Seed

A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm plants.

Seeds are the product of the ripened ovule, after fertilization by pollen and some growth within the mother plant. The embryo is developed from the zygote and the seed coat from the integuments of the ovule.

Seeds have been an important development in the reproduction and success of gymnosperm and angiosperm plants, relative to more primitive plants such as ferns, mosses and liverworts, which do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates.

The term "seed" also has a general meaning that antedates the above – anything that can be sown, e.g. "seed" potatoes, "seeds" of corn or sunflower "seeds". In the case of sunflower and corn "seeds", what is sown is the seed enclosed in a shell or husk, whereas the potato is a tuber.

Many structures commonly referred to as "seeds" are actually dry fruits. Plants producing berries are called baccate. Sunflower seeds are sometimes 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 fruits (such as the peach) have a hardened fruit layer (the endocarp) fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut.

Разнообразие семян
Seeds of different plants (left to right, not to scale). First row: Poppy, Red pepper, Strawberry, Apple tree, Blackberry, Rice, Carum. Second row: Mustard, Eggplant, Physalis, grapes, raspberries, red rice, Patchouli. Third row: Figs, Lycium barbarum, Beets, Blueberries, Golden Kiwifruit, Rosehip, Basil. Fourth row: Pink pepper, Tomato, Radish, Carrot, Matthiola, Dill, Coriander. Fifth row: Black pepper, White cabbage, Napa cabbage, Seabuckthorn, Parsley, Dandelion, Capsella bursa-pastoris. Sixth row: Cauliflower, Radish, Kiwifruit, Grenadilla, Passion fruit, Melissa, Tagetes erecta.

Seed production

Seeds are produced in several related groups of plants, and their manner of production distinguishes the angiosperms ("enclosed seeds") from the gymnosperms ("naked seeds"). Angiosperm seeds are produced in a hard or fleshy structure called a fruit that encloses the seeds for protection in order to secure healthy growth. 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 scales as they develop in some species of conifer.

Seed production in natural plant populations varies 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 and shortleaf pine produced from 0 to nearly 5 million sound pine seeds per hectare.[1] Over this period, there were six bumper, five poor, and nine good seed crops, when evaluated for production of adequate seedlings for natural forest reproduction.

Development

Seed Development Cycle
Stages of seed development:
Key: 1. Endosperm 2. Zygote 3. Embryo 4. Suspensor 5. Cotyledons 6. Shoot Apical Meristem 7. Root Apical Meristem 8. Radicle 9. Hypocotyl 10. Epicotyl 11. Seed Coat

Angiosperm (flowering plants) 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, which involves the fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote. Right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food the young plant will consume until the roots have developed after germination.

Ovule

Ovule-Gymno-Angio-en
Plant ovules: Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right

After fertilization the ovules develop into the seeds. The ovule consists of a number of components:

  • The funicle (funiculus, funiculi) or seed stalk which attaches the ovule to the placenta and hence ovary or fruit wall, at the pericarp.
  • The nucellus, the remnant of the megasporangium and main region of the ovule where the megagametophyte develops.
  • The micropyle, a small pore or opening in the apex of the integument of the ovule where the pollen tube usually enters during the process of fertilization.
  • The chalaza, the base of the ovule opposite the micropyle, where integument and nucellus are joined together.[2]

The shape of the ovules as they develop often affects the final 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 megagametophyte 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 (the funicle or funiculus).

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 manufactures nutrients from the endosperm that are used during the embryo's growth.[3]

Embryo

Ginkgo embryo and gametophyte
The inside of a Ginkgo seed, showing a well-developed embryo, nutritive tissue (megagametophyte), and a bit of the surrounding seed coat

The main components of the embryo are:

  • The cotyledons, the seed leaves, attached to the embryonic axis. There may be one (Monocotyledons), or two (Dicotyledons). The cotyledons are also the source of nutrients in the non-endospermic dicotyledons, in which case they replace the endosperm, and are thick and leathery. In endospermic seeds the cotyledons are thin and papery. Dicotyledons have the point of attachment opposite one another on the axis.
  • The epicotyl, the embryonic axis above the point of attachment of the cotyledon(s).
  • The plumule, the tip of the epicotyl, and has a feathery appearance due to the presence of young leaf primordia at the apex, and will become the shoot upon germination.
  • The hypocotyl, the embryonic axis below the point of attachment of the cotyledon(s), connecting the epicotyl and the radicle, being the stem-root transition zone.
  • The radicle, the basal tip of the hypocotyl, grows into the primary root.

Monocotyledonous plants have two additional structures in the form of sheaths. The plumule is covered with a coleoptile that forms the first leaf while the radicle is covered with a coleorhiza that connects to the primary root and adventitious roots form from the sides. Here the hypocotyl is a rudimentary axis between radicle and plumule. The seeds of corn are constructed with these structures; pericarp, scutellum (single large cotyledon) that absorbs nutrients from the endosperm, plumule, radicle, coleoptile and coleorhiza – these last two structures are sheath-like and enclose the plumule and radicle, acting as a protective covering.

Seed coat

The maturing ovule undergoes marked changes in the integuments, generally a reduction and disorganization but occasionally a thickening. 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 segment and the outer forms the testa. (The seed coats of some monocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form a pericardia.) The testae of both monocots and dicots are often marked with patterns and textured markings, or have wings or tufts of hair. When the seed coat forms from only one layer, it is also called the testa, though not all such testate are homologous from one species to the next. The funiculars abscesses (detaches at fixed point – abscission zone), the scar forming an oval depression, the hilum. Anatropous ovules have a portion of the funiculars that is adnate (fused to the seed coat), and which forms a longitudinal ridge, or raphe, just above the hilum. In bitegmic ovules (e.g. Symposium described here) both inner and outer integuments contribute to the seed coat formation. With continuing maturation the cells enlarge in the outer integument. While the inner epidermis may remain a single layer, it may also divide to produce two to three layers and accumulates starch, and is referred to as the colourless layer. By contrast the outer epidermis becomes tanniferous. The inner integument may consist of eight to fifteen layers. (Kozlowski 1972)

As the cells enlarge, and starch is deposited in the outer layers of the pigmented zone below the outer epidermis, this zone begins to lignify, while the cells of the outer epidermis enlarge radially and their walls thicken, with nucleus and cytoplasm compressed into the outer layer. these cells which are broader on their inner surface are called palisade cells. In the inner epidermis the cells also enlarge radially with plate like thickening of the walls. The mature inner integument has a palisade layer, a pigmented zone with 15–20 layers, while the innermost layer is known as the fringe layer. (Kozlowski 1972)

Gymnosperms

In gymnosperms, which do not form ovaries, the ovules and hence the seeds are exposed. This is the basis for their nomenclature – naked seeded plants. Two sperm cells transferred from the pollen do not develop the seed by double fertilization, but one sperm nucleus unites with the egg nucleus and the other sperm is not used.

[4] Sometimes each sperm fertilizes an egg cell and one zygote is then aborted or absorbed during early development.[5] 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 such as pine and spruce.

Shape and appearance

A large number of terms are used to describe seed shapes, many of which are largely self-explanatory such as Bean-shaped (reniform) – resembling a kidney, with lobed ends on either side of the hilum, Square or Oblong – angular with all sides more or less equal or longer than wide, Triangular – three sided, broadest below middle, Elliptic or Ovate or Obovate – rounded at both ends, or egg shaped (ovate or obovate, broader at one end), being rounded but either symmetrical about the middle or broader below the middle or broader above the middle.[6]

Other less obvious terms include discoid (resembling a disc or plate, having both thickness and parallel faces and with a rounded margin), ellipsoid, globose (spherical), or subglobose (Inflated, but less than spherical), lenticular, oblong, ovoid, reniform and sectoroid. Striate seeds are striped with parallel, longitudinal lines or ridges. The commonest colours are brown and black, other colours are infrequent. The surface varies from highly polished to considerably roughened. The surface may have a variety of appendages (see Seed coat). A seed coat with the consistency of cork is referred to as suberose. Other terms include crustaceous (hard, thin or brittle).

Structure

Avocado seed diagram-en
The parts of an avocado seed (a dicot), showing the seed coat and embryo
Budowa nasienia-dwuliscienne
Diagram of the internal structure of a dicot seed and embryo: (a) seed coat, (b) endosperm, (c) cotyledon, (d) hypocotyl

A typical seed includes two basic parts:

  1. an embryo;
  2. a seed coat.

In addition, the endosperm forms a supply of nutrients for the embryo in most monocotyledons and the endospermic dicotyledons.

Seed types

Seeds have been considered to occur in many structurally different types (Martin 1946).[7] These are based on a number of criteria, of which the dominant one is the embryo-to-seed size ratio. This reflects the degree to which the developing cotyledons absorb the nutrients of the endosperm, and thus obliterate it.[7]

Six types occur amongst the monocotyledons, ten in the dicotyledons, and two in the gymnosperms (linear and spatulate).[8] This classification is based on three characteristics: embryo morphology, amount of endosperm and the position of the embryo relative to the endosperm.

Monocot dicot seed
Diagram of a generalized dicot seed (1) versus a generalized monocot seed (2). A. Seed Coat B. Cotyledon C. Hilum D. Plumule E. Radicle F. Endosperm
Comparison of Monocotyledons and Dicotyledons
Comparison of monocotyledons and dicotyledons

Embryo

In endospermic seeds, there are two distinct regions inside the seed coat, an upper and larger endosperm and a lower smaller embryo. The embryo is the fertilised ovule, an immature plant from which a new plant will grow under proper conditions. The embryo has one cotyledon or seed leaf in monocotyledons, two cotyledons in almost all dicotyledons and two or more in gymnosperms. In the fruit of grains (caryopses) the single monocotyledon is shield shaped and hence called a scutellum. The scutellum is pressed closely against the endosperm from which it absorbs food, and passes it to the growing parts. Embryo descriptors include small, straight, bent, curved and curled.

Nutrient storage

Within the seed, there usually is a store of nutrients for the seedling 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, which is derived from the mother plant and the pollen via double fertilization. It is usually triploid, and is rich in oil or starch, and protein. In gymnosperms, such as conifers, the food storage tissue (also called endosperm) is part of the female gametophyte, a haploid tissue. The endosperm is surrounded by the aleurone layer (peripheral endosperm), filled with proteinaceous aleurone grains.

Originally, by analogy with the animal ovum, the outer nucellus layer (perisperm) was referred to as albumen, and the inner endosperm layer as vitellus. Although misleading, the term began to be applied to all the nutrient matter. This terminology persists in referring to endospermic seeds as "albuminous". The nature of this material is used in both describing and classifying seeds, in addition to the embryo to endosperm size ratio. The endosperm may be considered to be farinaceous (or mealy) in which the cells are filled with starch, as for instance cereal grains, or not (non-farinaceous). The endosperm may also be referred to as "fleshy" or "cartilaginous" with thicker soft cells such as coconut, but may also be oily as in Ricinus (castor oil), Croton and Poppy. The endosperm is called "horny" when the cell walls are thicker such as date and coffee, or "ruminated" if mottled, as in nutmeg, palms and Annonaceae.[9]

In most monocotyledons (such as grasses and palms) and some (endospermic or albuminous) dicotyledons (such as castor beans) the embryo is embedded in the endosperm (and nucellus), which the seedling will use upon germination. In the non-endospermic dicotyledons the endosperm is absorbed by the embryo as the latter grows within the developing seed, and the cotyledons of the embryo become filled with stored food. At maturity, seeds of these species have no endosperm and are also referred to as exalbuminous seeds. The exalbuminous seeds include the legumes (such as beans and peas), trees such as the oak and walnut, vegetables such as squash and radish, and sunflowers. According to Bewley and Black (1978), Brazil nut storage is in hypocotyl, this place of storage is uncommon among seeds.[10] All gymnosperm seeds are albuminous.

Seed coat

The seed coat develops from the maternal tissue, the integuments, originally surrounding the ovule. The seed coat in the mature seed can be a paper-thin layer (e.g. peanut) or something more substantial (e.g. thick and hard in honey locust and coconut), or fleshy as in the sarcotesta of pomegranate. The seed coat helps protect the embryo from mechanical injury, predators and drying out. Depending on its development, the seed coat is either bitegmic or unitegmic. Bitegmic seeds form a testa from the outer integument and a tegmen from the inner integument while unitegmic seeds have only one integument. Usually parts of the testa or tegmen form a hard protective mechanical layer. The mechanical layer may prevent water penetration and germination. Amongst the barriers may be the presence of lignified sclereids.[11]

The outer integument has a number of layers, generally between four and eight organised into three layers: (a) outer epidermis, (b) outer pigmented zone of two to five layers containing tannin and starch, and (c) inner epidermis. The endotegmen is derived from the inner epidermis of the inner integument, the exotegmen from the outer surface of the inner integument. The endotesta is derived from the inner epidermis of the outer integument, and the outer layer of the testa from the outer surface of the outer integument is referred to as the exotesta. If the exotesta is also the mechanical layer, this is called an exotestal seed, but if the mechanical layer is the endotegmen, then the seed is endotestal. The exotesta may consist of one or more rows of cells that are elongated and pallisade like (e.g. Fabaceae), hence 'palisade exotesta'.[12][13]

In addition to the three basic seed parts, some seeds have an appendage, an aril, a fleshy outgrowth of the funicle (funiculus), (as in yew and nutmeg) or an oily appendage, an elaiosome (as in Corydalis), or hairs (trichomes). In the latter example these hairs are the source of the textile crop cotton. Other seed appendages include the raphe (a ridge), wings, caruncles (a soft spongy outgrowth from the outer integument in the vicinity of the micropyle), spines, or tubercles.

A scar also may remain on the seed coat, called the hilum, where the seed was attached to the ovary wall by the funicle. Just below it is a small pore, representing the micropyle of the ovule.

Size and seed set

Seed variety
A collection of various vegetable and herb seeds

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 mycoheterotrophs 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 lives deriving energy from the fungi and do not produce green leaves.[14] At over 20 kg, the largest seed is the coco de mer. 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 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.[15][16]

Functions

Seeds serve several functions for the plants that produce them. Key among these functions are nourishment of the embryo, dispersal to a new location, and dormancy during unfavorable conditions. Seeds fundamentally are means of reproduction, and most seeds are the product of sexual reproduction which produces a remixing of genetic material and phenotype variability on which natural selection acts.

Embryo nourishment

Seeds protect and nourish the embryo or young plant. They 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.

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 their offspring by dispersing their seeds (see also vegetative reproduction). 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.[17]

By wind (anemochory)

Taraxacum sect. Ruderalia MHNT
Dandelion seeds are contained within achenes, which can be carried long distances by the wind.
Milkweed-in-seed2
The seed pod of milkweed (Asclepias syriaca)
  • Some seeds (e.g., pine) 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) have hairs that aid in wind dispersal.[18]

Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways:

By water (hydrochory)

  • Some plants, such as Mucuna and Dioclea, produce buoyant seeds termed sea-beans or drift seeds because they float in rivers to the oceans and wash up on beaches.[19]

By animals (zoochory)

  • Seeds (burrs) with barbs or hooks (e.g. acaena, burdock, dock) which attach to animal fur or feathers, and then drop off later.
  • Seeds with a fleshy covering (e.g. apple, cherry, juniper) are eaten by animals (birds, mammals, reptiles, fish) which then disperse these seeds in their droppings.
  • Seeds (nuts) are attractive long-term storable food resources for animals (e.g. acorns, hazelnut, walnut); the seeds are stored some distance from the parent plant, and some escape being eaten if the animal forgets them.

Myrmecochory is the dispersal of seeds by ants. Foraging ants disperse seeds which have appendages called elaiosomes[20] (e.g. bloodroot, trilliums, acacias, and many species of Proteaceae). 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.[21] 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, the Argentine ant (Linepithema humile) has invaded 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 seedlings have dropped.[22]

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 a catastrophe (e.g. late frosts, drought, herbivory) does not result in the death of all offspring of a plant (bet-hedging).[23] 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.[24] 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.[25]

Often, seed dormancy is divided into four major categories: exogenous; endogenous; combinational; and secondary. A more recent system distinguishes five classes: morphological, physiological, morphophysiological, physical, and combinational dormancy.[26]

Exogenous dormancy is caused by conditions outside the embryo, including:

  • Physical dormancy or hard seed coats occurs when seeds are impermeable to water. At dormancy break, a specialized structure, the ‘water gap’, is disrupted in response to environmental cues, especially temperature, so water can enter the seed and germination can occur. Plant families where physical dormancy occurs include Anacardiaceae, Cannaceae, Convulvulaceae, Fabaceae and Malvaceae.[27]
  • 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.[28] 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, but little evidence exists to support this claim.[29]

Endogenous dormancy is caused by conditions within the embryo itself, including:

  • In morphological dormancy, 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, Cycadaceae, Liliaceae, Magnoliaceae and Ranunculaceae.[30][31]
  • Morphophysiological dormancy includes seeds with underdeveloped embryos, and also 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, Aquifoliaceae, Liliaceae, Magnoliaceae, Papaveraceae and Ranunculaceae.[30] Some plants with morphophysiological dormancy, such as Asarum or Trillium species, have multiple types of dormancy, one affects radicle (root) growth, while the other affects plumule (shoot) growth. The terms "double dormancy" and "two-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.[30]
  • Physiological dormancy means the embryo, due to physiological causes, cannot 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 is usually the growth inhibitor in seeds, and its production can be affected by light.
    • Drying, in some plants, including a number of grasses and those from seasonally arid regions, is needed 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.[32]
  • 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.[31]
  • Secondary dormancy* is caused by conditions after the seed has been dispersed and occurs in some seeds when nondormant 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.[33]

The following types of seed dormancy do not involve seed dormancy, strictly speaking, as lack of germination is prevented by the environment, not by characteristics of the seed itself (see Germination):

  • 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 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 (30 °C or 86 °F); many plants that have seeds that germinate in early to midsummer have thermodormancy, so germinate only when the soil temperature is warm. Other seeds need cool soils to germinate, while others, such as 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 mangroves 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 plant seeds 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 it. After many generations of selective pressure by plant breeders and gardeners, dormancy has been selected out.

For annuals, 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.[34]

Persistence and seed banks

Germination

Sunflower seedlings
Germinating sunflower seedlings

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.[35]

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.[36]

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.[37] 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 affecting seed germination include; water, oxygen, temperature and light.

Three distinct phases of seed germination occur: water imbibition; lag phase; and radicle 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. 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.

Repair of DNA damage

During seed dormancy, often associated with unpredictable and stressful environments, DNA damage accumulates as the seeds age.[38][39][40] In rye seeds, the reduction of DNA integrity due to damage is associated with loss of seed viability during storage.[38] Upon germination, seeds of Vicia faba undergo DNA repair.[39] A plant DNA ligase that is involved in repair of single- and double-strand breaks during seed germination is an important determinant of seed longevity.[41] Also, in Arabidopsis seeds, the activities of the DNA repair enzymes Poly ADP ribose polymerases (PARP) are likely needed for successful germination.[42] Thus DNA damages that accumulate during dormancy appear to be a problem for seed survival, and the enzymatic repair of DNA damages during germination appears to be important for seed viability.

Inducing germination

A number of different strategies are used by gardeners and horticulturists to break seed dormancy.

Scarification allows water and gases to penetrate into the seed; it includes methods to physically break the hard seed coats or soften them by chemicals, such as 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. 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, while often weakening the seed coat such that the embryo is ready to sprout when it is deposited, along with a bit of fecal matter that acts as fertilizer, far from the parent plant. Microorganisms 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 nonsterile conditions.

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

Leaching or the soaking in water removes chemical inhibitors in some seeds that prevent germination. Rain and melting snow 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, 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, such as gibberellins, cytokinins, ethylene, thiourea, sodium hypochlorite, and others.[43] Some seeds germinate best after a fire. For some seeds, fire cracks hard seed coats, while in others, 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.[44]

Sterile seeds

Seeds may be sterile for few reasons: they may have been irradiated, unpollinated, cells lived past expectancy, or bred for the purpose.

Evolution and origin of seeds

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. The description in 2004 of the proto-seed Runcaria heinzelinii in the Givetian of Belgium 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. With this radiation came an evolution of seed size, shape, dispersal and eventually the radiation of gymnosperms and angiosperms and monocotyledons and dicotyledons. The seed plants progressively became one of the major elements of nearly all ecosystems.

Economic importance

Phaseolus vulgaris seed
Phaseolus vulgaris (common bean or green bean) seeds are diverse in size, shape, and color.

Seed market

In the United States farmers spent $22 billion on seeds in 2018, a 35 percent increase since 2010. DowDuPont and Monsanto account for 72 percent of corn and soybean seed sales in the U.S. with the average price of a bag of GMO corn seed is priced at $270.[45]

Edible seeds

Many seeds are edible and the majority of human calories comes from seeds,[46] especially from cereals, legumes and nuts. Seeds also provide most cooking oils, many beverages and spices and some important food additives. In different seeds the seed embryo or the endosperm dominates and provides most of the nutrients. The storage proteins of the embryo and endosperm differ in their amino acid content and physical properties. For example, the gluten of wheat, important in providing the elastic property to bread dough is strictly an endosperm protein.

Seeds are used to propagate many crops such as cereals, legumes, forest trees, turfgrasses, and pasture grasses. Particularly in developing countries, a major constraint faced is the inadequacy of the marketing channels to get the seed to poor farmers.[47] Thus the use of farmer-retained seed remains quite common.

Seeds are also eaten by animals (seed predation), and are also fed to livestock or provided as birdseed.

Poison and food safety

While some seeds are edible, others are harmful, poisonous or deadly.[48] Plants and seeds often contain chemical compounds to discourage herbivores and seed predators. In some cases, these compounds simply taste bad (such as in mustard), 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.[49]

A deadly poison, ricin, comes from seeds of the castor bean. Reported lethal doses are anywhere from two to eight seeds,[50][51] though only a few deaths have been reported when castor beans have been ingested by animals.[52]

In addition, seeds containing amygdalin – apple, apricot, bitter almond,[53] peach, plum, cherry, quince, and others – when consumed in sufficient amounts, may cause cyanide poisoning.[53][54] Other seeds that contain poisons include annona, cotton, custard apple, datura, uncooked durian, golden chain, horse-chestnut, larkspur, locoweed, lychee, nectarine, rambutan, rosary pea, sour sop, sugar apple, wisteria, and yew.[50][55] The seeds of the strychnine tree are also poisonous, containing the poison strychnine.

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. The common bean and many others, including the soybean, also contain trypsin inhibitors which interfere with the action of the digestive enzyme trypsin. Normal cooking processes degrade lectins and trypsin inhibitors to harmless forms.[56]

Please see the category plant toxins for further relevant articles.

Other uses

Cotton fiber grows attached to cotton plant seeds. Other seed fibers are from kapok and milkweed.

Many important nonfood oils are extracted from seeds. Linseed oil is used in paints. Oil from jojoba and crambe are similar to whale oil.

Seeds are the source of some medicines including castor oil, tea tree oil and the quack cancer drug Laetrile.

Many seeds have been used as beads in necklaces and rosaries including Job's tears, Chinaberry, rosary pea, and castor bean. However, the latter three are also poisonous.

Other seed uses include:

Seed records

Female coco de mer seed
The massive fruit of the coco de mer

In religion

The Book of Genesis in the Old Testament begins with an explanation of how all plant forms began:

And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so. And the earth brought forth grass, and herb yielding seed after its kind, and the tree yielding fruit, whose seed was in itself, after its kind: and God saw that it was good. And the evening and the morning were the third day.[63]

The Quran speaks of seed germination thus:

It is Allah Who causeth the seed-grain and the date-stone to split and sprout. He causeth the living to issue from the dead, and He is the one to cause the dead to issue from the living. That is Allah: then how are ye deluded away from the truth?[64]

See also

References

  1. ^ Cain M.D., Shelton M.G. (2001). "Twenty years of natural loblolly and shortleaf pine seed production on the Crossett Experimental Forest in southeastern Arkansas". Southern Journal of Applied Forestry. 25 (1): 40–45.
  2. ^ Galili G; Kigel J (1995). "Chapter One". Seed development and germination. New York: M. Dekker. ISBN 978-0-8247-9229-9.
  3. ^ Raven, Peter H., Ray Franklin Evert, and Helena Curtis. 1981. Biology of plants. New York: Worth Publishers. p. 410.
  4. ^ Rost, Thomas L.; Weier, T. Elliot; Weier, Thomas Elliot (1979). Botany: a brief introduction to plant biology. New York: Wiley. p. 319. ISBN 978-0-471-02114-8.
  5. ^ Filonova LH; Bozhkov PV; von Arnold S (February 2000). "Developmental pathway of somatic embryogenesis in Picea abies as revealed by time-lapse tracking". J Exp Bot. 51 (343): 249–264. doi:10.1093/jexbot/51.343.249. PMID 10938831. Archived from the original on 2008-12-07.
  6. ^ "Seed shape". anbg.gov.au. Archived from the original on 2014-02-26.
  7. ^ a b The Seed Biology Place, Gerhard Leubner Lab, Royal Holloway, University of London, archived from the original on 24 September 2015, retrieved 13 October 2015
  8. ^ Baskin, Carol C.; Baskin, Jerry M. (2001). Carol C. Baskin, Jerry M. Baskin. Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. Elsevier, 2001. google.ca. p. 27. ISBN 978-0-12-080263-0.
  9. ^ "The Encyclopædia Britannica, 9th ed. (1888) vol. 4". google.ca. 1888. p. 155.
  10. ^ Bewley & Black (1978) Physiology and Biochemistry of Seeds in Relation to Germination, pag.11
  11. ^ "Sinauer Associates, Inc., Publishers". 5e.plantphys.net. Archived from the original on 22 January 2014. Retrieved 7 May 2018.
  12. ^ "plant_anatomy Term "seed coat epidermis" (PO:0006048)". gramene.org. Archived from the original on 2014-02-03.
  13. ^ Rudall, Paula J. (2007). 6 – Seed and fruit – University Publishing Online – Paula J. Rudall. Anatomy of Flowering Plants: An Introduction to Structure and Development. Third edition. Cambridge University Press. doi:10.1017/CBO9780511801709. ISBN 978-0-521-69245-8.
  14. ^ Smith, Welby R. 1993. Orchids of Minnesota. Minneapolis: University of Minnesota Press. p. 8.
  15. ^ Kosinki, Igor (2007). "Long-term variability in seed size and seedling establishment of Maianthemum bifolium". Plant Ecology. 194 (2): 149–156. doi:10.1007/s11258-007-9281-1.
  16. ^ Shannon DA; Isaac L; Brockman FE (February 1996). "Assessment of hedgerow species for seed size, stand establishment and seedling height". Agroforestry Systems. 35 (1): 95–110. doi:10.1007/BF02345331.
  17. ^ Jones, Samuel B., and Arlene E. Luchsinger. 1979. Plant systematics. McGraw-Hill series in organismic biology. New York: McGraw-Hill. p. 195.
  18. ^ Morhardt, Sia; Morhardt, Emil; Emil Morhardt, J. (2004). California desert flowers: an introduction to families, genera, and species. Berkeley: University of California Press. p. 24. ISBN 978-0-520-24003-2.
  19. ^ "www.seabean.com – Sea-Beans and Drift Seeds". seabean.com. Archived from the original on 2006-07-11.
  20. ^ Marinelli J (1999). "Ants – The astonishing intimacy between ants & plants". Plants & Gardens News. 14 (1). Archived from the original on 2006-08-18.
  21. ^ Ricklefs, Robert E. (1993) The Economy of Nature, 3rd ed., p. 396. (New York: W.H. Freeman). ISBN 0-7167-2409-X.
  22. ^ Bond, W.J.; P. Slingsby (1984). "Collapse of an ant-plant mutualism: The Argentine ant, Iridomyrmex humilis and myrmecochorous Proteaceae". Ecology. 65 (4): 1031–1037. doi:10.2307/1938311. JSTOR 1938311.
  23. ^ Eira MTS, Caldas LS (2000) Seed dormancy and germination as concurrent processes. Rev Bras Fisiol Vegetal 12:85–104
  24. ^ Vleeshouwers L.M., Bouwmeester H.J., Karssen C.M. (1995). "Redefining seed dormancy: an attempt to integrate physiology and ecology". Journal of Ecology. 83 (6): 1031–1037. doi:10.2307/2261184. JSTOR 2261184.CS1 maint: Multiple names: authors list (link)
  25. ^ Thompson K, Ceriani RM, Bakker JP, Bekker RM (2003). "Are seed dormancy and persistence in soil related?". Seed Science Research. 13 (2): 97–100. doi:10.1079/ssr2003128.
  26. ^ Baskin J.M., Baskin C.C. (2004). "A classification system for seed dormancy". Seed Science Research. 14: 1–16. doi:10.1079/ssr2003150.
  27. ^ Baskin JM, Baskin CC, Li X (2000) "Taxonomy, anatomy and evolution of physical dormancy in seeds". Plant Species Biology 15:139–152
  28. ^ Baskin, C.C. and Baskin, J.M. (1998) Seeds: Ecology, biogeography, and evolution of dormancy and germination.San Diego, Academic Press
  29. ^ Gutterman, Y. (1993) Seed germination in desert plants. Springer Verlag, Berlin/Heidelberg.
  30. ^ a b c Baskin, C.C. and Baskin, J.M. (1998) Seeds: Ecology, biogeography, and evolution of dormancy and germination.San Diego, Academic Press.
  31. ^ a b Baskin, J.M. and Baskin, C.C. (2004) A classification system for seed dormancy. Seed Science Research 14:1–16.
  32. ^ International Workshop on Seeds, and G. Nicolas. 2003. The biology of seeds recent research advances : proceedings of the Seventh International Workshop on Seeds, Salamanca, Spain 2002. Wallingford, Oxon, UK: CABI Pub. p. 113.
  33. ^ Bewley, J. Derek, and Michael Black. 1994. Seeds physiology of development and germination. The language of science. New York: Plenum Press. p. 230.
  34. ^ Patten D.T. (1978). "Productivity and production efficiency of an Upper Sonoran Desert ephemeral community". American Journal of Botany. 65 (8): 891–895. doi:10.2307/2442185. JSTOR 2442185.
  35. ^ Black, Michael H.; Halmer, Peter (2006). The encyclopedia of seeds: science, technology and uses. Wallingford, UK: CABI. p. 224. ISBN 978-0-85199-723-0.
  36. ^ Seed Vigor and Vigor Tests Archived 2006-09-12 at the Wayback Machine
  37. ^ International Seed Testing Association. 1973. ISSN 0251-0952. pp. 120–121.Seed science and technology. Wageningen?: International Seed Testing Association.
  38. ^ a b Cheah KS; Osborne DJ (April 1978). "DNA lesions occur with loss of viability in embryos of ageing rye seed". Nature. 272 (5654): 593–599. doi:10.1038/272593a0. PMID 19213149.
  39. ^ a b Koppen G; Verschaeve L (2001). "The alkaline single-cell gel electrophoresis/comet assay: a way to study DNA repair in radicle cells of germinating Vicia faba". Folia Biol. (Praha). 47 (2): 50–54. PMID 11321247.
  40. ^ Bray CM; West CE (December 2005). "DNA repair mechanisms in plants: crucial sensors and effectors for the maintenance of genome integrity". New Phytol. 168 (3): 511–528. doi:10.1111/j.1469-8137.2005.01548.x. PMID 16313635.
  41. ^ Waterworth WM; Masnavi G; Bhardwaj RM; Jiang Q; Bray CM; West CE (September 2010). "A plant DNA ligase is an important determinant of seed longevity". Plant J. 63 (5): 848–860. doi:10.1111/j.1365-313X.2010.04285.x. PMID 20584150.
  42. ^ Hunt L; Holdsworth MJ; Gray JE (August 2007). "Nicotinamidase activity is important for germination". Plant J. 51 (3): 341–351. doi:10.1111/j.1365-313X.2007.03151.x. PMID 17587307.
  43. ^ Hartmann, Hudson Thomas, and Dale E. Kester. 1983. Plant propagation principles and practices. Englewood Cliffs, NJ: Prentice-Hall. ISBN 0-13-681007-1. pp. 175–177.
  44. ^ Jon E. Keeley and Fotheringham (1997-05-23). "Trace Gas Emissions and Smoke-Induced Seed Germination". Science. 276 (276 (5316)): 1248–1250. CiteSeerX 10.1.1.3.2708. doi:10.1126/science.276.5316.1248.
  45. ^ Dunn, Elizabeth G. (2019-03-04). "The Startup Taking On Bayer With Cheaper, Non-GMO Seeds". Bloomberg Businessweek. Retrieved 2019-03-07.
  46. ^ Sabelli, P.A.; Larkins, B.A. (2009). "The Development of Endosperm in Grasses". Plant Physiology. 149 (1): 14–26. doi:10.1104/pp.108.129437. PMC 2613697. PMID 19126691.
  47. ^ G. Mumby Seed Marketing Archived 2009-09-09 at the Wayback Machine, FAO, Rome
  48. ^ Chia Joo Suan, "Seeds of Doubt: Food Safety Archived 2008-04-29 at the Wayback Machine"
  49. ^ Clelland, Mike. "Poisonous Plants and Seeds Archived 2007-10-12 at the Wayback Machine", Healthy Child Care
  50. ^ a b Martin Anderson, Texas AgriLife Extension Service. "Poisonous Plants and Plant Parts – Archives – Aggie Horticulture". tamu.edu. Archived from the original on 2007-09-08.
  51. ^ Wedin GP; Neal JS; Everson GW; Krenzelok EP (May 1986). "Castor bean poisoning". Am J Emerg Med. 4 (3): 259–261. doi:10.1016/0735-6757(86)90080-X. PMID 3964368.
  52. ^ Albretsen JC; Gwaltney-Brant SM; Khan SA (2000). "Evaluation of castor bean toxicosis in dogs: 98 cases". J Am Anim Hosp Assoc. 36 (3): 229–233. doi:10.5326/15473317-36-3-229. PMID 10825094. Archived from the original on 2012-08-02.
  53. ^ a b "Almond/Almond Oil". drugs.com. Archived from the original on 2017-07-18.
  54. ^ Wolke, RL. Seeds of Anxiety Washington Post January 5, 2005 Archived September 15, 2017, at the Wayback Machine
  55. ^ Chia Joo Suan Food Safety: Seeds of doubt Archived 2008-04-29 at the Wayback Machine
  56. ^ Dhurandhar NV; Chang KC (1990). "Effect of Cooking on Firmness, Trypsin Inhibitors, Lectins and Cystine/Cysteine content of Navy and Red Kidney Beans (Phaseolus vulgaris)". J Food Sci. 55 (2): 470–474. doi:10.1111/j.1365-2621.1990.tb06789.x. Archived from the original on 2013-01-05.
  57. ^ Roach, John. (2005) "2,000-Year-Old Seed Sprouts, Sapling Is Thriving Archived 2007-02-03 at the Wayback Machine", National Geographic News, 22 November.
  58. ^ "Ice Age flower revival that could lead to resurrection of mammoth". Telegraph.co.uk. 21 February 2012. Archived from the original on 22 March 2014.
  59. ^ "Russian Scientists Revive 32,000-Year-Old Flower". sci-news.com. Archived from the original on 2012-02-27.
  60. ^ Corner EJH (1966). The Natural History of Palms. Berkeley, CA: University of California Press. pp. 313–314.
  61. ^ http://waynesword.palomar.edu/ww0601.htm#seed Archived 2010-12-19 at the Wayback Machine
  62. ^ Taylor EL; Taylor TMC (1993). The biology and evolution of fossil plants. Englewood Cliffs, NJ: Prentice Hall. p. 466. ISBN 978-0-13-651589-0.
  63. ^ King James Version, Genesis 1:12,13, 1611.
  64. ^ Quran, Translation: Abdullah Yusuf Ali, Al-An'aam 95:6

Bibliography

External links

Angelique Kerber

Angelique Kerber (German: [ʔandʒɛˈliːk ˈkɛɐ̯bɐ]; born 18 January 1988) is a German professional tennis player. A former world No. 1 and winner of three Grand Slam tournaments, she made her professional debut in 2003 and rose to prominence upon reaching the semifinals of the 2011 US Open as the No. 92-ranked player in the world. She ascended to the top of the rankings on 12 September 2016, thus becoming the twenty-second and oldest player to achieve the number-one ranking for the first time and the first new number-one player since Victoria Azarenka in 2012.A left-hander known for her counter-punching all-court game, Kerber has won 12 career singles titles across all surfaces on the WTA Tour, including the aforementioned three Grand Slam titles: the 2016 Australian Open, the 2016 US Open and the 2018 Wimbledon Championships. She has also won an Olympic silver medal while representing Germany at the 2016 Rio Olympics. Kerber is currently ranked world No. 5 as of 24 June 2019.

Coriander

Coriander (; Coriandrum sativum) is an annual herb in the family Apiaceae. It is also known as Chinese parsley, and the stems and leaves are usually called cilantro () in North America. All parts of the plant are edible, but the fresh leaves and the dried seeds (as a spice) are the parts most traditionally used in cooking.

Most people perceive the taste of coriander leaves as a tart, lemon/lime taste, but a smaller group of about 4–14% of people tested think the leaves taste like dish soap, linked to a gene which detects some specific aldehydes that are also used as odorant substances in many soaps and detergents.

Fruit

In botany, a fruit is the seed-bearing structure in flowering plants (also known as angiosperms) formed from the ovary after flowering.

Fruits are the means by which angiosperms disseminate seeds. Edible fruits, in particular, have propagated with the movements of humans and animals in a symbiotic relationship as a means for seed dispersal and nutrition; in fact, humans and many animals have become dependent on fruits as a source of food. Accordingly, fruits account for a substantial fraction of the world's agricultural output, and some (such as the apple and the pomegranate) have acquired extensive cultural and symbolic meanings.

In common language usage, "fruit" normally means the fleshy seed-associated structures of a plant that are sweet or sour, and edible in the raw state, such as apples, bananas, grapes, lemons, oranges, and strawberries. On the other hand, in botanical usage, "fruit" includes many structures that are not commonly called "fruits", such as bean pods, corn kernels, tomatoes, and wheat grains. The section of a fungus that produces spores is also called a fruiting body.

Germination

Germination is the process by which an organism grows from a seed or similar structure. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. In addition, the growth of a sporeling from a spore, such as the spores of hyphae from fungal spores, is also germination. Thus, in a general sense, germination can be thought of as anything expanding into greater being from a small existence or germ.

Grape

A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus Vitis.

Grapes can be eaten fresh as table grapes or they can be used for making wine, jam, juice, jelly, grape seed extract, raisins, vinegar, and grape seed oil. Grapes are a non-climacteric type of fruit, generally occurring in clusters.

Johanna Konta

Johanna Konta (born 17 May 1991) is a British professional tennis player who represented Australia until 2012. She has won three singles titles on the WTA Tour, as well as 11 singles and four doubles titles on the ITF Women's Circuit. The current British number one reached her best singles ranking of world No. 4 on 17 July 2017. She has reached the semis of the Australian Open, Wimbledon and the French Open.

Konta achieved a steep rise in her ranking from the spring of 2015 to late 2016, climbing from 150 to inside the world's top ten, thereby becoming the first Briton to be ranked amongst the WTA's top ten since Jo Durie over 30 years previously. This period included her best Grand Slam result up to that time, as she reached the semifinal of the 2016 Australian Open, a quarterfinal appearance at the Rio Summer Olympics and her maiden WTA title in Stanford. In 2017, she won the Miami Open, and reached the semifinal at Wimbledon.Born to Hungarian parents in Sydney, Australia, Konta moved to the UK when she was 14. She switched her sporting allegiance from Australia to Great Britain after she became a British citizen in May 2012.

Marion Bartoli

Marion Bartoli (French: [maʁjɔ̃ baʁtɔli]; born 2 October 1984) is a French former professional tennis player. She won the 2013 Wimbledon Championships singles title after previously being runner-up in 2007, and was a semifinalist at the 2011 French Open. She also won eight Women's Tennis Association singles and three doubles titles. She announced her immediate retirement from professional tennis on 14 August 2013.

Bartoli defeated three reigning world No. 1 players in her career: Justine Henin in the semifinal of the 2007 Wimbledon Championships, Jelena Janković in the fourth round of the 2009 Australian Open, and Victoria Azarenka in the quarterfinals of the 2012 Sony Ericsson Open. She also recorded wins over other top players such as Venus and Serena Williams, Ana Ivanovic, Lindsay Davenport, Arantxa Sánchez Vicario, Dinara Safina, Caroline Wozniacki, Petra Kvitová, Samantha Stosur, and Kim Clijsters.

She is known for her unorthodox style of play using two hands on both her forehand and backhand. On 30 January 2012 she reached a career-high ranking of No. 7 in the world; she returned to this ranking on 8 July 2013 after triumphing at Wimbledon. Bartoli reached at least the quarterfinal stage at each of the four Grand Slams. Her win at Wimbledon made her only the sixth player in the open era to win the Championships without dropping a single set. She is also the only player ever to have played at both the WTA Tour Championships and the WTA Tournament of Champions in the same year, in 2011.

Mobile Suit Gundam SEED

Mobile Suit Gundam SEED (Japanese: 機動戦士ガンダムSEED (シード), Hepburn: Kidō Senshi Gandamu Shīdo) is an anime series developed by Sunrise and directed by Mitsuo Fukuda. The ninth installment in the Gundam franchise, Gundam SEED takes place in a future calendar era, in this case the Cosmic Era, the first to do so. In this era, mankind has developed into two subspecies: Naturals, who reside on Earth, and Coordinators, genetically enhanced humans capable of amazing feats of intellect who emigrate to man-made orbital colonies to escape persecution by natural humans. The story revolves around a young Coordinator Kira Yamato who becomes involved in the war between the two races after a third, neutral faction's space colony is invaded by the Coordinators.

The television series was broadcast in Japan between 2002 and 2003, on the Tokyo Broadcasting System and Mainichi Broadcasting System networks, beginning a broadcast partnership with the Gundam franchise. The series spawned three compilations films and was adapted into a manga as well as light novels. A sequel series, Mobile Suit Gundam SEED Destiny followed in 2004. Merchandise has been released, including models, CD soundtracks and video games. Gundam SEED was licensed by Bandai Entertainment for broadcast in North America, and began airing in the United States and Canada in 2004 and 2005 respectively. The films and the sequel were also licensed by Bandai. The manga and light novels as well as the spin-off series, Mobile Suit Gundam SEED Astray, were licensed. Video games were released in North America.

Mobile Suit Gundam SEED was widely popular with the public in Japan, winning numerous awards, with high sales of the series DVD and music. The character development and animation has gained praise, but similarities with previous Gundam series have drawn both comparisons and criticism from Gundam fans.

Nut (fruit)

A nut is a fruit composed of an inedible hard shell and a seed, which is generally edible. In general usage, a wide variety of dried seeds are called nuts, but in a botanical context "nut" implies that the shell does not open to release the seed (indehiscent). The translation of "nut" in certain languages frequently requires paraphrases, as the word is ambiguous.

Most seeds come from fruits that naturally free themselves from the shell, unlike nuts such as hazelnuts, chestnuts, and acorns, which have hard shell walls and originate from a compound ovary. The general and original usage of the term is less restrictive, and many nuts (in the culinary sense), such as almonds, pecans, pistachios, walnuts, and Brazil nuts, are not nuts in a botanical sense. Common usage of the term often refers to any hard-walled, edible kernel as a nut. Nuts are an energy-dense and nutrient-rich food source.

Nutmeg

Nutmeg is the seed or ground spice of several species of the genus Myristica. Myristica fragrans (fragrant nutmeg or true nutmeg) is a dark-leaved evergreen tree cultivated for two spices derived from its fruit: nutmeg, from its seed, and mace, from the seed covering. It is also a commercial source of an essential oil and nutmeg butter. The California nutmeg, Torreya californica, has a seed of similar appearance, but is not closely related to Myristica fragans, and is not used as a spice. If consumed in amounts exceeding its typical use as a spice, nutmeg powder may produce allergic reactions, cause contact dermatitis, or have psychoactive effects. Although used in traditional medicine for treating various disorders, nutmeg has no known medicinal value.

Petra Kvitová

Petra Kvitová (Czech pronunciation: [ˈpɛtra ˈkvɪtovaː]; born 8 March 1990) is a Czech professional tennis player. Known for her powerful left-handed groundstrokes and variety, Kvitová turned professional in 2006 and has won 27 career singles titles, two of which are Grand Slam titles, the Wimbledon Championships in 2011 and in 2014. She also won a bronze medal at the 2016 Rio Olympics. Her career-high ranking of world No. 2 was reached on 31 October 2011 and as of 15 July 2019, she is ranked world No. 6 by the Women's Tennis Association (WTA). As such, Kvitová is currently the second highest-ranked left-handed player in the world and the second highest-ranked Czech, behind Karolína Plíšková.

Kvitová first gained notice upon defeating then-world No. 1 Dinara Safina in the third round of the 2009 US Open. This was followed by her first Grand Slam semifinal appearance at the 2010 Wimbledon Championships where she came up short to eventual champion Serena Williams. Then, during her breakthrough season in 2011, Kvitová won her first Grand Slam title at the Wimbledon Championships, defeating Maria Sharapova in the final, thus becoming the first player of either gender born in the 1990s to win a Grand Slam tournament title. She also won the WTA Tour Championships, thus becoming the third player to win the tournament on debut, the others being Williams and Sharapova. She also helped lead the Czech Republic to victory in the Fed Cup final that same year. It was the Czech Republic's first Fed Cup title as an independent nation.

In 2012, Kvitová made the semifinals of the Australian Open and French Open, and was crowned US Open Series champion. That same year, she also won the Hopman Cup alongside Tomáš Berdych. In 2014, she won her second and most recent Grand Slam title at the Wimbledon Championships, defeating Eugenie Bouchard in the final. In 2015, Kvitová achieved the feat of making the quarterfinals at all four Grand Slams after advancing to her first quarterfinal at the US Open, where she lost to eventual champion Flavia Pennetta. In 2016, she won the WTA Elite Trophy in her first appearance at the tournament, thus becoming the first player ever to win both categories of year-ending championships on debut. In 2019, she returned to her first Grand Slam final in almost five years, at the Australian Open where she finished runner-up to Naomi Osaka.

Poppy seed

Poppy seed is an oilseed obtained from the poppy (Papaver somniferum). The tiny kidney-shaped seeds have been harvested from dried seed pods by various civilizations for thousands of years. It is still widely used in many countries, especially in Central Europe, where it is legally grown and sold in shops. The seeds are used whole or ground into meal as an ingredient in many foods – especially in pastry and bread – and they are pressed to yield poppyseed oil.

Potato

The potato is a starchy, tuberous crop from the perennial nightshade Solanum tuberosum, native to the Americas. In many contexts, potato refers to the edible tuber, but it can also refer to the plant itself. Common or slang terms include tater, tattie, and spud.

Wild potato species can be found throughout the Americas, from the United States to southern Chile. The potato was originally believed to have been domesticated by indigenous peoples of the Americas independently in multiple locations, but later genetic testing of the wide variety of cultivars and wild species traced a single origin for potatoes. In the area of present-day southern Peru and extreme northwestern Bolivia, from a species in the Solanum brevicaule complex, potatoes were domesticated approximately 7,000–10,000 years ago. In the Andes region of South America, where the species is indigenous, some close relatives of the potato are cultivated.

Potatoes were introduced to Europe from the Americas in the second half of the 16th century by the Spanish. Today they are a staple food in many parts of the world and an integral part of much of the world's food supply. As of 2014, potatoes were the world's fourth-largest food crop after maize (corn), wheat, and rice.Following millennia of selective breeding, there are now over 1,000 different types of potatoes. Over 99% of presently cultivated potatoes worldwide descended from varieties that originated in the lowlands of south-central Chile, which have displaced formerly popular varieties from the Andes.The importance of the potato as a food source and culinary ingredient varies by region and is still changing. It remains an essential crop in Europe, especially Northern and Eastern Europe, where per capita production is still the highest in the world, while the most rapid expansion in production over the past few decades has occurred in southern and eastern Asia, with China and India leading the world in overall production as of 2014.

Being a nightshade similar to tomatoes, the vegetative and fruiting parts of the potato contain the toxin solanine and are not fit for human consumption. Normal potato tubers that have been grown and stored properly produce glycoalkaloids in amounts small enough to be negligible to human health, but if green sections of the plant (namely sprouts and skins) are exposed to light, the tuber can accumulate a high enough concentration of glycoalkaloids to affect human health.

Rapeseed

Rapeseed (B. napus subsp. napus), also known as rape, oilseed rape, and, in the case of one particular group of cultivars, canola, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed. It is the third-largest source of vegetable oil and second-largest source of protein meal in the world.

Roberto Bautista Agut

Roberto Bautista Agut (Spanish pronunciation: [roˈβeɾto βauˈtista aˈɣut]; born 14 April 1988) is a Spanish professional tennis player who is currently ranked world No. 13 in men's singles by the Association of Tennis Professionals (ATP).Agut has won nine ATP singles titles (9–7 in finals), the biggest being the 2018 Dubai Duty Free Championship, an ATP 500 tournament. His biggest final to date was the 2016 Shanghai Masters, where he lost to Andy Murray. His best result at a major was at the 2019 Wimbledon Championships, where he reached the semifinals. Bautista Agut achieved a career-high singles ranking of world No. 13 in October 2016.

Sesame

Sesame (; Sesamum indicum) is a flowering plant in the genus Sesamum, also called benne. Numerous wild relatives occur in Africa and a smaller number in India. It is widely naturalized in tropical regions around the world and is cultivated for its edible seeds, which grow in pods or "buns". World production in 2016 was 6.1 million tonnes, with Tanzania, Myanmar, India, and Sudan as the largest producers.Sesame seed is one of the oldest oilseed crops known, domesticated well over 3000 years ago. Sesamum has many other species, most being wild and native to sub-Saharan Africa. Sesamum indicum, the cultivated type, originated in India and is tolerant to drought-like conditions, growing where other crops fail.Sesame has one of the highest oil contents of any seed. With a rich, nutty flavor, it is a common ingredient in cuisines across the world. Like other nuts and foods, it can trigger allergic reactions in some people.

Sesame seeds are sometimes sold with the seed coat removed (decorticated); this variety is often present on top of baked goods in many countries.

Simona Halep

Simona Halep (Romanian pronunciation: [siˈmona haˈlep]; born 27 September 1991) is a Romanian professional tennis player. She has been ranked world No. 1 in singles twice between 2017 and 2019. She reached the No. 1 ranking for the first time on 9 October 2017. On her second occasion, she held the ranking for 48 consecutive weeks. In total, she has been No. 1 for 64 weeks, which ranks tenth in the history of women's tennis. Halep was the year-end No. 1 in 2017 and 2018. She has won 19 WTA singles titles. Halep has also finished runner-up 17 times. Halep has won two Grand Slam singles titles: the 2018 French Open, and the 2019 Wimbledon Championships.Halep first broke into the world's top 50 at the end of 2012, reached the top 20 in August 2013, and finally the top 10 in January 2014. She won her first six WTA titles in the same calendar year in 2013 (the first to do so since Steffi Graf in 1986), being named the WTA's Most Improved Player at its end, as well as being named ESPN Center Court's 2013 Most Improved Player. Halep won her first major tournament at the 2018 French Open, and went on to win the Wimbledon Championships in 2019. She had previously reached the finals of the 2014 French Open, 2017 French Open and 2018 Australian Open finals. She also reached the final of the 2014 WTA Finals, losing to Serena Williams in straight sets after having defeated her earlier in the tournament 6–0, 6–2 (which to that point was Serena's worst defeat in her career).Halep was the most clicked player on WTATennis.com for two consecutive years (2014–2015), when she was awarded the WTA Most Popular Player of the Year prize. After the 2017 Wimbledon Championships, Simona Halep became the active player with the most consecutive weeks within the top 10. Halep has also won WTA's Fan Favorite Singles Player in 2017 and 2018, and WTA's Player of the Year in 2018. In December 2018, Halep was chosen by ESPN most dominant tennis player of the year and ranked ninth in The Dominant 20 top of the most dominant 20 athletes in the world. She notched a 46–8 record. She was given the award of Cetățean de onoare ("Honorary Citizen") of the city of Bucharest in 2018. She is also a recipient of the Patriarchal Cross of Romania and the Order of the Star of Romania.Halep is the third Romanian female tennis player, after Virginia Ruzici and Irina Spîrlea, to have ever entered the top 10 WTA ranking (Magda Rurac was also ranked in the top 10 in unofficial world rankings in 1948 and 1949, before the existence of WTA rankings). She is also the first Romanian tennis player to win a Wimbledon singles title.

Single-elimination tournament

A single-elimination, knockout, or sudden death tournament is a type of elimination tournament where the loser of each match-up is immediately eliminated from the tournament. Each winner will play another in the next round, until the final match-up, whose winner becomes the tournament champion. Each match-up may be a single match or several, for example two-legged ties in European football or best-of series in American pro sports. Defeated competitors may play no further part after losing, or may participate in "consolation" or "classification" matches against other losers to determine the lower final rankings; for example, a third place playoff between losing semi-finalists. In a shootout poker tournament, there are more than two players competing at each table, and sometimes more than one progressing to the next round. Some competitions are held with a pure single-elimination tournament system. Others have many phases, with the last being a single-elimination final stage, often called playoffs.

Spermatophyte

The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants. The term phanerogams or phanerogamae is derived from the Greek φανερός, phanerós meaning "visible", in contrast to the cryptogamae from Greek κρυπτός kryptós = "hidden" together with the suffix γαμέω, gameein, "to marry". These terms distinguished those plants with hidden sexual organs (cryptogamae) from those with visible sexual organs (phanerogamae).

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