Key Points
Key Points: Structure of Monocotyledonous Seed
- Monocot seed: Usually endospermic, with endosperm storing food (except orchids).
- Endosperm: Large and bulky, separated from the embryo by a protein-rich aleurone layer.
- Embryo: Consists of a single cotyledon called the scutellum and a short embryonal axis.
- Cotyledon: Only one large, shield-shaped cotyledon present.
- Radicle and plumule: Radicle is enclosed in the coleorhiza, and plumule in the coleoptile.
- Seed structure: The seed coat is often fused with the fruit wall, and the embryo lies at one side of the endosperm.
Key Points: Structure of a Dicotyledonous Seed
- Seed coat: Consists of two layers—testa (outer) and tegmen (inner).
- Hilum: A scar on the seed coat showing the point of attachment to the fruit.
- Micropyle: A small pore present above the hilum helps in water absorption.
- Cotyledons: Two fleshy cotyledons present, storing reserve food material.
- Embryo: Contains an embryonal axis with radicle and plumule at opposite ends.
- Endosperm: May be present (e.g., castor) or absent (e.g., bean, gram, pea) in mature seeds.
