Sucrose metabolism in stele and cortex isolated from roots of Pisum sativum

Abstract

Stele and cortex were separated from the region 6–24 mm from the tip of roots of seedlings of Pisum sativum L. that had been grown in the dark for 5 days. The activities of sucrose synthetase (E.C. 2.4.1.13) and sucrose phosphate synthetase (E.C. 2.4.1.14) in extracts of stele were 34 and 5·9 nmol product formed/min per mg protein, respectively. The corresponding figures for extracts of cortex were 17 and 5·2. Appreciable labelling of sucrose occurred when samples of either stele or cortex were incubated in [ 14C]glucose for 90 min. The labelling of sucrose after incubation of the tissues for 45 min in [ 14C]glucose followed by 45 min in glucose suggested some turnover of sucrose in the cortex but none in the stele. These results are discussed in relation to the control of sucrose metabolism in the root.