Jim Bidlack - BIO 5354/4354 PLANT ANATOMY Lecture 28 - Seeds and Seedlings I. Generalized seed structure A. Where the seed comes from 1. Double fertilization A. Fusion of egg and sperm (zygote) B. Fusion of two polar nuclei with second sperm (endosperm) B. Parts of the seed 1. Embryo (from zygote) 2. Endosperm (may or may not be present in mature seed) 3. Seed coat (from integuments) II. Kinds of seeds A. Dicots - endosperm is partially or completely absorbed by the embryo by cotyledons 1. Seed coat (external structure) A. Hilum - place where seed was attached to plant B. Micropyle - small opening in the integuments 2. Embryo A. Embryo axis 1. Plumule (shoot apex, first foliage leaves, and epicotyl) 2. Epicotyl (portion beneath leaves) 3. Hypocotyl (portion beneath cotyledonary node) B. Cotyledons C. Radicle (primary root) 3. Stored food and mineral reserves (in cotyledons and other tissues) 4. Enzymes and hormones (found everywhere) B.
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