Crossword clues for cotyledon
The Collaborative International Dictionary
Cotyledon \Cot`y*le"don\ (k?t`?-l?"d?n), n. [Gr.??? a cupshaped hollow, fr. ???. See Cotyle.]
(Anat.) One of the patches of villi found in some forms of placenta.
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(Bot.) A leaf borne by the caulicle or radicle of an embryo; a seed leaf.
Note: Many plants, as the bean and the maple, have two cotyledons, the grasses only one, and pines have several. In one African plant ( Welwitschia) the cotyledons are permanent and grow to immense proportions.
Douglas Harper's Etymology Dictionary
from 1540s, in various sense, from Latin cotyledon "pennywort, navelwort," from Greek kotyledon "cup-shaped cavity," from kotyle "hollow thing, small vessel," also the name of a small liquid measure (nearly a half-pint); which is of uncertain origin. Botanical sense is 1776, from Linnaeus (1751).
Wiktionary
n. (context botany English) The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling.
WordNet
n. embryonic leaf in seed-bearing plants [syn: seed leaf]
Wikipedia
A cotyledon (; "seed leaf" from Latin cotyledon, from Greek: κοτυληδών kotylēdōn, gen.: κοτυληδόνος kotylēdonos, from κοτύλη kotýlē "cup, bowl") is a significant part of the embryo within the seed of a plant, and is defined by the Oxford English Dictionary as "The primary leaf in the embryo of the higher plants (Phanerogams); the seed-leaf." Upon germination, the cotyledon may become 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 ("monocots"). Plants with two embryonic leaves are termed dicotyledonous ("dicots") and placed in the class Magnoliopsida.
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, 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).
The 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.
Cotyledon is a genus of succulent plants in the Crassulaceae family. Mostly from Southern Africa, they also occur throughout the drier parts of Africa as far north as the Arabian peninsula.
A cotyledon is a significant part of the embryo within the seed of a plant.
Cotyledon may also refer to:
- Cotyledon (genus), a plant genus in the Crassulaceae family
- Cotyledon (placenta), a part of the anatomy of mammals
- Saxifraga cotyledon, a species of saxifrage, a plant
Usage examples of "cotyledon".
The ellipse described on the 29th had its longer axis directed at nearly right angles to a line joining the two cotyledons.
It has already been stated that the cotyledons of Phalaris and Avena, the plumules of Asparagus and the hypocotyls of Brassica, were likewise able to displace the same kind of sand, either whilst simply circumnutating or whilst bending towards a lateral light.
As the tips of the cotyledons of Phalaris and Avena bend upwards through the action of apogeotropism before the basal part, and as these same tips when excited by a lateral light transmit some influence to the lower part, causing it to bend, we thought that the same rule might hold good with apogeotropism.
When the cotyledons of Phalaris and Avena were covered with grease along one side, the growth of this side was quite stopped or greatly checked, and as the opposite side continued to grow, the cotyledons thus treated became bowed towards the greased side.
When the cotyledons are exposed to a lateral light, the upper part bends first, and afterwards the bending gradually extends down to the base, and, as we shall presently see, even a little beneath the ground.
The sheathlike cotyledons of the Gramineae circumnutate, that is, move to all sides, as plainly as do the hypocotyls or epicotyls of any dicotyledonous plants.
We may, also, suspect that the extreme sensitiveness to light of the upper part of the sheathlike cotyledons of the Gramineae, and their power of transmitting its effects to the lower part, are specialised arrangements for finding the shortest path to the light.
In the Gramineae the summit of the straight, sheathlike cotyledon is developed into a hard sharp crest, which evidently serves for breaking through the earth.
The cotyledons of several other species of Ipomoea likewise sink downwards late in the evening.
With all the above species of Ipomoea, when the two cotyledons on the same seedling were unequally depressed at night, this seemed to depend on the position which they had held during the day with reference to the light.
There are, however, some strong exceptions to this rule, as the cotyledons of Gossypium, Anoda and Ipomoea do not possess pulvini, yet continue to move and to grow for a long time.
Ultimately not a trace of the former curvature is left, except in the case of the leaflike cotyledons of the onion.
In the Leguminosae all the cotyledons which sleep, as far as we have seen, are provided with pulvini.
As in the Leguminosae and Oxalidae, the leaves and the cotyledons of the same species generally sleep, the idea at first naturally occurred to us, that the sleep of the cotyledons was merely an early development of a habit proper to a more advanced stage of life.
The fact of tubers being formed by the foregoing three widely distinct plants, makes us believe that their protection from animals at an early age and whilst tender, is one at least of the advantages gained by the remarkable elongation of the petioles of the cotyledons, together with their power of penetrating the ground like roots under the guidance of geotropism.