Histological observation of root bud formation of hairy roots in Lotus corniculatus L.

Abstract

AbstractThe anatomy of endogenous buds formation in hairy roots transformed by infection with a wild strain of Agrobacterium rhizogenes, A‐13, was studied in birdsfoot trefoil (Lotus corniculatus L.). Hairy root cultures, which had been subcultured in the dark, formed green spots (GS) spontaneously within 20 days after transfer to light conditions, and then GS developed to shoots. The GS structures were produced directly on the hairy roots showing no caulogenesis. Transverse sections at the center of GS structures showed that prominent mitotic activities existed inside of the endodermis, which consisted of a layer of spindly cells. Those proliferated regions composed the GS structures and root buds arose from these regions. Within 20 days after emergence of GS, the meristematic regions developed to shoots, and the apex had distinct single‐layered tunica with leaf primordia. The region of the root in which bud initiation occurred was the pericycle. Differentiation of root buds from the other origin of root tissues such as cortical cells and root apical cells was not found.