Chloride Influx into Citrus Leaf Slices

Abstract

The influx of 36Cl has been measured in slices of citrus leaves. The influx increases with increasing external chloride concentration. The shape of the influx v. concentration curve depends on the nature and concentration of the accompanying cations (Na+ and K+). There is no evidence for the two distinct chloride transport systems reported by other workers. Chloride influx was not stimulated by light under aerobic conditions and was sensitive to 2,4-dinitrophenol at uncoupling concentrations. Under anaerobic conditions influx was maintained by light but severely limited by dark conditions. 3-(chlorophenyl)-I,I-dimethylurea did not affect aerobic influx and only high levels (5 X 10-OM) affected the anaerobic influx in the light. It is proposed that chloride influx is normally dependent on oxidative phosphorylation but that cyclic photophosphorylation may provide an alternative energy source. The implications of these results are discussed with respect to ionic relations of whole leaves and salinity damage.