Acotyledon is used to refer to seed plants or spermatophytes that lack cotyledons, such as orchids and dodder. Orchid seeds are tiny with underdeveloped embryos. They depend on mycorrhizal fungi for their early nutrition so are myco-heterotrophs at that stage.

Contrary to many websites, acotyledon is not used to refer to "all nonflowering plants." Gymnosperms are nonflowering plants that have cotyledons or seed leaves. Seedless, nonflowering plants, such as bryophytes, ferns and fern allies, are not referred to as acotyledons because they lack seeds altogether.

Flowering plants or angiosperms are divided into two large groups. Monocotyledons or monocots have one seed lobe, which is often modified to absorb stored nutrients from the seed so never emerges from the seed or becomes photosynthetic. Dicotyledons or dicots have two cotyledons and often germinate to produce two leaf-like cotyledons. Conifers and other gymnosperms lack flowers but may have two or more cotyledons in the seedling.

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  • acotylédon — ⇒ACOTYLÉDON, ONE, adj. et subst. BOT., vx, emploi adj. 1. ,,Privé de cotylédons. (NYSTEN 1814 20). 2. ,,Dont les cotylédons ne sont pas visibles, dans l expr. plantes acotylédones ou inembryonnées. (NYSTEN 1814 20) : • 1. Les champignons, les… …   Encyclopédie Universelle

  • Acotyledon — A*cot y*le don (#; 277), n. [Gr. a priv. + ? anything cup shaped. See {Cotyledon}.] (Bot.) A plant which has no cotyledons, as the dodder and all flowerless plants. [1913 Webster] …   The Collaborative International Dictionary of English

  • acotyledon — [ā΄kät΄ə lēd′ n] n. any plant lacking seed leaves (cotyledons), as dodder …   English World dictionary

  • acotyledon — acotyledonous /ay kot l eed n euhs, ay kot /, adj. /ay kot l eed n, ay kot /, n. a plant without cotyledons, therefore one belonging to a group lower than the seed plants. [1810 20; A 6 + COTYLEDON] * * * …   Universalium

  • acotyledon — noun /ˈeɪ.kɔt.l̩.iːdˌn̩/ A plant that has no cotyledons, as the dodder and all flowerless plants …   Wiktionary

  • acotyledon — [əˌkɒtɪ li:d(ə)n] noun a plant that has no distinct seed leaves. Derivatives acotyledonous adjective Origin C18: from mod. L. plural acotyledones (see a 1, cotyledon) …   English new terms dictionary

  • acotyledon — acot·y·le·don …   English syllables

  • acotyledon — /əkɒtəˈlidən/ (say uhkotuh leeduhn) noun a plant without cotyledons. {a 6 + cotyledon} –acotyledonous /əkɒtəˈlidənəs/ (say uhkotuh leeduhnuhs), adjective …  

  • acotyledon —   n. plant without differentiated seed lobes.    ♦ acotyledonous, a …   Dictionary of difficult words

  • acotyledon — n. a plant with no distinct seed leaves. Derivatives: acotyledonous adj. Etymology: mod.L acotyledones pl. (as A (1), COTYLEDON) …   Useful english dictionary

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