Difference of optimum germination temperature of seeds of intact and dehusked japonica rice during seed development

Abstract

The effects of incubation temperature on germination of intact and dehusked japonica rice that had been harvested every 5 days from 10 days after anthesis (DAA) to 70 DAA were surveyed. At 30 ^°C incubation, the germination percentage of intact seeds at 25 DAA exceeded that of dehusked seeds. This tendency persisted until 65 DAA, when around 95% of both intact and dehusked seeds germinated. Germination percentages of intact seeds incubated at 20 ^°C were lower than seeds incubated at 30 ^°C for all DAA. However, germination percentages of dehusked seeds incubated at 20 ^°C were consistently higher than at 30 ^°C. Germination percentages of intact and dehusked seeds were similar at 20 ^°C incubation. Germination of intact seeds under 34/11 ^°C (16/8 h) was higher than at 30 ^°C. In contrast, germination of dehusked seeds under 34/11 ^°C (16/8 h) was lower than at 30°C. Inhibitory effects of removing husk on germination were observed from 15 to 70 DAA. Almost all of the intact seeds at 45 DAA germinated when imbibed 35, 30 and 25 ^°C, and germination percentages decreased with decreasing incubation temperatures from 20 to 15 ^°C. By contrast, germination percentage of dehusked seeds was highest in 20 ^°C incubation temperature; further increase or decrease of incubation temperature reduced germination percentage. The optimum germination temperature of intact and dehusked seeds of japonica rice differs during seed formation, such that the extent of germination inhibition by husk removal depends on the incubation temperature.