Salicylic acid and nitric oxide increase photosynthesis and antioxidant defense in wheat under UV-B stress

The effects of exogenous salicylic acid (SA), sodium nitropusside (SNP, a nitric oxide donor), or their combination on dwarf polish wheat (Triticum polonicum L.) seedlings under UV-B stress were studied. The UV-B stress significantly decreased plant height, shoot dry mass, pigment content, net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, transpiration rate, and variable to maximum chlorophyll fluorescence ratio (Fv/Fm) in all plants, but less in the presence of SA, SNP, and their combination. On the other hand, there were considerable increases in malondialdehyde (MDA), proline, O2 •-, and H2O2 content under the UV-B stress. When SA, SNP, and their combination were applied, content of MDA, proline, H2O2, and O2 •- were less increased. Moreover, there were considerable increases in activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione reductase under the UV-B stress and more in the presence of SA, SNP, and their combination. Therefore, it is considered that SA, SNP, and especially their combination could alleviate UV-B stress in dwarf polish wheat.