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66-741: Testa may refer to: [REDACTED] Look up testa in Wiktionary, the free dictionary. Testa (botany) , a term to describe the seed coat Testa (surname) Testa, Zanskar , a village in Ladakh , India Testa, Hurwitz & Thibeault , a former Boston law firm 11667 Testa , a main-belt asteroid discovered in 1997 Testa (ceramics) , fired clay material, especially crushed brick used in mortar Trans European Services for Telematics between Administrations Trebatius Testa (fl. 1st century BC), jurist of ancient Rome Tesch & Stabenow ,

132-489: 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 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

198-539: A German chemical company notable for its role in the Holocaust See also [ edit ] Head (disambiguation) , testa being the Italian word for head Testarossa (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Testa . If an internal link led you here, you may wish to change the link to point directly to

264-422: 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

330-411: 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

396-467: A fruit having the structure and texture of a drupe, but which does not precisely fit the definition of a drupe. The boundary between a drupe and a berry is not always clear. Thus, some sources describe the fruit of species from the genus Persea , which includes the avocado , as a drupe, others describe avocado fruit as a berry. One definition of berry requires the endocarp to be less than 2 mm ( 3 ⁄ 32  in) thick, other fruits with

462-427: 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 . The first land plants evolved around 468 million years ago, and reproduced using spores. The earliest seed bearing plants to appear were the gymnosperms , which have no ovaries to contain the seeds. They arose during

528-415: 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

594-416: A seed coat, a protective outer covering called a testa. More generally, the term "seed" means anything that can be sown , which may include seed and husk or tuber . Seeds are the product of the ripened ovule , after the embryo sac is fertilized by sperm from pollen , forming a zygote . The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth

660-420: A stony endocarp being drupes. In marginal cases, terms such as drupaceous or drupe-like may be used. The term stone fruit (also stonefruit ) can be a synonym for drupe or, more typically, it can mean just the fruit of the genus Prunus . Freestone refers to a drupe having a stone which can be removed from the flesh with ease. The flesh is not attached to the stone and does not need to be cut to free

726-435: 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

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792-550: 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 . 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

858-405: 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

924-509: 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

990-481: 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 (see Germination ): Not all seeds undergo a period of dormancy. Seeds of some mangroves are viviparous; they begin to germinate while still attached to

1056-402: 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

1122-404: Is halted. The formation of the seed is the defining part of the process of reproduction in seed plants ( spermatophytes ). Other plants such as ferns , mosses and liverworts , 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 . In the flowering plants ,

1188-431: Is known as scarification . Typical drupes include apricots , olives , loquat , peaches , plums , cherries , mangoes , pecans , and amlas (Indian gooseberries). Other examples include sloe ( Prunus spinosa ) and ivy ( Hedera helix ). The coconut is also a drupe, but the mesocarp is fibrous or dry (termed a husk ), so this type of fruit is classified as a simple dry, fibrous drupe. Unlike other drupes,

1254-444: 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

1320-535: 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 to disperse their offspring by dispersing their seeds (see also vegetative reproduction ). A seed must somehow "arrive" at

1386-446: 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

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1452-411: 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 as pine and spruce . 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, the endosperm forms

1518-419: 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 )

1584-417: The cone scales as they develop in some species of conifer . 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

1650-412: 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. Plant seeds hold endophytic microorganisms that can perform various functions, the most important of which

1716-424: 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 and this place of storage is uncommon among seeds. All gymnosperm seeds are albuminous. The seed coat develops from the maternal tissue, the integuments , originally surrounding the ovule. The seed coat in

1782-402: The ovary wall of the flower . In an aggregate fruit , which is composed of small, individual drupes (such as a raspberry ), each individual is termed a drupelet , and may together form an aggregate fruit. Such fruits are often termed berries , although botanists use a different definition of berry . Other fleshy fruits may have a stony enclosure that comes from the seed coat surrounding

1848-459: The attention of animals as a food , and the plant population benefits from the resulting dispersal of its seeds . The endocarp (pit or stone) is sometimes dropped after the fleshy part is eaten, but is often swallowed, passing through the digestive tract , and returned to the soil in feces with the seed inside unharmed. This passage through the digestive tract can reduce the thickness of the endocarp, thus can aid in germination rates. The process

1914-636: 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 . In most monocotyledons (such as grasses and palms ) and some ( endospermic or albuminous ) dicotyledons (such as castor beans )

1980-405: 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

2046-558: The coconut seed is so large that it is unlikely to be dispersed by being swallowed by fauna , but it can float extremely long distances—across oceans. Bramble fruits such as the blackberry and the raspberry are aggregates of drupelets. The fruit of blackberries and raspberries comes from a single flower whose pistil is made up of a number of free carpels. However, mulberries , which closely resemble blackberries, are not aggregate fruit, but are multiple fruits , actually derived from bunches of catkins , each drupelet thus belonging to

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2112-407: 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

2178-440: The elaiosomes are eaten. The remainder of the seed, which is hard and inedible to the ants, then germinates either within the nest or at a removal site where the seed has been discarded by the ants. This dispersal relationship is an example of mutualism , since the plants depend upon the ants to disperse seeds, while the ants depend upon the plants seeds for food. As a result, a drop in numbers of one partner can reduce success of

2244-429: 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

2310-452: 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

2376-645: 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 the coco 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 autumn all blooming plants often have small seeds. Many annual plants produce great quantities of smaller seeds; this helps to ensure at least

2442-507: The fruits achenes , caryopses , nuts , samaras , and utricles . Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways: Myrmecochory is the dispersal of seeds by ants . Foraging ants disperse seeds which have appendages called elaiosomes (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

2508-408: 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 . After fertilization, the ovules develop into

2574-446: The grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp .) 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 are homologous from one species to the next. The funiculus abscisses (detaches at fixed point – abscission zone),

2640-431: The growing parts. Embryo descriptors include small, straight, bent, curved, and curled. 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

2706-434: 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. 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

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2772-444: 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

2838-406: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Testa&oldid=1237146698 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Testa (botany) In botany , a seed is a plant embryo and nutrient reserve enclosed in

2904-478: The late Devonian period (416 million to 358 million years ago). From these early gymnosperms, seed ferns evolved during the Carboniferous period (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

2970-424: 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

3036-402: 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. The main components of the embryo are: Monocotyledonous plants have two additional structures in the form of sheaths. The plumule is covered with

3102-422: 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

3168-514: 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, 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

3234-456: 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 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

3300-399: 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. The embryo is

3366-403: 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

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3432-477: 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. Seed dormancy has two main functions: the first is synchronizing germination with

3498-415: The ovary ripens into a fruit which 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-called stone fruits (such as the peach ) have

3564-410: 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

3630-455: 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 the tegmen and the outer forms the testa . (The seed coats of some monocotyledon plants, such as

3696-405: 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

3762-415: The scar forming an oval depression, the hilum . Anatropous ovules have a portion of the funiculus 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. Gossypium described here) both inner and outer integuments contribute to the seed coat formation. With continuing maturation the cells enlarge in the outer integument. While

3828-413: 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

3894-399: The seed, but such fruits are not drupes. Flowering plants that produce drupes include coffee , jujube , mango , olive , most palms (including açaí , date , sabal and oil palms ), pistachio , white sapote , cashew , and all members of the genus Prunus , including the almond , apricot , cherry , damson , peach , nectarine , and plum . The term drupaceous is applied to

3960-411: 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. Stone fruits The definitive characteristic of a drupe is that the hard, woody ( lignified ) stone is derived from

4026-405: 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 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

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4092-420: 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

4158-642: The stone and must be cut to free the stone. Clingstone varieties of fruits in the genus Prunus are preferred as table fruit and for jams, because the flesh of clingstone fruits tends to be more tender and juicy throughout. Tryma is a specialized term for such nut -like drupes that are difficult to categorize. Hickory nuts ( Carya ) and walnuts ( Juglans ) in the Juglandaceae family grow within an outer husk; these fruits are technically drupes or drupaceous nuts, thus are not true botanical nuts . Many drupes, with their sweet, fleshy outer layer, attract

4224-419: The stone. Freestone varieties of fruits are preferred for uses that require careful removal of the stone, especially if removal will be done by hand. Freestone plums are preferred for making homegrown prunes , and freestone sour cherries are preferred for making pies and cherry soup . Clingstone refers to a drupe having a stone which cannot be easily removed from the flesh. The flesh is attached strongly to

4290-507: The strength of the seedlings produced. The germination percentage is simply the proportion of seeds that germinate from all seeds subject to the right conditions for growth. The germination rate is the length of time it takes for the seeds to germinate. Germination percentages and rates are affected by seed viability, dormancy and environmental effects that impact on the seed and seedling. In agriculture and horticulture quality seeds have high viability, measured by germination percentage plus

4356-426: 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

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