Control of its vitro somatic embryogenesis of the spindle tree (Euonymus europaeus L.) by the sugar type and the osmotic potential of the culture medium

In vitro somatic embryogenesis was achieved from zygotic embryo explants of a woody angiosperm species, the spindle tree, cultivated on various cultur e media differing in their sugar type and concentration, or in the applied osmotic potential. The highest frequency of somatic embryogenesis was obtai ned with a 350 mM sucrose, or a 89 mM glucose concentration in the culture medium. Experiments with culture media differing only in osmotic potential indicated that a minimal threshold osmotic potential is required to stimula te the emergence of somatic embryos. Elevated concentrations of glucose hav e an inhibitory effect, independent of their osmotic effect, while elevated concentrations of sucrose mainly act osmotically, stimulating the emergenc e of numerous somatic embryos.