VIABILIDADE E ATIVIDADE ANTIOXIDANTE DE SEMENTES DE GENÓTIPOS DE FEIJÃO-MIÚDO SUBMETIDOS AO ESTRESSE SALINO.

This study aimed to evaluate the effect of different salt concentrations on the germination, initial biomass and oxidative stress of four cowpea genotypes, commonly grown in the São José do Norte region, RS. The seeds of the genotypes Amendoim, Mosqueado, Baio and Preto were planted in rolls of "germitest" paper, soaked in a solution of sodium chloride at concentrations of zero, 50, 100, 150 and 200 mM and placed to germinate at a constant temperature of 25 oC. Variables studied were: germination, first count, length and dry mass of the shoots and roots of seedlings, lipid peroxidation and the specific activity of superoxide dismutase, ascorbate peroxidase and catalase. Increasing salt concentration adversely affected seed germination and also the first count of the four cowpea genotypes for the 100 mM salt treatment. Joint analysis of the regression curves for the growth parameters showed the same tendency for the four genotypes, with a significant growth reduction as salt stress increased. Stress effects were also evident from increased lipid peroxidation in the 200 mM salt treatment, followed by reduced enzyme antioxidant activity, since in the intermediate salt concentrations, the antioxidant enzymes efficiently eliminated reactive oxygen species (ROS), preventing oxidative stress. These results indicate that, at intermediate doses of salt, there was good initial development of the four cowpea genotypes and the best response was observed in the Amendoim genotype. [ABSTRACT FROM AUTHOR]