Plant regeneration from cultured immature inflorescences of coconut (Cocos nucifera L.) : evidence for somatic embryogenesis

Immature inflorescences of coconut belonging to three different genotypes were cultured on a solid medium supplemented with activated charcoal (2%) and a range of 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations (from 1.5 to 3.5 × 10(-4)M). Globular white callus formed from immature floral meristems, depending on inflorescence age and 2,4-D concentration. Acquisition of embryogenic competence is described histologically. Somatic embryos presented a functional bipolar organization with a completely differentiated shoot meristem which is reported here for the first time in coconut tissue culture. Embryo maturation allowed reliable plant regeneration of this in vitro recalcitrant species. Details are given of exogenous hormonal requirements for the acquisition of embryogenic competence and embryo maturation.