Influência do acúmulo e distribuição de íons sobre a aclimatação de plantas de sorgo e feijão-de-corda, ao estresse salino

Abstract

RESUMONeste 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 10 o 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. Palavras-chave: salinidade, Vigna unguiculata, Sorghum bicolor, tolerância ao estresse salinoInfluence of accumulation and distribution of ions on acclimation of sorghum and cowpea plants to salt stress ABSTRACT 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 10 th 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.

Physiological and ionic changes in dwarf coconut seedlings irrigated with saline water

“…The similarity of the responses observed for the concentrations of Na + and Cl -, and of organic solutes, in both shoots and roots of coconut, suggests that the increase in the accumulation of organic solutes in the leaflets is associated with the increments in the contents of potentially toxic elements, corroborating the results of Trindade et al (2006) for sorghum and cowpea. However, the increase in the contents of these solutes in roots, especially soluble amino-N and carbohydrates, and the retention of Na + in roots with increased water salinity, when compared to the same parameters in leaflets, suggest that the root system plays an important role in the tolerance to salt stress in coconut seedlings.…”

“…The increase in the contents of soluble amino-N, carbohydrates and proline in the roots of coconut seedlings, also observed in other studies (Lacerda et al, 2003;Trindade et al, 2006;Mendes et al, 2011;Cunha et al, 2013), suggests that these solutes may be contributing to the osmotic adjustment of the root cells, decreasing the osmotic potential of subcellular compartments, or may be associated with other functions of protection against the damages caused by salt stress. According to Praxedes et al (2009) in the cowpea crop (Vigna unguiculata (L.) Walp), the increase in the accumulation of proline is a mechanism of protection against excess of salts.…”

“…The greatest accumulation of potentially toxic ions (particularly Na + and Cl -) in the leaf tissues of glycophytes is correlated with the sensitivity to salt stress (Trindade et al, 2006). In the present study, however, there was a high T , MT Figure 1.…”

“…In spite of that, there were no symptoms of Cl -toxicity, which can be associated with the functions of this element in coconut plants. It is important to emphasize that the contents of ions in the shoots, in the present study, represent the mean of the contents in the leaf blades, petioles and rachis, which suggests the possibility of compartmentalization in these tissues, as observed in cowpea and sorghum (Trindade et al, 2006;Aquino et al, 2007).…”

Temperaturas elevadas afetam a distribuição de íons em plantas de feijão caupi pré-tratadas com NaCl1

“…Esses resultados são bons indicativos da capacidade dessa espécie de reter parte dos íons potencialmente tóxicos, em especial o Na + no sistema radicular evitando, assim, seu excesso nos tecidos fotossintetizantes (Trindade et al, 2006 Inversamente, as concentrações de K + foram reduzidas em plantas pré-tratadas com NaCl e expostas a altas temperaturas em comparação com as referências em todos os órgãos analisados (Figura 2). No tratamento de calor mais severo e sob condições salinas, as concentrações do íon foram reduzidas de 8, 40 e 36% em folhas, caules e raízes, respectivamente, em comparação com as plantas submetidas a 27 ºC e sem NaCl (condição referência) (Figura 2A; B e C).…”