Utilization of Exogenous Sugars for Biosynthesis of Carbohydrates in Germinating Pollen

Abstract

A study has been made of the utilization of C14-labeled D-fructose and sucrose by germinating pollen of Lapageria rosea and Impatiens oliveri. Sucrose was shown to be the main carbohydrate produced by the L. rosea pollen germinated in C14-labeled D-fructose solution. Two radioactive polysaccharides, starch and [beta]-1, 3-D-glucan, were also synthesized by the pollen. The same metabolic products were obtained when I. oliveri pollen was germinated in C14-labeled D-fructose solution. When Lapageria pollen which had been germinated in nonradioactive sucrose was transferred to a solution containing D-mannitol and C14-labeled sucrose, pollen tube growth ceased. Under these conditions the formation of [beta]-1,3-D-glucan, but not starch, occurred. The fact that the material in the pollen tubes which gives a positive callose stain with resorcin blue is degraded by a specific [beta]-1,3-D-glucanase indicates that pollen tube callose is a [beta]-1,3-D-glucan.