Yams

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Yams
Common wormwood (Dioscorea communis), illustration

Common wormwood ( Dioscorea communis ), illustration

Systematics
Subdivision : Seed plants (Spermatophytina)
Class : Bedecktsamer (Magnoliopsida)
Monocots
Order : Yams (Dioscoreales)
Family : Yam family (Dioscoreaceae)
Genre : Yams
Scientific name
Dioscorea
L.

Yams ( Dioscorea ), also known as yam or yams , are a genus of plants within the yam family (Dioscoreaceae). The up to 800 species are mainly found in the tropics . Some species are important tropical food and medicinal plants .

description

Balkan yams ( Dioscorea balcanica ), habit of a flowering plant
Balkan yams ( Dioscorea balcanica ), fruiting plant

Appearance and leaves

Yams species grow as twisting, perennial herbaceous plants . They form rhizomes or tubers as persistence organs, which can be very different in size, shape, color and ingredients as well as in their depth in the earth. Some species form nodules in the leaf axils ( e.g. Dioscorea bulbifera ).

The alternate or oppositely arranged leaves are divided into a petiole and a leaf blade. The simple or compound leaf blade has three to nine basal leaf veins .

Inflorescences and flowers

The flowers are always unisexual. The Dioscorea species are mostly dioecious ( dioecious ), rarely monoecious ( monoecious ) separate sexes. The flowers are spirally arranged in lateral, differently structured inflorescences , whereby the female inflorescences contain only a few flowers. The male flowers contain one or two circles with three stamens each , three of which can be reduced to staminodes . There may be three or six staminodes in the female flowers.

Fruits and seeds

The triangular capsule fruits open at the top when ripe. The seeds have membranous wings.

use

Yams at Brixton Market in London
Japanese yams in a market in Hamamatsu
A Japanese dish: baked yams, sprinkled with katsuobushi ( bonito flakes)

Some species and their selection forms are useful plants , both as important food plants and as medicinal plants. Many types of yams are grown for food because of their edible tubers.

In the most widely grown species, the underground tubers reach a length of up to 2 meters; their taste is sweet and resembles that of chestnuts and potatoes . They have dark brown to black skin and are rich in provitamin A and potassium . In addition to the “Chinese yam” (light root, Nagaimo, Dioscorea polystachya , Dioscorea batatas , Dioscorea divaricata or, incorrectly, Dioscorea opposita or Dioscorea oppositifolia ) and the Dioscorea japonica (“all Japanese mountain yams” or “Yama )imo” work Types of yams eaten raw toxic. Yams are similar in taste and appearance to sweet potatoes , but are not related to them. In South America , Africa and the Caribbean , yams are often part of the vegetable offer, but in Europe , unlike sweet potatoes, they are rarely available. In the kitchens of the tropics they are an important supplier of starch . In China there is a project to use genetic engineering to cultivate varieties of yams that are optimized as energy crops for the production of ethanol fuel .

In naturopathy, wild yams are used, depending on the dosage, to alleviate menopausal symptoms , against PMS and both for contraception and for people who have not wanted to have children. However, its use is controversial and requires intensive study of the topic. The wild yam containing large quantities of diosgenin , a cholesterol to the derivative with additional hydroxyl groups in the side chain, other than the inner rings ether Steran attach skeleton. Although the corpus luteum hormone progesterone can only be obtained from diosgenin through chemical degradation (marker degradation), diosgenin is referred to as “natural” progesterone in esoteric literature and alternative medicine. The use of yams root for progesterone production was initiated in 1944 by Russell Marker . In Mexico it led to the development of its own pharmaceutical industry based on the yams root.

Yams contain a small amount of amygdalin , which is converted into hydrogen cyanide in the intestine .

Economical meaning

The largest growing areas for yams are in Africa. The main producers (2018) are Nigeria , Ghana and the Ivory Coast . Only two of the ten largest producers are not located on the African continent: Haiti and Colombia.

The largest yam producers

According to the Food and Agriculture Organization (FAO) of the United Nations, around 72.6 million tons of yams were produced worldwide in 2018 . The ten largest producers together reaped 96.3% of the world harvest. Nigeria alone produced 65.5%.

Largest yam producers (2018)
rank country Quantity
(in t )
1 NigeriaNigeria Nigeria 47,532,615
2 GhanaGhana Ghana 7,858,209
3 Ivory CoastIvory Coast Ivory Coast 7,252,570
4th BeninBenin Benin 2,944,944
5 EthiopiaEthiopia Ethiopia 1,355,584
6th TogoTogo Togo 858.783
7th CameroonCameroon Cameroon 674.776
8th Central African RepublicCentral African Republic Central African Republic 513,489
9 ChadChad Chad 484,700
10 HaitiHaiti Haiti 423,545
world 72,580,852

Systematics and distribution

The genus Dioscorea was established by Carl von Linné in 1753 . The generic name Dioscorea honors the Greek doctor Pedanios Dioscurides , whose medicinal herbalism from the 1st century was important in medicine for over 1600 years. Synonyms for Dioscorea L. are: Borderea Miégev. , Botryosicyos Hochst. , Elephantodon salisb. , Epipetrum Phil. , Hamatris Salisb. , Helmia Kunth , Higinbothamia Uline , Hyperocarpa (Uline) GMBarroso, EFGuim. & Sucre , Merione Salisb. , Nanarepenta Matuda , Oncorhiza Pers. , Oncus Lour. , Polynomials Salisb. , Raja Burm. , Rajania L. , Ricophora Mill. , Rhizemys Raf. , Sismondaea Delponte , Strophis Salisb. , Tamus L. , Tamnus Mill. , Testudinaria Salisb. ex Burch. , Ubium J.F. Gmel. .

The genus Dioscorea is distributed almost worldwide from tropical to temperate areas . There are 52 species in China, 21 of which are only there. Some species are neophytes in some areas of the world .

The only species native to Central Europe are the common wormwood ( Dioscorea communis ) and the Balkan wormwood ( Dioscorea balcanica ).

The genus Yams ( Dioscorea ) includes 350 to 800 species:

Purple yams ( Dioscorea alata )
Stalked leaves of Dioscorea brachybotrya
Habit and simple leaves of Dioscorea bulbifera
Sprout axes with tubers of Dioscorea bulbifera
Flemishweed ( Dioscorea communis )
Stalked, simple foliage leaf of Dioscorea cotinifolia
Dioscorea dodecaneura
Dioscorea dregeana , fruiting
Inflorescence with flowers in detail and simple leaves of Dioscorea elephantipes
Tuber of Dioscorea elephantipes
Potato yams ( Dioscorea esculenta )
Fruits and finger-shaped leaves of the poisonous yams ( Dioscorea hispida )
Dioscorea japonica
Tuber of Dioscorea mexicana
Dioscorea nipponica
Habit and finger-shaped leaves of Dioscorea pentaphylla
Habit and stalked, simple leaves of the Chinese yams ( Dioscorea opposita )
Pedunculated leaves of Dioscorea polystachya
Dioscorea sincorensis
Dioscorea stegelmanniana
Dioscorea sylvatica
Habit and leaves of Dioscorea trifida
Wild yams ( Dioscorea villosa )

See also

literature

Individual evidence

  1. ↑ a b c d e f g h i j k l m n Chih-chi Ting, Michael G. Gilbert: Dioscoreaceae. In: Wu Zheng-yi, Peter H. Raven (Ed.): Flora of China. Volume 24 - Flagellariaceae through Marantaceae. Science Press and Missouri Botanical Garden Press, Beijing and St. Louis, 2000, ISBN 0-915279-83-5 . Dioscorea - online with the same text as the printed work .
  2. ↑ see also the corresponding article on the English language Wikipedia.
  3. ↑ a b c To clarify whether the “Japanese mountain yams” or “Yamaimo” (山芋) is called Dioscorea japonica or Dioscorea opposita → see: Section “Dioscorea opposita and Dioscorea japonica” on the discussion page (with possible individual references).
  4. ↑ Soyatech.com e-news, News China, Singapore Will Jointly Develop Energy-Intensive Plants for Biofuel Feedstocks from December 11, 2007 ( Memento from April 17, 2009 in the Internet Archive )
  5. ^ Yams root contraception ( memento from June 15, 2012 in the Internet Archive ) on mexican-wild-yam.de, accessed on October 10, 2017.
  6. ↑ Gillian Lockwood, Jill Anthony-Ackery, Jackie Meyers-Thompson and others. a .: Desire for children and fertility for dummies. Wiley VHC Verlag, 2008, ISBN 978-3-527-70442-2 , p. 83.
  7. ↑ Entry on amygdalin. In: Römpp Online . Georg Thieme Verlag, accessed on June 1, 2014.
  8. ↑ a b c Crops> Yams. In: FAO production statistics 2018. fao.org, accessed on April 22, 2020 (English).
  9. ↑ a b c d e Rafaël Govaerts, P. Wilkin, RMK Saunders: World Checklist of Dioscoreales. Yams and their allies: 1-65. The Board of Trustees of the Royal Botanic Gardens, Kew, 2007. In: Rafaël Govaerts (Ed.): Dioscorea. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved April 20, 2020.
  10. ^ Vernon Hilton Heywood : Alismataceae to Orchidaceae (Monocotyledones) . In: Thomas Gaskell Tutin et al. (Ed.): Flora Europaea . tape  5 . Cambridge University Press, 1980, ISBN 0-521-20108-X , Dioscoreaceae. , S. 84–85 ( Dioscorea on pp. 84–85 in the Google book search).
  11. ↑ Types and synonyms, Uni Melbourne.
  12. ^ Dioscorea batatas at Plants For A Future

Web links

Commons : Dioscorea  - collection of images, videos and audio files