Influence of High Water-Temperature on the Growth in Rice Plant (Oryza sativa L.)

This study was undertaken for evaluating the effects of the different water-temperatures both on the vegetative growth and on some morphological characteristics of rice plant. The plants were grown in the plastic pots, which were subjected to the respective combination of the day (8 : 30～17 : 30) and the night (17 : 30～8 : 30) water-temperatures in the three sorts of water baths regulated at 25℃, 31℃, and 37℃, respectively. These treatments were conducted during the period from July 1st to August 13th, and the plants were gathered to be examined. The top- and root-growths were most prominent at the constant temperature of 31℃, which were suppressed remarkably at 37℃ during the night, and the growths under the constant high water-temperature (37℃) were made to be ceased completely in a few days. The negative influence of high water-temperature was almost denied almost in the case when the day water-temperature was kept at 25℃ or 31℃, respectively. The plant-length was promoted mostly within the range from 31℃ to 25℃, whereas it was restrained by the high water-temperature (37℃) at day or night, especially at night. Moreover, a rather negative correlationship was noted between the plant-length and the mean water-temperature through day and night. As for the number of roots, the leaf emergence interval, the size of leaf and the diameter of crown root, These were correlated closely with the mean water-temperature through day and night rather than with the difference between the day or night water-temperature