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Seed

Seed

A seed is a part of a flowering plant involved in reproduction. It consists of three major parts: the embryo, endosperm, and testa. The embryo is produced when male and female elements are combined during reproduction. It will eventually grow into a new plant. The endosperm is a collection of stored food the young plant will use as it begins to germinate, or grow. The testa is a tough outer layer that protects the embryo and endosperm from damage by outside factors.

Two kinds of seed plants exist. Gymnosperms are plants that produce naked seeds. The most common type of gymnosperms are conifers, cone-bearing trees and shrubs such as firs, hemlocks, junipers, larches, pines, and spruce. Angiosperms are plants whose seeds are enclosed in a protective structure called the fruit. Angiosperms are also known as flowering plants because they produce flowers in which seeds are produced and in which they develop.

Seed production

Seeds are produced when pollen is released from the male (stamen) part of a plant. That pollen comes into contact with the ovules of the female (pistil) parts of a plant. Some kinds of plants contain both male and female organs on the same plant. In that case, self-fertilization can occur when pollen from one part of the plant fertilizes ovules on another part of the same plant.

In most plants, fertilization occurs between two different plants, one of which contains only male flowers and the other only female flowers. This process requires some kind of mechanism by which pollen can be carried between plants. In some cases, movement of air (wind) can bring about this kind of fertilization. Insects and birds can also produce the same result. For example, a bee may visit a male plant in search of nectar. In that search, the bee may rub off pollen onto its body. When the bee then visits a female plant, it may release that pollen onto the ovules of the second plant, making fertilization possible.

The endosperm within a seed is used when the embryo begins to develop. Seeds vary widely in terms of the relative amounts of embryo and endosperm they may contain. For example, members of the orchid family have tiny, dustlike seeds that consist of little more than core embryonic tissues, with very little in the way of energy reserves. In contrast, the gigantic seeds of some coconuts can weigh more than 60 pounds (25 kilograms), most of which is nutritional reserve surrounded by fibrous, protective husk.

Words to Know

Angiosperm: A plant whose seeds are enclosed in a protective structure called the fruit.

Dispersal: Any process by which seeds are spread outward from their parent plant.

Dormancy: A state of inactivity in an organism.

Embryo: The young form of an organism.

Endosperm: A collection of stored food used by a young plant during germination.

Germination: The beginning of growth of a seed.

Gymnosperm: A plant that produces naked seeds.

Pistil: The female reproductive organ in a plant.

Pollination: The transfer of pollen from the male organ of a plant to the female organ.

Self-fertilization: The process in which pollen from one part of a plant fertilizes ovules on another part of the same plant.

Stamen: The male reproductive organ in a plant.

Testa: A tough outer layer that protects the embryo and endosperm of a seed from damage.

Seed dispersal

A seed exists in a dormant (sleeping) state. It begins to germinate, or grow, only when it is deposited in a favorable environment, such as moist, warm ground. The long process by which a seed changes from a tiny embryo into a fully grown plant requires time and favorable conditions. In most cases, young plants have a better chance to survive and grow if they are deposited at some distance from the parent plant. In those cases, they will not have to compete for sunlight, water, and nutrients with their own parents.

There are, however, some important exceptions to this general rule. For example, the adults of annual species of plants die at the end of their breeding season. In those cases the parent plants do not compete with their seeds. Nevertheless, even annual plants tend to disperse their seeds widely.

Methods of dispersal. Plants have evolved a variety of mechanisms to disperse their seeds effectively. In some plant species, seeds are very buoyant, so they can be dispersed over great distances by the winds. Some well-known examples of this kind of plant are the fluffy seeds of the dandelion and fireweed. The seeds of maple trees are also dispersed by the wind. These seeds have a one-sided wing that causes them to swirl propeller-like after they are released from a parent tree. This structure allows maple seeds to be carried by even light breezes some distance from their parent before they hit the ground.

Some plants have developed an interesting method of dispersal, known as tumbleweeding. These plants grow into a roughly spherical shape. After the seeds are ripe, the mature plant detaches from the ground surface and is then blown about by the wind, shedding its seeds widely as it tumbles along.

The seeds of many other species of plants are dispersed by animals. Some seeds have structures that allow them to attach to the fur or feathers of passing animals, who then carry the seeds some distance away from the parent plant before they are deposited to the ground. One example of this mechanism is burdock, whose spherical fruits have numerous hairs with tiny hooked tips that stick to fur. This fruit also sticks to human clothing, and was the botanical model that inspired the invention of Velcro, a sticky, synthetic fastening material.

Another mechanism by which seeds are dispersed by animals involves their encasement in a fleshy, edible fruit. Such fruits are often brightly colored, have pleasant odors, and are nutritious and attractive to herbivorous (plant-eating) animals. These animals eat the fruit, seeds and all. After the fruit passes through the animal's digestive system, the seeds are dispersed at some distance from the parent plant.

The seeds of many plants with this sort of animal-dispersal strategy actually require passage through the gut of an animal before they will germinate. Some familiar examples of species that develop animal-dispersed fruits include the cherries, tomatoes, and watermelon.

Seed germination

After seeds have been dispersed into the environment, they may remain in a dormant state for some time, until appropriate cues are sensed for germination. Such clues include sufficient water, oxygen, and an appropriate temperature. Interestingly enough, the seeds of many species will not germinate even under favorable conditions. For example, seeds produced and dispersed just before the beginning of a cold season might actually experience the right conditions for germination for a short period of time. However, they would probably not survive if they germinated at once. A period of dormancy enables the seeds to wait out the cold season, and to begin growth when conditions are more favorable for the mature plant, in the springtime. It allows seeds a better chance of surviving unfavorable conditions and developing successfully into plants.

Germination begins with an increase of metabolic activity within the seed (that is, organic compounds are broken down to produce energy). The first visible sign of germination in angiosperms is generally an enlargement of the seed. That enlargement is caused by an intake of water from the environment. The seed's covering may wrinkle and crack at this

time. Soon afterward, the embryonic root emerges from the seed and begins to grow down into the soil. At about this time the shoot also emerges and grows upward out of the soil.

Uses of seeds

Seeds are used by humans for a number of purposes. The most important of those uses are as foods. Some seeds are eaten directly, while other are used to manufacture flour, starch, oil, alcohol, or some other edible products. Some examples of such seeds include those of wheat, rice, maize, sorghum, barley, peanut, soybean, lentil, common pea, common bean, coconut, walnut, pecan, and sunflower.

Many other seeds are eaten with their fruits, although it is generally the encasing fruit walls that are the sought-after source of nutrition. A few examples of edible fruits include those of the pumpkin or squash, bell pepper, apple, sweet cherry, strawberry, raspberry, and sweet orange.

[See also Plant; Reproduction ]

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"Seed." UXL Encyclopedia of Science. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

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seed

seed / sēd/ • n. 1. a flowering plant's unit of reproduction, capable of developing into another such plant. ∎  a quantity of these: grass seed you can grow artichokes from seed. ∎ fig. the cause or latent beginning of a feeling, process, or condition: the conversation sowed a tiny seed of doubt in his mind. ∎ archaic (chiefly in biblical use) a person's offspring or descendants. ∎  a man's semen. ∎  (also seed crystal) a small crystal introduced into a liquid to act as a nucleus for crystallization. ∎  a small container for radioactive material placed in body tissue during radiotherapy. 2. any of a number of stronger competitors in a sports tournament who have been assigned a specified position in an ordered list with the aim of ensuring that they do not play each other in the early rounds: he knocked the top seed out of the championships. • v. 1. [tr.] sow (land) with seeds: the shoreline is seeded with a special grass. ∎  sow (a particular kind of seed) on or in the ground. ∎ fig. cause (something) to begin to develop or grow: severance payouts that help seed their new businesses. ∎  place a crystal or crystalline substance in (something) in order to cause crystallization or condensation (esp. in a cloud to produce rain). 2. [intr.] (of a plant) produce or drop seeds: mulches encourage many plants to seed freely. ∎  (seed itself) (of a plant) reproduce itself by means of its own seeds: feverfew will seed itself readily. 3. [tr.] remove the seeds from (vegetables or fruit): stem and seed the chilies. 4. [tr.] give (a competitor) the status of seed in a tournament: Jeff Tarango, seeded five, was defeated by fellow American Todd Witsken. PHRASES: go (or run) to seed (of a plant) cease flowering as the seeds develop. ∎  deteriorate in condition, strength, or efficiency: Mark knows he has allowed himself to go to seed.

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"seed." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

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"seed." The Oxford Pocket Dictionary of Current English. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/seed-0

seed

seed, fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing them in flowering plants, especially in grains and nuts. The seed-bearing plants arose more recently in evolution; in more ancient plants (e.g., mosses and ferns) the spore is the agent of propagation. True seeds vary in size from the dustlike seeds of some orchids to the large seed contained in the coconut. The period of dormancy undergone by many seeds before germination also varies; the mangrove seed may sprout inside a fruit still hanging on the tree, while a seed of a sacred lotus dated at about 1,200 years and one of a date palm about 2,000 years old have been germinated. Long dormancy in some seeds is ensured by their extremely hard coats, which have to be scratched or split to force sprouting. In plant breeding, the source of pollen for fertilization is carefully controlled to produce the desired qualities in seed; under natural conditions a plant grown from seed may be quite different genetically from its maternal plant (see fertilization).

See study by J. Silvertown (2009).

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"seed." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/seed

"seed." The Columbia Encyclopedia, 6th ed.. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/seed

seed

seed The structure in angiosperms and gymnosperms that develops from the ovule after fertilization. Occasionally seeds may develop without fertilization taking place (see apomixis). The seed contains the embryo and nutritive tissue, either as endosperm or food stored in the cotyledons. Angiosperm seeds are contained within a fruit that develops from the ovary wall. Gymnosperm seeds lack an enclosing fruit and are thus termed naked. The seed is covered by a protective layer, the testa. During development of the testa the seed dries out and enters a resting phase (dormancy) until conditions are suitable for germination.

Annual plants survive the winter or dry season as seeds. The evolution of the seed habit enabled plants to colonize the land, since seed plants do not depend on water for fertilization (unlike the lower plants).

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"seed." A Dictionary of Biology. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." A Dictionary of Biology. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed-1

"seed." A Dictionary of Biology. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed-1

seed

seed that which is or is to be sown; †offspring OE.; †semen XIII. OE. sǣd, Ang. sēd, corr. to OS. sād (Du. zaad), OHG. sāi (G. saat), ON. sáð, Goth. -sēps :- Gmc. *sǣðiz, *sǣðam, f. *sæ- SOW2.
Hence seed vb. XIV (intr.). seedling XVII. seedy full of seed XVI; (sl.) shabby (from the appearance of a plant that has run to seed) XVIII; unwell XIX. Hence seedlip basket for seed. OE. sǣdlēap; f. lēap basket.

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"seed." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/seed-1

"seed." The Concise Oxford Dictionary of English Etymology. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/seed-1

seed

seed Part of a flowering plant that contains the embryo and food store. It is formed in the ovary by fertilization of the female gamete (see pollen). Food may be stored in a special tissue called the endosperm, or may be concentrated in swollen seed leaves (cotyledons). Seeds are the unit of dispersal of angiosperms and conifers. See also fruit; germination

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"seed." World Encyclopedia. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." World Encyclopedia. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/seed

"seed." World Encyclopedia. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/seed

seed

seed In the sexual reproduction of Spermatophyta (seed plants), the discrete body from which a new plant develops. Formed from a fertilized ovule, the seed comprises an outer coat (testa) that encloses a food store and an embryo plant. The food may be stored in the cotyledons (seed leaves) of the embryo itself or around the embryo in the endosperm.

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"seed." A Dictionary of Plant Sciences. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." A Dictionary of Plant Sciences. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed-0

"seed." A Dictionary of Plant Sciences. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed-0

seed

seed
1. In the sexual reproduction of seed plants (Spermatophyta), the discrete body from which a new plant develops. Formed from a fertilized ovule, the seed comprises an outer coat (testa) enclosing a food store and an embryo plant.

2. Any plant or animal structure concerned with propagation.

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"seed." A Dictionary of Ecology. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

"seed." A Dictionary of Ecology. . Encyclopedia.com. (April 28, 2017). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed

"seed." A Dictionary of Ecology. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/seed

seed

seedaccede, bead, Bede, bleed, breed, cede, concede, creed, deed, Eid, exceed, feed, Gide, God speed, greed, he'd, heed, impede, interbreed, intercede, Jamshid, knead, lead, mead, Mede, meed, misdeed, mislead, misread, need, plead, proceed, read, rede, reed, Reid, retrocede, screed, secede, seed, she'd, speed, stampede, steed, succeed, supersede, Swede, tweed, weak-kneed, we'd, weed •breastfeed • greenfeed • dripfeed •chickenfeed • spoonfeed • nosebleed •Nibelungenlied • invalid • Ganymede •Runnymede • airspeed • millipede •velocipede • centipede • Siegfried •filigreed • copyread • crossbreed •proofread • flaxseed • hayseed •rapeseed • linseed • pumpkinseed •aniseed • oilseed • birdseed • ragweed •knapweed • seaweed • chickweed •stinkweed • blanket weed • bindweed •pondweed • duckweed • tumbleweed •fireweed • waterweed • silverweed

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"seed." Oxford Dictionary of Rhymes. . Encyclopedia.com. 28 Apr. 2017 <http://www.encyclopedia.com>.

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"seed." Oxford Dictionary of Rhymes. . Retrieved April 28, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/seed