Salinity effects on proline accumulation and total antioxidant activity in leaves of the cape gooseberry (Physalis peruviana L.)

The effect of increasing sodium chloride (0, 60 and 120 mM NaCl) stress was investigated on the growth, proline content and total antioxidant activity (TAA) in leaves of cape gooseberry plants grown under greenhouse conditions. Plants were cultivated in 2 L pots and supplemented with nutrient solution for 75 days. Plant leaves were analyzed 45, 55, 65 and 75 days after transplanting. The vegetative growth (measured as total plant and organ dry weight [DW], leaf number and leaf area, as well as plant height) was significantly lower at 120 mM NaCl. At 60 mM NaCl, all determined leaf parameters and total plant DW were markedly reduced compared to non-salinized plants. Leaf proline content increased during the period of evaluation, being between two- and three-fold higher in plants at the 120 mM NaCl level compared to control plants. TAA, measured as µM Fremy's salt per g-1 FW, increased constantly during the evaluation period and from day 55 was significantly higher than in leaves of non-salinized plants. After 75 days of salt stress, both TAA and proline content did not differ between the 60 and 120 mM NaCl treatments. For all sampling dates, the 120 mM salt concentration significantly enhanced free radical scavenging activity compared to control and the 60 mM NaCl treatment. All treatments showed a nearly 12% increase in the radical scavenging activity during the experiment’s duration.