NITROGEN METABOLISM OF HALOPHYTES I. NITRATE REDUCTASE ACTIVITY IN SUAEDA MARTIMA.

The present paper reports a study into the activity of nitrate reductase in plants of Suaeda maritima. The growth of S. maritima in the upper salt-marsh appears nitrogen limited, going from the upper to lower marsh there is a three-fold increase in total nitrogen of the plants. Nitrogen status and the activity of nitrate reductase are related. Plants from the lower marsh contain a fifty times higher level of enzyme than those from the upper marsh. By feeding nitrate to plants at different sites in the marsh it was possible to induce high nitrate reductase activity in plants that previously contained low levels of the enzyme. At all sites there is an equal potential to induce nitrate reductase. The induction experiments with plants in situ suggest that in this marsh nitrate availability is the main factor limiting the growth of S. maritima in the upper marsh. [ABSTRACT FROM AUTHOR]