Does proline application ameliorate adverse effects of salt stress on growth, ions and photosynthetic ability of eggplant (Solanum melongena L.)?

• Proline was applied as foliar-spray on eggplant under saline conditions.
• Salt stress reduced growth, gas exchange, and Na+ and K+ contents in eggplant.
• Foliar-applied proline improved shoot fresh weight of both eggplant cultivars.
• Water use efficiency was improved by foliar spray of proline in cv. Round only.

To counteract abiotic stress-induced adverse effects on plants, one approach is the application of exogenous potential osmoprotectants such as proline. This experiment was carried out to evaluate the effects of exogenous application of different concentrations of proline as foliar spray on growth, gas exchange characteristics, chlorophyll fluorescence and mineral ion accumulation of two eggplant cultivars viz., L-888 and Round grown under saline regimes. Fifty-seven days old plants were subjected for 15 days to varying levels of proline [0 (water spray), 10 and 20 mM] under control and saline (150 mM NaCl) conditions. Salt stress reduced growth, net CO2 assimilation rate (A), water use efficiency (A/E), efficiency of photosystem II (Fv/Fm), shoot and root K+ and Ca2+ ions of both eggplant cultivars. Exogenous application of proline counteracted the adverse effects of salt stress on shoot fresh weight of both eggplant cultivars and A/E ratio in cv. Round only. Overall, proline was not effective in alleviating the undesirable effects of salt stress on other morphological and physiological attributes of both eggplant cultivars under saline and non-saline regime.