Growth responses, leaf water and osmotic relations, and tissue ionic and organic solute contents of Sporobolus virginicus (L.) Kunth, grown under solution culture in salinities of up to 450 mM NaCl, were studied. Shoot growth was stimulated by intermediate salt levels, concurrent with both an accumulation of Na+ and Cl− in shoots and a slight increase in shoot succulence. Root growth was stimulated at salinities of up to 450 mM NaCl, Osmotic adjustment of shoots was predominantly due to Na+, Cl−, and soluble carbohydrate accumulation, though a slight reduction in shoot succulence may have played a minor role at high salinity. Shoot Na+ and Cl− accumulation was tightly controlled, not exceeding levels required for osmotic adjustment, due in part to ion secretion by leaf salt glands. Shoots were selective for K+ over Na+, maintaining fairly constant K+ concentrations with increasing salinity, resulting in relatively high K+/Na+ ratios at high salinity. Increasing NaCl stimulated the accumulation of K+ in roots, which may have acted as a reservoir of K+ for shoots at high salinity. Glycinebetaine, and to a lesser extent proline and trigonelline, accumulated in shoot tissues with increasing salinity, though trigonelline concentrations were insufficient to be osmotically significant. Accumulation was closely associated with increases in shoot sap osmolality. It is proposed that glycinebetaine may act as a compatible solute in S. virginicus, as levels were sufficiently high to effect total osmotic adjustment of the cytoplasm at high salinity.
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