【作者】 肖昕；

【导师】 冯启言；

【作者基本信息】 中国矿业大学 ， 环境科学， 2009， 博士

【摘要】 土壤重金属污染已成为我国粮食安全的主要隐患之一,而中低浓度重金属复合污染的毒理效应及其毒害机理目前研究尚少。本论文通过皿培实验和盆栽实验,系统地研究了土壤中Cu、Cd、Pb和Zn四种重金属在单一与两两交互作用下对小麦幼苗的毒理效应和重金属的动态富集规律,利用透射电镜研究了重金属污染对小麦幼苗的微观伤害,探讨了重金属胁迫下小麦过程中土壤酶对重金属的响应和重金属在小麦植株中的富集特征,主要结论如下:(1)系统地研究了重金属交互作用对小麦幼苗各生理特性的影响及重金属在小麦幼苗中的富集特征。结果表明,交互作用对小麦各生长及生理指标均有不同程度的拮抗作用,其中对根伸长的作用最大(变异系数最大),交互组合中各元素及其交互作用对Cu、Cd、Zn富集量的影响均达到显著水平以上,而对Pb富集量的影响均达到极显著水平,该结论为土壤重金属污染早期预测提供了依据。(2)通过对小麦根尖及叶片细胞亚显微结构的观测,分析了不同金属元素及其交互作用对小麦细胞的损伤机制及其在小麦细胞中沉积状态。微观测试表明,不同细胞器对重金属及其交互作用的响应存在较大差异,小麦细胞利用细胞壁的吸附作用和液泡储存作用减少重金属对细胞器的损伤,而重金属浓度突破植物抗性范围后会对线粒体、细胞核、叶绿体等细胞器造成严重的损伤,微观观测结果与理化分析结果一致。论文观测到了部分重金属交互胁迫下小麦幼苗细胞由完整到完全破坏的全过程,为进一步揭示复合重金属对小麦毒害的微观机制提供了理论依据。(3)利用盆栽实验,跟踪监测了小麦生长全过程中小麦根区与非根区土壤蔗糖酶活性、脲酶活性和过氧化氢酶活性对重金属及其交互作用的响应,发现重金属的胁迫对小麦根区与非根区土壤中蔗糖酶活性和尿酶活性总体表现为抑制作用,其抑制作用的强弱与重金属的胁迫量有关,而过氧化氢酶活性与小麦生长过程的相关性更显著;根区土壤蔗糖酶活性、脲酶活性、过氧化氢酶活性总体上大于非根区,根际效应对土壤酶活性的促进顺序为蔗糖酶活性>过氧化氢酶活性>脲酶活性。(4)利用正交实验系统地分析了小麦不同生长时期复合重金属在小麦植株中富集特性,结果表明:重金属在小麦各生长时期总体表现为根、茎和叶片中的富集量大于颖壳和籽实,且富集量与重金属胁迫量显著性相关;重金属交互作用下,不同生长时期小麦不同部位对重金属富集特征不同,总体而言生长前期>生长后期;小麦各部位中重金属的富集量大多与该金属的胁迫量显著性相关,且相关性随小麦的生长降低。(5)与食品卫生标准比较,单因子实验条件下小麦籽实中镉、铅、锌的含量均超过了食品卫生标准;重金属的交互作用在一定程度上扩大了小麦中重金属富集量的域值范围,且各金属含量均出现了一定程度的超标现象,其中Zn的超标率最大,而Cd的超标倍数最大,可以推断重金属污染区域烟农19小麦易受污染。更多还原

【Abstract】 Soil heavy metals pollution has become one of main potential hazards of food security. Nonetheless, there were less research on eco-toxicity and toxic mechanisms of mixed heavy metals with moderate and low concentration. Dish culture and pot culture experiments were carried out to study the toxicological effects of Cu, Cd, Pb, Zn and their binary mixtures on wheat. Damage of heavy metals on wheat seedlings were observed microscopically by Transmission Electron Microscopy. Responses of soil enzyme to heavy metal pollution and heavy metals enrichment characteristic of wheat were also studied during wheat upgrowth polluted by the heavy metals. The major conclusions were listed as follows:(1) Effect of binary heavy metal interaction on physiological characteristics of wheat seedling and heavy metals enrichment characteristics were systematically studied. The results showed that binary heavy metal interaction posed antagonism towards all physiological characteristics index to different degrees. And it affects root elongation the most significantly (coefficient of variation was the biggest). The actions of each heavy metal element and their binary mixtures on Cu, Cd, Zn enrichment were significant. And extremely significant enrichment of Pb was acquired due to the actions mentioned above. The conclusion provided evidence for prediction of soil heavy metal pollution..(2) Damage mechanism of heavy metals and their interaction on wheat cells and metals deposition state were studied by observation of ultrastructure of root-tip and leaves cell of wheat seedling using TEM. The observation indicated that the responses of different organelles to heavy metals and their interaction were different. Adsorption of wall and storage of vacuole and organelles could mitigate damage of wheat cells by heavy metals. Some organelles, such as mitochondria , nucleolus and chloroplast, would be damaged by heavy metals with high concentration that exceeding resistance range of wheat cell. The result of microscopic observation was in accordance with the result of physico-chemical analysis. The whole process that complete damage of wheat seedling cells stressed by some binary mixtures of heavy metals was experimentally observed, which established a theoretical foundation of further understanding of micromechanism of mixed heavy metals damage to wheat were .(3) Response of sucrase, urease and catalase activity in both rhizosphere and non-rhizosphere of wheat root to heavy metals and their interactions were tested continually by pot culture. The testing results indicated that sucrase and urease activity in both rhizosphere and non-rhizosphere were inhibited as stressed by heavy metals totally and the inhibitions were related to the concentration of heavy metals while catalase activity was more correlated with wheat growth. Generally sucrase, urease and catalase activity in rhizosphere were bigger than that in non-rhizosphere and the order of rhizosphere effect promoting soil enzyme was sucrase activity>catalase activity> urease activity.(4) Orthogonal experiments was carried out systematically to study mixed heavy metals enrichment in wheat during wheat growth. The results showed that heavy metals in roots, stems and leaves were more than that in glumes and seeds as stressed by heavy metal during the wheat growth and the enrichment amount was related to the heavy metal concentration. The heavy metal enrichment varied in different growth stages of different part of wheat stressed by mixed heavy metals. Generally, the heavy metals enrichment in early growth stage is bigger than that in later growth stage. Most of the enrichment amount of heavy metals in wheat were significantly correlated to the concentration of the heavymetal and the correlation decreased with wheat growth.(5) Cd, Pb, Zn concentration in seed exceeded sanitary standards for foods as stressed by single heavy metal. The ranges of heavy metals enrichment amount were enlarged by interaction of mixed heavy metals to some extent. Each heavy metal exceeded the standards to some degree. Zn had the most ratio of exceeding the standards. And Cd had the most times of exceeding the standards. It’s concluded that Yan-nong 19 is easy to be contaminated as planting in the heavy metals polluting areas更多还原