WorldWideScience

Sample records for horticulturists

  1. Notice to nurserymen of the nameing and release for propagation of lufin white an american hardy hibiscus cultivar

    Science.gov (United States)

    Hibiscus laevis ‘LUFKIN WHITE’, a new hardy native ornamental hibiscus cultivar is recommended for trial by nurserymen and horticulturists as a summer flowering perennial landscape plant nationwide but is particularly adapted to conditions in the South. ‘LUFKIN WHITE’ was selected for its exception...

  2. Two New Disease-Resistant Hibiscus: 'Lufkin Red' and 'Lufkin White'

    Science.gov (United States)

    The Agricultural Research Service, United States Department of Agriculture, has released Hibiscus laevis ‘Lufkin Red’ and ‘Lufkin White’, two new hardy native ornamental hibiscus. These cultivars are recommended for trial by gardeners and horticulturists as summer flowering perennial landscape pl...

  3. Legon Journal of the Humanitie_2.cdr

    African Journals Online (AJOL)

    user

    these texts, ethnicity, education and class status are tied to language. It is therefore ..... be central in typing the speaker of pidgin and broken GhaE, who is portrayed as a .... GhaE with pidgin elements to the British horticulturist at Aburi gardens.

  4. Deficit irrigation strategies

    DEFF Research Database (Denmark)

    Stikic, Radmilla; Savíc, Sladjana; Jovanovic, Zorica

    2010-01-01

    Book Description: Horticulture is the industry and science of plant cultivation, including the process of preparing soil for the planting of seeds, tubers, or cuttings. Horticulturists work and conduct research in the disciplines of plant propagation and cultivation, crop production, plant breeding...... grafting techniques at the seedling stage to overcome soil-borne diseases, the application of biotechnology tools in the conservation of critically endangered plant species, salinity tolerance of ornamental horticultural species, and others....

  5. Archaeometric study of Amazon ceramic

    International Nuclear Information System (INIS)

    Sabino, Claudia de Vilhena Schayer; Amaral, Angela Maria; Poirior, Andre Pierre Prous

    2002-01-01

    There is no evidence of urban civilization in Brazilian prehistory; most inhabitants lived in tribal organization, probably with regional economic integration among several independent tribes. There are few evidences of seasonal migrations between the coast and the inland of southern Brazil. Some specialized horticulturists competed among themselves but other groups lived more isolatedly and probably peacefully, in the upper interfluvial regions. The chiefdom system is supposed to have existed only along the Amazon River. In this region, some pottery makers may have been specialized craftsmen and finest ceramics, that should have been exported from one village/region to another, can be found. In this study we tested some limited possibilities in three different cultural and regional contexts to see if application of analytic analysis in economically and politically 'simple' societies should give any results. (author)

  6. Salvia divinorum: an hallucinogenic mint which might become a new recreational drug in Switzerland.

    Science.gov (United States)

    Giroud, C; Felber, F; Augsburger, M; Horisberger, B; Rivier, L; Mangin, P

    2000-08-14

    Salvia divinorum Epling & Jativa is an hallucinogenic mint traditionally used for curing and divination by the Mazatec Indians of Oaxaca, Mexico. Young people from Mexican cities were reported to smoke dried leaves of S. divinorum as a marijuana substitute. Recently, two S. divinorum specimens were seized in a large-scale illicit in-door and out-door hemp plantation. Salvinorin A also called divinorin A, a trans-neoclerodane diterpene, was identified in several organic solvent extracts by gas chromatography-mass spectrometry. The botanical identity of the plant was confirmed by comparing it to an authentic herbarium specimen. More plants were then discovered in Swiss horticulturists greenhouses. All these data taken together suggest that many attempts exist in Switzerland to use S. divinorum as a recreational drug. This phenomenon may be enhanced because neither the magic mint, nor its active compound are banned substances listed in the Swiss narcotic law.

  7. Tribes and chiefdoms: An analytical study of some Brazilian ceramics

    International Nuclear Information System (INIS)

    Sabino, C.V.S.; Prous, A.P.; Wuest, I.; Guapindaia, V.

    2003-01-01

    There is no evidence of urban civilization in Brazilian prehistory; most inhabitants lived in tribal organizations, probably with regional economic integration among several independent tribes. There is little evidence of seasonal migrations between the coastal and inland areas of southern Brazil. Some specialized horticulturists competed among themselves but other groups lived more in isolation, and probably peacefully, in the upper interfluvial regions.The chiefdom system is supposed to have existed only along the river Amazon. In this region, some pottery makers may have been specialized craftsmen, and the finest ceramics that could have been exported from one village or region to another can be found. Outside this region, pottery was generally plain, except the tupiguarani, which was partly decorated. In this study some limited possibilities were tested, in three different cultural and regional contexts, to find out if the application of chemical analysis to economically and politically 'simple' societies can produce any results of additional archaeological relevance. (author)

  8. Sex-linked strategies of human reproductive behavior.

    Science.gov (United States)

    Jaffe, K; Urribarri, D; Chacon, G C; Diaz, G; Torres, A; Herzog, G

    1993-01-01

    We present data on fertility characteristics in the Venezuelan population for each sex separately, allowing a detailed comparative analysis of the variance in fertility between males and females. We show that the fertility distribution for both sexes is discontinuous, that the average female has a larger number of offspring per individual than the average male, and that highly fertile males outnumber highly fertile females so that the total number of offspring produced by males and females is balanced. Results indicate that a few males are responsible for a relative higher fertility of the average female and that interactions between polyandric females with monogamic and polygynic males are common. Among the Yanomami, a relatively unacculturated hunter-gatherer-horticulturist tribe, similar differences in fertility distribution of both sexes are apparent. The data suggest that human populations contain statistically distinct subpopulations, with different reproductive strategies, suggesting the existence of complex interactions among human populations which are not evident from the study of individuals or groups.

  9. Analyzing a self-managed CHP system for greenhouse cultivation as a profitable way to reduce CO2-emissions

    International Nuclear Information System (INIS)

    Compernolle, Tine; Witters, Nele; Van Passel, Steven; Thewys, Theo

    2011-01-01

    To counter global warming, a transition to a low-carbon economy is needed. The greenhouse sector can contribute by installing Combined Heat and Power (CHP) systems, known for their excellent energy efficiency. Due to the recent European liberalization of the energy market, glass horticulturists have the opportunity to sell excess electricity to the market and by tailored policy and support measures, regional governments can fill the lack of technical and economic knowledge, causing initial resistance. This research investigates the economic and environmental opportunities using two detailed cases applying a self managed cogeneration system. The Net Present Value is calculated to investigate the economic feasibility. The Primary Energy Saving, the CO 2 Emission Reduction indicator and an Emission Balance are applied to quantify the environmental impact. The results demonstrate that a self-managed CHP system is economic viable and that CO 2 emissions are reduced.

  10. Gardening with Huntington's disease clients--creating a programme of winter activities.

    Science.gov (United States)

    Spring, Josephine Anne; Baker, Mark; Dauya, Loreane; Ewemade, Ivie; Marsh, Nicola; Patel, Prina; Scott, Adrienne; Stoy, Nicholas; Turner, Hannah; Viera, Marc; Will, Diana

    2011-01-01

    A programme of garden-related indoor activities was developed to sustain a gardening group for people with mid to late stage Huntington's disease during the winter. The activities were devised by the horticulturist, working empirically, involving the services occupational therapist, physiotherapist, occupational therapy art technician, computer room, recreation and leisure staff. The programme was strongly supported by the nursing and care staff. Feedback on the effectiveness of the activities was sought from the clients, team members and unit staff. The clients' interest in gardening was sustained by a multidisciplinary programme of indoor growing and using plant products in creative activities, computing and group projects. The clients enjoyed all activities except one that they said lacked contact with plants. The inexpensive programme of activities enabled creativity and self-expression, stimulated social contact and helped with therapeutic goals of the clients. In addition, it engaged the multi-disciplinary team and the unit staff, was practical and enhanced the environment.

  11. ECOLOGICAL APPROACHES IN THE ORGANIC AGRICULTURAL SYSTEM

    Directory of Open Access Journals (Sweden)

    Veselka Vlahova

    2015-09-01

    Full Text Available The permaculture includes landscape shaping, terrace formation, establishment of raised planes and hilly beds. Sepp Holzer’s permaculture has been practices since 1962, having its followers in Columbia, Thailand, Brazil, the USA and Scotland, etc. Important specifics of the Fukuoka method consists of the requirement that the agricultural farm is close to nature, without any attempts to conquer or improve it, whence the method’s name “natural”, i.e. real or natural. In his book entitled “The One-Straw Revolution” the author examines the issues of natural agriculture. The Biodynamic French Intensive method of vegetable gardening combines two gardening traditions: biodynamics, created in the 1920s by Rudolph Steiner, and French intensive gardening, a method practiced by 19th century farmers on the outskirts of Paris. British horticulturist Alan Chadwick bought these methods to the United States in the 1960s and coined the term biointensive. This style of organic gardening focuses on sustainable, high productivity using minimal space.

  12. Social learning in cooperative dilemmas.

    Science.gov (United States)

    Lamba, Shakti

    2014-07-22

    Helping is a cornerstone of social organization and commonplace in human societies. A major challenge for the evolutionary sciences is to explain how cooperation is maintained in large populations with high levels of migration, conditions under which cooperators can be exploited by selfish individuals. Cultural group selection models posit that such large-scale cooperation evolves via selection acting on populations among which behavioural variation is maintained by the cultural transmission of cooperative norms. These models assume that individuals acquire cooperative strategies via social learning. This assumption remains empirically untested. Here, I test this by investigating whether individuals employ conformist or payoff-biased learning in public goods games conducted in 14 villages of a forager-horticulturist society, the Pahari Korwa of India. Individuals did not show a clear tendency to conform or to be payoff-biased and are highly variable in their use of social learning. This variation is partly explained by both individual and village characteristics. The tendency to conform decreases and to be payoff-biased increases as the value of the modal contribution increases. These findings suggest that the use of social learning in cooperative dilemmas is contingent on individuals' circumstances and environments, and question the existence of stably transmitted cultural norms of cooperation. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  13. Exposure assessment using human biomonitoring for glyphosate and fluroxypyr users in amenity horticulture.

    Science.gov (United States)

    Connolly, Alison; Jones, Kate; Galea, Karen S; Basinas, Ioannis; Kenny, Laura; McGowan, Padraic; Coggins, Marie

    2017-08-01

    Pesticides and their potential adverse health effects are of great concern and there is a dearth of knowledge regarding occupational exposure to pesticides among amenity horticulturalists. This study aims to measure occupational exposures to amenity horticuturalists using pesticides containing the active ingredients, glyphosate and fluroxypyr by urinary biomonitoring. A total of 40 work tasks involving glyphosate and fluroxypyr were surveyed over the period of June - October 2015. Workers used a variety of pesticide application methods; manual knapsack sprayers, controlled droplet applicators, pressurised lance applicators and boom sprayers. Pesticide concentrations were measured in urine samples collected pre and post work tasks using liquid chromatography tandem mass spectrometry (LC-MS/MS). Differences in pesticide urinary concentrations pre and post work task, and across applications methods were analysed using paired t-tests and linear regression. Pesticide urinary concentrations were higher than those reported for environmental exposures and comparable to those reported in some agricultural studies. Log-transformed pesticide concentrations were statistically significantly higher in post-work samples compared to those in pre-work samples (paired t-test, p<0.001; for both μgL -1 and μmol/mol creatinine). Urinary pesticide concentrations in post-work samples had a geometric mean (geometric standard deviation) of 0.66 (1.11) μgL -1 for glyphosate and 0.29 (1.69) μgL -1 for fluroxypyr. Linear regression revealed a statistically significant positive association to exist between the time-interval between samples and the log-transformed adjusted (i.e. post- minus pre-task) pesticide urinary concentrations (β=0.0039; p<0.0001). Amenity horticulturists can be exposed to pesticides during tasks involving these products. Further research is required to evaluate routes of exposure among this occupational group. Crown Copyright © 2017. Published by Elsevier GmbH. All

  14. Horticulture in Portugal 1850-1900: The role of science and public utility in shaping knowledge.

    Science.gov (United States)

    Rodrigues, Ana Duarte; Simões, Ana

    2017-07-01

    In this paper, we address the emergence of horticultural practice, agents, spaces and institutions in the two urban settings of Lisbon and Porto, in Portugal, during the second half of the nineteenth century. We do so by following the networking activities of two players: the self-made horticulturist and entrepreneur José Marques Loureiro, who created, in Porto, a commercial horticultural establishment and founded the Journal of Practical Horticulture; and the agronomist Francisco Simões Margiochi, head of the gardens and green grounds department of the municipality, who created the first course on gardening and horticulture, and founded the Royal Horticultural Society, both in Lisbon. Their joint activities were aimed at establishing horticulture as an applied science and to cater simultaneously to an extended audience of citizens. They enable us to enrich the narratives on the emergence and development of horticulture in Europe by calling attention to the participation in circulatory extended networks of actors who are often absent from these accounts. Additionally, they allow a comparative assessment of the outcome of their actions at the national level, and to understand their results in terms consonant with recent historiographical trends on the co-construction of centres and peripheries. AML - Arquivo Municipal de Lisboa (Municipal Archive of Lisbon).; ANTT - Arquivo Nacional da Torre do Tombo (National Archives at Torre do Tombo).; AHCPL - Arquivo Histórico da Casa Pia de Lisboa (Historical Archive of the Casa Pia of Lisbon).; JHP - Jornal de Horticultura Practica (Journal of Practical Horticulture). Online at: http://www.fc.up.pt/fa/?p=nav&f=html.fbib-Periodico-oa&item=378 ; BSNHP - Boletim da Sociedade Nacional de Horticultura de Portugal (Bulletin of the National Society of Horticulture of Portugal).

  15. [Promissing role of probiotics in prevention of smoking-related diseases].

    Science.gov (United States)

    Hozyasz, Kamil K

    2008-01-01

    Humans are highly adapted to consuming probiotics. Trehalose ("mushroom" sugar) is probably an important reserve compound and stress-responsible metabolite (increases bile and gastric acid resistance) of probiotic bacteria's and trehalase activity, in contrast to lactase activity, is preserved in all human populations, even those not consuming mushrooms. Among traditional Melanesian horticulturists, of whom 4/5 are daily smokers, the diet is rich in pre- and probiotics and there is absence of cancer and cardiovascular disease. Indoor air pollution is an important cancer risk factor. Over thousands of years, the controlled use of fire for preparing meals has resulted in exposure to smoke pollution (biomass fuels produce up to 100 times more respirable particles compared to gas ovens). Simultaneously, up until the 20th century, the only commonly available and inexpensive way of preserving food was fermentation and drying. Probiotics may protect the detoxification function of the kidney and liver. Furthermore, it can be speculated that probiotics may help in adaptation to smoke pollution generated during cooking, heating but also tobacco smoking. Smoking is the most important lifestyle risk factor for bladder cancer and the consumption of probiotic foods reduces the risk of this cancer in humans. Probiotics may restore natural killer cell activity which is lowered in smokers. In one study it was observed that a diet supplemented with Lactobacillus plantarum could be also useful in the prevention of cardiovascular disease in smokers. There is no sufficient data from clinical trials to recommend the routine use of probiotics in prevention of smoking-related diseases. More research is needed to investigate the role of probiotics in this area.

  16. MDGC-MS analysis of essential oils from Protium heptaphyllum (Aubl. and their antifungal activity against Candida specie

    Directory of Open Access Journals (Sweden)

    M. MOBIN

    Full Text Available ABSTRACT Protium heptaphyllum is found in the Amazon region, and in various Brazilian states and South American countries. Also Known as almecega, it produces an oil resin used in traditional medicine as analgesic, anti-inflammatory, cicatrizant and expectorant, it is rich in pentacyclic triterpenes and essential oil. The main objective of this study was to analyze the chemical composition of P. heptaphyllumresin (OEPh over different extraction times and to evaluate their antifungal activity against Candida species, obtained from gardeners with onychomycosis, using the disk diffusion method. The OEPh was obtained by hydrodistillation and analyzed by Multidimensional Gas Chromatography coupled with Mass Spectrometry (MDGC / MS. Candida species were obtained from lesions on the nails of horticulturist from a community garden in the city of Teresina, Piauí, Brazil. The antifungal activity in concentrations of 1000 µg/L, 500 µg/L and 250 µg/L, PROTOCOL M44-A2 (CLSI 2009 OEPh was tested. The main constituents identified were: l-limonene, α-terpineol, p-cineol, o-cymene and α-phellandrene, however, its composition varies significantly with extraction time. All species, except C. rugosa, were inhibited with halo (≥ 14 mm at 1000 μg / L. C. krusei is naturally resistant to the drug fluconazole, but when tested with OEPh the clinical species (case 9 demonstrated sensitivity in three dilutions (halo ≤ 10 ≥ 14 and the standard strain was inhibited at concentration of 1000 μg/Lg / L (halo 14mm. A similar situation also occurred with the standard strain of C. parapsilosis (halo ≥ 11mm. OEPh has considerable antifungal activity, which merits further investigation for alternative clinical applications, since this species is widely distributed in our community, and it presents good yields, and also has important therapeutic applications.

  17. Oficios y artesanos medievales en el Monasterio leonés de Vega

    Directory of Open Access Journals (Sweden)

    Domínguez Sánchez, Santiago

    2013-12-01

    Full Text Available In this article is studied the presence of a great group of servants, officials and craftsmen in the Benedictine monastery of Vega, situated in the bank of the river Cea, who, with their work, were contributing to the maintenance of the monastery. The study centres in the centuries X and the XVth, and in it, departing exclusively from the documentary sources, there is analyzed and values the work of artisans and craftsmen dedicated to the pastoral and agricultural tasks (shepherds, horticulturists, farmers and millers, others related to the nourishment (confectioners, bakers, butlers, butchers, fishermen, cooks and charcoal-burners, the garment and the footwear (tailors, cobblers and launderers, the construction (stonecutters, carpenters, bricklayers and blacksmiths, the trade (shopkeepers, the hospitality (doormen and innkeepers, the control of the servants ("merinos" and butlers, or to other activities related to the law and the right (arbitrators, attorneys, executioners, notaries and auctioneers.En este artículo se estudia la presencia en el monasterio benedictino de Vega, sito en la ribera del río Cea, de un nutrido grupo de criados, oficiales y artesanos que, con su trabajo, colaboraban en pro del sostenimiento del monasterio. El estudio se centra en los siglos X y XV, y en él, partiendo exclusivamente de las fuentes documentales, se analiza y valora el trabajo de menestrales y artesanos dedicados a las tareas pastoriles y agrícolas (pastores, hortelanos, labradores y molineros, otras relacionadas con la alimentación (reposteros, panaderos, bodegueros, carniceros, pescadores, cocineros y carboneros, el vestido y el calzado (sastres, zapateros y lavanderos, la construcción (pedreros, carpinteros, albañiles y herreros, el comercio (tenderos, la hospitalidad (porteros, posaderos y albergueros, el control de los criados (merinos y mayordomos, o bien a otras actividades relacionadas con la ley y el derecho (jueces árbitros, procuradores

  18. Accelerator mass spectrometry and the prehistoric occupation of the coast of rio de janeiro - brazil

    International Nuclear Information System (INIS)

    Damasio Macario, K.; Anjos, R.M.; Gomes, P.R.S.; Facure, A.D.; Elmore, M.; Coimbra, M.; Padron, I.; Najjar, R.; Kneip, L.; Lima, T.A.; Buarque, A.; Barbosa, M.; Seda, P.

    2001-01-01

    -cultural system destabilization, from the study of the relation between fishermen-collectors group (builders of shell mounds) and horticulturist, ceramics manufacturers group. Another objective is to compare information from the this area to data available from the entire national territory in order to delimit the origin point of these groups and their expansion routes. The geographical identification of prehistoric routes depends exclusively on the relation between location/characterization of the archaeological sites and the radiocarbon dating

  19. Mutated genes as research tool

    International Nuclear Information System (INIS)

    1981-01-01

    Green plants are the ultimate source of all resources required for man's life, his food, his clothes, and almost all his energy requirements. Primitive prehistoric man could live from the abundance of nature surrounding him. Man today, dominating nature in terms of numbers and exploiting its limited resources, cannot exist without employing his intelligence to direct natural evolution. Plant sciences, therefore, are not a matter of curiosity but an essential requirement. From such considerations, the IAEA and FAO jointly organized a symposium to assess the value of mutation research for various kinds of plant science, which directly or indirectly might contribute to sustaining and improving crop production. The benefit through developing better cultivars that plant breeders can derive from using the additional genetic resources resulting from mutation induction has been assessed before at other FAO/IAEA meetings (Rome 1964, Pullman 1969, Ban 1974, Ibadan 1978) and is also monitored in the Mutation Breeding Newsletter, published by IAEA twice a year. Several hundred plant cultivars which carry economically important characters because their genes have been altered by ionizing radiation or other mutagens, are grown by farmers and horticulturists in many parts of the world. But the benefit derived from such mutant varieties is without any doubt surpassed by the contribution which mutation research has made towards the advancement of genetics. For this reason, a major part of the papers and discussions at the symposium dealt with the role induced-mutation research played in providing insight into gene action and gene interaction, the organization of genes in plant chromosomes in view of homology and homoeology, the evolutionary role of gene duplication and polyploidy, the relevance of gene blocks, the possibilities for chromosome engineering, the functioning of cytroplasmic inheritance and the genetic dynamics of populations. In discussing the evolutionary role of

  20. Nutrient uptake by greenhouse net melonAcúmulo de nutrientes e rendimento de óleo em plantas de girassol influenciados pelo vigor dos aquênios e pela densidade de semeadura

    Directory of Open Access Journals (Sweden)

    Silvana da Silva Cardoso

    2010-02-01

    Full Text Available For presenting more commercial value, the net melon (Cucumis melo L. var reticulatus Naud. has been an option of greenhouse planting for the horticulturists. This work was carried out in Piracicaba, Brazil with the aim of evaluating the nutrient uptake from this melon cultivated in greenhouse. To obtain the nutrients accumulation in the different stages of the plant development, plants were collected in the transplant day (seedling, in the vegetative stage, in the beginning of the flowering stage, in the beginning and in the middle of fruit production period and in the harvest period. It was verified that the greatest increase of nutrient uptake happened between the beginning of the flowering and the beginning of the fruit production. The greatest dry matter accumulation happened between the beginning of the fruit production and the middle of fruit production period. The decrescent order of nutrients accumulated in the above ground part of the plant was: potassium > nitrogen > calcium > magnesium > sulphur > phosphorus > iron > manganese > zinc > copper ~ boron. O objetivo do trabalho foi avaliar o acúmulo de nutrientes e o rendimento de óleo dos aquênios em plantas de girassol produzidas sob a influência do vigor dos aquênios e da densidade de semeadura. Para isto, foi instalado um experimento no campo experimental no município de Seropédica/RJ, em outubro de 2006, com três distintos lotes de aquênios de girassol cv Embrapa 122 V2000, classificados como de baixo, de médio e de alto vigor, sob duas densidades de semeadura (45.000 e 75.000 sementes ha-1. Aos 20, 60 e 100 dias após a semeadura (DAS, foram coletadas as plantas para avaliação da massa de matéria seca e do acúmulo de nitrogênio, de fósforo, de potássio e de cálcio, no caule, nas folhas e nos capítulos. Nas plantas coletadas aos 100 DAS, foi feita também a avaliação do rendimento de aquênios (kg ha-1, do teor de óleo e do rendimento de óleo (kg ha-1. Observou

  1. Evaluation of the Tolerance of Some Citrus Rootstocks to Citrus Nematode in Greenhouse (Tylenchulus semipenetrans

    Directory of Open Access Journals (Sweden)

    Y. Mohammad Alian

    2018-02-01

    to Tristeza and gummosis and identifying their resistance to citrus nematode, so planting of these rootstocks in the North of the country can be effective in managing citrus nematode in infected areas. In fact, investigating resistance of common rootstocks in the region and having access to resistance sources can be regarded as a method for sanitation of plants and as a result for controlling this nematode and increasing yield in the region. Also, the results of this survey can help horticulturists to introduce and produce appropriate rootstocks in the south of the country.

  2. Risk Evaluation of the Use of Green Gas in Dutch greenhouses; Risico-evaluatie toepassing Groen Gas in de Nederlandse Glastuinbouw

    Energy Technology Data Exchange (ETDEWEB)

    Van Dijk, C.J. [Plant Research International PRI, Wageningen (Netherlands); Dueck, Th.A. [Wageningen UR Glastuinbouw, Wageningen (Netherlands); Burgers, W. [Infomil, Den Haag (Netherlands)

    2009-01-15

    information is available to estimate the possible risks of the remaining components in biogas. The approach in this study represents a worst case scenario because in common practice biogas will be mixed in the existing natural gas network before distributing it to greenhouses. It should be noted that even now, the use of flue gas emitted from combined heat power engines burning natural gas can result in nitrogen oxide concentrations that exceed the effective risk concentration under certain conditions. These effective risk concentrations have in some cases already resulted in negative effects on the growth and production of some greenhouse crops. These risks are independent of the use of biogas as fuel for combined heat power engines. If Dutch horticulturists are to use biogas on a large scale, it is essential that the maximum permissible concentrations be reduced for hydrogen fluoride (by a factor 20), sulphur dioxide (factor 2) and possibly benzene as well (factor 1.7). This is necessary in order to prevent these components becoming a potential risk to greenhouse crops. In addition, more research is advocated on the phytotoxicity of components for which insufficient information is presently available for the estimation of possible risks. [Dutch] Groen Gas (biogas) afkomstig uit vergistings- en vergassingsinstallaties kan een bijdrage leveren aan de energievoorziening als vervanger van fossiel aardgas. Het ambitieniveau ligt op 50% aardgasvervanging in 2050. In de Nederlandse glastuinbouw worden momenteel hoofdzakelijk aardgasgestookte WKK-installaties gebruikt. De installaties leveren elektriciteit voor belichting en levering aan het net, warmte voor de kas en rookgassen voor kooldioxide (CO2) productie t.b.v. gewasgroei en -productie. De glastuinbouwsector wordt als een belangrijke speler gezien voor de afzet van biogas. Indien op grote schaal geproduceerd biogas direct of na toevoeging aan het bestaande aardgasnet als brandstof wordt gebruikt voor installaties in de