Effect of silicon and nano silicon application on wheat (C3) and sorghum (C4) under salinity stress

Salinity stress is one of the factors that reduced the growth and yield of crops. The response of C3 and C4 plants to salinity stress and possible mitigation of the effects of this stress with the application of silicon and nanosilicon may be different according to the photosynthetic pathway of these plants. Therefore, this study was conducted to compare the response of wheat as a C3 plant and sorghum as a C4 plant to the effect of silicon and nanosilicon application on salinity stress mitigation.

Two experiments were conducted in a completely randomized design with factorial arrangement in pots filled with soil at Sari University of Agriculture and Natural Resources in 1398. The salinity factor was at two levels included 0 and 100 mM NaCl and the silicon factor was at three levels included 0 and 2 mM potassium silicate and 2 mM nanosilicon (SiO2)). Both forms of silicon were applied as foliar application. Plant photosynthesis-related traits were measured after 13 days of treatments the next day the plants were harvested for growth measurement and other biochemical assays.

The results of this study showed that salinity caused a significant reduction in fresh and dry weight of plants in both wheat and sorghum plants. Application of silicon in wheat and application of nanosilicon in sorghum caused a significant increase in fresh and dry weight of plants under salinity. Application of silicon and nanosilicon had no significant effect on stomatal conductance and transpiration of wheat and sorghum plants under salinity. In wheat plants, silicon foliar application significantly increased photosynthesis rate under salinity, but nanosilicon had no significant effect. On the contrary in sorghum, the use of silicon had no significant effect on the photosynthesis rate under salinity, but nanosilicon increased the photosynthesis rate of sorghum plants. In sorghum plant, under salinity conditions, the use of silicon and nanosilicon reduced the amount of hydrogen peroxide contents by 21 and 30%, respectively, and the amount of lipid peroxidation by about 13 and 23%, respectively. However, the use of silicon and nanosilicon did not indicated a significant effect on the content of hydrogen peroxide the amount of lipid peroxidation wheat plants grown under saline condition. The application of silicon in wheat plants increased 58% of the total fresh weight and 68% of the total dry weight of plants under salinity, although the application of nanosilicon had no significant effect. The use of silicon and nanosilicon increased the fresh and dry weight of sorghum plants under salinity, but the additive effect was greater by application nanosilicon, so that the total dry weight of sorghum plants under salinity in nanosilicon treatment were 75% higher than plants without this treatment.

This study showed that the use of silicon in wheat plants under salinity improved photosynthesis and thus reduced the effects of salinity on growth to some extent, but nanosilicon in this plant did not have such an effect. Conversely, in sorghum plants under salinity, the use of nanosilicon by reducing the amount of hydrogen peroxide and lipid peroxidation, reduced the oxidative stress caused by salinity and increased the photosynthesis rate of the plant, which led to more growth of plants under salinity stress. Such cases were not observed with the use of silicon.