Phycomycetes

We usually see bread mould growing on bread when kept in open for 4-5 days which is an example of fungi.

Fungal growth is also seen in decaying vegetables and fruits, pickles and leather goods.

Toadstool growing in rainy season or mushroom that we eat are examples of fungi too.

Both bread mould and mushroom differ from each other in many other aspects because they both belong to different classes of fungi.

Rhizopus and mucor are fungi found growing on bread or other dead decaying matter and they belong to phycomycetes class of fungi.

Let us see what makes phycomycetes different from other classes of fungi.

Most important characteristics of phycomycetes is aseptate coenocytic hyphae.

They are found in aquatic habitat, as parasite on plants or on decaying woods.

Asexual reproduction takes place by motile zoospores or non-motile aplanospores.

Sexual reproduction produces zygospore by fusion of either similar gametes (isogamy) or dissimilar gametes (anisogamy or oogamy).

Based on their mode of sexual reproduction, phycomycetes is further divided into two groups : oomycetes and zygomycetes.

Let us now see the oomycetes mode of sexual reproduction in Phycomycetes

In oomycetes, motile male gamete is transferred from antheridium (male sex organ) to ooganium (female sex organ) by gametangial contact.

After which fertilisation takes place and results in formation of thick-walled zygote called as oospore.

They reproduce asexually too which involves formation of sporangia.

Sporangia produces biflagellated zoospores (in aquatic forms) and nonflagellated conidia or aplanospores (in terrestrial forms).

Members of this group of fungi mostly live as parasite on plants and cause various plant diseases.

The disease late blight of potato is caused by phytophthora infestans and was responsible for Irish famine.

White rust of crucifers is caused by Albugo candida.

Downy mildew in crop plants, pea, mustard, spinach, onion etc. Is caused by Peronospora parasitica, Plasmospora and Sclerospora.

Pythium debaryanum causes damping off that results in killing of seedlings of tomato, chillies, mustard, tobacco etc.

Let us see zygomycetes mode of sexual reproduction in Phycomycetes.

Zygomycetes are also called as conjugating fungi because they reproduce sexually by copulation of gametangia and by conjugation.

Gametes are multinucleated (called as coenogametes) and fuse together to form resting diploid zygospore.

Zyogospore on germination produces a germ sporangiophore which bears terminal germ sporangium.

Meiospores called as germ spores are produced in the germ sporangium after meiosis.

Conidia, sporangiospores and aplanospores are asexual spores produced by the members of zygomycetes.

Mucor and Rhizopus are key members of zygomycetes.

Their body is made up of thread like, white, delicate mass of hyphae which is septate and coenocytic.

Their hyphae forms a network known as mycelium contains three kinds of hyphae: stolons, rhizoidal hyphae and sporangiophores.

These fungi grow on foodstuffs, leather, clothes, fruits and vegetables and spoils them.

Rhizopus nigricans causes soft rot of fruits and vegetables while many other species damage germination of maize seeds.

They're not always harmful, they also helps in maintaining soil fertility by decaying complex dead organic matter.

They are also used for manufacturer of lactic acid, citric acid, fumaric acid and production of alcohol.

Revision

Phycomycetes is a class of fungi characterised by aseptate coenocytic hyphae.

They are further divided into oomycetes and zygomycetes based on their method of sexual reproduction.

Oomycetes reproduce sexually by gametangial contact resulting in formation of oospore.

Examples of oomycetes are Phytophthora, Albugo, Pythium, Sclerospora, Plasmopara, Peronospora and they cause various diseases in plants.

Zygomycetes is characterised by formation of resting zygospore on fusion of gametes.

Mucor, Rhizopus, Pilobolus, Abscidia are examples of zygomycetes.

The End