Fruits are the means by which flowering plants (also known as
angiosperms) disseminate their
seeds. Edible fruits in particular have long propagated using the movements of humans and other animals in a
symbiotic relationship that is the means for
seed dispersal for the one group and
nutrition 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'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 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 term fruit also includes many structures that are not commonly called 'fruits' 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, including
corn (maize),
tomatoes, and various
squash
Many common language terms used for fruit and seeds differ from botanical classifications. For example, in botany, a fruit is a ripened
ovary or
carpel that contains seeds, e.g., an orange, pomegranate, tomato or a pumpkin. A nut is a type of fruit (and not a seed), and a seed is a ripened
ovule.[4]
In culinary language, a
fruit 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 are
savory or non-sweet produce (
zucchini, lettuce, broccoli, and tomato). but some may be sweet-tasting (sweet potato).[5]
Botanically, a
cereal grain, such as
corn,
rice, or
wheat is a kind of fruit (termed a
caryopsis). However, the fruit wall is thin and fused to the seed coat, so almost all the edible grain-fruit is actually a seed.[7]
The outer layer, often edible, of most fruits is called the pericarp. 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., the epicarp, mesocarp and endocarp.
Fruit that bears a prominent pointed terminal projection is said to be beaked.[8]
Development
A fruit results from the fertilizing and maturing of one or more flowers. The
gynoecium, which contains the stigma-style-ovary system, is centered in the flower-head, and it forms all or part of the fruit.[9] Inside the
ovary(ies) are one or more
ovules. Here begins a complex sequence called double fertilization: a female
gametophyte produces an egg cell for the purpose of fertilization.[10] (A female gametophyte is called a megagametophyte, and also called the embryo sac.) After double fertilization, the ovules will become seeds.
Ovules are fertilized in a process that starts with
pollination, which is the movement of pollen from the stamens to the stigma-style-ovary system within the flower-head. After pollination, a
pollen 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 a
zygote, 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 to
endosperm, a nutritive tissue used by the embryo.
As the ovules develop into seeds, the ovary begins to ripen and the ovary wall, the pericarp, may become fleshy (as in berries or
drupes), 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.[13] The pericarp typically is differentiated into two or three distinct layers; these are called the exocarp (outer layer, also called epicarp), mesocarp (middle layer), and endocarp (inner layer).
In some fruits, the
sepals,
petals,
stamens and/or
the style of the flower fall away as the fleshy fruit ripens. However, for simple fruits derived from an inferior ovary – i.e., one that lies below 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 an
accessory 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 a single flower (while having one or more separate, unfused, carpels); they are the
simple fruits.
Syncarpous fruits develop from a single
gynoecium (having two or more carpels fused together).
Multiple fruits form from many flowers – i.e., an inflorescence of flowers.
The development sequence of a typical
drupe, the
nectarine (Prunus persica) over a 7.5-month period, from bud formation in early winter to fruit
ripening 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 the
androecium parts (a), the petals (p), and the sepals (s) all converge and attach to the receptacle (r). (Ovary=gynoecium (g).)
In the
noni, 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 multiple
pistils, each of which will produce a
drupelet. Each flower will become a blackberry-like
aggregate 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.[14] 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 plant
taxa may be in the same group.
Simple fruits are the result of the ripening-to-fruit of a simple or compound ovary in a single flower with a single
pistil. In contrast, a single flower with numerous pistils typically produces an
aggregate fruit; and the merging of several flowers, or a 'multiple' of flowers, results in a 'multiple' fruit.[16] 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 called
dehiscence.[17] 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 by
frugivores – both are called
indehiscence. 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 edible
pericarp.
Types of dry simple fruits, (with examples) include:
Achene – most commonly seen in aggregate fruits (e.g.,
strawberry, see below).
Follicle – follicles are formed from a single carpel, and opens by one suture: (
milkweed); also commonly seen in aggregate fruits: (
magnolia,
peony).
Legume – (
bean,
pea,
peanut: botanically, the peanut is the seed of a legume, not a nut).
Fruits in which part or all of the
pericarp (fruit wall) is fleshy at maturity are termed fleshy 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 different
banana cultivars (Bananas are berries.)Strawberry, showing achenes attached to surface. Botanically, strawberries are not berries; they are classified as an
aggregateaccessory fruit.Flower of
Magnolia × wieseneri showing the many pistils making up the
gynoecium 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.[19] (The ovary itself may be compound, with several carpels.) The botanical term true 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.[20]
Banana – the fruit has been described as a "leathery berry".[21] 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: most
citrus fruit.
The strawberry, regardless of its appearance, is classified as a dry, not a fleshy fruit. Botanically, it is not a
berry; it is an
aggregate-accessory fruit, the latter term meaning the fleshy part is derived not from the plant's ovaries but from the
receptacle that holds the
ovaries.[22] Numerous dry
achenes 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.[22]
Schizocarps are dry fruits, though some appear to be fleshy. They originate from syncarpous ovaries but do not actually
dehisce; rather, they split into segments with one or more seeds. They include a number of different forms from a wide range of families, including
carrot,
parsnip,
parsley,
cumin.[14]
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.) The
stigma is the apical (at the apex) nodule that receives pollen; the
style is the stem-like column that extends down to the
ovary, which is the basal part that contains the seed-forming
ovule.Lilium unripe capsule fruit; an aggregate fruit.
An aggregate fruit is also called an aggregation, or etaerio; it develops from a single flower that presents numerous simple
pistils.[16] Each pistil contains one
carpel; together, they form a fruitlet. The ultimate (fruiting) development of the aggregation of pistils is called an aggregate fruit, etaerio fruit, or simply an etaerio.
Different types of aggregate fruits can produce different etaerios, such as achenes, drupelets, follicles, and berries.
For example, the Ranunculaceae species, including Clematis and Ranunculus, produces an etaerio of
achenes;
Rubus species, including raspberry: an etaerio of
drupelets;
The pistils of the
raspberry are called drupelets because each pistil is like a small
drupe attached to the receptacle. In some
bramble fruits, such as
blackberry, the receptacle, an accessory part, elongates and then develops as part of the fruit, making the blackberry an
aggregate-accessory fruit.[25] The strawberry is also an aggregate-accessory fruit, of which the seeds are contained in the
achenes.[26] 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 an inflorescence. Each ('smallish') flower produces a single fruitlet, which, as all develop, all merge into one mass of fruit.[27] Examples include
pineapple,
fig,
mulberry,
Osage orange, and
breadfruit. An inflorescence (a cluster) of white flowers, called a head, is produced first. After
fertilization, each flower in the cluster develops into a drupe; as the drupes expand, they develop as a connate organ, merging into a multiple fleshy fruit called a syncarp.
Progressive stages of multiple flowering and fruit development can be observed on a single branch of the Indian mulberry, or noni. 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. Commercial
cultivars of bananas and pineapples are examples of
seedless fruits. Some cultivars of
citrus fruits (especially
grapefruit,
mandarin oranges,
navel oranges),
satsumas,
table grapes, and of
watermelons are valued for their seedlessness. In some species, seedlessness is the result of parthenocarpy, 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.[28] Seedless bananas and grapes are
triploids, and seedlessness results from the abortion of the
embryonic plant that is produced by fertilization, a phenomenon known as stenospermocarpy, which requires normal pollination and fertilization.[29]
Seed dissemination
Variations in fruit structures largely depend on the
modes of dispersal applied to their seeds. Dispersal is achieved by wind or water, by
explosive dehiscence, and by interactions with animals.[30]
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 termed
zoochorous; common examples include
cocklebur,
unicorn plant, and
beggarticks (or Spanish needle).[31][32]
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 of
nuts typically motivate birds and
squirrels to
hoard them, burying them in soil to retrieve later during the winter of scarcity; thereby, uneaten seeds are sown effectively under natural conditions to
germinate 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, and
tuliptree. This mechanism increases dispersal distance away from the parent via wind. Other wind-dispersed fruit have tiny "
parachutes", e.g.,
dandelion,
milkweed,
salsify.[30]
Coconut fruits can float thousands of miles in the ocean, thereby spreading their seeds. Other fruits that can disperse via water are
nipa palm and
screw pine.[30]
Some fruits have evolved propulsive mechanisms that fling seeds substantial distances – perhaps up to 100 m (330 ft) in the case of the
sandbox tree – via explosive dehiscence or other such mechanisms (see
impatiens and
squirting cucumber).[33]
A
cornucopia 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 other
fruit 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 and
alcoholic beverages (brandy,
fruit beer, wine).[34] Spices like vanilla, black pepper, paprika, and
allspice are derived from berries.
Olive fruit is pressed for
olive oil and similar processing is applied to other oil-bearing fruits and vegetables.[35] Some fruits are available all year round, while others (such as blackberries and apricots in the UK) are subject to
seasonal availability.[36]
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 and
greengroceries and carried back to kitchens, at home or restaurant, for preparation of meals.[39]
Storage
All fruits benefit from proper post-harvest care, and in many fruits, the plant hormone
ethylene causes
ripening. Therefore, maintaining most fruits in an efficient
cold chain is optimal for post-harvest storage, with the aim of extending and ensuring shelf life.[40]
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 the
recommended 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 three
nutrients together.
Various culinary fruits provide significant amounts of
fiber and water, and many are generally high in
vitamin C.[41] An overview of numerous studies showed that fruits (e.g., whole apples or whole oranges) are satisfying (filling) by simply eating and chewing them.[42]
The dietary fiber consumed in eating fruit promotes
satiety, and may help to control body weight and aid reduction of blood
cholesterol, a
risk factor for
cardiovascular diseases.[43] Fruit consumption is under preliminary research for the potential to improve nutrition and affect chronic diseases.[44][45] Regular consumption of fruit is generally associated with reduced risks of several diseases and functional declines associated with aging.[46][47][48]
Food safety
For
food safety, the
CDC recommends proper fruit handling and preparation to reduce the risk of
food contamination and
foodborne 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.[49]
Allergies
Fruit allergies make up about 10 percent of all food-related allergies.[50][51]
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;[53]
Fruits of
opium poppy are the source of
opium, which contains the drugs
codeine and
morphine, as well as the biologically inactive chemical theabaine from which the drug
oxycodone is synthesized.[55]
Coir fiber from
coconut 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.[61]
The hard and colorful grain fruits of
Job's tears are used as decorative beads for jewelry, garments, and ritual objects.[62]
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^Agusti, Manuel; Primo-Millo, Eduardo (2020).
The Genus Citrus. Woodhead Publishing. pp. 219–244.
ISBN978-0-12-812163-4.
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^Hulme AC (1970). The Biochemistry of Fruits and Their Products. London & New York: Academic Press.
^Holt, S. H.; Miller, J. C.; Petocz, P.; Farmakalidis, E. (September 1995). "A satiety index of common foods". European Journal of Clinical Nutrition. 49 (9): 675–690.
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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.
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^Nathaniel Hawthorne, "The Great Carbuncle", in Twice-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!