The effect of benzyl adenine and nitrogen on some physiological parameters of pistachio seedlings in saline conditions

Soil and water salinity is considered an important limiting factor for growth in many parts of the world especially in arid and semi-arid areas. Plant growth is restricted by salt stress like many other abiotic stresses. According to the relative tolerance of pistachio plant to salinity and large areas of saline soils in the country, it seems that pistachio is a suitable plant for cultivation in these areas. Since the production and activity of plant hormones such as cytokinins is influenced by environmental stresses and nutrient elements and considerig the soil salinity of pistachio orchards in kerman province and the important role of nitrogen in the production and exportation of cytokinin from roots to shoots this research for the first time investigates the role of benzyl adenine hormone (cytokinin) and nitrogen under salt stress on physiological parameters and osmotic regulators of pistachio seedlings (Pistachia vera L.).
In order to evaluate the effect of different levels of nitrogen and benzyl adenine on some physiological and osmotic regulators parameters of pistachio seedlings, cv. Badami Zarand in saline conditions (sodium chloride), a factorial experiment was carried out in a completely randomized design with three replications in the greenhouse. Treatments were consisted of salinity (0 and 2000 mg NaCl per kg soil), nitrogen (0 and 100 mg N kg-1 soil as NH4No3), and benzyl adenine hormone (0, 250 and 500 mg l-1).
The results showed that application of 500 mg per liter benzyl adenine under salt stress increased dry weight of plant more than 2 folds compared to control. Also, with increasing salinity, the content of chlorophyll a, chlorophyll b and total chlorophyll was decreased. However application of nitrogen and benzyl adenine together, increased these parameters by 77, 72 and 52 percent, respectively. Also, carotenoids are affected by the treatments were increased by 78 percent. Although salinity reduced chlorophyll fluorescence index 31 percent, the application of nitrogen and 500 mg per liter benzyl adenine together could improve somewhat the effects of salinity and increased this photosynthetic parameter by 43 percent. Also, the results showed that proline and soluble sugars contents (osmotic regulators) increased with application of nitrogen and benzyl adenine (500 mg per liter), but combined application of these treatments increased osmotic regulators content by 78 and 59 percent compared to control, respectively.
The ratio of K/Na and Ca/Na were also significantly reduced with increasing salinity, but application of 500 mg per liter benzyl adenine increased these parameters by 100 and 40 percent, respectively.
According to the results, it is concluded that the nitrogen and benzyl adenine with improving of physiological and osmotic regulators parameters, increased the ability of pistachio seedlings to resistance to salinity stress and thus recommended to performe this test on maturity pistachio trees and if increase the quality and quantity of product to be recommended to farmers.