Salicylic Acid and Iron Reduce Salt-Induced Oxidative Stress and Photosynthesis Inhibition in Strawberry Plants

Oxidative stress is usually induced under saline conditions, adversely affecting yield and crucial physiological processes in plants. The present work was conducted to investigate the beneficial effects of salicylic acid (0.25 mM) and chelated iron (2 ppm) on strawberry tolerance to oxidative stress triggered by NaCl toxicity. Salt stress (80 mM NaCl) remarkably reduced stomatal conductance and photosynthetic pigment levels in stressed plants compared to unstressed ones. The application of SA and chelated iron was more efficient for gas exchange and pigment production. The SA and/or iron also attenuated the salinity-induced inhibitions on maximum fluorescence (F-m), maximum photochemical efficiency of photosystem II (phi(P0)), quantum yield for electron transfer (phi(E0)), quantum yield for the reduction of the end electron acceptors at the PSI acceptor side (phi(R0)), performance index (PIABS) and reaction centers density (RC/CS), while it reduced the minimum fluorescence (F-0) and the quantum yield of energy dissipation (phi(D0)). Additionally, significant increases in hydrogen peroxide levels (H2O2), lipid peroxidation (MDA), and cellular solute leakage (EL) were revealed under saline conditions. However, this damage was alleviated by the application of SA and iron supplementation. Furthermore, SA and/or iron treatments stimulated the enzymatic defense system with increased (POD, SOD and CAT) or reduced (PPO) activity in treated plants. It was noted that the interaction between SA and chelated iron was most beneficial to the treated plants relative to their separate treatment. This study suggests that an interaction between SA and iron could be a practical strategy to protect the strawberry crop under saline conditions.