Studies on Water Management in the Ill-drained Paddy Field : VII. The effect of the surface drainage on the photosynthetic activity in rice plant

[摘要] Authors investigated an influence of the surface drainage on the photosynthetic activity in rice field. The yield of rice plants was increased by the surface-drainage treatment given during a period from the end of feritile tillers formation until the soil moisture content decreased to 70%. According to the analysis of harvested materials, this yield-increase was chiefly due to the increase in ripened grains number, ratio of ripened grains to total grains in an ear, and weight of 1000 unhulled kernels. To know the reason for this, authors measured the apparent photosynthetic activiiy of rice population in field, and discussed the relation between the photosynthesis and other characters in rice plant. The total leaf area of rice plant in this drainage-plot was generally inferior to that of the constantly water-logged plot (cortrol-plot), both in the draining stage and in the subsequent irrigating stage. Connected with the total leaf area, the light transmission rate in the drainage-plot was always inclined to be higher than that of the control-plot. The water content of rice plant was lower in the drainage-plot than in the control plot, not only in the draining stage but also in the subsquent irrigating stage. Though the photosynthetic activity per unit area either of rice leaves or of the field was depressed by such draining treatment, it was promoted by the subsequent irrigation. This superiority of the photosynthetic activity in the drainage-plot lasted until the ripening stage and attributed to the yield increase. Although it has been reported by some researchers that the photosynthetic activity per unit leaf area has highly positive correlation with the water content in rice leaf blade, but in this study the correlation between them was partially disturbed because other factors caused by drainage treatment might presumably benefit the photosynthetic activity.

[学科分类] 农业科学（综合）