Reproduction in Fungi

Both asexual and sexual reproduction take place in fungi and there is no sexual reproduction in imperfect fungi.

A typical Fungi

Mutualistic Fungi

Mutualistic Fungi

Mutualism is the association in which both partners are benefited. The two key mutualistic symbiotic association formed by the Fungi are lichens and mycorrhizae.

A) Lichens:

Lichens are an association between a fungus (mostly Ascomycetes and imperfect fungi and a few basidiomycetes) a cyanobacterium and green alga. The body of a lichen has three layers:

(1) The upper layer is thin and tough which consists of fungal hyphae.
(2) The middle layer consists of fungal hyphae interwoven with photosynthetic cell.
(3) Bottom layer consists of loosely packed fungal hyphaes.
The specialized fungal hyphae which penetrate or envelope the photosynthetic cells, transfer nutrients directly to the rest of the fungus. Three types of lichens are recognized:

1) Crusticose Lichens:

These are compact, often seen on bare rocks or on tree bark.

2) Foliose Lichens:

These are leaf like.

3) Fruticose Lichens:

These are shrub like and branched.

The lichens vary in color, shape, over all appearance, and growth form. Lichens are efficient at acquiring nutrients and moisture. and therefore, they can survive in areas of low moisture and low temperature as well as areas with poor and no soil.

They produce and improve the soil, thus making it suitable for plants to invade the area. Unfortunately, lichens also take up pollutants and cannot survive where air is polluted. Therefore, their presence is a bioindicator that the air is healthy for humans to breathe.

B) Mycorrhizae:

Mycorrhizae are mutualistic relationships between soil fungi and the roots of most plants. This association occurs in 95% of all families of higher plants.

Fungal hyphae increases the amount of soil contact and total surface area for absorption. The hyphae help in the direct absorption of phosphorus, zinc, copper and other nutrients from the soil into the roots.

Plants whose roots are invaded by mycorrhizae grow more successfully than do plants without mycorrhizae.

There are two types of mycorrhizae in which mycelium extends far out into the soil.

1. Endomycorrhizae: 

Penetrate only into the cell wall of outer cells of plant root forming coils, swellings and minute branches and also extend out into sorrounding soil.

2. Ectomycorrhizae:

Form a mantle that is exterior to the root,  and they grow between cell walls. These are mostly formed with pines, firs, etc.

Nutrition in Fungi

Nutrition in Fungi

Absorptive Heterotrophs:

Fungi obtain their food by direct absorption from the immediate environment, and are thus absorptive heterotrophs.

Saptrotrophs or Saprobs:
Fungi secrete digestive enzyme. The enzymes breakdown dead organic molecules. The organic molecules thus produced are absorbed by the fungus. Saprobic fungi anchor to the substrates by modified hyphae, the rhizoids.

Decomposers:
Fungi decompose cellulose and lignin, the main component of plant cell wall, which most bacteria cannot break.

Parasites:
Parasitic fungi absorb nutrients directly from the host cytoplasm with the help of haustoria, which are special hyphal tips. Parasites may be obligate or facultative.

Predators:
The oyster mushroom Pleurotus ostreatus is a predatory (Carnivorous) fungus. The fungus paralyzes the nematodes, penetrates through them and absorb their nutritional contents, primarily to fulfill its nitrogen requirement.

The General Characteristics of Fungi

General Characteristics

Following are some of the important characteristics of fungi.

Habitat:

They occupy a wide range of habitats, aquatic, terrestrial and as parasites on plants and animals.

Mode of Life:

They can be parasites, saprotrophs or mutualists.

Size:

They range in size from the unicellular yeasts to the large toad stool.

Nutrition:

They lack chlorophyll, so they are non-photosynthetic. Thus, mode of nutrition is heterotrophic. Digestion takes place outside the body and nutrients are absorbed directly.

Cell Walls:

Cell walls are rigid containing chitin as fibrillar material. It has a high tensile strength, gives shape to the hyphae and prevents osmotic bursting of the cells. Chitin is more resistant to decay than cellulose and lignin present inn the plant cell wall.

The Taxonomic Status of Fungi

Fungi

A heavy lump of dough baked in the oven becomes a light, fluffy loaf of
bread. A bland chunk of milk solids become cheese. In each case members
the fungi kingdom are at work Fungi do not have footstep or leaves. Fungi
of do not have chlorophyll. Fungi (sing, fungus) can live in darkness and also in
light. There are more than 100,000 species of fungi. The study of fungi is
called mycology. The person who studies fungi is called mycologist.

A typical fungus