Carrot

The carrot (Daucus carota subsp. sativus) is a root vegetable, usually orange in colour, though purple, black, red, white, and yellow varieties exist. Carrots are a domesticated form of the wild carrot, Daucus carota, native to Europe and southwestern Asia. The plant probably originated in Persia and originally cultivated for its leaves and seeds. The most commonly eaten part of the plant is the taproot, although the greens are sometimes eaten as well. The domestic carrot has been selectively bred for its greatly enlarged, more palatable, less woody-textured taproot.

The carrot is a biennial plant in the umbellifer family Apiaceae. At first, it grows a rosette of leaves while building up the enlarged taproot. Fast-growing varieties mature within three months (90 days) of sowing the seed, while slower-maturing varieties are harvested four months later (120 days). The roots contain high quantities of alpha- and beta-carotene, and are a good source of vitamin K and vitamin B6, but the belief that eating carrots improves night vision is a myth put forward by the British in World War II to mislead the enemy about their military capabilities.

The United Nations Food and Agriculture Organization (FAO) reports that world production of carrots and turnips (these plants are combined by the FAO) for the calendar year 2013 was 37.2 million tonnes; almost half (~45%) were grown in China. Carrots are widely used in many cuisines, especially in the preparation of salads, and carrot salads are a tradition in many regional cuisines.

Contents

1 Etymology 2 History 3 Description 4 Chemistry 5 Cultivation 5.1 Cultivation problems 5.2 Companion planting 6 Cultivars 7 Production 8 Storage 9 Consumption 9.1 Nutrition 9.2 Night vision 10 See also 11 References 11.1 Cited literature 12 External links

Etymology
The word is first recorded in English circa 1530 and was borrowed from Middle French carotte,[1] itself from Late Latin carōta, from Greek καρωτόνor karōton, originally from the Indo-European root *ker- (horn), due to its horn-like shape. In Old English, carrots (typically white at the time) were not clearly distinguished from parsnips: the two were collectively called moru or more (from Proto-Indo-European *mork- "edible root", cf. German Möhre).

Various languages still use the same word for "carrot" as they do for "root"; e.g. Dutch wortel.[2]

History
Molecular and genetic studies, along with written history, support the idea that the cultivated/domesticated carrot has a single origin in Central Asia.[3] The wild ancestors of the carrot are likely to have originated in Persia (regions of which are now Iran and Afghanistan), which remains the centre of diversity for Daucus carota, the wild carrot. A naturally occurring subspecies of the wild carrot was presumably bred selectively over the centuries to reduce bitterness, increase sweetness and minimise the woody core; this process produced the familiar garden vegetable.[4][5]

A depiction labeled "garden" carrot from the Juliana Anicia Codex, a copy, written in Constantinople in 515 AD, of Dioscorides' 1st century AD Greek work. The facing page states that "the root can be cooked and eaten."[6] When they were first cultivated, carrots were grown for their aromatic leaves and seeds rather than their roots. Carrot seeds have been found in Switzerland and Southern Germany dating back to 2000–3000 BC.[7] Some close relatives of the carrot are still grown for their leaves and seeds, for example: parsley, cilantro/coriander, fennel, dill and cumin. The first mention of the root in classical sources is during the 1st century,[8] and the carrot may have been eaten as a root vegetable by the Romans, although there is some ambiguity about this,[9] as they used the word pastinaca for both carrots and parsnips, part of the same family.[10]

The plant is depicted and described in the Eastern Roman Juliana Anicia Codex, a copy, made in 515 AD in Constantinople, of the Greek physician Dioscorides' 1st century AD pharmacopoeia of herbs and medicines, De Materia Medica. Three different types of carrots are depicted, and the text states of them that "the root can be cooked and eaten."[11]

Carrots in a range of colours The plant appears to have been introduced into Spain by the Moors in the 8th century.[12] In the 10th century, in wordwide locations like West Asia, India and Europe, the roots were purple.[13] The modern carrot originated in Afghanistan at about this time.[8] The Jewish scholar Simeon Seth describes both red and yellow carrots in the 11th century.[14] The 12th-century Arab-Andalusian agriculturist, Ibn al-'Awwam, also mentions roots of these colours;[15] Cultivated carrots appeared in China in the 14th century, and in Japan in the 18th century.[8] Orange-coloured carrots appeared in the Netherlands in the 17th century,[16] which has been related to the fact that the Dutch flag at the time, the Prince's Flag, included orange.[13] These, the modern carrots, were intended by the English antiquary John Aubrey (1626–1697) when he noted in his memoranda, "Carrots were first sown at Beckington in Somersetshire. Some very old Man there [in 1668] did remember their first bringing hither."[17] European settlers introduced the carrot to colonial America in the 17th century.[18]

Outwardly purple carrots, still orange on the inside, were sold in British stores beginning in 2002.[13]

Description
Daucus carota is a biennial plant that grows a rosette of leaves while building up the taproot that stores large amounts of sugars to provide energy for the plant to flower in the second year.

Seedlings shortly after germination Soon after germination, 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 the seed leaf. The first true leaf appears about 10–15 days after germination. Subsequent leaves, produced from the stem nodes, are alternating (with a single leaf attached to a node) and compound, and arranged in a spiral. The alternating compound leaves show pinnation. 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 the internodes are not distinct. When the seed stalk elongates for flowering, the tip of the stem narrows and becomes pointed, extends upward, and becomes a highly branched inflorescence. The tall stems grow to 60–200 cm (20–80 in) tall.[19]

Most of the taproot consists of a pulpy 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 typically have a long conical shape, although cylindrical and round cultivars are available. The root diameter can range from 1 cm (0.4 in) to as much as 10 cm (4 in) at the widest part. The root length ranges from 5 to 50 cm (2.0 to 19.7 in), although most are between 10 and 25 cm (4 and 10 in).[19]

Daucus carota umbel (inflorescence). Individual flowers are borne on undivided pedicels originating from a common node.

Top view of Daucus carota inflorescence, showing umbellets; the central flower is dark red

Flower development begins when the flat meristem changes from producing leaves to an uplifted, conical meristem capable of producing stem elongation and a cluster of flowers. The cluster is a compound umbel, 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. 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 five petals, five stamens, and an entire calyx. The stamens usually split and fall off before the stigma becomes receptive to receive pollen. 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 the carpels.[19]

Flowers consist of five petals, five stamens, and an entire calyx. Flowers change 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. 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 floral nectaries attract pollinating 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.[19]

The fruit that develops is a schizocarp consisting of two mericarps; each mericarp is a true 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 the commissural side that faced the septum of the ovary. The flattened side has five longitudinal ribs. The bristly hairs that protrude from some ribs are usually removed by abrasion during milling 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.[19]

The carrot is a diploid species, and has nine relatively short, uniform-length chromosomes (2n=18).[3] The genome size is estimated to be 473 mega base pairs, which is four times larger than Arabidopsis thaliana, one-fifth the size of the maize genome, and about the same size as the rice genome.[20]

Chemistry
β-Carotene structure. Carotene is responsible for the orange colour of carrots and many other fruits and vegetables. Polyacetylenes can be found in Apiaceae vegetables like carrots where they show cytotoxic activities.[21][22] Falcarinol and falcarindiol (cis-heptadeca-1,9-diene-4,6-diyne-3,8-diol)[23] are such compounds. This latter compound shows antifungal activity towards Mycocentrospora acerina and Cladosporium cladosporioides.[23] Falcarindiol is the main compound responsible for bitterness in carrots.[24]

Other compounds such as pyrrolidine (present in the leaves),[25] 6-hydroxymellein,[26] 6-methoxymellein, eugenin, 2,4,5-trimethoxybenzaldehyde (gazarin) or (Z)-3-acetoxy-heptadeca-1,9-diene-4,6-diin-8-ol (falcarindiol 3-acetate) can also be found in carrot.

Cultivation
Workers harvesting carrots, Imperial Valley, California, 1948 Carrots are grown from seed and can take up to four months (120 days) to mature, but most varieties mature within 70 to 80 days under the right conditions.[27] They grow best in full sun but tolerate some shade.[28] The optimum temperature is 16 to 21 °C (61 to 70 °F).[29] The ideal soil is deep, loose and well-drained, sandy or loamy, with a pH of 6.3 to 6.8.[30] 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.[31] 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.[27][32]

Cultivation problems

See also: List of carrot diseases

There are several diseases that can reduce the yield and market value of carrots. The most devastating carrot disease is Alternaria leaf blight, which has been known to eradicate entire crops. A bacterial leaf blight caused by Xanthomonas campestris can also be destructive in warm, humid areas. Root knot nematodes (Meloidogyne species) can cause stubby or forked roots, or galls.[33] Cavity spot, caused by the oomycetes Pythium violae and Pythium sulcatum, results in irregularly shaped, depressed lesions on the taproots.[34]

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, and genotype.[35]

Companion planting

Carrots benefit from strongly scented companion plants. The pungent odour of onions, leeks and chives help repel the carrot root fly,[30] and other vegetables that team well with carrots include lettuce, tomatoes and radishes, as well as the herbs rosemary and sage.[36] Carrots thrive in the presence of caraway, coriander, chamomile, marigold and Swan River daisy.[30] They can also be good companions for other plants; if left to flower, the carrot, like any umbellifer, attracts predatory wasps that kill many garden pests.[37]

Cultivars
Carrot seeds

Seeds of Daucus carota subsp. maximus - MHNT Carrot cultivars can be grouped into two broad classes, eastern carrots and western carrots.[38] A number of novelty cultivars have been bred for particular characteristics.

"Eastern" (a European and American continent reference) carrots were domesticated in Persia (probably in the lands of modern-day Iran and Afghanistan 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 from anthocyanin pigments.[39]

The western carrot emerged in the Netherlands in the 17th century,[40] There is a popular belief that its orange colour making it popular in those countries as an emblem of the House of Orange and the struggle for Dutch independence, although there is little evidence for this.[41] The orange colour results from abundant carotenes in these cultivars.

Western carrot cultivars are commonly classified by their root shape. The four general types are: Chantenay carrots. 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-coloured core and are mostly used for processing.[32] Varieties include Carson Hybrid and Red Cored Chantenay. Danvers carrots. These have strong foliage and the roots are longer than Chantaney 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.[32] They were developed in 1871 in Danvers, Massachusetts.[42] Varieties include Danvers Half Long and Danvers 126. Imperator carrots. 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.[32] Varieties include Imperator 58 and Sugarsnax Hybrid. Nantes carrots. These have sparse foliage, are cylindrical, short with a more blunt 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.[32] Varieties include Nelson Hybrid, Scarlet Nantes and Sweetness Hybrid.

One particular variety lacks the usual orange pigment due to carotene, and owing its white colour to a recessive gene for tocopherol (vitamin E).[43] Derived from Daucus carota L. and patented at the University of Wisconsin–Madison,[43] the variety is intended to supplement the dietary intake of Vitamin E.[44]

Production
Production of carrots and turnips – 2013

Country

Production (millions of tonnes)

China 16.8 Uzbekistan 1.6 Russia 1.6 United States 1.3 Ukraine 0.9

World 37.2

Source: FAOSTAT of the United Nations[45]

Carrots are one of the ten most economically important vegetable crops in the world.[46] In 2013, world production of carrots (combined with turnips) was 37.2 million tonnes, with China producing 45% of the world total (16.8 million tonnes, table).[45] Other major producers were Uzbekistan and Russia (4% of world total each), the United States (3%) and Ukraine (2%).[45]

Storage
Carrots can be stored for several months in the refrigerator or over winter in a moist, cool place. For long term storage, unwashed carrots can be placed in a bucket between layers of sand, a 50/50 mix of sand and wood shavings, or in soil. A temperature range of 32 to 40 °F (0 to 5 °C) is best.[47][48]

Consumption
Carrot tzimmes Carrots can be eaten in a variety of ways. Only 3 percent of the β-carotene in raw carrots is released during digestion: this can be improved to 39% by pulping, cooking and adding cooking oil.[49] Alternatively they may be chopped and boiled, fried or steamed, and cooked in soups and stews, as well as baby and pet foods. A well-known dish is carrots julienne.[50] Together with onion and celery, carrots are one of the primary vegetables used in a mirepoix to make various broths.[51]

The greens are edible as a leaf vegetable, but are rarely eaten by humans;[52] some sources suggest that the greens contain toxic alkaloids.[53][54] When used for this purpose, they are harvested young in high-density plantings, before significant root development, and typically used stir-fried, or in salads.[52] Some people are allergic to carrots. In a 2010 study on the prevalence of food allergies in Europe, 3.6 percent of young adults showed some degree of sensitivity to carrots.[55] Because the major carrot allergen, the protein Dauc c 1.0104, is cross-reactive with homologues in birch pollen (Bet v 1) and mugwort pollen (Art v 1), most carrot allergy sufferers are also allergic to pollen from these plants.[56]

In India carrots are used in a variety of ways, as salads or as vegetables added to spicy rice or dal dishes. A popular variation in north India is the Gajar 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.[57] 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 in thin strips and added to rice, can form part of a dish of mixed roast vegetables or can be blended with tamarind to make chutney.[58]

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-eat snack food available in many supermarkets.[59] Carrots are puréed and used as baby food, dehydrated to make chips, flakes, and powder, and thinly sliced and deep-fried, like potato chips.[60]

The sweetness of carrots allows the vegetable to be used in some fruit-like roles. Grated carrots are used in carrot cakes, as well as carrot puddings, an English dish thought to have originated in the early 19th century.[61] Carrots can also be used alone or blended with fruits in jams and preserves. Carrot juice is also widely marketed, especially as a health drink, either stand-alone or blended with juices extracted from fruits and other vegetables.[62]

Highly excessive consumption over a period of time results in a condition of carotenemia which is a yellowing of the skin caused by a build up of carotenoids.

Nutrition

Carrots, raw

Nutritional value per 100 g (3.5 oz)

Energy 173 kJ (41 kcal)

Carbohydrates 9.6 g

Sugars 4.7 g

Dietary fiber 2.8 g

Fat 0.24 g

Protein 0.93 g

Vitamins

Vitamin A equiv. beta-carotene

lutein zeaxanthin (104%) 835 μg

(77%) 8285 μg 256 μg

Thiamine (B1)

(6%) 0.066 mg

Riboflavin (B2)

(5%) 0.058 mg

Niacin (B3)

(7%) 0.983 mg

Pantothenic acid (B5)

(5%) 0.273 mg

Vitamin B6

(11%) 0.138 mg

Folate (B9)

(5%) 19 μg

Vitamin C

(7%) 5.9 mg

Vitamin E

(4%) 0.66 mg

Vitamin K

(13%) 13.2 μg

Minerals

Calcium

(3%) 33 mg

Iron

(2%) 0.3 mg

Magnesium

(3%) 12 mg

Manganese

(7%) 0.143 mg

Phosphorus

(5%) 35 mg

Potassium

(7%) 320 mg

Sodium

(5%) 69 mg

Zinc

(3%) 0.24 mg

Other constituents

Fluoride 3.2 µg

Water 88 g

Link to USDA Database Entry

Units μg = micrograms • mg = milligrams IU = International units Percentages are roughly approximated using US recommendations for adults.

The carrot gets its characteristic, bright orange colour from β-carotene, and lesser amounts of α-carotene, γ-carotene, lutein and zeaxanthin.[63] α- and β-carotenes are partly metabolized into vitamin A,[64][65] providing more than 100% of the Daily Value (DV) per 100 g serving of carrots (right table). Carrots are also a good source of vitamin K (13% DV) and vitamin B6 (11% DV), but otherwise have modest content of other essential nutrients (right table).[66]

Carrots are 88% water, 4.7% sugar, 0.9% protein, 2.8% dietary fiber, 1% ash and 0.2% fat.[66] Carrot dietary fiber comprises mostly cellulose, with smaller proportions of hemicellulose, lignin and starch.[60] Free sugars in carrot include sucrose, glucose and fructose.[66]

The lutein and zeaxanthin carotenoids characteristic of carrots are studied for their potential roles in vision and eye health.[63][67]

Night vision

The provitamin A beta-carotene from carrots does not actually help people to see in the dark unless they suffer from a deficiency of vitamin A.[68] This myth was propaganda used by the Royal Air Force during the Second World War to explain why their pilots had improved success during night air battles, but was actually used to disguise advances in radar technology and the use of red lights on instrument panels.[69] Nevertheless, the consumption of carrots was advocated in Britain at the time as part of a Dig for Victory campaign. A radio programme called The Kitchen Front encouraged people to grow, store and use carrots in various novel ways, including making carrot jam and Woolton pie, named after the Lord Woolton, the Minister for Food.[70]