Morphophysiological and biochemical changes in castor bean seeds (Ricinus communis L.) subjected to gamma Radiation Cobalt-60.

O presente estudo teve por objetivo avaliar a radiossensibilidade de sementes de mamona cultivar IAC80 submetida a diferentes doses de radia????o gama cobalto60. Primeiramente foi feita a remo????o mec??nica da car??ncula das sementes, foram pr??embebidas por 24h em ??gua destilada e irradiadas com radia????o gama cobalto60 (0, 50, 100, 150 e 200 Gy) e posteriormente semeadas em bandejas de isopor contendo solo. Foram feitos testes de condutividade el??trica, emerg??ncia e ??ndice de velocidade de emerg??ncia, an??lises de crescimento e an??lise das enzimas antioxidantes (SOD, CAT e APX) avaliadas nas folhas e nas ra??zes de pl??ntulas de mamona. Os resultados foram submetidos ?? an??lise de vari??ncia e as m??dias comparadas pelo teste de Tukey (5%). A condutividade el??trica n??o foi afetada pelas doses de radia????o utilizadas. Os resultados mostraram que a radia????o gama afetou negativamente o desenvolvimento das pl??ntulas, sendo que a dose de 200Gy reduziu significativamente a emerg??ncia e o ??ndice de velocidade de emerg??ncia. As caracter??sticas morfofsiol??gicas apresentaram redu????o do tamanho das pl??ntulas conforme o aumento das doses de radia????o. Na atividade das enzimas antioxidantes, a super??xido dismutase apresentou diferen??a significativa apenas na dose de 200Gy, para as folhas, n??o sendo significativa nas ra??zes. A atividade da enzima ascorbato peroxidase mostrou aumento da atividade nas folhas conforme o aumento da dose de radia????o. J?? a atividade da catalase n??o mostrou diferen??a significativa quando exposta a diferentes doses de radia????o gama tanto em folhas quanto em ra??zes. A partir do exposto pode-se concluir que as doses de radia????o gama Co60 utilizadas neste estudo mostraram ter um efeito negativo sobre as caracter??sticas morfofisiol??gicas avaliadas neste trabalho. Quanto ?? atividade das enzimas antioxidantes (SOD e APX), a parte a??rea das pl??ntulas de mamona se mostrou mais sens??vel ??s doses de radia????o gama Co60 utilizadas.This study aimed to evaluate the radiosensitivity of castor bean seeds cultivar IAC80 subjected to different doses of cobalt60 gamma radiation. Firstly, the mechanical removal of the caruncle seeds was performed, after being pre-soaked for 24 hours and irradiated with cobalt60 gamma radiation (0, 50, 100, 150 and 200Gy) and, then, sown in polystyrene trays containing soil. Parameters such as electrical conductivity, emergence index and emergence rate, growth parameters and analysis of antioxidant enzymes (SOD, CAT and APX) measured/assessed in leaves and roots of castor bean plantlets /seedlings were evaluated. The results were submitted to ANOVA and the averages compared through Turkey test (5%). The electrical conductivity was not affected by the radiation doses used. The results showed that gamma radiation negatively affected plantlets/seedlings development, given that the dose of 200Gy significantly reduced emergence and speed of emergence index. The growth parameters showed a reduction in the plantlets size with the increase of radiation doses. The activities of antioxidant enzymes, superoxide dismutase showed a significant difference only at a dose of 200Gy to the leaves, not being significant to the roots. The activity of the enzyme ascorbate peroxidase showed increased activity in the leaves as the radiation doses were also increased. The activity of catalase showed no significant difference when exposed to different doses of gamma radiation in both leaves and roots. From the foregoing it can be concluded that the doses of Co60 gamma radiation used in this study were shown to have a negative effect on the morphological and physiological characteristics evaluated in this work. Regarding the activity of antioxidant enzymes (SOD and APX), the shoots of seedlings of castor bean was more sensitive to gamma radiation Co60 used