Ion Exchange Properties of the Root Cell Walls Isolated from the Halophyte Plants (Suaeda altissima L.) Grown Under Conditions of Different Salinity

Abstract

Ion exchange properties of root cell walls of 50- to 60-day-old plants of Suaeda altissima L., grown in nutrient medium in the presence of different NaCl concentration (0.3, 250, 750 mM) were investigated. For all growth conditions, the ion exchange capacity of the cell walls was estimated at various pH values and at different salt concentrations. The total amount of cation and anion exchange groups in the cell walls was determined. It is shown that four ionogenic groups in the polymeric structure of the halophyte cell walls are always observed independently of growth conditions: three are cation exchangeable, and one exchanges anions. The amount of the functional groups of each type is estimated, and the corresponding values of pK a j are calculated. It is shown that acidic properties are enhanced for all types of cation exchangeable groups by increasing electrolyte concentration (NaCl) in the nutrient solution. At the level of ‘optimal salinity’ (250 mM NaCl) the amount of polygalacturonic acid groups in cell walls is approx. 1.5 times greater than for the plants grown at either low (0.3 mM NaCl) or high salinity (750 mM NaCl). Ion exchange capacities of the root cell walls of the halophytes grown in different salt concentration are discussed in terms of S. altissima adaptation to salt stress.