Studies on the effect of the relative humidity of the atmosphere on the growth and physiology of rice plants. VI. Effect of ambient humidity on the photosynthetic rate of a rice plant population model.

Abstract

The effect of ambient humidity on the photosynthetic rate of a rice plant population model (area: 120×60 cm, Planting density: about 40 plants/dm2, leaf area index: 6∼7, plant height: about 30 cm, plant age in leaf number: about 6) was investigated at the air temperatures of 22, 28 and 34°C under artificial light. The stomatal aperture and the leaf temperature of leaves in the upper part of the plant population were also determined. The results obtained are as follows. 1. The photosynthetic rate of a rice plant population responded quickly to the changes in the relative humidity: the rate increased with the rise of humidity and decreased with its fall. 2. The stomatal aperture and the leaf temperature in the upper part of a population also quickly changed in proportion to relative humidity. These results suggested that the photosynthetic rate of a rice plant population responded quickly to humidity changes through the rapid change of stomatal aperture mainly, and also suggested that the increase of the leaf temperature with the increase of humidity enhanced the photosynthetic rate of the plant population at a low temperature (22°C) and suppressed the rate at a high temperature (34°C).