Mishra Seema, Srivastava S, Tripathi R D, Kumar R, Seth C S, Gupta D K
Ecotoxicology and Bioremediation Group, National Botanical Research Institute, Rana Pratap Marg, Lucknow 226001, India.
Chemosphere. 2006 Nov;65(6):1027-39. doi: 10.1016/j.chemosphere.2006.03.033. Epub 2006 May 8.
Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.
金鱼藻（Ceratophyllum demersum L.）植株在暴露于不同浓度的铅（1 - 100微摩尔）1 - 7天后，表现出了植物毒性和耐受性反应。具体反应是浓度和持续时间的函数。7天后植株积累了1748微克铅/克干重，这反映了其金属积累能力，然而大部分金属（1222微克/克干重，70%）仅在暴露1天后就积累了。随着金属浓度和暴露持续时间的增加，铅导致的毒性效应和氧化应激通过生物量和光合色素的减少以及丙二醛（MDA）含量和电导率的增加而明显体现。7天后观察到了衰老现象的形态症状，如叶片黄化和破碎。参照抗氧化系统和植物螯合肽的合成对植物采用的金属耐受性和解毒策略进行了研究。蛋白质和抗氧化酶，即超氧化物歧化酶（SOD，EC 1.15.1.1）、愈创木酚过氧化物酶（GPX，EC 1.11.1.7）、抗坏血酸过氧化物酶（APX，EC 1.11.1.11）、过氧化氢酶（CAT，EC 1.11.1.6）和谷胱甘肽还原酶（GR，EC 1.6.4.2）在较低浓度和持续时间时表现出诱导，随后下降。除GPX外，所有酶在1天后均表现出最大活性。在适度暴露条件下观察到半胱氨酸、非蛋白硫醇（NP - SH）和谷胱甘肽（GSH）含量增加，随后下降。在铅浓度为10和50微摩尔时，植物螯合肽（PC(2)和PC(3)）合成至显著水平，同时GSH水平下降。因此，PC的产生似乎对金属解毒很重要，然而它可能导致GSH的消耗，进而导致氧化应激。结果表明，植物对中等浓度的铅有积极反应并积累了大量金属。由于金属积累以及解毒潜力，该植物似乎有潜力作为铅污染中等的水生环境中的植物修复物种。
