Effect of Salinity on Physiological and Biochemical Parameters of Leaves in Three Pomegranate (Punica Granatum L.) Cultivars

Salinity is one of the most important abiotic stresses affecting crop yield. It is important to exploit pomegranates’ potential against salts because they are considered beneficial plants for human health due to their antioxidants and they are often exposed to severe salinity stress in the field. Three pomegranate cvs. were chosen as model plants for assessing the impact of different salt stress in the cultivation. The aim of this study was to evaluate the physiological and biochemical response of three pomegranate varieties (Punica granatum L.) (Wonderful, Ermioni, and Grenada) under different saline conditions. The plants were grown in a sand/perlite substrate in a 1:1 ratio and, throughout the experiment, were irrigated with a Hoagland nutrient solution, modified to contain four concentrations (0, 25, 50, and 75 mM) of NaCl, KCl, and K2SO4. At the end of the experiment, we measured the (a) concentrations of carotenoids and porphyrin of leaves; (b) phenols and flavonoids contents, and antioxidant capacity of leaves; (c) lipid peroxidation level; (d) leaf water potential; and (e) proline concentration. Ermioni contained the maximum concentration of proline phenols and flavonoids and antioxidant capacity in all salts. Furthermore, reductions in chlorophyll and carotenoid concentration were recorded in all cultivars. Grenada possessed the lowest porphyrin concentration. In conclusion, our results showed that Grenada was the most salt-susceptible cultivar. Salinity treatment triggered the enhancement in lipid peroxidation in the sensitive cultivar, while no change in lipid peroxidation level was observed in the tolerant cultivars. These data provide further support to the hypothesis that a mechanism exists that excludes salinity from the roots of tolerant cultivars, as well as an internal mechanism of tolerance that minimizes the accumulation of lipid peroxides through a higher proline content related to osmoregulation and membrane stabilization.