Action of Gibberellic Acid in Rice Seed

To evaluate the effectiveness of gibberellic acid (GA 3 ) in breaking rice seed dormancy and the use of a-amylase enzyme activity as an indicator of the dormancy level, seed from the intensively dormant irrigated cultivar Urucuia were used. The seeds were submitted to a predrying process in a forced air circulation chamber under 40oC during 7 days and submersed in 30 mL of GA 3 solution under 0, 10, 30 and 60 mg/L H 2 O concentrations, during 2, 24 and 36 hours. After the treatments, the a-amylase activity was determined by using the polyacrilamide electrophoresis and spectrophotometry. At the same time, the germination test was made. The results indicated a gain in germination and in a-amylase activity in higher concentrations and soaking time of seeds in GA 3 . These observations support the conclusion that soaking seed in 60 mg GA 3 /L during 36 hours can be used as a quick and efficient treatment in breaking rice seed dormancy and is equivalent to the forced air circulation chamber at 40oC during 7 days. The aamylase enzyme activity proved to be as an efficient marker of the seeds dormancy level.