Onion - wikipedia Onion vegetable This article is about the plant. For other uses, see Onion ( disambiguation ). `` Onions '' redirects here. For the surname, see Onions ( surname ). Onion Scientific classification Kingdom : Plantae Clade : Angiosperms Clade : Monocots Order : Asparagales Family : Amaryllidaceae Subfamily : Allioideae Genus : Allium Species : A. cepa Binomial name Allium cepa L. Synonyms Species synonymy Allium angolense Baker Allium aobanum Araki Allium ascalonicum auct. Allium ascalonicum var. condensum Millán Allium ascalonicum var. fertile Millán Allium ascalonicum f. rotterianum Voss ex J. Becker Allium ascalonicum var. sterile Millán Allium cepa var. aggregatum G. Don Allium cepa var. anglicum Alef. Allium cepa var. argenteum Alef. Allium cepa var. bifolium Alef. Allium cepa var. crinides Alef. Allium cepa var. flandricum Alef. Allium cepa var. globosum Alef. Allium cepa var. hispanicum Alef. Allium cepa var. jamesii Alef. Allium cepa var. lisboanum Alef. Allium cepa var. luteum Alef. Allium cepa var. multiplicans L.H. Bailey Allium cepa var. portanum Alef. Allium cepa var. praecox Alef. Allium cepa var. rosum Alef. Allium cepa var. sanguineum Alef. Allium cepa var. solaninum Alef. Allium cepa var. tripolitanum Alef. Allium cepa var. viviparum ( Metzg. ) Alef. Allium cepaeum St. - Lag. Allium commune Noronha Allium cumaria Buch. - Ham. ex Wall. Allium esculentum Salisb. Allium napus Pall. ex Kunth Allium nigritanum A. Chev. Allium pauciflorum Willd. ex Ledeb. Allium salota Dostál Ascalonicum sativum P. Renault Cepa alba P. Renault Cepa esculenta Gray Cepa pallens P. Renault Cepa rubra P. Renault Cepa vulgaris Garsault Kepa esculenta Raf. Porrum cepa ( L. ) Rchb. The onion ( Allium cepa L., from Latin cepa `` onion '' ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium. Its close relatives include the garlic, leek, chive, and Chinese onion. This genus also contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion ( Allium fistulosum ), the tree onion ( A. × proliferum ), and the Canada onion ( Allium canadense ). The name `` wild onion '' is applied to a number of Allium species, but A. cepa is exclusively known from cultivation. Its ancestral wild original form is not known, although escapes from cultivation have become established in some regions. The onion is most frequently a biennial or a perennial plant, but is usually treated as an annual and harvested in its first growing season. The onion plant has a fan of hollow, bluish - green leaves and its bulb at the base of the plant begins to swell when a certain day - length is reached. The bulbs are composed of shortened, compressed, underground stems surrounded by fleshy modified scale ( leaves ) that envelop a central bud at the tip of the stem. In the autumn ( or in spring, in the case of overwintering onions ), the foliage dies down and the outer layers of the bulb become dry and brittle. The crop is harvested and dried and the onions are ready for use or storage. The crop is prone to attack by a number of pests and diseases, particularly the onion fly, the onion eelworm, and various fungi cause rotting. Some varieties of A. cepa, such as shallots and potato onions, produce multiple bulbs. Onions are cultivated and used around the world. As a food item, they are usually served cooked, as a vegetable or part of a prepared savoury dish, but can also be eaten raw or used to make pickles or chutneys. They are pungent when chopped and contain certain chemical substances which irritate the eyes. Roots, leaves and developing bulb Umbel of onion flowers Contents 1 Taxonomy and etymology 2 Description 3 Uses 3.1 Origin and history 3.2 Onion types and products 3.3 Culinary uses 3.4 Non-culinary uses 4 Composition 4.1 Nutrients 4.2 Phytochemicals 4.3 Eye irritation 5 Cultivation 5.1 Pests and diseases 5.2 Storage in the home 6 Varieties 6.1 Common onion group ( var. cepa ) 6.2 Aggregatum group ( var. aggregatum ) 6.2. 1 Hybrids with A. cepa parentage 7 Production 8 See also 9 References 10 Further reading 11 External links Taxonomy and etymology The onion plant ( Allium cepa ), also known as the bulb onion or common onion, is the most widely cultivated species of the genus Allium. It was first officially described by Carl Linnaeus in his 1753 work Species Plantarum. A number of synonyms have appeared in its taxonomic history : Allium cepa var. aggregatum -- G. Don Allium cepa var. bulbiferum -- Regel Allium cepa var. cepa -- Linnaeus Allium cepa var. multiplicans -- L.H. Bailey Allium cepa var. proliferum -- ( Moench ) Regel Allium cepa var. solaninum -- Alef Allium cepa var. viviparum -- ( Metz ) Mansf. A. cepa is known exclusively from cultivation, but related wild species occur in Central Asia. The most closely related species include A. vavilovii ( Popov & Vved. ) and A. asarense ( R.M. Fritsch & Matin ) from Iran. However, Zohary and Hopf state that `` there are doubts whether the A. vavilovii collections tested represent genuine wild material or only feral derivatives of the crop. '' The vast majority of cultivars of A. cepa belong to the `` common onion group '' ( A. cepa var. cepa ) and are usually referred to simply as `` onions ''. The Aggregatum group of cultivars ( A. cepa var. aggregatum ) includes both shallots and potato onions. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion ( A. fistulosum ), Egyptian onion ( A. × proliferum ), and Canada onion ( A. canadense ). Cepa is commonly accepted as Latin for `` onion '' and has an affinity with Ancient Greek : κάπια ( kápia ), Albanian : qepë, Aromanian : tseapã, Catalan : ceba, English : chive, Occitan : ceba, Spanish : cebolla, Old French : cive, and Romanian : ceapă. Description Stereo image show Left frame hide Right frame show Parallel view ( ) show Cross-eye view ( ) Onion seeds have a distinct shape. The onion plant has been grown and selectively bred in cultivation for at least 7,000 years. It is a biennial plant, but is usually grown as an annual. Modern varieties typically grow to a height of 15 to 45 cm ( 6 to 18 in ). The leaves are yellowish - to bluish green and grow alternately in a flattened, fan - shaped swathe. They are fleshy, hollow, and cylindrical, with one flattened side. They are at their broadest about a quarter of the way up, beyond which they taper towards a blunt tip. The base of each leaf is a flattened, usually white sheath that grows out of a basal disc. From the underside of the disc, a bundle of fibrous roots extends for a short way into the soil. As the onion matures, food reserves begin to accumulate in the leaf bases and the bulb of the onion swells. In the autumn, the leaves die back and the outer scales of the bulb become dry and brittle, so the crop is then normally harvested. If left in the soil over winter, the growing point in the middle of the bulb begins to develop in the spring. New leaves appear and a long, stout, hollow stem expands, topped by a bract protecting a developing inflorescence. The inflorescence takes the form of a globular umbel of white flowers with parts in sixes. The seeds are glossy black and triangular in cross section. The average pH of an onion is around 5.5 Uses Origin and History Woodcut, 1547 Because the wild onion is extinct and ancient records of using onions span western and eastern Asia, the geographic origin of the onion is uncertain, with likely domestication worldwide. Food uses of onions date back thousands of years in China, Egypt and Persia. Traces of onions recovered from Bronze Age settlements in China suggest that onions were used as far back as 5000 BCE, not only for their flavour, but the bulb 's durability in storage and transport. Ancient Egyptians revered the onion bulb, viewing its spherical shape and concentric rings as symbols of eternal life. Onions were used in Egyptian burials, as evidenced by onion traces found in the eye sockets of Ramesses IV. Pliny the Elder of the first century CE wrote about the use of onions and cabbage in Pompeii. He documented Roman beliefs about the onion 's ability to improve ocular ailments, aid in sleep, and heal everything from oral sores and toothaches to dog bites, lumbago, and even dysentery. Archaeologists unearthing Pompeii long after its 79 CE volcanic burial have found gardens resembling those in Pliny 's detailed narratives. According to texts collected in the fifth / sixth century CE under the authorial aegis of `` Apicius '' ( said to have been a gourmet ), onions were used in many Roman recipes. In the Age of Discovery, onions were taken to North America by the first European settlers, only to discover the plant readily available, and in wide use in Native American gastronomy. According to diaries kept by certain of the first English colonists, the bulb onion was one of the first crops planted by the Pilgrim fathers. Onion types and products Jar of pickled onions Common onions are normally available in three colour varieties. Yellow or brown onions ( called red in some European countries ), are full - flavoured and are the onions of choice for everyday use, with many cultivars bred specifically to demonstrate this sweetness ( Vidalia, Walla Walla, Cévennes, `` Bermuda, '' &c. ). Yellow onions turn a rich, dark brown when caramelised and give French onion soup its sweet flavour. The red onion ( called purple in some European countries ) is a good choice for fresh use when its colour livens up the dish ; it is also used in grilling. White onions are the traditional onions used in classic Mexican cuisine ; they have a golden colour when cooked and a particularly sweet flavour when sautéed. While the large, mature onion bulb is most often eaten, onions can be eaten at immature stages. Young plants may be harvested before bulbing occurs and used whole as spring onions or scallions. When an onion is harvested after bulbing has begun, but the onion is not yet mature, the plants are sometimes referred to as `` summer '' onions. Additionally, onions may be bred and grown to mature at smaller sizes. Depending on the mature size and the purpose for which the onion is used, these may be referred to as pearl, boiler, or pickler onions, but differ from true pearl onions which are a different species. Pearl and boiler onions may be cooked as a vegetable rather than as an ingredient and pickler onions are often preserved in vinegar as a long - lasting relish. Onions are available in fresh, frozen, canned, caramelised, pickled, and chopped forms. The dehydrated product is available as kibbled, sliced, ring, minced, chopped, granulated, and powder forms. Onion powder is a seasoning widely used when the fresh ingredient is not available. It is made from finely ground, dehydrated onions, mainly the pungent varieties of bulb onions, and has a strong odour. Being dehydrated, it has a long shelf life and is available in several varieties : yellow, red, and white. Culinary uses See also : List of onion dishes This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( May 2018 ) Sautéing onions Onions are commonly chopped and used as an ingredient in various hearty warm dishes, and may also be used as a main ingredient in their own right, for example in French onion soup, creamed onions, and onion chutney. They are versatile and can be baked, boiled, braised, grilled, fried, roasted, sautéed, or eaten raw in salads. Their layered nature makes them easy to hollow out once cooked, facilitating stuffing them, as in Turkish sogan - dolma. Onions pickled in vinegar are eaten as a snack around the world, and as a side serving in pubs and fish and chip shops throughout the United Kingdom and the Commonwealth. They are part of a traditional British pub 's ploughman 's lunch, usually served with crusty bread, English cheese, and ale. Similar to garlic, onions can show an additional colour -- pink - red -- after cutting, an effect caused by reactions of amino acids with sulfur compounds. Non-culinary uses The large size of onion cells makes them useful for microscopy. These cells from the epidermis of a red onion are naturally pigmented. Onions have particularly large cells that are readily observed under low magnification. Forming a single layer of cells, the bulb epidermis is easy to separate for educational, experimental, and breeding purposes. Onions are, therefore, commonly employed in science education to teach the use of a microscope for observing cell structure. Onions are toxic to dogs, cats, guinea pigs, and many other animals. Composition Nutrients Raw onion bulbs Nutritional value per 100 g ( 3.5 oz ) Energy 166 kJ ( 40 kcal ) Carbohydrates 9.34 g Sugars 4.24 g Dietary fibre 1.7 g Fat 0.1 g Protein 1.1 g Vitamins Quantity % DV Thiamine ( B1 ) 4 % 0.046 mg Riboflavin ( B2 ) 2 % 0.027 mg Niacin ( B3 ) 1 % 0.116 mg Pantothenic acid ( B5 ) 2 % 0.123 mg Vitamin B6 9 % 0.12 mg Folate ( B9 ) 5 % 19 μg Vitamin C 9 % 7.4 mg Minerals Quantity % DV Calcium 2 % 23 mg Iron 2 % 0.21 mg Magnesium 3 % 10 mg Manganese 6 % 0.129 mg Phosphorus 4 % 29 mg Potassium 3 % 146 mg Zinc 2 % 0.17 mg Other constituents Quantity Water 89.11 g Fluoride 1.1 μg Link to USDA Database entry Units μg = micrograms mg = milligrams IU = International units Percentages are roughly approximated using US recommendations for adults. Source : USDA Nutrient Database Most onion cultivars are about 89 % water, 9 % carbohydrates ( including 4 % sugar and 2 % dietary fibre ), 1 % protein, and negligible fat ( table ). Onions contain low amounts of essential nutrients and have an energy value of 166 kJ ( 40 Calories ) in a 100 g ( 3.5 oz ) amount. Onions contribute savoury flavour to dishes without contributing significant caloric content. Phytochemicals Considerable differences exist between onion varieties in phytochemical content, particularly for polyphenols, with shallots having the highest level, six times the amount found in Vidalia onions. Yellow onions have the highest total flavonoid content, an amount 11 times higher than in white onions. Red onions have considerable content of anthocyanin pigments, with at least 25 different compounds identified representing 10 % of total flavonoid content. Onion polyphenols are under basic research to determine their possible biological properties in humans. Some people suffer from allergic reactions after handling onions. Symptoms can include contact dermatitis, intense itching, rhinoconjunctivitis, blurred vision, bronchial asthma, sweating, and anaphylaxis. Allergic reactions may not occur when eating cooked onions, possibly due to the denaturing of the proteins from cooking. Eye irritation Cut onions emit certain compounds which cause the lacrimal glands in the eyes to become irritated, releasing tears. Freshly cut onions often cause a stinging sensation in the eyes of people nearby, and often uncontrollable tears. This is caused by the release of a volatile gas, syn - propanethial - S - oxide, which stimulates nerves in the eye. This gas is produced by a chain of reactions which serve as a defence mechanism : chopping an onion causes damage to cells which releases enzymes called alliinases. These break down amino acid sulfoxides and generate sulfenic acids. A specific sulfenic acid, 1 - propenesulfenic acid, is rapidly acted on by a second enzyme, the lacrimatory factor synthase, producing the syn - propanethial - S - oxide. This gas diffuses through the air and soon reaches the eyes, where it activates sensory neurons. Lacrimal glands produce tears to dilute and flush out the irritant. Eye irritation can be avoided by cutting onions under running water or submerged in a basin of water. Leaving the root end intact also reduces irritation as the onion base has a higher concentration of sulphur compounds than the rest of the bulb. Refrigerating the onions before use reduces the enzyme reaction rate and using a fan can blow the gas away from the eyes. The more often one chops onions, the less one experiences eye irritation. The amount of sulfenic acids and lacrimal factor released and the irritation effect differs among Allium species. In 2008, the New Zealand Institute for Crop and Food Research created `` no tears '' onions by genetic modification to prevent the synthesis of lachrymatory factor synthase in onions. One study suggests that consumers prefer the flavor of onions with lower LFS content. However, since the LFS - silencing process involves reducing sulfur ingestion by the plant, it has also been suggested that LFS − onions are inferior in flavor. A method for efficiently differentiating LFS − and LFS+ onions has been developed based on mass spectrometry, with potential application in high - volume production ; gas chromatography is also used to measure lachrymatory factor in onions. In early 2018, Bayer released the first crop yield of commercially - available LFS - silenced onions under the name `` Sunions. '' They were the product of 30 years of cross-breeding ; genetic modification was not employed. Guinea hen weed and honey garlic contain a similar lachrymatory factor. Synthetic onion lachrymatory factor has been used in a study related to tear production, and has been proposed as a nonlethal deterrent against thieves and intruders. Cultivation Large - scale cultivation Onions are best cultivated in fertile soils that are well - drained. Sandy loams are good as they are low in sulphur, while clayey soils usually have a high sulphur content and produce pungent bulbs. Onions require a high level of nutrients in the soil. Phosphorus is often present in sufficient quantities, but may be applied before planting because of its low level of availability in cold soils. Nitrogen and potash can be applied at regular intervals during the growing season, the last application of nitrogen being at least four weeks before harvesting. Bulbing onions are day - length sensitive ; their bulbs begin growing only after the number of daylight hours has surpassed some minimal quantity. Most traditional European onions are referred to as `` long - day '' onions, producing bulbs only after 14 hours or more of daylight occurs. Southern European and North African varieties are often known as `` intermediate - day '' types, requiring only 12 -- 13 hours of daylight to stimulate bulb formation. Finally, `` short - day '' onions, which have been developed in more recent times, are planted in mild - winter areas in the autumn and form bulbs in the early spring, and require only 11 -- 12 hours of daylight to stimulate bulb formation. Onions are a cool - weather crop and can be grown in USDA zones 3 to 9. Hot temperatures or other stressful conditions cause them to `` bolt '', meaning that a flower stem begins to grow. Onions may be grown from seed or from sets. Onion seeds are short - lived and fresh seeds germinate better. The seeds are sown thinly in shallow drills, thinning the plants in stages. In suitable climates, certain cultivars can be sown in late summer and autumn to overwinter in the ground and produce early crops the following year. Onion sets are produced by sowing seed thickly in early summer in poor soil and the small bulbs produced are harvested in the autumn. These bulbs are planted the following spring and grow into mature bulbs later in the year. Certain cultivars are used for this purpose and these may not have such good storage characteristics as those grown directly from seed. Routine care during the growing season involves keeping the rows free of competing weeds, especially when the plants are young. The plants are shallow - rooted and do not need a great deal of water when established. Bulbing usually takes place after 12 to 18 weeks. The bulbs can be gathered when needed to eat fresh, but if they will be kept in storage, they should be harvested after the leaves have died back naturally. In dry weather, they can be left on the surface of the soil for a few days to dry out properly, then they can be placed in nets, roped into strings, or laid in layers in shallow boxes. They should be stored in a well - ventilated, cool place such as a shed. Pests and diseases Larvae of the onion fly Onions suffer from a number of plant disorders. The most serious for the home gardener are likely to be the onion fly, stem and bulb eelworm, white rot, and neck rot. Diseases affecting the foliage include rust and smut, downy mildew, and white tip disease. The bulbs may be affected by splitting, white rot, and neck rot. Shanking is a condition in which the central leaves turn yellow and the inner part of the bulb collapses into an unpleasant - smelling slime. Most of these disorders are best treated by removing and burning affected plants. The larvae of the onion leaf miner or leek moth ( Acrolepiopsis assectella ) sometimes attack the foliage and may burrow down into the bulb. The onion fly ( Delia antiqua ) lays eggs on the leaves and stems and on the ground close to onion, shallot, leek, and garlic plants. The fly is attracted to the crop by the smell of damaged tissue and is liable to occur after thinning. Plants grown from sets are less prone to attack. The larvae tunnel into the bulbs and the foliage wilts and turns yellow. The bulbs are disfigured and rot, especially in wet weather. Control measures may include crop rotation, the use of seed dressings, early sowing or planting, and the removal of infested plants. The onion eelworm ( Ditylenchus dipsaci ), a tiny parasitic soil - living nematode, causes swollen, distorted foliage. Young plants are killed and older ones produce soft bulbs. No cure is known and affected plants should be uprooted and burned. The site should not be used for growing onions again for several years and should also be avoided for growing carrots, parsnips, and beans, which are also susceptible to the eelworm. White rot of onions, leeks, and garlic is caused by the soil - borne fungus Sclerotium cepivorum. As the roots rot, the foliage turns yellow and wilts. The bases of the bulbs are attacked and become covered by a fluffy white mass of mycelia, which later produces small, globular black structures called sclerotia. These resting structures remain in the soil to reinfect a future crop. No cure for this fungal disease exists, so affected plants should be removed and destroyed and the ground used for unrelated crops in subsequent years. Neck rot is a fungal disease affecting onions in storage. It is caused by Botrytis allii, which attacks the neck and upper parts of the bulb, causing a grey mould to develop. The symptoms often first occur where the bulb has been damaged and spread downwards in the affected scales. Large quantities of spores are produced and crust - like sclerotia may also develop. In time, a dry rot sets in and the bulb becomes a dry, mummified structure. This disease may be present throughout the growing period, but only manifests itself when the bulb is in storage. Antifungal seed dressings are available and the disease can be minimised by preventing physical damage to the bulbs at harvesting, careful drying and curing of the mature onions, and correct storage in a cool, dry place with plenty of circulating air. Storage in the home Pickled onion Cooking onions and sweet onions are better stored at room temperature, optimally in a single layer, in mesh bags in a dry, cool, dark, well - ventilated location. In this environment, cooking onions have a shelf life of three to four weeks and sweet onions one to two weeks. Cooking onions will absorb odours from apples and pears. Also, they draw moisture from vegetables with which they are stored which may cause them to decay. Sweet onions have a greater water and sugar content than cooking onions. This makes them sweeter and milder tasting, but reduces their shelf life. Sweet onions can be stored refrigerated ; they have a shelf life of around 1 month. Irrespective of type, any cut pieces of onion are best tightly wrapped, stored away from other produce, and used within two to three days. Varieties Common onion group ( var. Cepa ) Rossa di Tropea onions for sale in Italy Most of the diversity within A. cepa occurs within this group, the most economically important Allium crop. Plants within this group form large single bulbs, and are grown from seed or seed - grown sets. The majority of cultivars grown for dry bulbs, salad onions, and pickling onions belong to this group. The range of diversity found among these cultivars includes variation in photoperiod ( length of day that triggers bulbing ), storage life, flavour, and skin colour. Common onions range from the pungent varieties used for dried soups and onion powder to the mild and hearty sweet onions, such as the Vidalia from Georgia, USA, or Walla Walla from Washington that can be sliced and eaten raw on a sandwich. Aggregatum group ( var. Aggregatum ) This group contains shallots and potato onions, also referred to as multiplier onions. The bulbs are smaller than those of common onions, and a single plant forms an aggregate cluster of several bulbs from a master. They are propagated almost exclusively from daughter bulbs, although reproduction from seed is possible. Shallots are the most important subgroup within this group and comprise the only cultivars cultivated commercially. They form aggregate clusters of small, narrowly ovoid to pear - shaped bulbs. Potato onions differ from shallots in forming larger bulbs with fewer bulbs per cluster, and having a flattened ( onion - like ) shape. However, intermediate forms exist. I'itoi onion is a prolific multiplier onion cultivated in the Baboquivari Peak Wilderness, Arizona area. This small - bulb type has a shallot - like flavour and is easy to grow and ideal for hot, dry climates. Bulbs are separated, and planted in the fall 1 in below the surface and 12 in apart. Bulbs will multiply into clumps and can be harvested throughout the cooler months. Tops die back in the heat of summer and may return with heavy rains ; bulbs can remain in the ground or be harvested and stored in a cool dry place for planting in the fall. The plants rarely flower ; propagation is by division. Hybrids with a cepa parentage A number of hybrids are cultivated that have A. cepa parentage, such as the diploid tree onion or Egyptian onion ( A. × proliferum ), and the triploid onion ( A. × cornutum ). The tree onion or Egyptian onion produces bulblets in the umbel instead of flowers, and is now known to be a hybrid of A. cepa and A. fistulosum. It has previously been treated as a variety of A. cepa, for example A. cepa var. proliferum, A. cepa var. bulbiferum, and A. cepa var. viviparum. It has been grown for centuries in Japan and China for use as a salad onion. The triploid onion is a hybrid species with three sets of chromosomes, two sets from A. cepa and the third set from an unknown parent. Various clones of the triploid onion are grown locally in different regions, such as ' Ljutika ' in Croatia, and ' Pran ', ' Poonch ', and ' Srinagar ' in the India - Kashmir region. ' Pran ' is grown extensively in the northern Indian provinces of Jammu and Kashmir. There are very small genetic differences between ' Pran ' and the Croatian clone ' Ljutika ', implying a monophyletic origin for this species. Some authors have used the name A. cepa var. viviparum ( Metzg. ) Alef. for the triploid onion, but this name has also been applied to the Egyptian onion. The only name unambiguously connected with the triploid onion is A. × cornutum. Spring onions or salad onions may be grown from the Welsh onion ( A. fistulosum ), as well as from A. cepa. Young plants of A. fistulosum and A. cepa look very similar, but may be distinguished by their leaves, which are circular in cross-section in A. fistulosum rather than flattened on one side. Onions ( dried ) production in 2016 Country ( millions of tonnes ) China 23.8 India 19.4 Egypt 3.1 United States 3.0 Iran 2.3 Turkey Russia 2.0 World 93.2 Source : UN Food & Agriculture Organisation Production Onions In 2016, world production of dried onions was 93.2 million tonnes, led by China and India producing 26 % and 21 % of the total, respectively. The Onion Futures Act, passed in 1958, bans the trading of futures contracts on onions in the United States. This prohibition came into force after farmers complained about alleged market manipulation by Sam Siegel and Vincent Kosuga at the Chicago Mercantile Exchange two years earlier. The subsequent investigation provided economists with a unique case study into the effects of futures trading on agricultural prices. The act remains in effect as of 2016. See also List of Allium species List of onion cultivars Pyruvate scale References Jump up ^ `` Allium cepa L ''. World Checklist of Selected Plant Families ( WCSP ). Royal Botanic Gardens, Kew -- via The Plant List. Jump up ^ Block, E. ( 2010 ). Garlic and Other Alliums : The Lore and the Science. Royal Society of Chemistry. ISBN 0 - 85404 - 190 - 7. Jump up ^ `` AllergyNet -- Allergy Advisor Find ''. Allallergy.net. Archived from the original on 15 June 2010. Retrieved 14 April 2010. ^ Jump up to : McNeal Jr., Dale W. ; Jacobsen, T.D. ( 2002 ). `` Allium cepa ''. In Flora of North America Editorial Committee. 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Jump up ^ Xu, K ; Huang, X ; Wu, M ; Wang, Y ; Chang, Y ; Liu, K ; Zhang, J ; Zhang, Y ; Zhang, F ; Yi, L ; Li, T ; Wang, R ; Tan, G ; Li, C ( 2014 ). `` A rapid, highly efficient and economical method of Agrobacterium - mediated in planta transient transformation in living onion epidermis ''. PLoS ONE. 9 ( 1 ) : e83556. doi : 10.1371 / journal. pone. 0083556. PMC 3885512. PMID 24416168. Jump up ^ Anne McCabe ; Mick O'Donnell ; Rachel Whittaker ( 19 July 2007 ). Advances in Language and Education. Bloomsbury Publishing. p. 35. ISBN 978 - 1 - 4411 - 0458 - 8. Jump up ^ Cope, R.B. ( August 2005 ). `` Allium species poisoning in dogs and cats '' ( PDF ). Veterinary Medicine. 100 ( 8 ) : 562 -- 566. ISSN 8750 - 7943. Jump up ^ Salgado, B.S. ; Monteiro, L.N. ; Rocha, N.S. ( 2011 ). `` Allium species poisoning in dogs and cats ''. Journal of Venomous Animals and Toxins Including Tropical Diseases. 17 ( 1 ) : 4 -- 11. doi : 10.1590 / S1678 - 91992011000100002. 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Journal of Investigational Allergology and Clinical Immunology. 22 ( 6 ) : 441 -- 442. PMID 23101191. ^ Jump up to : Scott, Thomas. `` What is the chemical process that causes my eyes to tear when I peel an onion ? ''. Ask the Experts : Chemistry. Scientific American. Retrieved 2007 - 04 - 28. ^ Jump up to : `` FAQ ''. National Onion Association. Retrieved 2013 - 03 - 28. Jump up ^ Hiskey, Daven ( 2010 - 11 - 05 ). `` Why onions make your eyes water ''. Today I Found Out. Retrieved 2013 - 03 - 28. Jump up ^ `` Tearless Onion Created In Lab Using Gene Silencing ''. ScienceDaily. 5 February 2008. Retrieved 23 November 2016. Jump up ^ Kim, Ha - Yeon ; Jackson, Daniel ; Adhikari, Koushik ; Riner, Cliff ; Sanchez - Brambila, Gabriela ( 2017 - 10 - 01 ). `` Relationship Between Consumer Acceptability and Pungency - Related Flavor Compounds of Vidalia Onions ''. Journal of Food Science. 82 ( 10 ) : 2396 -- 2402. doi : 10.1111 / 1750 - 3841.13915. ISSN 1750 - 3841. Jump up ^ Eady, Colin C. ; Kamoi, Takahiro ; Kato, Masahiro ; Porter, Noel G. ; Davis, Sheree ; Shaw, Martin ; Kamoi, Akiko ; Imai, Shinsuke ( 2008 - 08 - 01 ). `` Silencing Onion Lachrymatory Factor Synthase Causes a Significant Change in the Sulfur Secondary Metabolite Profile ''. Plant Physiology. 147 ( 4 ) : 2096 -- 2106. doi : 10.1104 / pp. 108.123273. ISSN 0032 - 0889. PMC 2492635. PMID 18583530. Jump up ^ Joyce, Nigel I. ; Eady, Colin C. ; Silcock, Patrick ; Perry, Nigel B. ; van Klink, John W. ( January 2013 ). `` Fast Phenotyping of LFS - Silenced ( Tearless ) Onions by Desorption Electrospray Ionization Mass Spectrometry ( DESI - MS ) ''. Journal of Agricultural and Food Chemistry. 61 : 1449 -- -- 1456 -- via ACS Publications. Jump up ^ Tewari, Gyanendra M. ; Bandyopadhyay, Chiranjib. ( 1975 - 07 - 01 ). `` Quantitative evaluation of lachrymatory factor in onion by thin - layer chromatography ''. Journal of Agricultural and Food Chemistry. 23 ( 4 ) : 645 -- 647. doi : 10.1021 / jf60200a044. ISSN 0021 - 8561. Jump up ^ Schmidt, Norman E. ; Santiago, Leanne M. ; Eason, H. Donald ; Dafford, Kurtus A. ; Grooms, Chris A. ; Link, Tammy E. ; Manning, Dana T. ; Cooper, Sylina D. ; Keith, R. Chad ( 1996 - 01 - 01 ). `` Rapid Extraction Method of Quantitating the Lachrymatory Factor of Onion Using Gas Chromatography ''. Journal of Agricultural and Food Chemistry. 44 ( 9 ) : 2690 -- 2693. doi : 10.1021 / jf950686s. ISSN 0021 - 8561. ^ Jump up to : Danovich, Tove ( February 8, 2018 ). `` Stop Crying ! Tear - Free Onions Are Here ''. National Public Radio. Retrieved April 13, 2018. Jump up ^ Van Hare, Holly ( 19 December 2017 ). `` Onions that do n't make you cry are finally here ''. LA Times. Retrieved 15 April 2018. Jump up ^ Klein, Joanna ( 5 September 2017 ). `` Why Onions Make You Cry ''. The New York Times. Retrieved 16 April 2018. Jump up ^ Higashihara, H., Yokoi, N., Aoyagi, M. et al. Jpn J Ophthalmol ( 2010 ) 54 : 215. https://doi-org.proxy.lib.umich.edu/10.1007/s10384-009-0786-0 Jump up ^ US patent 9482496B1, James Anthony Rocchi, Thomas John Stewart & Thomas John Stewart, `` Wall - mounted nonlethal device for defending against intruders '', published 2015 - 06 - 01, issued 2016 - 11 - 01, assigned to Fighting Chance Systems Inc Jump up ^ US patent 9890561B2, Yves Perrenoud, Daniel Idzkowski & Daniel Idzkowski, `` Pressurized chemical theft deterrent device '', published 2017 - 03 - 03, issued 2018 - 02 - 13, assigned to Skunklock Inc Jump up ^ Boyhan, George E. ; Kelley, W. Terry ( eds. ) ( 2007 ). `` 2007 Onion Production Guide ''. Production Guides. University of Georgia : College of Agricultural and Environmental Sciences. Retrieved 2013 - 09 - 14. CS1 maint : Multiple names : authors list ( link ) CS1 maint : Extra text : authors list ( link ) Jump up ^ Savonen, Carol ( 2006 - 07 - 13 ). `` Onion bulb formation is strongly linked with day length ''. Oregon State University Extension Service. Retrieved 2013 - 09 - 14. ^ Jump up to : `` Onions : Planting, Growing and Harvesting Onion Plants ''. The Old Farmer 's Almanac. Retrieved 2013 - 03 - 27. Jump up ^ Rhoades, Jackie. `` What is Onion Bolting and how to Keep an Onion from Bolting ''. Gardening Know How. Retrieved 2013 - 03 - 27. Jump up ^ `` Onion production ''. USDA : Agricultural Research Service. 2011 - 02 - 23. Retrieved 2013 - 03 - 27. Jump up ^ `` Onion ''. Plants for a Future. Retrieved 2013 - 03 - 22. Jump up ^ Hessayon, D.G. ( 1978 ). Be your own Vegetable Doctor. Pan Britannica Industries. pp. 22 -- 23. ISBN 0 - 903505 - 08 - 8. Jump up ^ Landry, Jean - François ( 2007 ). `` Taxonomic review of the leek moth genus Acrolepiopsis ( Lepidoptera : Acrolepiidae ) in North America ''. The Canadian Entomologist. 139 ( 3 ) : 319 -- 353. doi : 10.4039 / n06 - 098. Jump up ^ `` Delia antiqua ( Meigen ) : Onion Fly ''. Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. Retrieved 2013 - 03 - 29. Jump up ^ `` Onion Eelworm ( Ditylenchus dipsaci ) ''. GardenAction. 2011. Retrieved 2013 - 03 - 29. Jump up ^ `` Onion white rot ''. RHS Gardening. Royal Horticultural Society. Retrieved 2013 - 03 - 29. Jump up ^ `` Onion neck rot ''. RHS Gardening. Royal Horticultural Society. Retrieved 2013 - 03 - 29. Jump up ^ Jauron, Richard ( 2009 - 07 - 27 ). `` Harvesting and storing onions ''. Iowa State University Extension. Retrieved 2013 - 03 - 28. Jump up ^ Brewster, James L. ( 1994 ). Onions and other vegetable Alliums ( 1st ed. ). Wallingford, UK : CAB International. p. 5. ISBN 0 - 85198 - 753 - 2. Jump up ^ `` I'Itoi Onion ''. Ark of Taste. Slow Food USA. 2010. Retrieved 2013 - 03 - 25. Jump up ^ `` Allium × proliferum ''. Germplasm Resources Information Network ( GRIN ). Agricultural Research Service ( ARS ), United States Department of Agriculture ( USDA ). Retrieved 21 February 2011. ^ Jump up to : Fritsch, R.M. ; N. Friesen ( 2002 ). `` Chapter 1 : Evolution, Domestication, and Taxonomy ''. In H.D. Rabinowitch ; L. Currah. Allium Crop Science : Recent Advances. Wallingford, UK : CABI Publishing. p. 19. ISBN 0 - 85199 - 510 - 1. Jump up ^ Brewster, James L. ( 1994 ). Onions and other vegetable Alliums ( 1st ed. ). Wallingford, UK : CAB International. p. 15. ISBN 0 - 85198 - 753 - 2. Jump up ^ Friesen, N. & M. Klaas ( 1998 ). `` Origin of some vegetatively propagated Allium crops studied with RAPD and GISH ''. Genetic Resources and Crop Evolution. 45 ( 6 ) : 511 -- 523. doi : 10.1023 / A : 1008647700251. Jump up ^ Brewster, James L. ( 1994 ). Onions and other vegetable alliums ( 1st ed. ). Wallingford, UK : CAB International. p. 3. ISBN 0 - 85198 - 753 - 2. ^ Jump up to : `` Onion ( dry ) production in 2016 : Crops / World Regions / Production Quantity from pick lists ''. Food and Agriculture Organisation, Statistics Division ( FAOSTAT ). 2017. Retrieved 16 April 2018. Jump up ^ `` 7 USC § 13 -- 1 -- Violations, prohibition against dealings in motion picture box office receipts or onion futures ; punishment ''. United States Code : 7 USC § 13 -- 1. Legal Information Institute. 1958. Retrieved 2013 - 03 - 24. Further reading Block, E. ( 2010 ). Garlic and Other Alliums : The Lore and the Science. Royal Society of Chemistry ( UK ). ISBN 978 - 0 - 85404 - 190 - 9. Gripshover, Margaret M., and Thomas L. Bell, `` Patently Good Ideas : Innovations and Inventions in U.S. Onion Farming, 1883 -- 1939, '' Material Culture ( Spring 2012 ), vol 44 pp 1 -- 30. Sen, Colleen T. ( 2004 ). Food culture in India. Greenwood Publishing. ISBN 0 - 313 - 32487 - 5. External links Look up onion in Wiktionary, the free dictionary. Wikibooks Cookbook has a recipe / module on Onion powder Media related to Onions at Wikimedia Commons PROTAbase on Allium cepa Allium Allium species Chives Garlic Leek Onion Onion cultivars Calçot Cocktail Common / Bulb Yellow Red White Pearl Potato Scallion Shallot Sweet Tree Vidalia Welsh Onion species Allium...... abramsii... acuminatum... aflatunense... ampeloprasum... amplectens... anceps... atrorubens... bisceptrum... bolanderi... burlewii... caeruleum... campanulatum... cernuum... chinense... cratericola... crispum... cristophii... koreanum... monanthum... platycaule... praecox... punctum... sanbornii... shevockii... siskiyouense... sphaerocephalon... stellatum... stipitatum... textile... tribracteatum... tricoccum... triquetrum... tuolumnense... unifolium... validum... victorialis... yosemitense Onion food List of onion dishes Blooming Fried Onion cake Flammkuchen Zwiebelkuchen Onion ring Pickled Sogan - dolma Garlic cultivars Elephant Garlic chives Snow Mountain Solo Garlic species Allium...... canadense... drummondii... moly... neapolitanum... nigrum... roseum... sphaerocephalon... triquetrum... ursinum... vineale Garlic food List of garlic dishes Black garlic Persillade Pistou Garlic oil Garlic press Garlic bread Garlic chutney Beurre à la bourguignonne ( garlic butter ) Garlic soup Garlic and onion constituents Allicin Diallyl disulfide Diallyl trisulfide Allyl mercaptan syn - Propanethial - S - oxide Related Garlic Is as Good as Ten Mothers ( 1980 documentary ) Commons TRP channel modulators TRPA Activators 4 - Hydroxynonenal 4 - Oxo - 2 - nonenal 4, 5 - EET 12S - HpETE 15 - Deoxy - Δ - prostaglandin J2 α - Sanshool ( ginger, Sichuan and melegueta peppers ) Acrolein Allicin ( garlic ) Allyl isothiocyanate ( mustard, radish, horseradish, wasabi ) AM404 Bradykinin Cannabichromene ( cannabis ) Cannabidiol ( cannabis ) Cannabigerol ( cannabis ) Cinnamaldehyde ( cinnamon ) CR gas ( dibenzoxazepine ; DBO ) CS gas ( 2 - chlorobenzal malononitrile ) Curcumin ( turmeric ) Dehydroligustilide ( celery ) Diallyl disulfide Dicentrine ( Lindera spp. ) Farnesyl thiosalicylic acid Formalin Gingerols ( ginger ) Hepoxilin A3 Hepoxilin B3 Hydrogen peroxide Icilin Isothiocyanate Ligustilide ( celery, Angelica acutiloba ) Linalool ( Sichuan pepper, thyme ) Methylglyoxal Methyl salicylate ( wintergreen ) N - Methylmaleimide Nicotine ( tobacco ) Oleocanthal ( olive oil ) Paclitaxel ( Pacific yew ) Paracetamol ( acetaminophen ) PF - 4840154 Phenacyl chloride Polygodial ( Dorrigo pepper ) Shogaols ( ginger, Sichuan and melegueta peppers ) Tear gases Tetrahydrocannabinol ( cannabis ) Thiopropanal S - oxide ( onion ) Umbellulone ( Umbellularia californica ) WIN 55,212 - 2 Blockers Dehydroligustilide ( celery ) Nicotine ( tobacco ) Ruthenium red TRPC Activators Adhyperforin ( St John 's wort ) Diacyl glycerol GSK1702934A Hyperforin ( St John 's wort ) Substance P Blockers DCDPC DHEA - S Flufenamic acid GSK417651A GSK2293017A Meclofenamic acid N - ( p - amylcinnamoyl ) anthranilic acid Niflumic acid Pregnenolone sulfate Progesterone Pyr3 Tolfenamic acid TRPM Activators ADP - ribose BCTC Calcium ( intracellular ) Cold Coolact P Cooling Agent 10 CPS - 369 Eucalyptol ( eucalyptus ) Frescolat MGA Frescolat ML Geraniol Hydroxycitronellal Icilin Linalool Menthol ( mint ) PMD 38 Pregnenolone sulfate Rutamarin ( Ruta graveolens ) Steviol glycosides ( e.g., stevioside ) ( Stevia rebaudiana ) Sweet tastants ( e.g., glucose, fructose, sucrose ; indirectly ) Thio - BCTC WS - 3 WS - 12 WS - 23 Blockers Capsazepine Clotrimazole DCDPC Elismetrep Flufenamic acid Meclofenamic acid Mefenamic acid N - ( p - amylcinnamoyl ) anthranilic acid Nicotine ( tobacco ) Niflumic acid Ruthenium red Rutamarin ( Ruta graveolens ) Tolfenamic acid TPPO TRPML Activators MK6 - 83 PI ( 3, 5 ) P SF - 22 TRPP Activators Triptolide ( Tripterygium wilfordii ) Blockers Ruthenium red TRPV Activators 2 - APB 5 ', 6 ' - EET 9 - HODE 9 - oxoODE 12S - HETE 12S - HpETE 13 - HODE 13 - oxoODE 20 - HETE α - Sanshool ( ginger, Sichuan and melegueta peppers ) Allicin ( garlic ) AM404 Anandamide Bisandrographolide ( Andrographis paniculata ) Camphor ( camphor laurel, rosemary, camphorweed, African blue basil, camphor basil ) Cannabidiol ( cannabis ) Cannabidivarin ( cannabis ) Capsaicin ( chili pepper ) Carvacrol ( oregano, thyme, pepperwort, wild bergamot, others ) DHEA Diacyl glycerol Dihydrocapsaicin ( chili pepper ) Estradiol Eugenol ( basil, clove ) Evodiamine ( Euodia ruticarpa ) Gingerols ( ginger ) GSK1016790A Heat Hepoxilin A3 Hepoxilin B3 Homocapsaicin ( chili pepper ) Homodihydrocapsaicin ( chili pepper ) Incensole ( incense ) Lysophosphatidic acid Low pH ( acidic conditions ) Menthol ( mint ) N - Arachidonoyl dopamine N - Oleoyldopamine N - Oleoylethanolamide Nonivamide ( PAVA ) ( PAVA spray ) Nordihydrocapsaicin ( chili pepper ) Paclitaxel ( Pacific yew ) Paracetamol ( acetaminophen ) Phorbol esters ( e.g., 4α - PDD ) Piperine ( black pepper, long pepper ) Polygodial ( Dorrigo pepper ) Probenecid Protons RhTx Rutamarin ( Ruta graveolens ) Resiniferatoxin ( RTX ) ( Euphorbia resinifera / pooissonii ) Shogaols ( ginger, Sichuan and melegueta peppers ) Tetrahydrocannabivarin ( cannabis ) Thymol ( thyme, oregano ) Tinyatoxin ( Euphorbia resinifera / pooissonii ) Tramadol Vanillin ( vanilla ) Zucapsaicin Blockers α - Spinasterol ( Vernonia tweediana ) AMG - 517 Asivatrep BCTC Cannabigerol ( cannabis ) Cannabigerolic acid ( cannabis ) Cannabigerovarin ( cannabis ) Cannabinol ( cannabis ) Capsazepine DCDPC DHEA DHEA - S Flufenamic acid GRC - 6211 HC - 067047 Lanthanum Meclofenamic acid N - ( p - amylcinnamoyl ) anthranilic acid NGD - 8243 Niflumic acid Pregnenolone sulfate RN - 1734 RN - 9893 Ruthenium red SB - 705498 Tivanisiran Tolfenamic acid See also : Receptor / signaling modulators Ion channel modulators Taxon identifiers Wikidata : Q23485 Wikispecies : Allium cepa APDB : 14048 Calflora : 8630 EoL : 1084354 EPPO : ALLCE FNA : 200027457 FoC : 200027457 GBIF : 2857697 GRIN : 2244 iNaturalist : 48592 IPNI : 527795 - 1 IRMNG : 10201687 ITIS : 42720 NBN : NBNSYS0000002249 NCBI : 4679 NZOR : f82aaf80 - f01e - 478e - a663 - 830a981de942 PalDat : Allium_cepa Plant List : kew - 295261 PLANTS : ALCE POWO : urn : lsid : ipni.org : names : 527795 - 1 Tropicos : 18401646 uBio : 4962968 WCSP : 295261 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Onion&oldid=853439271 '' Categories : Allium Onions Plants described in 1753 Plants used in Native American cuisine Herbs Leaf vegetables Root vegetables Flora of the United States Flora of Mexico Flora of China Flora of Central America Flora of South America Flora of Europe Crops Hidden categories : CS1 maint : Uses editors parameter CS1 Latin - 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Question: where is food stored in the onion bulb
Answer: leaf bases