Differential response strategies of pomegranate cultivars lead to similar tolerance to increasing salt concentrations

Two-year-old pomegranate (Punica granatum L.) plants of the commercial cultivars Wonderful (W) and Parfianka (P) were subjected for 47 days in the substrate to four salt concentrations (0, 100, 150 and 200 mM NaCl), in order to evaluate their strategies in terms of Na+/Cl− translocation and tissue/organ compartmentalization, as well as of antioxidant and osmoprotectant mechanisms. Regardless of salt concentrations, mature leaves of both cultivars accumulated high concentrations of Na+ and Cl−, showed strong decreases in PSII photochemical efficiency and finally died, suggesting that a salt-induced ion-specific toxicity occurred. Conversely, these detrimental effects occurred later and at a lower magnitude in young leaves, likely as a consequence of a Na+ and Cl− compartmentalization in mature leaves and roots. Differential responses between cultivars was, instead, observed in terms of biochemical pathways, with P plants more activating osmolyte accumulation at root and leaf level (e.g. proline, abscisic acid and carbohydrates), antioxidant system (e.g. superoxide dismutase and catalase activity) and macronutrient distribution than W plants. However, both cultivars resulted salt-tolerant, as confirmed by their ability to safeguard biomass production.