Comparison of photosystem II efficiency in four Pistachio rootstocks under drought stress using chlorophyll fluorescence technique

In a greenhouse experiment aimed to compare drought resistance, photosystem II efficiency was evaluated using chlorophyll fluorescence parameters and chlorophyll content of four pistachio (Pistacia vera L.) rootstocks based on a completely randomized design (CRD) as factorial with drought treatment (PEG Hoagland solution) at four levels (0, -0.5, -1 and -2 MPa) and four pistachio rootstocks(Abareqi, Badami-Rize-zarand, Qazvini and sharakhs). After three months of stress commencement, chlorophyll fluorescence and related transients (F0¡ Fv¡ Fm¡ Fv/Fm¡ Area¡ VJ¡ PI¡ Fv/F0 and RC /ABS) were measured by fluorimeter. Chlorophyll a, b, total chlorophyll content and total dry weight of plants were measured at the end of experiment. Results showed that chlorophyll fluorescence parameters were influenced by drought stress. The parameters of Fv¡ Fm¡ Fv/Fm and PI were decreased with increasing of drought stress level. PI, a photosynthesis efficiency index, was reduced by 90% at the highest level of drought intensity. This parameters showed the most correlation with total dry weight (R2= 0.61) so it can be used as an effective parameter to identify drought susceptible or tolerance rootstocks. Our results showed that there is a significant correlation between chlorophyll content, chlorophyll fluorescence parameters and total dry weight under drought stress. Results of the experiment revealed that sarakhs and Badami-Riz-zarand could be categorized as more drought resistant based on their higher photosynthetic capacity and dry weight as compared to Abareqi.