铜对小白菜的毒性效应及其生态健康指标

Toxic effects of copper on Chinese cabbage and its ecological health parameter

以小白菜地上部分及根系重量、叶绿素值（SPAD值）以及与抗逆性有关的丙二醛（MDA）、超氧化物歧化酶活性（SOD）、脯氨酸含量等作为毒性指标，研究了0～400mg／kg外源铜对青紫泥小白菜生长的影响，并应用“生态剂量”概念计算青紫泥栽培小白菜的铜污染安全指标及食品卫生指标。结果表明，低浓度铜（〈100mg／kg）显著增加小白菜鲜重，高浓度铜（〉200mg／kg）则造成小白菜减产，400mg／kg的外源铜使小白菜减产84％；铜污染使根系重量下降表现出与地上部分同样的趋势。SPAD值随铜污染浓度的增加而呈线性下降；铜污染浓度低于100mg/kg有促进根体积、根长度、根表面积增加的趋势，但超过200mg／kg的铜浓度则显著降低根长、根体积和根表面积。在与重金属污染引起的抗逆性有关的牛理生化指标中，脯氨酸最为敏感，铜浓度小于50mg／kg或大于200mg／kg都能显著影响脯氨酸含量及SOD活性；与脯氨酸的变化一样，高浓度铜增加了MDA含量；青紫泥铜污染的临界指标为171mg／kg。

Copper is an essential element for the health of plants. But excessive copper has a detrimental negative effect on plant growth. Therefore, the diagnosis of soil copper contamination is one of the most important component parts in soil cleanup processes. This study was conducted to determine the toxic effect of Cu pollution on Chinese cabbage （ Brassica Chinensis） growth, and on its physiological activity. Shoots and roots production, malondialdehyde （MDA）, superoxide dismutase （SOD） and proline of Chinese cabbage were used as bioindicators of the toxic effect of Cu. The inhibition of physiological activity and biomass by different Cu concentrations ranging from 0 to 400 mg/kg soil was described by a mathematical model in order to calculate the ecological limitation value of Cu pollution. In the present study, 84% decrease of fresh shoot mass was observed at 400 mg/kg Cu loading. Similarly trend was found in root. Increased Cu load- ing caused a linear decrease of SPAD value. Nearly 2/3 of Cu is retained by the roots and only 1/3 is transported to the shoots. Cu concentrations lower than 100 mg/kg has a trend to promote the increases of root volume, root surface area, and root length. However, higher Cu loading （ 〉 200 mg/kg） significantly reduced the length, volume, and surface area of Chinese cabbage root. In the work reported here, it seems that proline is highly susceptible to Cu toxicity. The proline and SOD were affected severely not only by low concentration of external Cu （ 〈 50 mg/kg） but also by high level of it （ 〉 200 mg/kg）. There was a stimulation of MDA content at high Cu level. A much higher ED10 value threshold （ 171 mg/kg） was calculated and demonstrated the necessity of phototoxicological test according to different soil conditions. A similar quantity of Cu was calculated from fresh base of Chinese cabbage shoot mass.