Combined effect of salicylic acid and calcium application on salt-stressed strawberry plants

The salinity of water and agricultural lands is a major environmental factor adversely affecting crop productivity. Strawberry plants have been found to be sensitive to salt stress conditions. Salicylic acid (SA) and Ca2+ are endogenous signal molecules involved in many metabolic processes, which can stimulate the plants defence mechanisms to biotic and abiotic constraints. The main objective of this work was to investigate the impacts of SA (0.25 mM) and calcium nitrate (5 mM) application, singly or in combination, on growth parameters as well as physiological and biochemical markers of strawberry plants (Fragaria ananassa Duch, var. Fortuna) exposed to saline conditions (80 mM NaCl). The results showed that high salinity reduces plant growth and photosynthetic pigment content. Salt stress also induced an accumulation of Na, a decrease in K and Ca concentrations, a reduction in the levels of sugars, total phenol, relative water content, photochemical efficiency (F-v/F-m), and stomatal conductance as well as a decrease in proline, proteins, enzyme activities (catalase, superoxide dismutase and peroxidase) and an accumulation of hydrogen peroxide and malondialdehyde. However, SA and calcium treatments enhanced the plants' tolerance to salt stress by improving the above-mentioned parameters. Additionally, the best results were obtained with combined treatment (Ca + SA) under both salinity conditions. These findings indicated that the combination of calcium supplementation with exogenous application of SA may provide an effective solution to improving the strawberry plant's tolerance to saline conditions.