Salt stress affects water relations, photosynthesis, and oxidative defense mechanisms in Solanum melongena L.

A greenhouse experiment was conducted to examine the salt-induced changes in some key physio-biochemical attributes in eggplant (cv. New Noble) plants. Eggplant plants were grown under varying levels (0, 50, 100, and 150 mM) of sodium chloride under greenhouse conditions supplied with natural light and other climatic conditions. Varying saline regimes in growth medium significantly reduced the shoot and root fresh and dry weights, shoot and root lengths, relative water content, chlorophyll a and b pigments, photosynthetic rate (A), water-use efficiency, stomatal conductance (g s ), leaf and root K+, total phenolics, total soluble proteins, activity of superoxide dismutase (SOD), and leaf water and osmotic potentials in all eggplant plants. However, in contrast, saline regimes of the root growing medium did not affect transpiration rate (E), internal CO2 concentration (C i ), C i /C a ratio, photochemical quenching (qP), non-photochemical quenching, efficiency of photosystem-II (F v /F m ), leaf and root Ca2+ as well as ascorbic acid (AsA) contents in eggplant. A significant increase was observed in leaf turgor potential, free proline and glycinebetaine contents, leaf and root Na+ contents, malondialdehyde and hydrogen peroxide (H2O2) contents and activities of peroxidase (POD) and catalase (CAT) in eggplant plants under varying saline regimes. Overall, salt-induced growth reduction in eggplant plants was found to be associated with high accumulation of Na+ in both roots and shoots, which adversely affected photosynthetic capacity, chlorophyll pigments, K+ and Ca2+ contents, H2O2 and AsA levels and activities of SOD, POD, and CAT.