The effect of 24-epibrassinolide on the growth and dominance of pea (Pisum sativum L.) seedling buds

The effect of 24-epibrassinolide (BR) on the growth and dominance of pea seedling buds was studied and compared with the effect of auxin (indole-3-acetic acid - IAA) and cytokinin (benzyladenine - BA). A 0.1% concentration of BR, as well as of IAA and BA, inhibited the growth of intact plants, while a 0.01% concentration was ineffective. IAA is a plant hormone that enhances the apical dominance of the stem, what was confirmed when the growth of cotylary axillary buds was inhibited after the decapitated stem apex was substituted with 0.1% IAA. This is not an attribute of BR, because the same concentration of BR had no significant effect on the growth of cotylary axillary buds of the decapitated plants. A 0.1% and 0.01% concentration of BA paste applied to the remaining cotyledon of decapitated and of one cotyledon deprived plants released the cotylary bud from the growth inhibition of the cotyledon. However, BR did not release the bud from the inhibition of the cotyledon, either in a 0.1% or 0.01% concentration. BA (0.1% and 0.01%) was capable of determining the growth of cotylary buds if applied on one of the two cotyledons of the decapitated plants, because the growth of the BA-treated cotylary bud was stimulated. The same stimulation was observed after applying 0.01% BR.