INTRODUCTION
Fungi mainly undergo sexual and asexual reproduction, although some fungi reproduction through vegetative method. Their reproduction depends on favorable environmental conditions. Some conditions trigger genetically determined progress, leading to the specialized structures for sexual or asexual reproduction. There is also non-sexual reproduction.
SEXUAL REPRODUCTION
This involves the fusion of two mature gametes. In an artificial group of fungi called fungi imperfecti. It is absent. There are different types of fungi depending upon the type of sexual reproduction. Mates that are genetically different mates are Heterotrophic.
These processes involve the fusion of nuclei, as well as cytoplasm known as kargogamy and plasmogamy and it involves to a diploid nuclei which fuses form a haploid and undergo.
A dikargen cell is present in the intermediate meiosis phase between plasmogamy and kargogamy. There is a decrease in sexuality with the progressive increase in class of fungi.
Sexual reproduction occurs by planogametic copulation gametangial contact and copulation, spermatogamy and somatogamy.
In planogametic copulation gametes are with the flagella. They differentiate and then fuse. This fusion, may be isogamous or heterogamous, which involves similar and dissimilar gametes.
In gametangial contact, male and female sex organs are involved. These are the antheridia and the gametes fuse and form zygosphere while in spermatogamy, the male cell is carried to the female sex organ and in somatogamy the process involves fusing of vegetative hyphae.
SEXUAL REPRODUCTION IN SOME FUNGI
Zygomycates – They could have a single type of nucleus in their mycelium (homothallism) or they can contain two mating types nuclei inside their mycelium (neterothallism).
When homothatlic, they undergo somatic fusion (conjugation) caused by attraction in between the fungi by the secretin induce molecules responsible for the formation of zygospheres, modified hyphael tips, which then grow towards each other.
Ascomycetes – They have no specialized organ of hyphael fusion. Different mating type mycelia merely fuse with each other to form transcient dikargons, mycelia with two mating types nuclei within it. The dikargotic mycelia can differentiate to form varying amounts of sterile mycelium around what is to become the fertile issue of the fruit body.
In yeast, a diploid yeast will undergo meiosis producing, four haploid progeny cells.
Basidiomycetes – They have the most complex structure found in fungi. They rarelu produce asexualspores. They are mostly vegetativemycelium. Compatible mycelium fuse to craete a dikargon.
NON-SEXUAL REPRODUCTION
This method of reproduction is by spores known as sporangio-spores. These spores are found in a sac-like structure called the sporagium. There is a significant different between spores of aquatic fungi and that of a land fungi. The spores of an aquatic fungi is motile, while that of land fungi is non-motile and is mostly dispensed by wind.
Another non-sexual method is by the conidia which is produced by chain and specialized hyphae called conidiosphores and are generally dispersed by wind.
ASEXUAL REPRODUCTION
This is the most common method of reproduction in fungi. In its simplest form, asexual reproduction is by budding on binary fusion.
Budding is the development of a ning of chitin around the point where the bud is about to appear.
Fragmentation – Many fungi can reproduce by fragmentation. Any mycelium that is fragmented or disrupted, provided that the fragment contains the equivalent of the peripheral growth zone, can grow into a new colony.
Sporalation – This is by the most important type of asexual reproduction and asexual reproduction is extremely important to fungi, it is responsible for the reproduction of large numbers of spores through-out the year. The asexual spores are formed on a phase of fungal life cycle termed in some text as mitosphoric or anamorphic phase. There can be more than one mitosphoric state for each species of fungus, and in some cases the mitosporic states of very different species can look very similar.
The onset of asexual reproduction is controlled by many different things. Some are environmental-like nutrient levels, CO2 levels, light levels. Others can have internal lime clocks and sporulate anyway in a present part of the fungal life cycle designed to spread and maximize colonization during one season.
ASEXUAL REPRODUCTION IN SOME FUNGI
Chutridiomycetes – Chytrides are quite distinct from other fungi, as they have extremely simple thelli and motile zoospores.
Species within this group are very simple in structure and may only consist of a single cell, perhaps with rhizoids to anchor it on a substrate.
Asexual reproduction in the chytids is by the production of motile zoospores with a single posterior flagellum in the sporangia.
Zygomycetes – Zygomycetes fungal mycellium is coenocytic. At the onset of sporulation, large amount of aerial hyphae are produced. The tips of these aerial hyphae are fill with cytoplasmic contents and the nuclei undergo repeated mitosis. Around each of the nuclei cytoplasm and organelles connect and by the formation of coprious vesicles from golgi, each nucleus becomes isolated from the next by a plasma membrane within the spaces created by this cytoplasmic cleavage; spore walls begin to form, again by the fusion of Golgi vessicles containing cell wall monomers and enzymes with the spores membrane. A sporangium forms as these events occur so there is considerable water uptake by the forming sporangium, and as the collumella forms, the structure comes under considerable tugor pressure. A large sporangia can contain up to 100, 000 spores.
Ascomycetes/Deuteromycetes – The process of spore formation in most members of the higher fungal groups is based largely on the formation of aenal mycelium and the differentiation of the hyphael tip. However, unlike the process seen in zygomycetes, the process here involves much more like the budding seen in yeast. This is termed blastic process, which involves the blowing out of the hyphael tip wall. The blastic process can involves all wall layers or there can be a new cell wall synthesised which is centruded from within the old wall. This reproduction could result in a bottle-shaped fungi, other species of ascomycates and deutromycetes form their structures within plant tissue either as parasites or saprophytes. This fungi has evolved a more complex asexual sporing structure, probably influence by cultural conditions of the plant tissue. This structure is called sporodichium.