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

In Colombia, the cape gooseberry is grown in salt-affected areas. 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 kept in 2 L pots and grown under greenhouse conditions. Plant leaves were analyzed 45, 55, 65 and 75 days after transplanting (DAT). 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, as compared to the control and 60 mM treated plants. At 60 mM NaCl, all determined leaf parameters and total plant DW were markedly reduced, as compared to non-salinized plants. The leaf proline content increased significantly during the evaluation period and tended to be higher with increasing NaCl concentrations, but without statistical differences. The TAA, measured as mu M 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 DAT of salt stress, the 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 the free radical scavenging activity, as compared to the control and the 60 mM NaCl treatment. All treatments showed a nearly 12% increase in the radical scavenging activity during the experiment's duration. In conclusion, cape gooseberry plants protect themselves from salinity (120 mM NaCl) stress by increasing leaf antioxidant activity, as confirmed by the higher radical scavenging activity, but not significantly with proline synthesis.