Diurnal Changes of α-Amylase Activity and Starch Content of Rice (Oryza sativa L.) Seedlings

Abstract

Diurnal changes of α-amylase activity and starch content were examined in the seedlings of three-types of rice (Oryza sativa L.), i.e., Indica type (cv. IR24), Japonica x Indica type (cv. Suweon 258) and Japonica type (cv. Nipponbare). The results obtained are summarized as follows: 1. In all varieties the α-amylase activity was lower during the daytime (6 a.m. to 6 p.m.) than durng the nighttime (6 p.m. to 6 a.m.). The activity was highest between 4 a.m. and 6 a.m., and rapidly decreased between 7 a.m. and 9 a.m.. 2. The average activity of α-amylase in a day was highest in IR24, a little lower in Suweon 258, and lowest in Nipponbare, which was about 30% of that in IR24. 3. The diurnal changes of starch content showed a tendency converse to those of α-amylase activity: viz, starch content was lower during the nighttime than during the daytime in all varieties. 4. The average of starch content in a day was highest in Suweon258, a little lower in IR24 and lowest in Nipponbare.