Effect of Sodium Chloride on Expansion Rates and Invertase Activity of Leaves

Abstract

The rate of expansion and the invertase (�-fructofuranosidase, EC 3.2.1.26) activity of leaves of two relatively salt-sensitive plants, Phaseolus vulgaris and Zea mays, decreased with increasing concentrations of NaCl from 0 to 50 mM in nutrient solutions supplied regularly in a porous growth medium. Sucrose concentrations in the leaves were higher and reducing sugar concentrations were lower at the higher concentrations of NaCl. Growth of leaves, invertase activity, and concentrations of reducing sugar and sucrose changed much less, if at all, with NaCl treatment of Hordeum vulgare, a reasonably salt-tolerant plant. Cellulase activities were not different in bean leaves from plants grown on different NaCl concentrations. The Km values for sucrose for invertase from bean leaves were 5.8, 8.1 and 10.4 mM for plants grown on 0, 20 and 50 mM NaCl respectively. NaCl at concentrations up to 200 mM did not affect the in vitro activity of invertase from barley, bean or maize leaves.