Susceptibility to weathering damage and oxidative stress on soybean seeds with different lignin contents in the seed coat

Abstract

Abstract: This study aimed at evaluating the relationship among lignin content in the seed coat of soybean seeds with tolerance to weathering damage and oxidative stress. Four soybean cultivars (CD 208, CD 215, CD 202 and BRS 184), with lignin contents in the seed coat of 4.2, 2.6, 2.0 and 1.7%, respectively, were used. Seeds were subjected to deterioration by moisture, through artificially simulated rains. Pods of all cultivars were subjected to irrigation by constant sprinkling during 4 hours, and then dried in oven, set at 35 °C, for 37 hours; repeating twice such procedure. After these treatments seeds were subjected to tests and then compared to the control. Tests performed were: germination, accelerated aging and tetrazolium test; thereby quantifying the occurrence of damages by weathering damage. The activity of enzymes superoxide dismutase and guaiacol peroxidase was measured; and the lipid peroxidation was assessed. Soybean cultivars CD 208 and CD 215, with higher lignin content in the seed coat, were less susceptible to weathering damage. Seeds of cultivar CD 208 have also presented lower oxidative stress, when subjected to weathering damage stress.Resumo: O estudo teve como objetivo avaliar a relação entre o teor de lignina no tegumento de sementes de soja com tolerância à deterioração por umidade e ao estresse oxidativo. Foram utilizadas quatro cultivares de soja: CD 208, CD 215, CD 202 e BRS 184, com teores de lignina no tegumento de 4,2; 2,6; 2,0 e 1,7%, respectivamente. As sementes foram submetidas a uma deterioração por umidade através de chuvas simuladas (4 horas), e, posteriormente, secas em estufa (35 °C), por 37 horas, totalizando dois ciclos de umedecimento e secagem. Foram realizados os testes: germinação, envelhecimento acelerado e teste de tetrazólio. Foi medida a atividade das enzimas antioxidantes: Superóxido Dismutase e Guaiacol Peroxidase; e a peroxidação lipídica. As avaliações foram realizadas no delineamento inteiramente casualizado, em esquema fatorial 2x4, com quatro repetições. As cultivares de soja CD 208 e CD 215, com maior teor de lignina no tegumento, são menos suscetíveis ao dano por umidade. As sementes da cultivar CD 208 também apresentaram menor estresse oxidativo, quando submetidas a deterioração por umidade.