The Role of the Scutellum of Cereal Seedlings in the Synthesis and Transport of Sucrose

Abstract

Experiments with carbon-labeled glucose and fructose and organs of wheat and barley seedlings suggest that glucose is absorbed from the endosperm by the scutellum in germinating grain, simultaneously converted to sucrose, and transported in this form to the seedling. The main lines of evidence which support these conclusions are (1) the level of sucrose in the scutellum is high and that of the free hexose low; the reverse is true of the endosperm and, to a lesser extent, of the root and shoot,(2) both isolated and attached scutella absorb hexose readily and convert it largely to sucrose under a variety of condition; roots and shoots behave differently, (3) more ¹⁴C is accumulated into sucrose by isolated scutella than by those attached to seedlings, (4) the presence of enzymes which can effect conversion of hexose to sucrose has been demonstrated in scutellum extracts. This last body of evidence has also supported the view that sucrose synthesis in plants occurs by the pathway mediated by uridine diphosphate glucose as all the relevant enzymes have been detected in a single extract.