Effects of silicon on photosynthesis and concentration of nutrients of Brassica napus L. in saline-stressed conditions

Saline stress recognized as the most important abiotic stress for plants. Recent studies show that Si has a striking role in plant resistance to environmental stresses, such as saline stress. In order to study the effects of Si and saline conditions on photosynthesis and concentration of nutrients of SLM046 variety of Brassica nap us L., three levels of Si (0, 2 and 4 mM) and three levels of NaCl (100, 200 and 300 mM) were used by factorial and completely randomised design with four repetition in hydroponic greenhouse controlled conditions. After the treatment was applied, in flowering phase, the photosynthesis was measured. Finally, all plants were removed from the bed and the biochemical characteristics of plants (including the concentration of nutrients, proline and electrolyte leakage) were measured. Concentration of Si in leaves was also measured. The results showed that salinity has significant effect on photosynthesis, electrolyte leakage and proline concentration. An increase in salinity caused increase in electrolyte leakage and proline concentration and decrease in photosynthesis, but adding Si in saline conditions increased photosynthesis. Electrolyte leakage and proline concentration were decreased by adding Si. Saline stress decreased nitrate, K and N concentrations and K/Na ratio and increased Na and Cl concentrations. Adding Si to plant nutrient solution caused decrease in concentrations of Na and Cl but increased nitrate, K, N and K/Na ratio. The concentration of P was not affected by this treatment. The results showed that adding Si in plant nutrition solution caused an increase in Si concentration in plant leaves but increasing the levels of NaCl caused decrease in absorption of Si by the plant and decrease in concentration of Si in the plant.