Effect of salinity on growth and accumulation of organic and inorganic solutes in the leguminous plants Alhagi pseudoalhagi and Vigna radiata

The response of two leguminous plants Alhagi pseudoalhagi and Vigna radiata to seawater salinity was studied over a period of 30 d. The growth of Vigna radiata was markedly and gradually reduced by increasing salinity levels, whereas that of Alhagi pseudoalhagi was promoted at 9.1 and 16.2 dS m^-1 salinity but then was slightly reduced at 28.2 dS m^-1 salinity. These results indicate that Alhagi pseudoalhagi belongs to the group of halophytic plants. Seawater salinity caused changes in the membrane permeability measured as electrolyte leakage in both plants. Alhagi pseudoalhagi maintained a lower membrane permeability than Vigna radiata. With increasing salinity levels, the membrane permeability decreased in Alhagi pseudoalhagi, whereas, in Vigna radiata it slightly increased at 9.1 dS m^-1. The leaf water potential and the osmotic potential decreased in both plants along with the seawater salinity levels. However, the turgor potential and osmotic adjustment in Alhagi pseudoalhagi were maintained at a higher level than in Vigna radiata. The contributions of organic and inorganic solutes to the osmotic adjustment differed: Alhagi pseudoalhagi achieved osmotic adjustment through Cl^- and Na⁺ uptake from the substrate, while the contribution of K⁺, Ca²⁺, and organic solutes to the osmotic adjustment was limited. These results suggest that the differences in salt tolerance between Alhagi pseudoalhagi and Vigna radiata can not be due to differences in specific-ion effects, but may be related to some factors involved in membrane permeability and osmotic adjustment.