cotyledon

cotyledon

1. Botany a simple embryonic leaf in seed-bearing plants, which, in some species, forms the first green leaf after germination

2. Anatomy a tuft of villi on the mammalian placenta

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

cotyledon

[‚käd·əl′ēd·ən]

(botany)

The first leaf of the embryo of seed plants.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Cotyledon

 

one of the first leaves of a plant. The cotyledons form in the seed on the not yet differentiated body of the developing embryo. They often differ sharply in shape, internal structure, and, sometimes, function from subsequent leaves that arise on the growing point of the shoot. Gymnospermous plants have two to 15 cotyledons, dicotyledonous plants two cotyledons, and most monocotyledonous plants one cotyledon. When there is aboveground sprouting of dicotyledon seeds (for example, beans), green cotyledons emerge at the soil surface and for some time perform the functions of green leaves. In peas, oak, walnut, and a number of other plants the cotyledons upon sprouting remain in the seed and die after consumption of nutrient reserves. During the sprouting of many monocotyledons, the sheath portion of the cotyledon emerges from the seed, but the apex remains for some time in the endosperm, functioning as an organ of absorption. The same function is performed by the scutellum that remains in the seed of cereal grains; many botanists consider the scutellum to be a cotyledon.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.