The Relationship between Germination Rate of Rice Seeds at Low Temperature and the Subsequent Early Growth of Seedlings : IV. On the establishment of seedlings

In order to establish the direct sowing in flooded paddy field in such cool region as in Hokkaido, it is very important to stabilize the growth during the early stage of the plants, In view of this, and to clarify the relation between the varietal differences of rice seeds to germinate at low temperature and the degree of establishment of seedlings under the conditions of direct sowing in flooded Paddy field, the authors made some experiments in 1968 and 1969, by using 36 varieties as the experiment materials. The yielded results are summarized as follows ; 1. Regarding the relation between the germinability of paddy rice seeds at low temperature and the percentage establishment of seedlings, in 1968, in which water temperature after seedings was relatively low, significant positive correlation was observed. And in 1969, in which water temperature after seeding was relatively high, correlation was not so high, but if four varieties which widely slipped out of the whole tendencies were excluded, very significant positive correlation was also obtained. 2. In 1968, the decrease of percentage establishment of seedlings was mainly resulted from the increase of premature decay of seedlings, while in 1969, it was resulted from the increase of the floating and turned down seedlings. 3. With respect to the relation between the percentage establishment and the dry matter weights of seedlings and of roots, significant positive correlations were observed in both years. 4. The authors reported previously that there were positive signiftcant correlations between germinability at low temperature and the degree of elongation of seedlings and of root at early stage of growth. Thus, to sum up these results, it becomes clear that the germinability of paddy rice seeds at low temperature was a useful characteristic to ensure the stability of establishment seedlings nuder the condition of direct sowing in flooded paddy field in such cool regions as in Hokkaido. 5. As to the relationship between the percentage establishment of seedlings and T/R ratio in dry weights of seedlings, a significant positive correlation was observed in 1969, even though only one variety "wasebozu" which differed widely from the whole tendencies was in existance.