Analysis of Yield-Determining Process and Its Application to Yield-Prediction and Culture Improvement of Lowland Rice : XCVIII. Effects of the nitrogen content and thickness of a leaf-blade on the light-curve of carbon assimilation of the obverse, the reverse and both sides of the leaf-blade

[摘要] Using the same apparatus as in the previous paper (XCIV) and using the leaves with four different levels in the nitrogen content as well as in the thickness of leaves, the authors studied the effect of nitrogen content and thickness of leaves on the light-curve of carbon assimilation of the obverse, the reverse and both sides of a leaf-blade. The main results can be summerized as follows. 1) In the case of the obverse of a leaf-blade (flag-leaf) being exposed to light and its reverse being kept in the dark, a leaf-blade with a high nitrogen content or a thick histological construction absorbes much larger amount of CO2 on the obverse than on the reverse at any light intensity, and a remarkable difference in C02 absorption between two sides is always found, while, as the nitrogen content or the thickness, of leaves decreases, the CO2 absorption on the overse goes on decreasing and at the same time, on the contrary, that on the reverse goes on increasing progressively, and as a result the difference in CO2 absorption between two sides comes to be less and lees, and finally no difference comes to be found at any light intensity. 2) A comparison in the total amount of absorbed CO2 on the two sides of a leaf-blade has been made between two cases under the condition of the total amount of light on the two sides being always equal with each other case; i. e. one is the case of the obverse being exposed to light and the reverse being kept in the dark (herinafter written as one side exposure) and the other is the case of both sides being exposed to light with a half light intensity (hereinafter written as two side exposure). The results are as follows. The leaf-blades with a high nitrogen content or thick leaf-blades absorbes much larger amount of CO2 in the case of two side exposure than in the case of one side exposure, and they never show any light-saturation phenomenon up to the light intensity of O.8cal/cm2/min.in the case of one side exposure, while they clearly show a light-saturation phenomenon at the light intensity of O.6∼0.7cal/cm2/min. in the case of two side exposure. However, as the nitrogen content or the thickness in leaves decreases, the light-saturation point starts descending in the case of two side exposure and it also starts appearing even in the case of orLe side exposure, and the difference in CO2 absorption at every light intensity between two cases comes to be less and less and, as a result of it, finally the light-curves of C02 absorption in two cases come to coincide with each other. 3) The differences in the light-curves of CO2 absorption due to different nitrogen levels or thicknesses in leaves can be ascribed to the differences in light-absorption and light-transmission in leaves. 4) The results in the present experiments strotigly suggest the importance of straight and errect leaves, both sides of which are apt to receive sunlight under natural conditions, for increasing the rate of carbon assimilation and consequently the grain yield.

[学科分类] 农业科学（综合）