Seed

Inbotany, aseedis a plantembryoand nutrient reserve enclosed in a seed coat, a protective outer covering called a testa. More generally, the term "seed" means anything that can besown, which may include seed andhuskortuber. Seeds are the product of the ripenedovule, after theembryo sacisfertilizedbyspermfrompollen, forming azygote. The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted.
The formation of the seed is the defining part of the process ofreproductionin seed plants (spermatophytes). Other plants such asferns,mossesandliverworts, do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biologicalnicheson land, fromforeststograsslandsboth in hot and coldclimates.
In theflowering plants, the ovary ripens into afruitwhich contains the seed and serves to disseminate it. Many structures commonly referred to as "seeds" are actually dry fruits. 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-calledstone fruits(such as thepeach) have a hardened fruit layer (theendocarp) fused to and surrounding the actual seed.Nutsare the one-seeded, hard-shelled fruit of some plants with anindehiscentseed, such as anacornorhazelnut.
Thefirst land plantsevolved around 468 million years ago,and reproduced using spores. The earliest seed bearing plants to appear were thegymnosperms, which have no ovaries to contain the seeds. They arose during the lateDevonianperiod (416 million to 358 million years ago).From these early gymnosperms,seed fernsevolved during theCarboniferousperiod (359 to 299 million years ago); they had ovules that were borne in a cupule,which consisted of groups of enclosing branches likely used to protect the developing seed.
Published literature about seed storage, viability and its hygrometric dependence began in the early 19th century, influential works being:
Angiosperm seeds are "enclosed seeds", produced in a hard or fleshy structure called a fruit that encloses them for protection. 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 theconescales as they develop in some species ofconifer.
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 withdouble fertilization, which involves the fusion of two male gametes with the egg cell and the central cell to form the primaryendospermand 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 aftergermination.
After fertilization, theovulesdevelop into the seeds. The ovule consists of a number of components:
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 calledanatropous, with a curved shape.Orthotropousovules are straight with all the parts of the ovule lined up in a long row producing an uncurved seed.Campylotropousovules have a curved megagametophyte often giving the seed a tight "C" shape. The last ovule shape is calledamphitropous, where the ovule is partly inverted and turned back 90 degrees on its stalk (the funicle orfuniculus).
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 ormicropylarpole 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.
The main components of the embryo are:
Monocotyledonous plants have two additional structures in the form of sheaths. The plumule is covered with acoleoptilethat forms the first leaf while the radicle is covered with acoleorhizathat connects to the primary root andadventitiousroots form 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.
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 thetegmenand the outer forms thetesta. (The seed coats of some monocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form apericarp.) 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 testae arehomologousfrom one species to the next. The funiculus abscisses (detaches at fixed point – abscission zone), the scar forming an oval depression, thehilum. Anatropous ovules have a portion of the funiculus that is adnate (fused to the seed coat), and which forms a longitudinal ridge, orraphe, just above the hilum. In bitegmic ovules (e.g.Gossypiumdescribed 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 becomestanniferous. The inner integument may consist of eight to fifteen layers.
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 calledpalisadecells. 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.
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.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 such aspineandspruce.
Seeds are very diverse, and as such there are many terms are used to describe them.
A typical seed includes two basic parts:
In addition, theendospermforms a supply of nutrients for the embryo in most monocotyledons and the endospermic dicotyledons.
Seeds have been considered to occur in many structurally different types (Martin 1946).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.
Six types occur amongst the monocotyledons, ten in the dicotyledons, and two in the gymnosperms (linear and spatulate).This classification is based on three characteristics: embryo morphology, amount of endosperm and the position of the embryo relative to the endosperm.
In endospermic seeds, there are two distinct regions inside the seed coat, an upper and larger endosperm and a lower smaller embryo. Theembryois the fertilised ovule, an immatureplantfrom which a new plant will grow under proper conditions. The embryo has onecotyledonor seed leaf inmonocotyledons, two cotyledons in almost alldicotyledonsand two or more in gymnosperms. In the fruit ofgrains(caryopses) the single monocotyledon is shield shaped and hence called ascutellum. 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.
Within the seed, there usually is a store ofnutrientsfor theseedlingthat 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 theendosperm, which is derived from the mother plant and the pollen viadouble fertilization. It is usuallytriploid, and is rich inoilorstarch, andprotein. In gymnosperms, such asconifers, the food storage tissue (also called endosperm) is part of the femalegametophyte, ahaploidtissue. The endosperm is surrounded by thealeuronelayer (peripheral endosperm), filled with proteinaceous aleurone grains.
Originally, by analogy with the animalovum, the outer nucellus layer (perisperm) was referred to asalbumen, 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 withstarch, as for instancecereal grains, or not (non-farinaceous). The endosperm may also be referred to as "fleshy" or "cartilaginous" with thicker soft cells such ascoconut, but may also be oily as inRicinus(castor oil),CrotonandPoppy. The endosperm is called "horny" when the cell walls are thicker such asdateandcoffee, or "ruminated"  if mottled, as innutmeg,palmsandAnnonaceae.
In most monocotyledons (such asgrassesandpalms) and some (endospermicoralbuminous) dicotyledons (such ascastor beans) the embryo is embedded in the endosperm (and nucellus), which the seedling will use upongermination. In thenon-endospermicdicotyledons 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 asexalbuminousseeds. The exalbuminous seeds include thelegumes(such asbeansandpeas), trees such as theoakandwalnut, vegetables such assquashandradish, andsunflowers. According to Bewley and Black (1978), Brazil nut storage is in hypocotyl and this place of storage is uncommon among seeds.All gymnosperm seeds are albuminous.
The seed coat develops from the maternal tissue, theinteguments, 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 inhoney locustandcoconut), or fleshy as in thesarcotestaofpomegranate. The seed coat helps protect the embryo from mechanical injury, predators, and drying out. Depending on its development, the seed coat is eitherbitegmicorunitegmic. 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 oflignifiedsclereids.
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 containingtanninand starch, and (c) inner epidermis.  Theendotegmenis derived from the inner epidermis of the inner integument, theexotegmenfrom the outer surface of the inner integument. Theendotestais 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 theexotesta. 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'.
In addition to the three basic seed parts, some seeds have an appendage, anaril, a fleshy outgrowth of the funicle (funiculus), (as inyewandnutmeg) or an oily appendage, anelaiosome(as inCorydalis), or hairs (trichomes). In the latter example these hairs are the source of the textile cropcotton. 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 thehilum, 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.
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 aremycoheterotrophswhich depend onmycorrhizal fungifor 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.At up to 55 pounds (25 kilograms)  the largest seed is thecoco de mer(Lodoicea maldivica).This indicates a 25 Billion fold difference in seed weight.  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 autumnal 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.
Seeds serve several functions for the plants that produce them.  Key among these functions are nourishment of theembryo,dispersalto a new location, anddormancyduring unfavorable conditions.  Seeds fundamentally are means of reproduction, and most seeds are the product ofsexual reproductionwhich produces a remixing of genetic material andphenotypevariability on whichnatural selectionacts. Plant seeds holdendophyticmicroorganisms that can perform various functions, the most important of which is protection against disease.
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.
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 todispersetheir offspring by dispersing their seeds (see alsovegetative 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 calleddehiscent, which is often distinctive for related groups of plants; these fruits includecapsules,follicles,legumes,siliclesandsiliques.  When fruits do not open and release their seeds in a regular fashion, they are called indehiscent, which include the fruitsachenes,caryopses,nuts,samaras, andutricles.
Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways:
Myrmecochoryis the dispersal of seeds byants. Foraging ants disperse seeds which have appendages calledelaiosomes(e.g.bloodroot,trilliums,acacias, and many species ofProteaceae).  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 ofmutualism, 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.  InSouth Africa, theArgentine ant(Linepithema humile) hasinvadedand displaced native species of ants.  Unlike the native ant species, Argentine ants do not collect the seeds ofMimetes cucullatusor eat the elaiosomes.  In areas where these ants have invaded, the numbers ofMimetesseedlings have dropped.
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).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: morphological, physiological, morphophysiological, physical, and combinational dormancy.
Exogenous dormancy is caused by conditions outside the embryo, including:
Endogenous dormancy is caused by conditions within the embryo itself, including:
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 (seeGermination):
Not all seeds undergo a period of dormancy.  Seeds of somemangrovesare 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.
Forannuals, 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 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.
Far red light can prevent 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 vigoris 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.
Thegermination percentageis simply the proportion of seeds that germinate from all seeds subject to the right conditions for growth. Thegermination rateis 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 affecting seed germination include; water, oxygen, temperature and light.
Three distinct phases of seed germination occur: water imbibition; lag phase; andradicleemergence.
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 initiategermination. 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.
During seeddormancy, often associated with unpredictable and stressful environments,DNA damageaccumulates as the seeds age.Inryeseeds, the reduction of DNA integrity due to damage is associated with loss of seed viability during storage.Upon germination, seeds ofVicia fabaundergoDNA repair.A plant DNAligasethat is involved in repair of single- and double-strand breaks during seed germination is an important determinant of seed longevity.Also, inArabidopsisseeds, the activities of the DNA repair enzymesPoly ADP ribose polymerases(PARP) are likely needed for successful germination.Thus DNA damages that accumulate duringdormancyappear to be a problem for seed survival, and the enzymatic repair of DNA damages during germination appears to be important for seed viability.
A number of different strategies are used by gardeners and horticulturists to breakseed dormancy.
Scarificationallows 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 fromdigestion, 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.Microorganismsare 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.
Leachingor the soaking in water removes chemical inhibitors in some seeds that prevent germination.Rainand meltingsnownaturally 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.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.
Seeds may be sterile for few reasons: they may have been irradiated, unpollinated, cells lived past expectancy, or bred for the purpose.
The issue of the origin of seed plants remains unsolved. However, more and more data tends to place this origin in the middleDevonian. The description in 2004 of the proto-seedRuncaria heinzeliniiin theGivetianofBelgiumis an indication of that ancient origin of seed-plants. As with modern ferns, most land plants before this time reproduced by sending into the airsporesthat would land and become whole new plants.
Taxonomists have described early "true" seeds from the upper Devonian, which probably became the theater of their true firstevolutionary radiation. With this radiation came anevolution of seed size, shape, dispersal and eventually the radiation of gymnosperms and angiosperms andmonocotyledonsanddicotyledons. Seed plants progressively became one of the major elements of nearly all ecosystems.
Also called growing true, refers to plants whose seed will yield the same type of plant as the original plant. Open pollinated plants, which include heirlooms, will almost always grow true to seed if another variety does not cross-pollinate them.
Seeds harbor a diverse microbial community.Most of these microorganisms are transmitted from the seed to the developing seedlings.
In the United States farmers spent $22 billion on seeds in 2018, a 35 percent increase since 2010.DowDuPontandMonsantoaccount for 72 percent of corn and soybean seed sales in the U.S. with the average price of a bag of GMOcornseed is priced at $270.
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 ofloblolly pineandshortleaf pineproduced from 0 to nearly 5.5 million sound pine seeds per hectare.Over this period, there were six bumper, five poor, and nine good seed crops, when evaluated for production of adequateseedlingsfor natural forest reproduction.
Many seeds are edible and the majority of human calories comes from seeds,especially fromcereals,legumesandnuts. Seeds also provide mostcooking oils, manybeveragesandspicesand some importantfood additives.  In different seeds theseed embryoor theendospermdominates and provides most of thenutrients. The storageproteinsof the embryo and endosperm differ in theiramino acidcontent and physical properties.  For example, theglutenof wheat, important in providing theelasticproperty to breaddoughis strictly an endosperm protein.
Seeds are used to propagate many crops such as cereals, legumes,forest trees,turfgrasses, andpasturegrasses. 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 animals (seed predation), and are also fed tolivestockor provided asbirdseed.
While some seeds are edible, others are harmful, poisonous or deadly.Plants and seeds often containchemical compoundsto discourageherbivoresandseed predators.  In some cases, these compounds simply taste bad (such as inmustard), but other compounds are toxic or break down into toxic compounds within thedigestive system.  Children, being smaller than adults, are more susceptible to poisoning by plants and seeds.
A deadly poison,ricin, comes from seeds of thecastor 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 containingamygdalin–apple,apricot,bitter almond,peach,plum,cherry,quince, and others – when consumed in sufficient amounts, may causecyanide poisoning.Other seeds that contain poisons includeannona,cotton,custard apple,datura, uncookeddurian,golden chain,horse-chestnut,larkspur,locoweed,lychee,nectarine,rambutan,rosary pea,sour sop,sugar apple,wisteria, andyew.The seeds of thestrychnine treeare also poisonous, containing the poisonstrychnine.
The seeds of many legumes, including the common bean (Phaseolus vulgaris), contain proteins calledlectinswhich can cause gastric distress if the beans are eaten withoutcooking.  The common bean and many others, including thesoybean, also containtrypsin inhibitorswhich interfere with the action of the digestive enzymetrypsin.  Normal cooking processes degrade lectins and trypsin inhibitors to harmless forms.
Cottonfibergrows attached tocotton plantseeds. Other seed fibers are fromkapokandmilkweed.
Many important nonfood oils are extracted from seeds.Linseed oilis used in paints. Oil fromjojobaandcrambeare similar towhale oil.
Seeds are the source of some medicines includingcastor oil,tea tree oiland the quack cancer drugLaetrile.
Many seeds have been used asbeadsin necklaces and rosaries includingJob's tears,Chinaberry,rosary pea, andcastor bean. However, the latter three are also poisonous.
Other seed uses include:
TheBook of Genesisin the Old Testament begins with an explanation of how all plant forms began:
TheQuranspeaks of seed germination thus: