Effect of silicon nutrition on lipid peroxidation and antioxidant response of cucumber plants exposed to salinity stress

The effect of silicon (Si) on salinity-induced oxidative damages of cucumber was investigated in a greenhouse experiment. Two cucumber cultivars (Cucumis sativus L. cvs. Negin and Super Dominus) were exposed to two salinity levels (0 and 50mM NaCl) and two Si levels (0 and 1 mu M). Silicon stimulated shoot growth of cucumber particularly under saline conditions. Leaf malondialdehyde (MDA) content was increased in Super Dominus' while it remained unchanged in Negin' by salt stress. MDA content in cucumber leaves was reduced by Si. The effect of salinity on activity of catalase (CAT) and ascorbate peroxidase (APX) was dependent on enzyme type and cultivar. Silicon increased activity of CAT, APX, and guaiacol peroxidase (GPX) in the leaves. Silicon nutrition could alleviate salt-oxidative stress on cucumber plants by increasing activity of antioxidant enzymes. Higher activity of CAT, APX, and GPX in Negin' might be associated with its greater tolerance to salinity.