Changes in the Activity of Some Hydrolases, Peroxidase, and Catalase in the Rice Seed during Germination

A study was made of the changes in activity of enzymes involved in the breakdown of stored phytin, lipid, and hemicellulose in the aleurone layer of rice seed (Oryza sativa L., variety IR8) during the 1st week of germination in the light. Enzyme assays were made on crude extracts from degermed seed, and activities were expressed on a per seed basis. Phytase activity increased within the 1st day of germination. The increase in activity of most other enzymes-phosphomonoesterase, phosphodiesterase, esterase, lipase, peroxidase, catalase, beta-glucosidase, and alpha- and beta-galactosidase-closely followed the increase in protein content. Their peak activities occurred by the 5th to the 7th day. Some enzymes, such as beta-1, 3-glucanase and alpha-amylase, continued to increase in activity after the 7th day. Phytase, beta-1, 3-glucanase, and alpha-amylase followed a similar sequence of production in embryoless seed halves incubated in 0.12 muM gibberellin A(3), but the production of lipase was delayed.