Bo CHENG,Hai-feng LIAN,Ying-ying LIU,Xin-hui YU,Ya-li SUN,Xiu-dong SUN,Qing-hua SHI,Shi-qi LIU
A hydroponic study was conducted to determine the effects of selenium (Se: 0, 3, 6 μmol L –1 ) on senescence-related oxidative stress in garlic plants grown under two sulfur (S) levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose (0.3 μmol L –1 ) at low S level showed higher yields (12.0% increase in fresh weight yield, 13.7% increase in dry weight yield) than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glutathione peroxidase and catalase, but lower superoxide dismutase activities. Changes in F v / F m values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.
Flame retardants , such as Tetrabromobisphenol A (TBBPA), Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and tributyl phosphate (TBP), are frequently detected in surface water. However, the effects of FRs exposure on aquatic organisms especially freshwater microalgae are still unclear. In this study, the toxicities of TBBPA, TDCPP and TBP to microalgae Chlorella sorokiniana , in terms of growth inhibition, photosynthetic activity inhibition and oxidative damage, were investigated, and according ecological risks were assessed. The results showed that TBBPA, TDCPP and TBP had inhibitory effects on C. sorokiniana , with 96 h EC 50 (concentration for 50% of maximal effect) values of 7.606, 41.794 and 49.996 mg/L, respectively. Fv / Fm decreased as the increase of exposure time under 15 mg/L TBBPA. Under 50 mg/L TDCPP and 80 mg/L TBP exposure, Fv / Fm decreased significantly after 24 h. However, Fv / Fm rose after 96 h, indicating that the damaged photosynthetic activity was reversible. The content of chlorophyll a decreased, as the increase of TBBPA concentration from 3 to 15 mg/L. However, chlorophyll a increased first and then decreased, as the increase of TDCPP and TBP concentrations from 0 to 50 mg/L and 0–80 mg/L, respectively. Results indicated that C. sorokiniana could use the phosphorus of TDCPP and TBP to ensure the production of chlorophyll a . The risen content of reactive oxygen species , malondialdehyde as well as superoxide dismutase activity indicated that exposure to FRs induced oxidative stress . Additionally, the risk quotients showed that tested FRs had ecological risks in natural waters or wastewaters. This study provides insights into the toxicological mechanisms of different FRs toward freshwater microalgae for better understanding of according environmental risks.
危险品化学品经营许可证（带存储）