THE RESPONSE OF ATRIPLEX-AMNICOLA TO THE INTERACTIVE EFFECTS OF SALINITY AND HYPOXIA

The growth of Atriplex amnicola, its water and ion relations, and carbohydrate use were investigated in response to the interactive effects of salinity and root zone hypoxia in an experiment conducted in nutrient culture. One week of hypoxia in the root zone at both 50 and 400 mol m-3 NaCl caused the cessation of root growth, a reduction in shoot growth, and adversely affected water relations, but not ion relations or carbohydrate concentrations. Two weeks of hypoxia at 400 mol m-3 NaCl resulted in the death of root tips, a 20-fold increase in the resistance to water flow from the exterior of the roots to the leaves, and a further deterioration in water relations. There was also a doubling of Cl- concentrations in the xylem sap and a doubling of Na+ and Cl- concentrations in the leaves. An increase in the concentration of starch in the leaves, and sugars in the leaves, stems and roots, indicated that there were problems with carbohydrate use rather than supply. Under the prevailing conditions of low vapour pressure deficit, ion toxicity was the most probable cause of injury to A. amnicola in hypoxic solutions at high salinity. The response of A. amnicola to the interactive effects of salinity and hypoxia were similar to those reported for non-halophytes, but occurred at higher salinities.