Ion-exchange properties of the root cell walls isolated from a halophyte (Suaeda altissima L.) grown at different salinity conditions

摘要

Ion-exchange properties of root cell walls of 50-60 day-old plants (Suaeda altissima L.), which were grown in nutrient solution in the presence of different NaCl concentration (0.3, 250, 750 mM), were investigated. At all growth conditions the ion-exchange capacity of the cell walls were estimated at various pH values and at different solution salt concentrations. The total number of the cation-exchange and the anion-exchange groups in the cell walls were determined. It was established that independently of growth conditions there were four ionogenic groups in the polymeric structure of cell walls: three of them are cation exchangeable, and the forth one exchanges anions. The number of the functional groups of each type was estimated, and the corresponding values of pK_a~j were calculated. For all types of cation exchangeable groups arranged in the cell-wall structure the acid properties were enhanced by increasing concentration of electrolyte. It has been determined that at optimal salinity level (250 mM NaCl) the content of polygalacturonic acid groups in the cell walls is approx. 1.5 times greater than for plants grown at 0.3 and 750 mM NaCl. The results on the ion-exchange capacity of the root cell walls grown at different growth conditions are discussed in connection with the plant's adaptation to high salinity.