Zhang Yu-xiu, Huang Zhi-bo, Zhang Hong-mei, Li Lin-feng, Chai Tuan-yao
Department of Bioengineering, School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
Huan Jing Ke Xue. 2009 Dec;30(12):3676-83.
Plant species capable of accumulating heavy metals are of considerable interest for phytoremediation and phytomining. The mechanism of Mn tolerance/hyperaccumulate in Phytolacca americana L. is less known. To elucidate the role of antioxidative enzyme in response to Mn, the 6-week-old seedling of Mn hyperaccumulator P. americana and non-accumulator-tobacco (Nicotiana tabacum) were exposed to half strength Hoagland solution with 1 mmol x L(-1) or 3 mmol x L(-1) MnCl2 for 4 days. The photosynthetic rate in P. americana decreased more slowly than that in tobacco, while the MDA content and electrolyte leakage in tobacco increased more rapidly than that in P. americana. For example, after exposure to 1 mmol x L(-1) Mn for 4 days, the photosynthetic rates of P. americana and tobacco in comparison to the control reduced by 13.3% and 75.5%, respectively. The MDA content and electrolyte leakage in tobacco increased by 347.3% and 120.1%, respectively, whereas Mn had no marked effect on both of it in P. americana, indicated that the oxidative damage in tobacco was more serious than that in P. americana. The activities of SOD and POD of both species increased rapidly with elevated Mn concentration and exposure time in both species, the increase of SOD activity in P. americana was higher than that in tobacco. CAT activity in tobacco declined rapidly, while the activity of CAT in P. americana was increased. The activities of SOD, POD and CAT in P. americana upon 1 mmol x L(-1) Mn exposure increased by 161.1%, 111.3% and 17.5%, respectively. The activities of SOD and POD in tobacco increased by 55.5% and 206.0%, respectively, while CAT activity decreased by 15.6%, indicating that the antioxidative enzymes in P. americana, particularly in CAT,could fully scavenge the reactive oxygen species generated by Mn toxicity. These results collectively indicate that the enzymatic antioxidation capacity is one of the important mechanisms responsible for Mn tolerance in hyperaccumulator plant species.
能够积累重金属的植物物种对于植物修复和植物采矿具有重要意义。美洲商陆对锰的耐受/超积累机制尚不清楚。为了阐明抗氧化酶在响应锰时的作用，将6周龄的锰超积累植物美洲商陆和非积累植物烟草暴露于含有1 mmol/L或3 mmol/L MnCl₂的半强度霍格兰溶液中4天。美洲商陆的光合速率下降比烟草慢，而烟草中的丙二醛含量和电解质渗漏比美洲商陆增加得更快。例如，暴露于1 mmol/L锰4天后，与对照相比，美洲商陆和烟草的光合速率分别降低了13.3%和75.5%。烟草中的丙二醛含量和电解质渗漏分别增加了347.3%和120.1%，而锰对美洲商陆的这两者均无显著影响，表明烟草中的氧化损伤比美洲商陆更严重。两种植物的超氧化物歧化酶（SOD）和过氧化物酶（POD）活性均随锰浓度升高和暴露时间延长而迅速增加，美洲商陆中SOD活性的增加高于烟草。烟草中的过氧化氢酶（CAT）活性迅速下降，而美洲商陆中的CAT活性增加。暴露于1 mmol/L锰后，美洲商陆中SOD、POD和CAT的活性分别增加了161.1%、111.3%和17.5%。烟草中SOD和POD的活性分别增加了55.5%和206.0%，而CAT活性下降了15.6%，表明美洲商陆中的抗氧化酶，特别是CAT，能够充分清除由锰毒性产生的活性氧。这些结果共同表明，酶促抗氧化能力是超积累植物物种耐受锰的重要机制之一。
