Cao Xinde, Ma Lena Q, Tu Cong
Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA.
Environ Pollut. 2004;128(3):317-25. doi: 10.1016/j.envpol.2003.09.018.
This study measured antioxidative responses of Chinese brake fern (Pteris vittata L.) upon exposure to arsenic (As) of different concentrations. Chinese brake fern was grown in an artificially-contaminated soil containing 0 to 200 mg As kg(-1) (Na2HAsO4) for 12 weeks in a greenhouse. Soil As concentrations at < or =20 mg kg(-1) enhanced plant growth, with 12-71% biomass increase compared to the control. Such beneficial effects were not observed at >20 mg As kg(-1). Plant As concentrations increased with soil As concentrations, with more As being accumulated in the fronds (aboveground biomass) than in the roots and with maximum frond As concentration being 4675 mg kg(-1). Arsenic uptake by Chinese brake enhanced uptake of nutrient elements K, P, Fe, Mn, and Zn except Ca and Mg, whose concentrations mostly decreased. The contents of non-enzymatic antioxidants (glutathione, acid-soluble thiol) followed similar trends as plant As concentrations, increasing with soil As concentrations, with greater contents in the fronds than in the roots especially when exposed to high As concentrations (>50 mg kg(-1)). The activities of enzymatic antioxidants (superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase) in Chinese brake followed the same trends as plant biomass, increasing with soil As up to 20 mg kg(-1) and then decreased. The results indicated though both enzymatic and non-enzymatic antioxidants played significant roles in As detoxification and hyperaccumulation in Chinese brake, the former is more important at low As exposure (< or =20 mg kg(-1)), whereas the latter is more critical at high As exposure (50-200 mg kg(-1)).
本研究测定了蜈蚣草（Pteris vittata L.）在暴露于不同浓度砷（As）时的抗氧化反应。将蜈蚣草种植在人工污染的土壤中，土壤含砷量为0至200毫克/千克（Na2HAsO4），在温室中培养12周。土壤砷浓度≤20毫克/千克时促进植物生长，与对照相比生物量增加12 - 71%。在砷浓度>20毫克/千克时未观察到这种有益效果。植物体内的砷浓度随土壤砷浓度增加而增加，地上部分（叶）积累的砷比根部更多，叶中砷的最大浓度为4675毫克/千克。蜈蚣草对砷的吸收增加了除钙和镁之外的营养元素钾、磷、铁、锰和锌的吸收，钙和镁的浓度大多降低。非酶抗氧化剂（谷胱甘肽、酸溶性硫醇）的含量与植物砷浓度呈现相似趋势，随土壤砷浓度增加而增加，尤其是在暴露于高砷浓度（>50毫克/千克）时，叶中的含量高于根部。蜈蚣草中酶促抗氧化剂（超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、愈创木酚过氧化物酶）的活性与植物生物量呈现相同趋势，随土壤砷浓度增加至20毫克/千克时升高，之后降低。结果表明，虽然酶促和非酶促抗氧化剂在蜈蚣草对砷的解毒和超积累过程中都发挥了重要作用，但前者在低砷暴露（≤20毫克/千克）时更重要，而后者在高砷暴露（50 - 200毫克/千克）时更关键。
