Physiological quality rice seed submitted to gamma radiation/Qualidade fisiologica de sementes de arroz submetidas a radiacao gama

The objective of this research was to evaluate the effects of the gamma radiation ([Co.sup.60]) on the physiological quality of rice seeds. The research was carried out through three tests; in the first test rice seeds were irradiated at dosages of 0; 1; 2.5 and 5Gy, while for the second and third tests the seeds were subjected to accelerated aging before being irradiated. For the second test the seeds were divided into wet and dry and both groups subjected to accelerated aging previous to irradiation at dosages of 0; 1; 2.5 and 5Gy. For the third test the seeds were dried after being subjected to accelerated aging, and then irradiated at dosages of 0, 10, 25 and 50Gy. To assess the physiological effects of the gamma radiation, all seeds were tested for germination and their germination speed index recorded. Seedling growth was graded through the measurement of the lengths of the first leaf and seminal root system and total seedling dry weight, across all tests. The enzymatic activity of acid phosphatase and alpha-amylase was measured on dry seeds from the second test. The results from all tests indicate that the applied gamma radiation dosages did not cause any changes to the physiological quality of rice seeds. Key words: Oryza sativa, irradiation, mutagens. O objetivo deste trabalho foi avaliar os efeitos da radiacao gama ([Co.sup.60]) na qualidade fisiologica de sementes de arroz. O estudo foi realizado em tres ensaios. No primeiro ensaio, sementes de arroz foram irradiadas com doses de 0; 1; 2,5 e 5Gy e, para o segundo e o terceiro ensaio, as sementes foram submetidas a envelhecimento acelerado, antes da irradiacao. No segundo ensaio, as sementes foram dividas em umidas e secas apos envelhecimento acelerado e, entao, foram irradiadas nas doses 0; 1; 2,5 e 5Gy. No terceiro ensaio, as sementes foram secas apos o envelhecimento acelerado e irradiadas com doses de 0, 10, 25 e 50Gy. Para avaliacao dos efeitos fisiologicos da radiacao gama, foram realizados teste de germinacao--TG, indice de velocidade de germinacao--IVG e crescimento de plantas (comprimento de parte aerea e sistema radicular e massa seca total), em todos os ensaios. Foram determinadas as atividades enzimaticas da fosfatase acida e alfa amilase nas sementes secas, no segundo ensaio. Os resultados obtidos nos ensaios indicam que as doses de radiacao gama estudadas nao afetam a qualidade fisiologica das sementes de arroz. Palavras-chave: Oryza sativa, irradiacao, mutagenico.