African baobab tree
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African baobab tree ( Adansonia digitata ) |
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The African baobab ( Adansonia digitata ), also African Baobab (from Arabic bu-Hubub called), belongs to the subfamily of Bombacoideae in the family of mallow (Malvaceae). It is one of the most famous and characteristic trees of tropical Africa .
The scientific generic name honors the European discoverer of the tree, the French naturalist Michel Adanson , who laid out Senegal's first botanical garden in Saint-Louis in the 18th century . The specific epithet digitata alludes to the shape of the leaves, which are made up of five to nine individual leaves, reminiscent of the fingers of a human hand.
description
Vegetative characteristics
The baobab tree is characterized by a relatively short, extremely thick trunk. In South Africa, for example, there is a baobab tree in the Letaba district, which is 19 meters high and has a trunk diameter of 10.64 meters. In East Africa , bottle-shaped trunk shapes are very common, in which the trunk tapers sharply at a height of a few meters.
The crown of the tree consists of strong, often misshapen appearing branches that form a broad crown. In the unleafed state, the crown of branches is reminiscent of a root system, which has contributed to the legend that the baobab tree was a tree planted upside down by the devil .
The trunk is often deeply furrowed or has throat depressions. The gray-brown to gray bark is between five and ten centimeters thick. Therefore, the tree can survive smaller bush fires relatively unscathed. It is hard on the outside and fibrous on the inside. Young trees have a taproot first . As the tree ages, a lateral root system develops that extends to a depth of 1.8 meters. In the horizontal direction, the root system extends further than the tree height.
With baobabs, four development phases are distinguished according to the trunk shape: narrow shoots, cone-shaped, bottle-shaped and old. Shoots (up to 10–15 years) initially grow to a height of four to six meters without any pronounced growth in thickness, the branches protrude upwards at an acute angle. At the beginning of the year, the young baobabs grow between 80 and 100 centimeters per year in suitable locations. Then the trunk swells to a cone shape (up to 60 to 70 years), the tree becomes 5 to 15 meters high and up to 7 meters thick, and the tree blooms for the first time. At an age of 30 to 40 years, the branches begin to grow at right angles away from the trunk and from this point on they increase in length. After that, the tree has grown to a height of 10 to 20 meters, the trunk only increases slowly in thickness and develops a bottle shape (200-300 years). A tree can have a trunk diameter of four to five meters by the age of one hundred. Eventually the tree develops a spreading crown and only grows very slowly in width; hollow and multiple stems are often found (age: up to 800 years).
leaves
The baobab tree is a periodically deciduous tree. The simple or hand-shaped, long-stemmed and alternate leaves appear at the branch ends in early summer just before the start of the rainy season and develop completely within four weeks. If there is no rain or if the amount of rain is very low, leaf development is delayed.
Baobabs first shoot leaves of a simple elliptical shape, which, however, are thrown off again very early; even on young plants the leaves are simple. They are followed by shiny green leaves that are five to nine parts. They have a diameter of about 20 centimeters; the leaves or leaflets are each with entire margins and acuminate to acuminate. The petiole is up to 16 inches long.
blossoms
The age at which the tree first sets flowers depends on its area of distribution. In West Africa the baobab tree blooms for the first time at the age of eight to ten years, in East and South Africa at the earliest at 16 years.
The flowers start four weeks after the leaves have developed. The main flowering period is four weeks, while the individual flowers only bloom for 24 hours. During this time it is capable of being pollinated for around 16 to 20 hours.
The hermaphroditic flowers with a double flower envelope usually appear singly or in pairs. The very large flowers are waxy white in color and hang down on long stalks from the leaf axils. They consist of five petals that overlap a little and are 4.5 to 5 inches wide and 12 inches long. As well as a three- to five-lobed, slightly hairy calyx. Each flower contains 720 to 1,600 stamens arranged in the shape of a razor , which have grown together at their base to form a 1.5 to 4.5 centimeter long, narrow tube ( androphor ). The multilocular ovary is constantly above, with a long and projecting stylus having a multilobal scar . Here, too, there are geographical differences. In East and South Africa the flower stalk is only 20 centimeters long, in West Africa it is up to 90 centimeters.
The flowers, which smell unpleasant for people due to their sweet carrion odor, open in the late afternoon and are completely open the next morning. During the night they are pollinated by fruit bats such as the palm and Egyptian bat. The large-eared giant galago , the Senegal galago and various moths also visit the flowers and contribute to a smaller extent to pollination.
Fruits and seeds
After pollination, woody and velvety hairy, non-opening, multi-seeded capsules develop on the long stems within eight months , which are shaped differently depending on the area of distribution. In the baobab trees widespread in Angola , the fruit is elongated, in the other natural areas of distribution it is more egg-shaped to spherical. The fruits hanging down on stems are 25 to 50 centimeters long. During the ripening process, they change color from green to yellow to gray-brown.
The pulp, which is also edible for humans, is white and dry-floury, tastes sour due to the vitamin C content and is of a consistency that is reminiscent of firm, brittle cotton wool. The dark brown seeds of the fruits are embedded in it , which you can break out and also eat. They are relatively smooth, the size of a hazelnut, kidney-shaped and very rich in fat.
Above all, elephants and baboons , but also antelopes and small mammals eat the fruit and also ingest the seeds, which pass through the digestive tract without being unlocked and are picked from the excreted excrement by birds. The seeds remain viable for several years. Their long dormancy probably ends in nature through bush fires , prolonged rainfall or digestion by elephants ( endochory ).
If left untreated, the germination capacity of the seeds is less than 20%. They can be artificially made viable by pouring boiling water over them and leaving them to stand in the liquid for about a day. Depending on the weather conditions, seeds pretreated in this way can germinate after three weeks to six months. Acid treatment and grinding of the thick seed coat can also increase the germination capacity.
Age
The thickness of the trees and their irregular growth has repeatedly led to their age being overestimated. So was David Livingstone convinced that a tree he at Zambezi discovered having an age of at least 4000 years. However, extensive studies in Kenya , Mali , Sudan , Tanzania and Zambia have shown that very few baobabs are older than 400 years.
In 2018, researchers reported the partial or complete death of 9 of the 13 oldest baobabs within the past twelve years. The reason for this is unknown; possibly climate changes would have an influence. According to the study, the world's oldest baobab, Panke in Zimbabwe , died in 2010–2011 after more than 2,500 years (2,429 [± 14] years measured using the radiocarbon method ). The oldest largely intact baobab is now Humani Bedford Old baobab in Zimbabwe with an estimated age of 1,800 years.
Chromosome number
The number of chromosomes is 2n = 160.
Distribution and systematics
The baobab tree is the characteristic tree species of the dry tree savannah of the African lowlands south of the Sahara . In contrast, it is absent in the central African rainforests . The natural distribution area extends from the Sahel zone to the Transvaal . The tree is sensitive to frost, so the southern distribution line is due to the frost line along the 15th parallel.
It shows clear differences in appearance across its distribution area . So far, however, there has been no systematic investigation into whether the differences in the trunk shape and in the shape and size of the flowers and fruits are due to the individual trees belonging to different subspecies. Common companion trees are acacias , umbrella acacias and tamarind trees .
The sun-loving tree is adapted to the semi-arid habitat at an altitude of 450 to 600 meters with annual rainfall between 300 and 500 millimeters due to its special ability to store water. It is therefore most common in these areas. During the rainy season , which lasts between six weeks and five months in its area of distribution, a tree, which can occupy a volume of up to 200 cubic meters, with its spongy fibers sucks up up to 140,000 liters of water, which it stores for the dry season. The trunk can thicken by several centimeters due to the water retention during the rainy season.
Baobab trees are both near the coast and at altitudes up to 1500 m above sea level. To find NN . The occurrence in the coastal forests is probably due to plantings. These areas of distribution are characterized by significantly different levels of precipitation. The species can survive for a long time with annual rainfall below 100 millimeters, conditions such as those found in Mauritania , for example . On the other hand, the baobab tree can cope with comparatively high annual rainfall of 1,400 millimeters and more, especially if it stands on well-drained ground. The baobab does not tolerate waterlogging, heavy clay soils or temporary flooding. It finds the best conditions for growth on calcareous and deep soils.
The baobab was introduced to other regions by humans (so-called hemerochory ). So its occurrence in is Arabia and India probably due to Arab traders that the tree in the folk medicine used and it in India and Arabia in the 13th century introduced . The tree can also be found on the Cape Verde Islands , Madagascar and Sri Lanka as well as in Australia. As an ornamental wood, it is occasionally planted in Florida , Haiti , the Philippines and Java .
Animals of its habitat
Elephants use the baobab tree's ability to store water. They break open the bark of the baobab tree with their tusks, remove the damp fibers inside the tree with their proboscis and chew them to gain moisture. This creates large cavities in the trees that can cause the trees to collapse. Elephants are said to have been killed by baobabs that suddenly fell over.
Large elephant population densities in various national parks have led and still endanger the baobab population, since its natural succession is not sufficient to maintain the population density. There are now so many elephants, especially in the national parks of Zimbabwe , that they endanger the long-term survival of the baobab stocks. In other regions, where agricultural use has intensified due to population pressure, there is a lack of wild animals that spread the baobab seeds. Even if the trees, which are very difficult to clear, are usually left standing when land is used for agricultural purposes, the natural regeneration of the stands is prevented.
The baobab tree is the host plant for a number of insects that are considered to be agricultural pests and a secondary host of some, particularly problematic insect pests for cocoa and cotton plantings . However, baobab tree clearing has shown that if baobab trees are absent, these pests will migrate to other host plants.
The baobab tree also provides shelter and food for numerous other animal species. For example, weaver birds and passerine parrots nest in the crown of the baobab trees ; Galagos seek protection there. Caves in the trunk and branches are used for breeding by blue ruff , kingfishers , barn owls , hornbills and a number of species of long-winged parrots and lovebirds . In some regions, the gray-headed parrot only brooded in caves in the baobab tree. In addition to birds, the fruits of the tree are also eaten by elephants and baboons, as well as antelopes and a number of small mammals.
use
The San , residents of the Kalahari Desert, directly tap the trees' water supply to meet their fluid needs. The flesh, seeds, bark, leaves and sprouts of the baobab tree are also versatile; the tree's hollows are also used to store grain and water.
Similar to the role that lime trees and oaks once played in Central European village life, the baobab tree also plays a major role in African life. Markets, negotiations and other social events take place on centrally located trees in many villages.
African folk medicine
Almost every part of the baobab tree is used in African folk medicine . For example, the fruits are used against infections and diseases such as smallpox and measles . The leaves are used for diseases such as dysentery , diarrhea , colic and gastrointestinal inflammation. The seeds are used as a heart medicine, toothache, liver infections and malaria diseases.
The occurrence of proanthocyanidins in the pericarp of the fruit has been proven biochemically . However, placebo-controlled clinical studies to evaluate the phytopharmacological active ingredients are still pending.
food
The pulp and seeds are rich in protein , carbohydrates and oil and particularly contain the minerals calcium , potassium and magnesium . After the seeds and fibers are removed, the pulp is dried and either eaten unprocessed or mixed in milk or porridges. The oil-rich seeds are pressed into an oil that is rich in palmitic acid and has a high oxidative stability; in powder form it is used to thicken soups . The seeds are also eaten roasted or fermented and used as a spice.
Baobab leaves are also used as vegetables , either being eaten fresh like spinach , or dried and pulverized. 100 grams have an average energy value of 289 kJ (69 kcal ) and contain, among other things, 3.8 grams of protein and 50 milligrams of ascorbic acid . In Nigeria the leaves are called kuka . Kuka soup is a typical specialty for this country.
The fruits are also suitable for making beverages: the pulp can be fermented like a beer. In Sudan , a drink called Tabaldi is made from pulp with water .
Other forms of use
The tree also provides material for clothing , for roofing , neck jewelry , cords and ropes , nets , mats, hats , trays, boxes , baskets and paper . The fibers of the inner bast , which are very durable and strong, are used for this. They are obtained by peeling off the bark of the trees. Similar to cork oaks , the bark regenerates so that the trees can be used repeatedly as suppliers of bast. A red dye is obtained from the roots; the pollen, mixed with water, forms an adhesive . Due to the high proportion of potash , soap is also made from the ashes of various parts of the tree.
Baobabs, which have a hollow trunk, are said to be used as a prison or toilet on occasion; from West Africa it is reported that hollow baobabs also function as burial sites.
The baobab tree, however, is not used in forestry. Due to its elasticity, the light wood is difficult to work with with an ax and it rots very quickly.
Mythology and literature
Because of its appearance, there are several legends about the baobab tree.
According to a widespread belief in Africa, the devil tore up the tree and then stuck it with the branches first in the ground so that the roots now protrude into the air. According to another story, the tree wanted to be more beautiful than any other tree when it was created. When he did not succeed, however, he stuck his head into the earth and the roots protruded towards the sky. Another explanation emerges from the realm of creation mythology: When at the beginning of the world the hyena recognized its own ugliness at first glance into the reflecting water, it was very angry about it. She tore up a baobab and hurled it skyward to meet her Creator, who did this to her. However, the tree missed its target, fell back to the ground, got stuck there in reverse, and has been growing with the roots upwards ever since.
As the seat of gods and spirits, the baobab also plays a role in a number of other African legends and sagas.
In modern West African literature, the baobab is often used as a symbol of traditional African life and untouched, eternal nature. Places with "sacred" baobabs are often used as symbols of the Garden of Eden .
The tree has also found its way into European children's literature . In Antoine de Saint-Exupéry's story, The Little Prince, he worries that baobabs could overgrow his little asteroid and blow up their roots: "The baobabs begin to be small before they get big."
The baobab tree can also occasionally be found as a subject in modern German-language poetry (for example with Paul Celan ). Hans Magnus Enzensberger uses the baobab tree as an image for the neural network .
literature
- Nadja Biedinger: The world of tropical plants. DuMont, Cologne 2000, ISBN 3-7701-5294-8 .
- Roger Blench: The intertwined history of the silk cotton and baobab. In: René Cappers (Ed.): Fields of change. Progress in African archaeobotany. Barkhuis & Groningen University Library, Groningen 2007, pp. 1-19, PDF .
- Pascal Maitre: Baobab - The magic tree. Edition Lammerhuber, Baden, Lower Austria 2017, ISBN 978-3-903101-26-5 .
- Peter Schütt (Ed.): Trees of the tropics. The great encyclopedia. Nikol Verlagsgesellschaft, Hamburg 2004, ISBN 3-933203-79-1 .
- M. Sidibe, JT Williams: Baobab, Adansonia digitata L. (Crops for the Future Vol. 4), International Center for Underutilized Crops, Southampton 2002, ISBN 0-85432-776-2 , online (PDF; 2.7 MB) .
- Rupert Watson: The African Baobab. Struik Publishers, 2007, ISBN 978-1-77007-430-9 .
- Gerald E. Wickens, Pat Lowe: The Baobabs. Pachycauls of Africa, Madagascar and Australia. Springer, 2008, ISBN 978-1-4020-6430-2 .
Web links
- Adansonia digitata at Useful Tropical Plants.
- Adansonia digitata . In: U. Brunken, M. Schmidt, S. Dressler, T. Janssen, A. Thiombiano, G. Zizka: West African plants - A Photo Guide. Senckenberg Research Institute, Frankfurt am Main 2008.
Individual evidence
- ↑ Breitenbach 1985, cited from: M. Johansson: The Baobab tree in Kondoa Irangi Hills, Tanzania. Swedish University of Agricultural Sciences, Minor Field Studies 74, 1999, Uppsala, Sweden, urn : nbn: se: slu: epsilon-s-8038 .
- ↑ M. Sidibe, JT Williams: Baobab. Adansonia digitata L. International Center for Underutilized Crops, Southampton, UK 2002, ISBN 0-85432-776-2 , p. 21.
- ↑ Botany: Ancient baobabs suffer from mysterious tree deaths . ( Spektrum.de [accessed on June 18, 2018]).
- ↑ Adrian Patrut, Stephan Woodborne, Roxana T. Patrut, Laszlo Rakosy, Daniel A. Lowy: The demise of the large largest and oldest African baobabs . In: Nature Plants . June 11, 2018, ISSN 2055-0278 , doi : 10.1038 / s41477-018-0170-5 ( nature.com [accessed June 18, 2018]).
- ^ Adansonia digitata at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
- ↑ Abdelaaty A. Shahat: procyanidins from Adansonia digitata. In: Pharmaceutical Biology. Vol. 44, No. 6, 2006, pp. 445-450.
- ^ Magdi A. Osman: Chemical and nutrient analysis of baobab (Adansonia digitata) fruit and seed protein solubility. In: Plant Foods for Human Nutrition. Vol. 59, No. 1, 2004, pp. 29-33.
- ↑ Chantal. P. Thomson: The Myth of the Garden Eden and the Symbolism of the Baobab Tree in West African Literature. In: Kamal Salhi: Francophone post-colonial cultures: critical essays. Lexington Books, 2003, ISBN 978-0-7391-0568-9 , pp. 90-100.