Morpho-physiological and antioxidant response to NaCl-induced stress in in vitro shoots of pomegranate (Punica granatum L.)

Abstract

The physiological and antioxidant response to salinity was studied in pomegranate (Punica granatum L.) by exposing in vitro growing shoots of the Italian variety Profeta Partanna to 125 or 250 mM NaCl for 10 and 20 days. 250 mM NaCl significantly reduced shoot length, leaf area and water content of the shoots, regardless the length of the salt treatment,with respect to the control and to the 125 mM NaCl treatment. After 20 days the shoots treated with 250 mM NaCl also showed a significant reduction in relative growth rate (RGR) together with marked necroses and abscission of the oldest leaves. Salt treatments significantly decreased the contents of chlorophylls and carotenoids in both exposure times, depending on NaCl concentration. Proline, total phenolic compounds and ellagic acid did not increase or even decrease with the salt treatments. The levels of lipid peroxidation decreased, ascorbate peroxidase (APX) activity significantly increased in both treatment times and concentrations, while guaiacol peroxidase (G-POD) activity significantly increased in shoots treated with 250 mM NaCl for 20 days suggesting the rapid involvement of APX in controlling the oxidative stress in this species, even at low salt concentrations, and a delayed complementary role of G-POD.