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Spores, Sexual and Asexual Questions

Question 1

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Answer 1

Essentially all cells, once separated from the mycelium, have the potential to initiate a new thallus. Therefore, spores are non specialised cells and cells which function to disperse the fungus. Arthrospores are fragments of hyphae. Conidia, sporangiospores and zoospores are specialised cells which reproduce the fungi asexually. The sexual spores are basidiospores (Basidiomycota), ascospores (Ascomycota), zygospores (Zygomycota) and chytridiospores (Chytridiomycota).

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Question 2

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Answer 2

Arthrospores and conidiospores are found in the septate fungi. They differ in that arthrospores are formed from the fragmentation of existing hyphae, and are thus surrounded by pre-existing wall material. Conidiospores develop within freshly formed walls.

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Question 3

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Answer 3

Sporangiospores are formed following the internal division of cytoplasm within a sporangium, and they are found in the Chytridiomycota and Zygomycota. Conidiospores are formed following the extrusion of cytoplasm surrounded by new wall material. Conidia are found in the Ascomycota and Basidiomycota.

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Question 4

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Answer 4

Most conidia are formed on free conidiophores, either singly or in aggregations of various types. Synnemata are aggregations which rise from the substrate in a column. The spores are usually released from the surface, especially the tip. In a few fungi, the conidiogenous hyphae aggregate in a mass releasing the spores from a cushion-shaped sporodochium. Conidia may be formed within enclosures and the spores released when the plant tissue erupts (acervulus). They may be formed within flask-shaped pycnidia with the fungus providing the outer layer enclosing the conidiophores. Spores are released from pycnidia either through a pore or ostiole, or when the surface ruptures.

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Question 5

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Answer 5

The development of conidia has been classified into two basic types, blastic and thallic, which can be organised into a total of eight groups. Blastic acropetal and blastic synchronous; blastic sympodial; blastic phialidic; blastic annelidic; blastic retrogressive; basauxic; thallic arthric; and thallic solitary.

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Question 6

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Answer 6

Hyphae of opposite mating type fuse and at the junction, a separate sporangium forms. The zygospore forms within the zygosporangium.

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Question 7

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Answer 7

In the hymenium, following fusion of hyphae of opposite mating type, the dikaryotic tissue passes into karyogamy immediately followed by meiosis. The terminal cell in which the four products of meiosis are found then passes into a mitotic division, and walls form around the ascospores.

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Question 8

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Answer 8

Meiosis takes place inside the basidium. The resultant nuclei then pass into sterigma, and are exuded into new cells formed on the sterigma.

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