Ultrastructural and biochemical changes induced by salt stress in jatropha curcas seeds during germination and seedling development

Jatropha curcas L. is a multipurpose species of the Euphorbiaceae family that is widespread in arid and semiarid regions. This study investigated the ultrastructural and biochemical changes induced by salt stress during J. curcas seed germination and seedling development. Salt stress negatively affected seed germination and increased Na+ and Cl– contents in endosperms and embryo-axis. Lipids represented the most abundant reserves (64% of the quiescent seed dry mass), and their levels were strongly decreased at 8 days after imbibition (DAI) under salinity stress. Proteins were the second most important reserve (21.3%), and their levels were also reduced under salt stress conditions. Starch showed a transient increase at 5 DAI under control conditions, which was correlated with intense lipid mobilisation during this period. Non-reducing sugars and free amino acids were increased in control seeds compared with quiescent seeds, whereas under the salt-stress conditions, minimal changes were observed. In addition, cytochemical and ultrastructural analyses confirmed greater alterations in the cellular reserves of seeds that had been germinated under NaCl stress conditions. Salt stress promoted delays in protein and lipid mobilisation and induced ultrastructural changes in salt-stressed endosperm cells, consistent with delayed protein and oil body degradation4286587

Produção e fisiologia de plantas de cajueiro anão precoce sob condições de sequeiro e irrigado

A exploração do cajueiro sob condições de irrigação tem-se mostrado bastante promissora, especialmente no estado do Ceará, porém a resposta dessa cultura ao regime hídrico depende do genótipo. Objetivouse, com este trabalho, comparar respostas fisiológicas e bioquímicas (teores de solutos orgânicos e inorgânicos e trocas gasosas), tal como a produtividade de plantas de cajueiro anão precoce (Anacardium occidentale L.) sob dois regimes hídricos (sequeiro e irrigado). O experimento foi conduzido no Campo Experimental da Embrapa Agroindústria Tropical, em Pacajus CE, no período de agosto de 2006 a janeiro de 2007. As plantas foram submetidas a dois tratamentos: um sem irrigação e outro com água de poço com condutividade elétrica (CEa) de 0,5 dS m-1. As respostas fisiológicas foram avaliadas mensalmente e os dados de produção foram obtidos no período de novembro a janeiro. Os teores foliares de N-aminossolúveis e prolina foram mais elevados nas plantas cultivadas em condições de sequeiro do que naquelas irrigadas, porém não houve diferença significativa entre os tratamentos para as trocas gasosas, teores de carboidratos solúveis, K+, Na+ e Cl-. Entretanto, com exceção da fotossíntese, todas as variáveis estudadas apresentaram alterações com as épocas de coleta. Apesar das alterações em algumas variáveis ao longo do experimento, a produtividade das plantas não foi afetada pelo estresse hídrico

Influência do acúmulo e distribuição de íons sobre a aclimatação de plantas de sorgo e feijão-de-corda, ao estresse salino Influence of accumulation and distribution of ions on acclimation of sorghum and cowpea plants to salt stress

Neste trabalho, estudou-se a influência do acúmulo e distribuição de íons na parte aérea de plantas de feijão-de-corda e de sorgo na aclimatação ao estresse. As plantas foram submetidas a dois tratamentos: ao controle (solução nutritiva sem a adição de NaCl ) e ao salino (solução nutritiva, contendo NaCl a 75 mM). O sorgo mostrou-se mais tolerante ao estresse salino que o feijão-de-corda, notadamente após o 10º dia de estresse. O feijão-de-corda apresentou maior acúmulo de íons na parte aérea que o sorgo, que se comportou como planta com boa capacidade de exclusão e retenção de íons. O maior acúmulo de íons potencialmente tóxicos nos limbos foliares das plantas de feijão-de-corda, contribuiu para o aumento da suculência. Embora a exclusão ou retenção de íons em plantas de sorgo submetidas a estresse tenha produzido certo grau de desidratação foliar, pareceu tratar-se de um mecanismo de aclimatação ao estresse muito mais eficiente que o aumento da suculência resultante do acúmulo excessivo de íons nos tecidos foliares de plantas de feijão-de-corda.<br>In this paper the influence of accumulation and distribution of ions in plant shoots on acclimation to salt stress of cowpea and sorghum plants was studied. The plants were subjected to two treatments: control (nutrient solution without addition of NaCl) and saline (nutrient solution containing 75 mM of NaCl). Sorghum showed a higher tolerance to salt stress in comparison to cowpea, mainly after the 10th day of stress. Cowpea showed higher shoot ion accumulation than sorghum, which behaved as a plant with good capacity of ion exclusion. The higher accumulation of potentially toxic ions in cowpea leaves contributed to the increase in leaf succulence. Although the exclusion or retention of ions observed in stressed plants of sorghum had produced a certain degree of leaf dehydration, it seemed to be a much more efficient mechanism of stress acclimation than the excessive accumulation of ions in leaf tissues of cowpea plants

Nitrate: ammonium nutrition alleviates detrimental effects of salinity by enhancing photosystem II efficiency in sorghum plants

ABSTRACT This study was carried out to evaluate if replacement of nitrate (NO3-) by ammonium (NH4+) in the growth medium prevents the damage in the photosystem II (PSII) efficiency and degradation of photosynthetic pigments caused by saline stress in sorghum plants. Sorghum bicolor plants were cultivated in nutrient solutions containing different NO3-:NH4+ ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at a final concentration of 5.0 mM. Salinity was imposed by adding NaCl at 75 mM in the growth medium; and the analysis were performed after ten days of salt stress. The most striking effects of nitrogen regime were observed in plants supplied with equal amounts of NO3-: NH4+ (50:50). Under salt stress, 50:50-grown plants displayed an increase in the photosystem II maximum efficiency (Fv/Fm), which was associated with a lower non-photochemical quenching (NPQ). The superior performance of salt-stressed plants grown in 50:50 ratio was indicated by a higher effective quantum yield of PSII (ΦPSII) and electron transport rate (ETR), as well as increased chlorophyll b and anthocyanins. In conclusion, nitrogen nutrition with same amounts of nitrate and ammonium avoids the degradation of photosynthetic pigments and allows higher PSII efficiency in salt-stressed sorghum plants