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Cotyledon

February 16, 2024

For other uses, see Cotyledon (disambiguation).
Not to be confused with Cotyledion or cotylenol.

A cotyledon (/ˌkɒtɪˈliːdən/; lit. 'seed leaf'; from Latin cotyledon;[1] from κοτυληδών (kotulēdṓn), gen. κοτυληδόνος (kotulēdónos), from κοτύλη (kotýlē) 'cup, bowl') is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed."[2] The number of cotyledons present is one characteristic used by botanists to classify the flowering plants (angiosperms). Species with one cotyledon are called monocotyledonous ("monocots"). Plants with two embryonic leaves are termed dicotyledonous ("dicots").

Cotyledon from a Judas-tree (Cercis siliquastrum, a dicot) seedling
Comparison of a monocot and dicot sprouting. The visible part of the monocot plant (left) is actually the first true leaf produced from the meristem; the cotyledon itself remains within the seed
Schematic of epigeal vs hypogeal germination
Peanut seeds split in half showing the embryos with cotyledons and primordial root
Two-week-old Douglas fir (a conifer) with seven cotyledons
Mimosa pudica (a dicot) seedling with two cotyledons and the first "true" leaf with six leaflets

In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct. Cotyledons are formed during embryogenesis, along with the root and shoot meristems, and are therefore present in the seed prior to germination. True leaves, however, are formed post-embryonically (i.e. after germination) from the shoot apical meristem, which is responsible for generating subsequent aerial portions of the plant.

The cotyledon of grasses and many other monocotyledons is a 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).

Gymnosperm seedlings also have cotyledons. Gnetophytes, cycads, and ginkgos all have 2, whereas in conifers they are often variable in number (multicotyledonous), with 2–24 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).

Cotyledons may be ephemeral, lasting only days after emergence, or persistent, enduring at least a year 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.[3]

Epigeal versus hypogeal development edit

Main articles: Epigeal germination and Hypogeal germination

Cotyledons may be either epigeal, expanding on the germination of the seed, throwing off the seed shell, rising above the ground, and perhaps becoming photosynthetic; 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.[citation needed]

Hypogeal plants have (on average) significantly larger seeds than epigeal ones. They are also capable of surviving if the seedling is clipped off, as meristem buds remain underground (with epigeal plants, the meristem is clipped off if the seedling is grazed). The tradeoff is whether the plant should produce a large number of small seeds, or a smaller number of seeds which are more likely to survive.[4][5]

The ultimate development of the epigeal habit is represented by a few plants, mostly in the family Gesneriaceae in which the cotyledon persists for a lifetime. Such a plant is Streptocarpus wendlandii of South Africa in which one cotyledon grows to be up to 75 centimeters (2.5 feet) in length and up to 61 cm (two feet) in width (the largest cotyledon of any dicot,[6] and exceeded only by Lodoicea). Adventitious flower clusters form along the midrib of the cotyledon.[7] The second cotyledon is much smaller and ephemeral.[citation needed]

Related plants may show a mixture of hypogeal and epigeal development, even within the same plant family. Groups which contain both hypogeal and epigeal species include, for example, the Southern Hemisphere conifer family Araucariaceae,[8] the pea family, Fabaceae,[4] and the genus Lilium (see Lily seed germination types). The frequently garden grown common bean, Phaseolus vulgaris, is epigeal, while the closely related runner bean, Phaseolus coccineus, is hypogeal.[citation needed]

History edit

The term cotyledon was coined by Marcello Malpighi (1628–1694).[a] John Ray was the first botanist to recognize that some plants have two and others only one, and eventually the first to recognize the immense importance of this fact to systematics, in Methodus plantarum (1682).[3][11]

Theophrastus (3rd or 4th century BC) and Albertus Magnus (13th century) may also have recognized the distinction between the dicotyledons and monocotyledons.[12][11]

Notes edit

  1. ^ The Oxford English Dictionary attributes it Linnaeus (1707–1778) "1751 Linnaeus Philos. Bot. 54. Cotyledon, corpus laterale seminis, bibulum, caducum" [9] and 89, [10] by analogy with a similar structure of the same name in the placenta.[2]

References edit

  1. ^ Short & George 2013, p. 15, [1].
  2. ^ a b OED.
  3. ^ a b Vines, Sydney Howard (1913), "Robert Morison 1620—1683 and John Ray 1627—1705", in Oliver, Francis Wall (ed.), Makers of British botany, Cambridge University Press, pp. 8–43
  4. ^ a b Charles R. Tischler; Justin D. Derner; H. Wayne Polley; Hyrum B. Johnson (2007). Response of Seedlings of Two Hypogeal Brush Species to CO2 Enrichment. Proceedings: Shrubland dynamics -- fire and water; 2004 August 10–12; Lubbock, TX. Proceedings RMRS-P-47. In: Sosebee, Ronald E.; Wester, David B.; Britton, Carlton M.; Mcarthur, e. Durant; Kitchen, Stanley G., Comps. Proceedings: Shrubland Dynamics -- Fire and Water; 2004 August 10–12; Lubbock, Tx. Proceedings RMRS-P-47. Fort Collins, Co: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. P. 104-106. Vol. 047. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. pp. 104–106.
  5. ^ Baraloto, C.; Forget, P.-M. (2007), "Seed size, seedling morphology, and response to deep shade and damage in neotropical rain forest trees", American Journal of Botany, 94 (6): 901–11, doi:10.3732/ajb.94.6.901, PMID 21636459, S2CID 24272337
  6. ^ Nishii, Kanae; Kuwabara, Asuka; Nagata, Toshiyuki (2004). "Characterization of Anisocotylous Leaf Formation in Streptocarpus Wendlandii (Gesneriaceae): Significance of Plant Growth Regulators". Annals of Botany. 94 (3): 457–67. doi:10.1093/aob/mch160. JSTOR 42759229. PMC 4242185. PMID 15286012. Retrieved 13 December 2022.
  7. ^ Perry, Frances and Leslie Greenwood (1972). Flowers of the World. London: Hamlyn Publishing Group. p. 47.
  8. ^ Hiroaki Setoguchi; Takeshi Asakawa Osawa; Jean-Christophe Pintaud; Tanguy Jaffré; Jean-Marie Veillon (1998), "Phyloghuhenetic relationships within Araucariaceae based on rbcL gene sequences", American Journal of Botany, 85 (11): 1507–1516, doi:10.2307/2446478, JSTOR 2446478, PMID 21680310
  9. ^ Linnaeus 1751, p. 54.
  10. ^ Linnaeus 1751, p. 89.
  11. ^ a b Greene, Edward Lee (1983). Egerton, Frank N. (ed.). Landmarks of botanical history: Part 2. Stanford, California: Stanford University Press. p. 1019, note 15. ISBN 978-0-8047-1075-6.
  12. ^ "Bioetymology: Origin in Biomedical Terms: cotyledon, monocotyledon (plural usually monocots), dicotyledons(plural usually dicot)". bioetymology.blogspot.com.br. Retrieved 6 April 2018.

Bibliography edit

  • Linnaeus, Carl (1755) [1751]. Philosophia botanica : in qua explicantur fundamenta botanica cum definitionibus partium, exemplis terminorum, observationibus rariorum, adiectis figuris aeneis. originally published simultaneously by R. Kiesewetter (Stockholm) and Z. Chatelain (Amsterdam). Vienna: Joannis Thomae Trattner. Retrieved 13 December 2015.
  • 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.
  • "Cotyledon". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  • Short, Emma; George, Alex (2013). A primer of botanical Latin with vocabulary. New York: Cambridge University Press. ISBN 9781107693753. Retrieved 14 December 2015.

External links edit

     
    Wikimedia Commons has media related to Cotyledon.
     
    Look up cotyledon in Wiktionary, the free dictionary.

    February 16, 2024
    cotyledon, other, uses, disambiguation, confused, with, cotyledion, cotylenol, cotyledon, seed, leaf, from, latin, cotyledon, from, κοτυληδών, kotulēdṓn, κοτυληδόνος, kotulēdónos, from, κοτύλη, kotýlē, bowl, significant, part, embryo, within, seed, plant, defi. For other uses see Cotyledon disambiguation Not to be confused with Cotyledion or cotylenol A cotyledon ˌ k ɒ t ɪ ˈ l iː d en lit seed leaf from Latin cotyledon 1 from kotylhdwn kotuledṓn gen kotylhdonos kotuledonos from kotylh kotyle cup bowl is a significant part of the embryo within the seed of a plant and is defined as the embryonic leaf in seed bearing plants one or more of which are the first to appear from a germinating seed 2 The number of cotyledons present is one characteristic used by botanists to classify the flowering plants angiosperms Species with one cotyledon are called monocotyledonous monocots Plants with two embryonic leaves are termed dicotyledonous dicots Cotyledon from a Judas tree Cercis siliquastrum a dicot seedlingComparison of a monocot and dicot sprouting The visible part of the monocot plant left is actually the first true leaf produced from the meristem the cotyledon itself remains within the seedSchematic of epigeal vs hypogeal germinationPeanut seeds split in half showing the embryos with cotyledons and primordial rootTwo week old Douglas fir a conifer with seven cotyledonsMimosa pudica a dicot seedling with two cotyledons and the first true leaf with six leafletsIn the case of dicot seedlings whose cotyledons are photosynthetic the cotyledons are functionally similar to leaves However true leaves and cotyledons are developmentally distinct Cotyledons are formed during embryogenesis along with the root and shoot meristems and are therefore present in the seed prior to germination True leaves however are formed post embryonically i e after germination from the shoot apical meristem which is responsible for generating subsequent aerial portions of the plant The cotyledon of grasses and many other monocotyledons is a 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 Gymnosperm seedlings also have cotyledons Gnetophytes cycads and ginkgos all have 2 whereas in conifers they are often variable in number multicotyledonous with 2 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 amp Styles 1997 Cotyledons may be ephemeral lasting only days after emergence or persistent enduring at least a year 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 3 Contents 1 Epigeal versus hypogeal development 2 History 3 Notes 4 References 5 Bibliography 6 External linksEpigeal versus hypogeal development editMain articles Epigeal germination and Hypogeal germination Cotyledons may be either epigeal expanding on the germination of the seed throwing off the seed shell rising above the ground and perhaps becoming photosynthetic 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 citation needed Hypogeal plants have on average significantly larger seeds than epigeal ones They are also capable of surviving if the seedling is clipped off as meristem buds remain underground with epigeal plants the meristem is clipped off if the seedling is grazed The tradeoff is whether the plant should produce a large number of small seeds or a smaller number of seeds which are more likely to survive 4 5 The ultimate development of the epigeal habit is represented by a few plants mostly in the family Gesneriaceae in which the cotyledon persists for a lifetime Such a plant is Streptocarpus wendlandii of South Africa in which one cotyledon grows to be up to 75 centimeters 2 5 feet in length and up to 61 cm two feet in width the largest cotyledon of any dicot 6 and exceeded only by Lodoicea Adventitious flower clusters form along the midrib of the cotyledon 7 The second cotyledon is much smaller and ephemeral citation needed Related plants may show a mixture of hypogeal and epigeal development even within the same plant family Groups which contain both hypogeal and epigeal species include for example the Southern Hemisphere conifer family Araucariaceae 8 the pea family Fabaceae 4 and the genus Lilium see Lily seed germination types The frequently garden grown common bean Phaseolus vulgaris is epigeal while the closely related runner bean Phaseolus coccineus is hypogeal citation needed History editThe term cotyledon was coined by Marcello Malpighi 1628 1694 a John Ray was the first botanist to recognize that some plants have two and others only one and eventually the first to recognize the immense importance of this fact to systematics in Methodus plantarum 1682 3 11 Theophrastus 3rd or 4th century BC and Albertus Magnus 13th century may also have recognized the distinction between the dicotyledons and monocotyledons 12 11 Notes edit The Oxford English Dictionary attributes it Linnaeus 1707 1778 1751 Linnaeus Philos Bot 54 Cotyledon corpus laterale seminis bibulum caducum 9 and 89 10 by analogy with a similar structure of the same name in the placenta 2 References edit Short amp George 2013 p 15 1 a b OED a b Vines Sydney Howard 1913 Robert Morison 1620 1683 and John Ray 1627 1705 in Oliver Francis Wall ed Makers of British botany Cambridge University Press pp 8 43 a b Charles R Tischler Justin D Derner H Wayne Polley Hyrum B Johnson 2007 Response of Seedlings of Two Hypogeal Brush Species to CO2 Enrichment Proceedings Shrubland dynamics fire and water 2004 August 10 12 Lubbock TX Proceedings RMRS P 47 In Sosebee Ronald E Wester David B Britton Carlton M Mcarthur e Durant Kitchen Stanley G Comps Proceedings Shrubland Dynamics Fire and Water 2004 August 10 12 Lubbock Tx Proceedings RMRS P 47 Fort Collins Co U S Department of Agriculture Forest Service Rocky Mountain Research Station P 104 106 Vol 047 Fort Collins CO U S Department of Agriculture Forest Service Rocky Mountain Research Station pp 104 106 Baraloto C Forget P M 2007 Seed size seedling morphology and response to deep shade and damage in neotropical rain forest trees American Journal of Botany 94 6 901 11 doi 10 3732 ajb 94 6 901 PMID 21636459 S2CID 24272337 Nishii Kanae Kuwabara Asuka Nagata Toshiyuki 2004 Characterization of Anisocotylous Leaf Formation in Streptocarpus Wendlandii Gesneriaceae Significance of Plant Growth Regulators Annals of Botany 94 3 457 67 doi 10 1093 aob mch160 JSTOR 42759229 PMC 4242185 PMID 15286012 Retrieved 13 December 2022 Perry Frances and Leslie Greenwood 1972 Flowers of the World London Hamlyn Publishing Group p 47 Hiroaki Setoguchi Takeshi Asakawa Osawa Jean Christophe Pintaud Tanguy Jaffre Jean Marie Veillon 1998 Phyloghuhenetic relationships within Araucariaceae based on rbcL gene sequences American Journal of Botany 85 11 1507 1516 doi 10 2307 2446478 JSTOR 2446478 PMID 21680310 Linnaeus 1751 p 54 Linnaeus 1751 p 89 a b Greene Edward Lee 1983 Egerton Frank N ed Landmarks of botanical history Part 2 Stanford California Stanford University Press p 1019 note 15 ISBN 978 0 8047 1075 6 Bioetymology Origin in Biomedical Terms cotyledon monocotyledon plural usually monocots dicotyledons plural usually dicot bioetymology blogspot com br Retrieved 6 April 2018 Bibliography editLinnaeus Carl 1755 1751 Philosophia botanica in qua explicantur fundamenta botanica cum definitionibus partium exemplis terminorum observationibus rariorum adiectis figuris aeneis originally published simultaneously by R Kiesewetter Stockholm and Z Chatelain Amsterdam Vienna Joannis Thomae Trattner Retrieved 13 December 2015 Mirov N T 1967 The Genus Pinus Ronald Press Company New York Farjon A amp Styles B T 1997 Pinus Pinaceae Flora Neotropica Monograph 75 221 224 Cotyledon Oxford English Dictionary Online ed Oxford University Press Subscription or participating institution membership required Short Emma George Alex 2013 A primer of botanical Latin with vocabulary New York Cambridge University Press ISBN 9781107693753 Retrieved 14 December 2015 External links editTiscali reference Cotyledon nbsp Wikimedia Commons has media related to Cotyledon nbsp Look up cotyledon in Wiktionary the free dictionary Retrieved from https en wikipedia org w index php title Cotyledon amp oldid 1171003548, wikipedia, wiki, book, books, library,

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