The Solute and Water Relations of Agrostis Stolonifera Ecotypes Differing in Their Salt Tolerance

SUMMARY The water, ion, proline, amide, amino acid and quaternary onium contents of ecotypes of Agrostis stolonifera isolated from salt marsh, spray zone and inland habitats were determined over a range of external salt concentrations. When grown at high salinites the plants exhibited inhibition in the root water absorption and reduction in the shoot water content, these being most pronounced in the inland ecotype and least in the salt marsh ecotype. In the presence of salt the accumulation of Na + and Cl − in both shoots and roots was accompanied by a decline in tissue potassium content. At high salinities the increase in tissue ion content was greatest in the inland ecotype and least in the salt marsh ecotype. Proline, asparagine, glutamine, serine and glycine betaine showed increases in response to salinity, these being most pronounced in the salt marsh ecotype. The inland and spray zone ecotypes exhibited marked decreases in the aspartate and glutamate contents when grown at high salinities. With polyethylene glycol or mannitol in culture solutions, the salt marsh ecotype exhibited a greater ability to resist losses in shoot water content and to increase shoot proline, asparagine, glutamine and serine contents, than the inland and spray zone ecotypes. Changes in the solute and water status are discussed in relation to salt tolerance of the ecotypes.