Abstract
Rice plants were grown in rooms of the phytotron at the Hokkaido National Agricultural Experiment Station. Leaf temperatures of the plants were measured by an infra-red radiation thermometer at the booting stage.
Leaf temperatures were close to the air temperatures in rooms where the temperature was maintained at 24°C (natural light rooms) or 23°C (artificial light rooms) . While in rooms where the temperature was 12°C (natural and artificial light rooms), leaf temperatures were higher than the air temperatures. In natural light rooms, the differences were about 4°C on a clear day and about 2°C on a cloudy day. In artificial light rooms, the differences were about 0 to 2°C, depending on leaf height. Single leaves (or leaf parts) which received light vertically or at an angle of more than 45° showed 1 to 2°C higher temperatures than those of leaf groups.
