- Cotyledon. The first leaf or pair of leaves of an embryo and seedling, often a food-storage organ. The cotyledons may remain in the seed (hypogeal germination) or emerge to become the first photosynthetic organs (epigeal germination). ISTA Handbook on Pure Seed Definitions, Glossary. 3rd Edition 2010.
- Cotyledons. The cotyledons are the storage structures of the embryo. They may be only a small portion of the seed in species with endosperm, perisperm or female gametophyte storage tissue, or they may occupy a large portion of the embryo when they are the primary storage tissue (e.g. Phaseolus vulgaris). In epigeal species, the cotyledons may grow quite large and become the first photosynthetic structures of the young plant. In hypogeal species the primary function of the cotyledons is to provide nutrients to the growing seedling until it can produce its own nutrients. In most species the cotyledons shrivel and drop off as their reserves are depleted. In a few species (e.g. Cucurbita pepo, pumpkin) the cotyledons may persist well beyond the seedling stage of growth. In the monocotyledons the cotyledon absorbs nutrients from the endosperm and transfers them to the growing seedling. In the Poaceae the cotyledon is called the scutellum. It is in close proximity to the endosperm and is laterally attached to the embryo axis. In Allium (Liliaceae) the cotyledon tip remains embedded in the endosperm to absorb nutrients but the cotyledon also emerges from the soil (i.e. germination is epigeal) and becomes photosynthetic. Association of Official Seed Analysts (AOSA) Rules for Seed Testing, Volume 4, 2019
- Cotyledon. The first leaves of the embryo that serve for food digestion and food storage. Fenwick, J.R. revised 1995. Laboratory Manual for General Crops- Glossary. Unpublished class notes. Dept. of Soil and Crop Sciences, Colorado State University. Pages 104-111
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