Cucumber is one of the most important vegetables around the world which plays an important role in human nutrition. Salinity and alkalinity are two common abiotic stresses in arid and semi-arid agricultural regions that limit agricultural crop production. In order to investigate the effects of beneficial elements of selenium and silicon on physiological characteristics of cucumber under salinity and alkalinity stress conditions, a factorial experiment with a completely randomized basic design and four replications was carried out in greenhouse of Zarghan city, Shiraz. The treatments consisted of three levels of stress (non-stress, salinity stress of 75mM sodium chloride (NaCl), alkalinity stress of 75mM sodium bicarbonate (NaHCO3) and beneficial elements in five levels (0, 4 and 6mg/l of sodium selenite and 75 and 100 mg/l of sodium silicate). In alkalinity-stress conditions, different concentrations of selenium and silicon caused a significant increase in leaf relative water content and total chlorophyll concentration compared with control treatment. In salinity stress condition, leaf relative water content and total chlorophyll decreased, significantly. In both stress conditions, selenium and silicon increased the carotenoids, proline, total soluble sugars, malondialdehyde and protein concentrations, and superoxide dismutase, peroxidase and catalase enzyme activities. Based on the results, selenium and silicon foliar applications led to alleviation adverse effects of salinity and alkalinity stresses on physiological traits and reducing the adverse effects of these stresses on cucumber growth.
