Comparative Study on the Effect of Water Stress and Rootstock on Photosynthetic Function in Pistachio (Pistacia vera L.) Trees

The aim of this study is to evaluate the effects of water deficit stress on chlorophyll fluorescence (CF) characteristics of photosystem II (PSII) and pigment contents in two rootstock seedlings (Pistacia atlantica L. and P. khinjuk L.). Three levels of soil water potential (Ψs) was used, including WWD (-0.05 MPa), MWD (-0.7 MPa) and SWD (-1.5 MPa). It was found that water stress increased the minimal fluorescence (F0), quantum yield baseline (F0/Fm) and decreased the maximal fluorescence (Fm) and maximum quantum yield of PSII photochemistry (Fv/Fm) parameters in dark adapted leaves. In light adapted leaves, a significant increase in non-photochemical quenching (NPQ) and thermal dissipation of light energy to heat (D) and a decrease in electron transport rate (ETR) and photochemical efficiency of photosystem II (ΦPSII) occurred. The results demonstrated a decline in photosynthetic pigments (Chla), (Chlb) and carotenoids (Car) content with increasing water stress, whereas there was no significant effect on Chl (a/b) and Car/(a+b) ratios. Our data revealed there was no different in terms of performance between the two rootstocks in the alteration rate of pigment contents and photosynthetic features against soil water deficit conditions.