Cotyledon

A cotyledon, or seed leaf, is a leaf that is stored in a seed. When the seed sprouts, the cotyledons are the first leaves that the plant has. Monocot plants have only one cotyledon, and other plants have two. Cotyledons often look very different from the other leaves, so they are not called true leaves.

Plants use cotyledons to make sugars through photosynthesis. They use the sugars to keep true leaves growing. After a while, the cotyledons often die because the plant does not need them anymore.

Cotyledon Media

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  Cotyledon from a Judas-tree (Cercis siliquastrum, a dicot) seedling

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  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.

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  Schematic of epigeal vs hypogeal germination

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  Peanut seeds split in half, showing the embryos with cotyledons and primordial root

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  Two-week-old Douglas fir (a conifer) with seven cotyledons

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  Mimosa pudica (a dicot) seedling with two cotyledons and the first "true" leaf with six leaflets