DEVELOPMENTAL ELECTRON-MICROSCOPY AND HISTOCHEMISTRY OF SOMATIC EMBRYO DIFFERENTIATION IN SUGARCANE

Embryogenic callus formation and growth of somatic embryos of sugarcane (Saccharum officinarum L.) were followed by electron microscopy in order to investigate the correlation between the morphological sequence of events and some ultrastructural aspects of storage reserve accumulation. Observations of the differentiation symptoms showed that the embryos pass through distinct morphological stages, superficially reminiscent of those in grass zygotic embryos; with structural bipolar embryonic orientation showing distinctively clear embryo axes and scutellum. Histochemical and ultrastructural examinations revealed that both tissues accumulated significant amounts of the major storage reserves which were sequestered in membrane-bound units, though some differences in storage protein accumulation were observed between them at the later stages of embryo development. Taken together, the developmental and ultrastructural implications of these results are of interest since they show that sugarcane somatic embryos can recapitulate events in zygotic embryos and may, probably, have significance in their utility in synthetic seed technology.