Sexual Reproduction in Fungi
Union of two nuclei or gametes of opposite sex a gamete is unisexual. i.e. haploid.
The process of sexual reproduction consists of three distinct phases.
Union of two protoplasts brining two haploid nuclei together in the same of common cell.
Actual fusion of two haploid nuclei brought together as a result of plasmogamy , Karyogamy immediately follows plasmogamy.
The nuclear fusion is followed by meiosis ( reducing division) meiosis reduces the number of chromosomes to haploid.
The sex organs in fungi are called as gametanigia, Gametangia from differentiated sex cells gametes or may contain one or more gamete nuclei.
Methods of Sexual Reproduction:
a. Planogamtic Copulation
b. Gametangial Contact
c. Gametangial Copulation
a. Planogametic Copulation:
Fusion of two naked gametes, one or both of which are motile. It is completed in three manners.
1. Isoplanogamtic Copulation:
It involves two motile identical similar gametes but differs in their physiology. E.g. Synchytricum Olpidium.
Isogamous: It male and female are of same shape and size.
2. Anisoplanogametic Copualtion:
It involves union of dissimilar motile gametes of which one is larger than other. E.g. O. Blastocladiales Genus- Allomyces.
Anisogamous: Morphologically dissimilar but distinct in size and shape.
3. Heteroplanogametic Copualtion:
Fusion of non motile female gamete and motile male gamete is known as Heteroplanogametic Copulation.
b. Gametangial Contact:
In this method two gametangia of opposite sex comes in contact and one or more nuclei migrates from male to the female.
The male nuclei enters the female gametangium through a pore developed by the dissolution of gametangial walls at the point of contact while in other species fertilization tube acts as a passage or the male nuclei.
After the passage of nuclei has been accomplished the organisms continues its development in various ways and Antheridium eventually disintegrates. E.g. Oomycetes , Ascomycetes.
c. Gametangial Copulation:
Entire protoplast is transferred into the female gametangia a involes the fusion of two protoplast in a common cell. Sex gametes are indistinguishable or morphological identical. Copualtion occurs either by complete fusion of two protoplast. It is common in class Trichomycetes and zygomycetes.
It involves the formation of small spores or seed like structures or spematia. E.g. Spermatiospores.
Spermatia acts as male gamete which is uninucleate or spore like and carried out by wind, insects to the retentive hypha ( Female gametangium). A pore developed at the plant of contact and the contents of the spermatia passes into receptive hypha which serves as a female organ.
E.g. Pycniospores and Receptive hypha in rusts.
No gametes are involved. Vegetative hypha itself acts as a male and female gamete and bring about sexual reproduction. E. g. Smut Fungi.
Degenerate type of sexuality. It is accomplished through migration of nuclei from one cell to another cell of vegetative hypha, often through mechanism of clamps. The two nuclei remain in pair and divide as such and only fuse prior to the formation of spores. No special sex cells are produced. Clamp connections are formed during nuclear division. E.g. Class- Basidiomycetes.
It is defined as phenomenon of coexistence of genetically commonly met within higher plants and is independent sex. It is brought about by hyphal fusion and anastomosis or bridging or vegetative hyphal or carrying nuclei of different genetically reactions and of common occurance in Fungi Imperfecta, giving rise to new nuclear combination and resulting in the origin of new forms.