No description available.

No description available.

No description available.

No description available.

Extensive land areas in arid and semi-arid regions contain excessive amounts of salt which inhibit or prevent the growth of desirable crop plants. This problem is increasing with the development of extensive irrigation projects. The future of irrigation agriculture will depend upon the development and the utilization of means of (1) preventing salt accumulation, (2) reclaiming salted soils. and (3) making the best use of those soils which by reason of drainage problems, soil texture and permeability, poor quality irrigation water, etc. are unsuited for economic reclamation. The utilization of land that is not feasible to completely reclaim, at least under present economic conditions, will depend upon the selection, development, and use of varieties and strains of crop plants which will produce economically under such conditions. The objectives of this research are to (1) test on a preliminary basis the salt tolerance of a number of promising crop plant materials. (2) observe the effect of salt upon plant behavior and growth, and (3) develop various methods of evaluating plant materials for salt tolerance.

No description available.

Widespread antibiotic resistance is a major public health concern, and plants represent an emerging antibiotic exposure route. Recent studies indicate that crop plants fertilized with antibiotic-laden animal manure accumulate antibiotics, however, the molecular mechanisms of antibiotic entry and subcellular partitioning within plant cells remain unknown. Here we report that mutations in the Arabidopsis locus Multiple Antibiotic Resistance (MAR1) confer resistance, while MAR1 overexpression causes hypersensitivity to multiple aminoglycoside antibiotics. Resistance is highly specific for aminoglycosides and does not extend to antibiotics of other classes, including the aminocyclitol, spectinomycin. Yeast expressing MAR1 are hypersensitive to the aminoglycoside, G418, but not to chloramphenicol or cycloheximide. MAR1 encodes a protein with 11 putative transmembrane domains with low similarity to ferroportin1 from Danio rerio. A MAR1:YFP fusion protein localizes to the chloroplast, and chloroplasts from plants overexpressing MAR1 accumulate more of the aminoglycoside, gentamicin, while mar1-1 mutant chloroplasts accumulate less than wild type. MAR1 overexpression lines are slightly chlorotic, and this chlorosis is rescued by application of exogenous iron. MAR1 expression is also downregulated by low iron. Taken together, these data suggest that MAR1 is a plastid transporter that is likely to be involved in cellular iron homeostasis, and allows opportunistic entry of multiple antibiotics into the chloroplast. mar1 mutants represent an interesting example of plant antibiotic resistance that is based on the restriction of antibiotic entry into a subcellular compartment. Knowledge about this process – and other processes of antibiotic entry – could enable the production of crop plants that are incapable of antibiotic accumulation, aid in development of phytoremediation strategies for decontamination of water and soils polluted with antibiotics, and further the development of new plant-based molecular markers. The work described here also contributes to our understanding of how plants interact with the antibiotics they encounter, both in the laboratory (where aminoglycosides such as kanamycin are used heavily to select for transgenics) and in the natural environment. / text

Com o objetivo de melhorar o desempenho de culturas agrícolas, a utilização de extratos de algas tem aumentado, principalmente por ser uma alternativa ao uso de fertilizantes e por ser ecologicamente correta. A alga marinha Ascophyllum nodosum destaca-se dentre as espécies comumente empregadas para esta finalidade, e tem sido muito estudada por suas propriedades que incluem desde a promoção de crescimento vegetal ao uso na alimentação humana e animal. Numerosos estudos têm revelado vários efeitos benéficos da aplicação de extratos de algas em plantas, tais como a precocidade germinativa de sementes e de seu estabelecimento, melhoria do desempenho e da produtividade vegetal e elevada resistência a estresses bióticos e abióticos. Múltiplos processos fisiológicos, bioquímicos e genéticos estão envolvidos nas respostas dos vegetais e os efeitos observados a partir das aplicações podem ser diretos ou indiretos. Entretanto, os mecanismos de ação do extrato de A. nodosum ainda são pouco conhecidos e a sua elucidação é importante para a elaboração de estratégias que favoreçam o aumento da produtividade vegetal. Deste modo, torna-se relevante o estudo dos efeitos do extrato de alga sobre a fisiologia do crescimento, desenvolvimento e produtividade de espécies utilizadas em grandes culturas. O milho, a soja, o trigo e o feijão figuram entre as 10 culturas com maiores áreas de cultivo e volumes de produção no Brasil. Todas possuem múltiplas utilidades, alcançando relevância econômica e social não somente para este país, como também para o mundo, e por isso foram escolhidas para este estudo. / Aiming to improve the crop performance, the use of seaweed extracts has increased mainly because it is an alternative to the use of fertilizers and for being environmentally friendly. The seaweed Ascophyllum nodosum stands out among the species commonly employed for this purpose, and has been widely studied for its properties, which provide the plant growth as well as food for human and animals. Many studies have shown several beneficial effects of seaweed extracts in plants, such as the early germination of seeds and their establishment, improving the crop performance and productivity and a high resistance to biotic and abiotic stresses. Multiple physiological processes, biochemical and genetic factors are involved in the plant responses and the effects observed from applications can be direct or indirect. However, the action mechanisms of the A. nodosum extract are still poorly understood and their elucidation is important to develop strategies that provide higher plant productivity. Thus, it is important to study the seaweed extract effects on the physiology of the growth, development and yield of species used in crops. Corn, soybean, wheat and bean were chosen for this study due to their multiple uses and for being among the 10 crops that have the largest areas of cultivation and production volume in Brazil; achieving social and economic relevance not only for this country but also for the world.

Com o objetivo de melhorar o desempenho de culturas agrícolas, a utilização de extratos de algas tem aumentado, principalmente por ser uma alternativa ao uso de fertilizantes e por ser ecologicamente correta. A alga marinha Ascophyllum nodosum destaca-se dentre as espécies comumente empregadas para esta finalidade, e tem sido muito estudada por suas propriedades que incluem desde a promoção de crescimento vegetal ao uso na alimentação humana e animal. Numerosos estudos têm revelado vários efeitos benéficos da aplicação de extratos de algas em plantas, tais como a precocidade germinativa de sementes e de seu estabelecimento, melhoria do desempenho e da produtividade vegetal e elevada resistência a estresses bióticos e abióticos. Múltiplos processos fisiológicos, bioquímicos e genéticos estão envolvidos nas respostas dos vegetais e os efeitos observados a partir das aplicações podem ser diretos ou indiretos. Entretanto, os mecanismos de ação do extrato de A. nodosum ainda são pouco conhecidos e a sua elucidação é importante para a elaboração de estratégias que favoreçam o aumento da produtividade vegetal. Deste modo, torna-se relevante o estudo dos efeitos do extrato de alga sobre a fisiologia do crescimento, desenvolvimento e produtividade de espécies utilizadas em grandes culturas. O milho, a soja, o trigo e o feijão figuram entre as 10 culturas com maiores áreas de cultivo e volumes de produção no Brasil. Todas possuem múltiplas utilidades, alcançando relevância econômica e social não somente para este país, como também para o mundo, e por isso foram escolhidas para este estudo. / Aiming to improve the crop performance, the use of seaweed extracts has increased mainly because it is an alternative to the use of fertilizers and for being environmentally friendly. The seaweed Ascophyllum nodosum stands out among the species commonly employed for this purpose, and has been widely studied for its properties, which provide the plant growth as well as food for human and animals. Many studies have shown several beneficial effects of seaweed extracts in plants, such as the early germination of seeds and their establishment, improving the crop performance and productivity and a high resistance to biotic and abiotic stresses. Multiple physiological processes, biochemical and genetic factors are involved in the plant responses and the effects observed from applications can be direct or indirect. However, the action mechanisms of the A. nodosum extract are still poorly understood and their elucidation is important to develop strategies that provide higher plant productivity. Thus, it is important to study the seaweed extract effects on the physiology of the growth, development and yield of species used in crops. Corn, soybean, wheat and bean were chosen for this study due to their multiple uses and for being among the 10 crops that have the largest areas of cultivation and production volume in Brazil; achieving social and economic relevance not only for this country but also for the world.

In the literature on plant respiration, there are two viewpoints concerning the source of respiratory control: supply (photosynthate availability) or demand (temperature dependent) limitations. While different studies indicate the primary dependency for respiration is either the supply or demand side, the two paradigms cannot both be true. The relative importance of each paradigm may depend on a number of factors including period of time during which respiration is measured, phase of plant development, environmental conditions, and species. Studies were performed using continuous CO2 gas-exchange instrumentation to monitor short- and long-term changes in whole canopies of lettuce, tomato, soybean, and rice in response to changes in light and temperature during vegetative growth. Respiration in all crops was less sensitive to temperature than previously reported. This is likely due to large amounts of temperature-insensitive growth respiration as a fraction of total respiration during early growth. Carbon use efficiency (CUE) decreased with warm night temperatures, but the change was too small to decrease the final dry mass or carbon gain after night temperatures decreased. Canopies with constant day/night temperature had the same CUE, in elevated CO2 (1,200 μmol moJ- 1), regardless of temperature. In ambient CO2 (400 μmol mol-1), CUE decreased significantly when temperatures were above 32C. Applying shade initially decreased CUE because of low photosynthesis and high respiration. After about 12 days, canopies acclimated, based on recovery of CUE. Different species acclimated to shade to different extents, but no interaction was evident between light and shade stress. These data were used to predict changes in photosynthesis, respiration, and carbon use efficiency given light, temperature, and CO2 concentrations.