Differential effect of water salinity levels on gas exchange, chlorophyll fluorescence and antioxidant compounds in ex vitro date palm plants

In this study, the response to salt stress was evaluated in ex vitro acclimated date palm plants, regenerated from culture multiplication. The eighteen-month-old, were irrigated with 0 (control), 150, 300 or 450 mM NaCl solutions (high very high-water salinity). Photosynthesis parameters and antioxidant compounds determined at end of experiment leaves. At 150 NaCl, net CO2 assimilation rate internal concentration not impaired; while transpiration stomatal conductance decreased by 60 70%, respectively. By increasing concentrations, all gas exchanges decreased. Measurement chlorophyll fluorescence P700 redox state showed that PSII PSI machineries significantly enhanced under conditions. With remained unchanged compared control, some parameters, such as NPQ Y (NPQ), increased. photosystems functionality light intensity (PAR) dependent. Only low PAR, a significant increase observed. contrary, high most energy conversion functions reduced, especially those related PSI, indicating more susceptible for damage salinity than PSII. To overcome stress, plants mobilized cascade physio-biochemical pathways including activity proline biosynthesis. Overall, irrigation water, up mM, improves physiological performance which manage tolerate levels stress.