Department of Plant Sciences

Soil salinity is an increasing problem world-wide. High salt concentrations in root medium inhibit cell elongation and therefore plant growth. Under salt stress the pumping activity of the plasmalemma H+-ATPase is inhibited and may contribute to a weaker acidification of the apoplast and thus to growth inhibition. Therefore we investigated the influence of polyamines, which are known to play a role in salt-stress resistance, on the activity of the plasmalemma H+-ATPase. The concentrations of the polyamines spermidine (Spd) and spermine (Spm) in the maize hybrids Pioneer 3906 and SR 05 were influenced by salt stress with genotypic differences. While the polyamine concentrations in shoots were not changed, roots showed significantly lower spermidine (Spd) and higher spermine (Spm) concentrations under salt stress. The activity of the plasmalemma H+-ATPase was investigated using plasmalemma vesicles obtained from roots by two-phase partitioning. Spm had no effect on pumping activity of the plasmalemma H+-ATPase but Spd increased the net proton pumping significantly. The hydrolytic activity of plasmalemma H+-ATPase was not influenced by Spd. The synthesis of polyamines under salt stress may contribute to different salt resistance of maize genotypes.