Applied GA-3 was not altered in leaves of rice plants and kidney bean var. Mantle, one of the most sensitive varieties to GA-3, when those were treated with GA-3. But, GA-3 was changed to an unknown gibberellin in leaves of kidney bean var. Masterpiece, one of the least sensitive varieties to GA-3. Experimental results indicate that GA-3 itself has growth promoting effect on both kidney beans and rice plants, while the unknown gibberellin has not the effect. The fact that this unknown gibberellin exerts growth promoting effect on rice plant and not on kidney bean varieties can be explained by the result that this unknown gibberellin is easi1y converted to GA-3 in rice leaves, but not so in leaves of kidney beans.