Influences of gibberellin and auxin on endogenous plant hormone and starch mobilization during rice seed germination under salt stress

The soaking effects of two plant hormones, gibberellic acid (GA 3) and indole-3-acetic acid (IAA) on dehulled rice seeds exposed to low NaCl stress were investigated. Total soluble and reducing sugars in endosperms of rice seeds soaked with GA 3 (10 &M) increased gradually as germination progressed under low NaCl stress. This increase was more pronounced in IAA-soaked rice seeds than in GA 3-soaked rice seeds. Similarity of +-amylase activity in IAA-soaked germinating rice seeds was much more stimulated than that soaked with GA 3. IAA- and GA 3-soaked rice seeds showed relatively high amounts of endogenous IAA under salt stress. In particular, IAA content increased more in GA 3-soaked rice seeds than in IAA-soaked rice seeds. Furthermore, gibberellin content in IAA-soaked rice seeds showed the highest concentrations among all the treatments. It suggests that recovery effect in starch mobilization and root elongation is in some part regulated by soaking treatment of plant hormones under lower salt stress in rice seed germination.