Studies on the Emergence of Rice Seedlings in Direct-Sowing Culture. : 2. Effect of submersion treatment on the emergence of plumule.

Abstract

1) The rate of emergence of plumule decreased with the extension of the period of submer-sion treatment. Under all temperature conditions (20°, 25°and 30°C), the rate of emergence of plumule decreased, with the depth of seeding. 2) The growth of plumule was affected by submersion treatment. This submersion injury was distinct at the treatments, 2 to 5 days after seeding at 30°C. In these cases, the lengths of plumules were about 0.03 to 2.0 cm long. 3) Respiratory activity of plumule was reduced by submersion treatment. In the case of 3 cm-depth seeding at 30°C, the longer the period of submersion, the more was the decrease of the respiratory activity of plumule. 4) The submersion injury to respiration of plumule was strong at the treatments 2 to 5 days after seeding at 30°C, the lengths of the plumules were about 0.05 to 2.0 cm long. The reasons of the bad effects of submersion treatment on the emergence of plumules are as follows: (i) decrease of amount of oxygen in soil, (ii) reduction of respiratory activity, (iii) decrease of energy obtained from respiration, (iv) reduction of growth of plumule, and (v) decrease of the rate of emergence of plumule.