Abstract
1) This experiment aims to make clear the heading characteristics of japonica rice varieties under different sowing time at Ceylon. This experiment was conducted at the Central Agricultural Research Institute, Peradeniya, Ceylon in 1965.
2) Sixteen varieties were sown at about one month interval in cement pots. These varieties consisted of 10 Japanese paddy varieties, 2 Japanese upland varieties, 2 Taiwan varieties (Ponlai) and 2 Ceylon short duration varieties. Heading date and number of leaves on the main stem was recorded.
3) The heading time of japonica varieties were controlled almost exclusively by their basic vegetative growth period, because the variation of temperature was very small and the photosensitivity was digested due to the natural daylength shorter than the critical daylength of optimum region of them. It is considered that the basic vegetative growth of Japanese paddy varieties were too short to get high yield.
4) There is difference between Japanese paddy varieties and others about the relationship between number of days from sowing to heading and number of leaves on the main stem. The leaf emergence intervals of Japanese paddy varieties are smaller than those of other varieties. If there is any difference of growth habit between Japanese paddy varieties and others, this may be interesting.
