β‐3‐DIMETHYLSULPHONIOPROPIONATE, PROLINE AND QUATERNARY AMMONIUM COMPOUNDS IN SPARTINA ANGLICA IN RELATION TO SODIUM CHLORIDE, NITROGEN AND SULPHUR

Abstract

Summary Spartina anglica Hubbard seedlings were grown in nutrient solutions containing various concentrations of sodium salts, as the chloride, sulphate and sulphide. Two levels of nitrate were supplied to plants growing on the sodium chloride and sodium sulphate series. At low sodium chloride concentrations, higher growth rates were found in plants grown on the high nitrate level. At higher salinities, growth was inhibited and the inhibition was similar for plants grown on either of the two nitrate levels. Shoot levels of β‐3‐dimethylsulphoniopropionate (DMSP) showed no significant increase with increasing sodium chloride concentrations, at both nitrate levels. This strongly indicates that DMSP does not act as a compatible solute in S. anglica, grown under salt stress. Contrary to DMSP, levels of proline and quaternary ammonium compounds (QAC's) increased significantly in response to sodium chloride, and were significantly higher in plants grown on the high nitrate concentration. The influence of nitrogen availability on the accumulation of N‐containing compatible solutes and growth is discussed. Growth rates of plants grown in increasing sodium sulphate concentrations were not inhibited. DMSP levels in plants did not increase with a sulphate increase in the medium. A significant inhibition of plant growth by sodium sulphide was found. Sulphate in the plant increased with increasing sulphide levels in the nutrient solution and an increase of DMSP was found at the highest sulphide level. A possible function of DMSP as storage for excess sulphur is discussed.