Seed: a structure containing a plant embryo, a food reserve, and a protective coat. Seeds are the reproductive units of gymnosperms (conifers, cycads) and angiosperms (flowering plants). Each seed packages the next generation in a self-contained unit — the embryo carries the genetic blueprint, the endosperm or cotyledons provide the energy for initial growth, and the seed coat shields both from desiccation, mechanical damage, and pathogens until conditions favor germination.
The evolution of the seed was a major innovation in the history of land plants. It freed plant reproduction from dependence on water for fertilization — unlike ferns and mosses, which require a film of water for sperm to swim to eggs, seed plants deliver sperm via pollen, and the embryo develops within the protected environment of the ovule. This breakthrough allowed seed plants to colonize drier habitats and dominate terrestrial ecosystems. In angiosperms, seeds develop within a flower’s ovary, which matures into a fruit that further aids dispersal.
Seeds can remain dormant for years or even decades, germinating only when specific environmental conditions — temperature, moisture, light, or chemical signals — indicate that survival is likely. This dormancy is not passive inactivity but a regulated developmental arrest, maintained by hormone balances (particularly abscisic acid and gibberellins) and broken by environmental cues. Seed dispersal mechanisms — wind, water, animal ingestion, explosive dehiscence — shape plant distribution and ecology, linking the reproductive strategy of individual plants to the structure of entire landscapes.
Related terms
- Flower — the reproductive structure in which angiosperm seeds develop
- Pollination — the transfer of pollen that precedes seed formation
- Root — the first organ to emerge from a germinating seed
- Meristem — the embryonic meristems within the seed give rise to the new plant’s shoot and root
- Evolution — the seed as a key evolutionary innovation in plant history