Abstract
The concept of the constancy of accumulated effective temperature to the growth in paddy rice plants was examined under the controled environment for several rice cultivars which had different local adaptability. The results obtained were summerized as follows: 1. The constancy of accumulated effective temperature was maintained in varieties adapted to cold Hokkaido district to some degree. For the varieties adapted to the warm district of Japan, however, the concept was not applicable. 2. Influence of daylength must be taken into account when we examine the accumulated effective temperature always. 3. As to the accumulated effective temperature required for the expansion of successive leaves, there was no marked difference between cold and warm district varieties. 4. Under the low temperature condition, there was significant difference of total number of leaves on the main culm between varieties of cold and warm district of Japan. 5. In any cultivars, the constancy in later vegetative growth period, young ear formation to heading, was more notable than that in early period of growth, germination to young ear formation.
