In order to evaluate the differential absorption and toxicity of arsenate (AsV) and arsenite (AsIII), Lemna valdiviana plants were grown in a nutrient solution and subjected to 0.0 (control); 0.5; 1.0; 1.5; 2.0; 3.0; 4.0; 5.0 and 7.5 mg L-1 of AsIII or AsV for three days. Exposure to both chemical forms resulted in As bioaccumulation, although AsIII-grown plants showed higher As content in tissues. In AsV-grown plants, the relative growth rate (RGR) decreased to 50%, at a concentration of 4.0 mg L-1, while for treatments with AsIII, the same decrease was observed at 1.0 mg L-1. The tolerance index decreased with increasing concentrations, with lower values for AsIII. Plants treated with AsIII showed increased superoxide anion levels, whilst higher levels of hydrogen peroxide were present in AsV-treated plants. Moreover, malondialdehyde (MDA) levels were higher for plants subjected to AsIII when compared to AsV at lower concentrations. Concentrations of 1 mg L-1 of AsIII and 4 mg L-1 of AsV showed equivalent MDA levels. Superoxide dismutase and catalase activities were increased at low concentrations and were inhibited at higher concentrations of AsIII and AsV, whereas peroxidase activity was positively modulated by increased AsIII or AsV concentrations. In conclusion, L. valdiviana plants took up and accumulated arsenic as AsIII or AsV, demonstrating the potential for phytoremediation of this metalloid. Furthermore, AsIII-exposed plants showed enhanced toxicity when compared to AsV, at the same applied concentration, although toxicity was more related to internal As concentrations, regardless of the chemical form applied.

中文翻译：

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砷在植物中的毒性比砷高吗？

为了评估砷酸盐（AsV）和亚砷酸盐（AsIII）的差异吸收和毒性，将Lemna valdiviana植物在营养液中生长并进行0.0（对照）处理。0.5; 1.0; 1.5; 2.0; 3.0; 4.0; 5.0和7.5 mg L-1的AsIII或AsV持续三天。暴露于两种化学形式均会导致砷的生物积累，尽管生长于AsIII的植物在组织中的砷含量较高。在AsV生长的植物中，相对生长速率（RGR）在4.0 mg L-1的浓度下降低至50％，而对于AsIII处理，在1.0 mg L-1处观察到相同的降低。耐受指数随浓度增加而降低，AsIII值较低。用AsIII处理的植物显示出增加的超氧阴离子水平，而在AsV处理的植物中存在较高水平的过氧化氢。此外，与较低浓度的AsV相比，接受AsIII的植物的丙二醛（MDA）水平较高。1 mg L-1的AsIII和4 mg L-1的AsV的浓度显示等效的MDA水平。超氧化物歧化酶和过氧化氢酶的活性在低浓度下会增加，而在较高浓度的AsIII和AsV下会受到抑制，而过氧化物酶的活性则由较高的AsIII或AsV浓度正向调节。总之，瓦尔迪维亚纳植物吸收并积累了砷作为AsIII或AsV，这表明该类金属具有植物修复的潜力。此外，在相同的施用浓度下，与AsV相比，暴露于AsIII的植物显示出增强的毒性，尽管无论采用何种化学形式，毒性都与内部As浓度相关。