Phenylalanine and Calcium Nitrate Alleviate Cold Tolerance of Pistacia vera L. Seedlings

To study the effects of different concentrations of phenylalanine, and calcium nitrate under cold stress on Pistacia vera L. 'Abbas Ali' cultivar seedlings, a factorial experiment was performed with three factors of phenylalanine at three levels of calcium nitrate, and temperature based on a completely random design with three replications. The findings demonstrated that the effects of phenylalanine, calcium nitrate, temperature, as well as their interactions, were significant for all studied features. By simultaneous use of 2.5 mM of phenylalanine, and 5 ppm of calcium nitrate, electrolyte leakage reduced by 19% compared to the control sample at -3°C. Furthermore, when the temperature reduced from zero to -3°C, the concentration of proline increased from 2.3 to 3.1 μg g⁻¹ fw compared to the control seedlings. By simultaneous use of the highest concentrations of phenylalanine, and calcium nitrate, phenolic compounds, and soluble sugar increased. However, the interactions of phenylalanine×calcium nitrate, cold×phenylalanine, and phenylalanine×calcium nitrate×cold were not significant on the content of proline. A significant positive correlation was between proline, and soluble sugar at the probability level of 1% (r=0.87**). A significant negative correlation was between electrolyte leakage and chlorophyll fluorescence at the probability level of 1% (r=- 0.68**).