Effect of silicon supplementation on wheat plants under salt stress

Silicon (Si) is the second most abundant element in the earth’s crust and is regarded as a beneficial element for higher plants. In this study, the effect of Si supplementation (1 and 4 mM) was studied on wheat (Triticum aestivum cv. Homa) plants grown hydroponically under salinity stress (50 and 150 mM NaCl) for two weeks under controlled environmental conditions. Plant biomass was found to decrease at both salinity levels. Contrary to our expectation, Si supplementation failed to mitigate the salt stress effects on dry matter production. However, the majority of biochemical parameters related to salt tolerance showed improvements as a result of Si application, particularly at 1 mM. Under both control and salinity conditions, Si treatment resulted in higher leaf contents of chlorophyll and carotenoids, soluble sugars, proteins, and free amino acids, particularly proline. Osmotic potential, however, declined in the roots, suggesting that Si supplementation might contribute to plant’s higher water uptake capacity. Si treatment diminished leaf concentration of Na+ in the cell sap but increased it in the cell wall-bound fraction, indicating a Na+ detoxification mechanism mediated by Si. Our results suggest that a short-term Si treatment affects biochemical indicators of salt tolerance but that long-term exposure to Si is needed for a significantly alleviating effect on plant biomass