Salt tolerance in Sporobolus virginicus: the importance of ion relations and salt secretion

Abstract

Summary The role of ion relations and salt secretion in salt tolerance in the halophytic, C4 grass, Sporobolus virginicus (L.) K unth , was investigated. Plants were subjected to 0.2, 20, 40, 60 and 80% sea water for 12 weeks. There was no significant growth stimulation with increase in salinity from 0.2 to 20% sea water, while further increases to 80% sea water significantly reduced total biomass accumulation and growth of roots and shoots. The predominant ions secreted by salt glands were Na+ and Cl− with smaller amounts of K+, Ca2+ and Mg2+. Increase in substrate salinity from 0.2 to 20% sea water significantly increased secretion of Na+ and Cl−, but had no effect on tissue concentrations of these ions. Further increases in substrate salinity from 20 to 80% sea water had no effect on secretion of Na+ and Cl− but increased tissue concentrations of these ions. High rates of Na+ secretion and greater retention of K+ at high salinities resulted in stable Na+/K+ ratios in all treatments. Concentrations of proline in roots and shoots increased significantly with salinity increase. In all treatments, leaf water potentials were lower than media water potentials. Salt secretion was effective in maintaining salt balance at low to moderate salinities and ineffective at high salinities.