Improvement of Salinity Tolerance in Rice Seedlings by Exogenous Magnesium Sulfate Application

Abstract

This study was conducted to develop the salt tolerance of rice by exogenous application of magnesium sulfate supplement (MgSO4). The salinization was carried out on 7-day-old rice seedlings including BC15 (salinity tolerant) and DT84DB (salinity susceptible) varieties with 0.5 mM MgSO4. The exogenous application of MgSO4 significantly improves the growth of seedlings of both varieties. In addition, antioxidant activities increase in line with the raise of total phenolic and total flavonoid contents. Remarkably, the contents of momilactone B (MB) and phenolic compounds including tricin, ρ-coumaric, salicylic, cinnamic, benzoic, and ferulic acids simultaneously rise in both varieties treated by salinity and 0.5 mM MgSO4. Interestingly, MB was not found in the salt-treated samples but presents with considerable contents in the salt and MgSO4-treated cultivars. The findings imply that MgSO4 may significantly improve the salt tolerance of rice seedlings through the enhancement of secondary metabolic synthesis pathways, of which phenolic acids and momilactone B may play a crucial role in the response of rice to salt stress. In contrast, momilactone A (MA) did not show any contribution in salinity tolerance of examined rice cultivars at the early seedling stage. Further investigations on the effect of MgSO4 exogenous application in improving salinity tolerance of various rice varieties at other growing stages should be carried out.