Effects of salt stress on plant water status, leaf gas exchanges and chlorophyll fluorescence of Pistacia atlantica Desf. versus Pistacia vera L

The productivity of agricultural systems and the ecological distribution of plants are strongly influenced by salinity in arid and semi-arid regions. In this context, two pistachio species, Pistacia vera L. (P. vera) and Pistacia atlantica Desf. (P. atlantica), have been exposed to NaCl (between 0 and 80 mM) to study the effect of salinity on plant water status, chlorophyll fluorescence and leaf gas exchanges. A specific pattern of response to salinity has highlighted different mechanisms of tolerance. Reductions in stomatal conductance (gs), photosynthesis (A) and total chlorophyll content (TCC) are similar to reductions in the relative water content (RWC) for both species and the NaCl treatments. The shape of the multiphasic fluorescence kinetics curves(OJIP) varies according to the severity of stress, indicating an earlier effect upon addition of NaCl for P. vera, but later in P. atlantica. The dynamic functioning of PSII depends on the toxicity by NaCl, altering plant water status, light conversion and CO2 assimilation by the mesophyll. The impact of salinity is clear at J and especially at I and P, which greatly increases for high NaCl concentrations, reflecting a decrease in the photochemical efficiency of PSII and electron transport. The chlorophyll fluorescence in P. atlantica reflects a lower sensitivity to salinity due to the maintenance of higher cell turgor, chlorophyll content and assimilation of CO2 than P. vera, explaining the agricultural practice based on its use as rootstock for P. vera for a better rusticity.