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This study was conducted with the objective of testing the hypothesis that tomato fruits from organic farming accumulate more nutritional compounds, such as phenolics and vitamin C as a consequence of the stressing conditions associated with farming system. Growth was reduced in fruits from organic farming while titratable acidity, the soluble solids content and the concentrations in vitamin C were respectively +29%, +57% and +55% higher at the stage of commercial maturity. At that time, the total phenolic content was +139% higher than in the fruits from conventional farming which seems consistent with the more than two times higher activity of phenylalanine ammonia lyase (PAL) we observed throughout fruit development in fruits from organic farming. Cell membrane lipid peroxidation (LPO) degree was 60% higher in organic tomatoes. SOD activity was also dramatically higher in the fruits from organic farming. Taken together, our observations suggest that tomato fruits from organic farming experienced stressing conditions that resulted in oxidative stress and the accumulation of higher concentrations of soluble solids as sugars and other compounds contributing to fruit nutritional quality such as vitamin C and phenolic compounds.

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Additional information is available at the end of the chapter http://dx.doi.org/10.5772/54223. Introduction "biotic stress limits crop productivity [ ], and plays a major role in determining the distribution of plant species across different types of environments. "biotic stress and its effects on plants in both natural and agricultural settings is a topic that is receiving increasing attention because of the potential impacts of climate change on rainfall patterns and temperature extremes, salinization of agricultural lands by irrigation, and the overall need to maintain or increase agricultural productivity on marginal lands. In the field, a plant may experience several distinct abiotic stresses either concurrently or at different times through the growing season [ ].In reference [ ] are showed some common examples of the abiotic stresses a plant may encounter which include a decreased availability of water, extremes of temperature including freezing, decreased availability of essential nutrients from the soil or conversely the buildup of toxic ions during salt stress , excess light especially when photosynthesis is restricted or increased hardness of the soil that restricts root growth.In the face of a global scarcity of water resources and the increased salinization of soil and water, abiotic stress is already a major limiting factor in plant growth and will soon become even more severe as desertification covers more and more of the world's terrestrial area. Plants are often subjected to periods of soil and atmospheric water deficits during their life cycle. Moreover, the faster-than-predicted change in global climate [ ] and the different available scenarios for climate change suggest an increase in aridity for the semiarid regions of the globe. Together with overpopulation, this will lead to an overexploitation of water resources for agriculture purposes and increased constraints on plant growth and survival aid, therefore, on realizing crop yield potential [ ]. Thus, if a single abiotic stress is to be identified as the most common in limiting the growth of crops worldwide, it most probably is low water supply [ ].Like the water stress, salinity is one of the major severe abiotic factors affecting crop growth and productivity [ ]. Salt s negative effects on plant growth have initially been associated with the osmotic stress component caused by decreases in soil water potential and, consequently, restriction of water uptake by roots.The literature shows that drought and salinity are already widespread in many regions. Therefore, in reference [ ] the authors have presented that in world where population growth exceeds food supply, agricultural and plant biotechnologies aimed at overcoming severe environmental stresses need to be fully implemented. . . Plant stress definitionsThe term stress is most often used subjectively and with various meanings. The physiological definition and appropriate term for stress are referenced as responses to different situations. The flexibility of normal metabolism allows the...

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Cowpea is widely cultivated in arid and semi‐arid regions of the world where salinity is a major environmental stress that limits crop productivity. The effects of moderate salinity on growth and photosynthesis were examined during the vegetative phase of two cowpea cultivars previously classified as salt‐tolerant (Pitiúba) and salt‐sensitive (TVu). Two salt treatments (0 and 75 mm NaCl) were applied to 10‐day‐old plants grown in nutrient solution for 24 days. Salt stress caused decreases (59 % in Pitiúba and 72 % in TVu) in biomass accumulation at the end of the experiment. Photosynthetic rates per unit leaf mass, but not per unit leaf area, were remarkably impaired, particularly in TVu. This response was unlikely to have resulted from stomatal or photochemical constraints. Differences in salt tolerance between cultivars were unrelated to (i) variant patterns of Cl− and K+ tissue concentration, (ii) contrasting leaf water relations, or (iii) changes in relative growth rate and net assimilation rate. The relative advantage of Pitiúba over TVu under salt stress was primarily associated with (i) restricted Na+ accumulation in leaves paralleling an absolute increase in Na+ concentration in roots at early stages of salt treatment and (ii) improved leaf area (resulting from a larger leaf area ratio coupled with a larger leaf mass fraction and larger specific leaf area) and photosynthetic rates per unit leaf mass. Overall, these responses would allow greater whole‐plant carbon gain, thus contributing to a better agronomic performance of salt‐tolerant cowpea cultivars in salinity‐prone regions.

The cashew (Anacardium occidentale L.) is an important crop for semi-arid agriculture and contributes to the social and economical development of several world regions, including the northeast of Brazil. In spite of its importance, very few studies aim to understand the effects of abiotic stresses on the development and yield of the cashew. This review covers the research on cashew ecophysiology, with emphasis on the effects of water and salt stress on its development, mineral nutrition and gas exchange processes. The results presented here were obtained at different plant growth stages and under different environmental conditions of soil and climate. The ecophysiological significance of this information is also discussed. Key words: Anacardium occidentale, development, salt stress, water deficit Fisiologia do cajueiro cultivado sob condições adversas. O cajueiro (Anacardium occidentale L.) é uma cultura de grande importância para a agricultura de regiões semi-áridas, contribuindo para o desenvolvimento sócio-econômico de diversas regiões do mundo, incluindo a região nordeste do Brasil. Apesar de sua importância, poucos são os estudos visando à compreensão dos efeitos dos fatores abióticos sobre o desenvolvimento e a produtividade dessa cultura. Nesta revisão, são apresentadas informações científicas sobre a ecofisiologia do cajueiro, dando ênfase aos efeitos dos estresses hídrico e salino sobre os processos de desenvolvimento, nutrição mineral e trocas gasosas. Os resultados apresentados foram obtidos em experimentos com plantas em diferentes estádios de desenvolvimento e sob diferentes condições de solo e clima, de modo que essa complexidade é também discutida no texto. Palavras-chave: Anacardium occidentale, desenvolvimento, estresse hídrico, estresse salino

Seeds from eight different maize genotypes (BR3123, BR5004, BR5011, BR5026, BR5033, CMS50, D766 and ICI8447) were sown in vermiculite, and after germination they were transplanted into nutrient solution or nutrient solution containing 100 mmol.L -1 of NaCl and placed in a greenhouse. During the experimental period plant growth (dry matter, shoot to root dry mass ratio, leaf area, relative growth rate, and net assimilation rate), leaf temperature, stomatal conductance, transpiration, predawn water potential, sodium, potassium, soluble amino acids and soluble carbohydrate contents were determined in both control and salt stressed plants of all genotypes studied. Salt stress reduced plant growth of all genotypes but the genotypes BR5033 and BR5011 were characterized as the most salt-tolerant and salt-sensitive, respectively. Stomatal response of the salt-tolerant genotype was not affected by salinity. Among the studied parameters, shoot to root dry mass ratio, leaf sodium content and leaf soluble organic solute content showed no relation with salt tolerance, i.e., they could not be considered as good morpho-physiological markers for maize salt tolerance. In contrast, sodium and soluble organic solutes accumulation in the roots as a result of salt stress appeared to play an important role in the acclimation to salt stress of the maize genotypes studied, suggesting that they could be used as physiological markers during the screening for salt tolerance.Keywords: growth analysis; osmoregulation; salinity; transpiration; Zea mays, water relations;.Efeito do estresse salino sobre o crescimento, resposta estomática e acúmulo de solutos em diferentes genótipos de milho: Sementes de oito genótipos de milho (BR3123, BR5004, BR5011, BR5026, BR5033, CMS50, D766 e ICI8447) foram semeadas em vermiculita e, após a germinação, transplantadas para vasos contendo solução nutritiva ou solução nutritiva com 100 mmol.L -1 de NaCl, em casa de vegetação. Durante o período experimental avaliaram-se, em plantas de todos os genótipos, sob condições de controle e estresse salino, os seguintes parâmetros: crescimento (matéria seca, relação de matéria seca parte aérea/raiz, área foliar, taxa de crescimento relativo e taxa de assimilação líquida), temperatura foliar, condutância estomática, transpiração, potencial hídrico antemanhã e teores de sódio, potássio, aminoácidos solúveis e carboidratos solúveis. O estresse salino reduziu o crescimento das plantas de todos os genótipos, sendo o BR5033 e o BR5011 caracterizados como tolerante e sensível ao estresse salino respectivamente. A resposta estomática do genótipo tolerante não foi influenciada pela salinidade. Entre os parâmetros estudados, a relação de matéria seca parte aérea/raiz e os teores de sódio e de solutos orgânicos nas folhas não mostraram relação com a tolerância à salinidade, isto é, não foram considerados bons marcadores morfo-fisiológicos para a tolerância à salinidade em milho. Em contraste, os teores de sódio e de solutos orgânicos nas raízes mostraram desempenhar um important...