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Abstract Detail


Kaplan Memorial Lecture

Peterson, Larry [1].

Mycorrhizas - Co-ordinated development between plants and fungi.

The majority of vascular plant species have an intimate association with fungal symbionts, forming mycorrhizas. The fossil record has revealed that this is an ancient association with the success of the first land plants likely dependent on their fungal partners. Most mycorrhizas are examples of true mutualism with both partners benefiting from the association. Mycorrhizal fungi increase the surface area of plant roots for nutrient acquisition and in turn obtain carbon for growth and reproduction. However, plant species that lack chlorophyll depend on fungal connections to obtain carbon from photosynthetic plants; there is no evidence that the fungi receive any benefits from the association. These plants, known as myco-heterotrophs, are therefore cheaters. Mycorrhizas are categorized primarily on the interaction of plant roots with particular fungal species, resulting in characteristic changes in the morphology and cytology of both symbionts. In some cases, such as ectomycorrhizas, the morphology of the root system becomes highly modified resulting in morphotypes that can be useful in identifying the fungal symbiont involved. A critical stage in all mycorrhiza categories is the development of a nutrient-exchange interface between the symbiotic partners. With the exception of ectomycorrhizas, in which fungal hyphae develop external to epidermal and cortical cell walls, other mycorrhiza categories involve the penetration of root cell walls by fungal hyphae and the formation of highly modified fungal structures. In these latter cases hyphae are separated from the root cell cytoplasm by host-derived membrane (perifungal membrane) and a host-derived interfacial matrix consisting of molecules found in primary walls of plant cells. This matrix, which varies in composition depending on the mycorrhiza category, is deposited between the perifungal membrane and the hyphal wall forming an apoplastic compartment. The formation of the perifungal membrane and the deposition of matrix components into the apoplastic compartment involves the host cytoskeleton. Regardless of the structural nature of the nutrient-exchange interface, nutrients must pass into the symplast of both partners at some point. Modifications in host and fungal cell walls occur during the colonization process and specific membrane transporters are involved.

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1 - University of Guelph, Molecular and Cellular Biology, 50 Stone Rd East, Guelph, ON, N1G 2W1, Canada

Keywords:
mycorrhizae
nutrient exchange
Anatomy
roots.

Presentation Type: Special Presentation
Session: S4
Location: Franklin C and D/Hyatt
Date: Tuesday, July 10th, 2012
Time: 5:00 PM
Number: S4001
Abstract ID:141


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