| 题名 | 丛枝菌根对植物体内砷的累积分配和形态转化的影响 |
| 作者 | 任百慧 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 陈保冬 |
| 关键词 | 丛枝菌根 蒺藜苜蓿 水稻 砷 累积 形态 arbuscular mycorrhiza Medicago truncatula rice arsenic accumulation speciation |
| 其他题名 | Effects of Arbuscular Mycorrhiza Symbiosis on As Accumulation, Distribution and Speciation in Host Plants |
| 学位专业 | 生物工程 |
| 中文摘要 | 砷污染会造成土壤环境质量下降，当其在土壤中积累到一定程度时就会对土壤-植物系统产生毒害和破坏作用。砷还能够通过生物富集作用，经食物链传递危及人类健康。正是由于砷污染的严重性和普遍性，对砷污染问题的研究已成为农业、生态和环境科学研究领域的前沿和热点。 菌根技术作为一种生物技术，对于高效利用中等或轻度砷污染土壤具有一定的现实意义。丛枝菌根真菌作为一种能够与大多陆生植物共生的土壤微生物，能够通过增强宿主植物对养分以及水分的吸收，显著促进植物的生长，从而提高植物对砷污染的适应性。然而，菌根共生体如何影响植物对砷的吸收累积和形态转化，从而提高植物对砷的耐受能力，对于这方面的研究工作还很少。这也是本论文的研究重点。 本论文着眼于砷胁迫下丛枝菌根对植物吸收累积砷和砷形态变化的影响，旨在揭示菌根共生体减轻植物砷毒害的机制。本研究的主要内容及结果归纳如下： （1）以蒺藜苜蓿为研究对象，将其种植在含有不同磷浓度的砷污染土壤中，在土壤灭菌的条件下，通过接种菌根真菌与不接种对照处理以了解在磷砷交互作用下接种丛枝菌根真菌对苜蓿吸收及累积砷的影响。试验结果表明，在砷污染条件下，菌根真菌改善了蒺藜苜蓿磷营养状况、增加了生物量并减少了植物对砷的吸收，增强了植物对砷污染的适应性，而且在土壤磷营养状况越匮乏时，菌根真菌帮助植物抵抗砷污染的效果越明显。通过对植物体内砷形态的检测发现，仅在菌根植物的地上部检测到了甲基砷的存在，而且菌根植物中三价砷在总砷中的比例相对更高，表明丛枝菌根真菌可能在将无机砷转化为毒性更低的甲基砷，以及在五价砷还原为三价砷的过程中发挥了的重要作用，从而缓解了砷污染对植物的毒害效应。 （2）选取野生型蒺藜苜蓿以及相应的不能被菌根真菌侵染的突变体蒺藜苜蓿种植在没有灭菌的自然砷污染土壤中，从而揭示土著丛枝菌根真菌对苜蓿吸收及累积砷的影响。试验结果表明，相比与突变体苜蓿，野生型苜蓿的植株干重、磷浓度以及三价砷的比例会更高，而砷浓度却更低。试验结果表明菌根真菌在自然砷污染土壤中对于缓解植物砷毒害具有潜在重要作用。 （3）以水稻为研究对象，选取砷耐受型和砷敏感型的品种研究在旱作与淹水处理下丛枝菌根真菌对于水稻体内砷的累积及形态的影响。试验结果表明，无论在淹水还是旱作条件下菌根真菌与水稻都能形成良好的共生体系，然而在淹水条件下菌根侵染率要显著低于旱作条件下。相比而言，淹水处理下水稻籽粒与秸秆的生物量要显著低于旱作处理下，而根系砷浓度要显著高于旱作处理下，砷的生物有效性会显著提高。尽管接种处理相对抑制了水稻的生长，但却显著增加了砷耐受型品种水稻体内甲基砷的比例，一定程度上缓解了砷污染对植物的毒害。与砷敏感型品种相比，砷耐受型品种水稻籽粒中磷浓度会更高，总砷和无机砷的浓度会更低，甲基砷所占的比例会更高，对于砷污染的胁迫具有一定的抵抗能力。水稻品种与接种处理以及与水分处理的交互作用在籽粒砷浓度上表现出了显著的差异，揭示了不同品种水稻在菌根真菌作用下以及在不同水分处理下对砷吸收转化机制的异同。本研究为在砷污染条件下，如何保障水稻的安全生产提供了科学依据。 本论文通过模拟试验揭示了丛枝菌根对植物体内砷的累积分配和形态转化的影响，深化了有关菌根共生体参与生态系统中砷的迁移、转化、富集、毒害、解毒和抗性等过程的认识，也为利用菌根技术实现有限土壤资源的可持续利用及农产品的安全生产提供了理论基础。 |
| 英文摘要 | Arsenic (As) contamination is one of the major reasons for the deterioration of soil quality. Excessive As in the soil not only poses serious hazards to the soil-plant system, but also poses a great threat to human health via the food chain. Thus studies on As pollution have become hot topics in the field of agriculture, ecology and environmental science in recent years. As an environment-friendly biotechnology, mycorrhizal technology has some practical significance for the utilization of As contaminated soils. Arbuscular mycorrhizal fungi (AMF), as an important group of soil fungi, can form symbiotic association with the vast majority of the land plant families. AMF can significantly increase the absorption of mineral nutrients and water and subsequently promote the growth of host plants, thereby improving the adaptability of plants to As contamination. However, direct evidences are still lacking as for the role of AMF in As detoxification, particularly by affecting As accumulation and speciation in host plants. This thesis focuses on the effects of AMF on As accumulation and speciation in host plants and the underlying mechanisms so as to reveal the significance of AM fungi in plant tolerance to As toxicity. The main contents and results of this study are summarized as follows: （1）Medicago truncatula was used as test plant and grown in As-contaminated soil amended with different levels of P in order to reveal the involvements of AM fungus in plant As metabolism and the potential influences of P-As interactions on the mycorrhizal functions. The results indicated that the plant biomass in both experiments was dramatically enhanced by AM symbiosis. Mycorrhizal colonization enhanced As tolerance of M. truncatula by improving plant P nutrition and restricting As uptake. Host plants relied more on AMF for P acquisition under low P supply. Dimethylarsenic acid (DMA) was detected only in shoots of mycorrhizal plants, and mycorrhizal inoculation generally increased the percentage of arsenite in total As both in shoots and roots, indicating that AMF are most likely involved in the methylating of inorganic As into less toxic organic DMA and in the reduction of arsenate to arsenite, and thereby alleviating As toxicity in host plant. （2）Wild type and the mutant (TR25:3-1), which cannot be colonized by AMF, of M. truncatula were grown in unsterilized As-contaminated soil in order to investigate the effects of indigenous mycorrhizal fungi on As speciation and detoxification in host plants. Compared with the mutant, the wild type M. truncatula exhibited a higher plant dry weights, P concentrations, proportion of As(III) and lower As concentrations, suggesting that AM fungi do play an important role in alleviation of As phytotoxicity under natural conditions. （3）Arsenic accumulation and speciation in As sensitive and tolerant rice cultivars associated with AMF were examined under both aerobic and flooded conditions. The results showed that mycorrhizal symbiosis was well established in the roots of both rice cultivars, despite the colonization rate was much lower under flooded conditions. Compared with the aerobic condition, flooding cultivation decreased the yield of both grain and straw and increased As concentrations in roots. Although the growth of rice was inhibited by mycorrhizal colonization, mycorrhiza generally increased the percentage of organic As, and thereby alleviating As phytotoxicity. Compared with As sensitive rice cultivar, As tolerant cultivar exhibited a higher P concentrations and proportion of organic As and a lower total as well as inorganic As concentrations in grain. The study provided scientific basis for the safe production of rice in As contaminated soils. In conclusion, the study provided not only further evidence for the protective effects of AMF on host plants against As contamination, but also set theoretical basis for mycorrhizal remediation of As contaminated soils. |
| 公开日期 | 2015-07-07 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/15615]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 任百慧. 丛枝菌根对植物体内砷的累积分配和形态转化的影响[D]. 北京. 中国科学院研究生院. 2014. |
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