Rates of leaf appearance and panicle development in rice ( Oryza sativa L.): a comparison at three temperatures

Abstract

Plants of rice ( Oryza sativa L., cv. IR36) grown in controlled environment cabinets in free-draining or waterlogged pots at 20, 24 or 28°C with a photoperiod of 11.5 h day −1 were harvested serially and dissected in order to monitor leaf appearance and panicle development on the main culm. Temperature influenced the leaf appearance rate, the leaf number at panicle emergence and the panicle development rates strongly ( P < 0.01 in each case). In contrast, no significant effects of the water-management protocols were detected ( P > 0.25). No abrupt change in the leaf appearance rate was evident at panicle initiation: within each régime, a constant leaf appearance rate quantified relations between the number of emerged leaves and the time from sowing satisfactorily until 10 days after panicle initiation. Between 20 and 28°C linear relations were found between temperature and both the rate of progress towards panicle initiation and the rate of progress towards panicle emergence. In contrast, the rate of leaf appearance was no greater at 28°C than at 24°C; the optimum temperature was about 26°C. Hence, the value of this cardinal temperature differs between foliar and floral development; rice crop growth simulation models need to be modified accordingly.