Enhancing salinity tolerance in interspecific pistachio rootstocks through exogenous application of glycerol and sodium nitroprusside

This study examined the effects of foliar-applied glycerol (30 and 60 mM) and sodium nitroprusside (SNP) (100 and 200 μM) on the physiological and antioxidant responses of two interspecific hybrid pistachio rootstocks (Arota 1 and Arota 2) and their parental lines ( Pistacia atlantica and P. integerrima ) under varying salinity stress levels (0, 100, 200 mM NaCl). The salinity treatments were conducted weekly on one-year-old pistachio rootstocks in a controlled greenhouse for a duration of 90 days. The foliar application of glycerol and SNP was performed four times, with applications occurring every 15 days. Salinity stress caused a progressive decline in plant height, leaflet fresh weight, and dry weight across all rootstocks. Stimulant application, particularly SNP, mitigated these adverse effects in most rootstocks. Under salinity stress, proline and anthocyanin content increased while chlorophyll content decreased. Stimulants, especially SNP, alleviated these negative biochemical changes. Salinity significantly affected relative water content (RWC) and electrolyte leakage (EL), with the highest salinity level (200 mM) causing the greatest reduction in RWC and increase in EL. Glycerol, in particular, reduced EL under salinity stress. Additionally, salinity increased leaf sodium content and decreased potassium content, although stimulants did not significantly affect these mineral concentrations. Both salinity and stimulant treatments significantly influenced malondialdehyde content and the activities of catalase, peroxidase, and superoxide dismutase enzymes. Salinity stress elevated malondialdehyde levels and the activities of these antioxidant enzymes, with SNP effectively mitigating these effects. Overall, Arota 2 demonstrated the greatest salinity tolerance, particularly in terms of leaflet surface area, leaflet dry weight, RWC, and EL, followed by Arota 1.