Thecarrot (Daucus carota subsp.sativus) is aroot vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellowcultivars exist, all of which are domesticated forms of thewild carrot,Daucus carota, native to Europe and Southwestern Asia. The plant probably originated inIran and was originally cultivated for its leaves and seeds.
The carrot is abiennial plant in theumbellifer family,Apiaceae. World production of carrots (combined withturnips) for 2022 was 42 milliontonnes, led by China producing 44% of the total.
The characteristic orange colour is frombeta-carotene, making carrots a rich source ofvitamin A. A myth that carrots help people to see in the dark was spread as propaganda in the Second World War, to account for the ability of British pilots to fight in the dark; the real explanation was the introduction ofradar.
The word is first recorded in English around 1530 and was borrowed from theMiddle Frenchcarotte, itself from theLate Latincarōta, from theancient Greekκαρωτόν (karōtón), originally from theProto-Indo-European root*ker- ('horn'), due to its horn-like shape.[3] InOld English, carrots (typically white at the time) were not clearly distinguished fromparsnips.[3] The word's use as a colour name in English was first recorded around 1670, originally referring to yellowish-red hair.[3]
Description
Daucus carota is abiennial plant. In the first year, energy is stored in thetaproot to enable the plant to flower in its second year.[4]
Soon aftergermination, carrot seedlings show a distinct demarcation between taproot and stem: the stem is thicker and lacks lateral roots. At the upper end of the stem is theseed leaf. The firsttrue leaf appears about 10–15 days after germination. Subsequent leaves arealternate (with a single leaf attached to a node),spirally arranged, andpinnatelycompound, with leaf bases sheathing the stem. As the plant grows, the bases of the seed leaves, near the taproot, are pushed apart. The stem, located just above the ground, is compressed and theinternodes are not distinct. When the seed stalk elongates for flowering, the tip of the stem narrows and becomes pointed, and the stem extends upward to become a highly branchedinflorescence up to 60–200 cm (20–80 in) tall.[5]
Most of the taproot consists of apulpy outer cortex (phloem) and an inner core (xylem). High-quality carrots have a large proportion of cortex compared to core. Although a completely xylem-free carrot is not possible, some cultivars have small and deeply pigmented cores; the taproot can appear to lack a core when the colour of the cortex and core are similar in intensity. Taproots are typically long and conical, although cylindrical and nearly spherical cultivars are available. The root diameter can range from 1 cm (3⁄8 in) to as much as 10 cm (4 in) at the widest part. The root length ranges from 5 to 50 cm (2 to 20 in), although most are between 10 and 25 cm (4 and 10 in).[5]
Flower development begins when the flatmeristem changes from producing leaves to an uplifted, conical meristem capable of producing stem elongation and acluster of flowers. The cluster is a compoundumbel, and each umbel contains several smaller umbels (umbellets). The first (primary) umbel occurs at the end of the main floral stem; smaller secondary umbels grow from the main branch, and these further branch into third, fourth, and even later-flowering umbels.[5]
A large, primary umbel can contain up to 50 umbellets, each of which may have as many as 50 flowers; subsequent umbels have fewer flowers. Individual flowers are small and white, sometimes with a light green or yellow tint. They consist of fivepetals, fivestamens, and anentirecalyx. Thestamens usuallysplit and fall off before thestigma becomes receptive to receivepollen. The stamens of the brown, male, sterile flowers degenerate and shrivel before the flower fully opens. In the other type of male sterile flower, the stamens are replaced by petals, and these petals do not fall off. A nectar-containing disc is present on the upper surface of thecarpels.[5]
Flowerschange sex in their development, so the stamens release their pollen before the stigma of the same flower is receptive. The arrangement is centripetal, meaning the oldest flowers are near the edge and the youngest flowers are in the center. Flowers usually first open at the outer edge of the primary umbel, followed about a week later on the secondary umbels, and then in subsequent weeks in higher-order umbels.[5]
The usual flowering period of individual umbels is 7 to 10 days, so a plant can be in the process of flowering for 30–50 days. The distinctive umbels and floralnectaries attractpollinating insects. After fertilization and as seeds develop, the outer umbellets of an umbel bend inward causing the umbel shape to change from slightly convex or fairly flat to concave, and when cupped it resembles a bird's nest.[5]
The fruit that develops is aschizocarp consisting of twomericarps; each mericarp is atrue seed. The paired mericarps are easily separated when they are dry. Premature separation (shattering) before harvest is undesirable because it can result in seed loss. Mature seeds are flattened on thecommissural side that faced theseptum of theovary. The flattened side has five longitudinal ribs. The bristly hairs that protrude from some ribs are usually removed by abrasion duringmilling and cleaning. Seeds also contain oil ducts and canals. Seeds vary somewhat in size, ranging from less than 500 to more than 1000 seeds per gram.[5]
The carrot is adiploid species, and has nine relatively short, uniform-lengthchromosomes (2n=18).[6][7] The genome size is estimated to be 473 megabase pairs, which is four times larger thanArabidopsis thaliana, one-fifth the size of the maize genome, and about the same size as the rice genome.[8]
Seedlings shortly after germination
Flowers consist of five petals, five stamens, and an entire calyx.
Daucus carota umbel (inflorescence). Individual flowers are borne on undivided pedicels from a common node.
Top view ofDaucus carota inflorescence, showing umbellets; the central flower is dark red.
Roots at market
Chemistry
β-Carotene structure.Carotene is responsible for the orange colour of carrots.
Both written history and molecular genetic studies indicate that the domestic carrot has a single origin in Central Asia.[6][7] Its wild ancestors probably originated inGreater Iran (regions of which are nowIran andAfghanistan), which remains the centre of diversity for thewild carrotDaucus carota. A naturally occurringsubspecies of the wild carrot was presumablybred selectively over the centuries to reduce bitterness, increase sweetness and minimise the woody core; this process produced the familiar garden vegetable.[15][16]
Cultivation
History
When first cultivated, carrots were grown for their aromatic leaves and seeds rather than their roots. Carrot seeds have been found inSwitzerland andSouthern Germany dating back to 2000–3000 BC.[17] Some close relatives of the carrot are still grown for their leaves and seeds, such asparsley,coriander (cilantro),fennel,anise,dill andcumin. The first mention of the root in classical sources is from the 1st century AD;[18] the Romans ate a root vegetable calledpastinaca,[19] which may have been either the carrot or the closely relatedparsnip.[20][21]
The plant is depicted and described in theEastern RomanJuliana Anicia Codex, a 6th-century ADConstantinopolitan copy of the Greek physicianDioscorides' 1st-century pharmacopoeia of herbs and medicines,De Materia Medica. The text states that "the root can be cooked and eaten".[22] Another copy of this work, Codex Neapolitanes from the late 6th or early 7th century, has basically the same illustrations but with roots in purple.[23]
The plant was introduced into Spain by theMoors in the 8th century.[24] In the 10th century, roots from West Asia, India and Europe were purple.[25] The modern carrot originated inAfghanistan at about this time.[18] The 11th-century Jewish scholarSimeon Seth describes both red and yellow carrots,[26] as does the 12th-century Arab-Andalusian agriculturist,Ibn al-'Awwam.[27] Cultivated carrots appeared in China in the 12th century,[28] and in Japan in the 16th or 17th century.[29]
The orange carrot was created by Dutch growers. There is pictorial evidence that the orange carrot existed at least in 512 AD, but it is probable that it was not a stable variety until the Dutch bred the cultivar termed the "Long Orange" at the start of the 18th century.[30] Some claim that the Dutch created the orange carrots to honorthe Dutch flag at the time andWilliam of Orange,[25][31] but other authorities argue these claims lack convincing evidence and it is possible that the orange carrot was favored by the Europeans because it does not brown the soups and stews as the purple carrot does and, as such, was more visually attractive.[30]
Modern carrots were described at about this time by the EnglishantiquaryJohn Aubrey (1626–1697): "Carrots were first sown at Beckington in Somersetshire. Some very old Man there [in 1668] did remember their first bringing hither."[32] European settlers introduced the carrot tocolonial America in the 17th century.[33] Outwardly purple carrots, still orange on the inside, were sold in British stores beginning in 2002.[25]
Propagation
Workers harvesting carrots by hand,Imperial Valley, California, 1948
Carrots are grown from seed and can take up to four months (120 days) to mature, but most cultivars mature within 70 to 80 days under the right conditions.[34] They grow best in full sun but tolerate some shade.[35] The optimum temperature is 16 to 21 °C (61 to 70 °F).[36] The ideal soil is deep, loose and well-drained, sandy or loamy, with apH of 6.3 to 6.8.[37]
Fertilizer should be applied according to soil type because the crop requires low levels of nitrogen, moderate phosphate and high potash. Rich or rocky soils should be avoided, as these will cause the roots to become hairy and/or misshapen.[38] Irrigation is applied when needed to keep the soil moist. After sprouting, the crop is eventually thinned to a spacing of 8 to 10 cm (3 to 4 in) and weeded to prevent competition beneath the soil.[34][39]
There are several diseases that can reduce the yield andmarket value of carrots. The most devastating carrot disease isAlternaria leaf blight, which has been known to eradicate entire crops. A bacterial leaf blight caused byXanthomonas campestris can also be destructive in warm, humid areas. Root knot nematodes (Meloidogyne species) can cause stubby or forked roots, orgalls.[40]Cavity spot, caused by theoomycetesPythium violae andPythium sulcatum, results in irregularly shaped, depressed lesions on the taproots.[41]
Physical damage can also reduce the value of carrot crops. The two main forms of damage are splitting, whereby a longitudinal crack develops during growth that can be a few centimetres to the entire length of the root, and breaking, which occurs postharvest. These disorders can affect over 30% of commercial crops. Factors associated with high levels of splitting include wide plant spacing, early sowing, lengthy growth durations, andgenotype.[42]
Carrots can be good companions for other plants; if left to flower, the carrot, like anyumbellifer, attracts predatory wasps that kill many garden pests.[43]
Cultivars
Carrot seedsSeeds ofDaucus carota subsp. maximus –MHNT
Carrotcultivars can be grouped into two broad classes: "Eastern" carrots and "Western" carrots.[44] A number of novelty cultivars have been bred for particular characteristics.[6][7]
"Eastern" (a European and American continent reference) carrots were domesticated in Persia (probably in the lands of modern-dayIran andAfghanistan within West Asia) during the 10th century, or possibly earlier. Specimens of the Eastern carrot that survive to the present day are commonly purple or yellow, and often have branched roots. The purple colour common in these carrots comes fromanthocyanin pigments.[45]
The "Western" carrot emerged in theNetherlands in the 16th or 17th century.[46] There is a popular belief that its orange colour made it popular in those countries as an emblem of theHouse of Orange and the struggle forDutch independence, although there is little evidence for this beyond oral tradition and the timing.[30][31]
Western carrot cultivars are commonly classified by their root shape. The four general types are:
Chantenay. Although the roots are shorter than other cultivars, they have vigorous foliage and greater girth, being broad in the shoulders and tapering towards a blunt, rounded tip. They store well, have a pale core, and are mostly used for processing.[39]
Danvers. These have strong foliage, and the roots are longer than Chantenay types, and they have a conical shape with a well-defined shoulder, tapering to a point. They are somewhat shorter than Imperator cultivars, but more tolerant of heavy soil conditions. Danvers cultivars store well and are used both fresh and for processing.[39] They were developed in 1871 inDanvers, Massachusetts.[47]
Imperator. This cultivar has vigorous foliage, is of high sugar content, and has long and slender roots, tapering to a pointed tip. Imperator types are the most widely cultivated by commercial growers.[39]
Nantes. These have sparse foliage, are cylindrical, short with a blunter tip than Imperator types, and attain high yields in a range of conditions. The skin is easily damaged and the core is deeply pigmented. They are brittle, high in sugar, and store less well than other types.[39]
Breeding programs have developed new cultivars to have dense amounts of chemically-stableacylated pigments, such asanthocyanins, which can produce different colours.[6][7] One particular cultivar lacks the usual orange pigment due to carotene, owing its white colour to arecessive gene fortocopherol (vitamin E), but this cultivar and wild carrots do not provide nutritionally significant amounts of vitamin E.[48]
Carrots can be stored for several months in the refrigerator or over winter in a cool dry place. For long term storage, unwashed carrots can be placed in a bucket between dry layers of sand, a 50/50 mix of sand and wood shavings, or in soil. A temperature range of 0 to 4 °C (32 to 40 °F) and 90–95% humidity is best.[50][51] During storage, carrots may be subject to the development of bitterness, white blush, and browning, leading to carrot losses.[52] Bitterness can be prevented by storage in well-ventilated rooms with lowethylene content (for example, without ethylene-producing fruit and vegetables). White blush and browning can be countered with application of edible films, heat treatment, application ofhydrogen sulfide, and ultraviolet irradiation.[52]
Production
In 2022, world production of carrots (combined withturnips) was 42 milliontonnes, led by China with 44% of the total. Uzbekistan, the United States, and Russia were the only other countries producing over 1 million tonnes annually (table).
Raw carrots are 88% water, 9%carbohydrates, 1%protein, and contain negligiblefat (table). In a reference amount of 100 grams (3.5 oz), raw carrots supply 41calories and have a rich content (20% or more of theDaily Value, DV) ofvitamin A (93% DV) and a moderate amount (10–19% DV) ofvitamin K (11% DV) andpotassium (11% DV), but otherwise have low content ofmicronutrients (table).
As a common source of beta-carotene in diets, carrots are a provitamin A source; anenzyme that converts beta-carotene into vitamin A in thesmall intestine.[55][56]
Carrots can be eaten in a variety of ways. Only 3 percent of theβ-carotene in raw carrots is released during digestion: this can be improved to 39% by pulping, cooking and adding cooking oil.[57] Alternatively they may be chopped and boiled, fried or steamed, and cooked insoups andstews, as well as baby and pet foods. A well-known dish iscarrotsjulienne.[58] Together with onion andcelery, carrots are one of the primary vegetables used in amirepoix to makebroths.[59]
The greens are edible as aleaf vegetable,[60][61] but are rarely eaten by humans;[62] some sources suggest that the greens contain toxicalkaloids.[63][64] When used for this purpose, they are harvested young in high-density plantings, before significant root development, and typically usedstir-fried, or in salads.[62] Some people are allergic to carrots. In a 2010 study on the prevalence offood allergies in Europe, 3.6 percent of young adults showed some degree ofsensitivity to carrots.[65] Because the major carrotallergen, the protein Dauc c 1.0104, iscross-reactive with homologues inbirch pollen (Bet v 1) andmugwort pollen (Art v 1), most carrot allergy sufferers are also allergic to pollen from these plants.[66]
In India, carrots are used in a variety of ways, as salads or as vegetables added to spicy rice ordal dishes. A popular variation in north India is thegajar ka halwa carrot dessert, which has carrots grated and cooked in milk until the whole mixture is solid, after which nuts and butter are added.[67] Carrot salads are usually made with grated carrots with a seasoning of mustard seeds and green chillies popped in hot oil. Carrots can also be cut into thin strips and added to rice, can form part of a dish of mixed roast vegetables, or can be blended withtamarind to makechutney.[68] Since the late 1980s,baby carrots or mini-carrots (carrots that have been peeled and cut into uniform cylinders) have been a popular ready-to-eatsnack food available in many supermarkets.[69]Carrot juice is widely marketed, especially as a health drink, either stand-alone or blended with juices from fruits and other vegetables.[70]
The sweetness of carrots allows the vegetable to be used in some fruit-like roles. They are used grated incarrot cakes, as well ascarrot puddings, an English dish thought to have originated in the early 19th century.[71] Carrots can be used alone or blended with fruits injams andpreserves. In theEuropean Union, there is a rule specifying that only fruits can be used in making jams; to preserve the Portuguese carrot jam delicacy (orDoce de Cenoura in Portuguese), theCouncil of the European Union adopted a directive that, for purposes of regulation of fruit jams and jellies, considers carrots as fruit.[72]
Very high consumption of carrots over a long period of time can result incarotenemia, a harmless yellow-orange discoloration of the skin caused by a buildup of carotenoids.[73]
In culture
Despite popular belief, the provitamin A beta-carotene from carrots does not actually help people to see in the dark unless they suffer fromvitamin A deficiency.[55] This myth was propaganda used by theRoyal Air Force during theSecond World War to explain why British pilots had improvednight vision which enabled their success during nighttime air battles; in reality, it was thanks to newly adoptedradar technology.[74]
The consumption of carrots was advocated in Britain at the time as part of aDig for Victory campaign. A radio program calledThe Kitchen Front encouraged people to grow, store and use carrots in various novel ways, including making carrot jam andWoolton pie, named after theLord Woolton, theMinister for Food.[75] The British public during WWII generally believed that eating carrots would help them see better at night and in 1942 there was a 100,000-ton surplus of carrots from the extra production.[76]
See also
Carrot and stick – Metaphor for the use of punishment and reward
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^Baranska, Malgorzata; Schulz, Hartwig; Baranski, Rafal; et al. (2005). "In situ simultaneous analysis of polyacetylenes, carotenoids and polysaccharides in carrot roots".Journal of Agricultural and Food Chemistry.53 (17):6565–6571.Bibcode:2005JAFC...53.6565B.doi:10.1021/jf0510440.PMID16104767.
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^Ballmer-Weber, B.K.; Skamstrup Hansen, K.; Sastre, J.; et al. (2012). "Component-resolved in vitro diagnosis of carrot allergy in three different regions of Europe".Allergy.67 (6):758–766.doi:10.1111/j.1398-9995.2012.02827.x.PMID22486768.S2CID23864612.
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