Espermidina exógena atenua os efeitos do NaCl na germinação e crescimento inicial de leguminosas forrageiras

Abstract

RESUMO -Objetivou-se nesse estudo avaliar o papel atenuador da espermidina exógena sobre a germinação, vigor de sementes e crescimento de plântulas de cultivares das forrageiras alfafa, guandu e labe-labe submetidas ao estresse salino. A semeadura foi realizada em caixas de plástico tipo "gerbox" forradas com papel de filtro umedecidos com soluções salinas nas concentrações de 0, 20, 40, 60, 80 e 120 mM de NaCl contendo 0 ou 0,5 mM de espermidina. O delineamento experimental foi inteiramente casualizado em esquema fatorial 3 x 6 x 2 (forrageiras x salinidade x espermidina) com cinco repetições de 25 sementes. As avaliações da germinação foram realizadas no quarto e décimo dias, juntamente com o índice de velocidade de germinação (IVG), avaliado até o nono dia após a semeadura. Determinou-se a concentração salina que reduz em 50% a germinação e a massa seca da parte aérea e raiz no décimo dia após a semeadura. A aplicação de espermidina exógena proporcionou maior acúmulo de massa seca das raízes de labe-labe cv. Rongai, além de ter possibilitado a germinação de 50% das sementes de guandu cv. Caqui até a concentração salina de 72,09 mM de NaCl, assim como maior IVG nas sementes das leguminosas alfafa cv. Crioula e labe-labe cv. Rongai. Exogenous spermidine alleviates the effects of NaCl on the germination and initial growth of forage legumes ABSTRACT -The objective of this study was to evaluate the mitigating role of exogenous spermidine on the seed germination, seed vigor and seedling growth of alfalfa forage cultivars, pigeon pea and lablab subjected to salt stress. The seeds were sown in plastic gerboxes lined with filter paper moistened with saline solutions at concentrations of 0, 20, 40, 60, 80 and 120 mM NaCl containing 0 or 0.5 mM spermidine. The experimental design was a completely randomized factorial 3 x 6 x 2 (forage x salinity x spermidine) with five replicates of 25 seeds. Germination was evaluated on the fourth and tenth days, along with the germination speed index, measured until the ninth day after sowing. The salt concentration had reduced germination and the dry weight of shoot and root by 50% on the tenth day after sowing. The application of exogenous spermidine resulted in a greater dry root weight of lablab cv. Rongai, 50% germination of pigeon pea seeds cv. Caqui at the salt concentration of 72.09 mM NaCl, and a higher GSI for alfalfa cv. Crioula and lablab cv. Rongai seeds.

Vigour in maize seeds: influence on seedling development under conditions of salt stress

“…Como exemplos podem ser citados os dados obtidos para milho pipoca (MOTERLE et al, 2006), soja transgênica e convencional , leguminosas forrageiras (MELLONI et al, 2012), bem como nabiça e fedegoso (PEREIRA et al, 2014).…”

Physiological potential of soybean seeds under hypoxia and salinity stress

“…As for germination, obtained as a function of different osmotic potentials (Figure 3A), the percentage of normal seedlings decreased for the three cultivars evaluated. Significant reductions in seed germination were also observed in the study of Nunes et al (2009), , Melloni et al (2012), and Pereira et al (2014). These results prove the harmful effects of salinity stress due to its osmotic or ionic impact, impairing the absorption of water or favoring the entry of ions into the cells (Braccini et al, 1996).…”

“…The results suggest that the toxic effects of salts caused inhibition of germination. These results have been attributed to the reduction of the amount of water absorbed by the seeds in saline medium, with reduction of the osmotic potential of the solutions (Braccini et al, 1996;Melloni et al, 2012).…”

Pretreatment of forage legumes under moderate salinity with exogenous salicylic acid or spermidine

“…The same results in lablab and in another pigeonpea cultivar (cv. Caqui) were found by Melloni et al (2012), who verified that 0.5 mM Spd caused a significant decrease in seed germination under salt stress (20 -120 mM). However, these authors showed that at this decrease was smaller than the one observed in treatments with no Spd, indicating that salt stress could mitigate the effect of this polyamine.…”