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Current Category » Introductory Plant Pathology

Spores in Fungi

The fungi reproduce by spores. Spores is a minute reproductive of Propagative functioning as a seed of fungi. These are produced in three ways.

1. Asexually,
2. Sexually,
3. Vegetatively

Spores:

There are three types of spores:

1) Asexual:

i) Endogenous: a. Motile, e.g. Zoospores, b. Non motile e.g. Aplanospores
ii) Exogenous .E.g. Conidia Oidia
                                               
2) Sexual

i) Zygote
ii) Zygospores
iii) Oospores
iv) Ascospores
v) Basidiospores

3) Vegetative:

Chlamydospores

1) Asexual Spores in Fungi:

Asexual spores form without nuclear fusion or act of breeding. These spores borne of sporophores. They are not usually resistance to unfavourable conditions. They are capable of rapid multiplication. They may be one or many celled borne on specialized hyphae or produced in special structures called as spores fruits.

a. Endogenous:

These spores are formed internally within sac by the division of protoplasm. E.g. Sporangiospores.  

i) Sporangiospores:

Sporangiospores are produced in a sac or sporangium and are hvaline , unicellular. These spores are liberated by breaking the wall of sporangium. When sporangium gives motile spores, it is known as zoosporangium or swarsporangium and the spores as zoospores or swarmspores. These spores are motile by means of flagella.

ii) Aplanospore:

A non motile spore produced in the sporangium is knows as Aplanospore.

b. Exogenous:

These spores are borne externally on sporophores.E. g. Conidia, Oidia.

i) Conidia:

These spores are produced on sepecialized hyphae or stock. i.e. conidiphore. Conidia differ in their size, shape, colour, septation and branching within the same species. Conidia may be uni or multicellular, hyaline or coloured. E.g. Alternaria, Helminthosporium.

ii) Oidia:

These spores are barrel shaped or rectangular in shape and are produced asexually in chains on the stalk called as oidiophore. E.g. Oidia in powdery mildew.

II) Sexual Spores in Fungi:

The sexual spores are formed by the fusion between two gametes of opposite sec. Cell carrying the gamete is called gametangium and gamete is unisexual or haploid.

i) Oospores:

It is the result of union between female gametes i.e. Oogonium and male gametes i.e. Antheridium. Anthridial nuclei passes to Oogonium through fertilization tube. Oogonium is larger than Antheridium and is oval or irregular shaped. The Oospores are thick walled and may be smooth or rough, dark in colour. These spores can resist the adverse conditions.
E.g. Fungi of sub-division Mastigomycotian.
                                                                     
ii) Zygospores:

It is a result of union of two similar or identical gametes designated as +ve and –ve. The resultant spore is thick walled or spiny. The wall consists of two layer. Outer one is known as exosporium and inner layer as endosporium. These spores resist unfavourable conditions and germinate during favourable season. E.g. Fungi of Sub-division Zygomycotina.  
  
iii) Zygote:

It is form by union of to opposite haploid motile gametes. E.g. Lower fungi of the subdivision Mastigomycotian.

iv) Ascospores:

It is a result of union between female gametes. I.e. Ascogonium and male gamete. i.e. Antheridium. Anthridial nuclei passes to Oogonium through trichogyne. Ascospores are produce in a sanction as ascus and are generally eight in number, but it may vary and always in multiple of ‘2’. Ascospores may be single or many celled, hyaline or coloured and having various shapes.
E.g. Fungi of sub-division Ascomycotina.

v) Basidiospores:

These are the sexual spores produced on club shaped structure known as basidium on a short stalk o tube known as sterigmata. They are produced exogenously and usually four in number. In these fungi sex organs are absent, except in rust fungi.
E.g. Fungi of sub-division Basidiomycotina.

III) Vegetative Spores in Fungi:

Chlamydospores:

These spores are formed from hyphal cells of old mycelium enveloped by a thick cell wall, which later on separate from parent hyphae behave as resting spores. They may be formed terminally or intercalary.
E.g. Fusarium spp.

Current Category » Introductory Plant Pathology