Conidium
A conidium (
Asexual reproduction in
The terms microconidia and macroconidia are sometimes used.[4]
Conidiogenesis
There are two main types of conidium development:[5]
- Blastic conidiogenesis, where the spore is already evident before it separates from the conidiogenic hypha which is giving rise to it, and
- Thallic conidiogenesis, where first a cross-wall appears and thus the created cell develops into a spore.
Conidia germination
A conidium may form
Structures for release of conidia
Conidiogenesis is an important mechanism of spread of plant pathogens. In some cases, specialized macroscopic fruiting structures perhaps 1 mm or so in diameter containing masses of conidia are formed under the skin of the host plant and then erupt through the surface, allowing the spores to be distributed by wind and rain. One of these structures is called a conidioma (plural: conidiomata).[8][9]
Two important types of conidiomata, distinguished by their form, are:
- pycnidia (singular: pycnidium), which are flask-shaped, and
- acervuli (singular: acervulus), which have a simpler cushion-like form.
Pycnidial conidiomata or pycnidia form in the fungal tissue itself, and are shaped like a bulging vase. The conidia are released through a small opening at the apex, the ostiole.
Acervular conidiomata, or acervuli, are cushion-like structures that form within the tissues of a host organism:
- subcuticular, lying under the outer layer of the plant (the cuticle),
- intraepidermal, inside the outer cell layer (the epidermis),
- subepidermal, under the epidermis, or deeper inside the host.
Mostly they develop a flat layer of relatively short conidiophores which then produce masses of spores. The increasing pressure leads to the splitting of the epidermis and cuticle and allows release of the conidia from the tissue.
Health issues
Conidia are always present in the air, but levels fluctuate from day to day and with the seasons. An average person inhales at least 40 conidia per hour.[10] Exposure to conidia from certain species, such as those of Cryptostroma corticale, is known to cause hypersensitivity pneumonitis, an occupational hazard for forest workers and paper mill employees.[11][12]
Conidia are often the method by which some normally harmless but heat-tolerating (thermotolerant), common fungi establish infection in certain types of severely
See also
References
- ^ Jansonius, D.C., Gregor, Me., 1996. Palynology: principles and applications. American association of stratigraphic palynologists foundation.[page needed]
- PMID 11377860.
- CollinsDictionary.com. HarperCollins.
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- ^ James J. Worrall (2023). "Fungi". Forest Pathology. Retrieved 20 February 2023.
- .
- PMID 28883073.
- ^ Worrall, James J. (2023). "Sooty-Bark Disease of Maple". Forest Pathology. Retrieved 18 February 2023.
- PMID 33478566. 2.
- S2CID 3157271.
External links
- . . 1914.