Carrot

Appearance

''Daucus carota'' is a biennial plant that grows a rosette of leaves in the spring and summer, while building up the stout taproot that stores large amounts of sugars for the plant to flower in the second year.

Soon after germination, carrot seedlings show a distinct demarcation between the taproot and the hypocotyl. The latter is thicker and lacks lateral roots. At the upper end of the hypocotyl is the seed leaf. The first true leaf appears about 10–15 days after germination. Subsequent leaves, produced from the stem nodes, are alternating and compound, and arranged in a spiral. The leaf blades are pinnate. As the plant grows, the bases of the cotyledon are pushed apart. The stem, located just above the ground, is compressed and the internodes are not distinct. When the seed stalk elongates, the tip of the stem narrows and becomes pointed, extends upward, and becomes a highly branched inflorescence. The stems grow to 60–200 cm tall.

Most of the taproot consists of parenchymatous outer cortex and an inner core . 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 conical shape, although cylindrical and round cultivars are available. The root diameter can range from 1 cm to as much as 10 cm at the widest part. The root length ranges from 5 to 50 cm , although most are between 10 and 25 cm .


Flower development begins when the flat apical meristem changes from producing leaves to an uplifted conical meristem capable of producing stem elongation and an inflorescence. The inflorescence is a compound umbel, and each umbel contains several umbellets. The first 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. 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 anthers usually dehisce and the stamens fall off before the stigma becomes receptive to receive pollen. The anthers of the brown male sterile flowers degenerate and shrivel before anthesis. 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.


Flower development is protandrous, so the anthers 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 periphery 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.

The fruit that develops is a schizocarp consisting of two mericarps; each mericarp is an achene or true seed. The paired mericarps are easily separated when they are dry. Premature separation 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.

The carrot is a diploid species, and has nine relatively short, uniform-length chromosomes . 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.

Evolution

The wild ancestors of the carrot are likely to have come from Iran and Afghanistan, which remain the centre of diversity of ''Daucus carota'', the wild carrot. A naturally occurring subspecies of the wild carrot, ''Daucus carota'' subsp. ''sativus'', has been selectively bred over the centuries to reduce bitterness, increase sweetness and minimise the woody core. This has produced the familiar garden vegetable.

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 to 2000–3000 BC. Some close relatives of the carrot are still grown for their leaves and seeds, for example parsley, fennel, dill and cumin. The first mention of the root in classical sources is during the 1st century. The plant appears to have been introduced into Europe via Spain by the Moors in the 8th century. and in the 10th century, in such locations in the Middle East, India and Europe, the roots were purple. The modern carrot originated in Afghanistan at about this time. The 12th-century Arab Andalusian agriculturist, Ibn al-'Awwam, describes both red and yellow carrots; The Jewish scholar Simeon Seth also mentions roots of these colours in the 11th century. Cultivated carrots appeared in China in the 14th century, and in Japan in the 18th century. Orange-coloured carrots appeared in the Netherlands, where the flag included orange, in the 17th century. These, the modern carrots, were intended by the antiquary John Aubrey 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." European settlers introduced the carrot to Colonial America in the 17th century.

Purple carrots, still orange on the inside, were sold in British stores starting in 2002.

Uses

Carrots can be eaten in a variety of ways. Only 3% of the β-carotene in raw carrots is released during digestion: this can be improved to 39% by pulping, cooking and adding cooking oil. 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''. Together with onion and celery, carrots are one of the primary vegetables used in a ''mirepoix'' to make various broths.

The greens are edible as a leaf vegetable, but are only occasionally eaten by humans; some sources suggest that the greens contain toxic alkaloids. 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. 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. Because the major carrot allergen, the protein Dauc c 1.0104, is cross-reactive with homologues in birch pollen and mugwort pollen , most carrot allergy sufferers are also allergic to pollen from these plants.

In India carrots are used in a variety of ways, as salads or as vegetables added to spicy rice or daal 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. Carrot salads are usually made with grated carrots in western parts with a seasoning of mustard seeds and green chillies popped in hot oil, while adding carrots to rice usually is in julienne shape.

The variety of carrot found in north India is rare everywhere except in Central Asia and other contiguous regions, and is now growing in popularity in larger cosmopolitan cities in South India. The north Indian carrot is pink-red comparable to plum or raspberry or deep red apple in colour while most other carrot varieties in the world vary from orange to yellow in colour, comparable to hallowe'en pumpkins.

Since the late 1980s, baby carrots or mini-carrots have been a popular ready-to-eat snack food available in many supermarkets. Carrots are puréed and used as baby food, dehydrated to make chips, flakes, and powder, and thinly sliced and deep-fried, like potato chips.

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 old English dish thought to have originated in the early 19th century. Carrots can also be used alone or with fruits in jam and preserves. Carrot juice is also widely marketed, especially as a health drink, either stand-alone or blended with fruits and other vegetables.