α-Amylase Activity and Soluble Sugar Supply from Endosperm in Relation to Varietal Differences in Seedling Establishment under Low-Temperature Conditions in Rice (Oryza sativa L.)

Abstract

We examined 𰂱-amylase(EC 3.2.1.1) activity in endosperm in 6 varieties of rice (Oryza sativa L.), which showed different seedling establishment traits in field experiments, using seedlings grown in sterilized agar-bed at 16ºC. At the coleoptile elongation stage and the first leaf elongation stage, there were significant differences in 𰂱-amylase activity among the varieties investigated. However, the varietal difference in 𰂱-amylase activity at the coleoptile elongation stage did not correspond with that in coleoptile growth. Maltose, the immediate product of 𰂱 -amylase activity, accumulated in the endosperm at the coleoptile elongation stage in a greater amount in Fukuhibiki, which has a poor seedling establishment trait, than in Arroz da Terra, which has a superior seedling establishment trait. The concentration of glucose detected in the exudate from the endosperm adjacent to the scutellum at the coleoptile elongation stage was also higher in Fukuhibiki than in Arroz da Terra. The results obtained in sterileagar-bed conditions clearly demonstrated that neither deficiency in 𰂱-amylase activity nor glucose production in the endosperm were responsible for coleoptile growth retardation at 16ºC. Therefore, neither 𰂱-amylase activity nor sugar supply from the endosperm were responsible for the varietal differences seen in the rate of seedling establishment in paddy fields at around 16ºC.