A seed is a fertilized, mature ovule with an embryo and a store of food enclosed in a hard seed coat. It completes the reproductive process of gymnosperm and angiosperm plants.
A seed lies dormant until conditions are right for germination. Most seeds require a certain temperature and moisture for growth to begin.
Definition
A seed is a fertilized mature ovule that contains an embryo or miniature undeveloped plant together with stored food reserves in the form of a testa and a protective coat. Seeds are the characteristic reproductive organ of flowering plants, and are found in all gymnosperms (naked-seeded plants such as cycads and conifers) and angiosperms.
Viable seeds possess innate dormancy, which is the ability to resist germination until environmental conditions are optimal. Dormancy may be induced before or during maturation, or in the case of endospermic seeds, it may be evoked after seed dispersal from its mother plant.
A seed article is one that is so short that a relatively knowledgeable editor could improve its content with only a superficial web search or quick reference check. An article that would be improved only with significant research is not considered a seed.
Origin
Seeds are a characteristic feature of the spermatophytes, plants that contain ovary-like structures for storing and dispersing their young. They are mainly found in gymnosperms (naked-seeded plants) and angiosperms (flowering plants).
Before seeds evolved, most land plants, including ferns and mosses, reproduced by spreading their spores into the air where they could land and grow into new plants. The evolution of seeds began somewhere in the Devonian period some 385 million years ago.
A seed contains an embryo and a nutrient tissue called endosperm, which it gets from its mother plant. It is also referred to as the functional megaspore wall in some species. The development of the functional megaspore wall is a process called megasporogenesis. Seeds that develop with physiological dormancy are characterized by their inability to germinate until exposed to certain environmental triggers.
Function
Seeds are vital in keeping a species alive through periods of unfavorable conditions and in distributing plants from place to place. The outer seed coat protects the embryo plant and may hold a supply of food for it (endosperm).
There is usually an embryo in a seed, which can be either single in monocots or double in dicots. There are also cotyledons, or seed leaves, attached to the embryo.
The cotyledons are a source of nutrients for the young seedling until it can make its own food by photosynthesis. The epicotyl is a stalk that extends from the point of attachment of the cotyledon(s) and will become the shoot. Physiological dormancy may be broken by cool wet or cool dry conditions, or by a process called stratification which involves adding water and allowing the seeds to undergo a period of moist chilling.
Varieties
When seed catalogs arrive, gardeners spend hours poring over the many varieties they can choose from. Gardeners can select from reliable industry standards, heirloom favorites and locally recommended varieties.
A variety is a distinctive strain of a crop that has been tested to show consistent performance and adaptability to growing conditions. A variety may be open pollinated (plants self-pollinate), hybrid or inbred.
Inbred seeds are derived from parent plants that have been bred for consistency and uniformity. Hybrid seeds are made when the pollen of two different plant varieties is artificially controlled. Company names may be used in a variety name, but once they become part of the legal name, anyone marketing that seed must use the full, legally assigned name. This can prevent confusion and protect brand identity.
Uses
Seeds are an important source of food for animals and humans. The seeds of cereal grains (wheat, corn, rice) are staples in many diets, while those of legumes (beans, peas, peanuts) provide important protein. Seeds also supply oils for cooking and for lubrication (linseed oil, jojoba oil, and castor oil), fibers for textiles, woody fibers, and some medicines, such as laetrile and ginseng.
Seeds can be dispersed by animal consumption or by wind, water, or gravity. Several adaptations allow for their long-distance transport, including fleshy appendages that attract animal dispersers; hooks and barbs that stick to fur and feathers; or wings for wind-based dispersal. Seeds are a major vehicle for the dissemination of improved varieties and hybrids in agriculture. The introduction of high-yielding varieties and hybrids has greatly increased crop yields.
