Histological studies of shoot regeneration system in hypocotyl-derived callus of Phellodendron amurense Rupr.

An efficient in vitro plant regeneration was achieved from hypocotyl-derived callus of a medicinal tree Phellodendron amurense. The expected morphogenic response was obtained on the media containing 0.89 µM 6-benzyl aminopurine (BAP) plus 4.52 µM 2.4-dichlorophenoxyacetic acid (2,4-D), 4.44 µM BAP plus 5.37 µM α-naphthaleneacetic acid (NAA), or 2.22 µM BAP plus 4.92 µM indole-3-butyric acid (IBA). A detailed histological study was undertaken to gain a better understanding of cellular changes that take place during the plant regeneration process from callus tissue. This study led to the identification of the cellular origin of shoot regeneration. Histological studies revealed that the new vegetative buds originated from callus that completely altered the morphology of the callus tissues by the 60th day of culture. It also revealed that BAP with NAA or IBA induces plant regeneration through organogenesis whereas BAP with 2,4-D induces embryo-like-structure (ELS) through hypocotyl-derived callus. The presence of ELS lacking root poles was also observed.