Question No. 6

What do fungi regulate on our planet?
Answered 10 April 2006.
Question author: anonymous.
Asked 11 March 2006.

Lichens: symbiosis of a fungus and an alga

Lichens: symbiosis of a fungus and an alga

Fungi are heterotrophic immobile organisms decomposing the organic matter back into inorganic compounds that are again utilized by plants for new synthesis and growth. If fungi and other heterotrophic organisms had not been decomposing the organic matter, the stores of inorganic substances needed for plant life (e.g., carbon dioxide) would have been exhausted on Earth in a dozen of years (see, e.g., Section 2.1 of Gorshkov et al. (2004)). Plants would have died and biosphere degraded.

Fungi species producing edible biomass in conspicuous quantities, i.e. edible mushrooms, constitute a minor part of all fungi species inhabiting our planet. Many of the nearly a hundred thousand fungi species are represented by what we commonly refer to as mold.

Over 90% of all organic matter synthesised by plants is decomposed by bacteria and fungi in approximately equal shares. The rate of synthesis of organic matter by plants is limited from above by the magnitude of the incoming flux of solar radiation. In the meantime, decomposition of organic matter by bacteria and fungi can occur at any rate dependent on the population numbers of these organisms. Thus, the activity of fungi regulates the amount of organic and inorganic matter in the ecosystem, supplying plants with the necessary inorganic substances, decomposing dead organisms and eliminating weak and ill living organisms. Moreover, some plants do not grow at all without a particular type of symbiotic root fungi — mycorrhizae. Thus, due to their tight coupling with plant functioning, fungi represent one of the major elements of the biotic regulation of the environment.