Multifaceted Impact of Exogenous Salicylic Acid on Vicia Faba L. Under Salt Stress: Plant Growth, Water Status, and Photosynthetic Performance (OJIP Fluorescence)

Abstract

Abstract Purpose This study investigated the effect of salt stress on growth, water status, and photosynthetic activity in faba bean plants and the role of salicylic acid (SA) in mitigating the harmful effects of salt stress. Methods Faba bean plants were subjected to different levels of salt stress (0, 90, 120, and 150 mM NaCl) and salicylic acid (0, 0.5, and 1 mM SA). Salt and SA treatments were applied starting from the seedling stage and continued for two months. Results Results show that salt stress significantly affects the different studied parameters. Salinity strongly decreases the plant weight (fresh and dry) and the plant water status (Leaf Water Potential (LWP), Stomatal conductance (gs), Relative water content (RWC). The analysis of the Photosystem II (PSII) function disruption indicates that salt stress induced an electron transport inhibition at the donor side of the PSII due to the Oxygen-Evolving Complex (OEC) inactivation (positive-K-band) and reduced the PSII unit’s energetic connectivity (positive-L-band). The evaluation of the rate reduction of the end electron acceptor at the Photosystem I (PSI) side revealed that salt stress resulted in gradual decreases in the reduction rates. Nevertheless, the exogenous application of salicylic acid (SA) allowed plants to maintain a high weight/length value with a significant improvement in plant water status. Chlorophyll -a fluorescence analysis shows that SA application improved at the donor side of electron transport (lower intensity of the K and L-band), with a larger pool size under the combination of 0.5 mM SA and high salt stress levels applications. Conclusion These results suggest that the salt stress significantly affects the PSII by the inactivation of the OEC and decreasing the PSII unit’s connectivity. However, SA had a beneficial effect on the PSII and PSI salt stress tolerance in Vicia faba L.