Responses of the Salt Marsh Succulent Bassia diffusa (Thunb.) Kuntze to Salinity and Inundation

Abstract

Bassia diffusa is a dominant species in the upper intertidal ranges of many salt marshes in South Africa, yet little information exists on its ecophysiology. This is important, as increased flooding or drought has been predicted for different salt marshes. The responses of this species to simulated climate conditions were studied. Plants were grown for 3 months under tidal-, submerged- and drought conditions each with five salinity levels from 0 to 46.4 g l−1. Under submergence, plants died within 1 month, irrespective of the salinity. Optimum growth occurred in tidal-treated plants at 18.5 g l−1, and decreased with increased salinity and drought conditions. Succulence of drought-treated plants decreased relative to that of tidal-treated ones; plants possibly used up water reserves under increasing drought stress. Reduced leaf mass was indicative of drought hardiness in the species. These adaptations would permit the species to survive season-long drought and salinity conditions. Anthocyanin concentration in leaves and stems was not sufficiently high to be osmotically important, suggesting alternative functions for anthocyanin accumulated in response to drought, and alternative mechanisms for osmoregulation. These remain the subject of further research. Results are significant for better salt marsh management under predicted conditions.