Mineral composition of and proline accumulation by zostera marina L. in response to environmental salinity

Abstract

Plants of Zostera marina L. collected in the field were grown for several weeks at different salinities under controlled conditions. After this period plants were harvested and the plant tissue water was analysed for proline, Na, K and Cl, which increased in response to seawater concentration as did osmolality. Proline accumulated up to 22 mmoll −1 tissue water at the highest seawater concentration. Proline synthesis or breakdwon was found to be slow in response to changes in environmental salinity. Nitrogen levels in Zostera were high (5% dry weight); a possible drain of proline on plant nitrogen is discussed. In vitro activity of malate dehydrogenase (MDH) was inhibited by NaCl; proline did not affect MDH activity, not even at 1 mol proline l −1. The role of proline in osmotic adaptation of Zostera marina is discussed.