The role of fungi in diverse associations is presented with special reference to mycorrhiza and lichens. The benefits they confer on their partners in such mutual alliances accord them special recognition in ecology. . The report also goes into their classification and reproduction and overall econ...
1. MYCORRHIZA
A mycorrhiza is a symbiotic association between a fungus and the root of a higher plant. Advances in
mycology have expressed the possibility of in vitro mycorrhization between a select fungus and higher
plant. This can be seen in the association of fungi with Populus seedlings . The fungus is concerned with
water and nutrient uptake, while the plant is involved in food production through photosynthesis. When
they occur on the surface of the root, they are ecto-mycorrhizae and when they express inside the cells in
the root, they are called, endo-mycorrhizae.
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There are 4 general types of endo-mycorrhiza. These are arbuscular, orchid, arbutoid, and ectotrophic.
1.Arbuscular-This is the most common. Many of them are members of Zygomycetes. They form
arbuscules, which are swollen regions of mineral and water exchange
2.Orchid- This is a unique type in which some may not carry out photosynthesis before fruiting but
depends on the symbiotic invasion of the root by the fungus.. The plant therefore depends on the
mycorrhiza in order to get its nutrients.
3.Arbutoid-On the surface, it resembles ecto-mycorrhiza, by covering the root surface, however, the
difference is that this goes further into the cortex of the roots.
4.Ectotrophic-As the name suggests, they occur mostly on the covering and derives nutrients from the
plant root.
Reproduction in the arbuscular mycorrhiza is by the formation of thick walled resistant spores that are
capable of staying for long in the soil. The spores grow only in the presence of a compatible root Glomus
is a typical example. On getting the substrate, the spore goes through germination, root colonization,
exploration and network development
Mycorrhiza is beneficial because it
increases crop yield,
reduces disease occurrence,
reduces soil erosion,
optimizes fertilizer use,
improves drought resistance
enhances flowering and fruiting
promotes geo-nutrient cycling
2. LICHENS
This is a symbiotic association involving a fungus and an alga. The alga component is generally
unicellular like Chlorella, while the fungi partner are mostly members of the ascomycota and
basidiomycota. Each lichen is named after the fungal partner. For example, basidiolichen refers to a
thallus with a basidiomycete as the fungal component The alga supplies the food through photosynthesis
while the fungus presents the protection and also absorption of nutrients from the substrate. Structurally,
they are of 5 types.
Fruticose(tuft-like),
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