High Sulfur (S) Supplementation Imparts Waterlogging Tolerance to Oilseed rape (Brassica napus L.) Through Upregulating S Metabolism and Antioxidant Pathways

Waterlogging significantly impacts plant growth and development by altering nutrient uptake and antioxidant enzyme functions, resulting in reduced yield. Plants need sulfur (S) to produce reduced glutathione (GSH), a thiol compound that combats abiotic stresses. It is hypothesized that supplying S to high S-demanding oilseed rape plants beyond its growth requirements can reduce the adverse effect of waterlogging stress. Therefore, this study evaluated the comparative effect of different S doses (mg kg − 1 soil), i.e., no-S (S 0 ), low-S (S 1 , 35), medium-S (S 2 , 70), and high-S (S 3 , 140) on growth, yield and antioxidant defense systems of normal growing and waterlogged oilseed rape plants. Waterlogging was imposed at the inflorescence emergence stage for 7 days by retaining a 3-cm layer of water above the soil surface. Waterlogged plants supplemented with high-S showed improved growth and higher yield than those supplemented with lower S levels, and this response was associated with improved activity/contents of antioxidants, including ascorbate (AsA), GSH, ascorbate peroxidase, catalase, glutathione reductase, glutathione peroxidase, glutathione S-transferase, monodehydroascorbate reductase, and dehydroascorbate reductase, with concomitant lowering of hydrogen peroxide, dehydroascorbate and malondialdehyde content. Furthermore, leaf S concentration was enhanced in waterlogged plants treated with high-S, while anions were regulated whereby Cl − uptake was decreased. However, under control conditions, high-S did not provide additional benefits of improved plant growth, yield, and antioxidant activities compared to the medium-S application. Thus, it is concluded that additional S supplementation mitigates the adverse effects of waterlogging stress on oilseed rape, and needs to be employed as a potential strategy to alleviate the negative effects of this abiotic stress.