Abstract
Effects of day length on turning point of leaf emergence rate (TPL) were examined in 8 rice cultivars, including 3 japonica and 5 indica types under 10-hours and natural day length. The relationships between days after sowing and plant age in leaf number were approximated to two lines, and leaf emergence rate (LER) was estimated from the slopes of those lines. TPL was determined as the intersection of the two lines. As the result of 3-way ANOVA, there were significant differences in TPL and flag leaf emergence (FLE) among treatments and varieties. TPL and FLE were earlier under a short day length than those of under natural day length, and there was a significant positive correlation between them. These results indicated that TPL relates to the earliness of the variety, and that LER in all varieties were decreased slightly after TPL. LER in the early varieties tended to be faster than in late varieties. However, there was an exception such as Miriti, which LER was slower throughout the measurement period. The effect of short day on LER was observed in the regression line after TPL. The LER obtained under 10 hours a short day length was higher than that of under natural day length, and there were significant positive correlations between TPL and panicle initiation stage. These results suggest that TPL relates to the phase transition including panicle initiation phase.
