Peziza: Occurrence, Structure, Reproduction

Peziza is a saprophytic fungus of the class Discomycetes. It is often coprophilous in habit, growing on dung.

Peziza is commonly known as cup fungus, due to its cup-shaped fruit body.

Occurrence of Peziza

Peziza is a genus in the family Pezizaceae. It is represented by about 100 species and occurs all over the world.

Most of the species are saprophytes and prefer to grow on dung, decaying wood, or soil rich in humus during the rainy season. Some species are found on burnt forest wood.

Peziza vesiculosa is the most commonly occurring species. Although it is considered poisonous.

  • Some Peziza species are: Peziza domiciliana, P. vesiculosa, P. repanda, P. pustulata, P. catinum, P. ampliata, P. cerea, P. fimeti, etc.
Peziza: Occurrence, Structure, Reproduction

Vegetative Structure of Peziza

The vegetative plant body of Peziza is the mycelium. The mycelium is usually perennial and consists of well-developed, branched,septate hyphae.

The hyphae are not visible as they ramify within the substratum, forming a dense, complex system. This system helps in the absorption of nutrition from the substratum.

Apothecium of Peziza
Figure: Only Fruit bodies of Peziza are visible, as the mycelium develops inside the substratum

The hyphal cells are short and uninucleate.

Read also- Aspergillus: Occurrence, Structure, Reproduction

Reproduction in Peziza

Peziza reproduces both asexually and sexually.

Asexual Reproduction

Asexual reproduction is rare in Peziza. In some species, such as P. vesiculosa and P. repanda, it takes place through the formation of conidia and chlamydospores.

The conidia are produced exogenously at the tips of the erect conidiospores. Each of the conidia germinates to develop new mycelium.

The chlamydospores are intercalary, thick-walled resting cells. They are produced either singly or in series within the cells of the mycelium. Under favourable conditions, each chlamydospore germinates into new mycelium.

Sexual Reproduction

In Peziza, sex organs are completely absent. Sexual reproduction is extremely simple, and it takes place by somatic copulation between certain vegetative cells of adjacent hyphae or by autogamous pairing (i.e., fusion of two adjacent vegetative cells).

The hyphae get tangled in the adult mycelium. Certain vegetative cells in the centre of the tangle have been seen to possess nuclei that become associated in pairs, called dikaryons.

The cells with dikaryons give rise to the ascogenous hyphae. The ascogenous hyphae become septate and branched. The cells are binucleate.

The terminal cell of each ascogenous hypha functions as an ascus mother cell. The formation of a crozier or hook, in the development of ascus has not been reported in P. vesiculosa. However, in P. catinum, crozier formation can be seen. The two nuclei of the ascus mother cell fuse with each other, forming the synkaryon (a diploid nucleus).

The diploid nucleus divides by meiosis and then mitosis to form eight haploid nuclei. Each nucleus becomes organised into an ascospore in the mature ascus.

The erect asci lie side by side, parallel to each other, lining the cavity of the cup-shaped apothecium.

Apothecium

The apothecium, i.e., the fruit body of Peziza, is a fleshy, sessile or sub-sessile, cup-shaped structure without any hairs. It is large in size, varying from 2 cm to 40 cm in diameter.

The apothecium is usually brightly coloured. It is pale fawn (a light yellow-tan colour) in P. vesiculosa and orange in P. aurantia.

The margin of the apothecium cup is formed by the hymenium, a layer of elongated cells standing at a right angle to the surface like a palisade. It contains asci intermingled with sterile hyphae, the paraphyses.

Below the hymenium is a thin or fairly thick layer known as the hypothecium. The hypothecium is composed of many branched hyphae running parallel to the surface of the hymenium.

The outer layer of the hypothecium, i.e., the basal portion of the apothecium cup, is called the excipulum.

Ascus

The mature ascus is an elongated cylindrical structure with an operculum, or lid, at the apex. It contains eight ascospores arranged obliquely in a row.

Ascus of Peziza
Figure: Asci with ascospores

The ascospores are haploid, unicellular, smooth-walled, hyaline, and ellipsoidal in shape. They are liberated in large numbers through the operculum of the ascus.

Under favourable conditions, each ascospore germinates into a germ tube, from which new mycelium develops.

Taxonomic Position of Peziza

Division:Eumycota
Sub-Division:Ascomycotina
Class:Discomycetes
Order:Pezizales
Sub-Order:Pezizineae
Family:Pezizaceae
Genus:Peziza

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