Reduced Starch Content and Sucrose Synthase Activity in Developing Endosperm of Barley Plants Grown at Elevated Temperatures

Abstract

Starch accumulation is reduced when endosperms develop at elevated temperatures. Reduced starch deposition does not appear to be due to limiting assimilate levels during the grain filling period; on the contrary, endosperm sucrose may even be increased at the elevated temperature. Results indicate that elevated temperatures significantly reduce the activity of the sucrose cleavage enzyme UDPsucrose synthase (EC 2.4.1.13), found in the endosperm during grain development, and that these effects may be initiated by a relatively short period of thermal stress applied close to anthesis. It would appear that, when developing barley ears are exposed to elevated temperatures, there is an irreversible reduction in the capacity of the endosperm to convert sucrose to starch, caused by a decrease in the activity of at least one of the enzymes involved in this conversion pathway.