https://www.gardenology.org/w/api.php?action=feedcontributions&feedformat=atom&user=65.19.178.32 2026-04-10T15:45:04Z User contributions MediaWiki 1.43.0 https://www.gardenology.org/w/index.php?title=Cotyledon&diff=8788 2007-09-27T00:46:06Z

<p>65.19.178.32: </p> <hr /> <div>letoacpa<br /> relbochitr<br /> [[Image:Seedling_cotyledons_small.jpg|thumb|right|This [[seedling]] germinated producing two plain-looking cotyledons later followed by two normal-looking leaves that are small copies of the adult leaves.]]<br /> [[Image:Cotyledon-Cercis_siliquastrum.jpg|thumb|right|cotyledon in formation before the accumulation of the reserves seen at Judas-tree (''Cercis siliquastrum'')]]<br /> [[Image:Monocot_vs_dicot_crop_Pengo.jpg|thumb|Comparison of a monocot and dicot sprouting]]<br /> <br /> A '''cotyledon''' ([[Greek language|Greek]]: ''κοτυληδών'') is a significant part of the [[embryo]] within the [[seed]] of a [[plant]]. Upon [[germination]], the cotyledon usually becomes the embryonic first [[leaf|leaves]] of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the [[flowering plant]]s (angiosperms). Species with one cotyledon are called [[monocotyledonous]] (or, &quot;monocots&quot;) and placed in the Class Liliopsida. Plants with two embryonic leaves are termed [[dicotyledonous]] (&quot;dicots&quot;) and placed in the Class Magnoliopsida.<br /> <br /> The cotyledon of [[Poaceae|grasses]] and many other monocotyledons is highly modified and composed of a ''scutellum'' and a ''[[coleoptile]]''. The scutellum is a tissue within the seed that is specialized to absorb stored food from the adjacent [[endosperm]]. The coleoptile is a protective cap that covers the ''plumule'' (precursor to the stem and leaves of the plant).<br /> <br /> [[Image:Seekiefer (Pinus pinaster) 14d 1.jpg|left|thumb|A seedling of [[Maritime Pine]] with eight cotyledons]]<br /> [[Gymnosperm]] seedlings also have cotyledons, and these are often variable in number (multicotyledonous), with from 2 to 24 cotyledons forming a whorl at the top of the [[hypocotyl]] (the embryonic stem) surrounding the plumule. Within each species, there is often still some variation in cotyledon numbers, e.g. [[Monterey Pine]] (''Pinus radiata'') seedlings have 5–9, and [[Jeffrey Pine]] (''Pinus jeffreyi'') 7–13 (Mirov 1967), but other species are more fixed, with e.g. [[Cupressus sempervirens|Mediterranean Cypress]] always having just two cotyledons. The highest number reported is for [[Big-cone Pinyon]] (''Pinus maximartinezii''), with 24 (Farjon &amp; Styles 1997).<br /> <br /> The cotyledons may be ephemeral, lasting only days after emergence, or persistent, enduring a year or more on the plant. The cotyledons contain (or in the case of gymnosperms and monocotyledons, have access to) the stored food reserves of the [[seed]]. As these reserves are used up, the cotyledons may turn green and begin [[photosynthesis]], or may wither as the first true leaves take over food production for the seedling. <br /> <br /> Cotyledons may be either [[epigeal]], expanding on the germination of the seed, throwing off the seed shell and become photosynthetic above the ground; or [[hypogeal]], not expanding, remaining below ground and not becoming photosynthetic. The latter is typically the case where the cotyledons act as a storage organ, as in many [[nut (fruit)|nuts]] and [[acorn]]s. &lt;br clear = left&gt;<br /> <br /> ==References==<br /> *Mirov, N. T. (1967). ''The Genus Pinus''. Ronald Press Company, New York.<br /> *Farjon, A. &amp; Styles, B. T. (1997). Pinus (Pinaceae). ''Flora Neotropica Monograph'' 75: 221-224.<br /> <br /> [[Category:Botany]]</div>

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