An experiment was conducted in pots of 25 kg capacity to study the effect of saline irrigation (EC 0,5,10,15 and 20 dSm-1) prepared by mixing NaCl, NaSO4, CaCl and MgCl2 in 3:1 ratio of chloride and sulphate on gas exchange traits, membrane stability, chlorophyll stability index and osmolytic defense mechanism in Ziziphus rotundifolia and Ziziphus nummularia species of Indian jujube (Z.mauritiana). Result showed that net photosynthetic rate (PN), transpiration (e) and stomatal conductance were comparatively lower in Ziziphus nummularia, which further declined with increasing level of saline irrigation water. Chlorophyll stability and membrane stability also declined significantly in salt stress, with higher magnitude in Ziziphus nummularia. The activity of proline anabolic enzymes; Δ1-Pyrrolline-5-carboxylate reductase, Δ1-Pyrrolline-5-carboxylate synthetase and Ornithine-δ-aminotransferase were recorded higher in Ziziphus rotundifolia with decrease in proline dehydrogenase. The sodium content was observed higher in roots of Ziziphus rotundifolia and leaves of Ziziphus nummularia. Therefore, it is suggested that salt tolerance mechanism was more efficiently operative in Ziziphus rotundifolia owing to better management of physiological attributes, osmolytic defense mechanism and restricted translocation of sodium from root to leaves along with larger accumulation of potassium in its leaves.
Keywords: Cations; Gas exchange; Photosynthesis; Proline metabolism; Salinity.