The neem tree is a fast-growingtree that can reach a height of 15–20 metres (49–66 ft), and rarely 35–40 m (115–131 ft). It isevergreen, shedding many of its leaves during the dry winter months. The branches are wide and spreading. The fairly dense crown is roundish and may reach a diameter of 20–25 m (66–82 ft). The opposite,pinnate leaves are 20–40 cm (8–16 in) long, with 20 to 30 medium to dark green leaflets about 3–8 cm (1+1⁄4–3+1⁄4 in) long.[7] The terminal leaflet often is missing. Thepetioles are short.[8]
White and fragrantflowers are arranged in more-or-less droopingaxillarypanicles which are up to 25 cm (10 in) long. Theinflorescences, which branch up to the third degree, bear from 250 to 300 flowers. An individual flower is5–6 mm (3⁄16–1⁄4 in) long and8–11 mm (5⁄16–7⁄16 in) wide.Protandrous, bisexual flowers and male flowers exist on the same individual tree.
Thefruit is a smooth (glabrous), olive-likedrupe which varies in shape from elongate oval to nearly roundish, and when ripe is14–28 mm (1⁄2–1+1⁄8 in) by10–15 mm (3⁄8–5⁄8 in). The fruit skin (exocarp) is thin and the bitter-sweet pulp (mesocarp) is yellowish-white and very fibrous. The mesocarp is3–5 mm (1⁄8–1⁄4 in) thick. The white, hard inner shell (endocarp) of the fruit encloses one, rarely two, or three, elongatedseeds (kernels) having a brown seed coat.
Pollen grains
The neem tree[9] is similar in appearance to its relative, the chinaberry or bakain,Melia azedarach,[10] with which it may be confused.Melia azedarach also has toothed leaflets and similar looking fruit. One difference is that neem leaves arepinnate but chinaberry leaves aretwice- and thrice-pinnate.
The nameAzadirachta indica was first published byAdrien-Henri de Jussieu in 1830.[11] In 1753,Carl Linnaeus had described two species,Melia azedarach andMelia azadirachta.[12] De Jussieu consideredMelia azadirachta to be sufficiently different fromMelia azedarach to be placed in a new genus.[13] For both his species, Linnaeus referred to the name 'azedarach',[12] which is derived from the French 'azédarac', which in turn is from the Persian 'āzād dirakht' (ازادرخت), meaning 'free or noble tree'.[14] The Persian name of the tree,azad darakhat-e-hind, meaning 'the free tree of India', implies that it is free from disease and insect problems.[15]
The neem tree is noted for itsdrought resistance. Normally, it thrives in areas with sub-arid to sub-humid conditions, with an annual rainfall of 400–1,200 mm (16–47 in). It can grow in regions with an annual rainfall below 400 mm, but in such cases it depends largely onground water levels. Margosa can grow in many different types ofsoil, but it thrives best on well-drained deep and sandy soils. It is a typical tropical to subtropical tree and exists at annual mean temperatures of 21–32 °C (70–90 °F). It can tolerate high to very high temperatures and does not tolerate temperature below 5 °C (41 °F). Neem is one of very few shade-giving trees that thrive in drought-prone areas such as the dry coastal, southern districts ofIndia andPakistan. The trees are not at all delicate about water quality and thrive on the merest trickle of water, whatever the quality. In India and tropical countries where theIndian diaspora has reached, it is very common to see neem trees used for shade lining streets, around temples, schools and other such public buildings or in most people's backyards. In very dry areas, the trees are planted on large tracts of land.
In April 2015,A. indica was declared a class B and C weed in theNorthern Territory,Australia, meaning its growth and spread must be controlled and plants or propagules are not allowed to be brought into the territory. It is illegal to buy, sell, or transport the plants or seeds. Its declaration as a weed came in response to its invasion of waterways in the "Top End" of the territory.[17]
After being introduced into Australia, possibly in the 1940s,A. indica was originally planted in theNorthern Territory to provide shade for cattle. Trial plantations were established between the 1960s and 1980s inDarwin,Queensland, andWestern Australia, but the Australian neem industry did not prove viable. The tree has now spread into the savanna, particularly around waterways, and naturalised populations exist in several areas.[18]
Neem fruit, seeds, leaves, stems, andbark contain diversephytochemicals, some of which were first discovered in azadirachta seedextracts, such asazadirachtin established in the 1960s as an insectantifeedant, growth disruptor, andinsecticide.[19][20] The yield of azadirachtin from crushing 2 kg of seeds is about 5 g.[19]
The tender shoots and flowers of the neem tree are eaten as a vegetable in India. A soup-like dish calledvēppam pū cāṟu (வேப்பம் பூ சாறு) inTamil (translated as "margosa flowerrasam") made of the flower of neem is prepared inTamil Nadu. InBengal, young neem leaves are fried in oil with tiny pieces ofaubergine (brinjal). The dish is callednim bēgun bhājā (নিম বেগুন ভাজা) and is the first item during a Bengali meal, which acts as an appetizer. It is eaten with rice.
Neem leaves and fruits
Neem is used in parts of mainlandSoutheast Asia, particularly inCambodia, Laos (where it is calledkadao [ກະເດົາ]),Thailand (where it is known assadao [สะเดา[sàʔdaw] orsataoสะเตา[sàʔtaw]]),Myanmar (where it is known asta.ma [တမာ]) and Vietnam (where it is known assầu đâu and is used to cook the saladgỏi sầu đâu). Even if lightly cooked, the flavour is quite bitter, and the food is not consumed by all inhabitants of these countries. In Myanmar, young neemleaves and flower buds are boiled withtamarind fruit to soften its bitterness and eaten as a vegetable. Pickled neem leaves are also eaten with tomato and fish paste sauce in Myanmar.
Neem is used as aninsecticide, providing a natural alternative to synthetic pesticides. The active ingredient isazadirachtin.[23] Neem seeds are ground into powder that is soaked overnight in water and sprayed on the crop. To be effective, it must be applied repeatedly, at least every ten days. In addition to directly killing insects, neem acts as an anti-feedant, repellent, and egg-laying deterrent and thus protects the crop from damage. The insects starve and die within a few days. Neem also suppresses the subsequent hatching of their eggs. Neem-based fertilizers have been effective againstsouthern armyworm. Neem cake may be used as a fertilizer.[24] Silver nanoparticles made from the bark and leaves ofA. indica were also highly effective at killing first- and fourth-stageCulex quinquefasciatus mosquito larvae, but they worked less well against the pupae and adult mosquitoes.[25]
The neem genome andtranscriptomes from various organs have been sequenced.[30][31][32]Expressed sequence tags were identified by generation of subtractive hybridization libraries of neem fruit, leaf, fruit mesocarp, and fruit endocarp.[33][34]
In 1995, theEuropean Patent Office (EPO) granted a patent on an anti-fungal product derived from neem to theUnited States Department of Agriculture andW. R. Grace and Company.[35] The Indian government challenged the patent when it was granted, claiming that the process for which the patent had been granted had been in use in India for more than 2,000 years. In 2000, the EPO ruled in India's favour, but W. R. Grace appealed, claiming thatprior art about the product had never been published. On 8 March 2005, that appeal was lost and the EPO revoked the Neem patent.[35]
The biopesticide produced by extraction from the tree seeds containslimonoidtriterpenes.[19] Currently, the extraction process has disadvantages, such as contamination with fungi and heterogeneity in the content of limonoids due to genetic, climatic, and geographical variations.[36][37] To overcome these problems, production of limonoids from plantcell suspension and hairy root cultures in bioreactors has been studied,[38][39] including the development of a two-stage bioreactor process that enhances growth and production of limonoids with cell suspension cultures ofA. indica.[40]
^Compact Oxford English Dictionary (2013), Neem, page 679, Third Edition 2008 reprinted with corrections 2013, Oxford University Press.
^Henry Yule andA. C. Burnell (1996),Hobson-Jobson, Neem, page 622, The Anglo-Indian Dictionary, Wordsworth Reference. (This work was first published in 1886)
^Encarta World English Dictionary (1999), Neem, page 1210, St. Martin's Press, New York.
^Heuzé V., Tran G., Archimède H., Bastianelli D., Lebas F., 2015.Neem (Azadirachta indica).Feedipedia, a programme by Institut national de la recherche agronomique,CIRAD, AFZ andFAO. Last updated on 2 October 2015
^Sidhu OP, Kumar V, Behl HM (15 January 2003). "Variability in Neem (Azadirachta indica) with Respect to Azadirachtin Content".Journal of Agricultural and Food Chemistry.51 (4):910–915.Bibcode:2003JAFC...51..910S.doi:10.1021/jf025994m.PMID12568548.
^Prakash G, Bhojwani SS, Srivastava AK (1 August 2002). "Production of azadirachtin from plant tissue culture: State of the art and future prospects".Biotechnology and Bioprocess Engineering.7 (4):185–193.doi:10.1007/BF02932968.ISSN1226-8372.S2CID85845199.
^Srivastava S, Srivastava AK (17 August 2013). "Production of the Biopesticide Azadirachtin by Hairy Root Cultivation of Azadirachta indica in Liquid-Phase Bioreactors".Applied Biochemistry and Biotechnology.171 (6):1351–1361.doi:10.1007/s12010-013-0432-7.ISSN0273-2289.PMID23955295.S2CID36781838.
^Vásquez-Rivera A, Chicaiza-Finley D, Hoyos RA, et al. (1 September 2015). "Production of Limonoids with Insect Antifeedant Activity in a Two-Stage Bioreactor Process with Cell Suspension Culture of Azadirachta indica".Applied Biochemistry and Biotechnology.177 (2):334–345.doi:10.1007/s12010-015-1745-5.ISSN1559-0291.PMID26234433.S2CID207357717.
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