Beneficial role of exogenous silicon on yield, antioxidant systems, osmoregulation and oxidative stress in fenugreek (Trigonella foenum-graecum L.) under salinity stress

Purpose In the Earth's crust, silicon (Si) is the most abundant element after oxygen, while, under salt stress, its role in the tolerance of aromatic and medicinal plants (AMPs) is not yet detailed. For this reason, in this study we evaluated the effect of exogenous Si on some tolerance-related parameters in salt-stressed fenugreek, as an important AMP. Methods 3 mM of exogenous Si was applied to assess its impact on plant biomass and on some tolerance-related parameters in fenugreek (Trigonella foenum-graecum L.) grown under 150 mM NaCl stress. Results Results showed that salinity reduced growth parameters, relative water content, photosystem II efficiency, stomatal conductance and K+ and Ca2+ contents, while it increased the Na+ content, which could explain the obtained reduction in fenugreek growth and yield. However, Si supply reversed the depressive effects of salinity and improved fenugreek growth and yield. Adding exogenous Si also caused a significant reduction in Na+ content and increased K+ and Ca2+ concentrations. The content of malonyldialdehyd and hydrogen peroxide and the level of electrolyte leakage were significantly increased in salt-stressed fenugreek, while were significantly decreased after Si supplementation. The reduction in oxidative stress markers in Si-treated plants was correlated with a significant increase in both enzymatic and non-enzymatic antioxidant systems and an important accumulation of compatible solutes. Conclusion Therefore, exogenous Si was directly involved in the central defensive mechanisms to enhance salt tolerance of fenugreek, thus its application could be a promoting strategy to alleviate the damages of salinity on fenugreek growth and yield.