modifying elements

Salinity is one of the most important environmental stresses that affect the production of horticultural crops. So, some beneficial minerals may neutralize the effects of salinity. In order to investigate the effect of application of selenium and silicon nutrients under salinity and alkalinity stress on growth and some morphological, biochemical and mineral attributes of greenhouse cucumber "Nagin" under hydroponic condition, a factorial experiment based on a completely randomized design was conducted with four replications.  The treatments consisted of three levels of stress (non-stress, salinity stress of 75 mM sodium chloride (NaCl), alkalinity stress of 75 mM sodium bicarbonate (NaHCO3) and beneficial elements in five levels (0, 4 and 6 mg L-1 of selenium and 75 and 100 mg L-1 of silicon). According to the results of this study, the lowest leaf area (215.04 cm2) was observed in alkalinity treatments with no addition of selenium and silicon, whilst, it increased by application of beneficial elements (342.45 cm2) compared to control. The highest yield was obtained in 4 and 6 mg L-1 of selenium. Application of 100 mg L-1 silicon increased polyphenol oxidase activity by 13.91% and glutathione peroxidase activity by 38.14% compared to only sodium carbonate treatment under alkaline stress conditions.