Studies on the effects of high water temperature during daytime and night upon the growth and yields of rice plants. 2. Yield of the rice plants as affected by high water temperature.

摘要

As the water temperature was considered to be a very important problem to be dealt with in relation to the causes of low productivity of second crop of paddy rice on Okinawa, the influence of high water temperature to it was tested. The relationship between high water temperature and the growth of rice plant was already reported in the previous publication. Then the infuence of high water temperature to a yield of paddy rice was dealt in this paper. The results are as follows: 1. Both culm length and panicle length were dipressed by high water temperature, especially by that of night. The influence of difference water temperature to the weights of a panicle and of panicles per hill was clearly observed (Table 1). 2. Not only weight of a panicle but also a number of panicles per hill were decreased for the plots where water temperature was kept high during night. This, in turn, resulted the increase in weight of panicles per hill (Table 1). 3. The high water temperature at night affected to decrease both the rachis of second order and the number of grains attached to top of them (Table 2. Fig. 1). This attributed a decrease in grain number per panicle. Since the number of panicles was also decreased with the high water temperature at night, total grains per hill were small in number. 4. The percentage of sterile and defective grains was high in the plots where water temperature was kept high at night, while it was remarkable low in the plots where water temperature was varied between day and night (Table 1). 5. As the growth of both palea-and-lemma and endosperm was good in high water temperature at night, the weight of 1000 grains and 1000 hullhd grains was increased and the size of hulled grain became large (Table 5).