不同生态型蜈蚣草砷吸收差异特征及其机理

发布时间：2018-10-11 12:12

【摘要】：土壤砷污染是全球尤其是东南亚和中国非常突出且亟需解决的环境问题。自从砷超富集植物——蜈蚣草(Pteris vittata L.)发现以来,一直是国内外学者研究的热点。深入理解蜈蚣草体内砷代谢和富集机制是有效利用植物修复技术治理砷污染土壤的关键。在长期的自然进化过程中,蜈蚣草逐渐分化出不同生态型,已有研究结果显示:不同生态型蜈蚣草在砷吸收、富集方面存在显著差异。然而,不同生态型蜈蚣草砷吸收差异特征及其机理尚不清楚。本文通过野外调查、室内植物水培、土培和人工模拟等方法从吸收动力学、根系分泌物和砷酸还原酶3个方面探究不同生态型蜈蚣草砷吸收差异机理,初步得出如下结论:(1)在磷处理条件下,污染生态型及非污染生态型蜈蚣草根系对As(V)的吸收均符合米氏吸收方程。在磷处理条件下,非污染生态型具有较低的Km值,对As(V)的亲和力较污染生态型强,其α值(α=Vmax/Km,反映根系对离子的实际吸收能力,α值越大,吸收能力越强,反之则越弱)也高于污染生态型。随着磷浓度升高,污染生态型和非污染生态型对As(V)的亲和力均减小,实际As(V)吸收速率降低。(2)As(III)处理下,无论是污染生态型还是非污染生态型蜈蚣草对砷的吸收效率均比As(V)处理时高,但是砷从根部向地上部转移的能力弱于As(V)处理。(3)不同砷形态[As(V)和As(III)]对蜈蚣草根系分泌物的数量和种类无显著性影响。4种生态型蜈蚣草根系分泌的有机酸中主要以草酸为主,非污染生态型与污染生态型相比分泌更多的草酸。(4)非污染生态型蜈蚣草根系分泌物对土壤砷的活化能力优于污染生态型,室内模拟实验进一步表明:根系分泌物中的草酸对土壤砷的活化发挥显著作用。(5)不同生态型蜈蚣草地上部中砷形态分布存在明显差异:非污染生态型地上部As(III)的浓度显著高于污染生态型,其地上部中As(III)所占的比例也明显高于污染生态型。(6)不同生态型蜈蚣草之间根系砷酸还原酶活性存在显著差异,非污染生态型与污染生态型相比具有更高的的砷酸还原酶活性。
[Abstract]:Arsenic pollution in soil is an important environmental problem in the world, especially in Southeast Asia and China. Since the arsenic Super-enrichment Plant, Pteris vittata (Pteris vittata L.) Since its discovery, scholars at home and abroad have been the focus of research. Understanding the mechanism of arsenic metabolism and enrichment in Pteris vittata is the key to effectively use phytoremediation technology to control arsenic contaminated soil. In the long-term natural evolution process, Pteris vittata gradually differentiated into different ecotypes. The results showed that there were significant differences in arsenic absorption and enrichment between different ecotypes of Pteris vittata. However, the characteristics and mechanism of arsenic absorption in different ecotypes of Pteris vittata are unclear. In this paper, through field investigation, indoor plant hydroculture, soil culture and artificial simulation, the mechanism of arsenic absorption in different ecotypes of Pteris vittata was explored from three aspects: absorption kinetics, root exudates and arsenate reductase. The main conclusions are as follows: (1) under phosphorus treatment, the absorption of As (V) by the roots of Pteris vittata (Pteris vittata) was in accordance with the Michelson equation. Under phosphorus treatment, the non-polluted ecotypes have lower Km value and stronger affinity to As (V) than polluted ecotypes. The 伪 value (伪 = Vmax/Km,) reflects the actual absorption ability of the roots, and the higher the 伪 value, the stronger the absorption ability. On the contrary, the weaker) is also higher than the pollution ecotype. With the increase of phosphorus concentration, the affinity of polluted ecotypes and non-polluted ecotypes to As (V) decreased, and the actual As (V) absorption rate decreased. (2) under the treatment of) As (III), The arsenic absorption efficiency of Pteris vittata, whether polluted ecotype or non-polluted ecotype, was higher than that of As (V) treatment. However, the ability of arsenic transfer from root to shoot was weaker than that of As (V) treatment. (3) different forms of arsenic [As (V) and As (III)] had no significant effect on the number and species of root exudates of Pteris vittata. Oxalic acid was the main organic acid secreted by the roots of four ecotypes of Pteris vittata. Compared with the polluted ecotypes, the non-polluted ecotypes secreted more oxalic acid. (4) the root exudates of Pteris vittata, a non-polluted ecotype, could activate arsenic in soil more effectively than the polluted ecotypes. The results of laboratory simulation further showed that oxalic acid in root exudates played a significant role in the activation of arsenic in soil. (5) there were significant differences in the distribution of arsenic forms in the upper part of different ecotypes of centipede grassland: the above ground As (III) of non-polluted ecotypes. The concentration was significantly higher than the pollution ecotype, The percentage of As (III) in shoot was also significantly higher than that in polluted ecotype. (6) there were significant differences in arsenate reductase activity among different ecotypes of Pteris vittata, and non-polluted ecotypes had higher arsenate reductase activity than polluted ecotypes.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X173;X53

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