The Growth of Four Rice Varieties as Affected by Temperature and Photoperiod with Uniform Daily Periods of Daylight

Abstract

SummaryThe growth and grain production of four rice varieties were compared under controlled environment conditions at two minimum night temperatures (15 and 23°C) and at two daylengths (11½ and 13 hours) where the period of daylight for active photosynthesis was kept constant at 8 hours. The lower night temperature prevented flowering but at the higher one grain yields were associated with panicle weights rather than panicle numbers, and production of so-called photoperiod-insensitive varieties was affected by photoperiod. Although the periods of natural light were constant, and photoperiods were extended by low intensity incandescent light, in-creased total plant weights, not due to effects on tillering, were observed under longer days.