Response of Pistacia vera L. and Pistacia atlantica Desf. to light and water stress in arid bioclimate

Arid areas are often exposed to water stress and high light intensity. Climate change accentuates the situation. Therefore, this study aims to investigate the effects of increasing photosynthetic active radiation intensity ranging from 0 to 1200 µmole photon m−2 s−1 on net photosynthesis, and chlorophyll fluorescence in Pistacia vera L. and Pistacia atlantica Desf. in irrigated and stressed conditions. Plants aged of six months were grown in pots 25 L in the greenhouse. After 23 days of water withholding, net photosynthesis, chlorophyll fluorescence (OJIP) were measured at different PAR levels (0, 200, 400, 600, 800, 1000, and 1200 µmole photon m−2 s−1). Compared with the irrigated seedlings, those in the stressed treatment showed significantly reduced net photosynthesis, stomatal conductance, transpiration rate, and mesophyll efficiency for different PAR intensities (p < 0.005). Both species showed high water uses efficiency. The PAR did not influence the chlorophyll fluorescence at step O. On the contrary, for maximal fluorescence at the P step, P increased as PAR increased. It reached its high value at 1000 µmole photon m−2 s−1 (50% higher). At this level, a difference between P. vera irrigated and stressed seedlings was noted particularly in P. vera stressed seedlings which decreased compared to irrigated ones (50% lower). These results showed that the OJIP curve was typical in PAR 1000 µmole photon m−2 s−1. However, it was not completely constituted in low photosynthetic photon flux density values (PPFD) (0 to 800 µmole photon m−2 s−1and high PPFD values (1200 µmole photon m−2 s−1). The ecophysiological parameters also varied with different applied PPFD intensities. The results clearly showed that the PPFD value must be considered before estimating physiological parameters. Both species, of a great economic interest can be used to rehabilitate arid lands and protecting them from erosion and desertification.