cotyledon

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cotyledon (seed leaf) A part of the embryo in a seed plant. The number of cotyledons is an important feature in classifying plants. Among the flowering plants, the class known as Monocotyledoneae have a single cotyledon and Dicotyledoneae have two. Conifers have either two cotyledons, as in Taxus (yews), or five to ten, as in Pinus (pines). In seeds without an endosperm, e.g. garden pea and broad bean, the cotyledons store food, which is used in germination. In seeds showing epigeal germination, e.g. runner bean, they emerge above the soil surface and become the first photosynthetic leaves.

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cot·y·le·don / ˌkätlˈēdn/ • n. Bot. an embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed. DERIVATIVES: cot·y·le·don·ar·y / -ˈēdnˌerē/ adj.

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cotyledon (kŏt´əlēd´ən), in botany, a leaf of the embryo of a seed. The embryos of flowering plants, or angiosperms, usually have either one cotyledon (the monocots) or two (the dicots). Seeds of gymnosperms, such as pines, may have numerous cotyledons. In some seeds the cotyledons are flat and leaflike; in others, such as the bean, the cotyledons store the seed's food reserve for germination and are fleshy. In most plants the cotyledons emerge above the soil with the seedling as it grows. They differ in form from the true leaves.

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cotyledon First leaf or pair of leaves produced by the embryo of a flowering plant. Its function is to store and digest food for the embryo plant, and, if it emerges above ground, to photosynthesize for seedling growth. See also dicotyledon; monocotyledon

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cotyledon A seed leaf that is borne on a plant embryo. Characteristically there is 1 leaf in the monocotyledons, and 2 leaves in the dicotyledons, but there are exceptions, especially in the latter group.

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cotyledon seed-leaf. XVIII. — L. cotylēdon navelwort, pennywort — Gr. kotúlēdṓn applied to various cup-shaped cavities, f. kotúlē hollow, cup.

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cotyledon (kot-i-lee-dŏn) n. any of the major convex subdivisions of the mature placenta. Each cotyledon contains a major branch of the umbilical blood vessels.