6.5 Fungi: Biodiversity, ecology and use

Fungi are vital parts of the ecosystem, but we know very little about them. About 70,000 species of fungi are recognized and described of the 1.5 million extant taxa. That means only about 5% of the fungal world is known to us.

Fungi are extraordinarily diverse in form, structure, function and habitat. Nearly all are microscopic. The body of a fungus is composed of a filamentous web-like structure, the "mycelium"

Fungi

What are fungi?

Fungi may rival flowering plants in their species diversity. They outweigh the animal kingdom in their variety of form and structure.

Fungi are an integral part of the ecosystem. They are present in land, forests, soil, water, air--everywhere.

They are a unique group of organisms in the living system. Fungi are not plants because they have no green chlorophyll. They depend for their sustenance on living (or dead) plants, animals or other organisms.

The fungi break down a huge range of organic substances: chitin (the external skeletons of insects), keratin (skin, hair, horn, and feather), cellulose (most plant debris), lignin (wood) and even petroleum, plastic and DDT. They are the world's number one recyclers!

Common fungi include breadmould, watermould, yeast, mush rooms. puffballs. rusts. smuts. ergot. blights. and mildews

Fungi in history Fungi such as mushrooms and morels have been known to humans from early times. Vedic and mythological writings refer to fungi, e.g., Soma of Aryans. Fungi have attacked crops since the dawn of agriculture: e.g., rusts, smuts and blights of cereals; mildews; the Irish potato famine; the Wollo famine of Africa.

Fungal spores: Fungi reproduce by forming tiny spores, the fungal equivalent of seeds. Every breath we take is laden with fungal spores. A single mushroom produces millions of spores. Spores:

· Are dispersed by wind, water, insects or other animals.
· Survive unfavourable conditions for long periods.
· Come in a dazzling array of forms.
· Vary in diameter from 0.5 to 50 rum.

Fungi

Fungi in Western Ghats forests

Luxuriant forests flourish on the warm, humid, western side on the Western Ghats escarpment. Although about 13,000 species of fungi have been recorded, the mycota of this region are still largely unknown. More research is needed to explore the fungal riches of the region.

Mycorrhizae: Symbiosis between plants and fungi

Mycorrhizae are fungi which exploit large volumes of soil and have an intricate association with plants to meet their basic need: energy-rich carbon compounds. They take phosphorus from the soil and pass it on to plants-in exchange for photosynthates from the plants.

Mycorrhizal plants perform well in infertile soils, withstand heavy metal and acid rain pollution, mining soils, extremely acid or alkaline soils, and so on. They help plants overcome the shock of transplanting, so are very valuable in afforestation programmes.

Although about 300,000 plant species are believed to have mycorrhizae, only 130 species of mycorrhizal fungi have so far been described.

Western Ghat forests are gene banks of mycorrhizal fungi. We should look for them, study them and put them into use in agriculture and forestry.

Biological control of mosquitoes using fungi

One day, it may be possible to control mosquitoes using fungi.

Mosquitoes carry various human diseases-such as malaria, dengue fever and Japanese encephalitis. They breed and lay eggs in stagnant ponds and ditches. About 6 species of fungi are known to infect mosquitoes.

The bacteria Bacillus thuringiensis and B. sphaericus are used to control mosquitoes. It may be possible to develop certain fungi to control these insects, too.

Western Ghat streams, fields, ponds and other natural water bodies are storehouses of these fungi.

Decomposition of dung

We may turn up our noses, but dung is an important energy resource in forest and grassland ecosystems.

Some fungi are specialist dung decomposers. Dung cannot be decomposed completely without fungi.

Fungi are intimately involved with herbivorous animals. An example is Pilobolus. Several species are known from the Western Ghats. This fungus can shoot out spores onto vegetation up to 3 meters away. The spores germinate only if they pass through the gut of herbivorous animals.

Litter decomposition in forests Fungi and other organisms degrade the leaves, twigs and other organic litter that fall to the forest floor all year round. Different fungi decompose different substances. In general: Mucoraceous fungi decompose sugar Ascomycetous forms decompose cellulose (e.g., leaves) Basidiomycetes decompose lignin (e.g., tree bark).

Fungi in poetry The great Persian poet Omar Khayyam wrote... "A loaf of bread, a jug of wine, and thou!" Bread and wine are both made with fungi.

Three types of fungi

Fungi in stream ecosystems

Many rivers flow from the Western Ghat hills to the sea. Several types of aquatic fungi are important in the stream ecosystem.

Fungi in stream ecosystems

Invertebrates such as crustaceans living in the stream cannot directly consume leaves that fall into the water. Fungi colonize these leaves and condition them so they can be eaten by invertebrates. These crustaceans in turn form food for fish in the stream.

Aquatic fungi are sensitive to organic pollution. They are unable to tolerate water contaminated by material such as nitrogenous fertilizers, fungicides and insecticides.

Fungi in stream ecosystems

Prepared by Dr. D. J. Bhat