibrado de modo a proporcionar um volume de aplicação aproximado de 200 L ha. Após a pulverização, as plantas presentes nos reservatórios foram lavadas com água destilada, até remoção total dos corantes. Os depósitos totais de calda foram estimados em ?L por planta, e os depósitos unitários, em ?L cm-2 de superfície foliar. O aumento na proporção de plantas de aguapé na associação proporcionou menores depósitos de calda de pulverização sobre as plantas de alface-d'água. Em contrapartida, o aumento na proporção de salvínia na associação propiciou maiores depósitos de calda de pulverização, independentemente do tipo de ponta de pulverização. A ponta TXVK-8 proporcionou depósitos unitários e totais de calda de pulverização superiores aos da ponta DG 11002VS.This study aimed to evaluate two types of nozzles (ConeJet TXVK-8 and TeeJet DG 11002 VS and the amount of spray mix deposited on water lettuce (Pistia stratiotes plants organized under different population arrangements with water hyacinth (Eichhornia crassipes and eared watermoss (Salvinia auriculata plants. In addition to a full-dominance proportion over the area, corresponding to 100% cover of the water tank by eared watermoss plants, arrangements were used with either water hyacinth or water lettuce at 75%:25%, 50%:50%, and 25%:75%. Triple density was also used, with the three species being equally displayed at a 33.33% proportion. Dye solutions of FD&C Yellow no. 5 at 3,500 ppm and FD&C Blue no. 1 at 1,000 ppm were used as spraying tracers for TXVK-8 and DG 11002 VS nozzles, respectively. Both solutions were sprayed at the same plot within 30 minute interval each through a CO2 pressured backpack knapsack calibrated to deliver a spray volume around 200 L ha-1 . Plants at reservoirs were flushed with distilled water until total removal of the dyes deposited on them. The total spray deposits were estimated in ?L per plant and the unitary deposits where estimated in ?L cm-2 of foliar surface. Increase in water hyacinth plant proportion in the arrangement resulted in lower spray deposition over water lettuce. Increase in water moss plant proportion in the arrangement provided higher spray depositions over water lettuce, independently of the nozzle type used. The TXVK-8 nozzles provided higher unitary and total spray depositions compared to the DG 11002 VS nozzle.

S.R. Marchi

2009-06-01

98

Efeito de pontas de pulverização e de arranjos populacionais de plantas de Eichhornia crassipes e Salvinia auriculata na deposição de calda de pulverização sobre plantas de Pistia stratiotes / Effect of spray tips and water hyacinth and water lettuce plant population arrangements of watermoss plant spray mix deposition  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Este trabalho teve por objetivo avaliar o depósito de calda pulverizada por dois tipos de pontas de pulverização sob plantas de alface-d'água (Pistia stratiotes) dispostas em diferentes arranjos populacionais com plantas de aguapé (Eichhornia crassipes) e salvínia (Salvinia auriculata). Para isso, f [...] oi conduzido um experimento em condições de caixas-d'água em delineamento experimental inteiramente casualizado, com quatro repetições. Os tratamentos estiveram dispostos em esquema fatorial 2 x 8, sendo dois tipos de pontas de pulverização (ConeJet TXVK-8 e TeeJet DG 11002 VS) e oito proporções entre as plantas aquáticas, a saber: dominância total da área correspondente a 100% de cobertura da caixa-d'água pelas plantas de alface-d'água; e as proporções entre plantas de alface-d'água e plantas de aguapé ou salvínia a 75%:25%, 50%:50% e 25%:75%. Também foi utilizada uma densidade tripla, na qual as três espécies estiveram igualmente dispostas na proporção de 33,33%. Soluções dos corantes Amarelo Tartrasina FDC-5 a 3.500 ppm e Azul Brilhante FDC-1 a 1.000 ppm foram utilizadas como traçadores para as pontas TXVK-8 e DG 11002VS, respectivamente. A pulverização de ambas as soluções foi efetuada na mesma unidade experimental, com um intervalo de 30 minutos entre si, utilizando-se um pulverizador costal pressurizado com CO2, calibrado de modo a proporcionar um volume de aplicação aproximado de 200 L ha. Após a pulverização, as plantas presentes nos reservatórios foram lavadas com água destilada, até remoção total dos corantes. Os depósitos totais de calda foram estimados em ?L por planta, e os depósitos unitários, em ?L cm-2 de superfície foliar. O aumento na proporção de plantas de aguapé na associação proporcionou menores depósitos de calda de pulverização sobre as plantas de alface-d'água. Em contrapartida, o aumento na proporção de salvínia na associação propiciou maiores depósitos de calda de pulverização, independentemente do tipo de ponta de pulverização. A ponta TXVK-8 proporcionou depósitos unitários e totais de calda de pulverização superiores aos da ponta DG 11002VS. Abstract in english This study aimed to evaluate two types of nozzles (ConeJet TXVK-8 and TeeJet DG 11002 VS) and the amount of spray mix deposited on water lettuce (Pistia stratiotes) plants organized under different population arrangements with water hyacinth (Eichhornia crassipes) and eared watermoss (Salvinia auric [...] ulata) plants. In addition to a full-dominance proportion over the area, corresponding to 100% cover of the water tank by eared watermoss plants, arrangements were used with either water hyacinth or water lettuce at 75%:25%, 50%:50%, and 25%:75%. Triple density was also used, with the three species being equally displayed at a 33.33% proportion. Dye solutions of FD&C Yellow no. 5 at 3,500 ppm and FD&C Blue no. 1 at 1,000 ppm were used as spraying tracers for TXVK-8 and DG 11002 VS nozzles, respectively. Both solutions were sprayed at the same plot within 30 minute interval each through a CO2 pressured backpack knapsack calibrated to deliver a spray volume around 200 L ha-1 . Plants at reservoirs were flushed with distilled water until total removal of the dyes deposited on them. The total spray deposits were estimated in ?L per plant and the unitary deposits where estimated in ?L cm-2 of foliar surface. Increase in water hyacinth plant proportion in the arrangement resulted in lower spray deposition over water lettuce. Increase in water moss plant proportion in the arrangement provided higher spray depositions over water lettuce, independently of the nozzle type used. The TXVK-8 nozzles provided higher unitary and total spray depositions compared to the DG 11002 VS nozzle.

Marchi, S.R.; Martins, D.; Costa, N.V.; Domingos, V.D.; Cardoso, L.A..

99

Effect of pressure on the vacuum cooling of iceberg lettuce  

Energy Technology Data Exchange (ETDEWEB)

Vacuum cooling is known as a rapid evaporative cooling technique for any porous product which has free water. The aim of this paper is to apply vacuum cooling technique to the cooling of the iceberg lettuce and show the pressure effect on the cooling time and temperature decrease. The results of vacuum cooling are also compared with conventional cooling (cooling in refrigerator) for different temperatures. Vacuum cooling of iceberg lettuce at 0.7 kPa is about 13 times faster than conventional cooling of iceberg lettuce at 6 C. It has been also found that it is not possible to decrease the iceberg lettuce temperature below 10 C if vacuum cooling method is used and vacuum pressure is set to 1.5 kPa. (author) [French] Le refroidissement sous vide est connu comme une technique evaporative rapide refroidissant pour n'importe quel produit poreux qui a de l'eau libre. Le but de ce papier est d'appliquer le refroidissement sous vide pour le refroidissement de la laitue et examiner l'effet de la pression sur le temps de refroidissement et la diminution de temperature. Les resultats de refroidissement sous vide sont aussi compares avec le refroidissement conventionnel (refroidissement dans le refrigerateur) pour les differentes temperatures. Le refroidissement a vide de laitue a 0.7 kPa est environ 13 fois plus vite que le refroidissement conventionnel de laitue croquante a 6 C. Il a ete aussi constate qu'il n'est pas possible de diminuer la temperature de laitue ci-dessous 10 C si le refroidissement sous vide est utilise comme methode et la pression a vide est montree a 1.5 kPa. (orig.)

Ozturk, Hande Mutlu [Pamukkale University, Food Engineering Department, Faculty of Engineering, Denizli (Turkey); Ozturk, Harun Kemal [Pamukkale University, Mechanical Engineering Department, Faculty of Engineering, 20070 Kinikli, Denizli (Turkey)

2009-05-15

100

Transfer of Escherichia coli O157:H7 to iceberg lettuce via simulated field coring.  

Science.gov (United States)

The field-core (cut and core) harvesting technique used for iceberg lettuce was evaluated as a potential means of cross-contamination with Escherichia coli O157:H7. Chlorinated water treatment was evaluated for its efficacy in removing or inactivating the pathogen on the blade portion of the field coring device and on cored lettuce. Field coring devices inoculated by immersing blades in soil containing E. coli O157:H7 at 3.74 or 6.57 log CFU/g contained 3.13 and 4.97 log CFU per blade, respectively. Treatment of inoculated field coring device blades by immersing in chlorinated water (200 microg/ml total chlorine) for 10 s resulted in a reduction of 1.56 log CFU per blade, which was 1.42 log CFU per blade greater than that achieved using water, but insufficient to eliminate the pathogen on blades. Field coring devices inoculated by contacting soil containing E. coli O157:H7 at 2.72 and 1.67 log CFU/g, then repeatedly used to cut and core 10 lettuce heads, transferred the pathogen to 10 and 5 consecutively processed heads, respectively. Lettuce cores remained positive for the pathogen after spraying with 100 microg/ml free chlorine for 120 s at 2.81 kg/cm2 (40 lb/in2), regardless of the inoculum level. The number of E. coli O157:H7 recovered from inoculated lettuce cores treated for 10 s with chlorine was significantly (P lettuce with chlorinated or untreated water reduces but does not eliminate E. coli O157:H7. PMID:19343932

Taormina, Peter J; Beuchat, Larry R; Erickson, Marilyn C; Ma, Li; Zhang, Guodong; Doyle, Michael P

2009-03-01

 
 
 
 
101

Water plants A/W  

…Floating-leaved plants This group includes water lilies (Nymphaea alba and Nuphar lutea). Most of the plants are rooted in the bed and have long pliable stems, but a few, such as duckweed (Lemna minor) and frog-bit (Hydrocharis morsus-ranae), are not and drift about the water surface. Members of this group…

102

Induction of betacyanin formation in Chenopodium album cell cultures by co-cultivation with the duckweed Wolffia arrhiza.  

Science.gov (United States)

Cells of Chenopodium album and whole plants of the duckweed Wolffia arrhiza were cocultivated. In the presence of Wolffia arrhiza the synthesis of a red-violet pigment (betacyanin) was induced in several cells or cell clusters of Chenopodium album in the light. The exchange of solutes through the liquid phase was necessary for the induction of pigment formation. The red-violet cells could be selected and subcultivated resulting in a red callus. A reddish cell suspension was obtained in liquid culture in the presence of the duckweeds. PMID:24193767

Rudat, A; Ehwald, R

1994-02-01

103

Evaluación de la biomasa y manejo de Lemna gibba (lenteja de agua) en la bahía interior del Lago Titicaca, Puno / Evaluation of biomass and management Lemna gibba (duckweed) in the inner bay of Lake Titicaca, Puno  

Scientific Electronic Library Online (English)

Full Text Available SciELO Peru | Language: Spanish Abstract in spanish Uno de los mayores problemas que enfrenta la ciudad de Puno es la presencia de la lenteja de agua (Lemna gibba) en la bahía interior del Lago Titicaca, debido al proceso de eutrofización que sufre a causa del mal tratamiento de las aguas residuales de la ciudad de Puno. Muchas de las estrategias pla [...] nteadas hasta ahora no han dado resultados positivos en la reducción de la biomasa de Lemna gibba, debido a que estos planes están direccionados a la exterminación de este organismo. En lugar de ello se debe pensar en la forma más sostenible de hacer uso de la lenteja. Es por eso que los objetivos fueron: (a) estimar la biomasa (kg/m²) de lenteja de agua de la bahía interior del lago Titicaca y, (b) plantear una estrategia de manejo de la lenteja de agua de la bahía interior del lago Titicaca. El promedio de la biomasa de la lenteja de agua en la bahía interior fue de 6.94 kg/m², mientras que los promedios de pH y temperatura del agua fueron de 6.3 y 13.8°C, respectivamente. Esto prueba la eficacia de este organismo para crecer en condiciones difíciles (además hay altos niveles de N, P y metales pesados), por lo que su manejo puede ser una alternativa para disminuir el proceso de eutrofización del lago. Las estrategias de manejo de lenteja estuvieron enmarcadas dentro de un plano social, económico y ambiental, lo que permite su sostenibilidad en beneficio de la población de Puno y del ecosistema del lago Titicaca. Abstract in english One of the biggest problems Puno city is currently facing is the presence of duckweed (Lemna gibba) in the inner bay of Lake Titicaca, caused by eutrophication due to bad wastewater treatment. Many of the strategies proposed so far have not yielded positive results, because these plans were directed [...] to the extermination of this organism. Instead, the most sustainable duckweed use should be considered. That is why the objectives of this study were: (a) To estimate duckweed biomass (kg/m²) in the inner bay of Lake Titicaca, (b) To propose a management strategy for the duckweed from the inner bay of Lake Titicaca. The average biomass of the duckweed in the inner bay was 6.94 kg/m²; the average pH and temperature of the water were 6.3 and 13.8°C, respectively. This proves the effectiveness of this organism to grow in difficult conditions (in addition there are high levels of N, P and heavy metals), so that its management can be used as an alternative to reduce the eutrophication of the lake. Moreover, duckweed management strategies were framed within social, economical and environmental plans. Therefore, this macrophyte management is sustainable and beneficial for the people of Puno and the ecosystem of Lake Titicaca.

Ángel, Canales-Gutiérrez.

104

Characterization of photosynthetically active duckweed (Wolffia australiana) in vitro culture by Respiration Activity Monitoring System (RAMOS).  

Science.gov (United States)

The feasibility of oxygen transfer rate (OTR) measurement to non-destructively monitor plant propagation and vitality of photosynthetically active plant in vitro culture of duckweed (Wolffia australiana, Lemnaceae) was tested using Respiration Activity Monitoring System (RAMOS). As a result, OTR proofed to be a sensitive indicator for plant vitality. The culture characterization under day/night light conditions, however, revealed a complex interaction between oxygen production and consumption, rendering OTR measurement an unsuitable tool to track plant propagation. However, RAMOS was found to be a useful tool in preliminary studies for process development of photosynthetically active plant in vitro cultures. PMID:17450327

Rechmann, Henrik; Friedrich, Andrea; Forouzan, Dara; Barth, Stefan; Schnabl, Heide; Biselli, Manfred; Boehm, Robert

2007-06-01

105

Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus L.)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso-N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35Œ corn (29Œ wheat (20Œ wheat bran (10Œ fish oil (3Œ diamol (2€and premix (1Ž Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20nd 40?f dry matter of duckweed, in a dry and fresh form...

El-shafai, S. A. A. M.; El-gohary, F.; Verreth, J. A. J.; Schrama, J. W.; Gijzen, H. J.

2004-01-01

106

Residues of maneb in potatoes and lettuce and their persistence during cooking, washing and uv exposition  

International Nuclear Information System (INIS)

Lettuce plants were treated each with 0,186 mg of 14C maneb and 1,86 mg unlabelled maneb. The plants were analyzed 30 days later and subjected to washing. Washing eliminates 17,46% of total 14C maneb applied. No Etu was observed in water.Washing and baking cause a significant decrease of EBDC in potatoes samples and the UV exposition involves a decrease of the fungicide and a formation of Etu. On the other hand 54 % and 38% of lettuce and potatoe samples analyzed by CS2 method exceed the authorized norms

1992-01-01

107

Deposição de calda de pulverização sobre plantas de salvínia em função de pontas de pulverização e arranjos populacionais entre plantas de Aguapé e Alface-D'Água Spray deposition on water fern plants in function of nozzle tips and population arrangements with water Hyacinth and Water Lettuce plants  

Directory of Open Access Journals (Sweden)

Full Text Available Este trabalho teve como objetivo avaliar o depósito de calda pulverizada por dois tipos de pontas de pulverização sobre plantas de Salvinia auriculata dispostas em diferentes arranjos populacionais com plantas de Eichhornia crassipes e Pistia stratiotes. Um experimento foi conduzido em condições de caixas-d'água em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 2 x 8, sendo dois tipos de pontas de pulverização (ConeJet TXVK-8 e TeeJet DG 11002 VS e oito proporções entre as plantas aquáticas, a saber: dominância total da área de cobertura da caixa-d'água pelas plantas de salvínia (100%; e as proporções entre plantas de salvínia e de aguapé ou alface-d'água a 75%:25%, 50%:50% e 25%:75%. Também foi utilizada uma densidade tripla, na qual as três espécies estiveram igualmente dispostas na proporção de 33%. Soluções dos corantes Amarelo Tartrasina FDC-5 a 3.500 ppm e Azul Brilhante FDC-1 a 1.000 ppm foram utilizadas como traçadores para as pontas TXVK-8 e DG 11002VS, respectivamente. A pulverização das soluções foi efetuada na mesma unidade experimental, com intervalo de 30 minutos entre si, com auxílio de um pulverizador costal pressurizado com CO2, calibrado de modo que proporcionasse volume de aplicação aproximado de 200 L ha-1. Não foram observadas diferenças estatísticas entre os tipos de pontas de pulverização nas diferentes proporções estudadas, exceto para depósitos totais de calda de pulverização nas plantas na condição de dominância total da salvínia, uma vez que a ponta ConeJet TXVK-8 foi superior à TeeJet DG 11002 VS. Os valores dos depósitos diminuíram com o aumento da proporção de plantas de aguapé na associação e foram na condição em que 25% de plantas de salvínia estiveram associadas a 75% de plantas de aguapé. A presença da espécie alface-d'água não influenciou a deposição de gotas sobre as folhas de salvínia.This study aimed to evaluate two types of spray tips (ConeJet TXVK-8 and TeeJet DG 11002 VS and the amount of spray mix deposited on Salvinia auriculata plants organized under different population arrangements with Eichhornia crassipes and Pistia stratiotes plants. In addition to a full-dominance proportion over the area, corresponding to 100% cover of the water tank by eared water moss plants, arrangements with either water hyacinth or water lettuce were made at 75%:25%, 50%:50%, and 25%:75%. A triple density, in which the three species were equally disposed at a 33.33% proportion, was also used. Dye solutions of FD&C Yellow no. 5 at 3,500 ppm and FD&C Blue no.1 at 1,000 ppm were used, as spraying tracers for TXVK-8 and DG 11002 VS nozzles, respectively. Both solutions were sprayed at the same plot within a 30-minute interval each, through a CO2 pressured backpack, calibrated to deliver a spray volume of around 200 L ha-1. The total spray deposits were estimated in mL per plant and the unit deposits in mL cm² of foliar surface. No significant differences were observed between the nozzle tips used at different population arrangements, except total spray mix deposited on plants at 100% of eared water moss dominance proportion, with ConeJet TXVK-8, providing superior spray mix deposition, compared with TeeJet DG 11002 VS. The highest spray mix deposition was obtained under 100% of salvínia dominance. However, the spray mix quantity decreased with increase of water hyacinth in the proportion and reached the lowest value when 25% of eared water moss plants were associated with 75% of water hyacinth plants. The presence of water lettuce did not influence spray mix deposition over eared water moss plants.

S.R. Marchi

2011-03-01

108

Stimulating productivity of hydroponic lettuce in controlled environments with triacontanol  

Science.gov (United States)

Triacontanol (1-triacontanol) applied as a foliar spray at 10(-7) M to 4-day-old, hydroponically grown leaf lettuce (Lactuca sativa L.) seedlings in a controlled environment increased leaf fresh and dry weight 13% to 20% and root fresh and dry weight 13% to 24% 6 days after application, relative to plants sprayed with water. When applied at 8 as well as 4 days after seeding, triacontanol increased plant fresh and dry weight, leaf area, and mean relative growth rate 12% to 37%. There was no benefit of repeating application of triacontanol in terms of leaf dry weight gain.

Knight, S. L.; Mitchell, C. A.

1987-01-01

109

Phylogenetic relationships of aroids and duckweeds (Araceae) inferred from coding and noncoding plastid DNA.  

Science.gov (United States)

Familial, subfamilial, and tribal monophyly and relationships of aroids and duckweeds were assessed by parsimony and Bayesian phylogenetic analyses of five regions of coding (rbcL, matK) and noncoding plastid DNA (partial trnK intron, trnL intron, trnL-trnF spacer) for exemplars of nearly all aroid and duckweed genera. Our analyses confirm the position of Lemna and its allies (formerly Lemnaceae) within Araceae as the well-supported sister group of all aroids except Gymnostachydoideae and Orontioideae. The last two subfamilies form the sister clade of the rest of the family. Monophyly of subfamilies Orontioideae, Pothoideae, Monsteroideae, and Lasioideae is supported, but Aroideae are paraphyletic if Calla is maintained in its own subfamily (Calloideae). Our results suggest expansion of the recently proposed subfamily Zamioculcadoideae (Zamioculcas, Gonatopus) to include Stylochaeton and identify problems in the current delimitation of tribes Anadendreae, Heteropsideae, and Monstereae (Monsteroideae), Caladieae/Zomicarpeae, and Colocasieae (Aroideae). Canalization of traits of the spathe and spadix considered typical of Araceae evolved after the split of Gymnostachydoideae, Orontioideae, and Lemnoideae. An association with aquatic habitats is a plesiomorphic attribute in Araceae, occurring in the helophytic Orontioideae and free-floating Lemnoideae, but evolving independently in various derived aroid lineages including free-floating Pistia (Aroideae). PMID:21632433

Cabrera, Lidia I; Salazar, Gerardo A; Chase, Mark W; Mayo, Simon J; Bogner, Josef; Dávila, Patricia

2008-09-01

110

Increase of starch accumulation in the duckweed Lemna minor under abiotic stress  

Directory of Open Access Journals (Sweden)

Full Text Available Abiotic stresses often result in suppression of photosynthesis and plant growth. Using the duckweed species Lemna minor and subjecting these plants to abiotic stress viz., (1 application of heavy metals, (2 application of salt (NaCl, and (3 lack of phosphate, we showed that photosynthesis was inhibited to a lesser degree than plant growth. This became evident by detecting the accumulation of starch under these conditions: (1 Cadmium ions and other heavy metals induced the accumulation of starch after 4 days of treatment at concentrations when growth was almost completely suppressed (e. g. 80 %. (2 Application of NaCl at a concentration of 150 mM also resulted in accumulation of starch but the highest level could be observed only after 7 days. (3 Depletion of phosphate in the growth medium had similar effects leading to starch accumulation after 14 days of treatment. Starch can accumulate to approximately 50% of dry mass under the three different conditions. We suggest the following common molecular mechanism: The stress factor suppresses growth more effectively than photosynthesis. The resulting surplus of carbohydrates is then stored as starch. This hypothesis has biotechnological relevance since stressors may be applied for increasing starch accumulation in duckweed and thus could be used to optimize bioethanol production from this aquatic crop.

K. SOWJANYA SREE

2014-06-01

111

Agronomic efficiency of intercropping tomato and lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Four experiments were carried out at the São Paulo State University, Brazil, with the aim of determining the agronomic viability of intercropping tomato and lettuce, under greenhouse conditions. The studied intercropping systems were established by transplanting lettuce at 0, 10, 20 and 30 days after transplanting (DAT tomato and by transplanting tomato at 0, 10, 20 and 30 DAT lettuce. Intercropped tomato and lettuce were evaluated during two seasons and compared to their sole cropping. The experimental design was a randomized complete block with nine treatments. The productivity and the classification of the tomato fruits were not influenced by having lettuce intercropped with it, but lettuce production was lowered when tomato was intercropped with it. The longer the delay in lettuce transplanting, the greater the reduction in its productivity. There was an effect of cropping season on the extent of the agronomic advantage of intercropping over sole cropping. In the first cropping season, intercropping established by transplanting lettuce during the interval between 30 days before up to 20 DAT tomato yielded land use efficiency (LUE indices of 1.63 to 2.22. In the second period, intercropping established with the transplanting of lettuce up to 30 days before tomato yielded LUE indices of 1.57 to 2.05.Quatro experimentos foram conduzidos na Unesp, Brasil, com o objetivo de determinar a viabilidade agronômica de cultivos consorciados de alface e tomate em ambiente protegido. Consórcios estabelecidos por transplantes da alface aos 0, 10, 20 e 30 dias após o transplante (DAT do tomate e de tomate aos 0, 10, 20 e 30 DAT da alface, foram avaliados em duas épocas e comparados às suas monoculturas. Cada experimento foi conduzido em delineamento de blocos ao acaso, com nove tratamentos. Verificou-se que a produtividade do tomate e a classificação dos frutos não foram influenciadas pela alface, mas a produção da alface foi menor em consórcio. Quanto mais atrasado o transplante da alface menor foi a sua produtividade. Houve efeito de época de cultivo sobre a dimensão da vantagem agronômica do consórcio sobre a monocultura. Na primeira época de cultivo, os consórcios estabelecidos com o transplante da alface de 30 dias antes e até 20 dias após o transplante do tomate proporcionaram índices de eficiência do uso da área (EUA de 1,63 a 2,22. Na segunda época, os consórcios estabelecidos com o transplante da alface antes do tomate, em até 30 dias, proporcionaram índices EUA de 1,57 a 2,05.

Arthur B. Cecílio Filho

2011-09-01

112

Comparison of lettuce diseases and yield under subsurface drip and furrow irrigation.  

Science.gov (United States)

ABSTRACT Subsurface drip and furrow irrigation were compared on lettuce (Lactuca sativa) cvs. Salinas and Misty Day for yield and incidence and severity of three important diseases of lettuce in the Salinas Valley, CA. Experiments were conducted between 1993 and 1995 during the spring and fall seasons. The diseases examined included lettuce drop (Sclerotinia minor), downy mildew (Bremia lactucae), and corky root (Rhizomonas suberifaciens). Replicated plots of subsurface drip and furrow irrigation were arranged in a randomized complete-block design. All plants were inoculated with S. minor at the initiation of the experiment during the 1993 spring season. Plots were not inoculated for downy mildew and corky root during any season nor were the plots reinoculated with S. minor. During each season, all plots were sprinkler irrigated until thinning, and subsequently, the irrigation treatments were begun. The furrow plots were irrigated once per week, and the drip plots received water twice per week. The distribution of soil moisture at two soil depths (0 to 5 and 6 to 15 cm) at 5, 10, and 15 cm distance on either side of the bed center in two diagonal directions was significantly lower in drip-irrigated compared with furrow-irrigated plots. Plots were evaluated for lettuce drop incidence and downy mildew incidence and severity at weekly intervals until harvest. Corky root severity and yield components were determined at maturity. Lettuce drop incidence and corky root severity were significantly lower and yields were higher in plots under subsurface drip irrigation compared with furrow irrigation, regardless of the cultivar, except during the 1994 fall season. Incidence and severity of downy mildew were not significantly different between the two irrigation methods throughout the study. The differential microclimates created by the two irrigation treatments did not affect downy mildew infection, presumably because the mesoclimate is usually favorable in the Salinas Valley. Subsurface drip irrigation is a viable, long-term strategy for soilborne disease management in lettuce in the Salinas Valley. PMID:18945057

Subbarao, K V; Hubbard, J C; Schulbach, K F

1997-08-01

113

Clonal Expansion of Verticillium dahliae in Lettuce.  

Science.gov (United States)

ABSTRACT Few studies in population biology have documented how structure and diversity of pathogens evolve over time at local scales. With the historical samples of Verticillium dahliae available from lettuce, we investigated the structure and diversity of this pathogen in time and space. Three hundred twenty-nine V. dahliae isolates from lettuce fields collected over 18 years were characterized with polymorphic microsatellite markers and polymerase chain reaction tests for race and mating type. Genetic variation within and among commercial lettuce fields in a single season was also investigated using an additional 146 isolates. Sixty-two haplotypes (HTs) were observed among the 329 isolates. A single HT was frequently observed over multiple years and locations (61.40%). Genetic diversity, allelic richness, and private allelic richness suggested a relatively recent clonal expansion. Race 1 (93.63%) and MAT1-2-1 (99.69%) were overwhelmingly represented among the isolates. Linkage disequilibrium was significant (P < 0.001) for all populations, suggesting limited sexual recombination in the sampled populations from lettuce. Populations from 2006, 2009, and 2010 had higher numbers of unique HTs, implying a recent introduction of novel HTs. We conclude that V. dahliae population from lettuce evaluated in this study is expanding clonally, consistent with an asexually reproducing pathogen, and the movement of clonal genotypes locally occurs over time. PMID:24476528

Gurung, S; Short, D P G; Atallah, Z K; Subbarao, K V

2014-06-01

114

Stability of bovine coronavirus on lettuce surfaces under household refrigeration conditions.  

Science.gov (United States)

Fecal suspensions with an aerosol route of transmission were responsible for a cluster of severe acute respiratory syndrome (SARS) cases in 2003 in Hong Kong. Based on that event, the World Health Organization recommended that research be implemented to define modes of transmission of SARS coronavirus through sewage, feces, food and water. Environmental studies have shown that animal coronaviruses remain infectious in water and sewage for up to a year depending on the temperature and humidity. In this study, we examined coronavirus stability on lettuce surfaces. A cell culture adapted bovine coronavirus, diluted in growth media or in bovine fecal suspensions to simulate fecal contamination was used to spike romaine lettuce. qRT-PCR detected viral RNA copy number ranging from 6.6 × 10? to 1.7 × 10? throughout the experimental period of 30 days. Whereas infectious viruses were detected for at least 14 days, the amount of infectious virus varied, depending upon the diluent used for spiking the lettuce. UV and confocal microscopic observation indicated attachment of residual labeled virions to the lettuce surface after the elution procedure, suggesting that rates of inactivation or detection of the virus may be underestimated. Thus, it is possible that contaminated vegetables may be potential vehicles for coronavirus zoonotic transmission to humans. PMID:22265299

Mullis, Lisa; Saif, Linda J; Zhang, Yongbin; Zhang, Xuming; Azevedo, Marli S P

2012-05-01

115

Production of iceberg lettuce using mulches  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mulches bring several benefits to lettuce cultivation. This work evaluated the effect of mulches on the cultivation of iceberg lettuce, cv. Lucy Brown. The treatment plots were: 1- no mulch and no weed control (control); 2- no mulch and weed control every 15 days; 3- sugarcane bagasse mulch of 2 cm thickness; 4- black plastic mulch; 5- double-faced plastic mulch (silver/black). Data were collected in regard to plant cycle when in the field, amount of chlorophyll in the leaves, productivity (i...

2001-01-01

116

Effect of electric pulse charged to culture soil on improvement of nutritional soil condition and growth of lettuce (Lactuca sative L.  

Directory of Open Access Journals (Sweden)

Full Text Available This study is intended to measure variations of nutritional soil condition and mass spectrometric patterns to describe the specific effects of electric pulse charged to culture soil which induced an increase of lettuce growth. In a previous study, lettuce cultivated in an electrically pulsed culture soil (EPCS grew more actively than those in a conventional culture soil (CCS. Lettuce growth increased about 20% more in EPCS than CCS during cultivated for 21 days in this study. Content of nutrient salts and minerals varied in CCS and EPCS when assayed after the period of lettuce cultivation. Ammonium content in CCS was higher than that in EPCS but nitrate content was opposite of the ammonium. Inorganic N-compounds in EPCS was about 2.5 times higher than that in CCS. Content of phosphate in CCS increased greatly by lettuce cultivation but was about 2 times lower than that in EPCS. Contents of minerals in EPCS were relatively higher than those in CCS excepting Fe. Patterns of chromatography and mass spectrometry for water soluble compounds extracted from lettuces cultivated in EPCS were considerably different from those in CCS. Conclusively, electric pulse caused increased lettuce growth, improved nutritional soil conditions, and varied mass spectrometric patterns.

Jun Young Yi

2012-11-01

117

Internalisation potential of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium and Staphylococcus aureus in lettuce seedlings and mature plants.  

Science.gov (United States)

The internalisation potential of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7 and Salmonella enterica subsp. enterica serovar Typhimurium in lettuce was evaluated using seedlings grown in vermiculite in seedling trays as well as hydroponically grown lettuce. Sterile distilled water was spiked with one of the four human pathogenic bacteria (10(5) CFU/mL) and used to irrigate the plants. The potential for pathogen internalisation was investigated over time using light microscopy, transmission electron microscopy and viable plate counts. Additionally, the identities of the pathogens isolated from internal lettuce plant tissues were confirmed using polymerase chain reaction with pathogen-specific oligonucleotides. Internalisation of each of the human pathogens was evident in both lettuce seedlings and hydroponically grown mature lettuce plants. To our knowledge, this is the first report of S. aureus internalisation in lettuce plants. In addition, the levels of background microflora in the lettuce plants were determined by plate counting and the isolates identified using matrix-assisted laser ionisation-time of flight (MALDI-TOF). Background microflora assessments confirmed the absence of the four pathogens evaluated in this study. A low titre of previously described endophytes and soil inhabitants, i.e., Enterobacter cloacae, Enterococcus faecalis, Lysinibacillus fusiformis, Rhodococcus rhodochrous, Staphylococcus epidermidis and Staphylococcus hominis were identified. PMID:23708570

Standing, Taryn-Ann; du Plessis, Erika; Duvenage, Stacey; Korsten, Lise

2013-06-01

118

Exposure to radiofrequency radiation induces oxidative stress in duckweed Lemna minor L  

International Nuclear Information System (INIS)

Widespread use of radiofrequency radiation emitting devices increased the exposure to electromagnetic fields (EMFs) from 300 MHz to 300 GHz. Various biological effects of exposure to these fields have been documented so far, but very little work has been carried out on plants. The aim of the present work was to investigate the physiological responses of the plant Lemna minor after exposure to radiofrequency EMFs, and in particular, to clarify the possible role of oxidative stress in the observed effects. Duckweed was exposed for 2 h to EMFs of 400 and 900 MHz at field strengths of 10, 23, 41 and 120 V m-1. The effect of a longer exposure time (4 h) and modulation was also investigated. After exposure, parameters of oxidative stress, such as lipid peroxidation, H2O2 content, activities and isoenzyme pattern of antioxidative enzymes as well as HSP70 expression were evaluated. At 400 MHz, lipid peroxidation and H2O2 content were significantly enhanced in duckweed exposed to EMFs of 23 and 120 V m-1 while other exposure treatments did not have an effect. Compared to the controls, the activities of antioxidative enzymes showed different behaviour: catalase (CAT) activity increased after most exposure treatments while pyrogallol (PPX) and ascorbate peroxidase (APX) activities were not changed. Exceptions were reduced PPX and APX activity after longer exposure at 23 V m-1 and increased PPX activity after exposures at 10 and 120 V m-1. By contrast, at 900 MHz almost all exposure treatments significantly increased level of lipid peroxidation and H2O2 content but mostly decreased PPX activity and did not affect CAT activity. Exceptions were exposures to a modulated field and to the field of 120 V m-1 which increased PPX and CAT activity. At this frequency APX activity was significantly decreased after exposure at 10 V m-1 and longer exposure at 23 V m-1 but it increased after a shorter exposure at 23 V m-1. At both frequencies no differences in isoenzyme patterns of antioxidative enzymes or HSP70 level were found between control and exposed plants. Our results showed that non-thermal exposure to investigated radiofrequency fields induced oxidative stress in duckweed as well as unspecific stress responses, especially of antioxidative enzymes. However, the observed effects markedly depended on the field frequencies applied as well as on other exposure parameters (strength, modulation and exposure time). Enhanced lipid peroxidation and H2O2 content accompanied by diminished antioxidative enzymes activity caused by exposure to investigated EMFs, especially at 900 MHz, indicate that oxidative stress could partly be due to changed activities of antioxidative enzymes

2007-12-15

119

Water use and crop coefficient of subsurface drip-irrigated lettuce in Central Arizona Demanda hídrica e coeficiente de cultura da alface irrigada por gotejamento sub-superficial na região central do Arizona  

Directory of Open Access Journals (Sweden)

Full Text Available A two year field study (1996/97 and 1997/98 growing seasons was carried out at the Maricopa Agricultural Center (33º04'07" N; 111º57'18" W of the University of Arizona, USA, to investigate the water use and to derive Kc's for subsurface drip-irrigated head lettuce grown in small weighable lysimeters. Measurement periods ranged from 480 to 1100 ºC-day (96/97 and from 439 to 1098 ºC-day (97/98. These intervals corresponded essentially to the second half of the crop cycle which amounted to a 1100 ºC-day, on average. The lysimeters were weighed periodically and the computation of the water balance revealed an average water use of 117 mm. Basal crop Kc was expressed as a function of cumulative growing degree days following a multiple linear regression procedure in which the data were fitted with a Fourier sine series model with up to six coefficients. Two-year Kc curves were obtained based on the Hargreaves, FAO Penman and FAO Penman-Monteith equations and compared to the AZSCHED (AriZona SCHEDuling irrigation package. Predicted Kc peaked 0.88, 0.80 and 0.81 with the Hargreaves, FAO Penman, FAO Penman-Monteith equations, respectively, in the range of 1000 to 1050 ºC-day, in contrast to AZSCHED which predicted the peak Kc to be 1.01 at 1150 ºC-day.Um estudo conduzido na Fazenda Experimental Maricopa (33º04'07" N; 111º57'18" W, pertencente à Universidade do Arizona, USA, nos anos agrícolas de 1996/97 e 1997/98, objetivou determinar o uso de água e derivar coeficientes de cultura (Kc da alface de cabeça irrigada por gotejamento subsuperficial e cultivada em lisímetros de pesagem intermitente. O período de medições, expresso em graus-dia acumulados, variou de 480 a 1100 ºC-dia em 96/97 e de 439 a 1098 ºC-dia em 97/98. Esses intervalos corresponderam à segunda metade do ciclo da cultura, sendo que até a colheita somou-se uma média de 1100 ºC-dia. Os lisímetros eram pesados periodicamente e o balanço hídrico revelou um consumo médio de 117 mm, naqueles períodos. O Kc basal foi relacionado com o acúmulo de graus-dia através de regressão múltipla, seguindo um modelo dado por uma série seno de Fourier, com até seis coeficientes. As curvas de Kc foram determinadas com base nos métodos de Hargreaves, FAO Penman e FAO Penman-Monteith, para cálculo da ETo e comparadas por aquela gerada pelo programa AZSCHED (AriZona SCHEDuling de manejo da irrigação. Valores máximos de Kc estimados foram 0,88 (método de Hargreaves, 0,80 (FAO Penman e 0,81 (FAO Penman-Monteith no intervalo de 1000 a 1050 ºC dia, inferiores a 1,01 em 1150 ºC dia, que é o máximo Kc previsto pelo programa AZSCHED.

Aureo S. de Oliveira

2005-03-01

120

THE OCCURRENCE OF APIOSE IN LEMNA (DUCKWEED) AND OTHER ANGIOSPERMS.  

Science.gov (United States)

1. The branched-chain pentose apiose reacts with the benzidine-trichloroacetic acid reagent on paper chromatograms to give a yellow spot with.an intense white fluorescence in ultraviolet light; on chromatograms developed with butanol-acetic acid-water this spot lies between fucose and rhamnose. 2. Examination of paper chromatograms of hydrolysates of whole plant material has shown the presence of a substance with these properties in a wide variety of species. 3. Among the plants examined two members of the Lemnaceae (Lemna minor and Wolffia arrhiza) were found to be especially rich sources, comparable with Posidonia australis (Bell, Hardwick, Isherwood & Cahn, 1954). 4. Measurements of the apiose content of fractions derived from Lemna have shown that the sugar is present at a concentration of about 4% in the holocellulose, and part of this is retained in the alpha-cellulose left by extraction with 24% (w/v) potassium hydroxide containing borate. PMID:14340070

DUFF, R B

1965-03-01

 
 
 
 
121

Characterisation of lettuce virus X, a new potexvirus infecting lettuce in Iran.  

Science.gov (United States)

A virus with flexuous rod-shaped particle morphology was found in samples from lettuce during a survey of viruses infecting lettuce in Tehran province in Iran. This virus was subjected to a complete analysis of its biological and molecular features. The entire nucleotide sequence of the virus was determined, revealing a polyadenylated ssRNA genome consisting of 7,212 nucleotides [without poly (A) tail] and possessing an organization typical for potexviruses. Comparative genome analysis showed that the lettuce virus is closely related to Alstroemeria virus X, narcissus mosaic virus and asparagus virus 3. Based on particle morphology, physico-chemical properties and the complete genome sequence, this virus is a member of a new species in the genus Potexvirus, for which the name lettuce virus X (LeVX) is proposed. Biological assays using an infectious cDNA clone and a wild-type isolate of LeVX revealed that the virus, despite reaching high concentrations in all lettuce cultivars tested, does not cause symptoms in lettuce. PMID:18807116

Dizadji, A; Koohi-Habibi, M; Izadpanah, K; Dietrich, C; Mossahebi, G H; Winter, S

2008-01-01

122

Effect of Wastewater from Quetta City on the Germination and Seedling Growth of Lettuce (Lactuca sativa L.)  

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This study was concerned to the effects of 5 various level of polluted water of three different localities of Quetta city (viz., Chiltan Ghee Mill, Chiltan Town and Zarghoon Town) on seed germination and seedling growth of Lettuce (Lactuca sativa L.). The Lettuce was taken as a test plant and its seeds were germinated in petri-dishes in the Laboratory. Results showed that seed germination was significantly reduced and delayed as the concentration of wastewater (domestic and industrial ...

Zahoor Ahmad Bazai; Abdul Kabir Khan Achakzai

2006-01-01

123

Contamination of lettuce with antibiotic resistant E. coli after slurry application  

DEFF Research Database (Denmark)

Due to disease outbreaks associated with contaminated vegetables it has been speculated to what extent this may be linked with application of animal manure as fertilizer, which is particularly practiced in organic vegetable production where conventional fertilizers are prohibited. A field survey was therefore performed to assess the survival and transfer of antibiotic-resistant E. coli from animal manure to lettuces, with E. coli serving as an indicator of bacterial enteric pathogens. Animal slurry was applied to 3 Danish fields prior to planting of lettuce seedlings, then 5-8 weeks later at the normal time of harvest, inner and outer leafs of 10 lettuce heads were pooled into one sample unit with a total of 50 pools per field. Additionally, in one field, 15 soil samples were collected weekly until the harvest time. E. coli was enumerated by plating 1 mL of 10-fold serial dilutions of 5 g of homogenized sample material, i.e. manure, soil and lettuce onto PetrifilmTM Select E. coli count plates (3M) containing16 mg/L streptomycin or 16 mg/L ampicilin or no antibiotics. Plates were then incubated 24 h at 44°C. Selected isolates of E. coli (n=83) from slurry, soil and lettuce were analysed by PFGE DNA typing for further discrimination. The slurry applied to the fields contained 3.0-4.5 Log10 E. coli CFU/g and resistant E. coli ranged from 1.0 to 4.4 Log10 E. coli CFU/g with particular high numbers of streptomycin resistant E. coli in conventional pig slurry (field 1) opposed to organic cow slurry (field 2 and 3). E. coli was found in 36-54% of the pooled lettuce samples at the three fields with a detection limit of 10 CFU/g and 10-18% and 0-2% of pools had streptomycin and ampicilin resistant E. coli, respectively. Unexpectedly, the highest percentage of lettuce pools with antibiotic resistant E. coli were found on fields fertilized with organic cow slurry where 0.1-5% of E. coli was resistant opposed to 5-50% resistant E. coli in conventional slurry. Numbers of E. coli in 14-20% of pooled lettuce samples exceeded a satisfactory microbiological hygiene criteria level of 100 CFU/g. The numbers of resistant E. coli for both antibiotics were approximately 10-fold lower than the sensitive E. coli. At the time of harvest, the numbers of E. coli in 5 of 15 soil samples were reduced below the detection limit and no samples exceeded 100 CFU/g, which was in contrast to the lettuce samples, where 20% of faecally contaminated samples contained >100 E. coli/g. This indicates that fecal contamination of crops originated from alternative sources such as contaminated water or wildlife. This was supported by genotyping of E. coli, where half of the 21 PFGE types were found on single occasions in either soil or lettuce, whereas the other half was found both in slurry and lettuce indicating a possible transfer.

Jensen, Annette Nygaard; Storm, Christina

2011-01-01

124

Stimulation of nitrogen removal in the rhizosphere of aquatic duckweed by root exudate components.  

Science.gov (United States)

Plants can stimulate bacterial nitrogen (N) removal by secretion of root exudates that may serve as carbon sources as well as non-nutrient signals for denitrification. However, there is a lack of knowledge about the specific non-nutrient compounds involved in this stimulation. Here, we use a continuous root exudate-trapping system in two common aquatic duckweed species, Spirodela polyrrhiza (HZ1) and Lemna minor (WX3), under natural and aseptic conditions. An activity-guided bioassay using denitrifying bacterium Pseudomonas fluorescens showed that crude root exudates of the two species strongly enhanced the nitrogen-removal efficiency (NRE) of P. fluorescens (P acidic, neutral and basic fractions, a pronounced stimulatory effect was also observed for the neutral fractions from HZ1 and WX3 under both conditions, whereas the acidic fractions from WX3 displayed an inhibitory effect. Analysis of the active fractions using gas chromatography/mass spectrometry (GC/MS) revealed that duckweed released fatty acid methyl esters and fatty acid amides, specifically: methyl hexadecanoate, methyl (Z)-7-hexadecenoate, methyl dodecanoate, methyl-12-hydroxystearate, oleamide, and erucamide. Methyl (Z)-7-hexadecenoate and erucamide emerged as the effective N-removal stimulants (maximum stimulation of 25.9 and 33.4%, respectively), while none of the other tested compounds showed stimulatory effects. These findings provide the first evidence for a function of fatty acid methyl esters and fatty acid amides in stimulating N removal of denitrifying bacteria, affording insight into the "crosstalk" between aquatic plants and bacteria in the rhizosphere. PMID:24271005

Lu, Yufang; Zhou, Yingru; Nakai, Satoshi; Hosomi, Masaaki; Zhang, Hailin; Kronzucker, Herbert J; Shi, Weiming

2014-03-01

125

Effect of the Municipal Garbage on the Growth of Lettuce  

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Full Text Available Municipal Garbage (MG as a plant nutrient supply was evaluated. Some of the garbage was collected from Hail city, Kingdom of Saudi Arabia. The garbage was fermented partially after removing its contents of stones and metals. Lettuce plants were transplanted in five greenhouse pot experiments. In the first, a portion of the MG was mixed with a sandy soil at either 1, 2 or 3% before the transplanting. In the second, a portion of the MG was mixed with hydrochloric acid 0.1 Nat ratio of 1:2 for 15 days then extracted. The solid extracted portion was mixed with the sandy soil at 1, 2 , or 3%. A week after lettuce transplanting, a foliar spray technique was used to spray the HCl extract. In third and fourth experiments, the Coca Cola and the distilled water as extractants were used similarly to the second experiment. The fifth experiment was fertilized using the conventional rate of NPK fertilization ( control. The lettuce plants were harvested after two months from the experiment initiation then soil pH and total soluble salts were determined in 1:2.5 soil water extract. The pH and total soluble salt values among the treatments were not significant. Growth parameters such as the total fresh weight, shoot fresh weight, shoot dry weight and the dry matter percentage were determined. The results of the former three parameters increased as the rate of MG increased under the condition of the first four experiments. In addition, these parameters were great under the MG experiments in comparison to the control experiment. The dry matter percentages using 2% rate of MG were the greatest under all experiments except the Coca Cola experiment. This percentages increased as the rate of MG increased under the Coca Cola experiment condition. All of the growth parameters were the greatest under the condition of distilled water experiment among all of the experiments. The results of the study encourage using the water extract of MG as a source for plant nutrients and the extracted portion as a soil conditioner.

K.N. Al-Redhaiman

2003-01-01

126

Deposição de calda de pulverização sobre plantas de salvínia em função de pontas de pulverização e arranjos populacionais entre plantas de Aguapé e Alface-D'Água / Spray deposition on water fern plants in function of nozzle tips and population arrangements with water Hyacinth and Water Lettuce plants  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Este trabalho teve como objetivo avaliar o depósito de calda pulverizada por dois tipos de pontas de pulverização sobre plantas de Salvinia auriculata dispostas em diferentes arranjos populacionais com plantas de Eichhornia crassipes e Pistia stratiotes. Um experimento foi conduzido em condições de [...] caixas-d'água em delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 2 x 8, sendo dois tipos de pontas de pulverização (ConeJet TXVK-8 e TeeJet DG 11002 VS) e oito proporções entre as plantas aquáticas, a saber: dominância total da área de cobertura da caixa-d'água pelas plantas de salvínia (100%); e as proporções entre plantas de salvínia e de aguapé ou alface-d'água a 75%:25%, 50%:50% e 25%:75%. Também foi utilizada uma densidade tripla, na qual as três espécies estiveram igualmente dispostas na proporção de 33%. Soluções dos corantes Amarelo Tartrasina FDC-5 a 3.500 ppm e Azul Brilhante FDC-1 a 1.000 ppm foram utilizadas como traçadores para as pontas TXVK-8 e DG 11002VS, respectivamente. A pulverização das soluções foi efetuada na mesma unidade experimental, com intervalo de 30 minutos entre si, com auxílio de um pulverizador costal pressurizado com CO2, calibrado de modo que proporcionasse volume de aplicação aproximado de 200 L ha-1. Não foram observadas diferenças estatísticas entre os tipos de pontas de pulverização nas diferentes proporções estudadas, exceto para depósitos totais de calda de pulverização nas plantas na condição de dominância total da salvínia, uma vez que a ponta ConeJet TXVK-8 foi superior à TeeJet DG 11002 VS. Os valores dos depósitos diminuíram com o aumento da proporção de plantas de aguapé na associação e foram na condição em que 25% de plantas de salvínia estiveram associadas a 75% de plantas de aguapé. A presença da espécie alface-d'água não influenciou a deposição de gotas sobre as folhas de salvínia. Abstract in english This study aimed to evaluate two types of spray tips (ConeJet TXVK-8 and TeeJet DG 11002 VS) and the amount of spray mix deposited on Salvinia auriculata plants organized under different population arrangements with Eichhornia crassipes and Pistia stratiotes plants. In addition to a full-dominance p [...] roportion over the area, corresponding to 100% cover of the water tank by eared water moss plants, arrangements with either water hyacinth or water lettuce were made at 75%:25%, 50%:50%, and 25%:75%. A triple density, in which the three species were equally disposed at a 33.33% proportion, was also used. Dye solutions of FD&C Yellow no. 5 at 3,500 ppm and FD&C Blue no.1 at 1,000 ppm were used, as spraying tracers for TXVK-8 and DG 11002 VS nozzles, respectively. Both solutions were sprayed at the same plot within a 30-minute interval each, through a CO2 pressured backpack, calibrated to deliver a spray volume of around 200 L ha-1. The total spray deposits were estimated in mL per plant and the unit deposits in mL cm² of foliar surface. No significant differences were observed between the nozzle tips used at different population arrangements, except total spray mix deposited on plants at 100% of eared water moss dominance proportion, with ConeJet TXVK-8, providing superior spray mix deposition, compared with TeeJet DG 11002 VS. The highest spray mix deposition was obtained under 100% of salvínia dominance. However, the spray mix quantity decreased with increase of water hyacinth in the proportion and reached the lowest value when 25% of eared water moss plants were associated with 75% of water hyacinth plants. The presence of water lettuce did not influence spray mix deposition over eared water moss plants.

Marchi, S.R.; Martins, D.; Costa, N.V.; Carbonari, C.A.; Silva, J.R.V..

127

Evidence for Lettuce big-vein associated virus as the causal agent of a syndrome of necrotic rings and spots in lettuce  

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Lettuce big-vein associated virus (LBVaV, genus Varicosavirus) was shown to be responsible for characteristic necrotic symptoms observed in combination with big-vein symptoms in lettuce breeding lines when tested for their susceptibility to lettuce big-vein disease (BVD) using viruliferous Olpidium virulentus spores in a nutrient film technique (NFT) system. Lettuce plants showing BVD are generally infected by two viruses: Mirafiori lettuce big-vein virus (MiLBVV, genus Ophiovirus) and LBVaV....

Verbeek, M.; Dullemans, A. M.; Bekkum, P. J.; Vlugt, R. A. A.

2012-01-01

128

Virus diseases in lettuce in the Mediterranean basin.  

Science.gov (United States)

Lettuce is frequently attacked by several viruses causing disease epidemics and considerable yield losses along the Mediterranean basin. Aphids are key pests and the major vectors of plant viruses in lettuce fields. Lettuce mosaic virus (LMV) is probably the most important because it is seed-transmitted in addition to be transmissible by many aphid species that alight on the crop. Tomato spotted wilt virus (TSWV) is another virus that causes severe damage since the introduction of its major vector, the thrips Frankliniella occidentalis. In regions with heavy and humid soils, Lettuce Mirafiori big-vein virus (LMBVV) can also produce major yield losses. PMID:22682170

Moreno, Aranzazu; Fereres, Alberto

2012-01-01

129

Potential use of duckweed based anaerobic digester effluent as a feed source for heterotrophic growth of micro-algae  

Science.gov (United States)

Finding an alternative source of energy for the growing world's demand is a challenging task being considered by many scientists. Various types of renewable energy alternatives are being investigated by researchers around the world. The abundance of duckweed (i.e., Lemna and Wolfia sp.) in wetlands and wastewater lagoons, their rapid growth, and their capacity for nutrient, metal and other contaminant removal from wastewater suggests their potential as an inexpensive source of biomass for biofuel production. Another source of biomass for biofuel and energy production is micro-algae. The large-scale growth of micro-algae can potentially be achieved in a smaller footprint and at a higher rate and lower cost via heterotrophic growth compared to autotrophic growth for specific species that can grow under both conditions. Here we describe two types of research. First, two lab-scale, 5 L anaerobic digesters containing municipal raw wastewater that were set up, maintained and monitored over the course of 6 months using duckweed as the feed source. The pH, salinity, amount of gas production and gas composition were measured on a daily basis. The results from these measurements show that duckweed can be used as a good source of biofuel production in the form of methane gas. The second set of reactors consisted of two 1 L batch fed reactors containing algae (Chlorella vulgaris) grown in the lab environment heterotrophically. The pH and DO were monitored on a daily basis in order to investigate their effect on algae growth. Lipid analysis of the harvested algal biomass was done to investigate the efficiency of harvestable biofuel products. A nutrient solution containing glucose as an energy source was used as the initial feed solution, and the potential substitution of the glucose solution with the organic carbon residue from the duckweed digester effluent was investigated. Methane production, carbon stabilization, and gas composition results from the duckweed fed anaerobic digesters, and the growth and biolipid production of heterotrophic micro-algae fed pure substrate versus residual digester effluent carbon are discussed in detail in this study.

Ahmadi, L.; Dupont, R.

2013-12-01

130

Exposure to radiofrequency radiation induces oxidative stress in duckweed Lemna minor L  

Energy Technology Data Exchange (ETDEWEB)

Widespread use of radiofrequency radiation emitting devices increased the exposure to electromagnetic fields (EMFs) from 300 MHz to 300 GHz. Various biological effects of exposure to these fields have been documented so far, but very little work has been carried out on plants. The aim of the present work was to investigate the physiological responses of the plant Lemna minor after exposure to radiofrequency EMFs, and in particular, to clarify the possible role of oxidative stress in the observed effects. Duckweed was exposed for 2 h to EMFs of 400 and 900 MHz at field strengths of 10, 23, 41 and 120 V m{sup -1}. The effect of a longer exposure time (4 h) and modulation was also investigated. After exposure, parameters of oxidative stress, such as lipid peroxidation, H{sub 2}O{sub 2} content, activities and isoenzyme pattern of antioxidative enzymes as well as HSP70 expression were evaluated. At 400 MHz, lipid peroxidation and H{sub 2}O{sub 2} content were significantly enhanced in duckweed exposed to EMFs of 23 and 120 V m{sup -1} while other exposure treatments did not have an effect. Compared to the controls, the activities of antioxidative enzymes showed different behaviour: catalase (CAT) activity increased after most exposure treatments while pyrogallol (PPX) and ascorbate peroxidase (APX) activities were not changed. Exceptions were reduced PPX and APX activity after longer exposure at 23 V m{sup -1} and increased PPX activity after exposures at 10 and 120 V m{sup -1}. By contrast, at 900 MHz almost all exposure treatments significantly increased level of lipid peroxidation and H{sub 2}O{sub 2} content but mostly decreased PPX activity and did not affect CAT activity. Exceptions were exposures to a modulated field and to the field of 120 V m{sup -1} which increased PPX and CAT activity. At this frequency APX activity was significantly decreased after exposure at 10 V m{sup -1} and longer exposure at 23 V m{sup -1} but it increased after a shorter exposure at 23 V m{sup -1}. At both frequencies no differences in isoenzyme patterns of antioxidative enzymes or HSP70 level were found between control and exposed plants. Our results showed that non-thermal exposure to investigated radiofrequency fields induced oxidative stress in duckweed as well as unspecific stress responses, especially of antioxidative enzymes. However, the observed effects markedly depended on the field frequencies applied as well as on other exposure parameters (strength, modulation and exposure time). Enhanced lipid peroxidation and H{sub 2}O{sub 2} content accompanied by diminished antioxidative enzymes activity caused by exposure to investigated EMFs, especially at 900 MHz, indicate that oxidative stress could partly be due to changed activities of antioxidative enzymes.

Tkalec, Mirta [Department of Botany, Division of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, HR-10000 Zagreb (Croatia)], E-mail: mtkalec@zg.biol.pmf.hr; Malaric, Kresimir [Faculty of Electrical Engineering and Computing, University of Zagreb, Unska 3, HR-10000 Zagreb (Croatia); Pevalek-Kozlina, Branka [Department of Botany, Division of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, HR-10000 Zagreb (Croatia)

2007-12-15

131

A simple and efficient method for testing Lettuce mosaic virus resistance in in vitro cultivated lettuce.  

Science.gov (United States)

The potential of a new in vitro inoculation and propagation method developed for Lettuce mosaic virus (LMV) on lettuce (Lactuca sativa L.) was evaluated by studying LMV infection on in vitro cultivated seedlings or on newly regenerated plantlets. Lettuce cultivars differing by their LMV-resistance status were inoculated with various natural LMV isolates as well as with Green Fluorescent Protein (GFP)-tagged recombinant virus isolates. A good correlation was observed between the known resistance status of the cultivars and the results obtained by in vitro screening. The results show that this resistance assay can be greatly improved by the use of GFP-tagged virus isolates. The main advantages of this method are reduced space requirements and an improved environmental safety, especially for the handling of recombinant virus, of quarantine virus or of transgenic plants. PMID:14738978

Mazier, Marianne; German-Retana, Sylvie; Flamain, Fabrice; Dubois, Vincent; Botton, Emmanuel; Sarnette, Vérane; Le Gall, Olivier; Candresse, Thierry; Maisonneuve, Brigitte

2004-03-15

132

Use of propolis in the sanitization of lettuce.  

Science.gov (United States)

The present study aimed to determine the effectiveness of propolis in reducing the microbial load in ready-to-eat (RTE) and fresh whole head (FWH) lettuces (Lactuca sativa L.) type Batavia. Two sanitizing solutions were employed: sodium hypochlorite (SH) and propolis (PS), during 15 and 30 min. Tap water (TW) was used as a control. Regarding the mean reduction on aerobic mesophiles, psychrotrophic and fecal coliforms, the SH and PS treatments showed the same pattern of variation. In all cases, PS was slightly more effective in the microbiological reduction in comparison with commercial SH. Reductions between two and three log cycles were obtained with PS on aerobic mesophiles and psychrotrophic counts. The information obtained in the present study can be used to evaluate the potential use of propolis as product for sanitizing other vegetables and for developing other food preservation technologies, with impact on human health. PMID:25007823

Feás, Xesús; Pacheco, Lazaro; Iglesias, Antonio; Estevinho, Leticia M

2014-01-01

133

Alternative sanitization methods for minimally processed lettuce in comparison to sodium hypochlorite  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Lettuce is a leafy vegetable widely used in industry for minimally processed products, in which the step of sanitization is the crucial moment for ensuring a safe food for consumption. Chlorinated compounds, mainly sodium hypochlorite, are the most used in Brazil, but the formation of trihalomethane [...] s from this sanitizer is a drawback. Then, the search for alternative methods to sodium hypochlorite has been emerging as a matter of great interest. The suitability of chlorine dioxide (60 mg L-1/10 min), peracetic acid (100 mg L-1/15 min) and ozonated water (1.2 mg L-1 /1 min) as alternative sanitizers to sodium hypochlorite (150 mg L-1 free chlorine/15 min) were evaluated. Minimally processed lettuce washed with tap water for 1 min was used as a control. Microbiological analyses were performed in triplicate, before and after sanitization, and at 3, 6, 9 and 12 days of storage at 2 ± 1 ºC with the product packaged on LDPE bags of 60 µm. It was evaluated total coliforms, Escherichia coli, Salmonella spp., psicrotrophic and mesophilic bacteria, yeasts and molds. All samples of minimally processed lettuce showed absence of E. coli and Salmonella spp. The treatments of chlorine dioxide, peracetic acid and ozonated water promoted reduction of 2.5, 1.1 and 0.7 log cycle, respectively, on count of microbial load of minimally processed product and can be used as substitutes for sodium hypochlorite. These alternative compounds promoted a shelf-life of six days to minimally processed lettuce, while the shelf-life with sodium hypochlorite was 12 days.

Bachelli, Mara Lígia Biazotto; Amaral, Rívia Darla Álvares; Benedetti, Benedito Carlos.

134

Alternative disinfection techniques to extend the shelf life of minimally processed iceberg lettuce.  

Science.gov (United States)

Chlorination continues to be widely used by the fresh-cut industry for washing and disinfecting minimally processed fruits and vegetables. However, as chlorination has been reported to produce unhealthy by-products such as, chloramines and trihalomethanes, many alternative methods have been reported in the literature. This study examined the use of silver and hydrogen peroxide as possible alternative to chlorination. The results revealed an obvious bactericidal effect of hydrogen peroxide, silver and their combination on spoilage organisms. Combination of electrochemically generated silver (5 ppm) and hydrogen peroxide (0.4 ppm) caused significant (P lettuce. However, washing with chlorinated water (5 ppm) under same conditions revealed insignificant reduction in TPC (0.17 log), Pseudomonas (0.60 log), Enterobactericeae (0.15 log) or yeast and mould (0.81 log) counts. Results revealed also that both sources of silver (electrochemical silver and silver nitrate) have similar disinfecting effects, however, electrochemical silver maintained the quality of washed lettuce. PMID:20141938

Gopal, Angeline; Coventry, John; Wan, Jason; Roginski, Hubert; Ajlouni, Said

2010-04-01

135

Nutritional Efficiency of Phosphorus in Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available This work aimed to evaluate the efficiency of phosphorus absorption, translocation, and utilization in lettuce. A greenhouse experiment was arranged in a completely randomized design in a 5x2 factorial scheme to test five phosphorus doses (0, 100, 200, 300, and 500 mg dm-3 and two lettuce varieties (Lisa and Americana. The soil was incubated with limestone for pH correction. Following this procedure, a phosphate fertilization was carried and the lettuce seedlings were transplanted. Fertilization with nitrogen and potassium were applied as cover. Forty days after seedling transplantation, the plants were separated into root and aerial part to determine the following characteristics: aerial part dry matter (APDM; root dry matter (RDM; phosphorus content in the aerial part (PCAP; phosphorus content in the root (PCR; phosphorus accumulation in the aerial part (PAAP; phosphorus accumulation in the roots (PAR; phosphorus absorption efficiency (PAE; phosphorus translocation efficiency (PTE; phosphorus use efficiency in the aerial part (PUEAP and root-aerial part ratio (R/AP. The results obtained allowed to conclude that RDM and R/AP had a significant interaction between the varieties and the P doses, with Lisa presenting the highest values of these characteristics at the lowest doses evaluated. The characteristics PCAP, PAAP and PAE presented a significant difference between the varieties, with the Americana presenting the highest values. The characteristics PCAP, PAAP, EAP, APDM and PUEAP presented a significant difference between the P doses, with the highest values found at the dose of 500 mg dm-3, except for PUEAP, whose dose was 0 mg dm-3.

Ana Paula Almeida Bertossi

2013-07-01

136

Assessment of Escherichia coli O157:H7 transference from soil to iceberg lettuce via a contaminated field coring harvesting knife.  

Science.gov (United States)

The potential for lettuce field-coring harvesting knives to cross-contaminate lettuce heads with pathogens was evaluated. Rings and blades of the harvest knives artificially contaminated with Escherichia coli O157:H7 (EHEC), were used to core three successive heads of iceberg lettuce. The coring rings and blades were inoculated by dipping into soils containing EHEC at concentration ranges of 1-10(5) MPN/g soil. Factors that influenced EHEC transference from soil to iceberg lettuce via contaminated coring knife blade, included water content (WC) of clay and sandy soils, EHEC concentration, and degree of blade contact (stem, medium, and heavy) with edible tissue. High moisture content clay soil was positively associated with high pathogen transference. No EHEC were detected on any cut heads when clay soil contaminated with 10(5) MPN/g EHEC had WC of 20% or less, or when the knife blade was dipped into sandy soil contaminated with EHEC at the same level, regardless of percent WC. The extent to which the harvesting knife blade cut across edible lettuce tissues was also an important factor in the amount of pathogen transference that occurred. EHEC were detectable on first and second sequentially cut lettuce heads when medium-contact was made between knife blade and edible tissues and on all three sequentially cut lettuce heads using the heavy-contact cutting scenario, when the blade was contaminated with 10(4) cfu/g EHEC in clay soil (25% WC). However, when the blade, contaminated at the same soil EHEC level, was used to cut only the stem and had no contact with the edible portion of the lettuce head, no pathogen transference was detected. Under the current CIF harvesting practice, the cutting blade has a higher potential than the coring ring to be contaminated by the soil, but less opportunity to transfer pathogens to harvested lettuce. However, once contaminated, the coring ring has much higher potential than the blade to transfer pathogens to the harvested lettuce. PMID:22189025

Yang, Yang; Luo, Yaguang; Millner, Patricia; Turner, Ellen; Feng, Hao

2012-02-15

137

Study of Water Quality of Recirculated Water in Aquaponic Systems : Study of speciation of selected metals and characterization of the properties of natural organic matter  

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This thesis describes an extensive study on how water quality changes over time in a small scale recirculating system where waste water from smolt production was used to grow lettuce for commercial use. The treatment effect of lettuce on different solutions was tested and corresponding lettuce yield was evaluated. In order to enhance the treatment effect a rock wool filter was used on certain solutions. Important water quality parameters were measured every day, and the element concentration ...

Gjesteland, Ingrid

2013-01-01

138

Allelopathic action essential oils of alecrim-pimenta and lemongrass in germination of lettuce achenes
Ação alelopática de óleos essenciais de alecrim-pimenta e capimsanto na germinação de aquênios de alface
 

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The alecrim-pimenta and the lemongrass produce secondary compounds that can be used in alternative management of weed. The objective of this work was to evaluate the allelopathic effect of the essential oils of alecrim-pimenta and lemongrass in germination of lettuce achenes. It was used mature leaves of both species, and extracted the essential oil by distillation method of drag by water vapor. The bioassay was performed using achenes of crisp-leaf lettuce for summer and arranged in factoria...

2013-01-01

139

Tobacco streak virus isolated from lettuce.  

Science.gov (United States)

Tobacco streak virus (TSV) is an ilarvirus with a worldwide distribution. This virus infects many plants and causes significant yield losses. In this study, 300 samples of lettuce were collected from lettuce fields in Tehran Province. Infected plants show symptoms such as: mosaic, vein clearing, vein necrosis, yellowing and leaf distortion. DAS-ELISA (Double Antibody Sandwich-ELISA) was used with a polyclonal antiserum against TSV. Five isolates (T1, T2, T3, T4 and T5), which are collected, respectively from Mohammad Abad (Karaj), Malek Abad (Karaj), Hashtgerd (Karaj), Tarand Balla (Varamin) and Deh mah sin (Pishva) were inoculated on 29 species of Cucurbitaceae, Amaranthaceae, Solanacea, Compositae, Leguminosae and Chenopodiacea. Chenopodium quinoa 6 days after inoculation showed necrotic local lesions. Gomphrena globosa 10 days after inoculation developed chlorotic local lesions. Systemic symptoms were produced in Datura stramonium. Phaseolus vulgaris cv. Red Kidney 5 days after inoculation developed necrotic local lesions. Nicotiana tabacum 7 days after inoculation showed necrotic and chlorotic local lesions. Nicotiana clevelandii 15 days after inoculation developed leaf distortion and vein necrosis. Lactuca sativa 10-15 days after inoculation developed leaf istortion and mosaic. Reverse Transcription Polymerase Chain Reaction (RT-PCR) was performed using one primer pairs designed by DSMZ. An approximately 710 bp fragment was amplified with a specific primer. PMID:19634475

Abtahi, F S; Khodai Motlagh, M

2009-05-01

140

Tobacco streak virus Isolated from Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Tobacco streak virus (TSV is an ilarvirus with a worldwide distribution. This virus infects many plants and causes significant yield losses. In this study, 300 samples of lettuce were collected from lettuce fields in Tehran Province. Infected plants show symptoms such as: mosaic, vein clearing, vein necrosis, yellowing and leaf distortion. DAS-ELISA (Double Antibody Sandwich-ELISA was used with a polyclonal antiserum against TSV. Five isolates (T1, T2, T3, T4 and T5, which are collected, respectively from Mohammad Abad (Karaj, Malek Abad (Karaj, Hashtgerd (Karaj, Tarand Balla (Varamin and Deh mah sin (Pishva were inoculated on 29 species of Cucurbitaceae, Amaranthaceae, Solanacea, Compositae, Leguminosae and Chenopodiacea. Chenopodium quinoa 6 days after inoculation showed necrotic local lesions. Gomphrena globosa 10 days after inoculation developed chlorotic local lesions. Systemic symptoms were produced in Datura stramonium. Phaseolus vulgaris cv. Red Kidney 5 days after inoculation developed necrotic local lesions. Nicotiana tabacum 7 days after inoculation showed necrotic and chlorotic local lesions. Nicotiana clevelandii 15 days after inoculation developed leaf distortion and vein necrosis. Lactuca sativa 10-15 days after inoculation developed leaf istortion and mosaic. Reverse Transcription Polymerase Chain Reaction (RT-PCR was performed using one primer pairs designed by DSMZ. An approximately 710 bp fragment was amplified with a specific primer.

F.S. Abtahi

2009-01-01

 
 
 
 
141

Influence of initial pesticide concentrations and plant population density on dimethomorph toxicity and removal by two duckweed species.  

Science.gov (United States)

Aquatic plants take up, transform and sequester organic contaminants and may therefore be used in phytoremediation for the removal of pollutants from wastewaters. A better understanding of factors affecting the rate of contaminant uptake by aquatic plants is needed to improve engineered systems for removal of pollutants from wastewaters. This work focused on the influence of initial concentrations of pesticide and population density of plants on toxicity and uptake of the fungicide dimethomorph by two duckweed species. An increased sensitivity to dimethomorph was observed with increasing duckweed population density. Less light, due to crowding, may explain this higher sensitivity and reduced removal rate. A positive relationship was also found between toxicity or contaminant uptake and initial pesticide concentration with a maximal removal of 41 and 26 microg g(-1) fresh weight of dimethomorph (at 600 microg L(-1) of dimethomorph and an initial density of 0.10g E-flask(-1)) by Lemna minor and Spirodela polyrhiza, respectively. This research also indicated that these aquatic plants can efficiently eliminate organic contaminants and may ultimately serve as phytoremediation agents in the natural environment. PMID:20156640

Dosnon-Olette, Rachel; Couderchet, Michel; El Arfaoui, Achouak; Sayen, Stéphanie; Eullaffroy, Philippe

2010-04-15

142

Internalization of Sapovirus, a Surrogate for Norovirus, in Romaine Lettuce and the Effect of Lettuce Latex on Virus Infectivity  

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Noroviruses are the leading cause of food-borne outbreaks, including those that involve lettuce. The culturable porcine sapovirus (SaV) was used as a norovirus surrogate to study the persistence and the potential transfer of the virus from roots to leaves and from outer to inner leaves of lettuce plants. Treatment of lettuce with SaV was done through the roots of young plants, the soil, or the outer leaves of mature plants. Sampling of roots, xylem sap, and inner and outer leaves followed by ...

Esseili, Malak A.; Wang, Qiuhong; Zhang, Zhenwen; Saif, Linda J.

2012-01-01

143

Desempenho da alface em cultivo orgânico com e sem cobertura morta e diferentes lâminas d'água / Lettuce crop performance in organic tillage with and without mulching and at different irrigation water depths  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O experimento foi conduzido no período de 27/05/2006 a 02/08/2006 no SIPA (Sistema Integrado de Produção Agroecológica), localizado no município de Seropédica-RJ. Nesse trabalho, objetivou-se avaliar o desempenho da cultura da alface (Lactuca sativa L.) cultivada sob diferentes lâminas de irrigação [...] em um solo sem e com cobertura de palhada da leguminosa gliricídia. Foram conduzidos dois experimentos simultâneos, utilizando o delineamento experimental de blocos ao acaso, em ambos os experimentos, nos quais foram aplicadas 5 lâminas de irrigação, correspondendo a 25, 50, 80, 100, 115 % da evapotranspiração da cultura (ETc), sendo a produção final avaliada por meio da determinação da massa fresca, área foliar e número de folhas. Até o nível de 100% ETc, todas as variáveis analisadas tiveram seus valores aumentados, e para o nível de 115%, houve um decrescimento das mesmas. Na produção de massa fresca total, o sistema de cultivo com utilização de cobertura morta foi superior ao sem cobertura não diferenciando estatisticamente ao nível de 5 % probabilidade pelo teste F somente nas lâminas de 25 e 115% ETc. Abstract in english This work was carried out in order to evaluate the performance of a lettuce crop (Lactuca sativa L.) cultivated under different irrigation depths in ground with and without covering of gliricidia leguminosa. Two simultaneous experiments were conducted, in which 5 irrigation depths were applied, corr [...] esponding to 25, 50, 80, 100, and 115% of crop evapotranspiration (ETc). Final production was evaluated by means of the determination of fresh mass and leaf area. Up to the 100% ETc level, all the analyzed variables had their values increased. For the 115% level, there was a decrease of the same. In total fresh mass production, the system with covering was superior to the one without covering, not differentiating statistically to the 5% level probability for test F, except at depths of 25 and 115% ETc.

Márcio Emanoel de, Lima; Daniel Fonseca de, Carvalho; Adilson Pacheco de, Souza; José Guilherme Marinho, Guerra; Raul de Lucena Duarte, Ribeiro.

144

First report of Meloidogyne arenaria parasitizing lettuce in southern Spain  

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During the 2005-2006 autumn to winter lettuce-growing (Lactuca sativa cv. Iceberg) season, severely stunted and yellowing lettuce plants with disease incidence ranging from 80 to 100% were observed in four commercial, fall-sown fields at Almodóvar del Río (Córdoba Province) in southern Spain. Early symptoms consisted of severely reduced growth of the plants that continued with extensive leaf yellowing and the absence of tight-head formation. Attacks by the disease were estimated to cause n...

Castillo, Pablo; Landa, Blanca B.; Navas Corte?s, Juan Antonio; Vovlas, Nicola; Jime?nez-di?az, Rafael M.

2006-01-01

145

Leaf lettuce matabolome during aging and under stress  

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The plant metabolome is extremely diverse due to the extraordinary variety of secondary metabolites. Nuclear magnetic resonance (NMR) spectroscopy techniques in metabonomics have been used for the identification of metabolite presents in plants under stress. The work reported in this thesis aimed to evaluate the metabolic and physiological changes that occur in lettuce leaves, caused by aging, light and dark growth conditions and due to exposure to mancozeb pesticide. Lettuc...

Figueiredo, Patri?cia Isabel Duarte

2011-01-01

146

Quantitative microbial risk assessment for Escherichia coli O157 on lettuce, based on survival data from controlled studies in a climate chamber.  

Science.gov (United States)

The aims of the study were to determine the survival of Escherichia coli O157 on lettuce as a function of temperature and light intensity, and to use that information in a screening-level quantitative microbial risk assessment (QMRA) in order to evaluate risk-reducing strategies including irrigation water quality guidelines, rinsing, and holding time between last irrigation and harvest. Iceberg lettuce was grown in a climate chamber and inoculated with E. coli O157. Bacterial numbers were determined with the standard plate count method after inoculation and 1, 2, 4, and 7 day(s) postinoculation. The experiments were carried out at 11, 18, and 25°C in light intensities of 0, 400, and 600 mmol (m(2))(-1) s(-1). There was a significant effect of temperature and light intensity on survival, with less bacteria isolated from lettuce incubated at 25 and 18°C compared with 11°C (P lettuce consumption from 20 scenarios. A stricter water quality guideline gave a mean fivefold risk reduction. Holding times of 1, 2, 4, and 7 day(s) reduced the risk 3, 8, 8, and 18 times, respectively, compared with harvest the same day as the last irrigation. Finally, rinsing lettuce for 15 s in cold tap water prior to consumption gave a sixfold risk reduction compared with eating unrinsed lettuce. Sensitivity analyses indicated that variation in bacterial inactivation had the most significant effect on the risk outcome. A QMRA determining the relative risks between scenarios reduces uncertainty and can provide risk managers with decision support. PMID:22186038

Ottoson, Jakob R; Nyberg, Karin; Lindqvist, Roland; Albihn, Ann

2011-12-01

147

Relationship between Soil Health Assessment and the Growth of Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Soil health is very important point for plant growth which is measured by several indicators. The purposes of the research were to assess and to classify soil health Padang Betuah area of Bengkulu, and to compare between soil health indicators and lettuce plant performance indicators. Soils, consist of mineral and peat soils, were sampled using a soil random sampling technique. Lettuce plants were grown in polybags using sample soils. Both lettuce performance and soil health were assessed by calculating the percentage of total scores of lettuce plant or soil performance indicators which derived from variables observed. Soil variables for field evaluation included color, moisture content, texture, structure, compaction, land slope, organic matter, pH, amount of earthworm, erosion level, LCC (Legume Cover Crop, and vegetation performance. Soil variables for laboratory evaluation were pH, electrical conductivity (EC, total Carbon and Nitrogen, available-Posphorus, cation exchangeable capacity, base saturation, and aluminum saturation. While, the variables for lettuce growth performance included plant height, numbers of leaf, degree of leaf greenness, plant fresh weight, and relative percentage of shoot : root ratio. The results of field and laboratory evaluation showed that soil health were categoried as a healthy soil and moderate healthy soil both for mineral and peat soils, respectively. Furthermore, similar categories were also obtained for evaluation of plant performance categories. No correlation was found between the soil performance indicator category and the lettuce performance category.

Merakati Handajaningsih

2011-01-01

148

Prediction Model of Lettuce Nitrogen Content Based on Color Images  

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Full Text Available In order to facilitate intelligent precise nitrogen fertilizer management, a model of lettuce leaves’ nitrogen content is constructed. In this article, the lettuce samples of several nitrogen levels were cultivated. At Rosette stage, color images of lettuce leaves with every nitrogen level were collected and preprocessed and the texture features and the color features were extracted. Through the correlation analysis, principal component characteristics were extracted and image feature vectors were constructed after being screened and optimized. The regression equations of image feature vector and lettuce leaf nitrogen content were constructed by the principal component regression analysis method and the multiple linear regression method respectively. Based on the same test samples, prediction error rates of two expression models were computed. Results showed that the average error ratio of the principal component regression expression model is 9.30% and the one of multiple linear regression expression is 12.66%. The root mean square errors (RMSEP of PCR model was 0.4577 and the RMSEP of MLR model was 0.6284. It is also shown that the prediction result of the principal component regression expression model is better than the one of the latter and it can be applied to the nondestructive testing intuitive expression model of the nitrogen content of lettuce leaf. This study provides a basis or way to fertilize and manage nitrogen fertilizer precisely for lettuce or other crops.

Zhang Bing

2013-01-01

149

Growth of lettuce seedlings in different substrates  

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Full Text Available This research studied the growth of lettuce seedlings (Lactuca sativa L. cv. Veronica cultivated under greenhouse conditions, using polystyrene trays with 128 cells and three different commercial substrates: Golden Mix, Plantmax and Plugmix. The statistical design was in the form of randomized blocks, with eight (8 replications. Fifteen days after sowing the seeds, samples (five in total of plants were taken to evaluate the height, number of leaves, leaf area, leaf specific area, leaf specific weight, absolute and relative growth rates and net assimilation rates. The evaluated growth indexes showed that seedlings produced with the Plantmax and Plugmix substrates could be planted 25 days after sowing, since they have at least four definitive leaves. The Plantmax substrate showed, at the end of the evaluation, the best results in height, dry weight, leaf specific area, absolute growth rates and net assimilation rates.

Milene Rodrigues Peres

2007-12-01

150

Evaluation of non-chemical seed treatment methods for the control of Phoma valerianellae on lamb`s lettuce seeds  

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The aim of the present study was to identify seed treatment methods for eradicating Phoma valerianellae from lamb`s lettuce seeds in organic vegetable production. Using seeds naturally infested with the pathogen, the effect of three physical methods (hot water, aerated steam, electron treatment) and different agents of natural origin (micro-organisms, plant derived products, resistance inducers) was tested on moist filter paper, in seed trays under controlled conditions and in the field. In a...

Schmitt, A.; Koch, E.; Stephan, D.; Kromphardt, C.; Jahn, M.; Krauthausen, H. J.; Forsberg, G.; Werner, S.; Amein, T.; Wright, S. A. I.; Tinivella, F.; Wolf, J. M.; Groot, S. P. C.

2009-01-01

151

7 CFR 319.56-24 - Lettuce and peppers from Israel.  

Science.gov (United States)

...2010-01-01 false Lettuce and peppers from Israel. 319.56-24 Section 319.56-24...319.56-24 Lettuce and peppers from Israel. (a) Lettuce may be imported into the United States from Israel without fumigation for leafminers,...

2010-01-01

152

Disinfection of iceberg lettuce by titanium dioxide-UV photocatalytic reaction.  

Science.gov (United States)

Securing the physical quality and microbial safety of fresh foods has been a major focus in the food industry. To improve quality and increase the shelf life of fresh produce, disinfection methods have been developed. Titanium dioxide (TiO2) photocatalytic reactions under UV radiation produce hydroxyl radicals that can be used for disinfection of foodborne pathogenic bacteria. We investigated the effects of TiO2-UV photocatalytic disinfection on the shelf life of iceberg lettuce. Counts of natural microflora (total aerobic bacteria, coliforms, psychrotrophic bacteria, and yeasts and molds) and inoculated pathogenic bacteria (Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Salmonella Typhimurium) on iceberg lettuce were determined after 20-min treatments with TiO2-UV, UV radiation, a sodium hypochlorite (NaOCl) solution, and tap water. TiO2-UV treatment reduced the number of microorganisms by 1.8 to 2.8 log CFU/g compared with reductions of 0.9 to 1.4 and 0.7 to 1.1 log CFU/g obtained with UV radiation and NaOCl treatments, respectively. Treatment with tap water was used as a control and resulted in no reductions. Counts of microflora for iceberg lettuce at 4 and 25 degrees C were determined during a 9-day period. TiO2-UV treatment resulted in 1.2- and 4.3-log increases in the counts of total aerobic bacteria at 4 and 25 degrees C, respectively, compared with 1.3- to 1.6-log and 4.4- to 4.8-log increases due to UV radiation and NaOCl treatments. PMID:19777894

Kim, Youngbong; Choi, Yoonjung; Kim, Soohyun; Park, Jonghyun; Chung, Myongsoo; Song, Kyung Bin; Hwang, Ingyun; Kwon, Kisung; Park, Jiyong

2009-09-01

153

The eukaryotic translation initiation factor 4E controls lettuce susceptibility to the Potyvirus Lettuce mosaic virus.  

Science.gov (United States)

The eIF4E and eIF(iso)4E cDNAs from several genotypes of lettuce (Lactuca sativa) that are susceptible, tolerant, or resistant to infection by Lettuce mosaic virus (LMV; genus Potyvirus) were cloned and sequenced. Although Ls-eIF(iso)4E was monomorphic in sequence, three types of Ls-eIF4E differed by point sequence variations, and a short in-frame deletion in one of them. The amino acid variations specific to Ls-eIF4E(1) and Ls-eIF4E(2) were predicted to be located near the cap recognition pocket in a homology-based tridimensional protein model. In 19 lettuce genotypes, including two near-isogenic pairs, there was a strict correlation between these three allelic types and the presence or absence of the recessive LMV resistance genes mo1(1) and mo1(2). Ls-eIF4E(1) and mo1(1) cosegregated in the progeny of two separate crosses between susceptible genotypes and an mo1(1) genotype. Finally, transient ectopic expression of Ls-eIF4E restored systemic accumulation of a green fluorescent protein-tagged LMV in LMV-resistant mo1(2) plants and a recombinant LMV expressing Ls-eIF4E degrees from its genome, but not Ls-eIF4E(1) or Ls-eIF(iso)4E, accumulated and produced symptoms in mo1(1) or mo1(2) genotypes. Therefore, sequence correlation, tight genetic linkage, and functional complementation strongly suggest that eIF4E plays a role in the LMV cycle in lettuce and that mo1(1) and mo1(2) are alleles coding for forms of eIF4E unable or less effective to fulfill this role. More generally, the isoforms of eIF4E appear to be host factors involved in the cycle of potyviruses in plants, probably through a general mechanism yet to be clarified. PMID:12857809

Nicaise, Valérie; German-Retana, Sylvie; Sanjuán, Raquel; Dubrana, Marie-Pierre; Mazier, Marianne; Maisonneuve, Brigitte; Candresse, Thierry; Caranta, Carole; LeGall, Olivier

2003-07-01

154

Role of O-antigen on the Escherichia coli O157:H7 cells hydrophobicity, charge and ability to attach to lettuce.  

Science.gov (United States)

Environmental factors encountered during growing and harvesting may contribute to Escherichia coli O157:H7 contamination of lettuce. Limited nutrients and extended exposure to water may cause E. coli O157:H7 to shed its O antigen. Absence of the O157-polysaccharide antigen could affect the cell's physicochemical properties (hydrophobicity and cell charge) and ultimately influence its attachment to surfaces. The objectives of this study were to evaluate the effect of the E. coli O157:H7 O-antigen on the cell's overall hydrophobicity, charge and ability to attach to cut edge and whole leaf iceberg lettuce surfaces. Three strains of E. coli O157:H7 (86-24 wild type; F-12, mutant lacking the O-antigen and pRFBE, plasmid for O157 gene reintroduced) were examined for their hydrophobicity, overall charge and ability to attach to lettuce. Overall, E. coli O157:H7 attached at higher levels to cut surfaces over whole leaf surfaces (P=0.008) for all strains and treatments. Additionally, the strain lacking the O-antigen (F12)-attached significantly less to lettuce (P=0.015) than the strains expressing the antigen (WT and pRFBE). Cells lacking the O antigen (strain F-12) were also significantly more hydrophobic than strains 86-24 or pRFBE (P?0.05). Surface charge differed among the strains tested (P?0.05); however, it did not appear to influence bacterial attachment to lettuce surfaces. The charge was not fully restored in the pRFBE strain (expression of O-antigen reintroduced), therefore, no conclusions can be made pertaining to the effect of charge on attachment in this study. Results indicate that E. coli O157:H7 cells which lack the O-antigen have greater hydrophobicity and attach at lower concentrations than cells expressing the O-antigen, to iceberg lettuce surfaces. PMID:21550681

Boyer, Renee R; Sumner, Susan S; Williams, Robert C; Kniel, Kalmia E; McKinney, Julie M

2011-06-30

155

TiO2 photocatalytic inactivation under simulated solar light of bacterial consortia in domestic wastewaters previously treated by UASB, duckweed and facultative ponds  

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In this work, TiO2 photocatalysis was used to disinfect domestic wastewaters previously treated by different biological treatment systems: Upward-flow Anaerobic Sludge Blanket (UASB), facultative pond, and duckweed pond. The microorganisms monitored were E. coli, total coliforms, Shigella species, and Salmonella species. Photocatalytic experiments were carried out using two light sources: a solar simulator (UV intensity: 68-70 W m-2) and black-light lamps (BLL UV intensity: 17-20 W m-2). Samp...

Julián Andrés Rengifo-Herrera; Cesar Pulgarin; Fiderman Machuca; Janeth Sanabria

2010-01-01

156

Rapid determination of fosetyl-aluminum residues in lettuce by liquid chromatography/electrospray tandem mass spectrometry.  

Science.gov (United States)

This paper describes a new method for the sensitive and selective determination of fosetyl-aluminum (Al) residues in vegetable samples. The method involves extraction with water by using a high-speed blender and subsequent injection of the 5-fold diluted extract into the liquid chromatograph. Fosetyl-Al is determined by liquid chromatography with electrospray tandem mass spectrometry after the addition of tetrabutylammonium acetate as the ion-pairing reagent. The method has been used to assay lettuce samples spiked at 2 and 0.2 mg/kg. Recoveries were satisfactory, with mean values of 98 and 106%, respectively, and relative standard deviations were fosetyl-Al residues in lettuce with very little sample handling and good sensitivity; it was shown to be robust by the analysis of almost 100 samples. PMID:14509444

Hernández, Félix; Sancho, Juan V; Pozo, Oscar J; Villaplana, Carme; Ibáñez, María; Grimalt, Susana

2003-01-01

157

Comparison of Different Washing and Disinfection Protocols Used by Food Services in Southern Brazil for Lettuce (Lactuca sativa)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Different protocols have been used for washing and disinfecting leafy vegetables in Brazilian food services, however its effect on microbial reduction was barely studied. The aim of this study was to evaluate the effectiveness of lettuce washing and disinfecting protocols used by food services. The treatments evaluated were: washing in potable tap water (T1); washing and dipping in potable tap water (T2); washing with potable tap water and dipping in a solution of sodium hypochlorite (200 ppm...

Ana Beatriz Almeida de Oliveira; Ana Carolina Ritter; Eduardo Cesar Tondo; Marisa Itapema Cardoso

2012-01-01

158

Potential Uptake of Escherichia coli O157:H7 from Organic Manure into Crisphead Lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To investigate the potential transfer of Escherichia coli O157:H7 from contaminated manure to fresh produce, lettuce seedlings were transplanted into soil fertilized with bovine manure which had been inoculated with approximately 104 CFU g?1 E. coli O157:H7. The lettuce was grown for approximately 50 days in beds in climate-controlled rooms in a greenhouse. As the bacterium was not detected in the edible parts of the lettuce, the outer leaves of the lettuce, or the lettuce roots at harvest ...

Johannessen, Gro S.; Bengtsson, Gunnar B.; Heier, Berit T.; Bredholt, Sylvia; Wasteson, Yngvild; Rørvik, Liv Marit

2005-01-01

159

Use of a common laboratory glassware detergent improves recovery of Cryptosporidium parvum and Cyclospora cayetanensis from lettuce, herbs and raspberries.  

Science.gov (United States)

The success of any protocol designed to detect parasitic protozoa on produce must begin with an efficient initial wash step. Cryptosporidium parvum and Cyclospora cayetanensis oocysts were seeded onto herbs, lettuces and raspberries, eluted with one of four wash solutions and the recovered number of oocysts determined via fluorescent microscopy. Recovery rates for fluorescein thiosemicarbazide labeled C. parvum oocysts seeded onto spinach and raspberries and washed with de-ionized water were 38.4 ± 10.1% and 34.9 ± 6.2%, respectively. Two alternative wash solutions viz. 1M glycine, pH 5.5 and a detachment solution were tested also using labeled C. parvum seeded spinach and raspberries. No statistically significant difference was noted in the recovery rates. However, a wash solution containing 0.1% Alconox, a laboratory glassware detergent, resulted in a significant improvement in oocyst recovery. 72.6 ± 6.6% C. parvum oocysts were recovered from basil when washed with 0.1% Alconox compared to 47.9 ± 5.8% using detachment solution. Also, C. cayetanensis oocysts were seeded onto lettuces, herbs and raspberries and the recovery using de-ionized water were compared to 0.1% Alconox wash: basil 17.5 ± 5.0% to 76.1 ± 14.0%, lollo rosso lettuce 38.3 ± 5.5% to 72.5 ± 8.1%, Tango leaf lettuce 45.9 ± 5.4% to 71.1 ± 7.8% and spring mix (mesclun) 39.8 ± 0.7% to 80.2 ± 11.3%, respectively. These results suggest that the use of Alconox in a wash solution significantly improves recovery resulting in the detection of these parasitic protozoa on high risk foods. PMID:22094179

Shields, Joan M; Lee, Michelle Minjung; Murphy, Helen R

2012-02-01

160

Comparison between Hydroponically and Conventionally and Organically Grown Lettuces for Taste, Odor, Visual Quality and Texture: A Pilot Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hydroponic production of vegetables is becoming more common. In this study hydroponic lettuce, grown by a local distributor, and conventionally and organically field-grown lettuce, purchased at local retail stores were compared by descriptive analysis for taste, odor, visual quality and texture. Five lettuce varieties were compared; Romaine, Green Leaf, Red Leaf, Butter, and Common lettuce. A twenty-three member sensory panel randomly rated the lettuce using a 5 point scale or a 3 point scale...

Murphy, Matthew T.; Fannie Zhang; Nakamura, Yukiko K.; Omaye, Stanley T.

2011-01-01

 
 
 
 
161

Plant growth, metabolism and adaptation in relation to stress conditions. XXI. Reversal of harmful NaCl-effects in lettuce plants by foliar application with urea  

Directory of Open Access Journals (Sweden)

Full Text Available In relation to water control levels, administration of NaCl at low (3 dSm-1, medium (5 dSm-1 or high (7 dSm-1 concentration, in the growth medium of the lettuce plants, induced significant decreases in growth components as well as in the metabolites and enzymes determined, at vegetative and adult growth stages. On the other hand, significant increases in all growth and photosynthetic components determined, as well as in carbohydrate contents and in the activities of the antioxidant enzymes were obtained, above the water control levels, in response of treatment of lettuce plants with urea fertilizer up to 4 %, above which urea at 5% and 6% induced significant decreases in all the above mentioned components, throughout the entire periods of the experiments. Foliar application of urea up to 5 % to the variously salinized lettuce plants induced significant increases in all growth components as well as in all metabolites determined as compared with values of control-salinized plants. At 6% urea, significant decreases in growth parameters and in metabolites determined for the variously salinized plants were apparent. Thus, foliar application of urea can, at least, partially alleviate the inhibitory effects of salinity on growth and metabolism of lettuce plants; the magnitude of response being most pronounced with 3-4% urea.

Mahmoud Elbaz Younis

2008-09-01

162

Genetic resources collections of leafy vegetables (lettuce, spinach, chicory, artichoke, asparagus, lamb’s lettuce, rhubarb and rocket salad): composition and gaps  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lettuce, spinach and chicory are generally considered the main leafy vegetables, while a fourth group denoted by ‘minor leafy vegetables’ includes, amongst others, rocket salad, lamb’s lettuce, asparagus, artichoke and rhubarb. Except in the case of lettuce, central crop databases of leafy vegetables were lacking until recently. Here we report on the update of the international Lactuca database and the development of three new central crop databases for each of the other leafy vegetable...

2012-01-01

163

Use of soil improvers and plant strenghter in lettuce production  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the winter of 2010 and 2011, we studied the impact of fertilizers for soil improvement and plant strengthening PRPSOL and PRPEBV on lettuce varieties Complice in an indoor space at the farm Weber. The experiment was designed according to a random block system with four treatments in four repetitions. The picking of lettuce was carried out in two periods. In the first period we measured: plant mass and the mass marketing of plants, rosette diameter, and the diameter of the root salad, vitam...

2012-01-01

164

Persistence and Dissipation of Chlorpyrifos in Brassica Chinensis, Lettuce, Celery, Asparagus Lettuce, Eggplant, and Pepper in a Greenhouse  

Science.gov (United States)

The residue behavior of chlorpyrifos, which is one of the extensively used insecticides all around the world, in six vegetable crops was assessed under greenhouse conditions. Each of the vegetables was subjected to a foliar treatment with chlorpyrifos. Two analytical methods were developed using gas chromatography equipped with a micro-ECD detector (LOQ?=?0.05 mg kg?1) and liquid chromatography with a tandem mass spectrometry (LOQ?=?0.01 mg kg?1). The initial foliar deposited concentration of chlorpyrifos (mg kg?1) on the six vegetables followed the increasing order of brassica chinensis<lettucelettucelettuce), 0.97 (brassica chinensis), 1.47 (asparagus lettuce), and 3.50 mg kg?1 (celery), respectively. The half-lives of chlorpyrifos were found to be 7.79 (soil), 2.64 (pepper plants), 3.90 (asparagus lettuce), 3.92 (lettuce), 5.81 (brassica chinensis), 3.00 (eggplant plant), and 5.45 days (celery), respectively. The dissipation of chlorpyrifos in soil and the six selected plants was different, indicating that the persistence of chlorpyrifos residues strongly depends upon leaf characteristics of the selected vegetables.

Lu, Meng-Xiao; Jiang, Wayne W.; Wang, Jia-Lei; Jian, Qiu; Shen, Yan; Liu, Xian-Jin; Yu, Xiang-Yang

2014-01-01

165

Survival of Escherichia coli O157:H7 and Salmonella enterica serovars Typhimurium in iceberg lettuce and the antimicrobial effect of rice vinegar against E. coli O157:H7.  

Science.gov (United States)

The microbiological safety of fresh produce is a significant concern of consumers and industry. After applying at an inoculated level (about 10(6) CFUg(-1)) of E. coli O157:H7 and Salmonella enterica serovars Typhimurium on shredded iceberg lettuce and water samples individually, they were stored at 4 degrees C for 14 days and 22 degrees C for 7 days to monitor the growth and survival of pathogens. The results showed that at the end of 4 degrees C storage, populations of two pathogens in lettuce and water decreased approximately 1 log CFUg(-1). However, microbial levels on shredded lettuce increased 3 logs within 3 days at 22 degrees C. Vinegar (acetic acid) had been used to reduce populations of foodborne pathogens in foods; hence, the antimicrobial effect of rice vinegar on the survival of E. coli O157:H7 in inoculated lettuce (10(4) and 10(7) CFUg(-1)) is examined in this study. Results were observed that the treatment of inoculated lettuce (10(7) CFUg(-1)) with commercial vinegar containing 5% acetic acid (pH 3.0) for 5 min would reduce 3 logs population at 25 degrees C. Less than a 1-log decrease in bacterial numbers was recovered during 5 min exposure to 0.5% (pH 3.26) acetic acid. PMID:17613372

Chang, Ju-Mei; Fang, Tony J

2007-01-01

166

Light-Emitting Diodes (LEDs) for Miniature Hydroponic Lettuce  

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There is growing concern about food safety, environmental impact, and efficient energy usage in agricultural production systems. Producing lettuce under artificial lighting could be a solution addressing these concerns. Light-emitting diodes (LEDs) offer the advantages of a narrow light spectrum, low power consumption, and little heat production. The objective of this study was to determine the effects of different light sou...

Kent Kobayashi; Teresita Amore; Michelle Lazaro

2013-01-01

167

Lettucenin sesquiterpenes contribute significantly to the browning of lettuce.  

Science.gov (United States)

Wound-induced changes in the composition of secondary plant compounds cause the browning of processed lettuce. Cut tissues near the lettuce butt end clearly exhibit increased formation of yellow-brown pigments. This browning reaction is typically been attributed to the oxidation of polyphenols by the enzyme polyphenol oxidase (PPO). However, in our previous study on Iceberg lettuce, we showed that, besides the enzymatic polyphenol browning, other reactions must be involved in the formation of colored structures. With the present study for the first time, we isolated yellow sesquiterpenes by multilayer countercurrent chromatography (MLCCC), followed by preparative high-performance liquid chromatography (HPLC). Further analyses by nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques identified lettucenin A and three novel derivatives. We call these compounds lettucenins A1, B, and B1. Color-dilution analyses revealed these lettucenins as key chromophores in the browning of Iceberg lettuce. A time formation curve showed the accumulation of lettucenins A and B within 40 h after cutting. Thereafter, these structures were degraded to unknown colored compounds. Lettucenin A was verified in five varieties of Lactuca. In contrast to that, lettucenin A was present only at trace levels in five varieties of Cichorium. Therefore, lettucenin A might be used as a chemosystematic marker of the genus Lactuca. PMID:24818869

Mai, Franziska; Glomb, Marcus A

2014-05-21

168

Hygienic-sanitary quality of vegetables and evaluation of treatments for the elimination of indigenous E. coli and E. coli O157:H7 from the surface of leaves of lettuce (Lactuca sativa L.) Qualidade higiênico-sanitária de hortaliças e avaliação de tratamentos para eliminação de E. coli indígena e E. coli O157:H7 na superfície de folhas de alface (Lactuca sativa L.)  

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The purpose of this study is to evaluate the hygienic-sanitary quality of vegetables and irrigation water and assess the effectiveness of lemon juice and vinegar in reducing E. coli strains inoculated on lettuce. One hundred and forty samples of vegetables and 45 samples of irrigation water were investigated for thermotolerant coliforms and Salmonella spp. In order to verify the effectiveness of natural household sanitizers in reducing E. coli in inoculated lettuce, four treatment solutions w...

Ytana oliveira Santos; Rogeria Comastri de Castro Almeida; Alaise Gil Guimarães; Paulo Fernando Almeida

2010-01-01

169

An Ophiovirus isolated from lettuce with big-vein symptoms.  

Science.gov (United States)

Big-vein is a widespread and damaging disease of lettuce, transmitted through soil by the chytrid fungus Olpidium brassicae, and generally supposed to be caused by Lettuce big-vein virus (LBVV; genus Varicosavirus). This virus is reported to have rigid rod-shaped particles, a divided double-stranded RNA genome, and one capsid protein of 48 kD, but has not been isolated or rigorously shown to cause the disease. We provide evidence that a totally different virus, here named Mirafiori lettuce virus (MiLV), is also very frequently associated with lettuce showing big-vein symptoms. MiLV was mechanically transmissible from lettuce to Chenopodium quinoa and to several other herbaceous test plants. The virus was partially purified, and an antiserum prepared, which did not react with LBVV particles in decoration tests. As reported for LBVV, MiLV was labile, soil-transmitted and had a single capsid protein of 48 kD, but the particles morphologically resembled those of ophioviruses, and like these, MiLV had a genome of three RNA segments approximately 8.5, 1.9 and 1.7 kb in size. MiLV preparations reacted strongly in Western blots and in ISEM with antiserum to Tulip mild mottle mosaic virus, an ophiovirus from Japan also apparently Olpidium-transmitted. They reacted weakly but clearly in Western blots with antiserum to Ranunculus white mottle virus, another ophiovirus. When lettuce seedlings were mechanically inoculated with crude or partially purified extracts from MiLV-infected test plants, many became systemically infected with MiLV and some developed big-vein symptoms. Such plants did not react in ELISA using an LBVV antiserum or an antiserum to tobacco stunt virus, and varicosavirus-like particles were never seen in them in the EM after negative staining. We conclude that MiLV is a hitherto undescribed virus assignable to the genus Ophiovirus. The cause or causes of lettuce big-vein disease and the properties of LBVV may need to be re-evaluated in light of our results. PMID:11205109

Roggero, P; Ciuffo, M; Vaira, A M; Accotto, G P; Masenga, V; Milne, R G

2000-01-01

170

Light-Emitting Diodes (LEDs for Miniature Hydroponic Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available There is growing concern about food safety, environmental impact, and efficient energy usage in agricultural production systems. Producing lettuce under artificial lighting could be a solution addressing these concerns. Light-emitting diodes (LEDs offer the advantages of a narrow light spectrum, low power consumption, and little heat production. The objective of this study was to determine the effects of different light sources on the growth of miniature “Tom Thumb” butterhead lettuce in a non-circulating hydroponic system. Lettuce seedlings, started in Oasis Horticubes, were transferred to net pots in containers with a hydroponic nutrient solution. The lettuce was grown in a lab under three light treatments—blue LEDs, red LEDs, and fluorescent lights. At the end of the study, fluorescent lights resulted in greater root dry weight than blue LEDs and red LEDs. Total plant dry weight under fluorescent lights was greater than under red LEDs. There were no significant differences in shoot dry weight and plant height among the treatments. Percent partitioning of dry weight to shoots was greatest with red LEDs, followed by blue LEDS, and fluorescent lights. Percent partitioning of dry weight to roots was greatest with fluorescent lights, followed by blue LEDS, and red LEDs. Leaf chlorophyll content was greater under blue LEDs and fluorescent lights than red LEDs. The pH of the nutrient solution of the blue LED and the fluorescent light treatments were greater than the red LED treatment. Electrical conductivity of the nutrient solution of the fluorescent light treatment was greater than the blue LED treatment and the red LED treatment. In conclusion, LEDs could provide an alternative lighting source for miniature lettuce production.

Michelle Lazaro

2013-03-01

171

Inactivation of Escherichia coli O157:H7, Salmonella enterica serotype enteritidis, and Listeria monocytogenes on lettuce by hydrogen peroxide and lactic acid and by hydrogen peroxide with mild heat.  

Science.gov (United States)

Iceberg lettuce is a major component in vegetable salad and has been associated with many outbreaks of foodborne illnesses. In this study, several combinations of lactic acid and hydrogen peroxide were tested to obtain effective antibacterial activity without adverse effects on sensory characteristics. A five-strain mixture of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes was inoculated separately onto fresh-cut lettuce leaves, which were later treated with 1.5% lactic acid plus 1.5% hydrogen peroxide (H2O2) at 40 degrees C for 15 min, 1.5% lactic acid plus 2% H2O2 at 22 degrees C for 5 min, and 2% H2O2 at 50 degrees C for 60 or 90 s. Control lettuce leaves were treated with deionized water under the same conditions. A 4-log reduction was obtained for lettuce treated with the combinations of lactic acid and H2O2 for E. coli O157:H7 and Salmonella Enteritidis, and a 3-log reduction was obtained for L. monocytogenes. However, the sensory characteristics of lettuce were compromised by these treatments. The treatment of lettuce leaves with 2% H2O2 at 50 degrees C was effective not only in reducing pathogenic bacteria but also in maintaining good sensory quality for up to 15 days. A E. coli O157:H7 and Salmonella Enteritidis was achieved with the 2% H2O2 treatment, whereas a 3-log reduction of L. monocytogenes was obtained. There was no significant difference (P > 0.05) between pathogen population reductions obtained with 2% H2O2 with 60- and 90-s exposure times. Hydrogen peroxide residue was undetectable (the minimum level of sensitivity was 2 ppm) on lettuce surfaces after the treated lettuce was rinsed with cold water and centrifuged with a salad spinner. Hence, the treatment of lettuce with 2% H2O2 at 50 degrees C for 60 s is effective in initially reducing substantial populations of foodborne pathogens and maintaining high product quality. PMID:12182470

Lin, Chia-Mi; Moon, Sarah S; Doyle, Michael P; McWatters, Kay H

2002-08-01

172

Efeitos da cobertura do solo com filme de polietileno azul no consumo de água da cultura da alface cultivada em estufa Effects of the soil covering with blue colored polyethylene film on lettuce crop consumptive water-use in a gree  

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Full Text Available A cobertura do solo é uma prática agrícola que visa, principalmente, a controlar as plantas invasoras, a diminuir as perdas de água por evaporação do solo e a facilitar a colheita e a comercialização, uma vez que o produto se torna mais limpo e sadio. Porém, ao se cobrir o solo, também são alterados parâmetros importantes do microclima e, conseqüentemente, a germinação das sementes, o crescimento das raízes, a absorção de água e nutrientes, a atividade metabólica das plantas e o armazenamento de carboidratos. O objetivo do presente trabalho foi avaliar o efeito da cobertura do solo com filme de polietileno azul no consumo de água da cultura da alface (Lactuca sativa L.. O experimento foi instalado em uma estufa convencional, no município de Araras - SP, e conduzido durante o período de 22-3-2001 a 1º-5-2001. O consumo de água foi medido em dois lisímetros de pesagem instalados no interior da estufa. O espaçamento da cultura foi de 0,25 m x 0,25 m. Também foi avaliado o índice de área foliar (IAF em seis épocas distintas e determinada a eficiência do uso de água (EU ao final do ciclo da cultura. O delineamento estatístico foi o de blocos inteiramente casualizados, com dois tratamentos, "solo descoberto" e "solo coberto". O consumo médio de água foi de 4,17 mm dia-1 para o tratamento "solo descoberto" e de 3,11 mm dia-1 para o tratamento "solo coberto". O índice médio de área foliar não diferiu estatisticamente entre os tratamentos.The covering of the soil is an agricultural practice that intends to control the harmful herbs, to reduce the losses of water by evaporation of the soil, and to facilitate the harvest and the commercialization, once the product is cleaner and healthier. However, when the soil is covered important microclimatic parameters are also altered, and consequently the germination of seeds, the growth of roots, the absorption of water and nutrients, the metabolic activity of the plants and the carbohydrates storage. The current trial intended to evaluate the effect of soil covering with blue colored film on consumptive water-use in a lettuce crop (Lactuca sativa, L.. The experiment was carried out in a plastic greenhouse in Araras - São Paulo State, Brazil from March 3rd, 2001 to May 5th, 2001. The consumptive water-use was measured through two weighing lysimeter installed inside the greenhouse. Crop spacing was 0.25 m x 0.25 m and the color of the film above soil was blue. Leaf area index (IAF, was measured six times (7; 14; 21; 28; 35; 40 days after transplant and the water-use efficiency (EU was measured at the end. The experimental design was subdivided portions with two treatments, "bare soil" and "covered soil". The average consumptive water-use was 4.17 mm day-1 to the "bare soil" treatment and 3.11 mm day-1 to the "covered soil" treatment. The final leaf area index was 25.23 to the "bare soil" treatment and 24.39 to the "covered soil" treatment, and there was no statistical difference between then.

Alexandre O. Gonçalves

2005-12-01

173

Effect of Wastewater from Quetta City on the Germination and Seedling Growth of Lettuce (Lactuca sativa L.  

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Full Text Available This study was concerned to the effects of 5 various level of polluted water of three different localities of Quetta city (viz., Chiltan Ghee Mill, Chiltan Town and Zarghoon Town on seed germination and seedling growth of Lettuce (Lactuca sativa L.. The Lettuce was taken as a test plant and its seeds were germinated in petri-dishes in the Laboratory. Results showed that seed germination was significantly reduced and delayed as the concentration of wastewater (domestic and industrial effluents increased. Seedling growth (radical and plumule length also showed adverse effect in response to increasing level of polluted water. Whereas, plumule growth was comparatively better than that of radical subjected to initial doses of polluted water. However, by comparing the source of polluted water, maximum reduction in germination and seedling growth were obtained in the effluents of Chiltan Ghee Mill followed by domestic sewage of Chiltan and Zarghoon towns, respectively. It can be safely concluded that polluted water is becoming a threat for the crops with the passage of time as more and more wastes are becoming the part of it. Therefore, it is necessary to investigate the effects of polluted water on plants. Through appropriate awareness campaigns the communities in general and notables in particular, should be made aware of the harmful effects of the activity within the traditional norms and practices.

Zahoor Ahmad Bazai

2006-01-01

174

Effect of wash treatments on reducing human norovirus on iceberg lettuce and perilla leaf.  

Science.gov (United States)

Human noroviruses (NoVs) are major causes of nonbacterial gastroenteritis; they are transmitted by food and water, as well as person-to-person. The consumption of contaminated raw or uncooked food such as vegetables and fruits has been identified as a common source of human NoV outbreaks. In an effort to understand the survival and persistence of human NoVs on fresh produce, the efficacy of washing treatments in the removal of human NoVs from vegetables was evaluated. This study used artificially contaminated vegetables (iceberg lettuce and perilla leaf), and washing was done with tap water for convenience. Wash treatments included immersion in water, rinsing with running water, and a combination of immersion and rinsing (treatments I to III, respectively). The effect of a class I detergent, a commercial product used for washing fruits and vegetables, was also evaluated (treatment IV). After the wash treatments, the remnants of human NoVs on samples were measured via real-time reverse transcriptase PCR. The results varied among treatments and by vegetable. For iceberg lettuce, a reduction of 0.9 log was noted in the treatment III group. The wash treatment was more effective in the perilla leaf samples: each treatment significantly reduced the numbers of human NoVs (0.69- to 1.29-log reduction). These data demonstrated that wash treatments reduced numbers of virus from the surfaces of the vegetables. Therefore, washing would seem to be a basic step in reducing numbers of virus in food preparation and in viral transmission routes. PMID:22054192

Bae, Ju-Yun; Lee, Jeong-Su; Shin, Myoung-Hee; Lee, Soon-Ho; Hwang, In-Gyun

2011-11-01

175

Effect of temperature and type of packages on nitrates and nitrites content in lettuce  

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Full Text Available Lettuce wrapped in unperforated PE film, perforated PE film, stretch film and without wrapping was stored at 1, 6, 20 and 28°C. Freshly harvested lettuce and after one day of storage, independently on storage conditions, did not contains nitrites„ During storage of lettuce at 1°C only one time small quantities of nitrites (4.3 mg NO2/kg fresh matter were found - after twelve days storage in perforated PE film. Storage of lettuce longer than 7 days at 6°C caused formation of nitrites. Lettuce stored at 20 and 28°C in unperforated PE film contained nitrites already after 2 or 3 days of storage. Decline of nitrates during storage of lettuce was independent from film used to wrapping.

Józef B?kowski

1996-12-01

176

Machine Vision Monitoring System of Lettuce Growth in a State-Of Greenhouse  

Science.gov (United States)

Farmers want a monitoring system to support decisions for plant cultivation and to obtain information for plant health conditions. This study established the remote monitoring system in a greenhouse and provided the machine vision system with remote control camera to extract plant images, to analyze a trend of lettuce growth, and to predict fresh weights of lettuce plants. The calibration bars with color patches were used for the geometric calibration and the extraction of lettuce regions from the image captured under sunlight conditions. The fresh weight prediction model was developed by the image analysis of lettuces growing in a greenhouse.

Lee, Jong Whan

177

Dynamic Model as Attainment Effort of Nitrogen Synchronization at Lettuce Cultivation with Green Manure Paitan  

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Full Text Available Lettuce (Lactuca sativa is vegetable crop that consumed part of the leaf and harvested at a phase of vegetative. Nitrogen play important role in growth at phase of vegetative. Nitrogen in spacious have the character of easy to lose because of leaching. Increasing yield of lettuce can be done by improving Nitrogen synchronization, that is precisely usage moment with ready moment of N during and amount of its. The research was aimed to study of the pattern nitrogen requirement for lettuce crop, ready pattern of nitrogen by Tithonia diversifolia and design nitrogen synchronization model between lettuce crop with green manure of T. diversifolia. The research were divided in two phases that are phase research 1: Dynamic modeling for nitrogen synchronization on lettuce cultivation by green manure of T. diversifolia, and phase research 2: Fertilizer technology of high nitrogen synchronization on lettuce cultivation by green manure of T. diversifolia. The result of phase research 1 (first year research shows that dynamic model of N requirement by lettuce crop, release and availability model of N by T. diversifolia and synchronization model of N between requirement of N lettuce with release and availability of N by T. diversifolia. The dynamic model indicate that giving 10 t ha-1 of T. diversifolia which given 2 weeks before transplanting at lettuce crop can support high result and growth because happened good synchronization of N.

Yuni Agung Nugroho

2009-05-01

178

Hypochlorite treatments are not a significant source of perchlorate exposure in lettuce.  

Science.gov (United States)

Leafy vegetables, such as lettuce ( Lactuca sativa L), have been identified as a potential source of perchlorate exposure to humans. Perchlorate is of concern because excessive amounts may impair thyroid function by inhibiting iodide uptake by the sodium iodide symporter. Perchlorate has been identified as an oxidation product in sodium hypochlorite. Dilute hypochlorite solutions are widely used on lettuce as a preservative and as a treatment to reduce microbial food risks. However, the potential of hypochlorite to be a source of human perchlorate exposure from lettuce had not been evaluated. Studies were conducted with lettuce collected in the San Luis Valley of southern Colorado and in the lower Colorado River Valley of southwestern Arizona to represent conditions under which hypochlorite is applied to lettuce in the field and in salad processing facilities. We used spray and dipping solutions that were dilutions of concentrated sodium hypochlorite that would contain from 12000 and 120000 microg/L perchlorate. The perchlorate content of iceberg and romaine lettuce averaged 6.2 and 7.2 microg/kg fw in southern Colorado and 14.0 and 56.7 microg/kg fw in southwestern Arizona and there were no significant (P > 0.05) increases in the perchlorate content of lettuce due to hypochlorite treatments. Because of the relatively low concentrations of perchlorate present after dilution and the low volumes applied to lettuce, hypochlorite solutions do not appear to be a significant source of the perchlorate levels found in lettuce. PMID:19245207

Sanchez, C A; Fonseca, J M; Blount, B C; Krieger, R I

2009-03-25

179

Aceptabilidad de lechuga de hoja fresca troceada, tratada con ácido ascórbico mediante hidroenfriamiento / Acceptability of fresh cut leaf lettuce treated with ascorbic acid applied by hydrocooling  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish Se evaluó el efecto del ácido ascórbico aplicado mediante dos métodos de hidroenfriamiento sobre la aceptabilidad general, sabor y apariencia de lechuga verde de hoja troceada, así como la relación entre el sabor y la apariencia de la lechuga de hoja procesada sobre la aceptabilidad general de este [...] producto. La lechuga de hoja fue hidroenfriada con una solución de ácido ascórbico al 1% mediante inmersión y aspersión, o con agua por inmersión. Se uso como control a lechuga no hidroenfriada. Las soluciones para tratamientos fueron aplicadas a 5 ºC por 2 min, y la lechuga fue luego empacada en bolsas de polietileno impermeables a la humedad, almacenada a 5 ºC por 14 días, y evaluada en los días 1, 7 y 14 de almacenamiento. La aceptabilidad general de la lechuga de hoja procesada (troceada y empacada) estuvo altamente correlacionada con su sabor (R²= 0.85), pero no con su apariencia (R²= 0.39). Todos los tratamientos mantuvieron sus valores de aceptabilidad general y sabor durante el almacenamiento de 14 días (p>0.05). Sin embargo, la lechuga hidroenfriada mediante aspersión con ácido ascórbico y la no hidroenfriada (control) fueron los únicos tratamientos que mantuvieron su apariencia durante el estudio. Es requerida más experimentación con la aplicación de ácido ascórbico mediante hidroenfriamiento para garantizar su utilidad para la conservación de la calidad sensorial de la lechuga de hoja procesada durante su almacenamiento. Abstract in english We assessed the effect of ascorbic acid, applied by two hydrocooling methods, on the overall acceptability, taste and appearance of cut green leaf lettuce, and the relationship between the taste and appearance of processed leaf lettuce regarding the overall acceptability of this product. Leaf lettuc [...] e was hydrocooled with a solution of 1% ascorbic acid by immersion and spraying, or by immersion in water. Non-hydrocooled lettuce was used as control. The treatment solutions were applied at 5 °C for 2 min, and the lettuce was then packed in polyethylene bags, impervious to moisture, stored at 5 °C for 14 days, and evaluated after 1, 7 and 14 days of storage. The overall acceptability of processed leaf lettuce (cut and packed) was highly correlated with its taste (R²= 0.85), but not with its appearance (R²= 0.39). All treatments maintained the overall acceptability values and taste of the lettuce during the 14 days of storage (p> 0.05). However, the lettuce that was hydrocooled by spraying with ascorbic acid, and the non-hydrocooled lettuce (control) were the only treatments that maintained appearance during the study. Further experimentation with the application of ascorbic acid by hydrocooling is required to ensure its usefulness for maintaining the sensory quality of processed leaf lettuce during storage.

Esparza-Rivera, Juan Ramón; Navarro Bravo, Agustín; Kendall, Patricia; Fortis Hernández, Manuel; Preciado Rangel, Pablo; Meza Velázquez, Jorge Armando.

180

A naturally occurring recombinant isolate of Lettuce mosaic virus.  

Science.gov (United States)

LMV-Common and LMV-Most are two seed-borne types of Lettuce mosaic virus (LMV), genus Potyvirus. LMV-Most, but not LMV-Common, overcomes the resistance afforded to lettuce by two recessive genes, mo11 and mo12. An RT-PCR-based assay thought to be specific for LMV-Most also amplified LMV-Tn2, previously typified as LMV-Common. The sequence of selected regions along the genome indicated that LMV-Tn2 is a natural recombinant between LMV-Most and LMV-Common isolates, with a putative recombination site located within the P3 coding region. This is the first evidence of a naturally occurring LMV recombinant isolate. PMID:14689284

Krause-Sakate, R; Fakhfakh, H; Peypelut, M; Pavan, M A; Zerbini, F M; Marrakchi, M; Candresse, T; Le Gall, O

2004-01-01

 
 
 
 
181

Screening for resistance to lettuce downy mildew (Bremia lactucae)  

International Nuclear Information System (INIS)

Screening methods of Lactuca spp. for resistance to Bremia lactucae (lettuce downy mildew) are described in this chapter. Procedures of isolation, cultivation and maintenance of B. lactucae isolates are summarised. Resistance screening can be carried out either on lettuce seedlings, detached cotyledon leaves, leaf disks or parts of true leaves from adult plants. Methodology of inoculum preparation, inoculation and incubation conditions is described. For the assessment infection degree, a qualitative or quantitative approach is used. A basic differential set of Lactuca spp: used for testing B. lactucae isolates and virulence phenotypes of the most important B. lactucae races was established, including the denomination of races by the sextet code. The methods described have a broad application both in practice and research. They are useful for resistance screening of new breeding material, for searching for new sources of resistance in Lactuca spp. germplasm, for investigating plant resistance mechanisms and also for the study of virulence variation in B. lactucae isolates and populations. (author)

2010-05-01

182

Uptake of uranium by lettuce (Lactuca sativa L.) in natural uranium contaminated soils in order to assess chemical risk for consumers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Uranium mining activity in Cunha Baixa (Portugal) village has left a legacy of polluted soils and irrigation water. A controlled field experiment was conducted with lettuce (Lactuca sativa L.) in an agricultural area nearby the abandoned mine in order to evaluate uranium uptake and distribution in roots and leaves as well as ascertain levels of uranium intake by the local inhabitants from plant consuming. Two soils with different average uranium content (38 and 106 ...

Neves, O.; Abreu, M. M.; Vicente, E. M.

2008-01-01

183

Long-term deficit and excess of irrigation influences quality and browning related enzymes and phenolic metabolism of fresh-cut iceberg lettuce (Lactuca sativa L.)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of five drip irrigation treatments (excess 50%, excess 25%, control, deficit 25%, and deficit 50%) on the quality and shelf life of fresh-cut iceberg lettuce (Lactuca sativa L) were examined in 6 different harvest dates during 3 consecutive years. To minimize climatic differences between harvest dates, rainfall (mm) and crop evapotranspiration (ETc) (mm) were also considered during the whole growing period. The total amount of water was calculated considering the irrigation treatm...

2012-01-01

184

Quantitative study of cross-contamination with Escherichia coli, E. coli 0157, MS2 phage and murine norovirus in a simulated fresh-cut lettuce wash process  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The water management in fresh-cut produce processing is an important factor affecting the microbial quality and safety of fresh-cut produce. For this study, a commercial lettuce washing process was simulated using two subsequent washing baths (WB). The worst case scenario, when no sanitizers are used and still common in some European countries, was investigated to fully understand the potential for cross-contamination and to obtain baseline data for further risk assessment. The two cross-cont...

2014-01-01

185

Microbiological Quality of Bagged Cut Spinach and Lettuce Mixes?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Analysis of 100 bagged lettuce and spinach samples showed mean total bacterial counts of 7.0 log10 CFU/g and a broad range of <4 to 8.3 log10 CFU/g. Most probable numbers (MPN) of ?11,000 /g coliforms were found in 55 samples, and generic Escherichia coli bacteria were detected in 16 samples, but no E. coli count exceeded 10 MPN/g.

2008-01-01

186

Comparison of three fungicide spray advisories for lettuce downy mildew  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lettuce growers in coastal California have relied mainly on protective fungicide sprays to control downy mildew. Thus, timing of sprays before infection is critical for optimal results. A leaf-wetness-driven, infection-based advisory system, previously developed, did not always perform satisfactorily. In this study, the advisory system was modified by incorporating a pathogen survival component (system 1) or both survival and sporulation components (system 2). These systems were then evaluate...

Wu, B. M.; Subbarao, K. V.; Bruggen, A. H. C.; Koike, S. T.

2001-01-01

187

Outbreak of Shigella sonnei infection traced to imported iceberg lettuce.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the period from May through June 1994, an increase in the number of domestic cases of Shigella sonnei infection was detected in several European countries, including Norway, Sweden, and the United Kingdom. In all three countries epidemiological evidence incriminated imported iceberg lettuce of Spanish origin as the vehicle of transmission. The outbreaks shared a number of common features: a predominance of adults among the case patients, the presence of double infections with other enterop...

1995-01-01

188

Biological and molecular variability of lettuce mosaic virus isolates.  

Science.gov (United States)

ABSTRACT Lettuce mosaic potyvirus (LMV) causes severe disease of commercial lettuce crops. LMV isolates show wide biological variability, particularly in their ability to overcome the resistance genes described in Lactuca sativa. For a better understanding of the molecular interaction between lettuce and LMV, biological and molecular characterization of a collection of 10 LMV isolates known to differ in virulence or aggressiveness was performed. The ability of these isolates to overcome the resistance genes was reevaluated under standardized conditions. To study the molecular variability of LMV, an immunocapture-reverse transcription-poly-merase chain reaction technique, coupled with direct sequencing, was used to obtain nucleotide sequence data from three short regions of the LMV genome. Clustering analysis was performed and compared to the biological properties of the 10 isolates. Three groups of LMV isolates were discriminated based on the molecular data. These groups appear to correlate with the geographic origin of the isolates rather than with their pathogenicity. Sequence comparison with California isolates clearly showed that the California isolates are related to the western European isolates, raising the possibility of past exchanges of LMV between western Europe and California. PMID:18945118

Revers, F; Lot, H; Souche, S; Le Gall, O; Candresse, T; Dunez, J

1997-04-01

189

Effect of Gypsum Application on Enzymatic Browning Activity in Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available A comprehensive study to evaluate calcium, in terms of gypsum (CaSO4.2H2O by soil dressing application, on enzymatic browning activity of Polyphenol oxidase (PPO and internal qualities was tested on lettuce var. Grand Rapids under field conditions. A factorial in completely randomized design was arranged with four replications. The results showed that plants-treated with 50 mg kg-1 gypsum applied at 40 DAP had the maximal fresh weight of 25.83 g plant-1. The internal qualities of the lettuce at harvest showed that plants treated with 50 mg kg-1 gypsum had the maximal chlorophyll content (26.80 mg m-2, while all gypsum concentrations applied in this study, had less content of ascorbic acid than the control plants. Plants-treated with 100 mg kg-1 gypsum affected to the lowest level of PPO activity at week 3 after transplanting. Furthermore, gypsum application had no effect to biomass, leaf colour, the contents of phenolic and quinone in lettuce at harvesting stage.

Prasit Chutichudet

2009-01-01

190

Quantification of metal bioavailability for lettuce (Lactuca sativa L.) in field soils.  

Science.gov (United States)

Understanding metal bioavailability of plants in soils requires, apart from physiological processes and symbiosis with arbuscular mycorrhizal fungi, the consideration of the chemical availability in the soil solution (the intensity of the toxic exposure) and the soil's capacity to supply the metal (capacity). In this contribution we report on the time-dependent accumulation of As, Cd, Cr, Cu, Ni, Pb, and Zn in lettuce (Lactuca sativa L.). Bioassays with 17 Dutch field soils and two artificially metal-contaminated soils were carried out. Phytotoxicity was observed in soils with pH (pore water) plant transpired and the available concentration in the water. No net accumulation of As, Pb, Ni, and especially Cr was observed in most soils tested. The latter observation is in agreement with findings of Zayed et al. (Planta, 1998 206:293-299), who reported that translocation of Cr from roots to shoots is extremely limited. Internal Cd levels in the plants varied greatly among soils, whereas plant tissue concentrations of Zn and especially Cu appear to be regulated at more or less fixed levels. The 0.01 M CaCl(2)-extractable metal pool provides the best descriptor for the capacity of the soil to supply Cd and Zn. This enabled the development of models that are suited to predict Zn and Cd uptake by lettuce in both field soils (weathered soils) and soils to which metal salts were added, which is common practice in toxicity testing of chemicals. It is concluded that of all metals included in this study, Cd is the metal of most concern due to bioaccumulation through the soil-plant-animal food chain as Cd is the only metal that might pose human or animal health risks at plant tissue concentrations that are not directly phytotoxic. Finally, application of the models for risk assessment purposes is discussed. PMID:11031301

Peijnenburg, W; Baerselman, R; de Groot, A; Jager, T; Leenders, D; Posthuma, L; Van Veen, R

2000-11-01

191

The Use of Green Fluorescent Protein-Tagged Recombinant Viruses to Test Lettuce mosaic virus Resistance in Lettuce.  

Science.gov (United States)

ABSTRACT Seed certification and the use of cultivars containing one of two, probably allelic, recessive genes, mo1(1) and mo1(2), are the principal control methods for Lettuce mosaic virus (LMV) in lettuce. Although for a few LMV isolates, mo1(2) confers resistance with most isolates, the genes mo1(1) or mo1(2) confer a tolerance, and virus accumulation is readily detected in mo1-carrying plants. This phenotype complicates evaluation of the resistance status, in particular for mo1(1), for which there are no viral strains against which a true resistance is expressed. Two green fluorescent protein (GFP)-tagged viruses were constructed, derived from a non-resistance breaking isolate (LMV-0) and from a resistance-breaking isolate (LMV-E). An evaluation of 101 cultivars of known status was carried out with these recombinant viruses. Using the LMV-0-derived recombinant, identification of mo1-carrying cultivars was simple because, contrary to its wild-type parent, systemic movement of LMV-0-GFP was abolished in resistant plants. This assay detected four cases of misidentification of resistance status. In all these cases, further tests confirmed that the prior resistance status information was incorrect, so that a 100% correlation was observed between LMV-0-GFP behavior and the mo1 resistance status. Similarly, the LMV-E-derived recombinant allowed the identification of mo1(2) lettuce lines because its systemic movement was restricted in mo1(2) lines but not in susceptible or in mo1(1) lines. The tagged viruses were able to systemically invade another host, pea, irrespective of its resistance status against another member of the genus Potyvirus, Pea seed-borne mosaic virus. The use of these recombinant viruses could therefore greatly facilitate LMV resistance evaluation and speed up lettuce breeding programs. PMID:18943090

Candresse, T; Le Gall, O; Maisonneuve, B; German-Retana, S; Redondo, E

2002-02-01

192

Heat and drought stress during growth of lettuce (Lactuca sativa L.) does not promote internalization of Escherichia coli O157:H7.  

Science.gov (United States)

Studies were done to determine the effect of heat stress on internalization of Escherichia coli O157:H7 in lettuce subjected to different watering practices during growth. Iceberg and romaine lettuce were grown in sandy soil in an environmental chamber at 23 degrees C during the day and 7 degrees C at night, with a 12-h photoperiod. Thirty days after transplanting seedlings, potting soil was inoculated with a five-strain mixture of green fluorescent protein-labeled E. coli O157:H7 at populations of 4 and 6 log CFU/g of soil. Lettuce plants were exposed to one of two temperature stress regimes: 36 degrees C during the day and 15 degrees C at night for 2 days, or 32 degrees C during the day and 15 degrees C at night for 3 days, both with a 12-h photoperiod. Control plants were held at 23 degrees C during the day and 7 degrees C at night for 3 days. Plants were either watered daily or not watered during the heat stress and control treatments. E. coli O157:H7 was detected by enrichment in all inoculated soil and rhizosphere samples from plants grown in inoculated soil. Less E. coli O157:H7 was detected in inoculated heat-stressed soil than in control soil. From inoculated pots, all leaf surfaces and macerated leaves that had been surface sanitized were negative for E. coli O157:H7. All surface-sanitized macerated roots from control samples and from 143 of 144 samples of inoculated samples were negative for E. coli O157:H7. Heat stress during growth of lettuce did not promote or enhance internalization of E. coli O157:H7, regardless of the moisture content in the soil. PMID:20003727

Zhang, Guodong; Ma, Li; Beuchat, Larry R; Erickson, Marilyn C; Phelan, Vanessa H; Doyle, Michael P

2009-12-01

193

Antioxidant capacity and contents of phenols, ascorbic acid, ?-carotene and lycopene in lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available The antioxidant activity of three lettuce varieties (Lactuca sativa L. Emerald, Vera and Neva, cultivated in two kinds of protected spaces, a glasshouse and a plastic greenhouse, under controlled conditions, was determined. The content of antioxidant compounds: total phenols, flavonoids, L-ascorbic acid, ß-carotene and lycopene, were determined in ethanolic extracts of the lettuce with spectrophotometric methods. The largest content of total phenols (78.98 ± 0.67 mg GAE/g of dry extract was found in ethanolic extract of the lettuce variety Neva cultivated in a plastic greenhouse, whereas the largest content of flavonoids (35.45 ± 0.95 mg RU/g of dry extract was displayed in the lettuce Emerald cultivated in a glasshouse. It was observed that the lettuce cultivated in the glasshouse contained a somewhat higher content of L-ascorbic acid than the lettuce same variety from plastic greenhouse. The content of lycopene in the examined lettuce is negligible, and the content of ß-carotene is low. On the other hand, the high content of phenolic components causes favourable antioxidant properties found in all varieties of examined lettuce. [Projekat Ministarstva nauke Republike Srbije, br. TR 31059: A new concept in breeding vegetable cultivars and hybrids designed for sustainable growing systems using biotechnological methods

Zdravkovi? Jasmina M.

2014-01-01

194

Ascorbic Acid Retention in Shredded Iceberg Lettuce as Affected by Minimal Processing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of slicing method, packaging atmosphere and storage temperature were determined on total ascorbic acid (TAA) content of modified atmosphere packaged shredded lettuce. TAA was extracted from the lettuce samples and levels were monitored using either titration with 2,6-dichlorophenolindophenol solution or an assay kit. Slicing affected (p manual slicing > machine slicing. Flushing with 100% nitrogen increased retention (~5%...

1998-01-01

195

Indexação do Lettuce mosaic virus em sementes e plântulas de genótipos de alface / Lettuce mosaic virus indexation in seeds and seedlings of lettuce genotypes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O Lettuce mosaic virus espécie mais importante na cultura de alface (Lactuca sativa L.) no Brasil, causando sintomas de mosaico, clareamento das nervuras, necrose, distorção foliar e redução do crescimento da planta, pode ser transmitido por sementes com uma taxa de 1% a 16%, dependendo da interação [...] dos genótipos de alface com os isolados LMV-Most ou LMV-Common. Neste trabalho, avaliou-se a detecção do LMV por PTA-ELISA, em sementes e plântulas de oito genótipos de alface: 'Vanessa Roxa', 'Baba de Verão', 'Verdinha', 'Maravilha das 4 Estações', 'Evely', 'Marcela', 687 ('Sapore' x 'Vera' ), 784 ('Sapore' x 'Vera'), utilizando anti-soro policlonal específico. O vírus não foi detectado em sementes do genótipo 'Verdinha' e, em plântulas dos genótipos 687, 'Marcela' e 'Evely', após a germinação em papel e 687, 784 e 'Marcela' com gene mo1¹, após a germinação em substrato. A avaliação individual do número de sementes infectadas foi de 100% para 'Vanessa Roxa' e 'Baba de Verão', 87,7% para 'Verdinha', 46,6% para 'Maravilha das 4 Estações' e 16,6% para 'Evely'. Nos genótipos com gene de resistência o percentual foi de 15,6%, 26,6%, 90% em 'Marcela', 687 e 784, respectivamente. A detecção do LMV por PTA-ELISA foi eficiente tanto em sementes quanto em plântulas. Abstract in english Lettuce mosaic virus is the major virus in lettuce (Lactuca sativa L.) in Brazil, causing symptoms of mosaic, vein clearing, necrosis, leaf distortion and growth reduction. The LMV is transmitted by seeds at a rate of 1% to 16%, mostly due to interaction between the isolates LMV-Most and LMV-Common [...] and the lettuce cultivar. In this study, LMV detection by PTA-ELISA in seeds and seedlings of eight lettuce genotypes, 'Vanessa Roxa', 'Baba de Verão', 'Verdinha', 'Maravilha das 4 Estações', 'Evely', 'Marcela', 687 ('Vera' X 'Sapore'), 784 ('Vera' X 'Sapore'), was evaluated, using specific polyclonal antisera. The virus was not detected in seeds of 'Verdinha' genotype and seedlings of 687, 'Marcela' and 'Evely' after germination in a paper towel or in 687, 784 and 'Marcela' with the mo1¹ resistance gene, after germination in a substrate. The individual evaluation of the number of infected seeds made by PTA-ELISA was 100% for 'Vanessa Roxa' and 'Baba de Verão', 87.7% for 'Verdinha', 46.6% for 'Maravilha das 4 Estações' and 16.6% for 'Evely'. In the genotypes with the resistance gene the percentage was 15.6%, 26.6%, 90% in 'Marcela', 687 and 784, respectively. Virus detection in seeds and seedlings by PTA-ELISA was very efficient for both seeds and seedlings.

Lillian Silveira, Pereira; Alexandre Levi Rodrigues, Chaves; Joaquim Adelino, Azevedo Filho; Addolorata, Colariccio.

196

Effect of temperature and type of packages on quality of stored lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Lettuce head cv. Sanora non-wrapped, wrapped with perforated PE film, unperforated PE film, and in stretch film was stored at different temperatures: 1, 6, 20 and 28°C. The lettuce can be stored at 1°C up to 10 days, and at 6°C during 8 days period. Longer storage time caused clear loses of lettuce quality. During first two - three days of storage in both temperatures 1 and 6°C loses of ascorbic acid, dry matter, colour and organoleptic value were not observed. Faster decrease of ascorbic acid content was noted in leuuce stored in unperforated PE film and stretch film, in comparison to perforated PE film. The highest lettuce quality were found in case where lettuce were stored in perforated PE bags at 1°C.

Józef B?kowski

1996-12-01

197

ROLE OF PH IN THE ACCUMULATION OF LEAD AND NICKEL BY COMMON DUCKWEED (LEMNA MINOR  

Directory of Open Access Journals (Sweden)

Full Text Available Heavy metals are the most common non-biodegradable pollutants. Various remediation methods have been used for the treatment of heavy metal contaminated water. However, phytoremediation technology is currently being used due to its economically feasible and ecologically viable advantages. The aim of this study was to examine the role of pH in the accumulation capacity of Lemna minor in Pb and Ni contaminated water. The removal rate of Pb and Ni from L. minor was 99.99% and 99.30% respectively, after 28 days of exposure to the 10 mgl-1 Pb and Ni contaminated water at pH 5-6 and pH 6 respectively. // //

Leela Kaur

2012-11-01

198

Pennywort And Duckweed Marsh System For Upgrading Wastewater Effluent From A Mechanical Package Plant.  

Science.gov (United States)

A small artificial marsh system has been used to upgrade the effluent from a mechanical package plant for over seven years. The artificial marsh has a hydraulic retention time of 7 to 8 d. Although originally stocked with water hyacinth (Eichhornia crassi...

B. C. Wolverton R. C. McCaleb

1987-01-01

199

Preliminary Studies on Growth and Fresh Weight of Lettuce (Lactuca sativa as Affected by Clay Pot Irrigation and Spacing  

Directory of Open Access Journals (Sweden)

Full Text Available An experiment (Completely Randomized Design was set up to determine the effects of Clay Pot Sub-surface Irrigation (CPSI and spacing on the growth and fresh weight of lettuce (Lactuca sativa. The treatments were: CPSI with spacing; 15x15 cm, 20x20 cm and 30x30 cm. Control treatments were Watering Can Irrigation (WCI with the same spacing as above. Treatments were replicated three times given a total of 18 experimental units. Eighteen large enamel basins of 50/20 cm (diameter/height were filled with good topsoil and a clay pot buried neck deep in each of the basins. Seedlings were planted in all the eighteen basins. Five Hundred mL of wastewater was applied daily to plants in each container having either clay pot or watering can treatment. Plant height increased from 2.50 to 4.25 cm within 6 Weeks after Transplanting (WAT under CPSI and only increased from 2.14 to 2.99 cm under WCI. The CPSI also supported better leave growth and fresh weight. The fresh weight of lettuce increased almost two fold under 15x15 cm spacing compared to 20x20 and 30x30 cm.

George Nyarko

2011-01-01

200

Effect of the Municipal Garbage on the Growth of Lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Municipal Garbage (MG) as a plant nutrient supply was evaluated. Some of the garbage was collected from Hail city, Kingdom of Saudi Arabia. The garbage was fermented partially after removing its contents of stones and metals. Lettuce plants were transplanted in five greenhouse pot experiments. In the first, a portion of the MG was mixed with a sandy soil at either 1, 2 or 3% before the transplanting. In the second, a portion of the MG was mixed with hydrochloric acid 0.1 Nat ratio of 1:2 for ...

Al-redhaiman, K. N.; Nassar, I. N.; Al-salamah, I. S.

2003-01-01

 
 
 
 
201

Effect of Gypsum Application on Enzymatic Browning Activity in Lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A comprehensive study to evaluate calcium, in terms of gypsum (CaSO4.2H2O) by soil dressing application, on enzymatic browning activity of Polyphenol oxidase (PPO) and internal qualities was tested on lettuce var. Grand Rapids under field conditions. A factorial in completely randomized design was arranged with four replications. The results showed that plants-treated with 50 mg kg-1 gypsum applied at 40 DAP had the maximal fresh weight of 25.83 g plant-1...

2009-01-01

202

Assessing nitrogen supply potential and influence on growth of lettuce and amaranthus of different aged composts  

International Nuclear Information System (INIS)

This study assessed the potential of different composts at different maturity stages to supply N and their effect on the vegetative growth of lettuce and Amaranthus. Five composts aged 1, 3, 6, 9, and 12 months, were mixed with soil at the rate of 5%, 10% and 15% then seeded with lettuce and Amaranthus. Results showed that 1, 3 and 6 month aged composts had a negative effect on plant height of lettuce and Amaranthus as 1-15.78% and 4.78 to 29.45% decrease in plant height over control was recorded respectively. On the other hand 9 and 12 month aged composts had a significant positive effect on plant height of lettuce and Amaranthus where 43.48% and 34.8% increase over control was recorded with the application of 15% of 12 month aged compost respectively. A similar effect was observed on fresh biomass of both lettuce and Amaranthus where a 386% and 59.43% increase over control was recorded with the application of 15% of 12 month aged compost respectively. One and three month aged composts revealed a negative effect on N absorption by lettuce whereas 1, 3, 6 and 9 month aged composts had a negative effect on N absorption by Amaranthus. 30.39% and 21.48% increases over control in N absorption by lettuce and Amaranthus respectively were recorded with the application of 15% of 12 month aged compost. (author)

2010-02-01

203

Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations  

Science.gov (United States)

In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and probably part of a single macromolecular scaffold. Fresh Ulva tissue appears to contain the same three functional groups but at lower concentrations, based on wet weight. The titration in natural seawater was largely dominated by the non-carbonate alkalinity of the solution and could not be robustly modeled. Results of fits with ionic strengths fixed at their experimental values indicate that the pKas of all three groups display prominent Debije-Hückel-type behavior, hence that these acid dissociation reactions involve a different mechanism than metal-proton exchange reactions on mineral surfaces, whose distribution coefficients (i.e., equilibrium constants) generally show a weak ionic strength dependence.

Ebling, A. M.; Schijf, J.

2008-12-01

204

Fiscalização de hortas produtoras de verduras do município de Ribeirão Preto, SP Monitoring of lettuce crops of Ribeirão Preto, SP, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available O consumo de verduras cruas desempenha importante papel na transmissão de várias doenças infecciosas pela freqüente prática de irrigação de hortas com água contaminada. O objetivo deste estudo é a avaliação das condições higiênico-sanitárias de todas as hortas produtoras de verduras de Ribeirão Preto, SP com implantação de um sistema de fiscalização. A análise laboratorial de 129 hortas revelou irregularidades em 20,1% delas, destacando-se elevada concentração de coliformes fecais em 17%, presença de Salmonella em 3,1% e de vários enteroparasitas (Ascaris sp, Ancylostomidae, Strongyloides sp, Hymenolepis nana e Giardia sp em 13,1%. A repetição da análise das hortas irregulares determinou a interdição definitiva de uma delas; todas as demais foram aprovadas, comprovando a eficácia do sistema de fiscalização, particularmente com a implantação, inédita no país, do certificado de vistoria sanitária.The ingesting of raw vegetables plays an important role in the transmission of several infectious diseases due to the high frequency of irrigation with wastewater. The objective of this study was to evaluate the sanitary conditions of all lettuce producing crops in Ribeirão Preto through microbiological and parasitological analysis of both irrigation water and lettuce together with the implantation of an effective crop monitoring. Laboratory analysis of 129 crops showed irregularities in 26 (20.1% of these: high concentration of fecal coliforms in 17% of the lettuce, presence of Salmonella in 3.1% and several enteroparasites (Ascaris sp, Ancylostomidae, Strongyloides sp, Hymenolepis nana, and Giardia sp in 13.1%. Persistent irregularities determined the definitive closing down of one producer; all of the remaining 128 crops were eventually approved, thus demonstrating the efficacy of lettuce crop monitoring. Crops approved in the laboratory analysis were awarded a Sanitary Inspection Certificate - an unprecedented procedure in our Country - that resulted in a better acceptance of the monitoring.

Osvaldo M. Takayanagui

2000-04-01

205

Changes in the chlorophyll content in stored lettuce Lactuca sativa L. after pre-harvest foliar application of CaCl2  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the present investigations was to determine the cumulative effect of foliar treatment of lettuce plants with a CaCl2 solution and the cold-storage period on the level of chlorophylls in the leaves of lettuce cv. ?Omega? (Lactuca sativa L.. Plants were grown in a pot experiment conducted in the greenhouse of the Department of Cultivation and Fertilisation of Horticultural Plants, University of Life Sciences in Lublin. During the growing period, 10 and 20 days before harvest, the plants received foliar application of CaCl2 at the concentrations of 0.1 M and 0.2 M. Control plants were sprayed with water. Some plants were analysed immediately after the harvest; other specimens were cold-stored at a temperature of 4oC for 7 and 14 days. Whole leaves and blades without the midrib were analysed. The results obtained indicated that the foliar application of 0.2M CaCl2 in lettuce resulted in a decrease in the level of chlorophylls in fresh plants, compared with the control. A beneficial cumulative effect of the CaCl2 application and storage period on the chlorophyll level in lettuce leaves was observed in the leaf blades of plants after foliar treatment with the 0.1M CaCl2.solution and cold-stored for 7 and 14 days, in which in- creased levels of chlorophyll “a” and “b” and total chlorophyll, compared with the control, were found.

Irena Perucka

2014-01-01

206

Effect of CO2 levels on nutrient content of lettuce and radish  

Science.gov (United States)

Atmospheric carbon-dioxide enrichment is known to affect the yield of lettuce and radish grown in controlled environments, but little is known about CO2 enrichment effects on the chemical composition of lettuce and radish. These crops are useful model systems for a Controlled Ecological Life-Support System (CELSS), largely because of their relatively short production cycles. Lettuce (Lactuca sativa L.) cultivar 'Waldmann's Green' and radish (Raphanus sativus L.) cultivar 'Giant White Globe' were grown both in the field and in controlled environments, where hydroponic nutrient solution, light, and temperature were regulated, and where CO2 levels were controlled at 400, 1000, 5000, or 10,000 ppm. Plants were harvested at maturity, dried, and analyzed for proximate composition (protein, fat, ash, and carbohydrate), total nitrogen (N), nitrate N, free sugars, starch, total dietary fiber, and minerals. Total N, protein N, nonprotein N (NPN), and nitrate N generally increased for radish roots and lettuce leaves when grown under growth chamber conditions compared to field conditions. The nitrate-N level of lettuce leaves, as a percentage of total NPN, decreased with increasing levels of CO2 enrichment. The ash content of radish roots and of radish and lettuce leaves decreased with increasing levels of CO2 enrichment. The levels of certain minerals differed between field- and chamber-grown materials, including changes in the calcium (Ca) and phosphorus (P) contents of radish and lettuce leaves, resulting in reduced Ca/P ratio for chamber-grown materials. The free-sugar contents were similar between the field and chamber-grown lettuce leaves, but total dietary fiber content was much higher in the field-grown plant material. The starch content of growth-chamber lettuce increased with CO2 level.

McKeehen, J. D.; Smart, D. J.; Mackowiak, C. L.; Wheeler, R. M.; Nielsen, S. S.; Mitchell, C. A. (Principal Investigator)

1996-01-01

207

Detection of viable Salmonella in lettuce by propidium monoazide real-time PCR.  

Science.gov (United States)

Contamination of lettuce by Salmonella has caused serious public health problems. Polymerase chain reaction (PCR) allows rapid detection of pathogenic bacteria in food, but it is inaccurate as it might amplify DNA from dead target cells as well. This study aimed to investigate the stability of DNA of dead Salmonella cells in lettuce and to develop an approach to detecting viable Salmonella in lettuce. Salmonella-free lettuce was inoculated with heat-killed Salmonella Typhimurium cells and stored at 4 °C. Bacterial DNA extracted from the sample was amplified by real-time PCR targeting the invA gene. Our results indicate that DNA from the dead cells remained stable in lettuce for at least 8 d. To overcome this limitation, propidium monoazide (PMA), a dye that can selectively penetrate dead bacterial cells and cross-link their DNA upon light exposure, was combined with real-time PCR. Lettuce samples inoculated with different levels of dead or viable S. Typhimurium cells were treated or untreated with PMA before DNA extraction. Real-time PCR suggests that PMA treatment effectively prevented PCR amplification from as high as 10(8) CFU/g dead S. Typhimurium cells in lettuce. The PMA real-time PCR assay could detect viable Salmonella at as low as 10(2) CFU/mL in pure culture and 10(3) CFU/g in lettuce. With 12-h enrichment, S. Typhimurium of 10(1) CFU/g in lettuce was detectable. In conclusion, the PMA real-time PCR assay provides an alternative to real-time PCR assay for accurate detection of Salmonella in food. PMID:22417362

Liang, Ningjian; Dong, Jin; Luo, Laixin; Li, Yong

2011-05-01

208

The Eukaryotic Translation Initiation Factor 4E Controls Lettuce Susceptibility to the Potyvirus Lettuce mosaic virus1  

Science.gov (United States)

The eIF4E and eIF(iso)4E cDNAs from several genotypes of lettuce (Lactuca sativa) that are susceptible, tolerant, or resistant to infection by Lettuce mosaic virus (LMV; genus Potyvirus) were cloned and sequenced. Although Ls-eIF(iso)4E was monomorphic in sequence, three types of Ls-eIF4E differed by point sequence variations, and a short in-frame deletion in one of them. The amino acid variations specific to Ls-eIF4E1 and Ls-eIF4E2 were predicted to be located near the cap recognition pocket in a homology-based tridimensional protein model. In 19 lettuce genotypes, including two near-isogenic pairs, there was a strict correlation between these three allelic types and the presence or absence of the recessive LMV resistance genes mo11 and mo12. Ls-eIF4E1 and mo11 cosegregated in the progeny of two separate crosses between susceptible genotypes and an mo11 genotype. Finally, transient ectopic expression of Ls-eIF4E restored systemic accumulation of a green fluorescent protein-tagged LMV in LMV-resistant mo12 plants and a recombinant LMV expressing Ls-eIF4E° from its genome, but not Ls-eIF4E1 or Ls-eIF(iso)4E, accumulated and produced symptoms in mo11 or mo12 genotypes. Therefore, sequence correlation, tight genetic linkage, and functional complementation strongly suggest that eIF4E plays a role in the LMV cycle in lettuce and that mo11 and mo12 are alleles coding for forms of eIF4E unable or less effective to fulfill this role. More generally, the isoforms of eIF4E appear to be host factors involved in the cycle of potyviruses in plants, probably through a general mechanism yet to be clarified.

Nicaise, Valerie; German-Retana, Sylvie; Sanjuan, Raquel; Dubrana, Marie-Pierre; Mazier, Marianne; Maisonneuve, Brigitte; Candresse, Thierry; Caranta, Carole; LeGall, Olivier

2003-01-01

209

Assessment of lettuce quality during storage at low relative humidity using Global Stability Index methodology / Avaliação da qualidade da alface durante o armazenamento em baixa umidade relativa usando o Índice Global da Estabilidade  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Durante a pós-colheita a alface é exposta a condições adversas (baixa umidade relativa) que reduzem a qualidade do vegetal. A fim de avaliar sua vida útil, um grande número de índices de qualidade tem que ser analisado, requerendo um cuidadoso delineamento experimental e um longo consumo de tempo. N [...] este trabalho, o método modificado do Índice Global da Estabilidade foi aplicado para estimar a qualidade da alface manteiga a uma baixa umidade relativa durante o armazenamento diferenciando três zonas (interna, média e externa). Os resultados indicaram que, para a zona externa, os índices mais relevantes foram o conteúdo da umidade relativa, conteúdo da água, ácido ascórbico e a contagem total de micro-organismos mesófilos. Para a zona média, foram conteúdo da umidade relativa, conteúdo da água, clorofila total, ácido ascórbico e, para a interna, conteúdo da umidade relativa, água ligada, conteúdo da água e a contagem total de micro-organismos mesófilos. Foi proposto um modelo matemático entre o Índice Global da Estabilidade e qualidade visual geral para cada zona da alface. Ademais, foi aplicada a distribuição de Weibull para estimar o tempo da vida útil do vegetal, o qual foi: 5, 4 e 3 dias para as zonas interna, média e externa, respectivamente. Quando foi estudado o efeito do tempo de armazenamento para cada zona da alface, todos os índices avaliados na zona externa mostraram diferenças significativas (p Abstract in english During postharvest, lettuce is usually exposed to adverse conditions (e.g. low relative humidity) that reduce the vegetable quality. In order to evaluate its shelf life, a great number of quality attributes must be analyzed, which requires careful experimental design, and it is time consuming. In th [...] is study, the modified Global Stability Index method was applied to estimate the quality of butter lettuce at low relative humidity during storage discriminating three lettuce zones (internal, middle, and external). The results indicated that the most relevant attributes were: the external zone - relative water content, water content , ascorbic acid, and total mesophilic counts; middle zone - relative water content, water content, total chlorophyll, and ascorbic acid; internal zone - relative water content, bound water, water content, and total mesophilic counts. A mathematical model that takes into account the Global Stability Index and overall visual quality for each lettuce zone was proposed. Moreover, the Weibull distribution was applied to estimate the maximum vegetable storage time which was 5, 4, and 3 days for the internal, middle, and external zone, respectively. When analyzing the effect of storage time for each lettuce zone, all the indices evaluated in the external zone of lettuce presented significant differences (p

Ansorena, María Roberta; Agüero, María Victoria; Goñi, María Grabriela; Roura, Sara; Ponce, Alejandra; Moreira, María del Rosario; Di Scala, Karina.

210

Transfer of Metals in Food Chain: An Example with Copper and Lettuce  

Science.gov (United States)

Present study investigated the possible transfer of metals in the food chain (from soil to edible plants). The experiment was done with lettuce Lactuca sativa grown in different types of soil contaminated with copper (Cu2+) in various concentrations, with or without addition of humic substances. The highest content of copper was detected in lettuce samples grown in soils with lower levels of organic matter, thus indicating the importance of soil organics in metal transfer routes and accumulation rates in plants. It was found that copper accumulation in lettuce grown in contaminated soils can be significantly reduced by the addition of humic substances.

Vincevica-Gaile, Zane; Klavins, Maris

2012-12-01

211

SURVEY OF BIOLOGICAL HAZARDS IN THE LETTUCE USED IN COMMERCIAL SNACKS (SANDWICHES) FROM CURITIBA, PR, BRAZIL  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Over the last decades, lettuce has been associated to several foodborne outbreaks. The present study surveyed the microbiological and parasitological contamination of green leaf lettuce used in sandwiches sold in snack bars in Curitiba, Paraná, Brazil. Lettuce was collected before and after commercial washing. Such procedure was made by holding and rotating the wh...

ASSUAN DJAMILA IBRAHIM MOGHARBEL; FELIPE RICHTER REIS; MARIA LUCIA MASSON

2009-01-01

212

Low oxygen levels and light exposure affect quality of fresh-cut Romaine lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Modified atmosphere packaging (MAP) has the potential to extend the shelf-life of fresh-cut lettuce mainly by limiting the oxidation processes. However, exposure to light conditions has been described as causing browning and quality loss. The influence of O(2) partial pressures (pO(2)) and light exposure during storage on the shelf-life of fresh-cut Romaine lettuce was studied. Fresh-cut lettuce was exposed daily during storage to different light conditions: light (24 h), darkness (24 h) and ...

2011-01-01

213

Neural Network Modeling to Predict Shelf Life of Greenhouse Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Greenhouse-grown butter lettuce (Lactuca sativa L. can potentially be stored for 21 days at constant 0°C. When storage temperature was increased to 5°C or 10°C, shelf life was shortened to 14 or 10 days, respectively, in our previous observations. Also, commercial shelf life of 7 to 10 days is common, due to postharvest temperature fluctuations. The objective of this study was to establish neural network (NN models to predict the remaining shelf life (RSL under fluctuating postharvest temperatures. A box of 12 - 24 lettuce heads constituted a sample unit. The end of the shelf life of each head was determined when it showed initial signs of decay or yellowing. Air temperatures inside a shipping box were recorded. Daily average temperatures in storage and averaged shelf life of each box were used as inputs, and the RSL was modeled as an output. An R2 of 0.57 could be observed when a simple NN structure was employed. Since the "future" (or remaining storage temperatures were unavailable at the time of making a prediction, a second NN model was introduced to accommodate a range of future temperatures and associated shelf lives. Using such 2-stage NN models, an R2 of 0.61 could be achieved for predicting RSL. This study indicated that NN modeling has potential for cold chain quality control and shelf life prediction.

Wei-Chin Lin

2009-04-01

214

Occurrence of Cryptosporidium spp. oocysts in low quality water and on vegetables irrigated with low quality water in Kumasi, Ghana  

DEFF Research Database (Denmark)

Protozoan parasites belonging to the genus Cryptosporidium are transmitted e.g. by food and water and may cause severe diarrhoea, dehydration, weight loss and malnutrition. Ingestion of 10 oocysts can lead to infection and pathogenic symptoms. Thus, to characterize Cryptosporidium spp. contamination level of river water, irrigation water and lettuce, 10L of water and 16 lettuce samples were collected four times in the period September â?? October 2013, with weekly intervals from six sample sites in and around Kumasi, Ghana. Oocysts were purified from water by sedimentation for 2 x 48 hours or pulsifying of lettuce followed by immunomagnetic separation and quantification by immunofluorescence microscopy, with sensitivities of 2 and 9%, respectively. Oocysts were stored approx. six weeks at 4C° before enumeration and approx. two weeks on slides at room temperature. Oocysts were subsequently washed off the slides and attempts to characterize Cryptosporidium spp. positive samples were done by PCR amplification and sequencing of the SSU rRNA, the HSP70 and the GP60 genes. Cryptosporidium oocysts were found in 75% of the water samples and on 43% of the lettuce with concentrations of 53 â?? 3,268 per 10L water and 11 â?? 118 oocysts per 15 g of lettuce. Positive water samples on one or more occasions were demonstrated in all water samples from both rivers and farm sites while all farms had positive lettuce samples on all occasions. Rainfall seemingly lowered the concentration of oocysts in water but not on lettuce. Molecular characterization of Cryptosporidium positive samples was unsuccessful, thus no conclusions can be drawn concerning sources of contamination. Nevertheless, the detection of high prevalence and concentration levels of Cryptosporidium oocysts on vegetables consumed raw and in water with direct contact to humans entails a potential risk of infection in humans. Implementation of preventive measures based on this study should be considered and actions taken accordingly.

Petersen, Heidi Huus; Dalsgaard, Anders

215

Reúso de águas residuárias da piscicultura e da suinocultura na irrigação da cultura da alface / Reuse of wastewater from swine and fish activities in the lettuce culture  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Este trabalho teve o objetivo de avaliar o desenvolvimento, a produção e a qualidade sanitária da cultura da alface irrigada com águas residuárias originadas da suinocultura e da piscicultura. Os tratamentos avaliados foram: T1 - alface irrigada com água de origem subterrânea e adubação suplementar; [...] T2 - alface irrigada com água residuária de viveiro de peixes alimentados com ração; T3 - alface irrigada com água residuária originária de lagoa de estabilização de dejetos de suínos, e T4 - água de lagoa de cultivo de algas, alimentada com resíduo de biodigestor de dejeto de suíno. Os tratamentos não apresentaram diferenças significativas para altura da alface, diâmetro da cabeça, comprimento da raiz, massa da raiz, massa total da planta, massa fresca e massa seca; os tratamentos T4 e T2 apresentaram os maiores valores para comprimento da maior folha e número de folhas, respectivamente; em geral, as análises foliares e a extração de macro e micronutrientes pela cultura não apresentaram diferenças significativas; ocorreu contaminação de coliformes fecais e totais em todos os tratamentos; não ocorreu contaminação de Escherichia coli em todos os tratamentos; todos os Coeficientes de Uniformidade de Christiansen (CUC) encontrados foram acima de 85%, exceto para o tratamento T3 que foi de 74,05%; ocorreram alterações químicas no solo proporcionais às características das águas utilizadas nos respectivos tratamentos. Abstract in english The objective of this work was to evaluate development, production and sanitary quality of the irrigated lettuce with wastewater from fish and swine activities. The evaluated treatments was: T1 - lettuce irrigated with water from underground origin and supplemental fertilization; T2 - lettuce irriga [...] ted with wastewater from fish activities and fish fed with ration; T3 - lettuce irrigated with wastewater from swine treated in stabilization lagoon; and T4 - lettuce irrigated with effluent from seaweed lagoon, fed with wastewater from swine activities treated with anaerobic reactor. The treatments did not present significant differences for next culture characteristics: height, diameter head, length root, mass root, total mass plant, green mass and dry mass; the treatments T4 and T2 presented the biggest values for length and number leaf, respectively; in general, leaf analyses and extraction of macro and micronutrients by culture did not present significant differences; contamination by fecal coliforms in all treatments occurred; no contamination by Escherichia coli was observed in all treatments; all the Coefficients of Uniformity of Christiansen (CUC) observed were above 85%, except for treatment T3 where was 74%; chemical alterations in the soil occurred proportional to characteristics of waters used in the treatments.

Baumgartner, Dirceu; Sampaio, Silvio C.; Silva, Tatiana R. da; Teo, Carla R. P. A.; Vilas Boas, Márcio A..

216

Lettuce mosaic virus pathogenicity determinants in susceptible and tolerant lettuce cultivars map to different regions of the viral genome.  

Science.gov (United States)

Full-length infectious cDNA clones were constructed for two isolates (LMV-0 and LMV-E) of Lettuce mosaic virus (LMV), a member of the genus Potyvirus. These two isolates differ in pathogenicity in susceptible and tolerant-resistant lettuce cultivars. In susceptible plants, LMV-0 induces mild mosaic symptoms, whereas LMV-E induces severe stunting, leaf deformation, and a necrotic mosaic. In plants carrying either of the two probably allelic recessive resistance genes mol1 or mol2, LMV-0 is restricted partially to the inoculated leaves. When a systemic invasion does occur, however, symptoms fail to develop. LMV-E overcomes the protection afforded by the resistance genes, resulting in systemic mosaic symptoms. Analysis of the behavior of recombinants constructed between the two virus isolates determined that the HC-Pro protein of LMV-E causes the severe stunting and necrotic mosaic induced by this isolate in susceptible cultivars. In contrast, the ability to overcome mol resistance and induce symptoms in the resistant-tolerant cultivars was mapped to the 3' half of the LMV-E genome. These results indicate that the ability to induce severe symptoms and to overcome the protection afforded by the recessive genes mol1 or mol2 are independent phenomena. PMID:11386376

Redondo, E; Krause-Sakate, R; Yang, S J; Lot, H; Le Gall, O; Candresse, T

2001-06-01

217

Prevalence of Lettuce mosaic virus - common strain on three lettuce producing areas from São Paulo State Prevalência da estirpe comum de Lettuce mosaic virus em três regiões produtoras de alface do estado de São Paulo  

Digital Repository Infrastructure Vision for European Research (DRIVER)

LMV is one of the most important pathogens of lettuce worldwide. Based on their ability to overcome the resistance genes mo1¹ and mo1² in lettuce, isolates can be divided in two types: LMV-Most, which can infect and are seed-borne in cultivars containing the mo1 gene and LMV-Common, which do not cause symptoms on these cultivars and are seed transmitted only in susceptible cultivars. To evaluate the occurrence of these two types of LMV isolates, a survey was carried out during 2002-2005 in ...

Ana Carolina Firmino; Renate Krause-Sakate; Marcelo Agenor Pavan; Norberto da Silva; Sérgio Minoru Hanai; Roberto Hiroto Anbo; Thomas Nietzsche; Olivier Le Gall

2008-01-01

218

Researches Regarding the Influence of Cold Storage on the Chlorophyll Content in Lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the present investigations was to determine the effect of the cold storage period on the content of chlorophylls in the leaves of lettuce and arugula (rucola. The research material consisted in two types of lettuce (Lactuca sativa L. var. capitata; Lactuca sativa L. var. crispa and arugula (Eruca sativa purchased from supermarkets in Timisoara. The quantitative determination of chlorophyll pigments in leaves (SPAD was made by chlorophyll meter (SPAD 502 Konica-Minolta. During the few days cold storage at a temperature of 4ºC, the content of chlorophyll in the leaf significantly decreased, compared with that in the control group. After 3 days of cold storage arugula and lettuce (Lactuca sativa var. capitata values of chlorophyll content differ statistically very significantly (p<0.001 from the values found in the control group which for lettuce (Lactuca sativa L. var. crispa differs statistically significant (p < 0.05.

Iuliana Cretescu

2014-05-01

219

Microbial antagonists of Escherichia coli O157:H7 on fresh-cut lettuce and spinach.  

Science.gov (United States)

Fresh-cut lettuce and spinach can become contaminated with pathogens at numerous points from the field to the retail market. Natural microflora present on fresh produce may help reduce the pathogen load. The objective of this study was to isolate natural microflora from fresh-cut iceberg lettuce and baby spinach and to determine whether these bacteria were antagonistic toward Escherichia coli O157:H7. Samples were collected under conditions that mimicked actual practices between production and retail sale. Evidence of naturally occurring microorganisms on fresh lettuce (295 isolates) and spinach (200 isolates) and of possible antagonistic activity toward E. coli O157:H7 was documented. Inhibitory activity by several isolates was due to either acid production or antimicrobial peptides. Bacteria with inhibitory activity were isolated from every step in the processing and handling of the fresh-cut iceberg lettuce and baby spinach. PMID:19681287

Johnston, Michael A; Harrison, Mark A; Morrow, Ruth A

2009-07-01

220

Insecticide residues in head lettuce, cabbage, Chinese cabbage, and broccoli grown in fields.  

Science.gov (United States)

The residues of four insecticides belonging to different families were studied on head lettuce (Lactuca sativa L. var. capitata L.), cabbage (Brassica oleracea Linn. var. capitata DC.), Chinese cabbage (Brassica pekinensis Skeels), and broccoli (Brassica oleracea var. italica) after pesticide application. To reduce application variability, a tank mix of acetamiprid 20% SP, chlorpyrifos 22.5% EC, deltamethrin 2.4% SC, and methomyl 40% SP was applied at recommended and double doses. Initial deposits of all pesticides on head lettuce were higher than those of the other three crops. The residues of chlorpyrifos and deltamethrin were higher than the maximum residue limits (MRLs) at recommended preharvest intervals (PHIs) on head lettuce and Chinese broccoli treated with higher doses. The residues of methomyl on head lettuce also showed the same phenomenon. PMID:24684565

Chen, Miao-Fan; Chen, Jung-Fang; Syu, Jing-Jing; Pei, Chi; Chien, Hsiu-Pao

2014-04-23

 
 
 
 
221

DEMONSTRATION OF IRRIGATION RETURN FLOW WATER QUALITY CONTROL IN THE MESILLA VALLEY, NEW MEXICO  

Science.gov (United States)

A 182-ha operating farm was used to demonstrate the water pollution control benefits of implementing improved irrigation management techniques and structures. The commodity crops produced on the farm included wheat, tomatoes, cotton, lettuce, peppers, chiles, grain sorghum, and a...

222

Characterization of Distinct Tombusviruses that Cause Diseases of Lettuce and Tomato in the Western United States.  

Science.gov (United States)

A soilborne disease of lettuce, associated with necrosis and dieback, has been found with increasing frequency in California and Arizona over the last 10 years. An isometric virus, serologically related to Tomato bushy stunt virus (TBSV), was consistently isolated from lettuce plants with these disease symptoms. Back-inoculation to healthy lettuce plants and subsequent reisolation of the virus from symptomatic lettuce leaves suggested that this virus was the causal agent of this disease. A tombusvirus was also associated with a necrosis disease of greenhouse-grown tomatoes in Colorado and New Mexico. Complementary DNA representing the 3' end of viral genomic RNAs recovered from diseased lettuce and tomato plants had identical nucleotide sequences. However, these sequences were divergent (12.2 to 17.1%) from sequences of the previously described strains of TBSV, Petunia asteroid mosaic virus (PAMV), Artichoke mottled crinkle virus, and Carnation Italian ringspot virus. Additional tombusvirus isolates were recovered from diseased lettuce and tomato plants and these were most closely related to the TBSV-cherry strain (synonymous with PAMV) and to Cucumber necrosis virus based on comparison of 3'-end sequences (0.1 to 0.6% and 4.8 to 5.1% divergence, respectively). Western blot analysis revealed that the new tombusvirus isolated from diseased lettuce and tomato plants in the western United States is serologically distinct from previously described tombusvirus species and strains. Based on genomic and serological properties, we propose to classify this virus as a new tombusvirus species and name it Lettuce necrotic stunt virus. PMID:18944038

Obermeier, C; Sears, J L; Liu, H Y; Schlueter, K O; Ryder, E J; Duffus, J E; Koike, S T; Wisler, G C

2001-08-01

223

Effect of heat stress on the MDA, proline and soluble sugar content in leaf lettuce seedlings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

High temperature stress on different varieties of lettuce seedlings in MDA, proline and soluble sugar content were studied. The results were as follows : With the stress temperature, varieties of leaf lettuce seedlings in the MDA, proline and soluble sugar content gradually increased; Different varieties had the most significant difference in 38/33?(d/n). The increase of heat-resistant varieties on proline and soluble sugar content was quick and high, while its increase in MDA content w...

Yingyan Han; Shuangxi Fan; Qiao Zhang; Yanan Wang

2013-01-01

224

Nitrogenase Activity of Pseudomonas corrugata Isolated from Egyptian Lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the present study an isolate capable of root colonization of Egyptian Lettuce was isolated from the roots after selective enrichment. The isolated strain was identified as Pseudomonas corrugata by using Biochemical and Biolog identification system. The isolate has been found to be positive for nitrogenase activity. This root-colonized bacterium has not been previously isolated from Egyptian Lettuce and could be used as a bio-fertilizer.

Abada, Emad A.

2006-01-01

225

Transgenic lettuce seedlings carrying hepatitis B virus antigen HBsAg  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The obtainment of transgenic edible plants carrying recombinant antigens is a desired issue in search for economic alternatives viewing vaccine production. Here we report a strategy for genetic transformation of lettuce plants (Lactuca sativa L.) using the surface antigen HBsAg of hepatitis B virus. Transgenic lettuce seedlings were obtained through the application of a regulated balance of plant growth regulators. Genetic transformation process was acquired by cocultivation of cotyledons wit...

Jackson Marcondes; Ekkehard Hansen

2008-01-01

226

The Comparison of Ammonium or Nitrate-Grown Lettuce and Spinach in a Hydroponic System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Most plant species are sensitive to high ammonium concentrations. In this experiment the sensitivity of lettuce and spinach to ammonium was investigated. In a factorial experiment with framework of a completely randomized design with two factors, nitrogen form (ammonium and nitrate) and plant species (lettuce and spinach), and three replications seeds were germinated in a mixture of perlite, sand and clay in soil-maid pots. After two weeks, the seedlings at two true-leaf stage were then trans...

2010-01-01

227

Preharvest and postharvest factors related to off-odours of fresh-cut iceberg lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of different preharvest and postharvest factors affecting off-odour development of fresh-cut iceberg lettuce in low-O-2 modified atmospheres (MA) was investigated. Fresh-cut iceberg lettuce developed undesirable off-odours under low O-2 and elevated CO2 atmospheres. A strong relationship between CO2 concentration and off-odour development was observed. Significant differences in off-odour development existed among different cultivars in two harvests in consecutive years. The inf...

2013-01-01

228

The effect of growth regulators on the healthiness, growth and sprouting of inflorescence shoot of lettuce  

Directory of Open Access Journals (Sweden)

Full Text Available Investigations were carried out under greenhouse conditions on lettuce cv. Ilanka. Seeds were sown in January 1982 and 1984. Lettuce was cultivated to middle of June up to full flowering time. It was found that the preparation fenoprop (2,4,5-trichlorofenoxypropionic acid as a dimethylamine salt in concentrations of 10, 20 and 50 mg·dm-3 significantly decreased latex tipburn symptoms. Fenoprop increased the healthiness of the plants because treated plants were also less attacked by grey mould Botritis sp. Fenoprop also inhibited head formation in lettuce, but the weight of these plants was never smaller than control ones. Sometimes the weight of plants treated with fenoprop was significantly higher than of the control plants. Lettuce plants without heads had bolted earlier. Only the concentration of 100 mg·dm-3 of fenoprop retarded plant growth. The effect of K-NAA (potassium salt of ?-naphthaleneacetic acid on lettuce was weaker than the effect of fenoprop. After K-NAA treatment at a concentration of 25 mg·dm-3, lettuce plants formed normal heads but latex tipburn symptoms were retarded.

Jan Borkowski

1988-12-01

229

Isolation of phenolic compounds from iceberg lettuce and impact on enzymatic browning.  

Science.gov (United States)

Enzymatic browning is generally reported as the reaction between phenolic substances and enzymes. The quality of iceberg lettuce is directly linked to this discoloration. In particular, the color change of lettuce stems considerably reduces consumer acceptance and thus decreases sales revenue of iceberg lettuce. Ten phenolic compounds (caffeic acid, chlorogenic acid, phaseolic acid, chicoric acid, isochlorogenic acid, luteolin-7-O-glucuronide, quercetin-3-O-glucuronide, quercetin-3-O-galactoside, quercetin-3-O-glucoside, and quercetin-3-O-(6?-malonyl)-glucoside) were isolated from Lactuca sativa var. capitata by multilayer countercurrent chromatography (MLCCC) and preparative high-performance liquid chromatography (HPLC). In addition, syringin was identified for the first time in iceberg lettuce. This polyphenolic ingredient was previously not mentioned for the family of Cichorieae in general. The purity and identity of isolated compounds were confirmed by different NMR experiments, HPLC-DAD-MS, and HR-MS techniques. Furthermore, the relationship between discoloration of iceberg lettuce and enzymatic browning was thoroughly investigated. Unexpectedly, the total concentration of phenolic compounds and the activity of polyphenol oxidase were not directly related to the browning processes. Results of model incubation experiments of plant extract solutions led to the conclusion that in addition to the typical enzymatic browning induced by polyphenol oxidases, further mechanisms must be involved to explain total browning of lettuce. PMID:23473017

Mai, Franziska; Glomb, Marcus A

2013-03-20

230

Phenolic contents of lettuce, strawberry, raspberry, and blueberry crops cultivated under plastic films varying in ultraviolet transparency  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The levels of health-related phytochemicals were determined in lettuce leaf and in strawberry, raspberry and blueberry fruits grown in near-commercial conditions under plastic films of three different UV transparencies. In the red lettuce Lollo Rosso, total phenolics, anthocyanin, luteolin and quercetin levels were all raised by changing from a UV blocking film to a film of low UV transparency, and to a film of high UV transparency. The related green lettuce, Lollo Biondo, cultivated under t...

Ordidge, Matthew; Garci?a-maci?as, P.; Battey, Nicholas Hugh; Gordon, Michael Harry; Hadley, Paul; John, Philip; Lovegrove, Julie Anne; Vysini, E.; Wagstaffe, Alexandra

2010-01-01

231

Effect of Heat Schock on Browning-Related Enzymes in Minimally Processed Iceberg Lettuce and Crude Extracts  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of heat shock on PPO and POD activity in minimally processed Iceberg lettuce was examined during storage (10 days). The results were compared with the effect of temperature on crude extracts of these enzymes (in vitro analysis). Fresh-cut lettuce washed at 50 °C showed significantly lower PPO and POD activity throughout storage than lettuce washed at 4 °C and 25 °C. These results were consistent with a sensory analysis in which the panellists found the lowest browning sc...

2005-01-01

232

Radiotracer studies of maneb residues in lettuce plants  

International Nuclear Information System (INIS)

Lettuce plants have received different treatments of 14C-maneb at variable time. A cleaning is made to determine the foliar surface residues. The analysis of CS2 showed relatively important amount especially for lots which have received 4 treatments (10,3ppm and 6,49ppm). The amounts found after combustion have showed increasing amounts, proportionally to the number of treatments. The analysis of ETU revealed a presence only for lots which have received several treatments (3 and 4). The analysis by TLC showed many metabolites. Two of them have been identified (ETU, EU). Interfoliar migration of 14C product occurred between treated leaves and untreated leaves of the same plant

1990-01-01

233

Characterization of monophenolase activity of polyphenol oxidase from iceberg lettuce.  

Science.gov (United States)

Polyphenol oxidase (EC 1.14.18.1), a thylakoid membrane-bound enzyme, was isolated by sonication of osmotically shocked chloroplasts from iceberg lettuce (Lactuca sativa). The enzyme showed monophenolase activity when assayed on (p-hydroxyphenyl)propionic acid with 3-methyl-2-benzothiazolinone hydrazone in a reliable continuous spectrophotometric method, with high sensitivity, accuracy, and precision. The monophenolase activity showed a lag period before the steady-state rate (V(ss)) was reached. Both kinetic parameters, the lag period and the steady-state rate, depended on the pH, the enzyme and substrate concentrations, and the presence of catalytic amounts of o-diphenol. This activity shows inhibition by high substrate concentration. The experimental results correspond with the mechanism previously described for PPO from other sources. Kinetic constants K(m), V(max), and K(i) were determined. PMID:10563992

Chazarra, S; García-Carmona, F; Cabanes, J

1999-04-01

234

EFFECTS OF TRICHODERMA HARZIANUM ON LETTUCE IN PROTECTED CULTIVATION  

Directory of Open Access Journals (Sweden)

Full Text Available Effects of Trichoderma harzianum on lettuce seedling development, plant quality characteristics at harvest and yield were investigated. Experiments were carried out in an unheated glasshouse where composted straw bales were used as the growing medium. A part of the experiment was carried out in a high tunnel where soil was the growing medium. Seeds were sown in peat and seedlings were grown in the presence of T. harzianum at dosages of 5, 10 and 15 g m-2 applied at sowing. Among the seedling characteristics studied only seedling fresh weight of cv. Yedikule was increased significantly. Effect of T. harzianum on lettuce yield was not statistically significant. In the glasshouse, the straw bales were composted with two different methods. In the method I, 134g N, 13g P, 25g K, and 76 g Ca, and in the method II, 54.3g N, 26g P, and 22.6g Ca were provided to the straw bales. The marketable yield of cv. Yedikule from the straw bales of method I was 503 g plant-1 from 15 g m-2 whereas the control remained the lowest with 425 g plant-1. For the same cultivar grown on the method II the highest marketable yield was obtained from 10 g m-2 with 303 g plant-1 compared to the control (150 g plant-1. The cv. Coolguard grown in the straw bales was tested only with the method I and the highest yield was from 15 g m-2 with 570 g plant-1 compared to 551 g plant-1 from the control. Dosage main effect regarding marketable yield in soil in the tunnel was not significant.

Ugur Bal

2008-07-01

235

Envelhecimento acelerado em sementes de alface Accelerated aging in lettuce seeds  

Directory of Open Access Journals (Sweden)

Full Text Available Objetivou-se adequar a metodologia do teste de envelhecimento acelerado para avaliação do potencial fisiológico de sementes de quatro lotes dos genótipos de alface 'Babá de verão', 'Tainá' e 'Vera', aplicando-se o método tradicional e com o uso de solução saturada de NaCl. Para tal, as sementes foram submetidas à determinação do teor de água, testes de germinação e vigor (primeira contagem, condutividade elétrica, emergência em bandeja, índice de velocidade de emergência incluindo o teste de envelhecimento acelerado, conduzido nos períodos de 24, 48, e 72 horas, a 41°C com e sem solução saturada de NaCl. O experimento foi conduzido em delineamento inteiramente casualizado com quatro repetições. Os procedimentos tradicional e com o uso da solução saturada de NaCl por 72 horas foram sensíveis em estratificar os lotes em níveis de vigor, além de estarem de acordo com os demais testes utilizados. Portanto, o envelhecimento acelerado de sementes de alface deve ser feito utilizando o período de 72 horas, podendo ser realizado tanto pelo método tradicional quanto pelo método da solução saturada de NaCl.The objective was to adapt the methodology of the accelerated aging test to evaluate the physiological potential of seeds of four lots of lettuce genotypes 'Babá de verão', 'Tainá' and 'Vera' applying the traditional method and using a saturated NaCl solution. So, the seeds were subjected to determination of water content, seed germination and vigor (first count, electrical conductivity, speed emergency index, emergency tray including the accelerated aging test conducted in periods of 24, 48, 72 hours at 41°C with and without saturated solution of NaCl. The experiment was conducted in a randomized design with four replications. The accelerated aging traditional and saturated solution of NaCl by 72h was more sensitive to stratify the lots in vigor levels. Therefore, accelerated aging of seeds of lettuce should be made using the period of 72h and can be accomplished either by the traditional method and by the saturated NaCl solution method.

Rafael Marani Barbosa

2011-11-01

236

Envelhecimento acelerado em sementes de alface / Accelerated aging in lettuce seeds  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Objetivou-se adequar a metodologia do teste de envelhecimento acelerado para avaliação do potencial fisiológico de sementes de quatro lotes dos genótipos de alface 'Babá de verão', 'Tainá' e 'Vera', aplicando-se o método tradicional e com o uso de solução saturada de NaCl. Para tal, as sementes fora [...] m submetidas à determinação do teor de água, testes de germinação e vigor (primeira contagem, condutividade elétrica, emergência em bandeja, índice de velocidade de emergência) incluindo o teste de envelhecimento acelerado, conduzido nos períodos de 24, 48, e 72 horas, a 41°C com e sem solução saturada de NaCl. O experimento foi conduzido em delineamento inteiramente casualizado com quatro repetições. Os procedimentos tradicional e com o uso da solução saturada de NaCl por 72 horas foram sensíveis em estratificar os lotes em níveis de vigor, além de estarem de acordo com os demais testes utilizados. Portanto, o envelhecimento acelerado de sementes de alface deve ser feito utilizando o período de 72 horas, podendo ser realizado tanto pelo método tradicional quanto pelo método da solução saturada de NaCl. Abstract in english The objective was to adapt the methodology of the accelerated aging test to evaluate the physiological potential of seeds of four lots of lettuce genotypes 'Babá de verão', 'Tainá' and 'Vera' applying the traditional method and using a saturated NaCl solution. So, the seeds were subjected to determi [...] nation of water content, seed germination and vigor (first count, electrical conductivity, speed emergency index, emergency tray) including the accelerated aging test conducted in periods of 24, 48, 72 hours at 41°C with and without saturated solution of NaCl. The experiment was conducted in a randomized design with four replications. The accelerated aging traditional and saturated solution of NaCl by 72h was more sensitive to stratify the lots in vigor levels. Therefore, accelerated aging of seeds of lettuce should be made using the period of 72h and can be accomplished either by the traditional method and by the saturated NaCl solution method.

Rafael Marani, Barbosa; Denis Santiago da, Costa; Marco Eustáquio de, Sá.

237

Escherichia coli survival in lettuce fields following its introduction through different irrigation systems.  

Science.gov (United States)

Aims:? This study aimed to assess the contamination risk of Escherichia coli in commercial lettuce grown under three different irrigation systems (overhead sprinkler, subsurface drip and surface furrow). Methods and Results:? Three replicated field trials were conducted. In an initial trial, we consistently observed higher mesophilic bacteria counts under sprinkler irrigation but visual quality was found to be dependent on the water potential of leaves at harvest. Further, in the other two trials, E. coli K-12 strains LMM1010 and ATCC 25253, was injected into the water stream of the different irrigation systems to determine survival in the field. Results showed that product samples were positive for E. coli up to 7?days when using sprinkler irrigation, whereas only one product sample was found positive for E. coli when using other irrigation methods. Survival of bacteria in soil persisted longer in furrow-irrigated areas, ranging from an estimated 17?days in winter months to 5?days during the warmer summer periods. This finding combined with results from a parallel 3-year survey of canal waters indicate that while highest risk of finding E. coli in irrigation water is in warmer months, the survival in soil is lower during the same time period. Conclusions:? Our results in a study set under common commercial conditions confirmed the enhanced risk of E. coli contamination when using sprinkle irrigation. Furthermore, E. coli persistence in furrow-irrigated soil validates the importance of an early irrigation termination for both sprinkler and furrow methods. Significance and Impact of the Study:? Stringent monitoring and in-field food safety controls should be emphasized during the last few days before harvest. PMID:21214696

Fonseca, J M; Fallon, S D; Sanchez, C A; Nolte, K D

2011-01-01

238

Methods to Estimate Lettuce Evapotranspiration in Greenhouse Conditions in the Central Zone of Chile Métodos de Estimación de la Evapotranspiración de un Cultivo de Lechuga en Condiciones de Invernadero, Zona Central de Chile  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study evaluates five methods to estimate crop evapotranspiration in greenhouse conditions. It compares their performance in relation to the evapotranspiration directly determined from water balance measurements (ETlys) in an irrigated lettuce (Lactuca sativa L.) crop during 9 weeks. Daily values of the reference evapotranspiration (ETo) from Class A pan (CAP), Piche atmometers (ATM), Andersson evaporimeters (ANE), FAO-Radiation (FRE) and FAO-Penman-Monteith (PME) equations were compared....

Manuel Casanova P; Ingmar Messing; Abraham Joel; Alberto Cañete M

2009-01-01

239

Preliminary Studies on Growth and Fresh Weight of Lettuce (Lactuca sativa) as Affected by Clay Pot Irrigation and Spacing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An experiment (Completely Randomized Design) was set up to determine the effects of Clay Pot Sub-surface Irrigation (CPSI) and spacing on the growth and fresh weight of lettuce (Lactuca sativa). The treatments were: CPSI with spacing; 15x15 cm, 20x20 cm and 30x30 cm. Control treatments were Watering Can Irrigation (WCI) with the same spacing as above. Treatments were replicated three times given a total of 18 experimental units. Eighteen large enamel basins of 50/20 cm (diameter/height...

Abdul-Halim Abubakari; George Nyarko; Maalinyuur Sheila

2011-01-01

240

Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps  

Science.gov (United States)

Growing vegetable crops in space will be an essential part of sustaining astronauts during long-term missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop production, there have also been recent interests in analyzing the subtle effects of green light on plant growth, and to determine if it serves as a source of growth enhancement or suppression. A comparative study was performed on two short cycle crops of lettuce (Outredgeous) and radish (Cherry Bomb) grown under two light treatments. The first treatment being red and blue LEDs, and the second treatment consisting of white fluorescent lamps which contain a portion of green light. In addition to comparing biomass production, physiological characterizations were conducted on how the light treatments influence morphology, water use, chlorophyll content, and the production of A TP within plant tissues.

Mickens, Matthew A.

2012-01-01

 
 
 
 
241

Whole-head washing, prior to cutting, provides sanitization advantages for fresh-cut Iceberg lettuce (Latuca sativa L.).  

Science.gov (United States)

The efficacy of two leafy produce wash methods, the traditional cutting-before-washing process and a new washing-before-cutting method, on reduction of Escherichia coli O157:H7 inoculated on Iceberg lettuce was compared. The washing tests were conducted in a pilot-scale washer using combinations of water, chlorine, peroxyacetic acid, and ultrasound. The washing-before-cutting process recorded an E. coli O157:H7 count reduction 0.79-0.80 log?? CFU/g higher than that achieved with the cutting-before-washing process in treatments involving only a sanitizer. When ultrasound was applied to the washing-before-cutting process, a further improvement of 0.37-0.68 log?? CFU/g in microbial count reduction was obtained, reaching total reductions of 2.43 and 2.24 log?? CFU/g for chlorine and peroxyacetic acid washes, respectively. PMID:24704862

Palma-Salgado, Sindy; Pearlstein, Arne J; Luo, Yaguang; Park, Hee Kyung; Feng, Hao

2014-06-01

242

Green remediation of tetracyclines in soil-water systems  

Directory of Open Access Journals (Sweden)

Full Text Available The presence of tetracyclines in soil and surface water is an emerging concern. The present study was undertaken to investigate remediation of tetracylines (tetracycline (TC, oxytetracycline (OTC and chlortetracycline (CTC from aqueous solution using vetiver grass, water lettuce, and sunflower and root exudates of water lettuce, sunflower and from soil by tomato, Indian mustard and carrot plant. The data of this study denote that vetiver grass, water lettuce, sunflower remedy tetracyclines from water. The remediation % after 63 days of treatment was 87-61 for TC; 88-68 for OTC and 87-68 for CTC. The remediation of tetracyclines at lower concentration of antibiotics in presence of root exudates of water lettuce and sunflower was more than 99% and remediation was faster than water lettuce or sunflower. The remediation of tetracyclines from aqueous solution may be due to oxidation of-OH group(s of tetracycline through a process that is thought to involve reactive oxygen intermediates and/or role of peroxidase enzyme. The plant crops viz., tomato, Indian mustard and carrot can remedy 41%-72% of amended tetracyclines. The maximum bioaccumulation of TC and CTC was in Indian mustard and OTC was maximally bioaccumulated in tomato.  

Om Prakash Bansal

2013-12-01

243

Occurrence of Cryptosporidium spp. oocysts in low quality water and on vegetables irrigated with low quality water in Kumasi, Ghana  

DEFF Research Database (Denmark)

Protozoan parasites belonging to the genus Cryptosporidium are transmitted e.g. by food and water and may cause severe diarrhoea, dehydration, weight loss and malnutrition. Ingestion of 10 oocysts can lead to infection and pathogenic symptoms. Thus, to characterize Cryptosporidium spp. contamination level of river water, irrigation water and lettuce, 10L of water and 16 lettuce samples were collected four times in the period September â?? October 2013, with weekly intervals from six sample sites in and around Kumasi, Ghana. Oocysts were purified from water by sedimentation for 2 x 48 hours or pulsifying of lettuce followed by immunomagnetic separation and quantification by immunofluorescence microscopy, with sensitivities of 2 and 9%, respectively. Oocysts were stored approx. six weeks at 4C° before enumeration and approx. two weeks on slides at room temperature. Oocysts were subsequently washed off the slides and attempts to characterize Cryptosporidium spp. positive samples were done by PCR amplification and sequencing of the SSU rRNA, the HSP70 and the GP60 genes. Cryptosporidium oocysts were found in 75% of the water samples and on 43% of the lettuce with concentrations of 53 â?? 3,268 per 10L water and 11 â?? 118 oocysts per 15 g of lettuce. Positive water samples on one or more occasions were demonstrated in all water samples from both rivers and farm sites while all farms had positive lettuce samples on all occasions. Rainfall seemingly lowered the concentration of oocysts in water but not on lettuce. Molecular characterization of Cryptosporidium positive samples was unsuccessful, thus no conclusions can be drawn concerning sources of contamination. Nevertheless, the detection of high prevalence and concentration levels of Cryptosporidium oocysts on vegetables consumed raw and in water with direct contact to humans entails a potential risk of infection in humans. Implementation of preventive measures based on this study should be considered and actions taken accordingly.

Petersen, Tobias B; Petersen, Heidi H.

244

Frequência de Lettuce big-vein associated virus e Mirafiori lettuce big-vein virus em Plantas de alface no Estado de São Paulo e transmissão através de extrato vegetal e solo Frequency of Lettuce big-vein associated virus and Mirafiori lettuce big-vein virus in symptomatic and assymptomatic lettuce plants and sap and soil transmission  

Directory of Open Access Journals (Sweden)

Full Text Available A presença de sintomas de 'big vein' ou engrossamento das nervuras em alface e a associação do Lettuce big-vein associated virus (LBVaV e Mirafiori lettuce big-vein virus (MLBVV foram verificadas por RT-PCR utilizando-se oligonucleotídeos específicos para ambos os vírus. Foram coletadas 366 plantas sintomáticas nas regiões de Bauru, Campinas e Mogi das Cruzes no estado de São Paulo nos meses de junho e setembro de 2004 e abril e julho de 2005, e 18 plantas assintomáticas na região de Mogi das Cruzes no mês de dezembro de 2004. Infecção mista do LBVaV e MLBVV foi detectada em 76,2% das plantas sintomáticas, em 11,5% somente o MLBVV foi detectado e em 6,6% somente o LBVaV. Nas plantas assintomáticas coletadas em dezembro na região de Mogi das Cruzes, em áreas de alta incidência da doença durante o inverno, foi detectada a presença de MLBVV em 9 amostras e LBVaV em 7 amostras. Quatro dessas amostras apresentaram infecção mista, indicando que o desenvolvimento de sintomas depende de fatores abióticos, como temperatura. A inoculação via extrato vegetal a partir de plantas de alface com infecção mista pelo MLBVV e LBVaV foi realizada a 16°C/ 10°C (dia/noite e fotoperíodo de 11 horas, verificando-se que o MLBVV foi transmitido para Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa e para as cultivares de alface Trocadero e White Boston, enquanto o LBVaV foi transmitido apenas para a alface White Boston. Entretanto, nenhuma destas plantas apresentou sintomas da doença, com exceção de C. quinoa que apresentou sintomas de lesões locais. Plantio em solo proveniente de áreas com histórico da doença de Mogi das Cruzes permitiu a transmissão do LBVaV para alface cv. White Boston e do MLBVV para alface cv. Trocadero e White Boston, embora apenas a cv. White Boston tenha apresentado sintomas da doença. Em conjunto, estes resultados demonstram a dificuldade de transmissão de ambos os vírus, mesmo em condições de laboratório.The occurrence of big vein disease symptoms and the association of Lettuce big-vein associated virus (LBVaV and Mirafiori lettuce big-vein virus (MLBVV was evaluated by RT-PCR using specific primers for both viruses. A total of 366 symptomatic plants were collected during June and September 2004 and during April and July 2005 at Bauru, Campinas and Mogi das Cruzes in São Paulo state, and 18 symptomless plants were collected in Mogi das Cruzes on December 2004. Mixed infection was detected in 76,2% of the symptomatic plants, 11,5% had only MLBVV and 6,6% had only LBVaV. In the symptomless plants collected in areas with high incidence of the disease throughout the winter, MLBVV was found in 9 plants and LBVaV in 7 plants. Four plants had both viruses, indicating that symptom development depends on abiotic factors, such as temperature. Plants with MLBVV and LBVaV (mixed infection were used as source of virus in a host range assay at 16C/ 10°C (day/ night and 11h light period. MLBVV was transmitted to Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa and lettuce cv. Trocadero and White Boston, while LBVaV was transmitted only to lettuce cv. White Boston. No symptons could be verified for these plants with the exception of C. quinoa that showed local lesions. Transmission through soil in areas with high incidence of the disease was observed for LBVaV to lettuce cv. White Boston and MLBVV for lettuce cv. Trocadero and White Boston, but only cv. White Boston showed symptoms. Together, these results demonstrate the difficulties in transmitting both viruses, even under controlled laboratory conditions.

Márcio Martinello Sanches

2007-12-01

245

Understanding E. coli internalization in lettuce leaves for optimization of irradiation treatment.  

Science.gov (United States)

Irradiation penetrates food tissues and effectively reduces the number of food microorganisms in fresh produce, but the efficacy of the process against internalized bacteria is unknown. The objective of this study was to understand the mechanisms of pathogen colonization of plants relative to lettuce leaf structures so that radiation treatment of fresh leafy vegetables can be optimized. Leaves of iceberg, Boston, green leaf, and red leaf lettuces were cut into pieces, submerged in a cocktail mixture of two isolates of Escherichia coli (Rifampicin resistant), and subjected to a vacuum perfusion process to force the bacterial cells into the intercellular spaces in the leaves. Sixty bags containing 20g of lettuce each were tested. The inoculated leaves were gamma irradiated (Lanthanum-140, 0.16kGy/h) at 0.25-1.0-kGy (surface dose values), with increments of 0.25kGy at 15 degrees C. Microbial analysis was performed right after irradiation, including non-irradiated leaf pieces (controls). A dose uniformity ratio (max/min dose) of 2.8 was set to confirm the effect of non-uniform dose distribution. Calculated D(10)-values varied between 48 and 62% based on the dose distribution from the entrance dose. However, despite the subtle differences in composition and structure among the four lettuce varieties, the D(10)-values were not significantly different. Irradiation up to 1.0-kGy resulted in 3-4-log reduction of internalized E. coli on the lettuce leaves. The SEM images suggest that the contamination sites of pathogens in leafy vegetables are mainly localized on crevices and into the stomata. This study shows that irradiation effectively reduces viable E. coli cells internalized in lettuce, and decontamination is not influenced by lettuce variety. Ionizing irradiation effectively reduced the population of internalized pathogen in a dose-dependent manner and could be used as an effective killing step to mitigate the risk of foodborne disease outbreaks. PMID:19733930

Gomes, Carmen; Da Silva, Paulo; Moreira, Rosana G; Castell-Perez, Elena; Ellis, E Ann; Pendleton, Michael

2009-11-15

246

Economic analysis of organic greenhouse lettuce production in Turkey / Análise econômica da produção orgânica de alface em estufas na Turquia  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Preocupações sanitárias e ambientais têm atraído a atenção para a prática da agricultura orgânica como meio de proteger o balanço ambiental e produzir sem danificar o ambiente. Este estudo objetiva determinar a viabilidade econômica da produção em estufa da alface (Latuca sativa L.) em um ensaio de [...] campo, a fim de incentivar a produção orgânica de vegetais na área de preservação do Reservatório Tahtali, projetado como o único recurso hídrico de Izmir, a terceira maior cidade da Turquia. Uma estufa de tubos galvanizados (384 m²), ancorados e cobertos com polietileno, foi analisada para identificar procedimentos operacionais padronizados e determinar custos unitários de construção e operação. Alfaces orgânicas foram produzidas no outono de 2001-2002, testando diferentes aplicações de sobras compostadas e esterco de granja avícola como fertilizantes orgânicos (30 e 50 t ha-1), com ou sem a adição de fertilizantes comerciais bacterianos ou algais. A análise econômica foi feita de acordo com as quantidades de fertilizantes utilizadas. A determinação da lucratividade foi feita com base na análise de dados de custos, produtividade e preço. O lucro líquido obtido da produção orgânica de alface em estufa variou entre US$ 0.376 e US$ 0.901 m-2. Abstract in english Health issues and environmental concerns have drawn the attention to organic agriculture aiming to protect the natural balance and to produce without damaging the environment. This study aims determining economic feasibility of organic greenhouse lettuce (Lactuca sativa L.) in an on farm trial, to f [...] oster organic greenhouse vegetable production in the preservation area of Tahtali Dam, projected as the sole water resource of Izmir, Turkey's third largest. A 384 m² greenhouse, constructed of galvanized metal tubing anchored and covered with a polyethylene was analyzed to identify typical operation procedures, and to determine unitary construction and operation cost. Organic lettuces were produced during autumn season of 2001-2002, testing different organic fertilizer applications, including two rates of farmyard and poultry manure (30 and 50 t ha-1) with and without two organic fertilizers based on either bacteria or algae. Economical analysis was performed according to different organic fertilizer applications. Cost, yield, and price data were analyzed to determine the profitability of a typical operation. Net return obtained from organic lettuce growing ranged between us $ 0.376 and us $ 0.901 m-2, as a result of different fertilizer applications.

Sait, Engindeniz; Yuksel, Tuzel.

247

Consórcios alface-cenoura e alface-rabanete sob manejo orgânico Intercropping of lettuce-carrot and lettuce-radish under organic management  

Directory of Open Access Journals (Sweden)

Full Text Available Dois experimentos foram conduzidos, por dois anos consecutivos, em Seropédica, RJ, com o objetivo de avaliar o desempenho agronômico dos consórcios das cultivares de alface 'Regina 71' (lisa e 'Verônica' (crespa com cenoura 'Brasília' e rabanete 'Híbrido nº 19', sob manejo orgânico, assim como determinar as quantidades de macronutrientes exportadas. O delineamento experimental usado foi o de blocos ao acaso, com quatro repetições. No primeiro experimento, os tratamentos consistiram de alface crespa em consórcio com cenoura, alface crespa em consórcio com rabanete e os cultivos solteiros. No segundo experimento, usou-se alface lisa em lugar da crespa. Nos consórcios entre cenoura e alface crespa ou lisa, foram observados índices de uso eficiente da terra, superiores a 1,60. Nos consórcios de rabanete com alface, crespa ou lisa, esses índices foram de 1,54 e 1,27, respectivamente. As quantidades de nutrientes extraídas do sistema pelos produtos colhidos foram inferiores aos aportes efetuados, evidenciando a viabilidade de qualquer dos consórcios avaliados.Two experiments were carried out, in two consecutive years, at Seropédica, RJ, Brazil, aiming to evaluate the agronomic performance of intercropping of lettuce cvs. Regina 71 (smooth leaf and Verônica (crisp leaf with carrot (cv. Brasília and radish (cv. Hybrid number 19, under organic management. The amount of nutrients exported from the system by harvesting was also evaluated. The experimental design used was of completely randomized blocks, with four replications. In the first experiment, treatments consisted of lettuce with crisp leaves intercropped with carrot, lettuce with crisp leaves intercropped with radish and sole crops. In the second experiment, lettuce with smooth leaves was used instead of lettuce with crisp leaves. Intercropping of carrot and lettuce, with crisp or smooth leaf, presented land equivalent ratios higher than 1.60. Intercropping of radish and lettuce, with crisp or smooth leaf, presented land equivalent ratios of 1.54 and 1.27, respectively. Besides, the amounts of nutrients extracted by harvested products were lower than the inputs, pointing out the viability of the tested intercroppings.

Ailena Sudo Salgado

2006-07-01

248

Teores de nutrientes na alface irrigada com água residuária aplicada por sistemas de irrigação Nutrients levels in lettuce irrigated with wastewater applied by irrigation systems  

Directory of Open Access Journals (Sweden)

Full Text Available Desenvolveu-se este trabalho para avaliar a composição química da parte aérea da alface, cv. Elisa, irrigada com água residuária tratada com leitos cultivados com macrófitas e água de um depósito de fonte hídrica superficial, cultivada em Latossolo Vermelho Distroférrico, utilizando-se dos sistemas de irrigação por aspersão convencional, gotejamento subterrâneo e superficial. O experimento compreendeu o período de 17-8 a 3-10-2001, e as análises químicas da alface foram realizadas aos 47 dias após o transplantio das mudas em campo. A parte aérea da alface foi analisada quanto ao teor de nitrogênio total, nitrato, fósforo, potássio, cálcio, magnésio, enxofre, ferro, manganês, cobre, zinco, sódio, boro, cobalto e molibdênio. O sódio e o enxofre apresentaram teores maiores que o máximo adequado na parte aérea da alface e o magnésio menor, enquanto para os demais elementos químicos foram normais e adequados, considerando os padrões para plantas bem nutridas, não sendo influenciados pelo tipo de água. O sódio foi o elemento químico que apresentou a maior elevação na parte aérea nos tratamentos irrigados com água residuária, apresentando diferença significativa em relação à água do depósito superficial nos três sistemas de irrigação. A utilização dos diferentes sistemas de irrigação para aplicação de água residuária tratada com leitos cultivados com macrófitas não interferiu no teor de nutrientes na parte aérea.A trial was carried out to evaluate the chemical composition in the aerial part of lettuce, cv. 'Elisa', irrigated with wastewater treated with constructed wetland and source deposit water, grown on a Rhodic Hapludox Soil, using the irrigation systems sprinkle, subsurface drip and surface drip irrigation. The experiment was carried out from August 17th to October 3rd of 2001 and the chemical analyses of the lettuce were accomplished to 47 days after transplanting of the seedling. The aerial part of the lettuce was analyzed as for the levels of total nitrogen, nitrate, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, sodium, boron, cobalt and molybdenum. The sodium and the sulfur presented higher levels than the maximum suitable in the aerial part of the lettuce and the smallest level of magnesium, while other chemical elements analyzed were normal and appropriate considering the standard for well-nourished plants, not being influenced by the water type. The sodium was the chemical element that presented the highest levels in the aerial part of the lettuce in the treatments irrigated with wastewater, presenting significant difference in relationship to the treatments irrigated with source deposit water in the three irrigation systems. The use of the different irrigation systems by the application of wastewater treated with constructed wetland did not interfere in the levels of nutrients in the aerial part of the lettuce.

Delvio Sandri

2006-04-01

249

Occurence of Cryptosporidium spp. in low quality water and on vegetables in Kumasi, Ghana  

DEFF Research Database (Denmark)

Protozoan parasites belonging to the genus Cryptosporidium are transmitted e.g. by food and water and may cause severe diarrhoea, dehydration, weight loss and malnutrition. Ingestion of 10 oocysts can lead to infection and pathogenic symptoms. Thus, to characterize Cryptosporidium spp. contamination level of river water, irrigation water and lettuce, 10L of water and 16 lettuce samples were collected four times in the period of, September â?? October 2013, with weekly intervals from six sample sites in and around Kumasi, Ghana. Oocysts were purified from water by sedimentation for 2 x 48 hours or pulsifying of lettuce followed by immunomagnetic separation and quantification by immunofluorescence microscopy, with sensitivities of 2 and 9%, respectively. After approximately six weeks of storage at 4C°, analysis and additional storage on slides, oocysts were washed off the slides and attempts to characterize Cryptosporidium spp. positive samples were done by PCR amplification and sequencing of the SSU rRNA, the HSP70 and the GP60 genes after. Cryptosporidium oocysts were found in 75% of the water samples and on 43% of the lettuce with concentrations of 53 â?? 3268 per 10 L water and 11 â?? 118 oocyst per 15 g of lettuce. Positive water samples on one or more occasions were demonstrated in all water and farm sites while all farms had positive lettuce samples on all occasions. Rainfall seemingly lowered the concentration of oocysts in water but not on lettuce. Molecular characterization of Cryptosporidium positive samples was unsuccessful, thus no conclusions can be drawn concerning sources of contamination. Nevertheless, the detection of high prevalence and concentration levels of Cryptosporidium oocysts on vegetables consumed raw and in water with direct contact to humans entails a potential risk of infection in humans. Implementation of preventive measures based on this study should be considered and actions taken accordingly.

Petersen, T. B.; Petersen, H. H.

2014-01-01

250

Occurrence of Cryptosporidiumspp. oocysts in low quality water and on vegetables in Kumasi, Ghana  

DEFF Research Database (Denmark)

Protozoan parasites belonging to the genus Cryptosporidium are transmitted e.g. by food and water and may cause severe diarrhoea, dehydration, weight loss and malnutrition. Ingestion of 10 oocysts can lead to infection and pathogenic symptoms. Thus, to characterize Cryptosporidium spp. contamination level of river water, irrigation water and lettuce, 10L of water and 16 lettuce samples were collected four times in the period of, September â?? October 2013, with weekly intervals from six sample sites in and around Kumasi, Ghana. Oocysts were purified from water by sedimentation for 2 x 48 hours or pulsifying of lettuce followed by immunomagnetic separation and quantification by immunofluorescence microscopy, with sensitivities of 2 and 9%, respectively. After approximately six weeks of storage at 4C°, analysis and additional storage on slides, oocysts were washed off the slides and attempts to characterize Cryptosporidium spp. positive samples were done by PCR amplification and sequencing of the SSU rRNA, the HSP70 and the GP60 genes after. Cryptosporidium oocysts were found in 75% of the water samples and on 43% of the lettuce with concentrations of 53 â?? 3268 per 10 L water and 11 â?? 118 oocyst per 15 g of lettuce. Positive water samples on one or more occasions were demonstrated in all water and farm sites while all farms had positive lettuce samples on all occasions. Rainfall seemingly lowered the concentration of oocysts in water but not on lettuce. Molecular characterization of Cryptosporidium positive samples was unsuccessful, thus no conclusions can be drawn concerning sources of contamination. Nevertheless, the detection of high prevalence and concentration levels of Cryptosporidium oocysts on vegetables consumed raw and in water with direct contact to humans entails a potential risk of infection in humans. Implementation of preventive measures based on this study should be considered and actions taken accordingly.

Petersen, T. B.; Petersen, H. H.

2014-01-01

251

The C terminus of lettuce mosaic potyvirus cylindrical inclusion helicase interacts with the viral VPg and with lettuce translation eukaryotic initiation factor 4E.  

Science.gov (United States)

Recessive resistance to lettuce mosaic virus (LMV) is conferred in lettuce by the mo1 gene, encoding the eukaryotic translation initiation factor 4E (eIF4E). The C terminus of the viral cylindrical inclusion helicase (CI-Cter), together with the VPg, is involved directly in overcoming mo1 resistance. In this study, recombinant LMV VPg and CI-Cter proteins from wild-type or resistance-breaking isolates were expressed and purified from Escherichia coli. The allelic forms of eIF4E from susceptible or resistant lettuce cultivars were produced similarly and these proteins were used in ELISA-based assays to demonstrate the in vitro binding of the various forms of LMV CI-Cter to both lettuce eIF4E and LMV VPg proteins. All combinations tested displayed significant and specific interactions, and the interaction between the C-terminal part of the LMV CI and eIF4E was confirmed in vivo in bimolecular fluorescence complementation assays. Higher interaction signals for both CI-eIF4E and CI-VPg were observed for LMV-E, indicating that the eIF4E interaction network involving CI and VPg appears to be stronger in the case of this resistance-breaking isolate. This could suggest the need for a minimal interaction threshold for infection success in resistant lettuce, but more precise measurement of the interaction parameters linking eIF4E, VPg and CI is needed in order to reinforce such a hypothesis. PMID:21918009

Tavert-Roudet, G; Abdul-Razzak, A; Doublet, B; Walter, J; Delaunay, T; German-Retana, S; Michon, T; Le Gall, O; Candresse, T

2012-01-01

252

Sensory quality attributes of lettuce obtained using different harvesting performance systems  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The objective of this study was to determine the best lettuce cultivar (American 'Graciosa', 'Vanda', 'Marcela' and 'Lavínia') harvesting method. Therefore, quality and shelf-life were evaluated using sensory analyses. Lettuce heads was harvested with the root on by the producer, so that they were c [...] ut in different ways in the laboratory. The samples were stored in a cold chamber at 10 °C and 80% ± 2% of relative humidity for nine days, and the sensorial analyses were performed according to Qualitative Descriptive Analysis method on days 1, 3, 6, and 9 of storage by twelve trained testers. The results were evaluated by variance analysis, principal component analysis, and the Tukey test with a reliability of 95%. The results indicate that there was a reduction in the quality of lettuce between the 1st and the 5th day of storage and that after the sixth day of storage the lettuce samples were considered unfit for consumption, except for the 'Lavínia' lettuce cultivar with root and cut treatment 2. On the ninth day of storage all samples were considered inappropriate for consumption.

Oliveira, Denize Cristine Rodrigues de; Leal, Paulo Ademar Martins; Honório, Sylvio Luís; Soares, Eveline Kássia Braga.

253

Sensory quality attributes of lettuce obtained using different harvesting performance systems  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to determine the best lettuce cultivar (American 'Graciosa', 'Vanda', 'Marcela' and 'Lavínia' harvesting method. Therefore, quality and shelf-life were evaluated using sensory analyses. Lettuce heads was harvested with the root on by the producer, so that they were cut in different ways in the laboratory. The samples were stored in a cold chamber at 10 °C and 80% ± 2% of relative humidity for nine days, and the sensorial analyses were performed according to Qualitative Descriptive Analysis method on days 1, 3, 6, and 9 of storage by twelve trained testers. The results were evaluated by variance analysis, principal component analysis, and the Tukey test with a reliability of 95%. The results indicate that there was a reduction in the quality of lettuce between the 1st and the 5th day of storage and that after the sixth day of storage the lettuce samples were considered unfit for consumption, except for the 'Lavínia' lettuce cultivar with root and cut treatment 2. On the ninth day of storage all samples were considered inappropriate for consumption.

Denize Cristine Rodrigues de Oliveira

2013-06-01

254

PHYTOCHEMICAL AND ANTIOXIDANT CHARACTERIZATION OF FIREWEED (CRASSOCEPHALUM CREPIDIOIDES AND AFRICAN LETTUCE (LACTUCA TARAXACIFOLIA  

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Full Text Available Two neglected and under utilized green leaf vegetables (Fireweed and African lettuce in South-West, Nigeria was evaluated for phytochemical contents and antioxidant properties. The stems and leaves of the vegetables were cut, air-dried and ground to fine powder. The phytochemicals and antioxidants analyses were carried out using standard methods and the results obtained were analyzed statistically by ANOVA and DMRT analysis. The flavonoids, total phenol, oxalate, tannin and ascorbic acid contents were relatively higher in African lettuce than fireweed while total carotenoids, alkaloids and phytate were relatively higher in fireweed than African lettuce. It was only in total phenol content of both vegetables that there was no significant difference (P<0.05. There were no significant difference (P<0.05 in reducing power, Fe2+ chelating activity, DPPH and ABST+ radical scavenging activities of both vegetables, although these antioxidant properties were relatively higher in African lettuce than in fireweed. The two vegetables are highly rich in phytochemical antioxidant contents (although African lettuce is relatively richer and this will enhance their usefulness as medicinal plants as well as antioxidant agents in lipids and lipid containing foods.

J.O. ARAWANDE

2012-11-01

255

Qualidade microbiológica e produtividade de alface sob adubação química e orgânica Microbiological quality and productivity of lettuce under chemical and organic fertilization  

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Full Text Available A contaminação de hortaliças por micro-oganismos patogênicos é uma realidade. Os adubos orgânicos têm sido responsabilizados por algumas contaminações de hortaliças observadas no Brasil. O objetivo deste trabalho foi avaliar a produtividade e a contaminação de alface por Salmonella sp. e coliformes a 45 °C, cultivada sob adubação orgânica. O delineamento experimental foi de blocos ao acaso, com seis tratamentos, em cinco repetições. Os tratamentos foram: T1 - Testemunha (sem adubação; T2 - Adubação química; T3 - Esterco de galinha; T4 - Esterco bovino; T5 - Húmus de minhoca; e T6 - Composto orgânico. As variáveis analisadas foram matéria fresca, matéria seca, macro e micronutrientes e contaminação microbiológica. Foi observada maior obtenção de matéria fresca nas parcelas adubadas com esterco de galinha (543 g, que diferiu estatisticamente da produção observada nos demais tratamentos. Não foi observada diferença estatística significativa entre tratamentos para matéria seca, com exceção da parcela com composto orgânico que apresentou o menor valor (3,7%. Não foi observada contaminação do solo e nem dos adubos orgânicos por esses micro-organismos. Porém, foi observada contaminação da água de irrigação e da alface por coliformes fecais. Existem fortes indícios de que a água de irrigação tenha sido o principal veículo de contaminação.Vegetable contamination with lethal microorganisms is a reality. Organic manure has been considered responsible for vegetable contamination in Brazil. The aim of this research was to evaluate the yield and lettuce contamination by Salmonella sp. and fecal coliforms, at 45 °C, grown under organic fertilization. The experimental design was in randomized blocks composed with 6 treatments in five replicates. The treatments were: T1 - Control (no fertilization; T2 - Chemical fertilization; T3 - Chicken manure; T4 - Cattle manure; T5 - Worm manure, and T6 - Organic compost. Fresh weight, dry matter percentage, macro and micronutrients, and microbiological contamination were recorded. The highest lettuce weight was observed in the parcels fertilized with chicken manure (543 g, which differed statistically from the weights observed in the other treatments. On the other hand, no statistical difference was observed in the dry matter percentage among the different treatments, with the exception of the value observed at the organic compost treatment, which was the lowest (3,7%. The soil and organic manure samples were not contaminated by Salmonella sp. and fecal coliforms. Nevertheless, irrigation water and lettuce samples were contaminated by fecal coliforms. There is strong evidence that irrigation water was the main source of lettuce contamination.

Ingergleice Machado de Oliveira Abreu

2010-05-01

256

Cooling and concentration of nutrient solution in hydroponic lettuce crop / Resfriamento e concentração da solução nutritiva em cultivo hidropônico da alface  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O trabalho foi realizado em ambiente protegido, no setor de Horticultura do Instituto Federal do Espírito Santo, Campus Itapina, Colatina, região Noroeste do Espírito Santo, com o objetivo de estudar e avaliar o efeito do resfriamento e da condutividade elétrica da solução nutritiva no crescimento d [...] a alface cv. Vitória de Santo Antão em cultivo hidropônico. O trabalho foi realizado em delineamento experimental inteiramente casualizado com dois fatores (controle de temperatura máxima da solução nutritiva: 26ºC e sem controle; e condutividade elétrica (EC) da solução: 1, 2 e 3 dS m-1 e quatro repetições. Cinquenta e dois dias após a semeadura foi realizada a colheita das plantas e avaliados a massas frescas e secas de folha, caule e raiz, volume de raízes, comprimento do caule e das raízes e porcentagem de água nas plantas. A temperatura da solução nutritiva influenciou o desempenho da alface em função do aumento da condutividade elétrica, demonstrando que o aumento da EC não compromete a produtividade quando há limitação na temperatura máxima da solução nutritiva, que nesse experimento foi de 26ºC. O resfriamento da solução proporcionou maior acúmulo de massa e porcentagem superior de água presente nas plantas, aumentando a produtividade da alface hidropônica em condições de clima tropical. Abstract in english The study was conducted in greenhouse at horticulture department of the Instituto Federal do Espírito Santo, Campus Itapina, Colatina, northwestern Espírito Santo state, Brazil, with the objective of evaluating the effect of cooling and electrical conductivity of nutrient solution on growth and deve [...] lopment of lettuce cv. Vitória de Santo Antão in hydroponics. The study was conducted in a completely randomized design with two factors (control of the maximum temperature of the nutrient solution: 26ºC and without control; and electrical conductivity, EC, of the solution: 1, 2 and 3 dS m-1) with three repetitions. The plants were harvested fifty-two days after sowing (DAS). We evaluated the dry and fresh mass of leaves, stems and roots, stem and root length, root volume and plant water content (%). The temperature of the nutrient solution influenced the behavior of lettuce influenced by the electrical conductivity, showing that the increase of the EC did not reduce the lettuce productivity when the maximum temperature of the nutrient solution is limited, which in this experiment was tested at 26ºC. The cooling of the nutrient solution provided greater accumulation of mass and a higher water percentage in plants, increasing the productivity of hydroponic lettuce in tropical climate.

Cometti, Nilton N; Bremenkamp, Diene M; Galon, Karla; Hell, Leonardo R; Zanotelli, Marinaldo F.

257

Nutrient absorption and response of lettuce to phosphorus fertilization  

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Full Text Available The objective of this study was to evaluate the response of lettuce (cultivar Verônica to different levels of phosphorus fertilization. The experiment was conducted from 25/09/2003 (sowing to 03/12/2003 (harvesting at the Fazenda Experimental São Manuel, UNESP/FCA, Botucatu/SP, under protective structures. The experiment was conducted in a randomized block design, with five treatments (0, 200, 400, 600 and 800kg.ha-1 of P2O5, in the form of triple superphosphate and five replications. Plants were grown in 13L plastic pots containing Latossolo Vermelho Distrófico Típico. A quadratic response was observed for the fresh mass of the plant shoots and leaf area, with maximum equivalent levels of 733 and 756kg.ha-1 of P2O5, respectively, as well as for potassium, calcium, magnesium, sulfur, boron, copper, iron, manganese and zinc accumulation. Linear increases were observed with the treatments of P2O5 for dry mass of the shoots, leaf number, plant height and nitrogen and phosphorus accumulation.

Antonio Ismael Inácio Cardoso

2012-09-01

258

Evaluation of total and thermotolerant coliforms on lettuce self service restaurants in Sinop-MT  

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Full Text Available Lettuce (Lactuca sativa L. is the leafy vegetable most consumed in the world and present high content of pro vitamin A in green leaves; it’s rich in calcium and iron and presents reasonable amounts of vitamins B1, B2, B6 and C. When eaten raw in salads they can to transmit pathogens if are inadequately cleaned. This study aimed to evaluate the microbiological quality of lettuce served in self-service restaurants in the city of Sinop – MT, concerning the total and thermotolerant coliforms. The laboratory analysis used was the Most Probable Number method (MPN. All samples were positive for total coliforms, reaching values above 1100 MPN/g, and when analyzed to confirm the presence of coliforms tolerant, all samples were negative. These results allowed observing that the values found for tolerant coliforms are within the standards established by legislation, but the total coliform count indicates poor hygiene lettuce served and consumed

P. C. Perondi

2013-11-01

259

A New Image Segmentation Algorithm and It’s Application in lettuce object segmentation  

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Full Text Available Lettuce image segmentation which based on computer image processing is the premise of non-destructive testing of lettuce quality. The traditional 2-D maximum entropy algorithm has some faults, such as low accuracy of segmentation, slow speed, and poor anti-noise ability. As a result, it leads to the problems of poor image segmentation and low efficiency. An improved 2-D maximum entropy algorithm is presented in this paper. It redistricts segmented regions and furtherly classifies the segmented image pixels with the method of the minimum fuzzy entropy, and reduces the impact of noise points, as a result the image segmentation accuracy is improved. The improved algorithm is used to lettuce object segmentation, and the experimental results show that the improved segmentation algorithm has many advantages compared with the traditional 2-D maximum entropy algorithm, such as less false interference, strong anti-noise ability, good robustness and validity.  

Hongyan Gao

2012-09-01

260

High content of resveratrol in lettuce transformed with a stilbene synthase gene of Parthenocissus henryana.  

Science.gov (United States)

Resveratrol (trans-3,5,4'-trihydroxystilbene) is a plant phytoalexin which has positive effects on human health. Stilbene synthase (STS) is a key enzyme involved in resveratrol biosynthesis. To construct a vector for STS expression in lettuce plant, a cDNA-encoding STS of Parthenocissus henryana was fused to the Cauliflower mosaic virus (CaMV) 35S promoter, and the bar gene was used as a selective marker gene. To increase the expression of STS, the expression cassette was flanked by MARs. In transgenic lettuce plants, an additional compound was identified as resveratrol by HPLC and ESI-MS. Quantitative analysis showed that the average content of resveratrol reached 56.40 +/- 5.52 microg/g leaf fresh weight, which was comparable to the amount in grape skin. Anticancer assay in HeLa cells revealed that apoptosis was induced by 200 microM of resveratrol extracted from transgenic lettuce. PMID:17032013

Liu, Shujun; Hu, Yuanlei; Wang, Xiaoli; Zhong, Jin; Lin, Zhongping

2006-10-18

 
 
 
 
261

Effects of nitrogen fertilizers on the growth and nitrate content of lettuce (Lactuca sativa L.).  

Science.gov (United States)

Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha?¹) is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha?¹) have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate. PMID:24758896

Liu, Cheng-Wei; Sung, Yu; Chen, Bo-Ching; Lai, Hung-Yu

2014-04-01

262

Effects of Nitrogen Fertilizers on the Growth and Nitrate Content of Lettuce (Lactuca sativa L.  

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Full Text Available Nitrogen is an essential element for plant growth and development; however, due to environmental pollution, high nitrate concentrations accumulate in the edible parts of these leafy vegetables, particularly if excessive nitrogen fertilizer has been applied. Consuming these crops can harm human health; thus, developing a suitable strategy for the agricultural application of nitrogen fertilizer is important. Organic, inorganic, and liquid fertilizers were utilized in this study to investigate their effect on nitrate concentrations and lettuce growth. The results of this pot experiment show that the total nitrogen concentration in soil and the nitrate concentration in lettuce increased as the amount of nitrogen fertilizer increased. If the recommended amount of inorganic fertilizer (200 kg·N·ha?1 is used as a standard of comparison, lettuce augmented with organic fertilizers (200 kg·N·ha?1 have significantly longer and wider leaves, higher shoot, and lower concentrations of nitrate.

Cheng-Wei Liu

2014-04-01

263

A New Image Segmentation Algorithm and It’s Application in lettuce object segmentation  

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Full Text Available Lettuce image segmentation which based on computer image processing is the premise of non-destructive testing of lettuce quality. The traditional 2-D maximum entropy algorithm has some faults, such as low accuracy of segmentation, slow speed, and poor anti-noise ability. As a result, it leads to the problems of poor image segmentation and low efficiency. An improved 2-D maximum entropy algorithm is presented in this paper. It redistricts segmented regions and furtherly classifies the segmented image pixels with the method of the minimum fuzzy entropy, and reduces the impact of noise points, as a result the image segmentation accuracy is improved. The improved algorithm is used to lettuce object segmentation, and the experimental results show that the improved segmentation algorithm has many advantages compared with the traditional 2-D maximum entropy algorithm, such as less false interference, strong anti-noise ability, good robustness and validity.  

Xiaodong Zhang

2012-07-01

264

Multiple outbreaks of Salmonella braenderup associated with consumption of iceberg lettuce.  

Science.gov (United States)

The aim of this study was to describe the findings from an outbreak investigation following several apparently unrelated community outbreaks of gastroenteritis. Epidemiological, environmental, laboratory and traceback investigations were used to identify the source of the outbreak. We enrolled 23 (of 29) laboratory confirmed cases and 24 neighbourhood case-nominated controls in a case-control study which revealed that illness was associated with consumption of iceberg lettuce (matched odds ratio 8.0 (95% CI 1.1-355) contaminated with Salmonella braenderup. Several eating establishments were affected and the lettuce was traced back to a single producer in Spain. This is the first UK report implicating S. braenderup in an outbreak due to lettuce. The results highlight the need to increase attention to the various stages in the farm-to-fork process to reduce produce-associated outbreaks related to the global food trade. PMID:21916661

Gajraj, Roger; Pooransingh, Shalini; Hawker, Jeremy I; Olowokure, Babatunde

2012-01-01

265

Invasive plant-derived biochar inhibits sulfamethazine uptake by lettuce in soil.  

Science.gov (United States)

Veterinary antibiotics are frequently detected in soils posing potential contamination of food crops. Sulfamethazine (SMT) uptake was investigated by lettuce (Lactuca sativa L.) grown in the soils treated with/without biochar derived from an invasive plant, burcucumber (Sicyos angulatus L.) (BBC700). Soils were contaminated with SMT at 5 and 50mgkg(-1), and treated with/without 5% BBC700 (ww(-1)). The lettuces were harvested after 5weeks of cultivation and were analyzed for SMT by a high performance liquid chromatography-tandem mass spectrometry after solid-phase extraction. With 5% BBC700, the uptake of SMT was reduced by 86% in the soil spiked with 5mgkg(-1) SMT compared to the control whereas a 63% reduction was observed in the soil spiked with 50mgkg(-1) SMT. Application of BBC700, into soils effectively reduced the SMT uptake by lettuce. PMID:24997958

Rajapaksha, Anushka Upamali; Vithanage, Meththika; Lim, Jung Eun; Ahmed, Mohamed Bedair M; Zhang, Ming; Lee, Sang Soo; Ok, Yong Sik

2014-09-01

266

Impacts of major cations (K(+), Na (+), Ca (2+), Mg (2+)) and protons on toxicity predictions of nickel and cadmium to lettuce (Lactuca sativa L.) using exposure models.  

Science.gov (United States)

Biotic ligand models (BLM) explicitly accounting for hypothetical interactions with biotic ligands and bioavailability as dictated by water chemistry have been developed for various metals and different organisms. It is only recently that BLMs for plants have received increasing attention. Lettuce is one of the most important vegetable crops in the world. This study investigated the impacts of Ca(2+), Mg(2+), K(+), Na(+) and pH, on acute toxicity of Ni and Cd to butter-head lettuce seedlings (Lactuca sativa L.). 4-day assays with the root elongation inhibition (REI) as the endpoint were performed in hydroponic solutions. Magnesium was found to be the sole cation significantly enhancing the median inhibition concentration (IC50) of Ni(2+) with increasing concentration. By incorporating the competitive effects of Mg(2+), the Ni-toxicity prediction was improved significantly as compared to the total metal model (TMM) and the free ion activity model (FIAM). The conditional stability constants derived from the Ni-BLM were log K MgBL = 2.86, log K NiBL = 5.1, and f NiBL (50%)  = 0.57. A slight downtrend was observed in the 4-d IC50 of Cd(2+) at increasing H(+) concentrations, but this tendency was not consistent and statistically significant (p = 0.07) over the whole range. The overall variations of Cd-toxicity within the tested Na(+), K(+), Ca(2+) and Mg(2+) concentration ranges were relatively small and not statistically significant. 80 % of lettuce REI by Cd could be explained using both TMM and FIAM instead of BLM in the present study. Thus, the mechanistically underpinned models for soil quality guidelines should be developed on a metal-specific basis across different exposure conditions. PMID:24510448

Liu, Yang; Vijver, Martina G; Peijnenburg, Willie J G M

2014-04-01

267

Utility of bioassays (lettuce, red clover, red fescue, Microtox, MetSTICK, Hyalella, bait lamina) in ecological risk screening of acid metal (Zn) contaminated soil.  

Science.gov (United States)

The objective of this study was to assess selected bioassays and ecological screening tools for their suitability in a weight of evidence risk screening process of acidic metal contaminated soil. Intact soil cores were used for the tests, which minimizes changes in pH and metal bioavailability that may result from homogenization and drying of the soil. Soil cores were spiked with ZnCl(2) or CaCl(2). Leachate collected from the soil cores was used to account for the exposure pathways through pore water and groundwater. Tests assessed included MetSTICK in soil cores and Microtox in soil leachate, lettuce (Lactuca sativa), red fescue (Festuca rubra) and red clover (Trifolium pratense) in the soil cores and lettuce and red clover in soil leachate, Hyallella azteca in soil leachate, and an ecological soil function test using Bait Lamina in soil cores. Microtox, H. azteca, lettuce and red fescue showed higher sensitivity to low pH than to Zn concentrations and are therefore not recommended as tests on intact acidic soil cores and soil leachate. The Bait Lamina test appeared sensitive to pH levels below 3.7 but should be investigated further as a screening tool in less acidic soils. Among the bioassays, the MetSTICK and the T. pratense bioassays in soil cores were the most sensitive to Zn, with the lowest nominal NOEC of 200 and 400mg Zn/kg d.w., respectively. These bioassays were also tolerant of low pH, which make them suitable for assessing hazards of metal contaminated acid soils. PMID:22444727

Chapman, E Emily V; Hedrei Helmer, Stephanie; Dave, Göran; Murimboh, John D

2012-06-01

268

Lack of internalization of Escherichia coli O157:H7 in lettuce (Lactuca sativa L.) after leaf surface and soil inoculation.  

Science.gov (United States)

Survival and internalization characteristics of Escherichia coli O157:H7 in iceberg, romaine, and leaf lettuce after inoculation of leaf surfaces and soil were determined. A five-strain mixture of E. coli O157:H7 in water and cow manure extract was used as an inoculum for abaxial and adaxial sides of leaves at populations of 6 to 7 log and 4 log CFU per plant. The five strains were individually inoculated into soil at populations of 3 and 6 log CFU/g. Soil, leaves, and roots were analyzed for the presence and population of E. coli O157:H7. Ten (4.7%) of 212 samples of leaves inoculated on the adaxial side were positive for E. coli O157:H7, whereas 38 (17.9%) of 212 samples inoculated on the abaxial side were positive. E. coli O157:H7 survived for at least 25 days on leaf surfaces, with survival greater on the abaxial side of the leaves than on the adaxial side. All 212 rhizosphere samples and 424 surface-sanitized leaf and root samples from plants with inoculated leaves were negative for E. coli O157:H7, regardless of plant age at the time of inoculation or the location on the leaf receiving the inoculum. The pathogen survived in soil for at least 60 days. Five hundred ninety-eight (99.7%) of 600 surface-sanitized leaf and root samples from plants grown in inoculated soil were negative for E. coli O157:H7. Internalization of E. coli O157:H7 in lettuce leaves and roots did not occur, regardless of the type of lettuce, age of plants, or strain of E. coli O157:H7. PMID:19833024

Zhang, Guodong; Ma, Li; Beuchat, Larry R; Erickson, Marilyn C; Phelan, Vanessa H; Doyle, Michael P

2009-10-01

269

Effect of foliar calcium chloride treatment on the level of chlorogenic acid, ?-carotene, lutein and tocopherols in lettuce (Lactuca sativa L.  

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Full Text Available The aim of the presented study was to determine the effect of foliar application of CaCl2 on the level of ?-carotene, lutein, tocopherols and phenolic compounds in the leaves of lettuce cv. Omega (Lactuca sativa L.. The experiments were conducted in the greenhouse of the Faculty of Cultivation and Fertilisation of Horticultural Plants, University of Life Sciences in Lublin. During the growing period, 7 and 14 days before harvest, the plants were treated with a solution of CaCl2 with concentrations of 0.1 M and 0.2 M. Plants sprayed with water were the control treatment in the experiment. Analyses were performed on whole leaves and the blade without midrib. The obtained results indicate that the leaves of lettuce cv. Omega are a good source of phenolic compounds, carotenoids and tocopherols. The dominant carotenoid in lettuce cv. Omega was ?-carotene. Foliar application of CaCl2 on the plants did not have any significant effect on the level of ?-carotene and lutein in the whole leaves. The contents of tocopherols, total phenolic compounds and chlorogenic acid were dependent on the concentration of CaCl2. The application of 0.1 M CaCl2 solution in the plants resulted in a decrease in the level of total phenolic compounds and chlorogenic acid, and an increase in tocopherol content. However, the treatment of the plants with 0.2M CaCl2 solution caused a lowering of the concentration of tocopherols and an increase in the content of chlorogenic acid and total phenolic compounds.

Irena Perucka

2011-03-01

270

Adubação de alface com lodo de esgoto de cervejaria Lettuce manuring with sewage sludge of brewery  

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Full Text Available O lodo de esgoto pode ser uma alternativa viável na adubação orgânica da alface, em solos arenosos. Avaliou-se a produtividade e a qualidade dessa cultura por meio de um experimento de campo, comparando a aplicação de lodo de esgoto da cervejaria Equatorial, com a de esterco de galinha. Os tratamentos consistiram de adubações com lodo de esgoto, lodo de esgoto + NPK, esterco de galinha, esterco de galinha + NPK, NPK e controle. A produção e a qualidade comercial da alface cultivada com lodo de esgoto de cervejaria não diferiram em comparação ao tratamento com esterco de galinha. Não houve diferença no teor de macronutrientes nas folhas dessa cultura, com a utilização do esterco ou lodo de esgoto de cervejaria. Os teores de micronutrientes e metais pesados nas folhas da alface dos tratamentos não diferiram daqueles observados no controle. Desses resultados depreende-se que o lodo de esgoto de cervejaria pode substituir o esterco de galinha em adubações da cultura de alface, sem prejuízos na produtividade, qualidade e sem afetar os teores de metais pesados nas folhas.Sewage sludge can be a viable alternative as organic manure for lettuce culture in sandy soils. A field experiment was carried out to evaluate the yield and quality of lettuce fertilized with sewage sludge in comparison with poultry manure. The treatments were sewage sludge, sewage sludge + NPK, poultry manure, poultry manure + NPK and control (without fertilizer. The yield and commercial quality of lettuce fertilized with sewage sludge did not differ from the treatments with poultry manure. Macronutrients content in lettuce leaves did not differ from sewage sludge or poultry manure. The micronutrients and heavy metal contents in lettuce leaves did not differ between organic manure and control. The sewage sludge derived from brewery can substitute the poultry manure in organic fertilization of the lettuce, without reducing the yield and quality of this culture and did not affect heavy metal content in the leaves.

Altamiro S.L. Ferraz Junior

2003-03-01

271

Binding of virus-like particles of Norwalk virus to romaine lettuce veins.  

Science.gov (United States)

Noroviruses (NoV) annually cause millions of cases of gastrointestinal disease in the United States. NoV are associated with raw shellfish outbreaks, particularly oysters, which are thought to bioaccumulate NoV particles during the filter-feeding process. NoV outbreaks, however, have also been known to occur from other common-source food-borne vehicles, such as lettuce, frozen raspberries, and salad. In this study, we evaluated romaine lettuce as a potential vehicle for NoV transmission by testing the binding and distribution of NoV to the surface of romaine. Recombinant Norwalk virus-like particles (rNVLP) applied to the surface of romaine lettuce localized as large clusters primarily on the leaf veins. An extract of romaine lettuce leaves in phosphate-buffered saline (PBS) (romaine extract [RE]) bound rNVLP in a dose-dependent manner. RE did not bind rNVLP by histo-blood group antigens (HBGA), nor was RE competitive with rNVLP binding to porcine gastric mucin. These results suggested that non-HBGA molecules in RE bind rNVLP by a binding site(s) that is different from the defined binding pocket on the virion. Extracts of cilantro, iceberg lettuce, spinach, and celery also bound rNVLP. Samples of each of the vegetables spiked with rNVLP and tested with anti-NVLP antibody revealed by confocal microscopy the presence of rNVLP not only on the veins of cilantro but also throughout the surface of iceberg lettuce. PMID:21037300

Gandhi, Kamal M; Mandrell, Robert E; Tian, Peng

2010-12-01

272

Differences in attachment of Salmonella enterica serovars to cabbage and lettuce leaves.  

Science.gov (United States)

This study investigated the ability of five Salmonella enterica serovars to attach to and colonize intact and cut lettuce (Iceberg, Romaine) and cabbage surfaces. Biofilm formation and attachment of Salmonella serovars to intact and cut leaves were determined. Populations of loosely and strongly attached Salmonella were obtained to calculate the attachment strength (S(R)). Biofilm formation, as determined by microtiter plate assay, varied with strain and growth medium used. Salmonella Tennessee and S. Thompson produced stronger biofilms compared to S. Newport, S. Negev, and S. Braenderup. Biofilm formation was also stronger when Salmonella spp. were grown in diluted TSB (1:10). S. Tennessee, which produced strong biofilms, attached to produce surfaces at significantly higher numbers than the populations of S. Negev. Overall, S. Tennessee displayed more biofilm formation in vitro and attached more strongly to lettuce than other serovars. All Salmonella serovars attached rapidly on intact and cut produce surfaces. Salmonella spp. attached to Romaine lettuce at significantly higher numbers than those attached to Iceberg lettuce or cabbage. Salmonella attached preferentially to cut surface of all produce; however, the difference between Salmonella populations attached to intact and cut surfaces was similar (P>0.05). Salmonella attachment to both intact and cut produce surfaces increased with time. The overall attachment strength of Salmonella was significantly lower on cabbage (0.12) followed by Iceberg (0.23) and Romaine lettuce (0.34). Cabbage, intact or cut, did not support attachment of Salmonella as well as Romaine lettuce. Understanding the attachment mechanisms of Salmonella to produce may be useful in developing new intervention strategies to prevent produce outbreaks. PMID:20226552

Patel, Jitendra; Sharma, Manan

2010-04-30

273

Ocorrência generalizada do Lettuce mottle virus em três regiões produtoras de alface comercial do Estado de São Paulo Occurrence of Lettuce mottle virus on three lettuce producing areas from São Paulo State  

Directory of Open Access Journals (Sweden)

Full Text Available Os sequivírus são vírus isométricos transmitidos por afídeos. Lettuce mottle virus (LeMoV, um provável sequivirus foi descrito no Brasil em 1982 e causa sintomas de mosaico semelhantes aos observados pelo Lettuce mosaic virus (LMV. Um levantamento para ocorrência do LeMoV nos campos de produção de alface de três diferentes regiões do Estado de São Paulo (Mogi das Cruzes, Campinas e Bauru foi realizado durante 2002 a 2005. RNA total foi extraído e utilizado na detecção, em RT-PCR, com oligonucleotídeos específicos para o LeMoV. Do total de 1362 amostras, 137 (10,05% foram positivas para o LeMoV. Infecção mista com o LMV foi verificada em 43 amostras (31,4%. Foi verificada a ocorrência do LeMoV nas três diferentes regiões analisadas, porém sua ocorrência foi baixa nas diferentes épocas do ano.Sequiviruses are isometric aphid-borne plant viruses. Lettuce mottle virus (LeMoV, a putative sequivirus was first described in Brazil on 1982 causing similar mosaic symptoms as Lettuce mosaic virus (LMV. A survey for the occurrence of LeMoV on open field conditions was carried out during 2002 to 2005 on Mogi das Cruzes, Campinas and Bauru in São Paulo state. Total RNA was extracted and used on RT-PCR with specific LeMoV primers. On 1362 samples tested, 137 (10,05% were positive for LeMoV. Mixed infections with LMV was observed on 43 samples (31,4%. The presence of LeMoV was observed in the three different regions, but with low incidence during the year.

Renate Krause-Sakate

2008-02-01

274

Ocorrência generalizada do Lettuce mottle virus em três regiões produtoras de alface comercial do Estado de São Paulo / Occurrence of Lettuce mottle virus on three lettuce producing areas from São Paulo State  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Os sequivírus são vírus isométricos transmitidos por afídeos. Lettuce mottle virus (LeMoV), um provável sequivirus foi descrito no Brasil em 1982 e causa sintomas de mosaico semelhantes aos observados pelo Lettuce mosaic virus (LMV). Um levantamento para ocorrência do LeMoV nos campos de produção de [...] alface de três diferentes regiões do Estado de São Paulo (Mogi das Cruzes, Campinas e Bauru) foi realizado durante 2002 a 2005. RNA total foi extraído e utilizado na detecção, em RT-PCR, com oligonucleotídeos específicos para o LeMoV. Do total de 1362 amostras, 137 (10,05%) foram positivas para o LeMoV. Infecção mista com o LMV foi verificada em 43 amostras (31,4%). Foi verificada a ocorrência do LeMoV nas três diferentes regiões analisadas, porém sua ocorrência foi baixa nas diferentes épocas do ano. Abstract in english Sequiviruses are isometric aphid-borne plant viruses. Lettuce mottle virus (LeMoV), a putative sequivirus was first described in Brazil on 1982 causing similar mosaic symptoms as Lettuce mosaic virus (LMV). A survey for the occurrence of LeMoV on open field conditions was carried out during 2002 to [...] 2005 on Mogi das Cruzes, Campinas and Bauru in São Paulo state. Total RNA was extracted and used on RT-PCR with specific LeMoV primers. On 1362 samples tested, 137 (10,05%) were positive for LeMoV. Mixed infections with LMV was observed on 43 samples (31,4%). The presence of LeMoV was observed in the three different regions, but with low incidence during the year.

Renate, Krause-Sakate; Ana Carolina, Firmino; Adriana Salomão, Jadão; Marcelo A., Pavan; Norberto da, Silva; Sérgio Minoru, Hanai; Roberto Hiroto, Anbo; Thomas, Nietzsche.

275

Production of iceberg lettuce using mulches Produção de alface tipo americana sob coberturas de solo  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mulches bring several benefits to lettuce cultivation. This work evaluated the effect of mulches on the cultivation of iceberg lettuce, cv. Lucy Brown. The treatment plots were: 1- no mulch and no weed control (control); 2- no mulch and weed control every 15 days; 3- sugarcane bagasse mulch of 2 cm thickness; 4- black plastic mulch; 5- double-faced plastic mulch (silver/black). Data were collected in regard to plant cycle when in the field, amount of chlorophyll in the leaves, productivity (i...

2001-01-01

276

Nitrogen fertilization on intercropping of lettuce and rocket Adubação nitrogenada em consórcio de alface e rúcula  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The work was carried out at UNESP, Jaboticabal, São Paulo State, Brazil, from September to December 2006, to evaluate the effect of nitrogen fertilization on intercropping of lettuce and rocket. The experiment was conducted in a randomized complete block design, with four replications, treatments being arranged in a 4 x 4 + 2 factorial design. The treatments were the result of a combination of four N rates for lettuce (0, 65, 130 and 195 kg ha-1) and four N rates for rocket (0, 65, 130 and 1...

Barros Ju?nior, Aure?lio P.; Ceci?lio Filho, Arthur B.; Rezende, Bra?ulio Luciano A.; Rq, Diego Po?rto; Prado, Renato M.

2011-01-01

277

A detailed linkage map of lettuce based on SSAP, AFLP and NBS markers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Molecular markers based upon a novel lettuce LTR retrotransposon and the nucleotide binding site-leucine-rich repeat (NBS-LRR) family of disease resistance-associated genes have been combined with AFLP markers to generate a 458 locus genetic linkage map for lettuce. A total of 187 retrotransposon-specific SSAP markers, 29 NBS-LRR markers and 242 AFLP markers were mapped in an F2 population, derived from an interspecific cross between a Lactuca sativa cultivar commonly used in Europe and a wil...

Syed, N.; Sorensen, A. P.; Antonise, R.; Wiel, C. C. M.; Linden, C. G.; Westende, W. P. C.; Hooftman, D. A. P.; Nijs, H. C. M.; Flavell, A.

2006-01-01

278

The hrp genes of Pseudomonas cichorii are essential for pathogenicity on eggplant but not on lettuce  

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Pseudomonas cichorii causes necrotic lesions in eggplant and rot in lettuce. Through transposon insertion into P. cichorii strain SPC9018 we produced two mutants, 4-57 and 2-99, that lost virulence on eggplant but not lettuce. Analyses showed that a transposon was inserted into the hrpG gene in 4-57 and the hrcT gene in 2-99. Nucleotide sequences of the hrp genes of SPC9018 are homologous to those of Pseudomonas viridiflava BS group strains. The pathogenicity of 4-57 on eggplant was restored ...

Hojo, Hiroshi; Koyanagi, Makoto; Tanaka, Masayuki; Kajihara, Shigeru; Ohnishi, Kouhei; Kiba, Akinori; Hikichi, Yasufumi

2008-01-01

279

Influence of nickel nutrition and nitrogen source on growth and yield of lettuce in hydroponic culture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nickel (Ni) is the most recently discovered essential element for higher plants. But there is limited information about the effect of this element on yield and nitrogen (N) metabolism of different plants. In this research, the interaction of Ni supplement and N source was studied on nitrate accumulation and growth of lettuce (Lactuca sativa L. cv. Baker) in solution culture. In a greenhouse experiment, lettuce plants were exposed to two Ni levels (0 and 0.04 µM in the form of NiCl2) and thre...

2012-01-01

280

Binding of Virus-Like Particles of Norwalk Virus to Romaine Lettuce Veins?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Noroviruses (NoV) annually cause millions of cases of gastrointestinal disease in the United States. NoV are associated with raw shellfish outbreaks, particularly oysters, which are thought to bioaccumulate NoV particles during the filter-feeding process. NoV outbreaks, however, have also been known to occur from other common-source food-borne vehicles, such as lettuce, frozen raspberries, and salad. In this study, we evaluated romaine lettuce as a potential vehicle for NoV transmission by te...

2010-01-01

 
 
 
 
281

Índices morfofisiológicos e de produção de alface sob estresse salino / Morphophysiological indices and production of lettuce under saline stress  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese No Nordeste brasileiro, a alface é uma importante olerícola cultivada sob condições de irrigação em que são utilizadas águas de qualidade variada; uma das características da região é a variação espacial e temporal da qualidade dos recursos hídricos. Mesmo assim, são escassos os trabalhos referentes [...] aos efeitos da salinidade na formação de mudas e seu reflexo sobre a produção. Neste trabalho estudaram-se os efeitos de cinco níveis de condutividade elétrica da água de irrigação (CEa: 0,3, 1,0, 1,7, 2,4 e 3,1 dS m-1), em relação aos índices morfofisiológicos da alface 'Elba', a partir de mudas produzidas com águas de 0,3 e 3,1 dS m-1. Não houve efeito interativo entre os fatores estudados. O índice raiz/parte-aérea e a taxa de crescimento absoluto, foram afetados pela CEa, mas sem efeito sobre a taxa de crescimento relativo. O crescimento das plantas, cujas mudas foram produzidas com CEa de 3,1 dS m-1, foi inferior no início do ciclo, recuperando-se paulatinamente durante o crescimento; no momento da colheita, as taxas de crescimento absoluto e relativo foram, respectivamente, iguais e superiores às das plantas produzidas com água de baixa salinidade. A evapotranspiração diminuiu com o aumento da salinidade. As relações Na+/(Ca2++Mg2+) e Na+/K+ em folhas foram incrementadas linearmente com a salinidade, mas as plantas conseguiram manter o balanço iônico favorável. O rendimento da alface diminuiu 6,1 e 9,0% por aumento unitário de condutividade elétrica do extrato de saturação do solo e da água de irrigação, acima de 0,3 e 1,73 dS m-1, respectivamente. Abstract in english Lettuce is an important vegetable crop in the Northeast of Brazil cultivated under irrigated conditions using water of variable quality; one of the characteristics of this region is spatial and temporal variation in quality of water resources. In spite of this, research related to effects of salinit [...] y on the seedling formation and its posterior reflex on production is limited. In the present study, the effects of salinity of irrigation water (ECw: 0.3, 1.0, 1.7, 2.4 and 3.1 dS m-1) on growth response of lettuce 'Elba' using two types of seedlings produced with ECw of 0.3 and 3.1 dS m-1 were evaluated in a greenhouse. The studied factors had no interactive effect. Root/shoot ratio and absolute growth rate were affected by salinity although relative growth rate was not affected directly. The seedlings produced with ECw of 3.1 dS m-1 had lower growth rates at the beginning but recovered gradually during the growth cycle. In the last evaluation, the absolute and relative growth rates of these plants were, respectively, equal and superior to that of plants produced with water of low salinity. Increasing water salinity decreased evapotranspiration. The Na+/(Ca2++Mg2+) and Na+/K+ ratios in leaf increased linearly with the salinity but plants maintained favorable ionic balance. The decrease in lettuce yield was 6.1 and 9.0% per unit increase in electrical conductivity of the saturation extract of soil and of irrigation water above 0.3 and 1.73 dS m-1, respectively.

Sergio B. A., Viana; Pedro D., Fernandes; Hans R., Gheyi; Frederico A. L., Soares; Paulo T., Carneiro.

282

Índices morfofisiológicos e de produção de alface sob estresse salino Morphophysiological indices and production of lettuce under saline stress  

Directory of Open Access Journals (Sweden)

Full Text Available No Nordeste brasileiro, a alface é uma importante olerícola cultivada sob condições de irrigação em que são utilizadas águas de qualidade variada; uma das características da região é a variação espacial e temporal da qualidade dos recursos hídricos. Mesmo assim, são escassos os trabalhos referentes aos efeitos da salinidade na formação de mudas e seu reflexo sobre a produção. Neste trabalho estudaram-se os efeitos de cinco níveis de condutividade elétrica da água de irrigação (CEa: 0,3, 1,0, 1,7, 2,4 e 3,1 dS m-1, em relação aos índices morfofisiológicos da alface 'Elba', a partir de mudas produzidas com águas de 0,3 e 3,1 dS m-1. Não houve efeito interativo entre os fatores estudados. O índice raiz/parte-aérea e a taxa de crescimento absoluto, foram afetados pela CEa, mas sem efeito sobre a taxa de crescimento relativo. O crescimento das plantas, cujas mudas foram produzidas com CEa de 3,1 dS m-1, foi inferior no início do ciclo, recuperando-se paulatinamente durante o crescimento; no momento da colheita, as taxas de crescimento absoluto e relativo foram, respectivamente, iguais e superiores às das plantas produzidas com água de baixa salinidade. A evapotranspiração diminuiu com o aumento da salinidade. As relações Na+/(Ca2++Mg2+ e Na+/K+ em folhas foram incrementadas linearmente com a salinidade, mas as plantas conseguiram manter o balanço iônico favorável. O rendimento da alface diminuiu 6,1 e 9,0% por aumento unitário de condutividade elétrica do extrato de saturação do solo e da água de irrigação, acima de 0,3 e 1,73 dS m-1, respectivamente.Lettuce is an important vegetable crop in the Northeast of Brazil cultivated under irrigated conditions using water of variable quality; one of the characteristics of this region is spatial and temporal variation in quality of water resources. In spite of this, research related to effects of salinity on the seedling formation and its posterior reflex on production is limited. In the present study, the effects of salinity of irrigation water (ECw: 0.3, 1.0, 1.7, 2.4 and 3.1 dS m-1 on growth response of lettuce 'Elba' using two types of seedlings produced with ECw of 0.3 and 3.1 dS m-1 were evaluated in a greenhouse. The studied factors had no interactive effect. Root/shoot ratio and absolute growth rate were affected by salinity although relative growth rate was not affected directly. The seedlings produced with ECw of 3.1 dS m-1 had lower growth rates at the beginning but recovered gradually during the growth cycle. In the last evaluation, the absolute and relative growth rates of these plants were, respectively, equal and superior to that of plants produced with water of low salinity. Increasing water salinity decreased evapotranspiration. The Na+/(Ca2++Mg2+ and Na+/K+ ratios in leaf increased linearly with the salinity but plants maintained favorable ionic balance. The decrease in lettuce yield was 6.1 and 9.0% per unit increase in electrical conductivity of the saturation extract of soil and of irrigation water above 0.3 and 1.73 dS m-1, respectively.

Sergio B. A. Viana

2004-04-01

283

Avaliação patogênica in vitro de Pythium middletonii Sparrow e Pythium dissotocum Drechsler em alface / In vitro pathogenic evaluation of Pythium middletonii Sparrow and Pythium dissotocum Drechsler in lettuce  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Infecções radiculares nos cultivos hidropônicos de alface são frequentes e, na maior parte das vezes, causadas por espécies de Pythium, extremamente bem adaptadas ao ambiente aquático. Este estudo buscou avaliar o potencial patogênico in vitro de Pythium middletonii e P. dissotocum, em quatro cultiv [...] ares de alface: Elisa (lisa), Vera (crespa), Mimosa (mimosa) e Tainá (americana). Sementes de alface, de cada cultivar, foram desinfetadas superficialmente, pré-germinadas por 24 horas, e colocadas na superfície do meio ágar-água. Em seguida, um disco de micélio dos isolados de Pythium, foi disposto no centro de cada placa. Placas contendo apenas as sementes de alface serviram como controle. O delineamento experimental utilizado foi inteiramente casualizado, com cinco repetições, sendo cada uma delas representada por uma placa de Petri. Avaliou-se o comprimento dos hipocótilos, das radículas e a porcentagem das plântulas sobreviventes após dez dias de incubação. O experimento foi conduzido na temperatura ideal de crescimento da alface (20ºC), e nas ideais para o crescimento dos isolados, 23ºC para P. middletonii e 27ºC para P. dissotocum. A 20ºC, P. dissotocum foi mais patogênico que P. middletonii, reduzindo significativamente o comprimento dos hipocótilos e, principalmente, das radículas, de praticamente todas as cultivares. Na temperatura de 27ºC, P. dissotocum foi responsável pela mais baixa porcentagem de plântulas sobreviventes entre as cultivares, sendo mais patogênico em Vera (54% de sobrevivência). Dentre as cultivares analisadas, a Mimosa mostrou tendência de menor suscetibilidade a este patógeno, apresentando a maior porcentagem de plântulas sobreviventes e o maior comprimento das radículas em relação ao controle. P. dissotocum apresentou maior crescimento micelial e foi mais patogênico que P. middletonii em todos os experimentos realizados. Abstract in english Root infections in hydroponic lettuce are frequent and mostly caused by Pythium species, which are extremely well adapted to aquatic environments. The present study aimed to evaluate in vitro the pathogenic potential of Pythium middletonii and Pythium dissotocum in four cultivars of lettuce, Elisa ( [...] smooth), Vera (curly), Mimosa (mimosa) and Tainá (American). Lettuce seeds from each cultivar were superficially disinfected, pre-germinated for 24 hours and placed on the water agar medium surface. Then, a dish containing mycelium from Pythium isolates was placed in the center of each plate. Control consisted of plates containing lettuce seeds only. Experimental design was completely randomized, with five replicates, each one represented by a Petri dish. Hypocotyl and radical length besides surviving seedlings percentage after ten days of incubation were evaluated. The experiment was carried out, at different temperatures, and the pathogenicity of the isolates was investigated at the ideal temperature for the lettuce (20ºC), and at the ideal temperatures for the growth of the isolates, 23ºC for P. middletonii and 27ºC for P. dissotocum. At 20ºC, P. dissotocum had higher pathogenicity on lettuce cultivars than P. middletonii, significantly decreasing the length of hypocotyls, especially radicles, of most cultivars. For P. dissotocum, 27ºC was the most suitable temperature for the specimen growth; however, it led to the lowest percentage of surviving seedlings among all cultivars, with the lowest percentage (54%) detected for Vera. Among the cultivars, Mimosa presented higher percentage of survivor seedlings and higher length of radicles in relation to the control, and thus was considered less susceptible to the pathogen. P. dissotocum presented higher mycelium growth and was more pathogenic than P. middletonii in all experiments.

F.R., Baptista; C.L.A, Pires-Zottarelli; L.D., Teixeira; N.A., Santos Júnior.

284

Evaluation of treatments for elimination of foodborne pathogens on the surface of leaves and roots of lettuce (Lactuca sativa L.).  

Science.gov (United States)

Several outbreaks of Salmonella and Escherichia coli O157:H7 infections have been associated with consumption of leafy greens. Questions remain concerning the ability of these pathogens to become internalized within lettuce and spinach tissues. An effective validated surface disinfection method for lettuce is needed before factors affecting internalization of pathogens can be studied. The objective of this study was to develop a surface disinfection method for lettuce leaves and roots. Iceberg lettuce (Lactuca sativa L.) leaves cut into pieces (3 by 3 cm) and lettuce roots were inoculated by immersing in suspensions of five-strain mixtures of green fluorescent protein-labeled E. coli O157:H7, Salmonella, or Listeria monocytogenes at populations of 7 to 8 log CFU/ml for 10 min at 20 +/- 1 degrees C. Inoculated samples were placed in a laminar flow biosafety cabinet for 30 min before treating with disinfectants. Thirteen surface disinfection methods were compared for their efficacy in killing E. coli O157:H7 on lettuce leaf and root surfaces. E. coli O157:H7 initially at 5.8 or 6.8 log CFU/leaf piece or root was not detected by enumeration (lettuce leaves and roots and was also validated for inactivating Salmonella and L. monocytogenes. PMID:19350966

Zhang, Guodong; Ma, Li; Beuchat, Larry R; Erickson, Marilyn C; Phelan, Vanessa H; Doyle, Michael P

2009-02-01

285

Quantitative control of Lettuce mosaic virus fitness and host defence inhibition by P1-HCPro P1-HC Pro do Lettuce mosaic virus atua de forma quantitativa na inibição da resposta de defesa do hospedeiro e adaptação viral  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two Lettuce mosaic virus isolates capable of overcoming the resistance afforded by the resistance gene mo1² in lettuce, LMV-AF199 from Brazil, and LMV-E, an European isolate, were evaluated for the rapidity and severity of symptoms induced on the lettuce variety Salinas 88 (mo1²). The mosaic symptoms on Salinas 88 plants inoculated with LMV-AF199 appeared 7 days post-inoculation (dpi) and 15 dpi for LMV-E. The symptoms induced by LMV-AF199 in this cultivar were also more severe than those i...

Renate Krause-Sakate; Florence Richard-Forget; Elise Redondo; Marcelo Agenor Pavan; Francisco Murilo Zerbini; Thierry Candresse; Olivier Le Gall

2007-01-01

286

Produção de alface em NFT e Floating aproveitando água salobra e o rejeito da dessalinização Lettuce production under NFT and Floating using brackish groundwater and the reject from its desalination  

Directory of Open Access Journals (Sweden)

Full Text Available Plantas de alface cv. Elba foram cultivadas em dois sistemas hidropônicos, Floating e NFT, com o objetivo de avaliar três tipos de água: a água salobra natural (2,47 dS m-1 obtida a partir de um poço profundo; água doce (0,11 dS m-1 produzido por dessalinização por osmose inversa, e o rejeito salino (5,15 dS m-1, um efluente do processo de dessalinização. Estas águas foram combinadas em seis tratamentos resultantes da sua utilização alternada para preparar a solução nutritiva (SN e/ou substituir as perdas por evapotranspiração (ETc. O experimento foi conduzido em casa de vegetação na região semiárida de Pernambuco, utilizando 48 unidades experimentais em blocos casualizados em esquema fatorial 6x2 com quatro repetições. O rendimento da alface (massa de matéria fresca foi maior nas condições do Floating. O uso exclusivo da água do poço profundo e do rejeito de dessalinizadores diminuiu 22,7 e 39,6% a produção de alface, respectivamente. Para uma melhor combinação de águas doces e salobras, o uso de água salobra para repor a perda por ETc pode aumentar a produção de alface em relação ao uso dessas águas para preparar a SN, estes resultados foram registrados para a água do poço profundo e o rejeito.Plants of lettuce cv. Elba were grown under two hydroponic systems, Floating and NFT, aiming to evaluate three water resources: natural brackish water (2,47 dS m-1 obtained from a deep well; fresh water (0,11 dS m-1 produced by reverse osmosis desalination; and reject brine (5,15 dS m-1, a wastewater from desalination process. These waters were combined in six treatments resulted from their alternated use to prepare nutrient solution (NS and/or replace the evapotranspiration loss (ETc. The experiment was carried out under a greenhouse condition in the semiarid region of Pernambuco State, Brazil; 48 experimental units were used for both hydroponic systems. The lettuce yield (shoot fresh matter was higher under Floating conditions. The single use of deep well water and reject brine decreased 22.7 and 39.6% the lettuce yield, respectively. For a better combination of fresh and brackish waters, the use of brackish water to replace ETc loss may increase the lettuce yield in comparison to use these waters to prepare the NS; this result was registered for deep well water and reject.

Alexandre Nascimento dos Santos

2011-06-01

287

Molecular mapping of the viral determinants of systemic wilting induced by a Lettuce mosaic virus (LMV) isolate in some lettuce cultivars.  

Science.gov (United States)

The isolate AF199 of Lettuce mosaic virus (LMV, genus Potyvirus) causes local lesions followed by systemic wilting and plant death in the lettuce cultivars Ithaca and Vanguard 75. Analysis of the phenotype of virus chimeras revealed that a region within the P1 protein coding region (nucleotides 112-386 in the viral genome) and/or another one within the CI protein coding region (nucleotides 5496-5855) are sufficient together to cause the lethal wilting in Ithaca, but not in Vanguard 75. This indicates that the determinants of this particular symptom are different in these two lettuce cultivars. The wilting phenotype was not directly correlated with differences in the deduced amino acid sequence of these two regions. Furthermore, transient expression of the LMV-AF199 proteins, separately or in combination, did not induce local necrosis or any other visible reaction in the plants. Together, these results suggest that the systemic wilting reaction might be due to RNA rather than protein sequences. PMID:15763148

Krause-Sakate, Renate; Redondo, Elise; Richard-Forget, Florence; Jadão, Adriana Salomão; Houvenaghel, Marie-Christine; German-Retana, Sylvie; Pavan, Marcelo Agenor; Candresse, Thierry; Zerbini, F Murilo; Le Gall, Olivier

2005-05-01

288

Freshwater aquatic plant biomass production in Florida  

Energy Technology Data Exchange (ETDEWEB)

About 8% (1.2 million ha) of the total surface area of Florida is occupied by freshwater. Many of these water bodies are eutrophic. Nutrients present in these water bodies can be potentially used to culture aquatic plants as a possible feedstock for methane production. This paper summarizes the results of known research findings on biomass production potential of freshwater aquatic plants in Florida and identifies key research needs to improve the quality and quantity of biomass yields. Among floating aquatic plants, biomass yield potential was in the order of water-hyacinth > water lettuce > pennywort > salvinia > duckweed > azolla. Pennywort, duckweed, and azolla appear to perform well during the cooler months compared to other aquatic plants. Among emergent plants, biomass yield potential was in the order of southern wild rice > cattails > soft rush > bulrush. Cultural techniques, nutrient management, and environmental factors influencing the biomass yields were discussed. 68 references.

Reddy, K.R.; Sutton, D.L.; Bowes, G.

1983-01-01

289

Development of a simple extraction and oxidation procedure for the residue analysis of imidacloprid and its metabolites in lettuce using gas chromatography.  

Science.gov (United States)

Simple extraction and optimised oxidation procedures were developed for the determination of the total residues of imidacloprid and its metabolites (containing the 6-chloropicolyl moiety) in lettuce using a gas chromatography-micro electron capture detector (GC-?ECD). Samples were extracted with acetonitrile, and the extract was then evaporated. The remaining residues were dissolved in water and oxidised with potassium permanganate to yield 6-chloronicotinic acid (6-CAN). The acid residues were further dissolved in n-hexane:acetone (8:2, v/v) and then silylated with MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) to 6-chloronicotinic acid trimethylsilyl ester. Calibration curves were linear over the concentration ranges (0.025-5 ?g mL(-1)) with a determination coefficient (r(2)) of 0.991. The limits of detection and quantification were 0.015 and 0.05 mg kg(-1), respectively. Recoveries at two fortification levels ranged between 72.8% and 108.3% with relative standard deviation (RSD) lower than 8%. The method was effective, and sensitive enough to determine the total residues of imidacloprid and its metabolites in field-incurred lettuce samples. The identity of the analyte was confirmed using gas chromatography-tandem mass spectrometry (GC-MS/MS). PMID:24262575

Ko, Ah-Young; Rahman, Md Musfiqur; Abd El-Aty, A M; Jang, Jin; Park, Jong-Hyouk; Cho, Soon-Kil; Shim, Jae-Han

2014-04-01

290

Chemical control of downy mildew on lettuce and basil under greenhouse.  

Science.gov (United States)

Eight experimental trials were carried out during 2007 and 2008 to evaluate the efficacy of different fungicides against downy mildew of lettuce (Bremia lactucae) and basil (Peronospora belbahrii) under greenhouse conditions, at temperatures ranging from 19 to 24 degrees C. The mixture fluopicolide (fungicide belonging to the + propamocarb hydrochloride (fungicide belonging to the new chemical class of acyl-picolides) was compared with metalaxyl m + copper, zoxamide + mancozeb, iprovalicarb + Cu, fenamidone + fosetyl-Al and azoxystrobin. Two treatments were carried out at 8-12 day interval on lettuce and basil. The artificial inoculation of B. lactucae on lettuce (cv Cobham Green) and P. belbahrii. on basil (cv Genovese gigante) was carried out by using 1 x 10(5) CFU/ml 24 h after the first treatment. In the presence of a medium-high disease severity, all fungicides tested in these trials were effective against downy mildew on lettuce and basil as the other fungicides already available. The importance of the availability of a number of different chemicals to control downy mildews is discussed. PMID:20222581

Gullino, M L; Gilardi, G; Garibaldi, A

2009-01-01

291

UPTAKE OF CADMIUM FROM PHOSPHATE FERTILIZERS BY PEAS, RADISHES, AND LETTUCE  

Science.gov (United States)

Cadium uptake from phosphate fertilizers by radish (Raphanus sativa) lettuce (Latuca sativa) and garden peas (Pisum satium) was investigated in the greenhouse. Fertilizer in all treatments was applied at the rate of 100 P/g soil to pots containing 4kg soil. When reagent grade mon...

292

Occurrence and distribution of lettuce mosaic disease in Tehran province from Iran.  

Science.gov (United States)

Lettuce mosaic virus (LMV) Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) were identified in fields of Tehran province. In this study 452 leaf samples were collected from the fields throughout the Tehran province during 2002 and 2003. Distribution of Lettuce mosaic virus (LMV), Cucumber mosaic virus (CMV), Tomato spotted wilt virus (TSWV)and Arabis mosaic virus (ArMV) was determined with DAS-ELISA. Percentage of single Infection to LMV. CMV or TSWV was 20.58, 15.93 and 9.96% respectively. Also 15.28% of samples were co- infected with LMV+CMV, 8.19% with LMV+TSMV and 7.74% with CMV+TSWV. 4.65% of samples were Infected to all of these three viruses. LMV was found in 48.69%, CMV in 43.59% and TSWV in 30.54% of samples totally. Therefore LMV is major dominant agent of lettuce mosaic disease in Tehran province. This is the first report of occurrence of TSWV on lettuce in Iran and first report of CMV and LMV in Tehran province. PMID:15756832

Soleimani, P; Mossahebi, G H; Koohi-Habibi, M; Zad, J; Hosseini-Farhangi, S

2004-01-01

293

Effect of Garbage Compost on the 3,4-Benzpyrene Content of Carrots and Head Lettuce.  

Science.gov (United States)

Carrots (Daucus carota) and head lettuce (Lactuca sativa) were cultivated in concrete-framed parcels of 10 m exp 2 surface area, in which the soil containing 300 or 600 dz (1 dz = 100 kg) of garbage compost per hectare had stood for a year. The soil consi...

R. Siegfried

1975-01-01

294

Comparative Study of Ascorbic Acid and Tocopherol Concentrations in Hydroponic- and Soil-Grown Lettuces  

Directory of Open Access Journals (Sweden)

Full Text Available Hydroponically-grown produce may be a way of helping to feed the world a variety of fruits and vegetables, regardless of soil quality, space availability or climate. The objective of this study was to determine whether hydroponicallygrown lettuce contains as much ascorbic acid and tocopherol as soil-grown lettuce. We analyzed four varieties of lettuce, including: Waldmann’s Dark Green, Red Lollo Antago, Red Romaine Annapolis, and Butterleaf. The tocopherol content of hydroponically-grown Waldmann’s Dark Green, Red Lollo Antago, and Red Romaine Annapolis was 229%, 497% and 492% higher, respectively, compared to their soil-grown counterpart. The ascorbic acid content of hydroponically-grown Waldmann’s Dark Green, Red Lollo Antago, and Red Romaine Annapolis was 93%, 171% and 216% higher, respectively, compared to their soil-grown counterparts. Hydroponically grown lettuce varieties are significantly higher in both ascorbic acid and tocopherol content than their soil-grown counterparts, and hydroponic gardening is a viable option for producing nutritious fruits and vegetables.

Drew N. Buchanan

2013-09-01

295

Survey of vesicular-arbuscular mycorrhizae in lettuce production in relation to management and soil factors  

Science.gov (United States)

The occurrence of vesicular-arbuscular mycorrhizae (VAM) root colonization and spore number in soil was assessed for 18 fields under intensive lettuce (Lactuca sativa L.) production in California during July and August of 1995. Data on management practices and soil characteristics were compiled for each field, and included a wide range of conditions. The relationship between these factors and the occurrence of VAM in these fields was explored with multivariate statistical analysis. VAM colonization of lettuce tended to decrease with the use of chemical inputs, such as pesticides and high amounts of P and N fertilizers. Addition of soil organic matter amendments, the occurrence of other host crops in the rotation, and soil carbon:phosphorus and carbon:nitrogen ratios, were positively associated with VAM colonization of lettuce roots. The number of VAM spores in soil was strongly correlated with the number of other host crops in the rotation, the occurrence of weed hosts and sampling date, but was more affected by general soil conditions than by management inputs. Higher total soil N, C and P, as well as CEC, were inversely related to soil spore number. A glasshouse study of the two primary lettuce types sampled in the field showed no significant differences in the extent of root colonization under similar growing conditions. The results of this study are compared with other studies on the effects of management and soil conditions on mycorrhizal occurrence in agriculture.

Miller, R. L.; Jackson, L. E.

1998-01-01

296

Robust production of virus-like particles and monoclonal antibodies with geminiviral replicon vectors in lettuce.  

Science.gov (United States)

Pharmaceutical protein production in plants has been greatly promoted by the development of viral-based vectors and transient expression systems. Tobacco and related Nicotiana species are currently the most common host plants for the generation of plant-made pharmaceutical proteins (PMPs). Downstream processing of target PMPs from these plants, however, is hindered by potential technical and regulatory difficulties owing to the presence of high levels of phenolics and toxic alkaloids. Here, we explored the use of lettuce, which grows quickly yet produces low levels of secondary metabolites and viral vector-based transient expression systems to develop a robust PMP production platform. Our results showed that a geminiviral replicon system based on the bean yellow dwarf virus permits high-level expression in lettuce of virus-like particles (VLP) derived from the Norwalk virus capsid protein and therapeutic monoclonal antibodies (mAbs) against Ebola and West Nile viruses. These vaccine and therapeutic candidates can be readily purified from lettuce leaves with scalable processing methods while fully retaining functional activity. Furthermore, this study also demonstrated the feasibility of using commercially produced lettuce for high-level PMP production. This allows our production system to have access to unlimited quantities of inexpensive plant material for large-scale production. These results establish a new production platform for biological pharmaceutical agents that are effective, safe, low cost, and amenable to large-scale manufacturing. PMID:21883868

Lai, Huafang; He, Junyun; Engle, Michael; Diamond, Michael S; Chen, Qiang

2012-01-01

297

Iodine effects on phenolic metabolism in lettuce plants under salt stress.  

Science.gov (United States)

Iodine, applied as iodate in biofortification programs (at doses of ?80 ?M), has been confirmed to improve the foliar biomass, antioxidant response, and accumulation of phenol compounds in lettuce plants. The changes in phenolic compounds induced by the iodate application appear to have functional consequences in the response of salt-stressed plants. Thus, the aim of the present study was to determine whether the application of iodate can improve the response of severe salinity stress and whether the resistance can be attributed to the phenolic metabolism in lettuce ( Lactuca sativa cv. Philipus), a glycophyte cultivated for food and consumed year round. In this work, the application of iodate, especially at 20 and 40 ?M, in lettuce plants under salinity stress (100 mM NaCl) exerted a significantly positive effect on biomass and induced higher activity in the enzymes shikimate dehydrogenase and phenylalanine ammonia-lyase as well as the lower MW phenol-degrading enzyme polyphenol oxidase. This increased hydroxycinnamic acids and derivatives in addition to total phenols, which appear to act as protective compounds against salinity. This study reveals that in agricultural areas affected by this type of stress, the application of iodate may be an effective strategy, as it not only improves lettuce plant growth but also supplements the human diet with phenolic compounds and the trace element iodine. PMID:23445402

Blasco, Begoña; Leyva, Rocio; Romero, Luis; Ruiz, Juan Manuel

2013-03-20

298

Frequência de Lettuce big-vein associated virus e Mirafiori lettuce big-vein virus em Plantas de alface no Estado de São Paulo e transmissão através de extrato vegetal e solo / Frequency of Lettuce big-vein associated virus and Mirafiori lettuce big-vein virus in symptomatic and assymptomatic lettuce plants and sap and soil transmission  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A presença de sintomas de 'big vein' ou engrossamento das nervuras em alface e a associação do Lettuce big-vein associated virus (LBVaV) e Mirafiori lettuce big-vein virus (MLBVV) foram verificadas por RT-PCR utilizando-se oligonucleotídeos específicos para ambos os vírus. Foram coletadas 366 planta [...] s sintomáticas nas regiões de Bauru, Campinas e Mogi das Cruzes no estado de São Paulo nos meses de junho e setembro de 2004 e abril e julho de 2005, e 18 plantas assintomáticas na região de Mogi das Cruzes no mês de dezembro de 2004. Infecção mista do LBVaV e MLBVV foi detectada em 76,2% das plantas sintomáticas, em 11,5% somente o MLBVV foi detectado e em 6,6% somente o LBVaV. Nas plantas assintomáticas coletadas em dezembro na região de Mogi das Cruzes, em áreas de alta incidência da doença durante o inverno, foi detectada a presença de MLBVV em 9 amostras e LBVaV em 7 amostras. Quatro dessas amostras apresentaram infecção mista, indicando que o desenvolvimento de sintomas depende de fatores abióticos, como temperatura. A inoculação via extrato vegetal a partir de plantas de alface com infecção mista pelo MLBVV e LBVaV foi realizada a 16°C/ 10°C (dia/noite) e fotoperíodo de 11 horas, verificando-se que o MLBVV foi transmitido para Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa e para as cultivares de alface Trocadero e White Boston, enquanto o LBVaV foi transmitido apenas para a alface White Boston. Entretanto, nenhuma destas plantas apresentou sintomas da doença, com exceção de C. quinoa que apresentou sintomas de lesões locais. Plantio em solo proveniente de áreas com histórico da doença de Mogi das Cruzes permitiu a transmissão do LBVaV para alface cv. White Boston e do MLBVV para alface cv. Trocadero e White Boston, embora apenas a cv. White Boston tenha apresentado sintomas da doença. Em conjunto, estes resultados demonstram a dificuldade de transmissão de ambos os vírus, mesmo em condições de laboratório. Abstract in english The occurrence of big vein disease symptoms and the association of Lettuce big-vein associated virus (LBVaV) and Mirafiori lettuce big-vein virus (MLBVV) was evaluated by RT-PCR using specific primers for both viruses. A total of 366 symptomatic plants were collected during June and September 2004 a [...] nd during April and July 2005 at Bauru, Campinas and Mogi das Cruzes in São Paulo state, and 18 symptomless plants were collected in Mogi das Cruzes on December 2004. Mixed infection was detected in 76,2% of the symptomatic plants, 11,5% had only MLBVV and 6,6% had only LBVaV. In the symptomless plants collected in areas with high incidence of the disease throughout the winter, MLBVV was found in 9 plants and LBVaV in 7 plants. Four plants had both viruses, indicating that symptom development depends on abiotic factors, such as temperature. Plants with MLBVV and LBVaV (mixed infection) were used as source of virus in a host range assay at 16C/ 10°C (day/ night) and 11h light period. MLBVV was transmitted to Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa and lettuce cv. Trocadero and White Boston, while LBVaV was transmitted only to lettuce cv. White Boston. No symptons could be verified for these plants with the exception of C. quinoa that showed local lesions. Transmission through soil in areas with high incidence of the disease was observed for LBVaV to lettuce cv. White Boston and MLBVV for lettuce cv. Trocadero and White Boston, but only cv. White Boston showed symptoms. Together, these results demonstrate the difficulties in transmitting both viruses, even under controlled laboratory conditions.

Sanches, Márcio Martinello; Krause-Sakate, Renate; Zerbini, Francisco Murilo; Rosales, Marlene; Le Gall, Olivier; Pavan, Marcelo Agenor.

299

Effect of different concentrations of diluted seawater on yield and quality of lettuce  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english This study was carried out to investigate the effects of irrigating lettuce (Lactuca sativa L. cv. Funly) with different concentrations of diluted seawater (0%, 2.5%, 5%, 10%, 15%, 20%) on the fresh yield, marketable yield and quality (DM, total soluble solids, titratable acidity, total sugar, vitam [...] in C, NO3-N, protein, and total oxalate content). The experiments were conducted in a greenhouse in the autumn of 2012. The fresh yield, marketable yield, and DM of lettuce irrigated with 2.5% and 5% seawater were similar to those of control, but these parameters decreased in response to 10% seawater, and the lowest values were obtained in response to 20% seawater. The 2.5% seawater treatment had no effect on the vitamin C and NO3-N content, but both significantly decreased when lettuce was irrigated with seawater concentrations higher than 2.5%. Total soluble solids, total sugar, and protein content significantly increased in response to low salinity (2.5% and 5%) but decreased in response to increasing seawater stress. The titratable acidity values remained unchanged under the various saline conditions. Irrigation with diluted seawater did not affect the total oxalate content up to a concentration of 5%, but increasing the concentration of seawater above 5% increased oxalate content. The results of this study demonstrated that low concentrations of seawater are suitable for lettuce production and lettuce can be grown successfully using diluted seawater at concentrations of 2.5% and 5%.

Ahmet, Turhan; Hayrettin, Kuscu; Nese, Ozmen; Mehmet, Sitki Serbeci; Ali, Osman Demir.

300

Plant lesions promote the rapid multiplication of Escherichia coli O157:H7 on postharvest lettuce.  

Science.gov (United States)

Several outbreaks of Escherichia coli O157:H7 infections have been associated with minimally processed leafy vegetables in the United States. Harvesting and processing cause plant tissue damage. In order to assess the role of plant tissue damage in the contamination of leafy greens with E. coli O157:H7, the effect of mechanical, physiological, and plant disease-induced lesions on the growth of this pathogen on postharvest romaine lettuce was investigated. Within only 4 h after inoculation, the population sizes of E. coli O157:H7 increased 4.0-, 4.5-, and 11.0-fold on lettuce leaves that were mechanically bruised, cut into large pieces, and shredded into multiple pieces, respectively. During the same time, E. coli O157:H7 population sizes increased only twofold on leaves that were left intact after harvest. Also, the population size of E. coli O157:H7 was 27 times greater on young leaves affected by soft rot due to infection by Erwinia chrysanthemi than on healthy middle-aged leaves. Confocal microscopy revealed that leaf tip burn lesions, which are caused by a common physiological disorder of lettuce, harbored dense populations of E. coli O157:H7 cells both internally and externally. Investigation of the colonization of cut lettuce stems by E. coli O157:H7 showed that the pathogen grew 11-fold over 4 h of incubation after its inoculation onto the stems, from which large amounts of latex were released. The results of this study indicate that plant tissue damage of various types can promote significant multiplication of E. coli O157:H7 over a short time and suggest that harvesting and processing are critical control points in the prevention or reduction of E. coli O157:H7 contamination of lettuce. PMID:18641153

Brandl, M T

2008-09-01

 
 
 
 
301

Cadmium determination in lettuce grown in contaminated soil by INAAA and GFAAS  

Energy Technology Data Exchange (ETDEWEB)

Although Cd is not essential for the mammalian organism, it follows in body the same pathways of essential elements such as zinc and copper. There is evidence that the Cd induced reduction of Ca absorption, may lead to the development of osteoporosis. Anthropogenic activities associated with industrial activities, mining and use of fertilizers, limestone pesticides in agriculture are the main sources of Cd enrichment in soils. Due to the possibility that Cd being absorbed by plants and through them to reach the food chain, interest has increased in regard to developing techniques for remediation of contaminated sites. The addition of substances capable of immobilizing the toxic elements from the soil is a procedure that has been used for remediation of contaminated sites. The function of these substances is to reduce the mobility and bioavailability of potentially toxic elements in the soil. In this study, five doses of phosphorus as triple phosphorus were used in a number of lettuce plants grown in contaminated soil. The concentration of Cd present in lettuce leaves treated with phosphate was compared with the Cd absorbed by the control plant leaves. Instrumental Neutron Activation Analysis (INAA) and Graphite-Furnace Absorption Atomic Spectrometry (GFAAS) were the analytical methods used to determine Cd contents in lettuce leaves. The objective was to evaluate the performance of the employed analytical methods: INAA and GFAAS in the assessment of the efficiency of phosphorus treatments to reduce the Cd concentrations in leaves of lettuce. Results obtained indicated that both analytical methods were efficient to discriminate the response of Cd concentration in lettuce as a function of soil treatment with phosphorus. Although INAA has shown a positive performance in this study, GFAAS seemed more appropriate because its sensitivity was much higher than that obtained by INAA, in the experimental conditions. (author)

Armelin, Maria Jose A.; Maihara, Vera A.; Saiki, Mitiko, E-mail: marmelin@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Trevizam, Anderson R.; Silva, Maria Ligia S. [Universidade Estadual do Centro Oeste (UNICENTRO), Guarapuava, PR (Brazil); Muraoka, Takashi, E-mail: muraoka@cena.usp.b [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil)

2011-07-01

302

Reduction of Escherichia coli 0157:H7 in shredded iceberg lettuce by chlorination and gamma irradiation  

Science.gov (United States)

Lettuce was inoculated with a six-strain cocktail of acid-adapted Escherichia coli 0157:H7 at a level of 1×10 7 CFU/g. Following chlorination at 200 ?g/ml, the lettuce was irradiated at 0.15, 0.38, or 0.55 kGy using a 60Co source. Survival of E. coli 0157:H7, aerobic mesophiles and yeast and molds were measured over a period of 10 days. For quality analysis, chlorinated lettuce was subjected to irradiation at 0.33 and 0.53 kGy and stored at 1.0°C, 4.0°C or 7.0°C. Changes in texture and color were determined by instrumental means and changes in flavor, odor, and visual quality were determined by sensory testing. Chlorination plus irradiation at 0.55 kGy produced a 5.4-log reduction in E. coli 0157:H7 levels. Chlorination alone reduced the E. coli 0157:H7 counts by 1-2 logs. Irradiation at 0.55 kGy was also effective in reducing standard plate counts and yeast and mold counts. Irradiation at this level did not cause softening of lettuce and sensory attributes were not adversely affected. In general, appearance and flavor were affected more by the length of storage than by temperature conditions. The 5+log reduction in E. coli counts and lack of adverse effects on sensory attributes indicate that low-dose irradiation can improve the safety and shelf-life of fresh-cut iceberg lettuce for retail sale or food service.

Foley, D. M.; Dufour, A.; Rodriguez, L.; Caporaso, F.; Prakash, A.

2002-03-01

303

Reduction of Escherichia coli 0157:H7 in shredded iceberg lettuce by chlorination and gamma irradiation  

Energy Technology Data Exchange (ETDEWEB)

Lettuce was inoculated with a six-strain cocktail of acid-adapted Escherichia coli 0157:H7 at a level of 1x10{sup 7} CFU/g. Following chlorination at 200 {mu}g/ml, the lettuce was irradiated at 0.15, 0.38, or 0.55 kGy using a {sup 60}Co source. Survival of E. coli 0157:H7, aerobic mesophiles and yeast and molds were measured over a period of 10 days. For quality analysis, chlorinated lettuce was subjected to irradiation at 0.33 and 0.53 kGy and stored at 1.0 deg. C, 4.0 deg. C or 7.0 deg. C. Changes in texture and color were determined by instrumental means and changes in flavor, odor, and visual quality were determined by sensory testing. Chlorination plus irradiation at 0.55 kGy produced a 5.4-log reduction in E. coli 0157:H7 levels. Chlorination alone reduced the E. coli 0157:H7 counts by 1-2 logs. Irradiation at 0.55 kGy was also effective in reducing standard plate counts and yeast and mold counts. Irradiation at this level did not cause softening of lettuce and sensory attributes were not adversely affected. In general, appearance and flavor were affected more by the length of storage than by temperature conditions. The 5+log reduction in E. coli counts and lack of adverse effects on sensory attributes indicate that low-dose irradiation can improve the safety and shelf-life of fresh-cut iceberg lettuce for retail sale or food service.

Foley, D.M. E-mail: dfoley@chapman.edu; Dufour, A.; Rodriguez, L.; Caporaso, F.; Prakash, A

2002-03-01

304

Factors important for the shelf-life of minimally processed lettuce  

DEFF Research Database (Denmark)

The minimally processed vegetable industry has been increasing rapidly due to change in lifestyle. Both women and men work outside home and have less time to cook and need more convenience and time saving products, which also present fresh and healthy characteristics. Iceberg lettuce (Lactuca sativa L.) is one of the most popular fresh-cut vegetables. Although an increase in the number of mixed salads in retail food chains is evident, their short shelf-life due to rapid browning and off-odour is a problem that need research. Therefore, the aim of this PhD project was to investigate factors important for the shelf-life of minimally processed iceberg lettuce and to propose a new methodology to measure browning in cut lettuce. Browning has been pointed out as the main factor limitating shelf-life in cut lettuce. The problem becomes complex because browning of cut lettuce is difficult to measure. A novel method using image analysis for the measurement of browning in minimally processed lettuce was developed and presented in paper I. The method used a flatbed scanner for image acquisition, colour dye patches for colour correction, and colour thresholding to quantify the browning, that was expressed as brown area fraction. Cut lettuce was stored at 5°C for 6 days and plus 1 day at room temperature (day 7). Changes in browning were assessed at 2, 6 and 7 days of storage using image analysis. The result showed an increase in browning as time and temperature of storage increased. It was concluded that this technique can be used for measuring the browning in cut lettuce. Few studies are done on the formation of volatiles in cut lettuce. Temperature of storage and methods of preparation that minimized quality loss are highly desirable. As such, cutting direction and storage temperature were investigated to elucidate their influence on aroma formation and respiration rate in minimally processed lettuce, are presented in paper II. Lettuce was cut longitudinal and transverse to the mid-rib and stored at 6 and 10°C for 4 and 5 days. Changes in respiration rate were analyzed through the storage time, and aroma analysis was carried out after 4 and 5 days of storage in January and March, respectively. Respiration rate increased with increasing storage temperatures. Aroma formation was also influenced by storage temperature. Higher storage temperature allowed the increase of -longipinene, 2-methylbutanal and 3-methylbutanal. Transversal cut to the rib was strongly related with volatiles of lipoxygenase (LOX) pathway i.e. cis-3-hexenal, cis-3-hexenol and trans-2-hexenol, meanwhile longitudinal cut enhanced the formation of volatiles from other metabolic routes. Therefore, it was concluded that transversal cut cause a more severe damage to the tissue than longitudinal cut based on aroma production of LOX volatiles. It has been indicated that cultivar, season, packaging and storage time influence the type and concentration of volatile compounds, browning, chemical constituents and texture in vegetables. As part of this project, a more integrated study was undertaken for first time in lettuce to our knowledge. The study took into account the influence of cultivar, season, packaging and storage time. In order to achieve this, iceberg lettuce cultivars Platinas, Diamantinas and Morinas were harvested from June to September 2009. Lettuces were minimally processed and stored under three different treatments: two passive modified atmosphere packaging (MAP) built up by films of different permeabilities, F1 (OPALEN 65 AF) and F2 (OPP/PE-L 2040 AF), and storage in air. All packages were stored at 5°C. Gas composition, volatile compounds, physicochemical constituents, PPO activity and browning were assessed at 1, 5, 8 and 11 days of storage in packaged lettuce, whereas in air stored samples only at 1 and 5 days of storage. Additionally, respiration rate was only assessed in air stored samples and GC-O analysis was undertaken after 1 and 11 days of storage for cultivar Morinas packaged in passive MAP F2 in September. The study was divided into

Deza Durand, Karla Michelle

2013-01-01

305

Levantamento revela a predominância do Lettuce mottle virus em três regiões produtoras de alface no Estado de São Paulo Frequency of LMV, LeMoV and BiMV in three lettuce producing areas from São Paulo State  

Directory of Open Access Journals (Sweden)

Full Text Available Entre os problemas fitossanitários da cultura da alface estão as doenças causadas por vírus. Três vírus causam sintomas de mosaico praticamente indistinguíveis: o Lettuce mosaic virus (LMV, Potyvirus, o Lettuce mottle virus (LeMoV, Sequivirus e o Bidens mosaic virus (BiMV, Potyvirus. Através de RT-PCR utilizando-se oligonucleotídeos específicos para cada um destes vírus, amostras de alface e plantas invasoras, preferencialmente com sintoma de mosaico, foram coletadas em campos de produção de alface das regiões de Mogi das Cruzes, Campinas e Bauru no Estado de São Paulo e analisadas para a presença dos vírus. Verificou-se que o LeMoV foi o vírus encontrado com maior freqüência, seguido do LMV. A ocorrência de BiMV em alface foi extremamente baixa e restrita às regiões de Campinas e Bauru, onde também foi verificado em plantas invasoras como Bidens pilosa e Galinsoga parviflora. Esta ultima é hospedeira dos três vírus.Among the phytosanitary problems affecting lettuce culture are the diseases caused by viruses. Three viruses cause almost indistinguishable mosaic symptoms: Lettuce mosaic virus (LMV, Potyvirus, Lettuce mottle virus (LeMoV, Sequivirus and Bidens mosaic virus (BiMV, Potyvirus. By RT-PCR using specific primers for each virus, lettuce and weed samples, preferably with mosaic symptoms, and collected from lettuce fields in the regions of Mogi das Cruzes, Campinas and Bauru, São Paulo State, Brazil, were analyzed for the presence of these viruses. LeMoV was the most frequently found virus, followed by LMV. The occurrence of BiMV in lettuce was extremely low and restricted to the regions of Campinas and Bauru, where it was also found in weeds such as Bidens pilosa and Galinsoga parviflora. The latter plant is the host of these three viruses.

Bruno Rossitto De Marchi

2012-09-01

306

Levantamento revela a predominância do Lettuce mottle virus em três regiões produtoras de alface no Estado de São Paulo / Frequency of LMV, LeMoV and BiMV in three lettuce producing areas from São Paulo State  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Entre os problemas fitossanitários da cultura da alface estão as doenças causadas por vírus. Três vírus causam sintomas de mosaico praticamente indistinguíveis: o Lettuce mosaic virus (LMV, Potyvirus), o Lettuce mottle virus (LeMoV, Sequivirus) e o Bidens mosaic virus (BiMV, Potyvirus). Através de R [...] T-PCR utilizando-se oligonucleotídeos específicos para cada um destes vírus, amostras de alface e plantas invasoras, preferencialmente com sintoma de mosaico, foram coletadas em campos de produção de alface das regiões de Mogi das Cruzes, Campinas e Bauru no Estado de São Paulo e analisadas para a presença dos vírus. Verificou-se que o LeMoV foi o vírus encontrado com maior freqüência, seguido do LMV. A ocorrência de BiMV em alface foi extremamente baixa e restrita às regiões de Campinas e Bauru, onde também foi verificado em plantas invasoras como Bidens pilosa e Galinsoga parviflora. Esta ultima é hospedeira dos três vírus. Abstract in english Among the phytosanitary problems affecting lettuce culture are the diseases caused by viruses. Three viruses cause almost indistinguishable mosaic symptoms: Lettuce mosaic virus (LMV, Potyvirus), Lettuce mottle virus (LeMoV, Sequivirus) and Bidens mosaic virus (BiMV, Potyvirus). By RT-PCR using spec [...] ific primers for each virus, lettuce and weed samples, preferably with mosaic symptoms, and collected from lettuce fields in the regions of Mogi das Cruzes, Campinas and Bauru, São Paulo State, Brazil, were analyzed for the presence of these viruses. LeMoV was the most frequently found virus, followed by LMV. The occurrence of BiMV in lettuce was extremely low and restricted to the regions of Campinas and Bauru, where it was also found in weeds such as Bidens pilosa and Galinsoga parviflora. The latter plant is the host of these three viruses.

Bruno Rossitto, De Marchi; David Marques de Almeida, Spadotti; Milena Leite de, Oliveira; Márcio Martinello, Sanches; Renate, Krause-Sakate; Marcelo Agenor, Pavan.

307

Prevalence of Lettuce mosaic virus - common strain on three lettuce producing areas from São Paulo State / Prevalência da estirpe comum de Lettuce mosaic virus em três regiões produtoras de alface do estado de São Paulo  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O LMV ocorre em todo o mundo e é considerado um dos patógenos mais importantes para a cultura da alface. De acordo com a habilidade em contornar os genes de resistência mo1¹ e mo1² encontrados em alface, os isolados de LMV podem ser dividos em dois sub-grupos: LMV-Most, capazes de contornar a resist [...] ência propiciada por estes genes e de serem transmitidos pela semente nestas cutivares, e LMV-Common, que não são capazes de causar sintomas nestes cultivares, além de serem transmitidos pela semente somente em cultivares suscetíveis. Para avaliar a ocorrência destes dois tipos de isolados de LMV foram coletadas, durante 2002-2005, amostras de alface com sintomas de mosaico em áreas de produção de alface comercial das regiões de Campinas, Mogi das Cruzes e Bauru no estado de São Paulo. O RNA total foi utilizado para detecção por RT-PCR utilizando-se oligonucleotídeos universais para LMV que amplificam a porção N-terminal variável da capa protéica, localizada no terminal 3´do genoma. As amostras positivas foram analisadas por um segundo primer que amplifica um fragmento da região central (CI-VPg) do genoma viral. Um total de 1362 amostras foram avaliadas, tendo sido detectado o LMV em 504 amostras (37,29%). O LMV-Common prevaleceu em variedades suscetíveis (77,3%). O LMV-Most foi encontrado frequentemente associado a variedades portadoras do gene de tolerância mo1¹. Apesar da existência dos LMV-Most capazes de contornar a resistência em alface, estes não predominam em nossa condições. Abstract in english LMV is one of the most important pathogens of lettuce worldwide. Based on their ability to overcome the resistance genes mo1¹ and mo1² in lettuce, isolates can be divided in two types: LMV-Most, which can infect and are seed-borne in cultivars containing the mo1 gene and LMV-Common, which do not cau [...] se symptoms on these cultivars and are seed transmitted only in susceptible cultivars. To evaluate the occurrence of these two types of LMV isolates, a survey was carried out during 2002-2005 in three lettuce production areas from São Paulo State. Total RNA was used for the diagnosis of LMV isolates by RT-PCR using universal primers for the variable N-terminus of the capsid protein, in the 3' end of the genome. Positives samples were analyzed by a second RT-PCR using specifics primers for LMV-Most isolates designed to amplify a fragment from the central region (CI-VPg) of the genome. A total of 1362 samples showing mosaic symptoms were collected and 504 (37.29 %) were positives for LMV. On susceptible lettuce cultivars, LMV-Common was prevalent (77.3%). LMV-Most was found frequently associated with tolerant (mo1¹) lettuce cultivars. Susceptible cultivars correspond today for most of the area of lettuce production. So, despite the ability of LMV-Most isolates to overcome the resistance provided by the recessive mo1¹ gene, they are not prevalent in the conditions of São Paulo State.

Ana Carolina, Firmino; Renate, Krause-Sakate; Marcelo Agenor, Pavan; Norberto da, Silva; Sérgio Minoru, Hanai; Roberto Hiroto, Anbo; Thomas, Nietzsche; Olivier, Le Gall.

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Prevalence of Lettuce mosaic virus - common strain on three lettuce producing areas from São Paulo State Prevalência da estirpe comum de Lettuce mosaic virus em três regiões produtoras de alface do estado de São Paulo  

Directory of Open Access Journals (Sweden)

Full Text Available LMV is one of the most important pathogens of lettuce worldwide. Based on their ability to overcome the resistance genes mo1¹ and mo1² in lettuce, isolates can be divided in two types: LMV-Most, which can infect and are seed-borne in cultivars containing the mo1 gene and LMV-Common, which do not cause symptoms on these cultivars and are seed transmitted only in susceptible cultivars. To evaluate the occurrence of these two types of LMV isolates, a survey was carried out during 2002-2005 in three lettuce production areas from São Paulo State. Total RNA was used for the diagnosis of LMV isolates by RT-PCR using universal primers for the variable N-terminus of the capsid protein, in the 3' end of the genome. Positives samples were analyzed by a second RT-PCR using specifics primers for LMV-Most isolates designed to amplify a fragment from the central region (CI-VPg of the genome. A total of 1362 samples showing mosaic symptoms were collected and 504 (37.29 % were positives for LMV. On susceptible lettuce cultivars, LMV-Common was prevalent (77.3%. LMV-Most was found frequently associated with tolerant (mo1¹ lettuce cultivars. Susceptible cultivars correspond today for most of the area of lettuce production. So, despite the ability of LMV-Most isolates to overcome the resistance provided by the recessive mo1¹ gene, they are not prevalent in the conditions of São Paulo State.O LMV ocorre em todo o mundo e é considerado um dos patógenos mais importantes para a cultura da alface. De acordo com a habilidade em contornar os genes de resistência mo1¹ e mo1² encontrados em alface, os isolados de LMV podem ser dividos em dois sub-grupos: LMV-Most, capazes de contornar a resistência propiciada por estes genes e de serem transmitidos pela semente nestas cutivares, e LMV-Common, que não são capazes de causar sintomas nestes cultivares, além de serem transmitidos pela semente somente em cultivares suscetíveis. Para avaliar a ocorrência destes dois tipos de isolados de LMV foram coletadas, durante 2002-2005, amostras de alface com sintomas de mosaico em áreas de produção de alface comercial das regiões de Campinas, Mogi das Cruzes e Bauru no estado de São Paulo. O RNA total foi utilizado para detecção por RT-PCR utilizando-se oligonucleotídeos universais para LMV que amplificam a porção N-terminal variável da capa protéica, localizada no terminal 3´do genoma. As amostras positivas foram analisadas por um segundo primer que amplifica um fragmento da região central (CI-VPg do genoma viral. Um total de 1362 amostras foram avaliadas, tendo sido detectado o LMV em 504 amostras (37,29%. O LMV-Common prevaleceu em variedades suscetíveis (77,3%. O LMV-Most foi encontrado frequentemente associado a variedades portadoras do gene de tolerância mo1¹. Apesar da existência dos LMV-Most capazes de contornar a resistência em alface, estes não predominam em nossa condições.

Ana Carolina Firmino

2008-06-01

309

Micro-scale elemental partition in tissues of the aquatic plant Lemna minor L. exposed to highway drainage water  

International Nuclear Information System (INIS)

In the scope of a monitoring program to assess the environmental impact of automobile traffic over one main bridge in Lisbon, both water and duckweed (Lemna minor L.) were sampled from the road drainage tanks and analyzed for chemical elements. Plants uptake Cr, Mn, Cu, and Zn metals from rain water draining the bridge road. Nuclear microprobe elemental maps of cryosections of L. minor tissues showed that incorporated elements were internalized in fronds of the plant. This approach at micrometer level allows a better knowledge of the elemental tissue partitioning in this biomonitor organism

2013-07-01

310

Is Local Produce Safer? Microbiological Quality of Fresh Lettuce and Spinach from Grocery Stores and Farmers' Markets  

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Full Text Available There is a growing demand for fresh, safe, high-quality, and locally grown vegetables. This study compared microbial populations in Romaine lettuce, Bibb lettuce, and spinach procured from grocery stores and farmers’ markets throughout the course of a summer. Standard microbial techniques were used to analyze 42 samples for the presence of total aerobic mesophilic and psychrophilic bacteria; yeasts and molds; surface and internalized coliforms and Escherichia coli; and the pathogens E. coli O157:H7 and Salmonella spp. Large variations in counts were found between produce types, sampling days, and between grocery and farmers’ market samples. The average highest microbial loads were associated with spinach samples from the grocery store, with both total aerobic mesophilic and psychrophilic counts greater than 7.1 log CFU/g. Average psychrophilic counts were higher than mesophilic microorganisms in all samples tested. In general, lettuce from farmers’ markets had more bacterial, yeast, and mold presence than lettuce from grocery stores.

Emiria Soendjojo

2012-01-01

311

Comparison of Different Washing and Disinfection Protocols Used by Food Services in Southern Brazil for Lettuce (Lactuca sativa  

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Full Text Available Different protocols have been used for washing and disinfecting leafy vegetables in Brazilian food services, however its effect on microbial reduction was barely studied. The aim of this study was to evaluate the effectiveness of lettuce washing and disinfecting protocols used by food services. The treatments evaluated were: washing in potable tap water (T1; washing and dipping in potable tap water (T2; washing with potable tap water and dipping in a solution of sodium hypochlorite (200 ppm of free chlorine for 15 min (T3; and 30 min (T4; washing with potable tap water and dipping in 2% vinegar solution (T5; and 20% vinegar solution (T6. After the treatments, the samples were microbiologically evaluated to measure bacterial reductions. The microbial counts showed that the mean total mesophile reductions were: 0.64 log for T1, 0.75 log for T2, 2.06 log for T3, 2.46 log for T4, 1.68 log for T5 and 1.72 log for T6, and the mean total coliform reductions were: 1.11 log for T1, 1.09 log for T2, 2.29 log for T3, 2.35 log for T4, 1.6 log for T5 and 2.09 log for T6. Based on these results it can be concluded that protocols which used 200 ppm sodium hypochlorite for 15 to 30 min (T3 e T4, were the most effective, followed by treatment with 20% vinegar solution (T6. The latter method, however, turned the lettuce dark during the distribution period.

Ana Beatriz Almeida de Oliveira

2012-01-01

312

Development of genomic SSR markers for fingerprinting lettuce (Lactuca sativa L.) cultivars and mapping genes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Lettuce (Lactuca sativa L.) is the major crop from the group of leafy vegetables. Several types of molecular markers were developed that are effectively used in lettuce breeding and genetic studies. However only a very limited number of microsattelite-based markers are publicly available. We have employed the method of enriched microsatellite libraries to develop 97 genomic SSR markers. Results Testing of newly developed markers on a...

Rauscher Gilda; Simko Ivan

2013-01-01

313

Cadmium availability and accumulation by lettuce and rice Disponibilidade e acúmulo de cádmio por plantas de arroz e alface  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Among the toxic elements, Cd has received considerable attention in view of its association with a number of human health problems. The objectives of this study were to evaluate the Cd availability and accumulation in soil, transfer rate and toxicity in lettuce and rice plants grown in a Cd-contaminated Typic Hapludox. Two simultaneous greenhouse experiments with lettuce and rice test plants were conducted in a randomized complete block design with four replications. The treatments consisted ...

Bruno Fernando Faria Pereira; Danilo Eduardo Rozane; Suzana Romeiro de Araújo; Gabriel Barth; Rafaela Josemara Barbosa Queiroz; Thiago Assis Rodrigues Nogueira; Milton Ferreira Moraes; Cleusa Pereira Cabral; Antonio Enedi Boaretto; Eurípedes Malavolta

2011-01-01

314

Reasoned opinion on the modification of the existing MRLs for azoxystrobin in lettuce, spinach, celery, cardoon, spices and rhubarb  

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In accordance with Article 6 of Regulation (EC) No 396/2005, France received an application from the company Syngenta Agro SAS to modify the existing MRLs for the active substance azoxystrobin in lettuce, spinach, celery and cardoon. In order to accommodate for the intended use of azoxystrobin, France proposed to raise the existing MRLs to 15 mg/kg for spinach and similar, lettuces and other salad plants, celery and cardoon. Germany received an application from the plant protection service La...

2012-01-01

315

Agronomic and economic viability of intercropping onion and lettuce Viabilidade agroeconômica do cultivo consorciado de cebola e alface  

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The study aimed to evaluate the agronomic and economic performance of intercropping onion and lettuce on four plant densities of each species. The experiment was set up in completely randomized blocks, with four replications and treatments arranged in a 4 x 4 factorial. Treatments resulted from a combination of four (100, 80, 60, and 40% of recommended plant densities in monoculture) plant densities for both lettuce and onion. Intercropping did not affect the agronomic performance of onion or...

Da Mota, Wagner F.; Pereira, Rosimeire D.; Santos, Gizeli S.; Vieira, Janiele Ca?ssia B.

2012-01-01

316

Association mapping and marker-assisted selection of the lettuce dieback resistance gene Tvr1  

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Abstract Background Lettuce (Lactuca saliva L.) is susceptible to dieback, a soilborne disease caused by two viruses from the family Tombusviridae. Susceptibility to dieback is widespread in romaine and leaf-type lettuce, while modern iceberg cultivars are resistant to this disease. Resistance in iceberg cultivars is conferred by Tvr1 - a single, dominant gene that provides durable resistance. This study describes fine mapping of the resistance gene...

2009-01-01

317

Assessment of lettuce quality during storage at low relative humidity using Global Stability Index methodology Avaliação da qualidade da alface durante o armazenamento em baixa umidade relativa usando o Índice Global da Estabilidade  

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Full Text Available During postharvest, lettuce is usually exposed to adverse conditions (e.g. low relative humidity that reduce the vegetable quality. In order to evaluate its shelf life, a great number of quality attributes must be analyzed, which requires careful experimental design, and it is time consuming. In this study, the modified Global Stability Index method was applied to estimate the quality of butter lettuce at low relative humidity during storage discriminating three lettuce zones (internal, middle, and external. The results indicated that the most relevant attributes were: the external zone - relative water content, water content , ascorbic acid, and total mesophilic counts; middle zone - relative water content, water content, total chlorophyll, and ascorbic acid; internal zone - relative water content, bound water, water content, and total mesophilic counts. A mathematical model that takes into account the Global Stability Index and overall visual quality for each lettuce zone was proposed. Moreover, the Weibull distribution was applied to estimate the maximum vegetable storage time which was 5, 4, and 3 days for the internal, middle, and external zone, respectively. When analyzing the effect of storage time for each lettuce zone, all the indices evaluated in the external zone of lettuce presented significant differences (p Durante a pós-colheita a alface é exposta a condições adversas (baixa umidade relativa que reduzem a qualidade do vegetal. A fim de avaliar sua vida útil, um grande número de índices de qualidade tem que ser analisado, requerendo um cuidadoso delineamento experimental e um longo consumo de tempo. Neste trabalho, o método modificado do Índice Global da Estabilidade foi aplicado para estimar a qualidade da alface manteiga a uma baixa umidade relativa durante o armazenamento diferenciando três zonas (interna, média e externa. Os resultados indicaram que, para a zona externa, os índices mais relevantes foram o conteúdo da umidade relativa, conteúdo da água, ácido ascórbico e a contagem total de micro-organismos mesófilos. Para a zona média, foram conteúdo da umidade relativa, conteúdo da água, clorofila total, ácido ascórbico e, para a interna, conteúdo da umidade relativa, água ligada, conteúdo da água e a contagem total de micro-organismos mesófilos. Foi proposto um modelo matemático entre o Índice Global da Estabilidade e qualidade visual geral para cada zona da alface. Ademais, foi aplicada a distribuição de Weibull para estimar o tempo da vida útil do vegetal, o qual foi: 5, 4 e 3 dias para as zonas interna, média e externa, respectivamente. Quando foi estudado o efeito do tempo de armazenamento para cada zona da alface, todos os índices avaliados na zona externa mostraram diferenças significativas (p < 0,05. Para as zonas interna e média, todos os índices medidos, com exceção do conteúdo da água e do total de clorofila, mostraram diferenças significativas (p < 0,05.

María Roberta Ansorena

2012-06-01

318

Identification of Fusarium oxysporum f. sp. lactucae race 1 as the causal agent of lettuce wilt in Brazil  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The objective of this work was to assess the virulence to lettuce cultivars and host specificity and to identify races of Fusarium oxysporum f. sp. lactucae (FOLac) isolates associated with lettuce wilt in Brazil. Thirty-one isolates identified based on morphology were inoculated in a set of lettuce [...] cultivars for race determination. Plantlets of 'Elisa', 'Vera', and 'Red Salad Bowl' cultivars were inoculated with all isolates using a root-dipping method. Isolates were also inoculated in species of Asteraceae and other botanical families. 'Elisa' and 'Vera' were susceptible to 27 isolates while 'Red Salad Bowl' was resistant to all isolates. Plants other than lettuce were not infected by any of the isolates, suggesting their specificity to lettuce. All pathogenic isolates were assigned to race 1 and used to evaluate a PCR protocol with primers targeting race 1. Only amplicons associated with race 1 pattern were observed for all pathogenic isolates but not for one non-pathogenic isolate, thus leading us to conclude that FOLac race 1 is so far the sole causal agent of lettuce wilt in Brazil.

Cléia S., Cabral; Kátia R., Brunelli; Hélcio, Costa; Maria Esther de N., Fonseca; Leonardo S., Boiteux; Ailton, Reis.

319

In vitro antagonists of Rhizoctonia solani tested on lettuce: rhizosphere competence, biocontrol efficiency and rhizosphere microbial community response.  

Science.gov (United States)

The rhizosphere competence of 15 in vitro antagonists of Rhizoctonia solani was determined 4 weeks after sowing inoculated lettuce seeds into nonsterile soil. Based on the colonization ability determined by selective plating, eight strains were selected for growth chamber experiments to determine their efficacy in controlling bottom rot caused by R. solani on lettuce. Although in the first experiment all antagonists colonized the rhizosphere of lettuce with CFU counts above 2 x 10(6) g(-1) of root fresh weight, only four isolates significantly reduced disease severity. In subsequent experiments involving these four antagonists, only Pseudomonas jessenii RU47 showed effective and consistent disease suppression. Plate counts and denaturing gradient gel electrophoresis (DGGE) fingerprints of Pseudomonas-specific gacA genes amplified from total community DNA confirmed that RU47 established as the dominant Pseudomonas population in the rhizosphere of inoculated lettuce plants. Furthermore, the DGGE fingerprint revealed that R. solani AG1-IB inoculation severely affected the bacterial and fungal community structure in the rhizosphere of lettuce and that these effects were much less pronounced in the presence of RU47. Although the exact mechanism of antagonistic activity and the ecology of RU47 remain to be further explored, our results suggest that RU47 is a promising agent to control bottom rot of lettuce. PMID:19486156

Adesina, Modupe F; Grosch, Rita; Lembke, Antje; Vatchev, Tzenko D; Smalla, Kornelia

2009-07-01

320

Quality of fresh-cut Iceberg lettuce and spinach irradiated at doses up to 4 kGy  

Science.gov (United States)

Fresh-cut Iceberg lettuce packaged in modified atmosphere packages and spinach in perforated film bags were irradiated with gamma rays at doses of 0, 1, 2, 3, and 4 kGy. After irradiation, the samples were stored for 14 days at 4 °C. O2 levels in the packages of fresh-cut Iceberg lettuce decreased and CO2 levels increased with increasing radiation dose, suggesting that irradiation increased respiration rates of lettuce. Tissue browning of irradiated cut lettuce was less severe than that of non-irradiated, probably due to the lower O2 levels in the packages. However, samples irradiated at 3 and 4 kGy had lower maximum force and more severe sogginess than the non-irradiated control. In addition, ascorbic acid content of irradiated lettuce was 22-40% lower than the non-irradiated samples after 14 days of storage. The visual appearance of spinach was not affected by irradiation even at a dose of 4 kGy. Consumer acceptance suggested that more people would dislike and would not buy spinach that was treated at 3 and 4 kGy as compared to the non-irradiated sample. Overall, irradiation at doses of 1 and 2 kGy may be employed to enhance microbial safety of fresh-cut Iceberg lettuce and spinach while maintaining quality.

Fan, Xuetong; Guan, Wenqiang; Sokorai, Kimberly J. B.

2012-08-01

 
 
 
 
321

Construction of transplastomic lettuce (Lactuca sativa) dominantly producing astaxanthin fatty acid esters and detailed chemical analysis of generated carotenoids.  

Science.gov (United States)

The plastid genome of lettuce (Lactuca sativa L.) cv. Berkeley was site-specifically modified with the addition of three transgenes, which encoded ?,?-carotenoid 3,3'-hydroxylase (CrtZ) and ?,?-carotenoid 4,4'-ketolase (4,4'-oxygenase; CrtW) from a marine bacterium Brevundimonas sp. strain SD212, and isopentenyl diphosphate isomerase from a marine bacterium Paracoccus sp. strain N81106. Constructed transplastomic lettuce plants were able to grow on soil at a growth rate similar to that of non-transformed lettuce cv. Berkeley and generate flowers and seeds. The germination ratio of the lettuce transformants (T0) (98.8%) was higher than that of non-transformed lettuce (93.1 %). The transplastomic lettuce (T1) leaves produced the astaxanthin fatty acid (myristate or palmitate) diester (49.2% of total carotenoids), astaxanthin monoester (18.2%), and the free forms of astaxanthin (10.0%) and the other ketocarotenoids (17.5%), which indicated that artificial ketocarotenoids corresponded to 94.9% of total carotenoids (230 ?g/g fresh weight). Native carotenoids were there lactucaxanthin (3.8%) and lutein (1.3 %) only. This is the first report to structurally identify the astaxanthin esters biosynthesized in transgenic or transplastomic plants producing astaxanthin. The singlet oxygen-quenching activity of the total carotenoids extracted from the transplastomic leaves was similar to that of astaxanthin (mostly esterified) from the green algae Haematococcus pluvialis. PMID:24287848

Harada, Hisashi; Maoka, Takashi; Osawa, Ayako; Hattan, Jun-Ichiro; Kanamoto, Hirosuke; Shindo, Kazutoshi; Otomatsu, Toshihiko; Misawa, Norihiko

2014-04-01

322

Corky Root of Lettuce Caused by Strains of a Gram-Negative Bacterium from Muck Soils of Florida, New York, and Wisconsin  

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Slow-growing bacteria similar to the bacterium causing lettuce corky root (CR) in California (strain CA1) were isolated from muck soils of Florida, New York, and Wisconsin, using lettuce seedlings as bait. All strains were tested for reaction with polyclonal antibodies produced against strain CA1 and for pathogenicity on CR-susceptible (Salinas) and CR-resistant (Green Lake) lettuce cultivars in a greenhouse. Five strains from Florida, three from New York, and three from Wisconsin induced sev...

Bruggen, Ariena H. C.; Brown, Philip R.; Jochimsen, Kenneth N.

1989-01-01

323

Podridão de raízes causada por Pythium aphanidermatum, em cultivares de alface produzidas em sistema hidropônico / Root rot caused by Pythium aphanidermatum of lettuce cultivars produced in a hydroponic system  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A podridão de raízes, causada por Pythium aphanidermatum e outras espécies de Pythium, é a principal doença da alface cultivada em sistemas hidropônicos no Brasil. O presente trabalho teve como objetivo avaliar quatro cultivares comerciais de alface em relação à sensibilidade a podridão de raízes, c [...] ausada por P. aphanidermatum. Os estudos foram realizados em placas de Petri contendo ágar-água com plântulas de alface das cultivares crespa (Vera e Verônica) e lisa (Regina e Elisa), infestadas ou não com o patógeno. Com as mesmas cultivares foram realizados quatro experimentos em sistemas hidropônicos (Nutrient Film Technique), sendo dois em estufa coberta com plástico e sombrite e dois em estufa coberta apenas com plástico. As plântulas, infectadas ou não com P. aphanidermatum, foram transplantadas para os sistemas infestados ou não. Foi avaliada a severidade da doença e o desenvolvimento das plantas. Todas as cultivares foram suscetíveis à podridão de raízes nos experimentos realizados in vitro e in vivo. A presença do sombrite não reduziu a podridão de raízes em cultivares de alface produzidas no sistema hidropônico. A cultivar Regina apresentou maior massa de matéria seca da parte aérea e das raízes, na presença ou ausência do patógeno, sendo a mais indicada para o cultivo hidropônico na época mais quente do ano. Abstract in english Lettuce root rot caused by Pythium aphanidermatum and other Pythium species is the main disease in hydroponic systems in Brazil. The present work aimed to evaluate the behavior of four commercial lettuce cultivars as to their sensitivity to root rot caused by P. aphanidermatum in hydroponic systems. [...] Experiments were conducted in Petri dishes containing water-agar medium and seedlings of the crisp head lettuce cultivars (Vera and Verônica) and leafy lettuce cultivars (Regina and Elisa), infested or not with the pathogen. With the same cultivars, four other experiments were carried out in hydroponic systems (Nutrient Film Technique), two in a shaded greenhouse and the other two in a conventional greenhouse. Seedlings infected or not with P. aphanidermatum were transplanted to hydroponic systems infested or not with the pathogen. The disease severity and the plant development were evaluated. All cultivars were susceptible to root rot in both in vitro and in vivo experiments. The shading did not reduce root rot in the lettuce cultivars in hydroponic system. The cultivar Regina showed higher shoot and root dry mass in the presence or absence of the pathogen, constituting thus the most suitable cultivar for hydroponic systems during the hottest period of the year.

Pinto, Zayame Vegette; Cipriano, Matheus Aparecido Pereira; Galvão, José Abrahão Haddad; Bettiol, Wagner; Patrício, Flávia Rodrigues Alves; Santos, Amaury da Silva dos.

324

Potencial de rizobactérias na promoção de crescimento e controle da podridãoradicular em alface hidropônica / Potential of rhizobacteria to promote root rot growth and control in hydroponically cultivated lettuce  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Os objetivos do trabalho foram avaliar se isolados de rizobactérias do grupo fluorescente do gênero Pseudomonas: 1) produzem metabólitos envolvidos na promoção do crescimento (AIA e HCN); 2) têm potencial para controle biológico de Pythium aphanidermatum; 3) podem promover o crescimento de plantas d [...] e alface cultivadas em sistema hidropônico; 4) e verificar se há correspondência nas interações in vitro e in vivo desses microrganismos. Com esses objetivos, placas de Petri contendo meio de cultura ágar-água, com ou sem Pythium aphanidermatum, receberam sementes prégerminadas de alface tratadas com os isolados de rizobactérias. Os comprimentos do hipocótilo e da radícula foram medidos cinco ou sete dias após a incubação a 28 ºC. Dois experimentos foram conduzidos em casa de vegetação com plantas de alface hidropônica e 17 isolados bacterianos. As unidades experimentais receberam a suspensão dos isolados de Pseudomonas spp. e, uma semana depois, a suspensão de zoósporos de P. aphanidermatum. Avaliaram-se o escurecimento das raízes e a massa de matéria seca da parte aérea e das raízes das plantas. Os isolados produzem metabólitos que beneficiam o crescimento de alface mesmo na presença do patógeno. Os isolados LP15, LP25, LP28, LP44 e LP47 reduziram os danos causados por P. aphanidermatum nos experimentos realizados in vitro e in vivo. Este é o primeiro estudo que demonstrou que rizobactérias obtidas de solos brasileiros têm potencial para promover o controle biológico de P. aphanidermatum e o crescimento de plantas de alface em sistemas hidropônicos. Abstract in english The aims of this study were to evaluate whether rhizobacteria with hydroponic lettuce plants and 17 bacterial isolates. The experimental isolates of the fluorescent group of the genus Pseudomonas: 1) units received Pseudomonas spp. isolate suspension and, one week later, produce metabolites involved [...] in growth promotion (AIA and HCN); P. aphanidermatum zoospore suspension. The plants were evaluated for 2) have the potential for the biological control of Pythium root darkening and shoot and root dry matter mass. The isolates produce aphanidermatum; 3) promote the growth of lettuce cultivated in metabolites which benefit the growth of lettuce even in the presence of hydroponic system; 4) show correspondence in the in vitro and in vivo the pathogen. The isolates LP15, LP25, LP28, LP44 and LP47 reduced interactions. Thus, Petri dishes containing agar-water culture medium, the damage caused by P. aphanidermatum in experiments in vitro and in with or without Pythium aphanidermatum, received pre-germinated vivo. This is the first study which demonstrated that rhizobacteria seeds of lettuce treated with the rhizobacteria isolates. The lengths of obtained from Brazilian soils have the potential to promote the the hypocotyl and radicle were measured at five or seven days after biological control of P. aphanidermatum and the growth of lettuce incubation at 28 ºC. Two experiments were carried out in a greenhouse plants in hydroponic systems.

Cipriano, Matheus Aparecido Pereira; Patrício, Flávia Rodrigues Alves; Freitas, Sueli dos Santos.

325

Nitrogen fertilization on intercropping of lettuce and rocket / Adubação nitrogenada em consórcio de alface e rúcula  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O trabalho foi conduzido na UNESP, Jaboticabal-SP, de setembro a dezembro de 2006, com objetivo de avaliar o efeito da adubação nitrogenada em consórcio de alface e rúcula. O delineamento experimental foi de blocos casualizados completos, com quatro repetições, sendo os tratamentos arranjados em esq [...] uema fatorial 4 x 4 + 2. Os tratamentos resultaram da combinação de quatro doses de N para a alface (0, 65, 130 e 195 kg ha-1) e quatro doses de N para a rúcula (0, 65, 130 e 195 kg ha-1), mais dois tratamentos adicionais, correspondentes aos monocultivos de alface e rúcula. As cultivares utilizadas foram Verônica (alface) e Folha Larga (rúcula). O aumento da dose de N para ambas as culturas, em consórcio, proporcionou incrementos na massa fresca e produtividade de alface e da rúcula e maximizou o índice de eficiência de uso da área (1,84) na dose 127 kg ha-1 de N para a alface e 195 kg ha-1 de N para rúcula. Abstract in english The work was carried out at UNESP, Jaboticabal, São Paulo State, Brazil, from September to December 2006, to evaluate the effect of nitrogen fertilization on intercropping of lettuce and rocket. The experiment was conducted in a randomized complete block design, with four replications, treatments be [...] ing arranged in a 4 x 4 + 2 factorial design. The treatments were the result of a combination of four N rates for lettuce (0, 65, 130 and 195 kg ha-1) and four N rates for rocket (0, 65, 130 and 195 kg ha-1), plus two additional treatments, which corresponded to lettuce and rocket under single cropping. Veronica (lettuce) and Folha Larga (rocket) were the cultivars used. An increase in the N rate for both cultures, under intercropping system, caused fresh matter gains and higher yields for lettuce and rocket, maximizing the land equivalent ratio (1.84) at 127 kg ha-1 of N for lettuce and 195 kg ha-1 of N for rocket.

Aurélio P, Barros Júnior; Arthur B, Cecílio Filho; Bráulio Luciano A, Rezende; Diego RQ, Pôrto; Renato de M, Prado.

326

Baby-leaf and multi-leaf of green and red lettuces are suitable raw materials for the fresh-cut industry  

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Consumer demand for softer leaves with variation in taste, shape and colours has encouraged the development of new lettuce products of baby-sized leaves. The objective of this study was the comparison of whole-head lettuce, as the most common raw material for fresh-cut, with baby-leaf and multi-leaf as the newest baby-sized lettuce leaves. Lettuces (Lactuca sativa L) of the types Green Leaf, Red Leaf and Lollo Rosso were cultivated in the same field with different plant densities, under comme...

2012-01-01

327

Efeito da irrigação no desenvolvimento da alface crespa, em ambiente protegido, em Lavras, MG / Effect of irrigation on development of crisped lettuce, in protected environment, in Lavras, MG  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Com este trabalho, objetivou-se avaliar o efeito de lâminas de irrigação sobre o desenvolvimento da alface crespa, em ambiente protegido, na região de Lavras, MG. O experimento foi instalado em casa de vegetação com delineamento em blocos casualizados, em esquema fatorial 2 x 4, com quatro repetiçõe [...] s. Os tratamentos se constituíram de duas cultivares de alface, Verônica e Hortência, e quatro lâminas de irrigação, 75, 100, 125 e 150% de reposição de água, em que os resultados permitiram concluir que as duas cultivares de alface responderam igualmente à aplicação das lâminas de irrigação, sendo as massas frescas máximas, total e comercial, estimadas com a aplicação de 249,1 mm (125,8%) e 244,9 mm (123,7%), respectivamente; plantas com maior número de folhas (23,06 folhas) e maior massa fresca de folhas (296,43 g planta-1) foram obtidas com a aplicação de 235,3 mm (118,8%) e 243,1 mm (122,8%), respectivamente; o teor de matéria seca de folhas reduziu-se linearmente em função das lâminas de água aplicadas. Abstract in english The present work intended to evaluate the effect of irrigation depths on the development of crisped lettuce, in protected environment in the region of Lavras, Minas Gerais State, Brazil. The experiment was set up in a greenhouse with randomized blocks design in 2 x 4 factorial scheme, with four repl [...] ications. The treatments consisted of two lettuce cultivars, Verônica and Hortência, and four irrigation depths, 75, 100, 125 and 150% of water replacement. The results allow to conclude that the two cultivars of lettuce respond equally to application of irrigation depths, with the maximum, total and commercial fresh masses estimated with the application of 249.1 mm (125.8%) and 244.9 mm (123.7%), respectively; plants with higher number of leaves (23.06 leaves) and higher fresh mass of leaves (296.43 g plant-1) were obtained with the application of 235.3 mm (118.8%) and 243.1 mm (122.8%), respectively; the dry matter content of leaves reduced linearly with the applied water depths.

Renato C., Vilas Boas; Jacinto de A., Carvalho; Luiz A. A., Gomes; Kleber J. de, Souza; Reginaldo C., Rodrigues; Alexandre M. G. de, Sousa.

328

Erigeron bonariensis: hospedeira alternativa do Lettuce mosaic virus no Brasil Erigeron bonariensis: an alternative host of Lettuce mosaic virus in Brazil  

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Full Text Available O gênero Erigeron (Asteraceae, de plantas da vegetação espontânea, encontra-se amplamente disseminado nas regiões Sul e Sudeste do Brasil, sendo freqüentemente encontrado em lavouras perenes e anuais. Plantas de E. bonariensis com sintoma de mosaico, típico do induzido por vírus, foram coletadas no município de São Paulo e submetidas a análises ao microscópio eletrônico de transmissão, testes biológicos, sorológicos e moleculares. Em cortes ultrafinos do tecido foliar original, observaram-se inclusões tubulares e cata-ventos dispersos no citoplasma. Através de inoculação mecânica, somente Chenopodium amaranticolor, C. quinoa, Nicotiana benthamiana e N. clevelandii foram infetadas. Os resultados obtidos em ELISA foram negativos quando se utilizaram antissoros contra o Turnip mosaic vírus (TuMV e diferentes estirpes do Potato virus Y (PVY, constatando-se relacionamento sorológico com o Lettuce mosaic virus (LMV. Com a utilização de oligonucleotídeos específicos para LMV amplificaram-se fragmentos esperados de aproximadamente 280 pb, que seqüênciados confirmaram a identidade do vírus. A ocorrência do LMV em E. bonariensis, gênero da mesma família botânica da alface (Lactuca sativa, é de grande importância, pois talvez possa atuar como reservatório para infecção de campos de produção de alface. Este é o primeiro relato, no Brasil, de vírus infetando Erigeron sp., o qual só havia sido reportado como hospedeira natural do Bidens mottle virus (BiMoV e do Tomato spotted wilt virus (TSWV nos Estados Unidos.The genus Erigeron, Asteraceae family, comprises weed plants spread over Southern and Southeastern Brazil, and, frequently, is found among annual and perennial crop plants. Erigeron bonariensis L.plants showing symptoms of mosaic, similar to those caused by plant viruses, were collected in São Paulo State and submitted to electron microscopy, biological, serological and molecular analysis. Ultrathin sections of the original foliar tissues samples showed tubular and pinwheel inclusions dispersed in the cytoplasm of infected cells. Following transmission by mechanical inoculation, only Chenopodium amaranticolor, C. quinoa, Nicotiana benthamiana and N. clevelandii were infected. The ELISA results were negative with antisera against Turnip mosaic virus (TuMV and Potato virus Y (PVY and positive for Lettuce mosaic virus (LMV antiserum. With specific primers to LMV, 280 bp fragments were amplified and sequenced, confirming the virus identity as LMV. The occurrence of LMV in E. bonariensis, which belongs to the lettuce (Lactuca sativa family, is significant since it may also act as LMV reservoir for lettuce field crops. This is the first report in Brazil of a virus infecting Erigeron sp. which has also been reported as a natural host of Bidens mottle virus and Tomato spotted wilt virus in the United States.

Alexandre L. R. Chaves

2003-06-01

329

Further characterization of two sequiviruses infecting lettuce and development of specific RT-PCR primers.  

Science.gov (United States)

Lettuce mottle virus (LeMoV) and dandelion yellow mosaic virus (DaYMV) infect lettuce in South America and Europe, respectively. LeMoV and DaYMV possess isometric particles, occur at low concentrations in plants and have narrow host ranges. Partial genome sequences of both viruses were obtained using purified viral preparations and universal primers for members of the family Sequiviridae. DaYMV and LeMoV sequences were analyzed and showed identity with other members of the family. Universal primers that detect both viruses and specific primers for LeMoV and DaYMV were designed and used in RT-PCR-based diagnostic assays. These results provide the first molecular data on the LeMoV and DaYMV genomes and suggest that LeMoV is a member of the genus Sequivirus, probably distinct from DaYMV. PMID:17238013

Jadão, A S; Krause-Sakate, R; Liberti, D; Pavan, M A; Echer, M M; Svanella-Dumas, L; Zerbini, F M; Candresse, T; Le Gall, O

2007-01-01

330

Effects of vacuum and controlled atmosphere treatments on insect mortality and lettuce quality.  

Science.gov (United States)

Laboratory studies were conducted to determine the effects of vacuum and controlled atmosphere on mortality of aphids, Nasonovia ribisnigri (Mosley) and Macrosiphum euphorbiae (Thomas), and leafminer, Liriomyza langei Frick, and on the visual quality of iceberg lettuce at three different temperatures. Vacuum at 50 mbar and controlled atmosphere with 6% CO2 were effective in controlling aphids and leafminer larvae. Complete control of N. ribisnigri and M. euphorbiae was achieved with vacuum treatments and 6% CO2 CA treatments at 5 degrees C in 4 d. Mortality was >96% when leafminer larvae were treated with vacuum and 6% CO2 CA treatments for 4 d. However, leafminer pupae were more tolerant to the treatments and highest mortality was close to 60% in 4 d with CO2 under vacuum. None of the treatments had negative effects on visual quality of iceberg lettuce. Results from this study are encouraging and warrant further and large-scale research. PMID:14503580

Liu, Yong-Biao

2003-08-01

331

Influence of Cadmium and Lead Concentrations of Irrigation Water on Dry Matter Yield of Vegetables  

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Full Text Available The aim of the study was to find out the extent that cadmium and lead concentrations in irrigation water affect yield of vegetables like cabbage, lettuce and carrots negatively or positively. Experimental plots were established to produce cabbage, carrots and lettuce. The crops were irrigated with irrigation water of 0.05 and 0.1 mg L-1 Cd and 30 and 50 mg L-1 Pb concentrations. Results of analyzed crops samples showed that generally, there was a reduction of dry matter yield of crops produced. Dry matter yield of cabbage and lettuce treated with 0.05 mg L-1 Cd concentration of irrigation water reduced by 56.10 and 10.65%, respectively. At 0.1 mg L-1 Cd irrigation water concentration the reduction of cabbage and lettuce dry matter yield were 61.17 and 16.57%, respectively, compared with values of controlled crops. However, in the case of carrots there were increases in dry matter yield of 268 and 187%, respectively irrigating with water with Cd concentrations of 0.05 and 0.1 mg L-1. With Pb irrigated vegetables, dry matter yield for all the three crops reduced at all Pb irrigation water concentrations. Dry matter yield of Pb treated cabbage reduced by 56.6, 13.54% for lettuce and 35.83% for carrots at 30 mg L-1 Pb irrigation water concentration. At 50 mg L-1 Pb irrigation water concentration, dry matter contents of cabbage, lettuce and carrots reduced by 72.85, 43.23 and 24.57%, respectively, compared with values from controlled plots.

E. Mensah

2009-01-01

332

Development of genomic SSR markers for fingerprinting lettuce (Lactuca sativa L. cultivars and mapping genes  

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Full Text Available Abstract Background Lettuce (Lactuca sativa L. is the major crop from the group of leafy vegetables. Several types of molecular markers were developed that are effectively used in lettuce breeding and genetic studies. However only a very limited number of microsattelite-based markers are publicly available. We have employed the method of enriched microsatellite libraries to develop 97 genomic SSR markers. Results Testing of newly developed markers on a set of 36 Lactuca accession (33?L. sativa, and one of each L. serriola L., L. saligna L., and L. virosa L. revealed that both the genetic heterozygosity (UHe?=?0.56 and the number of loci per SSR (Na?=?5.50 are significantly higher for genomic SSR markers than for previously developed EST-based SSR markers (UHe?=?0.32, Na?=?3.56. Fifty-four genomic SSR markers were placed on the molecular linkage map of lettuce. Distribution of markers in the genome appeared to be random, with the exception of possible cluster on linkage group 6. Any combination of 32 genomic SSRs was able to distinguish genotypes of all 36 accessions. Fourteen of newly developed SSR markers originate from fragments with high sequence similarity to resistance gene candidates (RGCs and RGC pseudogenes. Analysis of molecular variance (AMOVA of L. sativa accessions showed that approximately 3% of genetic diversity was within accessions, 79% among accessions, and 18% among horticultural types. Conclusions The newly developed genomic SSR markers were added to the pool of previously developed EST-SSRs markers. These two types of SSR-based markers provide useful tools for lettuce cultivar fingerprinting, development of integrated molecular linkage maps, and mapping of genes.

Rauscher Gilda

2013-01-01

333

Effect of the soil type on the microbiome in the rhizosphere of field-grown lettuce  

Science.gov (United States)

The complex and enormous diversity of microorganisms associated with plant roots is important for plant health and growth and is shaped by numerous factors. This study aimed to unravel the effects of the soil type on bacterial communities in the rhizosphere of field-grown lettuce. We used an experimental plot system with three different soil types that were stored at the same site for 10 years under the same agricultural management to reveal differences directly linked to the soil type and not influenced by other factors such as climate or cropping history. Bulk soil and rhizosphere samples were collected 3 and 7 weeks after planting. The analysis of 16S rRNA gene fragments amplified from total community DNA by denaturing gradient gel electrophoresis and pyrosequencing revealed soil type dependent differences in the bacterial community structure of the bulk soils and the corresponding rhizospheres. The rhizosphere effect differed depending on the soil type and the plant growth developmental stage. Despite the soil type dependent differences in the bacterial community composition several genera such as Sphingomonas, Rhizobium, Pseudomonas, and Variovorax were significantly increased in the rhizosphere of lettuce grown in all three soils. The number of rhizosphere responders was highest 3 weeks after planting. Interestingly, in the soil with the highest numbers of responders the highest shoot dry weights were observed. Heatmap analysis revealed that many dominant operational taxonomic units were shared among rhizosphere samples of lettuce grown in diluvial sand, alluvial loam, and loess loam and that only a subset was increased in relative abundance in the rhizosphere compared to the corresponding bulk soil. The findings of the study provide insights into the effect of soil types on the rhizosphere microbiome of lettuce.

Schreiter, Susanne; Ding, Guo-Chun; Heuer, Holger; Neumann, Gunter; Sandmann, Martin; Grosch, Rita; Kropf, Siegfried; Smalla, Kornelia

2014-01-01

334

Produção de sementes de alface em cultivo hidropônico Lettuce seeds production in hydroponic system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sementes de alface das cultivares Deyse e Regina foram produzidas em estufa, no sistema hidropônico, com elevados rendimentos por planta e boa qualidade de sementes, quando comparados a resultados de sistema convencional, de canteiros em campo. Esses dados sugerem estudos de produção de sementes de alface em cultivo protegido.Lettuce seeds of Deyse and Regina cultivars were produced in greenhouse, in hydroponic system, with excelents rendiments per plant and seed quality, when compared...

2001-01-01

335

Insights into the economic viability of a new CEA system producing hydroponic lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new CEA (Controlled Environment Agriculture) system growing Boston lettuce, Lactuca Sativa cv. ?Vivaldi?, achieves the same quality and quantity of production every day of the year. The year-round constant quantity and quality production indicate potential for success. However, our research showed that out of nine selected U.S. locations with different climatic and economic conditions, the Northeast had 25.7 percent higher production costs for the same yield. The analysis indicated that giv...

Ilaslan, Gunes; White, Gerald B.; Langhans, Robert W.

2002-01-01

336

Dynamics of nonpersistent aphid-borne viruses in lettuce crops covered with UV-absorbing nets.  

Science.gov (United States)

Aphid-transmitted viruses frequently cause severe epidemics in lettuce grown under Mediterranean climates. Spatio-temporal dynamics of aphid-transmitted viruses and its vector were studied on lettuce (Lactuca sativa L.) grown under tunnels covered by two types of nets: a commercial UV-absorbing net (Bionet) and a Standard net. A group of plants infected by Cucumber mosaic virus (CMV, family Bromoviridae, genus Cucumovirus) and Lettuce mosaic virus (LMV, family Potyviridae, genus Potyvirus) was transplanted in each plot. The same virus-infected source plants were artificially infested by the aphid Macrosiphum euphorbiae (Thomas). Secondary spread of insects was weekly monitored and plants were sampled for the detection of viruses every two weeks. In 2008, the infection rate of both CMV and LMV were lower under the Bionet than under the Standard cover, probably due to the lower population density and lower dispersal rate achieved by M. euphorbiae. However, during spring of 2009, significant differences in the rate of infection between the two covers were only found for LMV six weeks after transplant. The spatial distribution of the viruses analysed by SADIE methodology was "at random", and it was not associated to the spatial pattern of the vector. The results obtained are discussed analyzing the wide range of interactions that occurred among UV-radiation, host plant, viruses, insect vector and environmental conditions. Our results show that UV-absorbing nets can be recommended as a component of an integrated disease management program to reduce secondary spread of lettuce viruses, although not as a control measure on its own. PMID:22226944

Legarrea, S; Betancourt, M; Plaza, M; Fraile, A; García-Arenal, F; Fereres, A

2012-04-01

337

Cold-induced imbibition damage of lettuce embryos: A study using cryo-scanning electron microscopy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The impact of rehydration on a multicellular organism was studied in lettuce (Lactuca sativa L.) embryos, using cryo-scanning electron microscopy (cryo-SEM). Naked embryos were sensitive to imbibitional stress, whereas embryos with an intact, thick-walled endosperm were not. Imbibitional injury to naked embryos was mainly confined to the outer 2-3 cell layers of the axis. These cells failed to swell and appeared poorly hydrated. Deeper layers were not affected even after extended periods of c...

2004-01-01

338

Changes in Acid Invertase Activity and Sugar Contents in Lettuce During Storage at Ambient Temperature  

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This study investigated the changes in acid invertase activity and sugar contents in lettuce (Lactuca sativa L. cvs. `Shizuka` and `Shisuko`) during storage at 20°C. Percent weight loss of the heads was highest after 2 days of storage. In both cultivars, the degree of greenness continuously declined with time. Respiration rate decreased in `Shisuko`, whereas the rate in` Shizuka` increased at the end of storage. The activity of acid invertase in soluble and cell wall-bound fractions d...

Wanraya Suthumchai; Toshiyuki Matsui; Kazuhide Kawada; Yusuke Kosugi

2006-01-01

339

Rhizoctonia solani as a component in the bottom rot complex of glasshouse lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The basal parts of maturing glasshouse lettuce can be attacked by several soil fungi, which cause bottom rot. Until recently quintozene was generally applied against this disease complex. The study of the causal fungi - especially Rhizoctonia solani - and their control was undertaken in view of the need for quintozene replacing fungicides.A survey revealed that Botrytis cinerea was the most frequently observed pathogen, especially in winter crops. The incidence of Sclerotinia minor, Sclerotin...

Kooistra, T.

1983-01-01

340

Marker-assisted reduction of redundancy in a genebank collection of cultivated lettuce  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To reduce the level of redundancy in a collection of cultivated lettuce, data from 160 amplified fragment length polymorphism (AFLP) fragments and 10 polymorphic microsatellites were used in combination with passport data and morphological data, the latter obtained from an experimental field trial performed for verification purposes. Based on the observed distribution of the number of marker differences between and within accessions, a minimum of three AFLP differences and two microsatellite ...

Treuren, R.; Groot, E. C.; Boukema, I. W.; Wiel, C. C. M.; Hintum, T. J. L.

2010-01-01

 
 
 
 
341

Influence of nickel nutrition and nitrogen source on growth and yield of lettuce in hydroponic culture  

Directory of Open Access Journals (Sweden)

Full Text Available Nickel (Ni is the most recently discovered essential element for higher plants. But there is limited information about the effect of this element on yield and nitrogen (N metabolism of different plants. In this research, the interaction of Ni supplement and N source was studied on nitrate accumulation and growth of lettuce (Lactuca sativa L. cv. Baker in solution culture. In a greenhouse experiment, lettuce plants were exposed to two Ni levels (0 and 0.04 µM in the form of NiCl2 and three N levels (5, 10, and 20 µM in the form of urea and ammonium nitrate. The plants were harvested 6 weeks after transplanting and the fresh weight of shoots and roots, total N concentration, nitrate concentration and Fe content of shoots were determined. The results indicated that shoot and root fresh weight of nitrate-fed plants were higher than urea-fed plants. Ni nutrition significantly enhanced the yield of urea-fed plants. The shoot nitrate concentration in nitrate-fed plants was significantly greater in comparison with urea-fed plants. On the other hand, nitrate concentration in the shoots of lettuce plants decreased significantly with Ni nutrition. Ni supplementation in urea-fed plants increased the shoot Fe content. The shoot concentration of total-N in the urea-fed plants increased with the Ni supplement. While, Ni had no significant effect on shoot concentration of total-N in the nitrate-fed plants. Addition of low levels of Ni to the nutrient solution, particularly to the urea-containing solution, improved the yield of lettuce. In addition, these plant leaves are safer for human consumption because the shoot nitrate content is significantly reduced by application of Ni.

F. Hosseini

2012-06-01

342

Combining leeway on farm and supply basin scales to promote technical innovations in lettuce production  

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We analysed the technical and organisational leeway available to market gardeners and marketing firms in the Roussillon region, southeastern France, to meet two qualitative objectives: a longer marketing period and an increasing product safety by replacing soil chemical disinfection with solarisation. We surveyed 33 market gardeners producing lettuce and selling through three different marketing firms. Farmers used two alternative models to stagger harvests and three to introduce solarisation...

Navarrete, Mireille; Le Bail, Marianne; Papy, Franc?ois; Bressoud, Fre?de?rique; Tordjman, Sophie

2006-01-01

343

Crop to wild introgression in lettuce: following the fate of crop genome segments in backcross populations  

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Background: After crop-wild hybridization, some of the crop genomic segments may become established in wild populations through selfing of the hybrids or through backcrosses to the wild parent. This constitutes a possible route through which crop (trans)genes could become established in natural populations. The likelihood of introgression of transgenes will not only be determined by fitness effects from the transgene itself but also by the crop genes linked to it. Although lettuce is generall...

Uwimana, B.; Smulders, M. J. M.; Hooftman, D. A. P.; Hartman, Y.; Tienderen, P. H.; Jansen, J.; Mchale, L. K.; Michelmore, R. W.; Visser, R. G. F.; Wiel, C. C. M.

2012-01-01

344

Rin4 Causes Hybrid Necrosis and Race-Specific Resistance in an Interspecific Lettuce Hybrid  

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Some inter- and intraspecific crosses may result in reduced viability or sterility in the offspring, often due to genetic incompatibilities resulting from interactions between two or more loci. Hybrid necrosis is a postzygotic genetic incompatibility that is phenotypically manifested as necrotic lesions on the plant. We observed hybrid necrosis in interspecific lettuce (Lactuca sativa and Lactuca saligna) hybrids that correlated with resistance to downy mildew. Segregation analysis revealed a...

Jeuken, M. J. W.; Zhang, N.; Mchale, L. K.; Pelgrom, K. T. B.; Boer, E.; Lindhout, P.; Michelmore, R.; Visser, R. G. F.; Niks, R. E.

2009-01-01

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