微塑料和镉协同作用对蒲公英光合特征及抗氧化作用的影响

Effects of Microplastics and Cadmium on the Photosynthetic Characteristics and Antioxidant Responses of Taraxacum mongolicum

摘要: 土壤中普遍存在重金属和微塑料(MPs)复合污染的环境问题，其中，镉(Cd)具有较高的生态风险，聚对苯二甲酸乙二醇酯(PET)是常见的微塑料污染物。以蒲公英(Taraxacum mongolicum)为研究对象，开展重金属Cd (5 mg/kg)和不同浓度MPs (0、0.2%、0.5%、1%、2% PET)复合胁迫试验，探究Cd与PET协同作用对蒲公英幼苗叶绿素含量及抗氧化酶活性的影响。结果表明：1) 0.2% PET和5 mg/kg Cd协同处理下，蒲公英的叶绿素a/b比值与对照组相比增幅约为0.49%，0.5% PET时，叶绿素a/b比值降低了0.55%；2) 0.2% PET和5 mg/kg Cd协同处理下，蒲公英幼苗中过氧化物酶(POD)活性达最高，为338.86 U/g，较Cd胁迫对照组提升0.450%，Cd胁迫对超氧化物歧化酶(SOD)活性影响也显著减弱；3) 0.5% PET和5 mg/kg Cd协同处理下，蒲公英的SOD活性开始呈下降趋势，直至2% PET较Cd组降低0.970%。综上，PET与Cd的协同作用对蒲公英叶绿素含量及抗氧化酶活性影响显著，0.2% PET对叶绿素a/b比值影响较小，可缓解Cd诱导的氧化应激损伤，0.2% PET减弱了Cd的毒性效应。

Abstract: To address the widespread co‑contamination of soils by heavy metals and microplastics (MPs), a pot experiment was conducted using cadmium (Cd), a metal with high ecological risk, and polyethylene terephthalate (PET), a common microplastic. Dandelion seedlings (Taraxacum mongolicum) were exposed to a fixed Cd concentration (5 mg/kg) together with five PET levels (0, 0.2%, 0.5%, 1%, and 2%). The effects on leaf chlorophyll content and antioxidant enzyme activities were examined. The results showed that: 1) Under the combined stress of 0.2% PET and 5 mg/kg Cd, the chlorophyll a/b ratio of Taraxacum mongolicum increased by approximately 0.49% compared with the control group, while it decreased by 0.55% at the 0.5% PET concentration; 2) The peroxidase (POD) activity in dandelion seedlings reached a maximum of 338.86 U/g under the synergistic treatment of 0.2% PET and 5 mg/kg Cd, which was 0.450% higher than that in the Cd-only stressed control group. Additionally, the adverse effect of Cd stress on superoxide dismutase (SOD) activity was significantly attenuated; 3) When exposed to the combined treatment of 0.5% PET and 5 mg/kg Cd, the SOD activity of dandelion began to exhibit a downward trend, ultimately decreasing by 0.970% at the 2% PET concentration compared with the Cd-only group. In conclusion, the synergistic interaction between PET and Cd significantly affects the chlorophyll content and antioxidant enzyme activities of Taraxacum mongolicum. Specifically, 0.2% PET has a minimal impact on the chlorophyll a/b ratio, can alleviate Cd-induced oxidative stress damage, and thereby mitigates the toxic effect of Cd.