Kimio Nakaseko

Effect of continuous ethephon application on culm length, sugar content and yield in spring wheats.

Three varieties of spring wheat, tall Haruhikari, semi-dwarf Haruyutaka and tall late Selpek, were grown in a 5 cm equidistant square pattern (400 plants/m2) and the 100 ppm of ethephon was applied four and six times at four days interval during the period from double ridge stage to flag leaf emergence (DR treatment) and from flag leaf emergence to anthesis (CE treatment), respectively. The ethephone treatments did not influence the phenological events (Table 1), but inhibited culm elongation (Fig. 1), especially the lower internodes in DR treatment and the upper internodes in CE treatment (Table 2). The effect of shortening in culm length was more in CE treatment and in tall varieties than in DR treatment and in semi-dwarf variety. The water soluble sugar content in culm changed higher in CE treatment (Fig. 2), indicating a highly negative correlation with culm length at milk-ripe stage regardless of the treatments and varieties (Fig. 3). The grain yield in DR treatment was higher in all varieties than those in controls, though not significant, mainly due to the increase in number of ears and grain number per ear (Table 4).