EFFECT OF ABSCISIC-ACID, OSMOLARITY AND TEMPERATURE ON IN-VITRO DEVELOPMENT OF RECALCITRANT MANGO NUCELLAR EMBRYOS

Development of cotyledonary-stage nucellar embryos of mango was arrest ed in vitro by exposure to 750-1750 mu M ABA. The enlargement and germ ination of nucellar embryos was inhibited for as long as 4 weeks after subculture from ABA-containing medium. Mannitol at concentrations bet ween 7.5 and 12.5% inhibited nucellar embryo development, presumably d ue to osmotic effects; however, there was no residual effect after sub culture of somatic embryos onto medium without mannitol. Temperatures between 22.5 and 37.5 degrees C stimulated embryo development, whereas lower temperatures (7.5 and 15 degrees C) delayed germination. There was no germination 1 month after somatic embryos, pulsed for 8 weeks a t 7.5 degrees C, were transferred to 22.5 degrees C; however, after 2 months, 86% of these somatic embryos germinated. These results indicat e that it is possible to induce developmental arrest in recalcitrant m ango embryos with high concentrations of ABA, mannitol or low temperat ure (7.5 degrees C).