Specific Rooting Activity of 4-(3-indolyl)-4-butanolide Formed in Early Stage of Bupleurum falcatum L. Root Culture with Indole-3-butyric Acid

Abstract

Indole-3-butyric acid (IBA) induced vigorous rooting in Saiko (Bupleurum falcatum L.)-cultured roots after about 2 weeks. In medium at the first day of the culture, we found a novel IBA derivative, 4-(3-indolyl)-4-butanolide (IBL).
Synthetic IBL induced rooting on both cultured roots of B. falcatum and cuttings of Vigna radiata L. Wilczek. We histologically compared the effects of IBL and IBA on cultured roots of B. falcatum. IBA induced considerable thickening of the original roots, due to marked cell expansion and division in the cortical tissue. On the other hand, IBL did not show cell expansion, but induced cell division as strongly as IBA. Although auxin suppresses root elongation with unneutral growth of the cotyledons of Raphanus sativus, IBL shows none of those effects. The results suggest that IBL may play a specific role in the rooting process induced by IBA.