Abstract
The soil culture of rice seedling was designed to confirm the growth-promoting effect of gibberellins in crop residuals. Fully ripened pericarps of Cuba beans and detached cotyledons of kidney beans were used as the source of gibberellins. A considerable amount of acidic ethyl acetate soluble gibberellins was detected even in the ripened pericarps of Cuba beans which have been air-dried for about one year after harvest (Fig. 1). In detached cotyledons of kidney beans (Kentucky Wonder, a tall variety), a considerable amount of gibberellins was also detected in both acidic ethyl acetate and n-Butanol fractions (Fig. 3). All the materials were added to the soil in petri dish after being milled, and germinated seeds of Tanginbozu, a dwarf rice variety, were sown in the beds. The growth of the second leaf sheath was found to accelerated by adding those materials to the soil (Figs. 2, 4, 5). The bound type gibberellins were found to convert into free type in soil, while free type ones are comparatively unchangable in the soil (Fig. 3). Gibberellin activity in cotyledons is relatively greater in tall variety of kidney bean than in dwarf one. The growth of the second leaf sheath in rice seedling was hardly accelerated when the cotyledons of the dwarf variety was added (Figs. 4, 5). As shown above the effect of endogenous gibberellins contained in plant residuals can be observed by such a simple method employed in this experiment.
