The Relationship between Germination Rate of Rice Seeds at Low Temperature and the Subsequent Early Growth of Seedlings : II. On some properties of roots at early stage

Abstract

In order to establish the direct-seeding cultivation of rice on the submerged paddy field in such cool region as in Hokkaido, it is very important to stabilize the germination after seeding and to stabilize the subsequent standing of seedlings. Standing of seedlings is affected seriously by the root development conditions at the earlier stage. In view of this, in order to clarify the relation between the viability of rice seeds to germinate at low temperature (having close bearings on the stability of germination of seeds) and the viability of roots to develop at earlier plant growth stage, the authors made the experiments in 1967 under the conditions of the direct-seeding on the submerged paddy fields (indoor) by using 23 varieties as samples. The results of the experiment are summarized as follows : 1. With respect to the relation of the viability of paddy rice seeds to germinate at low temperature to the some properties of roots (the number of roots, the maximum length of roots, and the weight of roots of the seedlings), significant or some positive correlations were observed in both cases of 10-day old seedlings and 20-day old ones, irrespective of the difference in water depth (3 cm and 6 cm), but in the case of 20-day old ones, the correlations were observed more clearly than in the case of 10-day old ones. 2. Regarding the inter-or intra-relations among the number of roots, the maximum length of roots and the weight of the seedlings, very high correlationships were noticed, irrespective of difference in the water depth as well as in the number of days after seeding. Even at the relatively early stage after seeding, the same varietal differences were observed under different conditions such as depth water. 3. On the other hand, with respect to the relation between the plant height and the root development, very high positive correlation was observed. When authors tried to find out the partial correlations among the germination rate of seeds at low temperature, plant height and the root development at earlier stage, the significant correlation was observed between the plant height and the root development at earlier stage, excepting the effect of the germination of seeds at low temperature. 4. Viewed from the above test results, the positive correlation found between the germination rate of seeds at low temperature and the root development at earlier stage is regarded as the derivative action through the plant height. However, the significant correlation between the germination rate of seeds at low temperature and plant height of seedings was observed as reported in preceding paper (SASAKI, 1968), so, authors dissussed that it was very significant to use the rice varirties high in germination rate at low temperature to ensure the stability of direct-seeding rice culture on the submerged paddy field in such cool region as in Hokkaido.