Abstract

1. Effect of gibberellic acid (1 % K-salt of GA in lanolin) on transpiration rate, plant height, leaf area, dry weight of tops and roots, internode extension, internode diameter, flowering, development of roots, and nodulation in Adzuki (Azuki) bean (Phaseolus sp., a commercial dwarf bean cultivated in Japan and China) were investigated. 2. Young seedlings grown in Hoagland's nutrient solution in glass beakers were treated with GA-paste at the first internode. Water loss (i.e. water consumption) experienced by culture solutions during a period of 24 hours were measured one and two weeks after treatment. Plant height, leaf area, and dry weight were measured at the same time. Height of treated plants was remarkable greater; total leaf surface area of them, however, was notable less. Dry weight of both tops and roots of treated plants was less; dry weight of roots of treated plants was notable less while that tops was not significantly affected. T/R ratio of treated plants was greater than that of controls. Transpiration rates of GA-treated plants were less than that of controls if the rates were calculated per plant, per dry weight of tops or per total dry weight. If leaf area or dry weight of roots were used as a basis for expressing rates of transpiration, the rates of GA-treated plants were greater than that of controls. 3. Young plants grown in soil in pots were treated with GA-paste at the first internode one week after seeding. The appearance of new internode of GA-treated plants was earlier than that of controls. The cessation of internode extension took place earlier in treated plants. Number of internode was not affected by GA application. Diameter of the first internode of treated plants was greater than that of controls whereas the diameters of the second and third internodes were less. Flowering of these plants was not hastened. Flower numbers were not significantly affected by GA application. 4. The growth promoting effect of GA on petiole elongation was closely coincided with the growth region of the petiole. 5. Initiation and growth rate of secondary and tertiary roots, and nodulation were inhibited by the application of GA-paste.