【作者】 大宇（Muhammad Dawood）；

【导师】 邬飞波；

【作者基本信息】 浙江大学 ， 作物学， 2008， 硕士

【摘要】 土壤重金属污染正严重威胁着农产品的安全和人类健康。筛选鉴定抗/耐重金属的植物种/品种,探讨抗/耐性的生理生化机制,进而分离鉴定机关的特异基因.对于土壤重金属污染的植物修复具有重要的理论与实践指导意义。经野外调查,我们在浙江东南部地区三家开办了20余年的电镀厂周边受电镀废水、废弃物严重污染已无法种植农作物荒废多年的土壤上(土壤有效态Cr(VI)含量高达20mg/kg)发现了一种无铬中毒症状、生长旺盛、生物量大的多年生香蒲科香蒲属(Typhaceae)植物—狭叶香蒲(Typha angustifolia L.)。本研究采用盆栽试验,旨在探讨该狭叶香蒲对铬胁迫的耐性与相关的生理反应及其螯合剂诱导植物萃取污染土壤中重金属的可能性。主要研究结果如下:盆栽试验研究了狭叶香蒲对铬毒害的耐性,并分析测定了相应的生理反应指标。与无铬对照相比,50μM Cr(VI)处理略提高了狭叶香蒲的株高和生物学产量,100μM Cr(VI)处理对株高和生物学产量并无显著影响;铬浓度增至200-800μM,植株的株高和生物学产量显著下降,但即便是在最高铬浓度800μM Cr(VI)胁迫下,植株叶片仍未见明显的铬中毒症状(叶片上未见坏死斑点)。因此,我们可以得出结论,该植物能在800μM Cr(VI)处理下正常生长,且无明显的铬毒害症状:说明这种香蒲科植物是一种对铬毒害具有很强耐性的植物。铬超积累植物是指植株铬含量超过1000mg kg~-1 DW,迁移系数达到0.02-0.10的植物种/品种。而香蒲植株的铬含量相对较低,因此该植物可能主要通过严格控制铬的‘土壤-植物’、‘根系-叶片’的迁移,从而限制了植株各部分铬含量。生理分析结果显示,铬胁迫显著提高了SOD和POD活性:叶片和根系中Cr和Mn含量呈显著正相关.Cr和另外3种微量元素(Fe、Zn、Cu)也呈正相关,但未达到显著水平。因此,根据本试验结果,香蒲对铬的耐性与铬胁迫下SOD和POD酶活性增强、必需微量元素吸收转移效率提高有关。外源添加金属螫合剂促进植物吸收积累重金属是利用高生物量植物种进行植物修复的可行手段之一。盆栽试验以狭叶香蒲为材料,研究了外源添加EDTACA(柠檬酸)刘,植物萃取污染土壤中Cd、Cu、Pb和Cr的作用。结果表明,香蒲对重金属毒害具有很强的抗性,各种重金属胁迫下香蒲植株地上部并未表现出中毒症状(欠绿或坏死)。与对照相比,施加EDTA显著降低了植株的株高、生物量,并严重影响植株正常生长发育:2.5 mM和5 mM CA处理显著提高了根系的(?)重。外源添加EDTA和CA均使地上部Cd、Pb和Cr含量显著上升,其中以EDTA效果更为明显。处理25 d收获时,5 mM EDTA处理地上部Cd、Cr和Pb含量最高,而2.5 mM CA处理根系Pb含景最高。10 mM CA处理地上部Cd累积量比2.5 mMEDTA处理高出了36.9%,与10 mM EDTA处理基本持平:但10 mM CA处理地上部Pb累积量较EDTA处理低。同时,CA处理下根系Cd、Cu和Pb累积量及5 mM或10 mM CA处理下地上部Cr累积量显著高于对照和EDTA处理。外源添加EDTA和CA对地上部Cu的累积量均无显著影响。实验结果也发现,外源加入EDTA显著增强了Cu、Cr、Pb和Cd在土壤中的溶解性;相比之下,CA对土壤水溶性Cu、Cr和Cd的影响较小,对Pb没有影响。综上所述,与EDTA相比,CA是一种环境友好的外源重金属螯合剂以诱导提高香蒲植物葶取污染土壤中的重金属。更多还原

【Abstract】 Heavy metal pollution in soils poses a major environmental hazard to terrestrial plants.It is crucially important to identify appropriate plant species/genotypes which may resist/tolerate heavy metals or other contaminants to identify/study the related genes in order to remediate the contaminated environment.While,understanding physiological and biochemical mechanisms of heavy metal tolerance/resistance is fundamental for discovering or creating new metal resisting plant species.We found a kind of gramineous plant species,Typha angustifolia,with high resistance to Cr stress growing on a Cr-contaminated area.The present research was conducted for two successive growth seasons to evaluate its ability to tolerant Cr stress and the relevant physiological responses and the possible role in chelate-assisted phytoextraction of metal polluted soils. The results were as follows:Pot experiments were conducted to study the potential of T.angustifolia plants for Cr toxicity tolerance and subsequent physiological response involved in this phenomenon. Plants exposed to 50μM Cr(Ⅵ)showed a slight increase in plant height and biomass, compared with control,and there was no difference in these growth parameters between the plants exposed to 100μM Cr(Ⅵ)and control(0μM),while increasing Cr levels to 200-800μM induced a significant decrease in plant height and biomass,but without significant injured leaf symptoms of Cr toxicity(necrotic patches on leaf blade)even in 800μM treatment.Thus,it can be concluded that the plant can survive well in 800μM Cr stress.However,T.angustifolia plants demonstrated a relatively low Cr concentration in comparison with the plants classified as hyper-accumulators which require a concentration of at least 1000 mg Cr kg~-1 DW.with a translocation factor(TF)of 0.02 to 0.10 among different Cr treatments of this plant.Therefore,it can be concluded that the plant tends to restrict soil-plant and root-leaf transfer,and consequently has a lower Cr concentration in its tissues.Since the extraction of metal from Cr-amended medium depends on plant species,this plant,like many other plants,may have evolved Cr exclusion strate(?). Chromium induced significant increase in SOD and POD activities.Meanwhile. significantly positive correlation was detected between Cr and Mn or Cu in leaves,and roots,respectively,and slender positive correlation also occurred between Cr and the other three microelements in leaves and roots.The Cr tolerance of the plants appeared to be associated with the enhancement of SOD and POD activities and the improvement of the essential microelements uptake and translocation.Improvement of the capacity of plants to accumulate metals by the application of chelating agents provides a new possibility for phytoremediation using high biomass species.Pot experiment was conducted to study the performance of EDTA and citric acid (CA)addition in enhancing phytoextraction of Cd,Cu,Pb and Cr from artificially contaminated soil by T.angustifolia.The results demonstrated the remarkable resistance to heavy metal toxicity of T.angustifolia with no visual toxic symptoms such as chlorosis and necrosis on shoots of the plants exposed to metal stress.EDTA-addition significantly reduced plant height,biomass production and stunted plant growth compared with the control,while 2.5 and 5 mM CA addition induced significant increases in root dry weight. Both of EDTA and CA significantly increased shoot Cd.Pb and Cr concentrations compared with the control,with EDTA being more effective than CA.At final harvest,the highest shoot Cd,Cr,and Pb concentrations were recorded in 5 mM EDTA,while maximal root Pb concentration found in 2.5 mM CA treatment.However,shoot Cd accumulation of 10 mM CA treatment was 36.9%higher than that of 2.5 mM EDTA,and similar with 10 mM EDTA,but lower in shoot Pb accumulation relative to EDTA treatments.Meanwhile, root Cd,Cu and Pb accumulation of CA treatments and shoot Cr accumulation in 5 or 10 mM CA treatments was markedly higher than that of control and EDTA treatments.Both of EDTA and CA have no significant effects on shoot Cu accumulation.The results also showed that EDTA dramatically increased the dissolution of Cu,Cr.Pb and Cd in soil. while CA addition has much less effect on water-soluble Cu,Cr,and Cd,and no effect on Pb level.It may be suggested that CA can be regarded as a good chelate candidate for T. angustifolia as environmentally safe phytoextraction of Cd and Cr in soils.更多还原