Diagram of Scouler's willow (Salix scouleriana) seed, indicating position of hypocotyl.

The hypocotyl (short for "hypocotyledonous stem",[1] meaning "below seed leaf") is the stem of a germinating seedling, found below the cotyledons (seed leaves) and above the radicle (root).



As the plant embryo grows at germination, it sends out a shoot called a radicle that becomes the primary root and penetrates down into the soil. After emergence of the radicle, the hypocotyl emerges and lifts the growing tip (usually including the seed coat) above the ground, bearing the embryonic leaves (called cotyledons) and the plumule that gives rise to the first true leaves. The hypocotyl is the primary organ of extension of the young plant and develops into the stem.


The early development of a monocot seedling like cereals and other grasses is somewhat different. A structure called the coleoptile, essentially a part of the cotyledon, protects the young stem and plumule as growth pushes them up through the soil. A mesocotyl—that part of the young plant that lies between the seed (which remains buried) and the plumule—extends the shoot up to the soil surface, where secondary roots develop from just beneath the plumule. The primary root from the radicle may then fail to develop further. The mesocotyl is considered to be partly hypocotyl and partly cotyledon (see seed).

Not all monocots develop like the grasses. The onion develops in a manner similar to the first sequence described above, the seed coat and endosperm (stored food reserve) pulled upwards as the cotyledon extends. Later, the first true leaf grows from the node between the radicle and the sheath-like cotyledon, breaking through the cotyledon to grow past it.

Storage organ

In some plants, the hypocotyl becomes enlarged as a storage organ. Examples include cyclamen, gloxinia and celeriac. In cyclamen, this storage organ is called a tuber.

See also


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Hypocotyl — Hypocotyl, Sprossabschnitt zwischen Keimblättern und Keimwurzel beim Embryo der Cormophyten …   Deutsch wörterbuch der biologie

  • hypocotyl — [hī΄pō kät′ l, hip΄ōkät′ l] n. [ HYPO + COTYL(EDON)] the part of the axis, or stem, below the cotyledons in the embryo of a plant …   English World dictionary

  • Hypocotyl — Hypokotyl einer Jeffrey Kiefer Hypokotyl (gr.: hypo = unterhalb und kotyle = Höhlung; engl.: Hypocotyl) ist ein Fachausdruck der Botanik und bezeichnet den untersten Abschnitt der Sprossachse einer Samenpflanze vom Wurzelhals (das ist die… …   Deutsch Wikipedia

  • hypocotyl — Part of the axis of a plant embryo or seedling between the point of insertion of the cotyledon(s) and the top of the radicle (root). In some etiolated seedlings, the hypocotyl is greatly extended …   Dictionary of molecular biology

  • hypocotyl — poskiltis statusas T sritis augalininkystė apibrėžtis Apatinė daigo stiebo dalis nuo šaknies iki skilčialapių. atitikmenys: angl. hypocotyl rus. гипокотиль; подсемядольное колено ryšiai: sinonimas – hipokotilis …   Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas

  • hypocotyl — noun Etymology: International Scientific Vocabulary hypo + cotyledon Date: 1880 the part of the axis of a plant embryo or seedling below the cotyledon …   New Collegiate Dictionary

  • Hypocotyl — Hypocotyle Partie de la tige située entre la base de la tige (collet) et les premiers cotylédons de la plante. La tige est verticale. Organes végétaux Organes aériens Bourgeon • Bulbe • Écorce • Épine • Feuille • Foliole • Cotylédon • Fleur •… …   Wikipédia en Français

  • hypocotyl — hypocotylous, adj. /huy peuh kot l/, n. Bot. the part of a plant embryo directly below the cotyledons, forming a connection with the radicle. See diag. under cotyledon. [1875 80; HYPO + COTYL(EDON)] * * * …   Universalium

  • hypocotyl — noun In plants with seeds, that portion of the embryo or seedling between the root and cotyledons …   Wiktionary

  • hypocotyl — hy·po·cot·yl (hi″po kotґəl) [hypo + kotyle hollow] the part of the axis of a plant embryo or seedling below the point of attachment of the cotyledon and from which the radicle, or primary root, grows …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”