The effects of the interaction between salinity and nitrogen limitation in Agrostis stolonifera L.

Salt-tolerant Agrostis stolonifera ecotypes commonly grow on upper salt marshes, environments regarded as having a limited nitrogen supply. The interaction between salinity and nitrate supply limitation was studied in two ecotypes of A. stolonifera, one isolated from an upper salt marsh and one from an inland habitat. The ion, amino acid, glycine betaine and sugar contents of the two ecotypes were determined over a range of external salt concentrations and levels of nitrate supply. In vivo nitrate reductase activity was also measured. Several low molecular weight nitrogenous compounds accumulated in the salt-stressed plants. Nitrogen supply limitation had a great effect on the way in which the plants responded to salt stress. In particular, the concentrations of the soluble organic nitrogenous compounds were reduced. The results are discussed with respect to the salt marsh environment, and possible models for cytoplasmic osmoregulation are presented.Acknowledgements: One of us (MJH) gratefully acknowledges the receipt of a research studentship from the Science Research Council, U.K. We would also like to thank Mrs E. E. Griffiths for skilled technical assistance, and Dr I. Ahmad for help with the amino acid analysis.