Size of the Microbody Population in Sunflower Cotyledons During the Transition in Cotyledonary Microbody Function

Microbody fractions not contaminated by mitochondria, plastids, or protein bodies were isolated from sunflower cotyledons during the transition of the cotyledonary microbody population from glyoxysomal to leaf peroxisomal function. In these microbody fractions, specific enzyme activities could be determined based on microbody protein content. The amount of microbody protein per cotyledon was estimated from the specific and total activities of isocitrate lyase and glycolate oxidase. This can be considered to be a relative measure of the size of the cotyledonary microbody population (number of microbodies per cotyledon). The amount of microbody protein per cotyledon remained constant over most of the transition period, declining only during the final stage. This result suggests that there is no pronounced and selective degradation of glyoxysomes during the transition in cotyledonary microbody function.