Abstract
(1) Rice plants were grown experimentally by late seeding and transplanting, being thus exposed to cool weathers at their blooming periods, and their flowering and fruiting capabiliy as affected by air temperature was studied. (2) Blooming was found to occur rather more prosperously when the temperature rose even only in a slight extent after a period with lower temperatures which were sub-optimal for blooming, than when it remained unchanged at somewhat higher levels. (3) Decline in fruiting percentage of the flowers due to low temperatures at blooming stage was proved dependent on the growth condition of the plant previous to that stage. Plants which had suffered from shortness of temperature, not being vigorous enough at their flowering stages, showed higher reduction in fruiting percentage by low temperatures, compared with those grown up under favourable conditions. (4) The optimum temperature for flowering in rice plant under natural conditions seemed to lie between daily maximum from 27.5O° to 32.5°C., or more precisely, from 29.5° to 32.5°, and daily minimums from 17.5° to 22.5°, or more precisely from 19.5° to 22.5°C. With a daily maximum temperature below 24.5°C blooming was restrained remarkably.
