Sporogenesis is the production of
spores in biology. The term is also used to refer to the process of reproductionvia spores. Reproductive spores are formed in many eukaryotic organisms, such as plants, algaeand fungi, during their normal reproductive life cycle. Dormant spores are formed, for example by certain fungi and algae, primarily in response to unfavorable growing conditions. Most eukaryotic spores are haploidand form through cell division, though some types are diploidor dikaryons and form through cell fusion.
Reproduction via spores
Reproductive spores are generally the result of cell division, most commonly
meiosis(e.g. in plant sporophytes). Sporic meiosis is needed to complete the sexual life cycle of the organisms using it.
In some cases, sporogenesis occurs via
mitosis(e.g. in some fungi and algae). Mitotic sporogenesis is a form of asexual reproduction. Examples are the conidial fungi " Aspergillus" and " Penicillium", for which mitospore formation appears to be the primary mode of reproduction. Other fungi, such as ascomycetes, utilize both mitotic and meiotic spores. The red alga " Polysiphonia" alternates between mitotic and meiotic sporogenesis and both processes are required to complete its complex reproductive life cycle.
In the case of dormant spores in eukaryotes, sporogenesis often occurs as a result of
fertilizationor karyogamyforming a diploid spore equivalent to a zygote. Therefore, zygospores are the result of sexual reproduction.
Reproduction via spores involves the spreading of the spores by water or air. Algae and some fungi (
chytrids) often use motile zoospores that can swim to new locations before developing into sessile organisms. Airborne spores are obvious in fungi, for example when they are released from puffballs. Other fungi have more active spore dispersal mechanisms. For example, the fungus " Pilobolus" can shoot its sporangia towards light. Plant spores designed for dispersal are also referred to as diaspores. Plant spores are most obvious in the reproduction of ferns and mosses. However, they also exist in flowering plants where they develop hidden inside the flower. For example, the pollen grains of flowering plants develop out of microspores produced in the anthers.
Reproductive spores grow into multicellular haploid individuals or
sporelings. In heterosporousorganisms, two types of spores exist: microspores give rise to males and megaspores to females. In homosporousorganisms, all spores look alike and grow into individuals carrying reproductive parts of both genders.
Formation of reproductive spores
Sporogenesis occurs in reproductive structures termed sporangia. The process involves sporogenous cells (sporocytes, also called spore mother cells) undergoing cell division to give rise to spores.
In meiotic sporogenesis, a diploid spore mother cell within the sporangium undergoes meiosis, producing a tetrad of haploid spores. In organisms that are
heterosporous, two types of spores occur: Microsporangia produce malemicrospores, and megasporangia produce femalemegaspores. In megasporogenesis, often three of the four spores degenerate after meiosis, whereas in microsporogenesis all four microspores survive.
gymnosperms, such as conifers, microspores are produced through meiosis from microsporocytes in microstrobili or male cones. In flowering plants, microspores are produced in the anthers of flowers. Each anther contains four pollen sacs, which contain the microsporocytes. After meiosis, each microspore undergoes mitotic cell division, giving rise to multicellular pollen grains (six nuclei in gymnosperms, three nuclei in flowering plants).
Megasporogenesis occurs in megastrobili in conifers (for example a pine cone) and inside the
ovulein the flowers of flowering plants. A megasporocyte inside a megasporangium or ovule undergoes meiosis, producing four megaspores. Only one is a functional megaspore whereas the others stay dysfunctional or degenerate. The megaspore undergoes several mitotic divisions to develop into a female gametophyte(for example the seven-cell/eight-nuclei embryo sacin flowering plants).
Some fungi and algae produce
mitospores through mitotic cell division within a sporangium. In fungi, such mitospores are referred to as conidia.
Formation of dormant spores
Some algae, fungi and bacteria form
resting spores designed to survive unfavorable conditions. Typically, changes in the environment from favorable to unfavorable growing conditions will trigger a switch from asexual reproductionto sexual reproductionin these organisms. The resulting spores are protected through the formation of a thick cell walland can withstand harsh conditions such as drought or extreme temperatures. Examples are chlamydospores, teliospores, zygospores, and myxospores.
Chlamydospore and teliospore formation
Chlamydospores are generally multicellular, asexual structures. Teliospores are a form of chlamydospore produced through the fusion of cells or hyphaewhere the nuclei of the fused cells stay separate. These nuclei undergo karyogamyand meiosis upon germination of the spore.
Zygospore, oospore and auxospore formation
Zygospores are formed in certain fungi ( zygomycota, for example " Rhizopus") and some algae (for example " Chlamydomonas"). The zygospore forms through the isogamic fusion of two cells (motile single cells in "Chlamydomonas") or sexual conjugationbetween two hyphae (in zygomycota). Plasmogamyis followed by karyogamy, therefore zygospores are diploid ( zygotes). They will undergo zygotic meiosis upon germinating.
oomycetes, the zygote forms through the fertilization of an egg cell with a sperm nucleus and enters a resting stage as a diploid, thick-walled oospore. The germinating oospore undergoes mitosis and gives rise to diploid hyphae which reproduce asexually via mitotic zoospores as long as conditions are favorable.
diatoms, fertilization gives rise to a zygote termed auxospore. Besides sexual reproduction and as a resting stage, the function of an auxospore is the restoration of the original cell size, as diatoms get progressively smaller during mitotic cell division. Auxospores divide by mitosis.
The term sporogenesis can also refer to
endosporeformation in bacteria, which allows the cells to survive unfavorable conditions. Endospores are not reproductive structures and their formation does not require cell fusion or division. Instead, they form through the production of an encapsulating spore coat within the spore-forming cell.
*S.S. Mader (2007): "Biology", 9th edition, McGraw Hill Companies, New York, ISBN 978-0-07-246463-4
*P.H. Raven, R.F. Evert, S.E. Eichhorn (2005): "Biology of Plants", 7th Edition, W.H. Freeman and Company Publishers, New York, ISBN 0-7167-1007-2
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Look at other dictionaries:
Sporogenesis — Spo ro*gen e*sis ( j[e^]n [ e]*s[i^]s), n. [Spore + genesis.] (Biol.) Reproduction by spores. [1913 Webster] … The Collaborative International Dictionary of English
sporogenesis — sporogenesis. См. спорогенез. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) … Молекулярная биология и генетика. Толковый словарь.
sporogenesis — [spôr΄ə jen′ə sis] n. [ModL: see SPORO & GENESIS] Biol. 1. reproduction by means of spores 2. the formation of spores sporogenic adj. sporogenous [spô räj′ə nəs] adj … English World dictionary
sporogenesis — sporogenezė statusas T sritis augalininkystė apibrėžtis Sporų (mikrosporų, makrosporų) susidarymo vyksmas. atitikmenys: angl. sporogenesis rus. спорогенез; спорообразование … Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas
sporogenesis — noun Etymology: New Latin Date: circa 1890 1. reproduction by spores 2. spore formation • sporogenous also sporogenic adjective … New Collegiate Dictionary
sporogenesis — (spor o jen ē sis) See sporulation … Dictionary of microbiology
sporogenesis — /spawr euh jen euh sis, spohr /, n. Biol. 1. the production of spores; sporogony. 2. reproduction by means of spores. [1885 90; SPORO + GENESIS] * * * … Universalium
sporogenesis — noun The process by which spores are produced. See Also: sporangium, spore, sporophyte, sporophytic … Wiktionary
sporogenesis — SYN: sporogony. [sporo + G. genesis, production] * * * spo·ro·gen·e·sis .spōr ə jen ə səs, .spȯr n, pl e·ses .sēz 1) reproduction by spores 2) spore formation * * * spo·ro·gen·e·sis (spor″o jenґə sis) [sporo + genesis] sporulation… … Medical dictionary
sporogenesis — reproduction by means of spores Causation and Formation … Phrontistery dictionary