Comparison of starch, ADP-glucose pyrophosphorylase and starch synthase levels in non-embryogenic cells and developing embryos in Hevea brasiliensis

Abstract

Summary Sucrose, glucose, fructose and starch levels, and ADP-glucose pyrophosphorylase (EC 2.7.7.27) and starch synthase (EC 2.4.1.21) activities were studied in an embryogenic strain of Hevea brasiliensis during the periods of multiplication of proembryogenic clusters and development of somatic embryos. For comparison, a non-embryogenic strain was also investigated. The development of somatic embryos was studied on a medium containing polyethylene glycol and abscisic acid and a medium devoid of both. First, a correlation between ADP-glucose pyrophosphorylase activity and starch accumulation was shown during the multiplication period of proembryogenic clusters. Second, starch accumulation in somatic embryos was observed at the end of the developmental period on the medium containing polyethylene glycol and abscisic acid but not on the medium devoid of these substances. In non-embryogenic cells, starch levels were similar whatever the culture conditions. However, this difference in starch content was not reflected in the starch biosynthetic capacity inferred from the ADP-glucose pyrophosphorylase and starch synthase activities, which were similar in the two culture conditions and in somatic embryos and non-embryogenic cells. Also, somatic embryos were more numerous, especially at the torpedo stage, on the medium containing polyethylene glycol and abscisic acid than on the medium devoid of these substances.