Sucrose metabolism by roots of Pisum sativum

Abstract

The aim of this work was to relate [ 14C]-sucrose metabolism to the activities of sucrose synthetase and acid and alkaline invertases in roots of Pisum sativum. We fed [U- 14C]-sucrose to 5-day-old plants and then excised the apical 6 mm of the roots and dissected the regions 6–24 mm from the root apices into stele and cortex. The detailed distribution of 14C in these parts of the roots was determined at the end of the feeding period and after a chase. The data indicate that sucrose arriving in the stele is divided between storage, conversion to polysaccharide, and consumption in respiration, whereas sucrose arriving in the rest of the root is used in respiration or converted to polysaccharide or hexose so rapidly that little is stored. Fractionation of carefully prepared extracts of pea roots, tubers of Solanum tuberosum, and spadices of Arum maculatum showed that sucrose synthetase was recovered in the soluble fraction. The results are discussed in relation to the roles of the aforementioned enzymes.