Studies on the Emergence of Rice Seedlings in the Direct-Sowing Culture : V. Effect of high temperature treatment of seeds before sowing on the emergence in paddy rice seedlings

Abstract

In this study, effect of high temperature treatment of seeds before sowing on the emergence in paddy rice seedlings were examined. Materials were two paddy rice varieties "Koshijiwase" and "Hoyoku" in japonica type, and cultural temperature was about 20°C. Seeding-depth were 5 and 7cm, and soil moisture content was about 19 per cent (pF value was about 3). The following results were obtained. 1. High temperature treatment of seeds before sowing promoted the emergence in rice seedlings. The promotion was more obvious under the conditions of 5 cm or more depth of seeding and compacted covering soil. 2. The most effective high temperature treatment of seeds before sowing was as follows. (i) Moisture content in seeds before the high temperature treatment; 24-27 per cent. (ii) Volume of vessel in which contains seeds during the high temperature treaument; 4-40 times larger than the volume of seeds. (iii) High temperature treatment; 4-8 days at 40-44°C.