Analysis of Yield-Determining Process and its Appication to Yield-Prediction and Culture Improvement of Lowland Rice : LXXV. Temperature effects on tillering in case of leaves and culm, clum-bases, and roots being independently treated.

摘要

In the previous paper for maximizing yield particular stress was laid on ensuring the necessary number of tillers as early as possible. Therefore, as a step of finding the ways by which the tiller-number is efficiently increased, the authors tried to investigate the temperature conditions which make the rice plant increse the number of tillers as well as the length of tillers. For the purpose they firstly investigated temperature effects on tillering by subjecting each part of the rice plant independently, i. e. leaves and culms, culm-bases, and roots, to various temperatures (16, 21, 31 and 36°C). The results obtained may be summarized as follows. 1. The temperature at the bases of culms, inside of which the growing points are located, is much more effective than the temperature around the roots for increasing the number of tillers as well as the length of tillers, and moreover, it is worthy of note that low temperatures at the culm-base encourage the development of tillers which come out from lower nodes, while high temperatures such as 31°C and 36°C at the culm-base definitely disturb their development. (cf. Fig. 2 and Fig. 3). 2. At the culm-base a considerable high temperature, i. e. 31°C, is favorable for lengthening tillers, while a considerable low temperature, i. e. 16°C, is likely to be indispensable to increase efficiently the number of tillers. (cf. Fig. 2 and Fig. 3) 3. It has definitely been recognized in the experiment that a wide range from a maximum to a minimum in daily temperature at the culm-base is quite advantageous for increasing the number of tillers. (cf. Fig. 4) 4. So far as the experiment is concerned, in case of a whole nursely period being subjected to the temperature treatment, a temperature of 21°C is optimum in air-temperature as well as in water-temperature for increasing the number of tillers of seedlings, but in case of a whole nursery period being divided into two periods, i. e. the first half and the latter half, and each period being subjected respectively to the temperature treatment, high air-temperatures up to 36°C and slightly lower water-temperatures than the air-temperatures are favorable in the first half period, while high air-temperatures as well as high water-temperatures are unfavorable, and low air- and water-temperatures are quite necessary in the latter half period to increase efficiently the number of tillers of seedlings. (The air-temperatures can be considered as the temperatures around leaves and culms, while the water-temperatures can be taken as the temperatures at the culm-basis.)(cf. Table 1 and Table 2)