Effects of water stress and salinity on photosynthesis of pistachio

Abstract

Responses of Pistachia vera L. cultivar ‘Kerman’ to water stress were typical of those of xerophytic plants. Although photosynthesis declined with decreasing leaf water potential, plants continued to photosynthesize until a leaf water potential of as low as −5 MPa was reached. Some measure of turgor was maintained at very low leaf water potential (−6 MPa), which is a rarity in woody plants. However, at the lower range of leaf water potential, the plants were less efficient in their water use. Salinity levels up to 225 mM Cl − did not have any effect on photosynthetic rate or on stomatal and mesophyll resistances to the diffusion of CO 2. Chlorophyll content and leaf water, osmotic and turgor potentials were also unaffected by this level of salinity, despite significantly higher concentrations of Cl − and Na + in the leaves. When the salinity level was raised to 400 mM Cl −, a significant increase in leaf succulence diluted chloride and sodium concentrations (on a tissue-water basis) to values less than in leaves of plants treated with 225 mM Cl −.