Effects of varying sulphate and nitrogen supply on DMSP and glycine betaine levels in Spartina anglica

The relationship between sulphate, dimethylsulphoniopropionate (DMSP); and glycine betaine concentrations as well as the interaction with nitrogen sup ply in Spartina anglica Hubbard was investigated. Several studies have alre ady shown that nitrogen affects levels of DMSP and glycine betaine in Spart ina. It has further been suggested that sulphate is important to the growth of the salt marsh grass Spartina. We hypothesised that DMSP might be invol ved in a high sulphur requirement. It was further hypothesised that the eff ect of sulphate would depend on nitrogen supply. S. anglica shoots were tre ated with a range of nutrient solutions containing four different sulphate treatments, 0, 80, 800 or 1600 mu M and two different nitrogen levels, 0 or 2 mM ammonium nitrate. Plant parts were analysed for DMSP and glycine beta ine, as well as total nitrogen and total sulphur. Plants were analysed for proline as well but levers were very low or non-detectable and patterns wer e not consistent. Total sulphur was affected by both the nitrogen and sulph ate treatments while total nitrogen was affected by the nitrogen treatments only. Sulphate had no effect on growth (leaf length or biomass), but nitro gen increased growth of S. anglica shoots. Levels of DMSP and glycine betai ne were unaffected by increased sulphate supply. Nitrogen significantly dec reased concentrations of DMSP and glycine betaine. However, due to increase d biomass production, total amounts of DMSP and glycine betaine per plant w ere significantly higher in the 2 mM nitrogen treatments. The data suggest that pools of DMSP in roots and stems are more important than previously th ought. (C) 2000 Elsevier Science B.V. All rights reserved.