Metabolite Contents and Panicle Development in Indica Rice Varieties Belonging to Different Growth Duration Groups

Abstract

Growth, spikelet number and assimilate contents of the panicle on the mainshoot of 20 indica rice varieties consisting of four duration groups were measured at intervals during the period between 2 weeks prior to anthesis and maturity. Panicle development was of longer duration in the late maturing varieties than in the early, and grain yield of the former was more than that of the latter due to difference in grain number. Shifting the cultivation of an early duration check variety to match the time of reproductive development in the medium duration group did not change its pattern of development. During development, the concentration of soluble carbohydrates, amino acids and phosphates changed significantly with time, and the pattern was the same in all varieties. Initially the concentration was low, but increased sharply a few days before anthesis to a peak level, then declined until anthesis. After anthesis it decreased to a minimum at maturity. Pre-anthesis metabolite concentration of the panicle was higher in the late varieties than in the early varieties, but not much difference was observed post-anthesis. Growth durations of the vegetative, reproductive and grain filling periods collectively influenced grain yield but, on the basis of partial correlation analysis, the vegetative duration was found most important for yield.