Effect of Drought Stress on Chlorophyll Fluorescence, Chlorophyll Contents and Chlorophyll Index in Four Pistachio Seedling Rootstocks

Chlorophyll fluorescence is a non-destructive tool for estimation of the efficiency of photochemistry and photosynthesis status in plants and has extensively been used in assessing plants response to environmental stresses. The aim of this study was to evaluate the effect of drought stress on chlorophyll fluorescence, chlorophyll content, chlorophyll index, and biomass in four pistachio seedling rootstocks grown under greenhouse conditions. The rootstocks were Pistacia vera cv. Badami-e-Zarand, P. vera cv Ghazvini, P. vera cv. Sarakhs, and P. mutica. The results showed that water stress reduced F_V/F_m ratio (which is an indicator for the maximum efficiency of photosystem II), chlorophyll contents, and biomass in plants. Highest amount of F_V/F_m ratio was observed in the control treatment (full irrigation) and had significant difference with the severe stress treatment. In most cases, there was no significant difference among studied rootstocks, except P. mutica that showed the highest quantum yield of PSII. The maximum and minimum chlorophyll concentrations in irrigation treatments were also obtained in the control and severe stress treatments, respectively. The effects of genotypes on the chlorophyll contents (a, b, total and CCI) were significant and the highest and the lowest of these parameters belonged to P. mutica and P. vera cv. Sarakhs, respectively. In the case of shoot, root, and leaf dry weight, the rootstocks P. mutica and P. vera cv. Badami showed lower reduction under water stress. Based on the results, water stress had negative effects on pistachio seedling rootstocks and P. mutica showed more resistance than the other genotypes.