Studies on the Effects of Soil Temperature upon the Growth of Crop Plants : III Soil temperature and leaf emergence of rice plant. : VIII Relation of temperature of several parts of rice plant to the rate of leaf emergence.
The effects of soil temperature upon the rate of leaf emergence in rice plant were investigated. The results obtained were as follows : 1) From the first experiment in which rice plants were grown with 23 and 28°C soil temperature in the air temperature-controlled conditions kept at 20 and 30°C respectively, it was recognized that the rate of leaf emergence were affected by the soil temperature and not by the air temperature (Fig. 1). 2) In the second one, plants were grown with 23, 28 and 33°C soil temperature by use of the constant temperature water tanks out of doors, and it was concluded that the effect of soil temperature upon the rate of leaf emergence differed according to the growing stage. Namely, it was much significant at the first half period of the tillering stage and not at the jointing stage (Fig. 2 and 3). 3) Finally, for the purpose of investigating the reference of the rate of leaf emergence to the temperature of several parts of plant, i.e., leaf sheath (A) in irrigation water, base of seedling (B) in soil, and root (C), the part A and (B+C) or (A+B) and C were exposed to the different temperature separately. These parts were treated with temperature of 20 and 30°C respectively (Fig. 4). According to the result of this experiment, it was cleared that the temperature of leaf sheath was less influential upon the rate of leaf emergence than those of base and root (Table 2, and Fig. 5).