Seed
Overview
A seed is a small embryonic
Plant embryogenesis
Plant embryogenesis is the process that produces a plant embryo from a fertilised ovule by asymmetric cell division and the differentiation of undifferentiated cells into tissues and organs. It occurs during seed development, when the single-celled zygote undergoes a programmed pattern of cell...

 plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 enclosed in a covering called the seed coat, usually with some stored food
Food storage
Food storage is both a traditional domestic skill and is important industrially. Food is stored by almost every human society and by many animals...

. It is the product of the ripened ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...

 of gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...

 and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed plants (started with the development of flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s and pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...

), with the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 developed from the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

 and the seed coat from the integuments of the ovule.

Seeds have been an important development in the reproduction and spread of flowering plants, relative to more primitive plants like moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

es, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s and liverworts
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....

, which do not have seeds and use other means to propagate themselves.
Encyclopedia
A seed is a small embryonic
Plant embryogenesis
Plant embryogenesis is the process that produces a plant embryo from a fertilised ovule by asymmetric cell division and the differentiation of undifferentiated cells into tissues and organs. It occurs during seed development, when the single-celled zygote undergoes a programmed pattern of cell...

 plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 enclosed in a covering called the seed coat, usually with some stored food
Food storage
Food storage is both a traditional domestic skill and is important industrially. Food is stored by almost every human society and by many animals...

. It is the product of the ripened ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...

 of gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...

 and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed plants (started with the development of flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s and pollination
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...

), with the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 developed from the zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

 and the seed coat from the integuments of the ovule.

Seeds have been an important development in the reproduction and spread of flowering plants, relative to more primitive plants like moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...

es, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s and liverworts
Marchantiophyta
The Marchantiophyta are a division of bryophyte plants commonly referred to as hepatics or liverworts. Like other bryophytes, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of genetic information....

, which do not have seeds and use other means to propagate themselves. This can be seen by the success of seed plants (both gymnosperms and angiosperms) in dominating biological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

s on land, from forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

s to grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

s both in hot and cold climates.

The term seed also has a general meaning that predates the above — anything that can be sown
Sowing
Sowing is the process of planting seeds.-Plants which are usually sown:Among the major field crops, oats, wheat, and rye are sowed, grasses and legumes are seeded, and maize and soybeans are planted...

, e.g. "seed" potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

es, "seeds" of corn
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...

 or sunflower "seeds"
Sunflower seed
The sunflower seed is the fruit of the sunflower . The term "sunflower seed" is actually a misnomer when applied to the seed in its pericarp . Botanically speaking, it is more properly referred to as an achene. When dehulled, the edible remainder is called the sunflower kernel.There are three types...

. In the case of sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...

 and corn "seeds", what is sown is the seed enclosed in a shell or hull, and the potato is a tuber.

Seed structure

A typical seed includes three basic parts: (1) an embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

, (2) a supply of nutrients for the embryo, and (3) a seed coat.

The embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 is an immature plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

 from which a new plant will grow under proper conditions. The embryo has one cotyledon
Cotyledon
A cotyledon , is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants...

 or seed leaf in monocotyledon
Monocotyledon
Monocotyledons, also known as monocots, are one of two major groups of flowering plants that are traditionally recognized, the other being dicotyledons, or dicots. Monocot seedlings typically have one cotyledon , in contrast to the two cotyledons typical of dicots...

s, two cotyledons in almost all dicotyledon
Dicotyledon
The dicotyledons, also known as dicots, are a group of flowering plants whose seed typically has two embryonic leaves or cotyledons. There are around 199,350 species within this group...

s and two or more in gymnosperms. The radicle
Radicle
In botany, the radicle is the first part of a seedling to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil...

 is the embryonic root. The plumule is the embryonic shoot. The embryonic stem above the point of attachment of the cotyledon(s) is the epicotyl
Epicotyl
In plant physiology, the epicotyl is the embryonic shoot above the cotyledons. In most plants the epicotyl will eventually develop into the leaves of the plant. In dicots, the hypocotyl is what appears to be the base stem under the spent withered cotyledons, and the shoot just above that is the...

. The embryonic stem below the point of attachment is the hypocotyl
Hypocotyl
The hypocotyl is the stem of a germinating seedling, found below the cotyledons and above the radicle .-Dicots:...

.

Within the seed, there usually is a store of nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s for the seedling
Seedling
thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...

 that will grow from the embryo. The form of the stored nutrition varies depending on the kind of plant. In angiosperms, the stored food begins as a tissue called the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...

, which is derived from the parent plant via double fertilization
Double fertilization
Double fertilization is a complex fertilization mechanism that has evolved in flowering plants . This process involves the joining of a female gametophyte with two male gametes . It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive structure of a flower...

. The usually triploid endosperm is rich in oil or starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...

 and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

. In gymnosperms, such as conifer
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...

s, the food storage tissue is part of the female gametophyte, a haploid tissue. In some species, the embryo is embedded in the endosperm or female gametophyte, which the seedling will use upon germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

. In others, the endosperm is absorbed by the embryo as the latter grows within the developing seed, and the cotyledons of the embryo become filled with this stored food. At maturity, seeds of these species have no endosperm and are termed exalbuminous seeds. Some exalbuminous seeds are bean
Bean
Bean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....

, pea
Pea
A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...

, oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

, walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

, squash, sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...

, and radish
Radish
The radish is an edible root vegetable of the Brassicaceae family that was domesticated in Europe, in pre-Roman times. They are grown and consumed throughout the world. Radishes have numerous varieties, varying in size, color and duration of required cultivation time...

. Seeds with an endosperm at maturity are termed albuminous seeds. Most monocots (e.g. grasses
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...

 and palms
Arecaceae
Arecaceae or Palmae , are a family of flowering plants, the only family in the monocot order Arecales. There are roughly 202 currently known genera with around 2600 species, most of which are restricted to tropical, subtropical, and warm temperate climates...

) and many dicots (e.g. brazil nut
Brazil Nut
The Brazil nut is a South American tree in the family Lecythidaceae, and also the name of the tree's commercially harvested edible seed.- Order :...

 and castor bean) have albuminous seeds. All gymnosperm seeds are albuminous.

The seed coat (or testa) develops from the tissue, the integument, originally surrounding the ovule. The seed coat in the mature seed can be a paper-thin layer (e.g. peanut
Peanut
The peanut, or groundnut , is a species in the legume or "bean" family , so it is not a nut. The peanut was probably first cultivated in the valleys of Peru. It is an annual herbaceous plant growing tall...

) or something more substantial (e.g. thick and hard in honey locust
Honey locust
The Honey locust, Gleditsia triacanthos, is a deciduous tree native to central North America. It is mostly found in the moist soil of river valleys ranging from southeastern South Dakota to New Orleans and central Texas, and as far east as eastern Massachusetts.-Description:Honey locusts, Gleditsia...

 and coconut
Coconut
The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...

). The seed coat helps protect the embryo from mechanical injury and from drying out.

In addition to the three basic seed parts, some seeds have an appendage on the seed coat such an aril
Aril
An aril is any specialized outgrowth from the funiculus that covers or is attached to the seed. It is sometimes applied to any appendage or thickening of the seed coat in flowering plants, such as the edible parts of the mangosteen and pomegranate fruit, the mace of the nutmeg seed, or the...

 (as in yew
Taxus
Taxus is a genus of yews, small coniferous trees or shrubs in the yew family Taxaceae. They are relatively slow-growing and can be very long-lived, and reach heights of 1-40 m, with trunk diameters of up to 4 m...

 and nutmeg
Nutmeg
The nutmeg tree is any of several species of trees in genus Myristica. The most important commercial species is Myristica fragrans, an evergreen tree indigenous to the Banda Islands in the Moluccas of Indonesia...

) or an elaiosome
Elaiosome
Elaiosomes are fleshy structures that are attached to the seeds of many plant species. The elaiosome is rich in lipids and proteins, and may be variously shaped. Many plants have elaiosomes to attract ants, which take the seed to their nest and feed the elaiosome to their larvae...

 (as in Corydalis
Corydalis
Corydalis is a genus of about 470 species of annual and perennial herbaceous plants in the fumewort family , native to the temperate Northern Hemisphere and the high mountains of tropical eastern Africa...

) or hairs (as in cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

). There may also be a scar on the seed coat, called the hilum
Hilum (biology)
In botany, the hilum is a scar or mark left on a seed coat by the former attachment to the ovary wall or to the funiculus...

; it is where the seed was attached to the ovary wall by the funiculus
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...

.

Kinds of seeds

Many structures commonly referred to as "seeds" are actually dry fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s. Sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...

 seeds are sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone
Drupe
In botany, a drupe is a fruit in which an outer fleshy part surrounds a shell of hardened endocarp with a seed inside. These fruits develop from a single carpel, and mostly from flowers with superior ovaries...

fruits (such as the peach
Peach
The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...

) have a hardened fruit layer ( the endocarp) fused to and surrounding the actual seed. Nuts
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

 are the one-seeded, hard shelled fruit, of some plants, with an indehiscent seed, such as an acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

 or hazelnut
Hazelnut
A hazelnut is the nut of the hazel and is also known as a cob nut or filbert nut according to species. A cob is roughly spherical to oval, about 15–25 mm long and 10–15 mm in diameter, with an outer fibrous husk surrounding a smooth shell. A filbert is more elongated, being about twice...

.

Seed production

Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms ("enclosed seeds") from the gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...

s ("naked seeds"). Angiosperm seeds are produced in a hard or fleshy structure called a fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 that encloses the seeds, hence the name. (Some fruits have layers of both hard and fleshy material). In gymnosperms, no special structure develops to enclose the seeds, which begin their development "naked" on the bracts of cones. However, the seeds do become covered by the cone
Conifer cone
A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...

 scales as they develop in some species of conifer.

Seed production in natural plant populations vary widely from year-to-year in response to weather variables, insects and diseases, and internal cycles within the plants themselves. Over a 20-year period, for example, forests composed of loblolly pine
Loblolly Pine
Pinus taeda is one of several pines native to the Southeastern United States, from central Texas east to Florida, and north to Delaware. It is particularly dominant in the eastern half of North Carolina, where there are huge expanses consisting solely of Loblolly Pine trees...

 and shortleaf pine
Shortleaf Pine
Pinus echinata is a species of pine native to the eastern United States from southern New York south to northern Florida, west to the extreme southeast of Kansas, and southwest to eastern Texas. The tree is variable in form, sometimes straight, sometimes crooked, with an irregular crown...

 produced from 0 to nearly 5 million sound pine seeds per hectare. Over this period, there were six bumper seeds, five poor seeds crops, and nine good seed crops, when evaluated in regard to producing adequate seedlings for natural forest reproduction.

Seed development

The seed, which is an embryo with two points of growth (one of which forms the stems the other the roots) is enclosed in a seed coat with some food reserves.
Angiosperm seeds consist of three genetically distinct constituents: (1) the embryo formed from the zygote, (2) the endosperm, which is normally triploid, (3) the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization
Double fertilization
Double fertilization is a complex fertilization mechanism that has evolved in flowering plants . This process involves the joining of a female gametophyte with two male gametes . It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive structure of a flower...

 and involves the fusion of the egg and sperm nuclei into a zygote. The second part of this process is the fusion of the polar nuclei with a second sperm cell nucleus, thus forming a primary endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...

. Right after fertilization, the zygote is mostly inactive but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food that the young plant will consume until the roots have developed after germination or it develops into a hard seed coat. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen
Tegmen
A tegmen designates the modified leathery front wing on an insect particularly in the orders Dermaptera , Orthoptera , Mantodea , Phasmatodea and Blattodea .-The nature of tegmina:The term tegmen refers to a miscellaneous and arbitrary group of organs...

 and the outer forms the testa. When the seed coat forms from only one layer it is also called the testa, though not all such testa are homologous from one species to the next.

In gymnosperms, the two sperm cells transferred from the pollen do not develop seed by double fertilization but one sperm nucleus unites with the egg nucleus and the other sperm is not used. Sometimes each sperm fertilizes an egg cell and one zygote is then aborted or absorbed during early development. The seed is composed of the embryo (the result of fertilization) and tissue from the mother plant, which also form a cone around the seed in coniferous plants like Pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...

 and Spruce
Spruce
A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...

.

The ovules after fertilization develop into the seeds; the main parts of the ovule are the funicle; which attaches the ovule to the placenta, the nucellus; the main region of the ovule were the embryo sac develops, the micropyle
Micropyle
A micropyle is small opening in the surface of an ovule, through which the pollen tube penetrates, often visible as a small pore in the ripe seed....

; A small pore or opening in the ovule where the pollen tube usually enters during the process of fertilization, and the chalaza
Chalaza
The chalaza is a structure inside bird and reptile eggs and plant ovules. It attaches or suspends the yolk or nucellus within the larger structure.-In animals:...

; the base of the ovule opposite the micropyle, where integument and nucellus are joined together.

The shape of the ovules as they develop often affects the finale shape of the seeds. Plants generally produce ovules of four shapes: the most common shape is called anatropous, with a curved shape. Orthotropous ovules are straight with all the parts of the ovule lined up in a long row producing an uncurved seed. Campylotropous ovules have a curved embryo sac often giving the seed a tight “c” shape. The last ovule shape is called amphitropous, where the ovule is partly inverted and turned back 90 degrees on its stalk or funicle.

In the majority of flowering plants, the zygote's first division is transversely oriented in regards to the long axis, and this establishes the polarity of the embryo. The upper or chalazal pole becomes the main area of growth of the embryo, while the lower or micropylar pole produces the stalk-like suspensor that attaches to the micropyle. The suspensor absorbs and manufacturers nutrients from the endosperm that are utilized during the embryos growth.

The embryo is composed of different parts; the epicotyle will grow into the shoot, the radicle grows into the primary root, the hypocotyl connects the epicotyle and the radicle, the cotyledons form the seed leaves, the testa or seed coat forms the outer covering of the seed. Monocotyledonous plants like corn, have other structures; instead of the hypocotyle-epicotyle, it has a coleoptile that forms the first leaf and connects to the coleorhiza that connects to the primary root and adventitious
Adventitious
Adventitious has various meanings in various disciplines and in general usage.Adventitious is from the Latin root advenire, meaning "to come or be superadded" and in correct English the meanings tend to have connections to accidental or casual occurrence...

 roots form from the sides. The seeds of corn are constructed with these structures; pericarp, scutellum (single large cotyledon) that absorbs nutrients from the endosperm, endosperm, plumule, radicle, coleoptile and coleorhiza - these last two structures are sheath-like and enclose the plumule and radicle, acting as a protective covering. The testa or seed coats of both monocots and dicots are often marked with patterns and textured markings, or have wings or tufts of hair.

Seed size and seed set

Seeds are very diverse in size. The dust-like orchid seeds are the smallest with about one million seeds per gram; they are often embryonic seeds with immature embryos and no significant energy reserves. Orchids and a few other groups of plants are myco-heterotrophs
Myco-heterotrophy
Myco-heterotrophy is a symbiotic relationship between certain kinds of plants and fungi, in which the plant gets all or part of its food from parasitism upon fungi rather than from photosynthesis. A myco-heterotroph is the parasitic plant partner in this relationship...

 which depend on mycorrhizal fungi for nutrition during germination and the early growth of the seedling. Some terrestrial Orchid seedlings, in fact, spend the first few years of their life deriving energy from the fungus and do not produce green leaves. At over 20 kg, the largest seed is the coco de mer
Coco de mer
The Coco de Mer , the sole member of the genus Lodoicea, is a palm endemic to the islands of Praslin and Curieuse in the Seychelles. It formerly also was found on St Pierre, Chauve-Souris and Ile Ronde in the Seychelles group, but has become extinct on these islands...

. Plants that produce smaller seeds can generate many more seeds per flower, while plants with larger seeds invest more resources into those seeds and normally produce fewer seeds. Small seeds are quicker to ripen and can be dispersed sooner, so fall blooming plants often have small seeds. Many annual plants produce great quantities of smaller seeds; this helps to ensure that at least a few will end in a favorable place for growth. Herbaceous perennials and woody plants often have larger seeds, they can produce seeds over many years, and larger seeds have more energy reserves for germination and seedling growth and produce larger, more established seedlings after germination.

Seed functions

Seeds serve several functions for the plants that produce them. Key among these functions are nourishment of the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

, dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...

 to a new location, and dormancy
Dormancy
Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...

 during unfavorable conditions. Seeds fundamentally are a means of reproduction and most seeds are the product of sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...

 which produces a remixing of genetic material and phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...

 variability that natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 acts on.

Embryo nourishment

Seeds protect and nourish the embryo or young plant. Seeds usually give a seedling a faster start than a sporeling from a spore, because of the larger food reserves in the seed and the multicellularity of the enclosed embryo.

Seed dispersal

Unlike animals, plants are limited in their ability to seek out favorable conditions for life and growth. As a result, plants have evolved many ways to disperse
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...

 their offspring by dispersing their seeds (see also vegetative reproduction
Vegetative reproduction
Vegetative reproduction is a form of asexual reproduction in plants. It is a process by which new individuals arise without production of seeds or spores...

). A seed must somehow "arrive" at a location and be there at a time favorable for germination and growth. When the fruits open and release their seeds in a regular way, it is called dehiscent, which is often distinctive for related groups of plants, these fruits include; Capsules, follicles, legumes, silicles and siliques. When fruits do not open and release their seeds in a regular fashion they are called indehiscent, which include the fruits achenes, caryopsis, nuts, samaras, and utricles.

Seed dispersal is seen most obviously in fruits; however many seeds aid in their own dispersal. Some kinds of seeds are dispersed while still inside a fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 or cone
Conifer cone
A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...

, which later opens or disintegrates to release the seeds. Other seeds are expelled or released from the fruit prior to dispersal. For example, milkweeds produce a fruit type, known as a follicle
Follicle (fruit)
In botany, a follicle is a dry unilocular many-seeded fruit formed from one carpel and dehiscing by the ventral suture in order to release seeds, such as in larkspur, magnolia, banksia, peony and milkweed....

, that splits open along one side to release the seeds. Iris
Iris (plant)
Iris is a genus of 260-300species of flowering plants with showy flowers. It takes its name from the Greek word for a rainbow, referring to the wide variety of flower colors found among the many species...

 capsules
Capsule (fruit)
In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...

 split into three "valves" to release their seeds.

By wind (anemochory)

  • Some seeds (e.g., pine
    Pine
    Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...

    ) have a wing that aids in wind dispersal.
  • The dustlike seeds of orchids are carried efficiently by the wind.
  • Some seeds, (e.g. milkweed, poplar
    Poplar
    Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....

    ) have hairs that aid in wind dispersal.


Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways:
  • Dandelion achenes have hairs.
  • Maple
    Maple
    Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...

     samaras have two wings.

By water (hydrochory)

  • Some plants, such as Mucuna
    Mucuna
    Mucuna is a genus of around 100 accepted species of climbing vines and shrubs of the family Fabaceae, found worldwide in the woodlands of tropical areas....

    and Dioclea
    Dioclea
    Dioclea is a genus of flowering plants in the pea family, Fabaceae, that is native to the Americas. The seeds of these legumes are buoyant drift seeds, and are dispersed by rivers....

    , produce buoyant seeds termed sea-beans or drift seeds because they float in rivers to the oceans and wash up on beaches.

By animals (zoochory)

  • Seeds (burr
    Burr (fruit)
    A bur is a seed or dry fruit in which the seeds bear hooks or teeth which attach themselves to fur or clothing of passing animals or people. The hooks or teeth can be irritants and very hard to get off of clothing, such as wool or cotton...

    s) with barbs or hooks (e.g. acaena
    Acaena
    Acaena is a genus of about one hundred species of perennial herbs and subshrubs in the Rosaceae, native mainly to the Southern Hemisphere, notably New Zealand, Australia and South America, but with a few species extending into the Northern Hemisphere, north to Hawaii and California Acaena is a...

    , burdock
    Burdock
    Burdock is any of a group of biennial thistles in the genus Arctium, family Asteraceae. Native to the Old World, several species have been widely introduced worldwide....

    , dock
    Rumex
    The docks and sorrels, genus Rumex L., are a genus of about 200 species of annual, biennial and perennial herbs in the buckwheat family Polygonaceae....

    ) which attach to animal fur or feathers, and then drop off later.
  • Seeds with a fleshy covering (e.g. apple
    Apple
    The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

    , cherry
    Cherry
    The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

    , juniper
    Juniper
    Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the...

    ) are eaten by animals (bird
    Bird
    Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

    s, mammal
    Mammal
    Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

    s, reptile
    Reptile
    Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

    s, fish
    Fish
    Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

    ) which then disperse these seeds in their droppings.
  • Seeds (nuts
    Nut (fruit)
    A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

    ) which are an attractive long-term storable food resource for animals (e.g. acorn
    Acorn
    The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...

    s, hazel
    Hazel
    The hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...

    nut, walnut
    Walnut
    Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

    ); the seeds are stored some distance from the parent plant, and some escape being eaten if the animal forgets them.


Myrmecochory
Myrmecochory
Myrmecochory is seed dispersal by ants, an ecologically significant ant-plant interaction with worldwide distribution. Myrmecochorous plants produce seeds with elaiosomes, a term encompassing various external appendages or "food bodies" rich in lipids, amino acid, or other nutrients that are...

is the dispersal of seeds by ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...

s. Foraging ants disperse seeds which have appendages called elaiosome
Elaiosome
Elaiosomes are fleshy structures that are attached to the seeds of many plant species. The elaiosome is rich in lipids and proteins, and may be variously shaped. Many plants have elaiosomes to attract ants, which take the seed to their nest and feed the elaiosome to their larvae...

s (e.g. bloodroot
Bloodroot
Bloodroot is a perennial, herbaceous flowering plant native to eastern North America from Nova Scotia, Canada southward to Florida, United States...

, trillium
Trillium
Trillium is a genus of about 40–50 species of spring ephemeral perennials, native to temperate regions of North America and Asia....

s, Acacia
Acacia
Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not...

s, and many species of Proteaceae
Proteaceae
Proteaceae is a family of flowering plants distributed in the Southern Hemisphere. The family comprises about 80 genera with about 1600 species. Together with the Platanaceae and Nelumbonaceae they make up the order Proteales. Well known genera include Protea, Banksia, Embothrium, Grevillea,...

). Elaiosomes are soft, fleshy structures that contain nutrients for animals that eat them. The ants carry such seeds back to their nest, where the elaiosomes are eaten. The remainder of the seed, which is hard and inedible to the ants, then germinates either within the nest or at a removal site where the seed has been discarded by the ants. This dispersal relationship is an example of mutualism, since the plants depend upon the ants to disperse seeds, while the ants depend upon the plants seeds for food. As a result, a drop in numbers of one partner can reduce success of the other. In South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, the Argentine ant
Argentine ant
The Argentine ant, Linepithema humile, is a dark ant native to northern Argentina, Uruguay, Paraguay, and southern Brazil...

 (Linepithema humile) has invaded
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 and displaced native species of ants. Unlike the native ant species, Argentine ants do not collect the seeds of Mimetes cucullatus or eat the elaiosomes. In areas where these ants have invaded, the numbers of Mimetes seedling
Seedling
thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...

s have dropped.

Seed dormancy

Seed dormancy has two main functions: the first is synchronizing germination with the optimal conditions for survival of the resulting seedling; the second is spreading germination of a batch of seeds over time so that a catastrophe after germination (e.g. late frosts, drought, herbivory) does not result in the death of all offspring of a plant (bet-hedging). Seed dormancy is defined as a seed failing to germinate under environmental conditions optimal for germination, normally when the environment is at a suitable temperature with proper soil moisture. This true dormancy or innate dormancy is therefore caused by conditions within the seed that prevent germination. Thus dormancy is a state of the seed, not of the environment. Induced dormancy, enforced dormancy or seed quiescence occurs when a seed fails to germinate because the external environmental conditions are inappropriate for germination, mostly in response to conditions being too dark or light, too cold or hot, or too dry.

Seed dormancy is not the same as seed persistence in the soil or on the plant, though even in scientific publications dormancy and persistence are often confused or used as synonyms.

Often seed dormancy is divided into four major categories: exogenous; endogenous; combinational; and secondary. A more recent system distinguishes five classes of dormancy:morphological, physiological, morphophysiological, physical and combinational dormancy.

Exogenous dormancy is caused by conditions outside the embryo including:
  • Physical dormancy or hard seed coats occurs when seeds are impermeable
    Permeability (fluid)
    Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.- Units :...

     to water. At dormancy break a specialized structure, the ‘water gap’, is disrupted in response to environmental cues, especially temperature, so that water can enter the seed and germination can occur. Plant families where physical dormancy occurs include Anacardiaceae
    Anacardiaceae
    Anacardiaceae are a family of flowering plants bearing fruits that are drupes and in some cases producing urushiol, an irritant. Anacardiaceae include numerous genera with several of economic importance. Notable plants in this family include cashew , mango, poison ivy, sumac, smoke tree, and marula...

    , Cannaceae, Convulvulaceae, Fabaceae
    Fabaceae
    The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...

     and Malvaceae
    Malvaceae
    Malvaceae, or the mallow family, is a family of flowering plants containing over 200 genera with close to 2,300 species. Judd & al. Well known members of this family include okra, jute and cacao...

    .
  • Chemical dormancy considers species that lack physiological dormancy, but where a chemical prevents germination. This chemical can be leached out of the seed by rainwater or snow melt or be deactivated somehow. Leaching of chemical inhibitors from the seed by rain water is often cited as an important cause of dormancy release in seeds of desert plants, however little evidence exists to support this claim.


Endogenous dormancy is caused by conditions within the embryo itself, including:
  • Morphological dormancy where germination is prevented due to morphological characteristics of the embryo. In some species the embryo is just a mass of cells when seeds are dispersed, it is not differentiated. Before germination can take place both differentiation and growth of the embryo have to occur. In other species the embryo is differentiated but not fully grown (underdeveloped) at dispersal and embryo growth up to a species specific length is required before germination can occur. Examples of plant families where morphological dormancy occurs are Apiaceae
    Apiaceae
    The Apiaceae , commonly known as carrot or parsley family, is a group of mostly aromatic plants with hollow stems. The family is large, with more than 3,700 species spread across 434 genera, it is the sixteenth largest family of flowering plants...

    , Cycadaceae, Liliaceae
    Liliaceae
    The Liliaceae, or the lily family, is a family of monocotyledons in the order Liliales. Plants in this family have linear leaves, mostly with parallel veins but with several having net venation , and flower arranged in threes. Several have bulbs, while others have rhizomes...

    , Magnoliaceae
    Magnoliaceae
    The Magnoliaceae, or Magnolia Family, is a flowering plant family in the order Magnoliales. It consists of two subfamilies:*Magnolioideae, of which Magnolia is the most well-known genus....

     and Ranunculaceae
    Ranunculaceae
    Ranunculaceae are a family of about 1700 species of flowering plants in about 60 genera, distributed worldwide....

    .
  • Morphophysiological dormancy seeds with underdeveloped embryos, and which in addition have physiological components to dormancy. These seeds therefore require a dormancy-breaking treatments as well as a period of time to develop fully grown embryos. Plant families where morphophysiological dormancy occurs include Apiaceae
    Apiaceae
    The Apiaceae , commonly known as carrot or parsley family, is a group of mostly aromatic plants with hollow stems. The family is large, with more than 3,700 species spread across 434 genera, it is the sixteenth largest family of flowering plants...

    , Aquifoliaceae, Liliaceae
    Liliaceae
    The Liliaceae, or the lily family, is a family of monocotyledons in the order Liliales. Plants in this family have linear leaves, mostly with parallel veins but with several having net venation , and flower arranged in threes. Several have bulbs, while others have rhizomes...

    , Magnoliaceae
    Magnoliaceae
    The Magnoliaceae, or Magnolia Family, is a flowering plant family in the order Magnoliales. It consists of two subfamilies:*Magnolioideae, of which Magnolia is the most well-known genus....

    , Papaveraceae
    Papaveraceae
    Papaveraceae, informally known as the poppy family, are an economically important family of 44 genera and approximately 770 species of flowering plants in the order Ranunculales. The family is cosmopolitan, occurring in temperate and subtropical climates, but almost unknown in the tropics...

     and Ranunculaceae
    Ranunculaceae
    Ranunculaceae are a family of about 1700 species of flowering plants in about 60 genera, distributed worldwide....

    . Some plants with morphophysiological dormancy like Asarum
    Asarum
    Asarum is a genus of plants in the birthwort family Aristolochiaceae, commonly known as Wild ginger.- Description :...

     or Trillium
    Trillium
    Trillium is a genus of about 40–50 species of spring ephemeral perennials, native to temperate regions of North America and Asia....

     species have multiple types of dormancy, one affects radicle (root) growth while the other affects plumule (shoot) growth. The terms "double dormancy" and "2-year seeds" are used for species whose seeds need two years to complete germination or at least two winters and one summer. Dormancy of the radicle (seedling root)is broken during the first winter after dispersal while dormancy of the shoot bud is broken during the second winter.
  • Physiological dormancy means that the embryo can, due to physiological causes, not generate enough power to break through the seed coat, endosperm or other covering structures. Dormancy is typically broken at cool wet, warm wet or warm dry conditions. Abscisic acid
    Abscisic acid
    Abscisic acid , also known as abscisin II and dormin, is a plant hormone. ABA functions in many plant developmental processes, including bud dormancy. It is degraded by the enzyme -abscisic acid 8'-hydroxylase.-Function:...

     is usually the growth inhibitor in seeds and its production can be affected by light.
    • Drying; some plants including a number of grasses and those from seasonally arid regions need a period of drying before they will germinate. The seeds are released but need to have a lower moisture content before germination can begin. If the seeds remain moist after dispersal, germination can be delayed for many months or even years. Many herbaceous plants from temperate climate zones have physiological dormancy that disappears with drying of the seeds. Other species will germinate after dispersal only under very narrow temperature ranges, but as the seeds dry they are able to germinate over a wider temperature range.

  • Combinational dormancy In seeds with combinational dormancy the seed or fruit coat is impermeable to water and the embryo has physiological dormancy. Depending on the species physical dormancy can be broken before or after physiological dormancy is broken.

  • Secondary dormancy* is caused by conditions after the seed has been dispersed and occurs in some seeds when non-dormant seed is exposed to conditions that are not favorable to germination, very often high temperatures. The mechanisms of secondary dormancy are not yet fully understood but might involve the loss of sensitivity in receptors in the plasma membrane.


The following types of seed dormancy do not involve seed dormancy strictly spoken as lack of germination is prevented by the environment not by characteristics of the seed itself (see Germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

):
  • Photodormancy or light sensitivity affects germination of some seeds. These photoblastic seeds need a period of darkness or light to germinate. In species with thin seed coats, light
    Light
    Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

     may be able to penetrate into the dormant embryo. The presence of light or the absence of light may trigger the germination process, inhibiting germination in some seeds buried too deeply or in others not buried in the soil.
  • Thermodormancy is seed sensitivity to heat or cold. Some seeds including cocklebur and amaranth germinate only at high temperatures (30C or 86F) many plants that have seed that germinate in early to mid summer have thermodormancy and germinate only when the soil temperature is warm. Other seeds need cool soils to germinate, while others like celery are inhibited when soil temperatures are too warm. Often thermodormancy requirements disappear as the seed ages or dries.


Not all seeds undergo a period of dormancy. Seeds of some mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...

s are viviparous, they begin to germinate while still attached to the parent. The large, heavy root allows the seed to penetrate into the ground when it falls. Many garden plants have seeds that will germinate readily as soon as they have water and are warm enough, though their wild ancestors may have had dormancy, these cultivated plants lack seed dormancy. After many generations of selective pressure by plant breeders and gardeners dormancy has been selected out.

For annuals
Annual plant
An annual plant is a plant that usually germinates, flowers, and dies in a year or season. True annuals will only live longer than a year if they are prevented from setting seed...

, seeds are a way for the species to survive dry or cold seasons. Ephemeral plants are usually annuals that can go from seed to seed in as few as six weeks.

Seed germination

Seed germination is a process by which a seed embryo develops into a seedling. It involves the reactivation of the metabolic pathways that lead to growth and the emergence of the radicle or seed root and plumule or shoot. The emergence of the seedling above the soil surface is the next phase of the plant's growth and is called seedling establishment.

Three fundamental conditions must exist before germination can occur. (1) The embryo must be alive, called seed viability. (2) Any dormancy requirements that prevent germination must be overcome. (3) The proper environmental conditions must exist for germination.

Seed viability is the ability of the embryo to germinate and is affected by a number of different conditions. Some plants do not produce seeds that have functional complete embryos or the seed may have no embryo at all, often called empty seeds. Predators and pathogens can damage or kill the seed while it is still in the fruit or after it is dispersed. Environmental conditions like flooding or heat can kill the seed before or during germination. The age of the seed affects its health and germination ability: since the seed has a living embryo, over time cells die and cannot be replaced. Some seeds can live for a long time before germination, while others can only survive for a short period after dispersal before they die.

Seed vigor is a measure of the quality of seed, and involves the viability of the seed, the germination percentage, germination rate and the strength of the seedlings produced.

The germination percentage is simply the proportion of seeds that germinate from all seeds subject to the right conditions for growth. The germination rate is the length of time it takes for the seeds to germinate. Germination percentages and rates are affected by seed viability, dormancy and environmental effects that impact on the seed and seedling. In agriculture and horticulture quality seeds have high viability, measured by germination percentage plus the rate of germination. This is given as a percent of germination over a certain amount of time, 90% germination in 20 days, for example. 'Dormancy' is covered above; many plants produce seeds with varying degrees of dormancy, and different seeds from the same fruit can have different degrees of dormancy. It's possible to have seeds with no dormancy if they are dispersed right away and do not dry (if the seeds dry they go into physiological dormancy). There is great variation amongst plants and a dormant seed is still a viable seed even though the germination rate might be very low.

Environmental conditions effecting seed germination include; water, oxygen, temperature and light.

Three distinct phases of seed germination occur: water imbibition; lag phase; and radicle
Radicle
In botany, the radicle is the first part of a seedling to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil...

 emergence.

In order for the seed coat to split, the embryo must imbibe (soak up water), which causes it to swell, splitting the seed coat. However, the nature of the seed coat determines how rapidly water can penetrate and subsequently initiate germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

. The rate of imbibition is dependent on the permeability of the seed coat, amount of water in the environment and the area of contact the seed has to the source of water. For some seeds, imbibing too much water too quickly can kill the seed. For some seeds, once water is imbibed the germination process cannot be stopped, and drying then becomes fatal. Other seeds can imbibe and lose water a few times without causing ill effects, but drying can cause secondary dormancy.

Inducing germination

A number of different strategies are used by gardeners and horticulturists to break seed dormancy
Seed dormancy
Seed dormancy is a condition of plant seeds that prevents germination when the seeds are under optimal environmental conditions for germination. Living, non dormant seeds germinate when soil temperatures and moisture conditions are suited for cellular processes and division; dormant seeds do...

.

Scarification which allows water and gases to penetrate into the seed, include methods that physically break the hard seed coats or soften them by chemicals. Means of scarification include soaking in hot water or poking holes in the seed with a pin or rubbing them on sandpaper or cracking with a press or hammer. Soaking the seeds in solvents or acids is also effective for many seeds. Sometimes fruits are harvested while the seeds are still immature and the seed coat is not fully developed and sown right away before the seed coat become impermeable. Under natural conditions seed coats are worn down by rodents chewing on the seed, the seeds rubbing against rocks (seeds are moved by the wind or water currents), by undergoing freezing and thawing of surface water, or passing through an animal's digestive tract. In the latter case, the seed coat protects the seed from digestion
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....

, while often weakening the seed coat such that the embryo is ready to sprout when it gets deposited (along with a bit of fertilizer) far from the parent plant. Microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

s are often effective in breaking down hard seed coats and are sometimes used by people as a treatment, the seeds are stored in a moist warm sandy medium for several months under non-sterile conditions.

Stratification also called moist-chilling is a method to break down physiological dormancy and involves the addition of moisture to the seeds so they imbibe water and then the seeds are subject to a period of moist chilling to after-ripen the embryo. Sowing outside in late summer and fall and allowing to overwinter outside under cool conditions is an effective way to stratify seeds, some seeds respond more favorably to periods of oscillating temperatures which are part of the natural environment.

Leaching or the soaking in water removes chemical inhibitors in some seeds that prevent germination. Rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

 and melting snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

 naturally accomplish this task. For seeds planted in gardens, running water is best - if soaked in a container, 12 to 24 hours of soaking is sufficient. Soaking longer, especially in stagnant water that is not changed, can result in oxygen starvation and seed death. Seeds with hard seed coats can be soaked in hot water to break open the impermeable cell layers that prevent water intake.

Other methods used to assist in the germination of seeds that have dormancy include prechilling, predrying, daily alternation of temperature, light exposure, potassium nitrate, the use of plant growth regulators like gibberellins, cytokinins, ethylene, thiourea, sodium hypochlorite plus others. Some seeds germinate best after a fire, for some seeds fire cracks hard seed coats while in other seeds chemical dormancy is broken in reaction to the presence of smoke, liquid smoke is often used by gardeners to assist in the germination of these species.

Origin and evolution

The origin of seed plants is a problem that still remains unsolved. However, more and more data tends to place this origin in the middle Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

. The description in 2004 of the proto-seed Runcaria heinzelinii in the Givetian of Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

 is an indication of that ancient origin of seed-plants. As with modern ferns, most land plants before this time reproduced by sending spores into the air, that would land and become whole new plants.

The first "true" seeds are described from the upper Devonian, which is probably the theater of their true first evolutionary radiation. The seed plants progressively became one of the major elements of nearly all ecosystems.

Economic importance

Edible seeds

Many seeds are edible and the majority of human calories comes from seeds , especially from cereal
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...

s, legumes and nut
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...

s. Seeds also provide most cooking oil
Cooking oil
Cooking oil is purified fat of plant origin, which is usually liquid at room temperature ....

s, many beverages and spice
Spice
A spice is a dried seed, fruit, root, bark, or vegetative substance used in nutritionally insignificant quantities as a food additive for flavor, color, or as a preservative that kills harmful bacteria or prevents their growth. It may be used to flavour a dish or to hide other flavours...

s and some important food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

s. In different seeds the seed embryo or the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...

 dominates and provides most of the nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s. The storage protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s of the embryo and endosperm differ in their amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 content and physical properties. For example the gluten
Gluten
Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...

 of wheat, important in providing the elastic
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....

 property to bread dough
Dough
Dough is a paste made out of any cereals or leguminous crops by mixing flour with a small amount of water and/or other liquid. This process is a precursor to making a wide variety of foodstuffs, particularly breads and bread-based items , flatbreads, noodles, pastry, and similar items)...

 is strictly an endosperm protein.

Seeds are used to propagate many crops such as cereals, legumes, forest trees
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...

, turfgrasses and pasture
Pasture
Pasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...

 grasses. Particularly in developing countries, a major constraint faced is the inadequacy of the marketing channels to get the seed to poor farmers. Thus the use of farmer-retained seed remains quite common.

Seeds are also eaten by animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, and are fed to livestock
Livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

. Many seeds are used as birdseed.

Poison and food safety

While some seeds are edible, others are harmful, poisonous or deadly. Plants and seeds often contain chemical compounds to discourage herbivores and seed predators
Seed predation
Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores feed on the seeds of plants as a main or exclusive food source, in many cases leaving the seeds damaged and not viable...

. In some cases, these compounds simply taste bad (such as in mustard
Mustard (condiment)
Mustard is a condiment made from the seeds of a mustard plant...

), but other compounds are toxic or break down into toxic compounds within the digestive system. Children, being smaller than adults, are more susceptible to poisoning by plants and seeds.

A deadly poison, ricin
Ricin
Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of salt can kill an adult. The LD50 of ricin is around 22 micrograms per kilogram Ricin , from the castor oil plant Ricinus communis, is a highly toxic, naturally...

, comes from seeds of the castor bean. Reported lethal doses are anywhere from two to eight seeds,
though only a few deaths have been reported when castor beans have been ingested by animals.

In addition, seeds containing amygdalin
Amygdalin
Amygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...

apple
Apple
The apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...

, apricot
Apricot
The apricot, Prunus armeniaca, is a species of Prunus, classified with the plum in the subgenus Prunus. The native range is somewhat uncertain due to its extensive prehistoric cultivation.- Description :...

, bitter almond, peach
Peach
The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...

, plum
Plum
A plum or gage is a stone fruit tree in the genus Prunus, subgenus Prunus. The subgenus is distinguished from other subgenera in the shoots having a terminal bud and solitary side buds , the flowers in groups of one to five together on short stems, and the fruit having a groove running down one...

, cherry
Cherry
The cherry is the fruit of many plants of the genus Prunus, and is a fleshy stone fruit. The cherry fruits of commerce are usually obtained from a limited number of species, including especially cultivars of the wild cherry, Prunus avium....

, quince
Quince
The quince , or Cydonia oblonga, is the sole member of the genus Cydonia and native to warm-temperate southwest Asia in the Caucasus region...

, and others—when consumed in sufficient amounts, may cause Cyanide poisoning
Cyanide poisoning
Cyanide poisoning occurs when a living organism is exposed to a compound that produces cyanide ions when dissolved in water. Common poisonous cyanide compounds include hydrogen cyanide gas and the crystalline solids potassium cyanide and sodium cyanide...

.
Other seeds that contain poisons include annona
Annona
Annona is a genus of flowering plants in the pawpaw/sugar apple family, Annonaceae. It is the second largest genus in the family after Guatteria, containing approximately 110 species of mostly neotropical and afrotropical trees and shrubs....

, cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

, custard apple
Custard apple
Custard apple, a common name, can refer to:*Custard-apple, also called bull's heart, the fruit of the tree Annona reticulata.*The custard-apple tree itself, Annona reticulataThe term may also refer to:...

, datura
Datura
Datura is a genus of nine species of vespertine flowering plants belonging to the family Solanaceae. Its precise and natural distribution is uncertain, owing to its extensive cultivation and naturalization throughout the temperate and tropical regions of the globe...

, uncooked durian
Durian
The durian is the fruit of several tree species belonging to the genus Durio and the Malvaceae family . Widely known and revered in southeast Asia as the "king of fruits", the durian is distinctive for its large size, unique odour, and formidable thorn-covered husk...

, golden chain
Golden Chain
There are multiple uses for the term Golden Chain:*Golden chain is the common name for the genus Laburnum, and related species of small trees with decorative yellow flowers.*Golden Chain , an alleged group of al Qaeda's wealthy sponsors...

, horse-chestnut, larkspur
Delphinium
Delphinium is a genus of about 300 species of perennial flowering plants in the buttercup family Ranunculaceae, native throughout the Northern Hemisphere and also on the high mountains of tropical Africa. The common name, larkspur, is shared with the closely related genus Consolida...

, locoweed
Locoweed
Locoweed is a common name in North America for any plant that produces swainsonine, a phytotoxin harmful to livestock. Worldwide, swainsonine is produced by a small number of species, most in three genera of the flowering plant family Fabaceae: Oxytropis and Astragalus in North America, and...

, lychee
Lychee
The lychee is the sole member of the genus Litchi in the soapberry family, Sapindaceae. It is a tropical and subtropical fruit tree native to Southern China and Southeast Asia, and now cultivated in many parts of the world...

, nectarine, rambutan
Rambutan
The rambutan is a medium-sized tropical tree in the family Sapindaceae, and the fruit of this tree. It is native to Vietnam, Indonesia, the Philippines, Sri Lanka, Malaysia, and elsewhere in Southeast Asia, although its precise natural distribution is unknown. It is closely related to several...

, rosary pea, sour sop, sugar apple, wisteria
Wisteria
Wisteria is a genus of flowering plants in the pea family, Fabaceae, that includes ten species of woody climbing vines native to the eastern United States and to China, Korea, and Japan. Aquarists refer to the species Hygrophila difformis, in the family Acanthaceae, as Water Wisteria...

, and yew
Taxus
Taxus is a genus of yews, small coniferous trees or shrubs in the yew family Taxaceae. They are relatively slow-growing and can be very long-lived, and reach heights of 1-40 m, with trunk diameters of up to 4 m...

. The seeds of the strychnine tree
Strychnine tree
The Strychnine tree also known as Nux vomica, Poison Nut, Semen strychnos and Quaker Buttons, is a deciduous tree native to India, southeast Asia, a member of family Loganiaceae. It is a medium-size tree growing in open habitats...

 are also poisonous, containing the poison strychnine
Strychnine
Strychnine is a highly toxic , colorless crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine causes muscular convulsions and eventually death through asphyxia or sheer exhaustion...

.

The seeds of many legumes, including the common bean (Phaseolus vulgaris), contain proteins called lectins which can cause gastric distress if the beans are eaten without cooking
Cooking
Cooking is the process of preparing food by use of heat. Cooking techniques and ingredients vary widely across the world, reflecting unique environmental, economic, and cultural traditions. Cooks themselves also vary widely in skill and training...

. The common bean and many others, including the soybean
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...

, also contain trypsin inhibitors which interfere with the action of the digestive enzyme trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...

. Normal cooking processes degrade lectins and trypsin inhibitors to harmless forms.

Please see the category plant toxins for further relevant articles.

Other uses

Cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

 fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....

 grows attached to cotton plant
Gossypium
Gossypium is the cotton genus. It belongs to the tribe Gossypieae, in the mallow family, Malvaceae, native to the tropical and subtropical regions from both the Old and New World. The genus Gossypium comprises around 50 species , making it the largest in species number in the tribe Gosssypioieae....

 seeds. Other seed fibers are from kapok
Kapok
Ceiba pentandra is a tropical tree of the order Malvales and the family Malvaceae , native to Mexico, Central America and the Caribbean, northern South America, and to tropical west Africa...

 and milkweed.

Many important nonfood oils are extracted from seeds. Linseed oil
Linseed oil
Linseed oil, also known as flaxseed oil, is a clear to yellowish oil obtained from the dried ripe seeds of the flax plant . The oil is obtained by cold pressing, sometimes followed by solvent extraction...

 is used in paints. Oil from jojoba
Jojoba
Jojoba, pronounced , is a shrub native to the Sonoran and Mojave deserts of Arizona, California, and Mexico. It is the sole species of the family Simmondsiaceae, placed in the order Caryophyllales. It is also known as goat nut, deer nut, pignut, wild hazel, quinine nut, coffeeberry, and gray box...

 and crambe
Crambe
Crambe is a genus of Brassicaceae native to Europe, southwest and central Asia and eastern Africa. It includes among its species seakale , grown as a leaf vegetable, Crambe cordifolia which is grown as an herbaceous border perennial, and Crambe abyssinica, which is grown for an oil from the seeds...

 are similar to whale oil
Whale oil
Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...

.

Seeds are the source of some medicines including castor oil
Castor oil
Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is and its density is 961 kg/m3...

, tea tree oil
Tea tree oil
Tea tree oil, or melaleuca oil, is a pale yellow colour to nearly clear essential oil with a fresh camphoraceous odor. It is taken from the leaves of the Melaleuca alternifolia, which is native to the northeast coast of New South Wales, Australia...

 and the discredited cancer drug, Laetrile
Amygdalin
Amygdalin , C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet...

.

Many seeds have been used as bead
Bead
A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...

s in necklaces and rosaries including Job's tears
Job's Tears
Job's Tears , Coixseed, Tear Grass, adlay, or adlai, is a tall grain-bearing tropical plant of the family Poaceae native to Southeast Asia but elsewhere cultivated in gardens as an annual. It has been naturalized in the southern United States and the New World tropics...

, Chinaberry, rosary pea, and castor bean. However, the latter three are also poisonous.

Other seed uses include:
  • Seeds once used as weights for balance
    Weighing scale
    A weighing scale is a measuring instrument for determining the weight or mass of an object. A spring scale measures weight by the distance a spring deflects under its load...

    s.
  • Seeds used as toys by children, such as for the game Conkers.
  • Resin from Clusia
    Clusia
    Clusia is the type genus of the family Clusiaceae. Comprising 140-150 species, it is native to tropical and subtropical America. Its species are shrubs, vines and small to medium-size trees up to 20 m tall, with evergreen foliage...

     rosea
    seeds used to caulk boats.
  • Nematicide
    Nematicide
    A nematicide is a type of chemical pesticide used to kill parasitic nematodes.One common nematicide is obtained from neem cake, the residue obtained after cold-pressing the fruit and kernels of the neem tree. Known by several names in the world, the tree was first cultivated in India in ancient...

     from milkweed seeds.
  • Cottonseed meal
    Cottonseed meal
    Cottonseed meal is the byproduct remaining after cotton is ginned and the seeds crushed and the oil extracted. The remaining meal is usually used for animal feed and in organic fertilizers. However, the meal can be fed only to adult ruminants because it contains a compound called gossypol...

     used as animal feed and fertilizer
    Fertilizer
    Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

    .

Seed records

  • The oldest viable
    Oldest viable seed
    -Carbon dated:*The oldest carbon-14-dated seed that has grown into a viable plant was a Judean date palm seed about 2,000 years old, recovered from excavations at Herod the Great's palace on Masada in Israel. It was germinated in 2005...

     carbon-14
    Carbon-14
    Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...

    -dated seed that has grown into a plant was a Judean date palm
    Judean date palm
    The Judean date palm is a cultivar of the date palm .Prized for its beauty, shade, and medicinal properties, the cultivar was thought to have become extinct sometime around AD 150. However, in 2005, a preserved 2,000-year-old seed sprouted. It is the oldest known human-assisted germination of a seed...

     seed about 2,000 years old, recovered from excavations at Herod the Great
    Herod the Great
    Herod , also known as Herod the Great , was a Roman client king of Judea. His epithet of "the Great" is widely disputed as he is described as "a madman who murdered his own family and a great many rabbis." He is also known for his colossal building projects in Jerusalem and elsewhere, including his...

    's palace on Masada
    Masada
    Masada is the name for a site of ancient palaces and fortifications in the South District of Israel, on top of an isolated rock plateau, or horst, on the eastern edge of the Judean Desert, overlooking the Dead Sea. Masada is best known for the violence that occurred there in the first century CE...

     in Israel
    Israel
    The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

    . It was germinated in 2005.

  • The largest seed is produced by the coco de mer
    Coco de mer
    The Coco de Mer , the sole member of the genus Lodoicea, is a palm endemic to the islands of Praslin and Curieuse in the Seychelles. It formerly also was found on St Pierre, Chauve-Souris and Ile Ronde in the Seychelles group, but has become extinct on these islands...

    , or "double coconut palm", Lodoicea maldivica. The entire fruit
    Fruit
    In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

     may weigh up to 23 kilograms (50 pounds) and usually contains a single seed.

  • The earliest fossil
    Fossil
    Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

     seeds are around 365 million years old from the Late
    Famennian
    The Famennian is one of two faunal stages in the Late Devonian epoch. It lasted from 374.5 ± 2.6 million years ago to 359.2 ± 2.5 million years ago. It was preceded by the Frasnian stage and followed by the Tournaisian stage and is named after Famenne, a natural region in southern Belgium.It was...

     Devonian
    Devonian
    The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

     of West Virginia
    West Virginia
    West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...

    . The seeds are preserved immature ovule
    Ovule
    Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...

    s of the plant
    Plant
    Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

     Elkinsia polymorpha.

See also

  • Brownbagging
    Brownbagging (agriculture)
    Brownbagging or brown-bagging is the agricultural practice of planting, or especially selling, seed saved from the farmers own harvest, as opposed to buying new seed from a seed company....

  • Biological dispersal
    Biological dispersal
    Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...

  • Germination
    Germination
    Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

  • List of edible seeds
  • List of world's largest seeds
  • Recalcitrant seed
    Recalcitrant seed
    Recalcitrant seeds are seeds that do not survive drying and freezing during ex-situ conservation. Moreover, these seeds cannot resist the effects of drying or temperatures less than 10° C; thus, they cannot be stored for long periods like orthodox seeds because they can lose their viability...

  • Seed company
    Seed company
    Seed companies produce and sell seeds for flowers, fruit and vegetables to theamateur gardener. The production of seed is a multi billion dollar business, which usesgrowing facilities and growing locations world wide. While most seed is produced by large...

  • Seed enhancement
    Seed enhancement
    Seed enhancement is a range of treatments of seeds that improves their performance after harvesting and conditioned, but before they are sown. They include priming, steeping, hardening, pregermination, pelleting, encrusting, film-coating, tagging and others, but excludes treatments for control of...

  • Seed orchard
    Seed orchard
    A seed orchard is an intensively-managed plantation of specifically arranged trees for the mass production of genetically improved seeds to create plants, or seeds for the establishment of new forests.-General:...

  • Seed paper
    Seed paper
    Seed paper is a type of handmade paper that includes any number of different plant seeds. Seed paper is attractive, versatile, and easily recyclable. One of the novel features of seed paper is that it is a medium for viable plant seeds...

  • Seed predation
    Seed predation
    Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores feed on the seeds of plants as a main or exclusive food source, in many cases leaving the seeds damaged and not viable...

  • Seed saving
    Seed saving
    In agriculture and gardening, seed saving is the practice of saving seeds or other reproductive material from open-pollinated vegetables, grain, herbs, and flowers for use from year to year for annuals and nuts, tree fruits, and berries for perennials and trees...

  • Seed testing
    Seed testing
    Seed testing is performed in dedicated laboratories by trained and usually certified analysts. The tests are designed to evaluate the quality of the seed lot being sold. Several tests are done:*Germination test: Reports the percentage of seed that germinated...

  • Seedbed
    Seedbed
    A seedbed or seedling bed is the local soil environment in which seeds are planted. Often it comprises not only the soil but also a specially prepared cold frame, hotbed or raised bed used to grow the seedlings in a controlled environment into larger young plants before transplanting them into a...

  • Seedling
    Seedling
    thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...

  • Soil seed bank
    Soil Seed Bank
    The soil seed bank refers to the natural storage of seeds, often dormant, within the soil of most ecosystems. The study of soil seed banks started in 1859 when Charles Darwin observed the emergence of seedlings using soil samples from the bottom of a lake. The first scientific paper on the subject...

  • Stratification
    Stratification (botany)
    In horticulture, stratification is the process of pretreating seeds to simulate natural winter conditions that a seed must endure before germination. Many seed species undergo an embryonic dormancy phase, and generally will not sprout until this dormancy is broken...


External links

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