ABSCISIC-ACID AND HIGH OSMOTICUM REGULATION OF DEVELOPMENT AND STORAGE RESERVE ACCUMULATION IN SUGARCANE SOMATIC EMBRYOS

Both abscisic acid and high osmoticum influence (somatic) embryogenesi s in plants. However, the specific effects of these bioregulators on g eneral aspects of embryogenesis and storage reserve accumulation, in p articular, remain quite unclear. Our results showed that abscisic acid and sorbitol could, depending upon their concentrations, act in ways that are either beneficial or detrimental to the frequency of somatic embryogenesis in sugarcane (Saccharum officinarum L.) callus cultures. Complementary studies of sectioned scutellar tissues, using transmiss ion electron microscopy were conducted to examine the in situ localiza tion of storage reserves in cells of somatic embryos treated with: (i) 10(-5) M ABA; (ii) 9% sorbitol; (iii) 10(-5) M ABA and 9% sorbitol; a nd (iv) untreated embryos (control) for 14 days. They indicated that t hese substances elicited storage reserve accumulation differently. Whi lst ABA-treated embryos allocated significantly more of their cell vol umes to protein bodies with no visible amyloplasts, sorbitol-treated e mbryos allocated more cell volumes to prominent starch grains and nume rous lipid bodies. It is concluded that the specific control mechanism (s) of influence due to these compounds is probably different, as ref lected in the varying patterns of amyloplasts (or starch grains), prot ein- and lipid bodies visualized in the scutellar cells.