Adansonia

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Adansonia
Baobab Adansonia digitata.jpg
Adansonia digitata in Tanzania
Scientific classification e
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malvales
Family: Malvaceae
Subfamily: Bombacoideae
Genus: Adansonia
L.[1]
Species

See species section

Adansonia is a genus made up of eight species of medium to large deciduous trees known as baobabs (/ˈbˌbæb/ or /ˈbˌbæb/). They are placed in the Malvaceae family, subfamily Bombacoideae. They are native to Madagascar, mainland Africa, and Australia.[2] The trees have also been introduced to other regions such as Asia.[3][4] The generic name honours Michel Adanson, the French naturalist and explorer who described Adansonia digitata.[5] The baobab is also known as the "upside down tree", a name that originates from several myths.[6] They are among the most long-lived of vascular plants[7] and have large flowers that are reproductive for a maximum of 15 hours.[8] The flowers open around dusk, opening so quickly that movement can be detected by the naked eye, and are faded by the next morning.[8] The fruits are large, oval to round and berry-like and hold kidney-shaped seeds in a dry, pulpy matrix.

In the early 21st century, baobabs in southern Africa began to die off rapidly from a cause yet to be determined. It is unlikely that disease or pests would be able to kill many trees so rapidly, and some have speculated that the die-off is a result of dehydration.[9][10]

Description[edit]

General[edit]

Adansonia digitata (African baobab) tree in Mikumi National Park with its fruits hanging

Baobabs are long-lived deciduous, small to large trees from 5 to 30 m tall[8] with broad trunks and compact crowns. Young trees usually have slender, tapering trunks, often with a swollen base. Mature trees have massive trunks that are bottle-shaped or cylindrical and tapered from bottom to top.[8] The trunk is made of fibrous wood arranged in concentric rings, although rings are not always formed annually and so cannot be used to determine the age of individual trees.[11] Tree diameter fluctuates with rainfall so it is thought that water may be stored in the trunk.[8] Baobab trees have two types of shoots—long, green vegetative ones, and stout, woody reproductive ones. Branches can be massive and spread out horizontal from the trunk or are ascending. Adansonia rubrostipa is the only baobab that sometimes has spines.[8] Adansonia gregorii is generally the smallest of the baobabs, rarely getting to over 10 m (33 ft) tall and often with multiple trunks.[8] Both A. rubrostipa and A. madagascariensis are small to large trees, from 5 to 20 m (16 to 66 ft) tall.[8] The other baobabs grow from 25 to 30 m (80 to 100 ft) tall, with 2 to 3 m (7 to 10 ft) diameter trunks. A. digitata however often have massive single or multiple trunks of up to 10 m (33 ft) diameter.[8]

Leaves[edit]

Leaves are palmately compound in mature trees, but seedlings and regenerating shoots may have simple leaves. The transition to compound leaves comes with age and may be gradual. Leaves have 5-11 leaflets, with the largest ones in the middle and may be stalkless or with short petioles. Leaflets may have toothed or smooth edges and may be hairless or have simple to clumped hairs. Baobabs have stipules at the base of the leaves, but the stipules are soon shed in most species. Baobabs are deciduous, shedding leaves during the dry season.[8]

Flowers[edit]

Open flower showing distorted petals and the unfused ball of stamens set on top of the staminal tube
Bisected flower showing the style running through the staminal tube, bending, then projecting out of the stamens

In most Adansonia species, the flowers are born on short erect or spreading stalks in the axils of the leaves near the tips of reproductive shoots. Only A. digitata has flowers and fruits set on long, hanging stalks. There is usually only a single flower in an axil, but sometimes flowers occur in pairs. They are large, showy and strongly scented. They only open near dusk. Opening is rapid and movement of the flower parts is fast enough to be visible. Most Adansonia species are pollinated by bats.[12] Flowers may remain attached to the trees for several days, but the reproductive phase is very short, with pollen shed during the first night and stigmas shriveled by the morning. The flower is made up of an outer 5-lobed calyx, and an inner ring of petals set around a fused tube of stamens.[8] The outer lobes of the calyx are usually green (brown in A. grandidieri) and in bud are joined almost to the tip. As the flower opens, the calyx lobes split apart and become coiled or bent back (reflexed) at the base of the flower. The inner surface of the lobes are silky-hairy and cream, pink, or red.[8] Sometimes the lobes do not separate cleanly, distorting the shape of the flower as they bend back. The calyx lobes remain fused at the base, leaving a feature (calyx tube) that has nectar-producing tissue and that is cup-shaped, flat or tubular; the form of the calyx tube varies with species.[8] The flowers have a central tube (staminal tube) made up of fused stalks of stamens (filaments), with unfused filaments above. A densely hairy ovary is enclosed in the staminal tube, and a long style tipped with a stigma emerges from the filaments. Petals are set near the base of the staminal tube and are variable in shape and colour. The flowers, when fresh, may be white, cream, bright yellow or dark red, but fade quickly, often turning reddish when dried.[8]

Fruit[edit]

The fruit of the baobabs is one of their distinguishing features. It is large, oval to round, and berry-like in most species (usually less than 10 centimetres (3.9 in) long in A. madagascariensis.[8]). It has a dry, hard outer shell of variable thickness. In most species, the shell is indehiscent (does not break open easily). A. gibbosa is the only species with fruits that crack while still on the tree, which then tend to break open upon landing on the ground. Inside the outer shell, kidney-shaped seeds 10-15(-20) mm long are set in a dry pulp.[8]

Taxonomy[edit]

The earliest written reports of baobab are from a 14th century travelogue by the Arab traveler Ibn Batuta.[8] The first botanical description was by Alpino (1592) looking at fruits that he observed in Egypt from an unknown source. They were called Bahobab, possibly from the Arabic "bu hibab," meaning "many-seeded fruit".[8] The French explorer and botanist, Michel Adanson (1727–1806) observed a baobab tree in 1749 on the island of Sor, Senegal and wrote the first detailed botanical description of the full tree, accompanied with illustrations. Recognizing the connection to the fruit described by Alpino he called the genus Baobab. Linnaeus later renamed the genus Adansonia, to honour Adason, but use of baobab as one of the common names has persisted.[8]

The genus Adansonia is in the subfamily Bombacoideae, within the family Malvaceae in the order Malvales. The subfamily Bombacoideae was previously treated as the Bombacaceae family but it is no longer recognized at the rank of family by the Angiosperm Phylogeny Group I 1998, II 2003 or the Kubitzki system 2003. There are eight accepted species of Adansonia. A new species (Adansonia kilima Pettigrew, et al.), was described in 2012, found in high-elevation sites in eastern and southern Africa.[13] This is however no longer recognized as a distinct species[14] but considered a synonym of A. digitata. Some high-elevation trees in Tanzania show different genetics and morphology but further study is needed to determine if recognition of them as a separate species is warrented.[14] The genus Adansonia is further divided into three sections. Section Adansonia includes only A. digitata. This species has hanging flowers and fruit, set on long flowering stalks. This is the type species for the genus Adansonia.[8] All species of Adansonia except A. digitata are diploid; A. digitata is tetraploid.[13] Section Brevitubae includes A. grandidieri and A. suarexensis. These are species with flower buds that set on short pedicles and that are approximately twice as long as wide. The other species are all classified within the section Longitubae. They also have flowers/ fruits set on short pedicels, but the flower buds are 5 or more times as long as wide.

Species[edit]

As of July 2020, there are eight recognized species of Adansonia, with six endemic to Madagascar, one native to mainland Africa and the Arabian Peninsula, and one native to Australia. The mainland African species (Adansonia digitata) also occurs on Madagascar, but it is not a native of that island. Baobabs were introduced in ancient times to south Asia and during the colonial era to the Caribbean. They are also present in the island nation of Cape Verde.[6] A ninth species was described in 2012 (Adansonia kilima Pettigrew, et al.)[13] but is no longer recognized as a distinct species.[14] The African and Australian baobabs are almost identical despite having separated more than 100 million years ago, probably getting to Australia from Africa by oceanic dispersal.[15]

List of species of Adansonia[16]
Species Common names Native range
Adansonia digitata L. (also includes Adansonia kilima[13]) African baobab, dead-rat-tree, monkey-bread-tree, montane African baobab, Gongolaze western, northeastern, central & southern Africa, SW Asia (Yemen, Oman)[17]
Adansonia grandidieri Baill. Grandidier's baobab, giant baobab west central Madagascar[18]
Adansonia gregorii F.Muell. (syn. A. gibbosa) boab, Australian baobab, bottletree, cream-of-tartar-tree, gouty-stem Australia (Northern Territory, Western Australia)[19]
Adansonia madagascariensis Baill. Madagascar baobab northwest and north Madagascar[20]
Adansonia perrieri Capuron Perrier's baobab northern Madagascar[20]
Adansonia rubrostipa Jum. & H.Perrier (syn. A. fony) fony baobab central to south part of western Madagascar[20]
Adansonia suarezensis H.Perrier Suarez baobab northern Madagascar[20]
Adansonia za Baill. za baobab west and southwest Madagascar[20]

Habitat[edit]

The Malagasy species are important components of the Madagascar dry deciduous forests. Within that biome, Adansonia madagascariensis and A. rubrostipa occur specifically in the Anjajavy Forest, sometimes growing out of the tsingy limestone itself. A. digitata has been called "a defining icon of African bushland".[21] The tree also grows wild in Sudan in the regions of Darfur and the state of Kordofan. The locals call it "Gongolaze" and use its fruits as food and medicine and use the tree trunks as reservoirs to save water.

Ecology[edit]

Baobabs store water in the trunk (up to 120,000 litres or 32,000 US gallons) to endure harsh drought conditions.[22] All occur in seasonally arid areas, and are deciduous, shedding their leaves during the dry season. Across Africa, the oldest and largest baobabs began to die in the early 21st century, likely from a combination of drought and rising temperatures.[9] The trees appear to become parched, then become dehydrated and unable to support their massive trunks.[10]

Baobabs are important as nest sites for birds, in particular the mottled spinetail[23] and four species of weaver.[24]

Notable trees[edit]

"Grandmother" Fony baobab

Radiocarbon dating has provided data on a few individuals of A. digitata. The Panke baobab in Zimbabwe was some 2,450 years old when it died in 2011, making it the oldest angiosperm ever documented, and two other trees—Dorslandboom in Namibia and Glencoe in South Africa—were estimated to be approximately 2,000 years old.[25] Another specimen known as Grootboom was dated and found to be at least 1275 years old.[21][26] The Glencoe baobab, a specimen of A. digitata in Limpopo Province, South Africa, was considered to be the largest living individual, with a maximum circumference of 47 m (154 ft)[27] and a diameter of about 15.9 m (52 ft). The tree has since split into two parts, so the widest individual trunk may now be that of the Sunland baobab, or Platland tree, also in South Africa. The diameter of this tree at ground level is 9.3 m (31 ft) and its circumference at breast height is 34 m (112 ft).[25]

Two large baobabs growing in Tsimanampetsotse National Park were also studied using radiocarbon dating.[25] One called Grandmother is made up of three fused trunks of different ages, with the oldest part of the tree an estimated 1,600 years old. The second, "polygamous baobab", has six fused stems, and is an estimated 1,000 years old.[25]

Food uses[edit]

The cut fruit from Mozambique
Baobab powder

Leaves[edit]

Leaves may be eaten as a leaf vegetable.[21]

Fruit[edit]

  • The white pith in the fruit of the Australian baobab (A. gregorii) tastes like sherbet.[28] It has an acidic, tart, citrus flavor.[29] It is a good source of vitamin C, potassium, carbohydrates, and phosphorus.[30]
  • The dried fruit powder of A. digitata, baobab powder, contains about 11% water, 80% carbohydrates (50% fiber),[31] and modest levels of various nutrients, including riboflavin, calcium, magnesium, potassium, iron, and phytosterols, with low levels of protein and fats.[29][32][33] Vitamin C content, described as variable in different samples, was in a range of 74 to 163 milligrams (1.14 to 2.52 gr) per 100 grams (3.5 oz) of dried powder.[29] In 2008, baobab dried fruit pulp was authorized in the EU as a safe food ingredient,[34] and later in the year was granted GRAS (generally recognized as safe) status in the United States.[35]
  • In Angola, the dry fruit of A. digitata is usually boiled and the broth is used for juices or as the base for a type of ice cream known as gelado de múcua.
  • In Zimbabwe, the fruit of A. digitata is eaten fresh or the crushed crumbly pulp is stirred into porridge and drinks.[36]
  • In Tanzania, the dry pulp of A. digitata is added to sugarcane to aid fermentation in brewing (beermaking).[37]

Seed[edit]

Other uses[edit]

Some baobab species are sources of fiber, dye, and fuel. Indigenous Australians used the native species A. gregorii for several products, making string from the root fibers and decorative crafts from the fruits.[40] Baobab oil from the seed is also used in cosmetics, particularly in moisturizers.[41]

Gallery[edit]

References[edit]

  1. ^ "Genus: Adansonia L." Germplasm Resources Information Network. United States Department of Agriculture. 12 November 2008. Archived from the original on 30 May 2010. Retrieved 14 January 2011.
  2. ^ Tropicos.org. Missouri Botanical Garden. 8 Jul 2020 http://www.tropicos.org Archived 23 April 2011 at the Wayback Machine
  3. ^ "The Baobab: Fun Facts About Africa's Tree of Life".
  4. ^ "The baobab, a Malagasy tree – Voyage Tourisme Madagascar". Archived from the original on 9 February 2021. Retrieved 1 May 2020.
  5. ^ Eggli, U.; Newton, L.E. (2004). Etymological Dictionary of Succulent Plant Names. Springer Berlin Heidelberg. p. 3. ISBN 978-3-540-00489-9. Archived from the original on 1 March 2020. Retrieved 25 September 2018.
  6. ^ a b Wickens, G. E.; Lowe, P. (2008). The Baobabs: Pachycauls of Africa, Madagascar and Australia. Springer Verlag. ISBN 978-1-4020-6430-2. OCLC 166358049.
  7. ^ Adrian Patrut et al. (2018) The demise of the largest and oldest African baobabs. Nature Plants 4: 423–426. DOI: 10.1038/s41477-018-0170-5
  8. ^ a b c d e f g h i j k l m n o p q r s t Baum, D.A., 1995, A Systematic Revision of Adansonia (Bombacaceae). Annals of the Missouri Botanical Garden , 1995, Vol. 82, No. 3 (1995), pp. 440-471
  9. ^ a b Ed Yong (11 June 2018). "Trees That Have Lived for Millennia Are Suddenly Dying The oldest baobabs are collapsing, and there's only one likely explanation". The Atlantic. Archived from the original on 9 February 2021. Retrieved 12 June 2018.
  10. ^ a b Rachel Nuwer (12 June 2018). "Last March of the 'Wooden Elephants': Africa's Ancient Baobabs Are Dying". The New York Times.
  11. ^ Kornei, K. 2021. Scientists determine the age of one of Africa’s most famous trees. Science (https://www.science.org/content/article/scientists-determine-age-one-africa-s-most-famous-trees)
  12. ^ Baum, David A. (1995). "The Comparative Pollination and Floral Biology of Baobabs (Adansonia- Bombacaceae)". Annals of the Missouri Botanical Garden. 82 (2): 322–348. doi:10.2307/2399883. ISSN 0026-6493. JSTOR 2399883. Archived from the original on 9 February 2021. Retrieved 21 October 2020.
  13. ^ a b c d Pettigrew, J. D.; et al. (2012). "Morphology, ploidy and molecular phylogenetics reveal a new diploid species from Africa in the baobab genus Adansonia (Malvaceae: Bombacoideae)" (PDF). Taxon. 61 (6): 1240–1250. doi:10.1002/tax.616006.
  14. ^ a b c Cron, Glynis & Karimi, Nisa & Glennon, Kelsey & Udeh, Chukwudi & Witkowski, E & Venter, Sarah & Assogbadio, A & Baum, David. (2016). "One African baobab species or two? A re-evaluation of Adansonia kilima." South African Journal of Botany. 103. 312. 10.1016/j.sajb.2016.02.036.
  15. ^ Baum, David A.; Small, Randall L.; Wendel, Jonathan F. (1998). "Biogeography and floral evolution of baobabs (Adansonia, Bombacaceae) as inferred from multiple data sets". Syst Biol. 47 (2): 181–207. doi:10.1080/106351598260879. PMID 12064226.
  16. ^ "GRIN Species Records of Adansonia". Germplasm Resources Information Network. United States Department of Agriculture. Archived from the original on 24 September 2015. Retrieved 14 January 2011.
  17. ^ Science, Kew. " https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:558628-1". Plants of the World Online. Retrieved 19 February 2022.
  18. ^ Ravaomanalina, H.; Razafimanahaka, J. (2016). "Adansonia grandidieri". IUCN Red List of Threatened Species. 2016: e.T30388A64007143. doi:10.2305/IUCN.UK.2016-2.RLTS.T30388A64007143.en.
  19. ^ Science, Kew. " https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:558631-1". Plants of the World Online. Retrieved 19 February 2022.
  20. ^ a b c d e Behrens, K. and K. Barnes. 2016. Wildlife of Madagascar. Wild guides, Princeton University Press.
  21. ^ a b c "Adansonia digitata (baobab)". Royal Botanic Gardens, Kew. Archived from the original on 20 February 2014. Retrieved 8 June 2014.
  22. ^ "The Baobab tree in Senegal". Archived from the original on 4 October 2008. Retrieved 1 October 2008.
  23. ^ "Species text in The Atlas of Southern African Birds" (PDF). Archived from the original (PDF) on 21 October 2012. Retrieved 30 October 2014.
  24. ^ "Weavers breeding in baobabs". Animal Demography Unit, Department of Biological Sciences, University of Cape Town, South Africa. Archived from the original on 15 September 2015. Retrieved 30 October 2014.
  25. ^ a b c d Patrut A, von Reden KF, Danthu P, Pock-Tsy JM, Patrut RT, Lowy DA (2015). "Searching for the oldest baobab of Madagascar: radiocarbon investigation of large Adansonia rubrostipa trees". PLOS ONE. 10 (3): e0121170. Bibcode:2015PLoSO..1021170P. doi:10.1371/journal.pone.0121170. PMC 4373780. PMID 25806967.
  26. ^ Patrut, A., et al. (2010). Fire history of a giant African baobab evinced by radiocarbon dating. Archived 22 October 2014 at the Wayback Machine Radiocarbon 52(2), 717–26.
  27. ^ "Big Baobab Facts". Archived from the original on 6 January 2008. Retrieved 8 January 2008.
  28. ^ F.A.Zich; B.P.M.Hyland; T.Whiffen; R.A.Kerrigan (2020). "Adansonia gregorii". Australian Tropical Rainforest Plants Edition 8 (RFK8). Centre for Australian National Biodiversity Research (CANBR), Australian Government. Retrieved 23 June 2021.
  29. ^ a b c UK Advisory Committee on Novel Foods and Processes (July 2008). "Baobab dried fruit pulp. EC No. 72; August 2006: Application from PhytoTrade Africa to approve baobab dried fruit pulp of African baobab (A. digitata) as a novel food ingredient. Authorised July 2008". UK Food Standards Agency. Archived from the original on 26 July 2012. Retrieved 3 June 2012.
  30. ^ "Baobab: Benefits, nutrition, dietary tips, and risks". Medical News Today. Archived from the original on 9 February 2021. Retrieved 20 June 2018.
  31. ^ "Nutrition Facts". nutritionvalue.org. Archived from the original on 9 February 2021. Retrieved 20 July 2020.
  32. ^ Osman, M. A. (2004). "Chemical and nutrient analysis of baobab (Adansonia digitata) fruit and seed protein solubility". Plant Foods Hum Nutr. 59 (1): 29–33. CiteSeerX 10.1.1.587.6400. doi:10.1007/s11130-004-0034-1. PMID 15675149. S2CID 23737392.
  33. ^ Chadare, F. J.; et al. (2009). "Baobab food products: a review on their composition and nutritional value". Crit Rev Food Sci Nutr. 49 (3): 254–74. doi:10.1080/10408390701856330. PMID 19093269. S2CID 23498946.
  34. ^ "Baobab dried fruit pulp". UK Food Standards Agency. 2008. Archived from the original on 26 July 2012. Retrieved 3 June 2012.
  35. ^ "GRAS Notice No. GRN 273". US Food and Drug Administration. 25 July 2009. Archived from the original on 9 February 2021. Retrieved 3 May 2018.
  36. ^ "South African villagers tap into trend for 'superfood' baobab". AFP. 24 September 2018. Archived from the original on 9 February 2021. Retrieved 29 September 2018.
  37. ^ Sidibe, M., et al. Baobab, Adansonia digitata L. Volume 4 of Fruits for the Future. International Centre for Underutilised Crops, 2002.
  38. ^ a b Ambrose-Oji, B. and N. Mughogho. 2007. Adansonia grandidieri Baill. Archived 7 April 2014 at the Wayback Machine In: van der Vossen, H. A. M. and G. S. Mkamilo (Eds). PROTA 14: Vegetable oils/Oléagineux. PROTA, Wageningen, Netherlands.
  39. ^ a b Ambrose-Oji, B. and N. Mughogho. 2007. Adansonia za Baill. Archived 2 April 2015 at the Wayback Machine In: van der Vossen, H. A. M. and G. S. (Eds). PROTA 14: Vegetable oils/Oléagineux. PROTA, Wageningen, Netherlands.
  40. ^ "Dance of the baob". The Australian Women's Weekly. National Library of Australia. 2 February 1966. p. 26. Retrieved 11 January 2012.
  41. ^ Vermaak, Ilze; Kamatou, Guy; Komane-Mofokeng, B.; Alvaro, Viljoen; Beckett, Katie (2011). "African seed oils of commercial importance – Cosmetic applications". South African Journal of Botany. 77 (4): 920–933. doi:10.1016/j.sajb.2011.07.003.

External links[edit]