seed [%PREMIUM_LINK%] (sēd) Pronunciation Key |
Noun A mature fertilized ovule of angiosperms and gymnosperms that contains an embryo and the food it will need to grow into a new plant. Seeds provide a great reproductive advantage in being able to survive for extended periods until conditions are favorable for germination and growth. The seeds of gymnosperms (such as the conifers) develop on scales of cones or similar structures, while the seeds of angiosperms are enclosed in an ovary that develops into a fruit, such as a pome or nut. The structure of seeds varies somewhat. All seeds are enclosed in a protective seed coat. In certain angiosperms the embryo is enclosed in or attached to an endosperm, a tissue that it uses as a food source either before or during germination. All angiosperm embryos also have at least one cotyledon. The first seed-bearing plants emerged at least 365 million years ago in the late Devonian Period. Many angiosperms have evolved specific fruits for dispersal of seeds by the wind, water, or animals. See more at germination, ovule.