The activity and interaction of brassinolide and gibberellic acid in mung bean epicotyls

The growth rate of mung bean epicotyls was used for evaluating the effect of brassinolide on cell elongation. Growth above that of control plants was observed at 10−10M and above. Gibberellic acid showed an additivity relationship with low concentrations (10−9–10−8M) of brassinolide in this test system and the two growth promoters may therefore act independently at the cellular level. Because of relative ease of operation, great sensitivity and the short time required for assessing biological activity, this assay could be used in conjunction with the bean second internode bioassay for evaluating the activity of brassinolide and its analogs, as well as of other growth promotors.