Sulfur alleviates cadmium toxicity in rice ( Oryza sativa L.) seedlings by altering antioxidant levels

We investigated changes in reactive oxygen species (ROS) and antioxidant levels in rice ( Oryza sativa L. cv ‘Dongjin’) seedlings treated with toxic cadmium (Cd) and/or sulfur (S). Exposure of rice seedlings to 30 μM Cd inhibited plant growth and resulted in increased levels of superoxide, hydrogen peroxide, and malondialdehyde (MDA), and induced Cd uptake by the roots, stems, and leaves. Application of S to Cd-stressed seedlings ameliorated Cd-induced oxidative stress by increasing the capacity of the glutathione (GSH)-ascorbate (AsA) cycle, promoting S assimilation by increasing cysteine, GSH, and AsA content in treated plants, and decreasing Cd transfer from the roots to the stems and leaves. Therefore, these results indicate that S application represents a viable strategy of alleviating Cd-induced growth inhibition and oxidative damage by restricting Cd translocation from the roots to the stems and leaves, thereby maintaining sufficient levels of GSH and AsA by sustaining homeostasis of the GSH-AsA cycle.