Histological observations of morphogenesis in petiole derived callus of Amorphophallus rivieri Durieu in vitro.
The initiation and development of somatic embryos and organogenic shoots and corm-like structures (CLSs) from petiole-derived calli of Amorphophallus rivieri Durieu were observed histologically. The petioles were cultured on Murashige and Skoog (MS) medium supplemented with 5.37 microM alpha-naphthaleneacetic acid (NAA) and 4.44 microM N(6)-benzylaminopurine (6-BA) for callus induction. The shoot and corm organogenesis occurred from the compact calli when they were transferred to a medium containing 0.54 microM NAA and 4.44 microM 6-BA. A combination of 13.57 microM 2,4-dichlorophenoxyacetic acid (2,4-D) and 8.88 microM 6-BA or 24.18 microM NAA and 6.66 microM 6-BA was optimum for induction of somatic embryos, which failed to produce plantlets because of their structural abnormalities. Shoot regeneration predominantly happened through organogenesis although somatic embryogenesis infrequently occurred. The subepidermal cells of the compact callus converted to competent cells and started divisions, which resulted in formation of the meristemoids. The meristemoid cells continued division to develop into bud primordia. Subepidermal cells could also form the globular structures. Subsequently, these globoids developed into CLSs from which plantlets regenerated during subculture. Meanwhile, the CLSs were capable to form cormels, which could be a promising way for the propagation of A. rivieri.