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cotyledon in formation before the accumulation of the reserves seen at Judas-tree (Cercis siliquastrum)

Comparison of a monocot and dicot sprouting

A cotyledon (Greek: κοτυληδών) is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon becomes the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous (or, "monocots") and placed in the Class Liliopsida. Plants with two embryonic leaves are termed dicotyledonous ("dicots") and placed in the Class Magnoliopsida. Species See text. ... Image File history File links This is a lossless scalable vector image. ... Image File history File links Download high resolution version (896x591, 307 KB)Picture of Cotyledon in formation at Juda-tree (Cercis siliquastrum) of (ID?). Morphology of a true leaf. ... Image File history File links Download high resolution version (896x591, 307 KB)Picture of Cotyledon in formation at Juda-tree (Cercis siliquastrum) of (ID?). Morphology of a true leaf. ... Image File history File linksMetadata Monocot_vs_dicot_crop_Pengo. ... Image File history File linksMetadata Monocot_vs_dicot_crop_Pengo. ... For other uses, see Embryo (disambiguation). ... A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... For other uses, see Plant (disambiguation). ... Not to be confused with Gemination in phonetics. ... Look up foliage in Wiktionary, the free dictionary. ... Classes Magnoliopsida - Dicots Liliopsida - Monocots The flowering plants or angiosperms are the most widespread group of land plants. ... Orders Base Monocots: Acorus Alismatales Asparagales Dioscoreales Liliales Pandanales Family Petrosaviaceae Commelinids: Arecales Commelinales Poales Zingiberales Family Dasypogonaceae Monocotyledons or monocots are a group of flowering plants usually ranked as a class and once called the Monocotyledoneae. ... Orders see text Dicotyledons or dicots are flowering plants whose seed contains two embryonic leaves or cotyledons. ...

The cotyledon of grasses and many other monocotyledons is highly modified leaf 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). Subfamilies There are 7 subfamilies: Subfamily Arundinoideae Subfamily Bambusoideae Subfamily Centothecoideae Subfamily Chloridoideae Subfamily Panicoideae Subfamily Pooideae Subfamily Stipoideae The true grasses are monocotyledonous plants (Class Liliopsida) in the Family Poaceae, also known as Gramineae. ... Schematic image of wheat coleoptile (above) and flag leave (below) Coleoptile is the pointed protective sheath covering the emerging shoot in monocotyledons such as oats and grasses. ... Endosperm is the tissue produced in the seeds of most flowering plants around the time of fertilization. ...

A seedling of Maritime Pine with eight cotyledons

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. Mediterranean Cypress always having just two cotyledons. The highest number reported is for Big-cone Pinyon (Pinus maximartinezii), with 24 (Farjon & Styles 1997). Image File history File links Size of this preview: 413 × 599 pixel Image in higher resolution (562 × 815 pixel, file size: 365 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cotyledon ... Image File history File links Size of this preview: 413 × 599 pixel Image in higher resolution (562 × 815 pixel, file size: 365 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Cotyledon ... Binomial name Pinus pinaster Aiton The Maritime Pine (Pinus pinaster) is a pine native to the western Mediterranean region. ... Divisions Pinophyta (or Coniferophyta) - Conifers Ginkgophyta - Ginkgo Cycadophyta - Cycads Gnetophyta - Gnetum, Ephedra, Welwitschia The gymnosperms (Gymnospermae) are a group of spermatophyte seed-bearing plants with ovules on the edge or blade of an open sporophyll, the sporophylls usually arranged in cone-like structures. ... Hypocotyl is a botanical term for a part of a germinating seedling of a seed plant. ... Binomial name Pinus radiata D.Don Pinus radiata (family Pinaceae) is known in English as Monterey Pine in some parts of the world (mainly in the USA, Canada and the British Isles), and Radiata Pine in others (primarily Australia, New Zealand and Chile). ... Binomial name Pinus jeffreyi Balf. ... Binomial name Cupressus sempervirens L. Cupressus sempervirens, the Mediterranean Cypress, is a species of cypress native to the eastern Mediterranean region, in northeast Libya, southeast Greece (Crete, Rhodes), southern Turkey, Cyprus, western Syria, Lebanon and western Jordan, and also a disjunct population in Iran. ... Binomial name Pinus maximartinezii Rzedowski Big-cone Pinyon (Pinus maximartinezii) is a pine in the pinyon pine group, native to central Mexico. ...

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. A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... The leaf is the primary site of photosynthesis in plants. ...

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 nuts and acorns.
In botany, a seed is described as epigeal when the cotyledons of the germinating seed expand, throw off the seed shell and become photosynthetic above the ground. ... In botany, a seed is described as hypogeal when the cotyledons of the germinating seed remain non-photosynthetic, inside the seed shell, and below ground. ... For other uses, see Nut (disambiguation). ... For other uses, see Acorn (disambiguation). ...

References

• Mirov, N. T. (1967). The Genus Pinus. Ronald Press Company, New York.
• Farjon, A. & Styles, B. T. (1997). Pinus (Pinaceae). Flora Neotropica Monograph 75: 221-224.

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