The effectiveness of zinc in alleviating salinity stress on pistachio seedlings

Introduction. Zinc (Zn) deficiency is a common nutritional disorder in Pistachio (Pistacia vera) which is grown on calcareous, saline and sodic soils. The effects of Zn amendment on the mineral nutrient uptake, the osmoregulation and the dynamics of phytohormones in pistachio under salt stress were investigated in the common conditions of Iran Materials and methods. A greenhouse study was conducted to evaluate the improving effects of zinc (0, 5, 10 and 20mg Zn kg(-1) soil) under saline (800, 1600, 2400 and 3200 mg NaCl kg(-1) soil) conditions on pistachio 'Badami' seedlings. The concentrations of potassium, calcium, sodium, magnesium, and Zn were determined by atomic absorption spectroscopy, and chloride was measured by titration Specific absorption rates (SAR) and specific utilization rates (SUR) of the minerals were calculated. Abscisic acid (ABA), 3-indoleacetic acid (IAA) and cytokinin contents were measured by HPLC, and the concentrations of osmoregulators (proline, glycine betaine and choline) were determined by spectrophotometry Results and discussion. The K, Ca and Zn concentrations and the IAA and cytokinin contents were reduced under Zn deficiency and salt stress. Increasing salinity in soil under Zn-deficient conditions generally decreased the SAR and SUR of K, Ca, Zn and Mg and ABA contents. However, these adverse effects of salinity were alleviated by increasing Zn levels up to 10 mg kg(-1) soil. The addition of Zn to the soil significantly decreased the proline and choline concentrations and increased the glycine betaine one of the pistachio seedlings exposed to salinity. Zinc treatments influenced the relationship between the relative growth rate (RGR) and the studied elements SARs and SURs. Conclusion. Overall, Zn improved plant growth under salt stress. According to the results obtained in this study, adequate Zn treatments can prevent the uptake and accumulation of sodium in the pistachio leaf and stem and improve both plant RGR and mineral nutrients absorption. Adequate Zn treatments also contribute to maintain the balance among seedling phytohormones even under salinity stress.