Abstract
Using several cultivars, the response in heading date to air-temperature was studied. Rice plants transferred to air-temperatures of 30°, 25° and 20° at young-ear-formation stage headed in 15 and 20 days and may have headed in 40-45 days, respectively. Plants transferred for 7 days to 24°/19° and 18°/13° (day/night temperature) at three stages during early ear development headed several days later than the outdoor control. Plants transferred to 35°, 30°, 25°, 20° and 15°C day temperatures (night temperature was 5° lower than the respective day temperature) when the auricle of the boot leaf reached the same level as that of the leaf below headed in 7, 8, 11, 16 and 26 days, respectively. Differential soil temperatures appeared to affect heading to a slight extent.
