This doctoral thesis investigated the impact of the arbuscular mycorrhizal (AM) symbiosis, an ubiquitous and beneficial association between plant roots and soil fungi, toward plant growth, stress tolerance, and metal uptake in relation to extrinsic metal conditions ranging from low (e.g. trace) to high (e.g. toxic) exposure levels. The investigative strategy is divided into two main parts: (1) statistical meta-analysis and (2) experimental analysis. In the first part, an extensive literature review in the field of metal phytoremediation was conducted in order to construct a meta-dataset consisting of various plant physiological and soil ecological parameters which were ultimately extracted from nearly 30 published works. Meta-analytical statistical tools were then used to examine general trends and perspectives in metal phytoextraction and metal stress tolerance (Chapter 2), to establish an inherent role for the AM symbiosis therein (Chapter 3), and to discuss the potential for plant investment in symbiotic associations as an extrinsic stress tolerance strategy in complement to the plant's intrinsic stress resistance mechanisms (Chapter4). From these findings, a series of conceptual models were proposed depicting the plant growth and metal uptake in relation to increasing metal exposure levels by integrating the primary AM-induced mechanisms of 'enhanced uptake' and 'metal biosorption'. In the second part, in vitro root-organ (Chapter 5) and greenhouse culture systems (Chapters 6 and 7) were designed using the micronutrient zinc (Zn) as a typical metal contaminant to test various parameters of AM-plant growth and metal uptake, for which the proposed conceptual models were used as a framework for developing new hypotheses regarding plant-soil interactions. The methods and analytical techniques included Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) for the determination of soil- and plant-Zn concentrations, differential root staining and microscopic analysis for the assessment of AM-root colonization, and standard physiological metrics for the determination of plant health 'status. In brief, I showed that the AM symbiosis plays a dynamic role in plant development and stress tolerance first by enhancing the uptake of limiting metal nutrients, and then by reducing the uptake of potentially toxic metal contaminants due to metal biosorption under metal toxicity conditions. Accordingly, I also suggested that such mechanisms contribute in buffering the proximal growth environment, and thereby increasing soil's resiliency. Altogether, I consider the revised models depicting the impact of the AM symbiosis on plant and soil systems to be a relevant tool in environmental remediation practices.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/30063 |
| Date | January 2011 |
| Creators | Audet, Patrick J |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 244 p. |
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