When ancient plants first evolved to live on land, they found a harsh and unforgiving environment. On land, water and nutrients are much more difficult to acquire. Compared to the watery habitats they came from, plant roots on land are not surrounded by limitless resources. Chance encounters with several species of fungi forged a timeless and important symbiosis. These fungal symbionts greatly improved the water and mineral uptake of their host plants. In return for these increased resources, the fungi are “paid” in sugars produced by the plant. The term mycorrhiza or “root fungus” is used to describe this uniquely beneficial relationship. Depending on the type of fungi and how they infect the plant, mycorrhizal fungi can be broken into two main categories.
Ancient Plants: The Inside Job
Endomycorrhizal fungi have unique traits that separate them from other forms of mycorrhizal fungi. First, they can enter plant cells in the cortex (part of the root). Once inside the cells, they set up special structures called arbuscules. These small “trees” within the plant cell trade water and minerals for sugars. Another unique feature is the absence of sexual reproduction in endomycorrhizal fungi. Instead of making mushrooms to reproduce, they form asexual spores. These clonal bodies maintain the species. Endomycorrhizal fungi are commonly found on many plants including most annual vegetables and ornamental plants.
Ancient Plants as an Outside Ally
Unlike endomycorrhiza, ectomycorrhiza are not able to enter the plant’s cells. Instead, they form a specialized structure between the cells in the cortex. This structure is called the Hartig net. The netting trades nutrients and water for sugars. Ectomycorrhizal fungi also cover the exterior of the plant’s roots with a mantle, or fungal covering. This covering suppresses the growth of root hairs, but the fungus makes up for this by extending the “reach” of the plant’s root system with fungal hyphae (root-like structures of the fungus). Ectomycorrhiza fungi are primarily found in association with shrubs, woody plants, and trees and produce mushrooms to spread their spores.
This age-old partnership has been a boon for both organisms. The plants have gained access to more water and nutrients. Something that would be much harder without the fungi. The fungi, in return, gain a food source in the form of carbon. This carbon-based “economy” is what drives the whole relationship. Whether an endomycorrhiza or ectomycorrhiza, this ancient plant symbiosis is crucial to the success of land plants.
This information was compiled by Mack Lessig, Community Gardens Program Coordinator for Manatee County Department of Parks and Natural Resources, Ag and Extension Services Division in partnership with the University of Florida/IFAS. 941-722-4524 Ext 1821 or MLessig@ufl.edu
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