Zinc soil application enhances photosynthetic capacity and antioxidant enzyme activities in almond seedlings affected by salinity stress

Zinc is a critical mineral nutrient that protects plant cells from salt-induced cell damage. We tested whether the application of Zn at various concentrations [0, 5, 10, or 20 mg kg(-1)(soil)] would protect almond (Prunus amygdalus) seedlings subjected to salt stress (0, 30, 60, or 90 mM NaCl). All concentrations of Zn, particularly the application of 10 and 20 mg kg(-1), increased the net photosynthetic rate, stomatal conductance, the maximal efficiency of PSII photochemistry, and a proline content in almond seedlings grown under salt stress; 20 mg(Zn) kg(-1) was the most effective concentration. The activity of superoxide dismutase showed a significant increase under salinity stress and Zn application. The catalase activity decreased in the salt-treated seedlings, but recovered after the Zn treatment. Our results proved the positive effects of Zn on antioxidant enzyme activity scavenging the reactive oxygen species produced under salt stress.