Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propagated using the movements of humans and other animals in asymbiotic relationship that is the means forseed dispersal for the one group andnutrition for the other; humans, and many other animals, have become dependent on fruits as a source of food.[1] Consequently, fruits account for a substantial fraction of the world'sagricultural output, and some (such as theapple and thepomegranate) have acquired extensive cultural and symbolic meanings.
In common language and culinary usage,fruit normally means the seed-associated fleshy structures (or produce) of plants that typically are sweet (or sour) and edible in the raw state, such as apples, bananas, grapes, lemons, oranges, and strawberries. In botanical usage, the termfruit also includes many structures that are not commonly called as such in everyday language, such as nuts, bean pods, corn kernels, tomatoes, and wheat grains.[2][3]
An arrangement of fruits commonly thought of as culinary vegetables, includingcorn (maize),tomatoes, and varioussquash
Many common language terms used for fruit and seeds differ from botanical classifications. For example, in botany, afruit is a ripenedovary orcarpel that contains seeds, e.g., an orange, pomegranate, tomato or a pumpkin. Anut is a type of fruit (and not a seed), and aseed is a ripenedovule.[4]
In culinary language, afruit is the sweet- or not sweet- (even sour-) tasting produce of a specific plant (e.g., a peach, pear or lemon);nuts are hard, oily, non-sweet plant produce in shells (hazelnut,acorn).Vegetables, so-called, typically aresavory or non-sweet produce (zucchini, lettuce, broccoli, and tomato). but some may be sweet-tasting (sweet potato).[5]
Botanically, acereal grain, such ascorn,rice, orwheat is a kind of fruit (termed acaryopsis). However, the fruit wall is thin and fused to the seed coat, so almost all the edible grain-fruit is actually a seed.[7]
Pomegranate fruit – whole and piece with arilsFruit platter – seasonal fruits
The outer layer, often edible, of most fruits is called thepericarp. Typically formed from the ovary, it surrounds the seeds; in some species, however, other structural tissues contribute to or form the edible portion. The pericarp may be described in three layers from outer to inner, i.e., theepicarp,mesocarp andendocarp.
Fruit that bears a prominent pointed terminal projection is said to bebeaked.[8]
Development
A fruit results from the fertilizing and maturing of one or more flowers. Thegynoecium, which contains thestigma-style-ovary system, is centered in the flower-head, and it forms all or part of the fruit.[9] Inside theovary(ies) are one or moreovules. Here begins a complex sequence calleddouble fertilization: a femalegametophyte produces an egg cell for the purpose of fertilization.[10] (A female gametophyte is called amegagametophyte, and also called theembryo sac.) After double fertilization, the ovules will become seeds.
Ovules are fertilized in a process that starts withpollination, which is the movement of pollen from the stamens to the stigma-style-ovary system within the flower-head. After pollination, apollen tube grows from the (deposited) pollen through the stigma down the style into the ovary to the ovule. Two sperm are transferred from the pollen to a megagametophyte. Within the megagametophyte, one sperm unites with the egg, forming azygote, while the second sperm enters the central cell forming the endosperm mother cell, which completes the double fertilization process.[11][12] Later, the zygote will give rise to the embryo of the seed, and the endosperm mother cell will give rise toendosperm, a nutritive tissue used by the embryo.
Fruit formation is associated withmeiosis, a central aspect ofsexual reproduction in flowering plants. During meiosishomologous chromosomes replicate,recombine and randomly segregate, and then undergo segregation ofsister chromatids to producehaploid cells.[13] Union of haploid nuclei frompollen andovule (fertilisation), occurring either byself- or cross-pollination, leads to the formation of a diploidzygote that can then develop into anembryo within the emerging seed. Repeated fertilisations within theovary are accompanied by maturation of the ovary to form the fruit.
As the ovules develop into seeds, the ovary begins to ripen and the ovary wall, thepericarp, may become fleshy (as in berries ordrupes), or it may form a hard outer covering (as in nuts). In some multi-seeded fruits, the extent to which a fleshy structure develops is proportional to the number of fertilized ovules.[14] The pericarp typically is differentiated into two or three distinct layers; these are called theexocarp (outer layer, also called epicarp),mesocarp (middle layer), andendocarp (inner layer).
In some fruits, thesepals,petals,stamens orthe style of the flower fall away as the fleshy fruit ripens. However, for simple fruits derived from aninferior ovary – i.e., one that liesbelow the attachment of other floral parts – there are parts (including petals, sepals, and stamens) that fuse with the ovary and ripen with it. For such a case, when floral parts other than the ovary form a significant part of the fruit that develops, it is called anaccessory fruit. Examples of accessory fruits include apple, rose hip, strawberry, and pineapple.
Because several parts of the flower besides the ovary may contribute to the structure of a fruit, it is important to understand how a particular fruit forms.[3] There are three general modes of fruit development:
Apocarpous fruits develop from asingle flower (while having one or more separate, unfused, carpels); they are thesimple fruits.
Syncarpous fruits develop from asinglegynoecium (having two or more carpels fused together).
Multiple fruits form from many flowers – i.e., an inflorescence of flowers.
The development sequence of a typicaldrupe, thenectarine (Prunus persica) over a 7.5-month period, from bud formation in early winter to fruitripening in midsummer
The parts of a flower, showing the stigma-style-ovary system.
An apple is a simple, fleshy fruit. Key parts are the epicarp, or exocarp, or outer skin (not labelled); and the mesocarp and endocarp (labelled).
Insertion point: There are three positions of insertion of the ovary at the base of a flower: I superior; II half-inferior; III inferior. The 'insertion point' is where theandroecium parts (a), the petals (p), and the sepals (s) all converge and attach to the receptacle (r). (Ovary=gynoecium (g).)
In thenoni, flowers are produced in time-sequence along the stem. It is possible to see a progression of flowering, fruit development, and fruit ripening.
Twin apples
Classification of fruits
Dewberry flowers. Note the multiplepistils, each of which will produce adrupelet. Each flower will become a blackberry-likeaggregate fruit.Dewberry fruit
Consistent with the three modes of fruit development, plant scientists have classified fruits into three main groups: simple fruits, aggregate fruits, and multiple (or composite) fruits.[15] The groupings reflect how the ovary and other flower organs are arranged and how the fruits develop, but they are not evolutionarily relevant as diverse planttaxa may be in the same group.
Simple fruits are the result of the ripening-to-fruit of a simple or compound ovary in asingle flower with asinglepistil. In contrast, a single flower with numerous pistils typically produces anaggregate fruit; and the merging of several flowers, or a 'multiple' of flowers, results in a 'multiple' fruit.[17] A simple fruit is further classified as either dry or fleshy.
To distribute their seeds, dry fruits may split open and discharge their seeds to the winds, which is calleddehiscence.[18] Or the distribution process may rely upon the decay and degradation of the fruit to expose the seeds; or it may rely upon the eating of fruit and excreting of seeds byfrugivores – both are calledindehiscence. Fleshy fruits do not split open, but they also are indehiscent and they may also rely on frugivores for distribution of their seeds. Typically, the entire outer layer of the ovary wall ripens into a potentially ediblepericarp.
Types of dry simple fruits, (with examples) include:
Achene – most commonly seen in aggregate fruits (e.g.,strawberry, see below).
Fruits in which part or all of thepericarp (fruit wall) is fleshy at maturity are termedfleshy simple fruits.
Types of fleshy simple fruits, (with examples) include:
Berry – the berry is the most common type of fleshy fruit. The entire outer layer of the ovary wall ripens into a potentially edible "pericarp", (see below).
Stone fruit or drupe – the definitive characteristic of a drupe is the hard, "lignified" stone (sometimes called the "pit"). It is derived from the ovary wall of the flower:apricot,cherry,olive,peach,plum,mango.
Fruits of four differentbanana cultivars. (Bananas are berries.)Strawberry, showing achenes attached to surface. Botanically, strawberries are not berries; they are classified as anaggregateaccessory fruit.Flower ofMagnolia ×wieseneri showing the many pistils making up thegynoecium in the middle of the flower. The fruit of this flower is an aggregation of follicles.
Berries are a type of simple fleshy fruit that issue from a single ovary.[20] (The ovary itself may be compound, with several carpels.) The botanical termtrue berry includes grapes, currants, cucumbers, eggplants (aubergines), tomatoes, chili peppers, and bananas, but excludes certain fruits that are called "-berry" by culinary custom or by common usage of the term – such as strawberries and raspberries. Berries may be formed from one or more carpels (i.e., from the simple or compound ovary) from the same, single flower. Seeds typically are embedded in the fleshy interior of the ovary.
Examples include:
Tomato – in culinary terms, the tomato is regarded as a vegetable, but it is botanically classified as a fruit and a berry.[21]
Banana – the fruit has been described as a "leathery berry".[22] In cultivated varieties, the seeds are diminished nearly to non-existence.
Pepo – berries with skin that is hardened:cucurbits, including gourds, squash, melons.
Hesperidium – berries with a rind and a juicy interior: mostcitrus fruit.
The strawberry, regardless of its appearance, is classified as a dry, not a fleshy fruit. Botanically, it is not aberry; it is anaggregate-accessory fruit, the latter term meaning the fleshy part is derived not from the plant's ovaries but from thereceptacle that holds theovaries.[23] Numerous dryachenes are attached to the outside of the fruit-flesh; they appear to be seeds but each is actually an ovary of a flower, with a seed inside.[23]
Schizocarps are dry fruits, though some appear to be fleshy. They originate from syncarpous ovaries but do not actuallydehisce; rather, they split into segments with one or more seeds. They include a number of different forms from a wide range of families, includingcarrot,parsnip,parsley,cumin.[15]
Detail of the raspberry flower: there is a clustering of pistils at the center of the flower. (A pistil consists of stigma, style, and ovary.) Thestigma is the apical (at the apex) nodule that receives pollen; thestyle is the stem-like column that extends down to theovary, which is the basal part that contains the seed-formingovule.Lilium unripe capsule fruit; an aggregate fruit
An aggregate fruit is also called an aggregation, oretaerio; it develops from a single flower that presents numerous simplepistils.[17] Each pistil contains onecarpel; together, they form a fruitlet. The ultimate (fruiting) development of the aggregation of pistils is called anaggregate fruit,etaerio fruit, or simply anetaerio.
Different types of aggregate fruits can produce different etaerios, such as achenes, drupelets, follicles, and berries.
For example, the Ranunculaceae species, includingClematis andRanunculus, produces an etaerio ofachenes;
Rubus species, including raspberry: an etaerio ofdrupelets;
The pistils of theraspberry are calleddrupelets because each pistil is like a smalldrupe attached to the receptacle. In somebramble fruits, such asblackberry, the receptacle, an accessory part, elongates and then develops as part of the fruit, making the blackberry anaggregate-accessory fruit.[26] The strawberry is also an aggregate-accessory fruit, of which the seeds are contained in theachenes.[27] Notably in all these examples, the fruit develops from a single flower, with numerous pistils.
A multiple fruit is formed from a cluster of flowers, (a 'multiple' of flowers) – also called aninflorescence. Each ('smallish') flower produces a single fruitlet, which, as all develop, all merge into one mass of fruit.[28] Examples includepineapple,fig,mulberry,Osage orange, andbreadfruit. An inflorescence (a cluster) of white flowers, called a head, is produced first. Afterfertilization, each flower in the cluster develops into a drupe; as the drupes expand, they develop as aconnate organ, merging into a multiple fleshy fruit called asyncarp.
Progressive stages of multiple flowering and fruit development can be observed on a single branch of the Indian mulberry, ornoni. During the sequence of development, a progression of second, third, and more inflorescences are initiated in turn at the head of the branch or stem.
Fruits may incorporate tissues derived from other floral parts besides the ovary, including the receptacle, hypanthium, petals, or sepals. Accessory fruits occur in all three classes of fruit development – simple, aggregate, and multiple. Accessory fruits are frequently designated by the hyphenated term showing both characters. For example, a pineapple is a multiple-accessory fruit, a blackberry is an aggregate-accessory fruit, and an apple is a simple-accessory fruit.
Seedlessness is an important feature of some fruits of commerce. Commercialcultivars of bananas and pineapples are examples ofseedless fruits. Some cultivars ofcitrus fruits (especiallygrapefruit,mandarin oranges,navel oranges,satsumas),table grapes, and ofwatermelons are valued for their seedlessness. In some species, seedlessness is the result ofparthenocarpy, where fruits set without fertilization. Parthenocarpic fruit-set may (or may not) require pollination, but most seedless citrus fruits require a stimulus from pollination to produce fruit.[29] Seedless bananas and grapes aretriploids, and seedlessness results from the abortion of theembryonic plant that is produced by fertilization, a phenomenon known asstenospermocarpy, which requires normal pollination and fertilization.[30]
Seed dissemination
Variations in fruit structures largely depend on themodes of dispersal applied to their seeds. Dispersal is achieved by wind or water, byexplosive dehiscence, and by interactions with animals.[31]
Some fruits present their outer skins or shells coated with spikes or hooked burrs; these evolved either to deter would-be foragers from feeding on them or to serve to attach themselves to the hair, feathers, legs, or clothing of animals, thereby using them as dispersal agents. These plants are termedzoochorous; common examples includecocklebur,unicorn plant, andbeggarticks (or Spanish needle).[32][33]
By developments of mutual evolution, the fleshy produce of fruits typically appeals to hungry animals, such that the seeds contained within are taken in, carried away, and later deposited (i.e.,defecated) at a distance from the parent plant. Likewise, the nutritious, oily kernels ofnuts typically motivate birds andsquirrels tohoard them, burying them in soil to retrieve later during the winter of scarcity; thereby, uneaten seeds are sown effectively under natural conditions togerminate and grow a new plant some distance away from the parent.[4]
Other fruits have evolved flattened and elongated wings or helicopter-like blades, e.g.,elm,maple, andtuliptree. This mechanism increases dispersal distance away from the parent via wind. Other wind-dispersed fruit have tiny "parachutes", e.g.,dandelion,milkweed,salsify.[31]
Coconut fruits can float thousands of miles in the ocean, thereby spreading their seeds. Other fruits that can disperse via water arenipa palm andscrew pine.[31]
Some fruits have evolved propulsive mechanisms that fling seeds substantial distances – perhaps up to 100 m (330 ft) in the case of thesandbox tree – via explosive dehiscence or other such mechanisms (seeimpatiens andsquirting cucumber).[34]
A selection of fruit for sale in a market in FrancePicking blackberries inOklahoma
A large variety of fruits – fleshy (simple) fruits from apples to berries to watermelon; dry (simple) fruits including beans and rice and coconuts; aggregate fruits including strawberries, raspberries, blackberries, pawpaw; and multiple fruits such as pineapple, fig, mulberries – are commercially valuable as human food. They are eaten both fresh and as jams, marmalade and otherfruit preserves. They are used extensively in manufactured and processed foods (cakes, cookies, baked goods, flavorings, ice cream, yogurt, canned vegetables, frozen vegetables and meals) and beverages such as fruit juices andalcoholic beverages (brandy,fruit beer, wine).[35] Spices like vanilla, black pepper, paprika, andallspice are derived from berries.Olive fruit is pressed forolive oil and similar processing is applied to other oil-bearing fruits and vegetables.[36] Some fruits are available all year round, while others (such as blackberries and apricots in the UK) are subject toseasonal availability.[37]
Typically, many botanical fruits – "vegetables" in culinary parlance – (including tomato, green beans, leaf greens, bell pepper, cucumber, eggplant, okra, pumpkin, squash, zucchini) are bought and sold daily in fresh produce markets andgreengroceries and carried back to kitchens, at home or restaurant, for preparation of meals.[40]
Storage
All fruits benefit from proper post-harvest care, and in many fruits, the plant hormoneethylene causesripening. Therefore, maintaining most fruits in an efficientcold chain is optimal for post-harvest storage, with the aim of extending and ensuring shelf life.[41]
Nutritional value
Comparing fresh fruits for fiber, potassium (K), and vitamin C.[citation needed] Each disk-point refers to a 100 g (3.5 oz) serving of the fresh fruit named. The size of the disk represents the amount of fiber (as percentage of therecommended daily allowance, RDA) in a serving of fruit (see key at upper right). The amount of vitamin C (as percent RDA) is plotted on the x–axis and the amount of potassium (K), in mg on the y–axis. Bananas are high in value for fiber and potassium, and oranges for fiber and vitamin C. (Apricots are highest in potassium; strawberries are rich in vitamin C.) Watermelon, providing low levels of both K and vitamin C and almost no fiber, is of least value for the threenutrients together.
Various culinary fruits provide significant amounts offiber and water, and many are generally high invitamin C.[43] An overview of numerous studies showed that fruits (e.g., whole apples or whole oranges) are satisfying (filling) by simply eating and chewing them.[44]
The dietary fiber consumed in eating fruit promotessatiety, and may help to control body weight and aid reduction of bloodcholesterol, arisk factor forcardiovascular diseases.[45] Fruit consumption is under preliminary research for the potential to improve nutrition and affect chronic diseases.[46][47] Regular consumption of fruit is generally associated with reduced risks of several diseases and functional declines associated with aging.[48][49][50]
Food safety
Forfood safety, theCDC recommends proper fruit handling and preparation to reduce the risk offood contamination andfoodborne illness. Fresh fruits and vegetables should be carefully selected; at the store, they should not be damaged or bruised; and precut pieces should be refrigerated or surrounded by ice.
All fruits and vegetables should be rinsed before eating. This recommendation also applies to produce with rinds or skins that are not eaten. It should be done just before preparing or eating to avoid premature spoilage.
Fruits and vegetables should be kept separate from raw foods like meat, poultry, and seafood, as well as from utensils that have come in contact with raw foods. Fruits and vegetables that are not going to be cooked should be thrown away if they have touched raw meat, poultry, seafood, or eggs.
All cut, peeled, or cooked fruits and vegetables should be refrigerated within two hours. After a certain time, harmful bacteria may grow on them and increase the risk of foodborne illness.[51]
Allergies
Fruit allergies make up about 10 percent of all food-related allergies.[52][53]
Because fruits have been such a major part of the human diet, various cultures have developed many different uses for fruits they do not depend on for food. For example:
Bayberry fruits provide a wax often used to make candles;[55]
Fruits ofopium poppy are the source ofopium, which contains the drugscodeine andmorphine, as well as the biologically inactive chemical theabaine from which the drugoxycodone is synthesized.[57]
Coir fiber fromcoconut shells is used for brushes, doormats, floor tiles, insulation, mattresses, sacking, and as a growing medium for container plants. The shell of the coconut fruit is used to make bird houses, bowls, cups, musical instruments, and souvenir heads.[63]
The hard and colorful grain fruits ofJob's tears are used as decorative beads for jewelry, garments, and ritual objects.[64]
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^Yip, Cynthia Sau Chun; Chan, Wendy; Fielding, Richard (March 2019). "The Associations of Fruit and Vegetable Intakes with Burden of Diseases: A Systematic Review of Meta-Analyses".Journal of the Academy of Nutrition and Dietetics.119 (3):464–481.doi:10.1016/j.jand.2018.11.007.ISSN2212-2672.PMID30639206.S2CID58628014.
^Nathaniel Hawthorne, "The Great Carbuncle", inTwice-Told Tales, 1837: Hide it [the great carbuncle] under thy cloak, say'st thou? Why, it will gleam through the holes, and make thee look like a jack-o'-lantern!
