Physiological studies of salt tolerance in Plantago maritima (L.)

Abstract

The studies described in this thesis were concerned with evaluating the salt tolerance mechanisms of Plantago maritima (L.). This species, a perennial herb, is found growing in various habitats including saline coastal environments where it can withstand soil salinity concentrations of up to 300mM NaCl. Three populations of Plantago maritima were studied: an upper saltmarsh, a lower saltmarsh and a sea-cliff population. The comparison of populations from different habitats, and presumably different in vivo saline conditions, was hypothesised to lend itself to the determination of the salt tolerance mechanisms of this species. Growth, ion accumulation, ion efflux and non-structural carbohydrate concentrations were investigated for Plantago maritima plants grown in up to six different NaCl treatments over one and nine weeks. Growth was measured in terms of weekly fresh weight, leaf length, root length and final dry weight and water content. Shoot and root ion contents and ion efflux were determined by flame photometry, while soluble and insoluble carbohydrate contents were determined using High Performance Liquid Chromatograohy and enzyme analysis respectively.