Selenium Alleviates Coleus from Oxidative Damage under Pb Stress by Resource Allocation and Antioxidant Defense System

摘要

The role of selenium (Se) against lead (Pb) stress in Coleus (Coleus blumei benth.) was investigated by evaluating the allocation plasticity and antioxidant properties of plants cultured hydroponically with lead (1.0 mM Pb) and selenite (0～5.0 mM Se) in this study. It was showed that Pb reduced the root growth and caused serious damage in the roots, which was accompanied by biomass changes and Pb accumulation in the organ. When Se application up to 1.0 mM improved the biomass allocation and Pb accumulation of Coleus organs and significantly decreased Thiobarbituric Acid Reactive Substances (TBARS) accumulation in Coleus treated with 1.0 mM Pb. However, above 1.0 mM, Se induced stress in Coleus grown with Pb. These results indicated that at this concentration, Se can protect Coleus from Pb stress by expressing primarily biomass allocation and metal partitioning. Significant changes of antioxidant defense system in Coleus exposed to Pb stress were also found as a result of the added Se. Se supplied up to 1.0 mM greatly decreased root Superoxide Dismutase (SOD) and Peroxidase (POD) activity in Pb-stressed Coleus (p<0.05). In addition, Catalase (CAT) and glutathione peroxidase (GSH-Px) activity was increased with increasing Se concentration (p<0.05). The effect of Se on glutathione (GSH) in Coleus Pb-treated was dose-dependent. The GSH content increased up to a concentration of 2.5 mM Se and then decreased. These changes in enzymatic and non-enzymatic antioxidants showed that Se supplied had a significant disturbance on Coleus under Pb stress and affected the biochemical and physiological processes. Furthermore, the obtained results also showed that appropriate Se supplementation may ameliorate Pb-induced oxidative stress by decreasing lipid peroxidation and altering antioxidant defense system and that Se detoxification and accumulation in Coleus might be associated closely with the efficiency of these mechanisms.