Mishra Seema, Srivastava Sudhakar, Tripathi R D, Dwivedi Sanjay, Shukla M K
Ecotoxicology and Bioremediation Group, National Botanical Research Institute, Rana Pratap Marg, Lucknow-226001, India.
Environ Toxicol. 2008 Jun;23(3):294-301. doi: 10.1002/tox.20340.
Cadmium (Cd) contamination of aquatic systems is of major concern since it is a nonessential element and hampers plant growth upon accumulation. The aim of this study was to investigate the Cd accumulation behavior of coontail plant, Ceratophyllum demersum L., toxicity induced and response of the antioxidant system. Plants were exposed to various concentrations of Cd (0-10 microM) for a period of 1-7 days. Accumulation of Cd was found to be a concentration duration dependent phenomenon. The maximum accumulation of Cd, 1293 microg g(-1) dw, was observed after 7 days at 10 microM. Plants showed significant stimulation of the activities of various antioxidant enzymes viz., superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), guaiacol peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6), and glutathione reductase (EC 1.6.4.2) and tolerated toxicity of Cd up to moderate concentration of 5 microM. At 10 microM exposure, enzyme activities declined and plants experienced toxicity, which was evident by the significant decrease in the photosynthetic pigments and by increase in the levels of H(2)O(2), lipid peroxidation and ion leakage. In conclusion, modulation of antioxidant system in a coordinated manner in response to Cd accumulation appears to help plants tolerate toxicity of Cd up to 5 microM.
水生系统中的镉（Cd）污染备受关注，因为它是一种非必需元素，积累后会阻碍植物生长。本研究的目的是调查狐尾藻（Ceratophyllum demersum L.）对镉的积累行为、诱导的毒性以及抗氧化系统的反应。将植物暴露于不同浓度的镉（0 - 10微摩尔）中1 - 7天。发现镉的积累是一种浓度-持续时间依赖性现象。在10微摩尔浓度下处理7天后，镉的最大积累量为1293微克/克干重。植物表现出各种抗氧化酶活性的显著刺激，即超氧化物歧化酶（EC 1.15.1.1）、抗坏血酸过氧化物酶（EC 1.11.1.11）、愈创木酚过氧化物酶（EC 1.11.1.7）、过氧化氢酶（EC 1.11.1.6）和谷胱甘肽还原酶（EC 1.6.4.2），并且在高达5微摩尔的中等浓度下耐受镉的毒性。在10微摩尔暴露时，酶活性下降，植物出现毒性，这通过光合色素的显著减少以及过氧化氢、脂质过氧化和离子渗漏水平的增加而明显表现出来。总之，响应镉积累以协调方式调节抗氧化系统似乎有助于植物耐受高达5微摩尔的镉毒性。
