The Mycorrhizal Network: Difference between revisions
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Mycorrhizae is the symbiotic relationship between fungi and plants. Mycelium, the vegetative part of a fungus, extends in a branching network of hyphae, that secrete enzymes and break down organic material into nutrients for its growth. The hyphae colonize the root system of plants, providing the photosynthetic organisms with nutrients and water in exchange for carbohydrates that the fungi cannot produce on its own being heterotrophic. This colonization may be intracellular as ectomycorrhizal fungi that envelop roots, or extracellular as arbuscular mycorrhizal fungi (AMF) which trade nutrients via a signal transduction pathway. | Mycorrhizae is the symbiotic relationship between fungi and plants. Mycelium, the vegetative part of a fungus, extends in a branching network of hyphae, that secrete enzymes and break down organic material into nutrients for its growth. The hyphae colonize the root system of plants, providing the photosynthetic organisms with nutrients and water in exchange for carbohydrates that the fungi cannot produce on its own being heterotrophic. This colonization may be intracellular as ectomycorrhizal fungi that envelop roots, or extracellular as arbuscular mycorrhizal fungi (AMF) which trade nutrients via a signal transduction pathway. | ||
==Evolution of Mycorrhizae== | |||
Evolution of Mycorrhizae | Fossil records indicate that mycorrhizal fungi predates the evolution of vascular plants, about 460 million years ago in the Ordovican period (Redecker et al. 2000). The presence of these fungi were involved in the development of soil and the evolution and colonization of vascular land plants, specifically by aiding the non-vascular plants with acquisition of nutrients through fungal hyphae, as the “soil” lacked a significant amount of nutrients for terrestrial plants to survive without their fungal symbionts (Pirozynski and Malloch 1975). As the fungi cycles nutrients to the plants the fungus receives and fixes carbon into the ground, and assists in oxygenation of the atmosphere (Mills et al. 2018). In a study by Krings et al (2007) fossil evidence from the Rhynie chert sediment of the Early Devonian period suggests that fungal endophytes, specifically those which colonize the rhizoids of <i>Nothia aphylla</i>, actively influenced the evolution of these plants due to observed host responses. The responses to fungal infection in <i>N. aphylla</i> - rhizoid bulging, separation of infected cells via thickening of cell walls, and the motile inhibition of hypha - suggests its susceptibility to colonization by fungi at least 400 million years ago, advancing selection between plant species with the increasing complexity of interspecies interactions (Krings et al. 2007). | ||
Fossil records indicate that mycorrhizal fungi predates the evolution of vascular plants, about 460 million years ago in the Ordovican period (Redecker et al. 2000). The presence of these fungi were involved in the development of soil and the evolution and colonization of vascular land plants, specifically by aiding the non-vascular plants with acquisition of nutrients through fungal hyphae, as the “soil” lacked a significant amount of nutrients for terrestrial plants to survive without their fungal symbionts (Pirozynski and Malloch 1975). As the fungi cycles nutrients to the plants the fungus receives and fixes carbon into the ground, and assists in oxygenation of the atmosphere (Mills et al. 2018). In a study by Krings et al (2007) fossil evidence from the Rhynie chert sediment of the Early Devonian period suggests that fungal endophytes, specifically those which colonize the rhizoids of Nothia aphylla, actively influenced the evolution of these plants due to observed host responses. The responses to fungal infection in N. aphylla - rhizoid bulging, separation of infected cells via thickening of cell walls, and the motile inhibition of hypha - suggests its susceptibility to colonization by fungi at least 400 million years ago, advancing selection between plant species with the increasing complexity of interspecies interactions (Krings et al. 2007). | |||
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Revision as of 22:22, 6 April 2021
Section
By Freya Beinart
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Mycorrhizae is the symbiotic relationship between fungi and plants. Mycelium, the vegetative part of a fungus, extends in a branching network of hyphae, that secrete enzymes and break down organic material into nutrients for its growth. The hyphae colonize the root system of plants, providing the photosynthetic organisms with nutrients and water in exchange for carbohydrates that the fungi cannot produce on its own being heterotrophic. This colonization may be intracellular as ectomycorrhizal fungi that envelop roots, or extracellular as arbuscular mycorrhizal fungi (AMF) which trade nutrients via a signal transduction pathway.
Evolution of Mycorrhizae
Fossil records indicate that mycorrhizal fungi predates the evolution of vascular plants, about 460 million years ago in the Ordovican period (Redecker et al. 2000). The presence of these fungi were involved in the development of soil and the evolution and colonization of vascular land plants, specifically by aiding the non-vascular plants with acquisition of nutrients through fungal hyphae, as the “soil” lacked a significant amount of nutrients for terrestrial plants to survive without their fungal symbionts (Pirozynski and Malloch 1975). As the fungi cycles nutrients to the plants the fungus receives and fixes carbon into the ground, and assists in oxygenation of the atmosphere (Mills et al. 2018). In a study by Krings et al (2007) fossil evidence from the Rhynie chert sediment of the Early Devonian period suggests that fungal endophytes, specifically those which colonize the rhizoids of Nothia aphylla, actively influenced the evolution of these plants due to observed host responses. The responses to fungal infection in N. aphylla - rhizoid bulging, separation of infected cells via thickening of cell walls, and the motile inhibition of hypha - suggests its susceptibility to colonization by fungi at least 400 million years ago, advancing selection between plant species with the increasing complexity of interspecies interactions (Krings et al. 2007).
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Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2021, Kenyon College.
