Adansonia

Adansonia is a genus made up of eight species of medium to large deciduous trees known as baobabs (/ˈbeɪoʊˌbæb/). Previously classified within the family Bombacaceae, they are now placed in the Malvaceae. They are native to Madagascar, mainland Africa[2] and Australia.[3] Trees have also been introduced to other regions such as Asia.[2][4][5] The generic name honours Michel Adanson, the French naturalist and explorer who described Adansonia digitata.[6] The baobab is also known as the "upside down tree", a name that originates from several myths.[7] They are among the most long-lived of vascular plants[8] and have large flowers that are reproductive for a maximum of 15 hours.[9] The flowers open around dusk; opening so quickly that movement can be detected by the naked eye and are faded by the next morning.[9] The fruits are large, oval to round and berry-like and hold kidney-shaped seeds in a dry, pulpy matrix.

For the most common use of "Baobab", see Adansonia digitata.
"Baobab" and "Upside-down tree" redirect here. For the tree in Hyde Park, see Fagus sylvatica § Cultivation. For other use, see Baobab (disambiguation).

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

See Species section

In the early 21st century, baobabs in southern Africa began to die off rapidly from a cause yet to be determined. Scientists believe it is unlikely that disease or pests were able to kill many trees so rapidly, and some speculated that the die-off was a result of dehydration from global warming.[10][11]

Description

General

Baobabs are long-lived deciduous, small to large trees with broad trunks and compact crowns. Young trees usually have slender, tapering trunks, often with a swollen base. The trunk is made of fibrous wood arranged in concentric rings. Tree diameter fluctuates with rainfall so it is thought that water may be stored in the trunk.[9] Baobab trees have two types of shoots – long, green vegetative ones, and stout, woody reproductive ones. Adansonia gregorii is generally the smallest of the baobabs, rarely getting to over 10 m tall and often with multiple trunks.[9] Both A. rubrostipa and A. madagascariensis are small to large trees, from 5 to 20 m (16 to 66 ft) tall.[9] 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.[9]

Leaves

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. 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.[9]

Flowers

Flowers are born near the tips of reproductive shoots, in the axils of the leaves. There is usually only a singe 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.[9]The calyx is usually green (brown in A. grandidieri Baill.) [9] and made up of 5 lobes that 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. 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.[9] 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.[9]

Fruit

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.[9]). 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, so then tend to break open upon landing on the ground. Inside the outer shell, kidney-shaped seeds are set in a dry pulp.[9]

Species
Adansonia grandidieri, Madagascar
Adansonia digitata, Niger

As of July 2020, there were considered to be eight 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.[7] 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]
SpeciesCommon namesRange
Adansonia digitata L. (also includes Adansonia kilima[13])African baobab, dead-rat-tree, monkey-bread-tree, montane African baobabwestern, northeastern, central & southern Africa[17]
Adansonia grandidieri Baill.Grandidier's baobab, giant baobabwest central Madagascar[18]
Adansonia gregorii F.Muell. (syn. A. gibbosa)boab, Australian baobab, bottletree, cream-of-tartar-tree, gouty-stemnorthwestern Australia
Adansonia madagascariensis Baill.Madagascar baobabnorthwest and north Madagascar[19]
Adansonia perrieri CapuronPerrier's baobabnorthern Madagascar[19]
Adansonia rubrostipa Jum. & H.Perrier (syn. A. fony)fony baobabcentral to south part of western Madagascar[19]
Adansonia suarezensis H.PerrierSuarez baobabnorthern Madagascar[19]
Adansonia za Baill.za baobabwest and southwest Madagascar[19]

Habitat

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".[20] 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

Baobabs store water in the trunk (up to 120,000 litres or 32,000 US gallons) to endure harsh drought conditions.[21] 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.[10] The trees appear to become parched, then become dehydrated and unable to support their massive trunks.[11]

Baobabs are important as nest sites for birds, in particular the mottled spinetail[22] and four species of weaver.[23]

Notable trees
"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.[24] Another specimen known as Grootboom was dated and found to be at least 1275 years old.[20][25] 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)[26] 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).[24]

Two large baobabs growing in Tsimanampetsotse National Park were also studied using radiocarbon dating.[24] 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.[24]

Food uses
The cut fruit from Mozambique
Baobab powder
Baobob flower

Leaves

Leaves may be eaten as a leaf vegetable.[20]

Fruit
  • The white pith in the fruit of the Australian baobab (A. gregorii) tastes like sherbet.[27] It has an acidic, tart, citrus flavor.[28] It is a good source of vitamin C, potassium, carbohydrates, and phosphorus.[29]
  • The dried fruit powder of Adansonia digitata, baobab powder, contains about 11% water, 80% carbohydrates (50% fiber),[30] and modest levels of various nutrients, including riboflavin, calcium, magnesium, potassium, iron, and phytosterols, with low levels of protein and fats.[28][31][32] 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.[28] In 2008, baobab dried fruit pulp was authorized in the EU as a safe food ingredient,[33] and later in the year was granted GRAS (generally recognized as safe) status in the United States.[34]
  • In Angola, the dry fruit of Adansonia 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 Adansonia digitata is used in traditional food preparations which include "eating the fruit fresh or crushed crumbly pulp to stir into porridge and drinks".[35]

Seed

Tree

In Tanzania, the dry pulp of A. digitata is added to sugarcane to aid fermentation in brewing (beermaking).[38]

Other uses

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.[39] Oil from the seed is also used in cosmetics, particularly in moisturizers.[40]

References
  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. https://www.abc.net.au/news/2018-08-07/boabs-come-africa-baobabs-evolution/10060946
  3. Tropicos.org. Missouri Botanical Garden. 8 Jul 2020 http://www.tropicos.org
  4. https://www.tripsavvy.com/fun-facts-about-the-baobab-tree-1454374
  5. https://madagascar-tourisme.com/en/what-to-do/fauna-and-flora/baobab/
  6. Eggli, U.; Newton, L.E. (2004). Etymological Dictionary of Succulent Plant Names. Springer Berlin Heidelberg. p. 3. ISBN 978-3-540-00489-9.
  7. Wickens, G. E.; Lowe, P. (2008). The Baobabs: Pachycauls of Africa, Madagascar and Australia. Springer Verlag. ISBN 978-1-4020-6430-2. OCLC 166358049.
  8. 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
  9. 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
  10. 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. Retrieved 12 June 2018.
  11. Rachel Nuwer (12 June 2018). "Last March of the 'Wooden Elephants': Africa's Ancient Baobabs Are Dying". The New York Times.
  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.
  13. 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. 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" (PDF). 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. Gardner, Simon; Sidisunthorn, Pindar; Lai, Ee May (2011). Heritage Trees of Penang. Penang: Areca Books. ISBN 978-9-675-71906-6.
  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. Behrens, K. and K. Barnes. 2016. Wildlife of Madagascar. Wild guides, Princeton University Press.
  20. "Adansonia digitata (baobab)". Royal Botanic Gardens, Kew. Archived from the original on 20 February 2014. Retrieved 8 June 2014.
  21. "The Baobab tree in Senegal". Archived from the original on 4 October 2008. Retrieved 1 October 2008.
  22. "Species text in The Atlas of Southern African Birds" (PDF). Archived from the original (PDF) on 21 October 2012. Retrieved 30 October 2014.
  23. "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.
  24. 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.
  25. 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.
  26. "Big Baobab Facts". Archived from the original on 6 January 2008. Retrieved 8 January 2008.
  27. "Adansonia gregorii". Australian Tropical Rainforest Plants. Retrieved 20 July 2020.
  28. 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. Retrieved 3 June 2012.
  29. "Baobab: Benefits, nutrition, dietary tips, and risks". Medical News Today. Retrieved 20 June 2018.
  30. "Nutrition Facts". nutritionvalue.org. Retrieved 20 July 2020.
  31. 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.
  32. 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.
  33. "Baobab dried fruit pulp". UK Food Standards Agency. 2008. Retrieved 3 June 2012.
  34. "GRAS Notice No. GRN 273". US Food and Drug Administration. 25 July 2009. Retrieved 3 May 2018.
  35. "South African villagers tap into trend for 'superfood' baobab". AFP. 24 September 2018. Retrieved 29 September 2018.
  36. 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.
  37. 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.
  38. Sidibe, M., et al. Baobab, Adansonia digitata L. Volume 4 of Fruits for the Future. International Centre for Underutilised Crops, 2002.
  39. "Dance of the baob". The Australian Women's Weekly. National Library of Australia. 2 February 1966. p. 26. Retrieved 11 January 2012.
  40. 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.
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