Abstract
This is a part of the experiments on the physiological effect of rice plant to irrigation. The degree of respirationof the plant cultivated in pots and different conditions was measured by determining the volume of CO2 expired. The experiments were classified into two divisions, direct sowing and transplanting, and frurther subdivided by the openning time of the irrgation. As to the method of measuring the degree of respiration, we determined the amount of carbon dioxide expired by the rice plant per one hour by introducing it into the barium solution, the concentration of which had been known, and titirationg the solution gy N/10 oxalic acid. The data in the figures thus obtained were converted into per one gram of dry matter for the benefit comparison.The essential points of the results were as follows: 1) In each plots of the direct sowing, the degree of respiration was found to be deteriorated gradually since the 11th of July to the heading 2)In the transplanting plots, the volume of CO2 decreased in each plot till the 29th of July, but it has a tendency to increase somewhat before the heading 3) In both the direct sowing plots and the transplanting, the volume of CO2was almost the same till the end of July, but before the heading it was generally found a little more respiration in the transplanting plots than in the direct sowin.4) The degree of respiration seems to have a tendency to be affected by the different conditions of cultivation, especially the abrupt changes in the soil seem to cause the increase of the amount of respiration.
