Photosynthesis Properties and Ion homeostasis of Different Pistachio Cultivar Seedlings in Response to Salinity Stress

Understanding mechanisms of salt tolerance, physiological responses to salt stress, and screening genotypes for breeding programs are important scientific issues remained to be investigated in pistachio. Therefore, current study was carried out to investigate response of different pistachio cultivars (G1, G2, Kaleghochi and UCB1) to salinity treatments (0.6 as control, 10, 20 dS m-1 using saline underground water) as a factorial experiment based on randomized complete block design with three replications in greenhouse of Iranian Pistachio Research Institute (Rafsanjan) in 2014-2015. Some physiological and nutrition properties of the pistachio cultivars measured in this study. Results showed decreased stomatal conductance, photosynthesis rate, chlorophyll content, and Fv/Fm in response to salinity treatments. The main cause of these changes was related to the altered ion contents along with the competition among ions for being absorbed by plant. Despite of sufficient amount of potassium in the soil, high concentrations of sodium and other associated elements such as calcium and magnesium decreased the ability of pistachio plants to absorb adequate amount of vital ions such as potassium. As a result of sodium accumulation and deficiency of potassium, K+/Na+ ratio was decreased in pistachio leaves. Consequently, toxicity of sodium ions in the plant cells reduced stomatal conductance and the rate of photosynthesis. Comparison between cultivars showed that for the most of the traits the difference between control and moderate salinity (10 ds m-1) in all cultivars was not significant. However, G2 cultivar showed higher ability to accumulate potassium and absorbed lower concentration of sodium, calcium, and magnesium under sever salinity treatment (20 ds m-1). These result suggested that G2 could be considered as a potential tolerant cultivar for cultivation in saline area.