Effects of carbohydrate addition on the induction of somatic embryogenesisin Hevea brasiliensis

The effect of different carbohydrates was tested on early somatic embryogen esis of Hevea brasiliensis. Sucrose was replaced with maltose, fructose or glucose. Somatic embryo production was significantly higher with maltose. W ith maltose, the initial yellow colour of the calli turned orange, and dry matter production after 28 days' culture was half that obtained with sucros e. Maltose also reduced the soluble sugar content by around 60%, whereas in the presence of sucrose, the soluble sugar content of calli increased. On maltose medium, embryonic cells were initiated after 2 weeks, whereas calli obtained on media containing sucrose mostly consisted of parenchymatous ce lls. The embryogenic cells rapidly formed into globular embryos. The origin of the `maltose' effect is discussed: is it carbohydrate stress or a signa l molecule? The effect of maltose was checked on 6 Hevea callus lines maint ained in the laboratory.