Sporophyte


Sporophyte

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The sporophyte produces spores (hence the name), by meiosis. These meiospores develop into a gametophyte. Both the spores and the resulting gametophyte are haploid, meaning they only have one set of homologous chromosomes. The mature gametophyte produces male or female gametes (or both) by mitosis. The fusion of male and female gametes produces a diploid zygote which develops into a new sporophyte. This cycle is known as alternation of generations or alternation of phases.

s into two halves causes complications.

Bryophytes (mosses, liverworts and hornworts) have a dominant gametophyte stage on which the adult sporophyte is dependent on the gametophyte for nutrition. The embryo of the sporophyte develops from the zygote within the female sex organ or archegonium, and in its early development is therefore nurtured by the gametophyte. Because this embryo-nurturing feature of the life cycle is common to all land plants they are known collectively as the Embryophytes.

Most algae have dominant gametophyte generations, but in some species the gametophytes and sporophytes are morphologically similar (isomorphic). An independent sporophyte is the dominant form in all clubmosses, horsetails, ferns, gymnosperms, and angiosperms (flowering plants) that have survived to the present day. Early land plants had sporophytes that produced identical spores (isosporous or homosporous) but the ancestors of the gymnosperms evolved complex heterosporous life cycles in which the spores producing male and female gametophytes were of different sizes, the female megaspores tending to be larger, and fewer in number, than the male microspores.

During the Devonian period several plant groups independently evolved heterospory and subsequently the habit of endospory, in which single megaspores were retained within the sporangia of the parent sporophyte, instead of being freely liberated into the environment as in ancestral exosporous plants. These endosporic megaspores contained within them a miniature multicellular female gametophyte complete with female sex organs or archegonia containing oocytes which were fertilised by free-swimming sperm produced by windborne miniatuarised male gametophytes in the form of pre-pollen. The resulting zygote developed into the next sporophyte generation while still retained within the pre-ovule, the single large female meiospore or megaspore contained in the modified sporangium or nucellus of the parent sporophyte. The evolution of heterospory and endospory were among the earliest steps in the evolution of seeds of the kind produced by gymnosperms and angiosperms today.

References

*P. Kenrick & P.R. Crane (1997) The origin and early evolution of plants on land. "Nature" 389, 33-39.
*T.N. Taylor, H. Kerp and H. Hass (2005) Life history biology of early land plants: Deciphering the gametophyte phase. "Proceedings of the National Academy of Sciences" 102, 5892-5897.
*P.R. Bell & A.R. Helmsley (2000) "Green plants. Their Origin and Diversity." Cambridge University Press ISBN 0 521 64673 1


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  • sporophyte — [ spɔrɔfit ] n. m. • 1897; de spore et phyte ♦ Bot. 1 ♦ Individu producteur de spores d une espèce à reproduction sexuée. 2 ♦ Phase du cycle reproducteur de certains végétaux inférieurs et de tous les spermaphytes et ptéridophytes. ● sporophyte… …   Encyclopédie Universelle

  • sporophyte — [spō′rəfīt΄, spôr′əfīt΄] n. [ SPORO + PHYTE] in certain plants and algae, the spore bearing generation that is diploid and reproduces by spores: the sporophyte generation begins with the fertilized egg and ends with meiosis: distinguished from… …   English World dictionary

  • Sporophyte — Spo ro*phyte (sp[=o] r[ o]*f[imac]t), n. [Spore + Gr. fyto n plant.] (Bot.) In plants exhibiting alternation of generations, the generation which bears asexual spores; opposed to {gametophyte}. It is not clearly differentiated in the life cycle… …   The Collaborative International Dictionary of English

  • sporophyte — sporophyte. См. спорофит. (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.

  • sporophyte — from comb. form of Gk. spora “spore” (see SPORE (Cf. spore)) + phyte (see PHTYO (Cf. phtyo )) …   Etymology dictionary

  • sporophyte — sporophytic /spawr euh fit ik, spohr /, adj. /spawr euh fuyt , spohr /, n. Bot. the form of a plant in the alternation of generations that produces asexual spores. Cf. gametophyte. [1885 90; SPORO + PHYTE] * * * In many plants and algae, the… …   Universalium

  • Sporophyte — Le sporophyte est la génération du cycle de reproduction des plantes qui produit des spores, microspores et macrospores, qui sont disséminées ou non. Cette phase du cycle de développement fait suite à la fécondation et contient donc le double de… …   Wikipédia en Français

  • sporophyte — noun The plant (or the diploid phase in its life cycle) which produces spores by meiosis in order to produce gametophytes. (b) sporophyte with foot reduced, the entire sporophyte enveloped by the calyptra, which is ± stipitate at the base. See… …   Wiktionary

  • sporophyte — sporofitas statusas T sritis augalininkystė apibrėžtis Augalas, kuris išaugina sporas. atitikmenys: angl. sporophyte rus. спорофит ryšiai: sinonimas – nelytinė karta …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • sporophyte — noun Etymology: International Scientific Vocabulary Date: 1886 the diploid individual or generation of a plant exhibiting alternation of generations that produces asexual spores compare gametophyte • sporophytic adjective …   New Collegiate Dictionary


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