Bowiea volubilis
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| Bowiea volubilis | ||||||||||||
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Bowiea volubilis , habit and flowers, on the right is the green tuber. |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Bowiea | ||||||||||||
| Harv. ex Hook.f. | ||||||||||||
| Scientific name of the species | ||||||||||||
| Bowiea volubilis | ||||||||||||
| Harv. ex Hook.f. |
Bowiea volubilis ( Syn .: Schizobasopsis volubilis (Harv. Ex Hook. F.) Macbr., Ophiobostryx volubilis Skeels, Bowiea kilimandscharica Mildbraed), also called Zulu potato , climbing potato or climbing onion , is a species ofthe hyacinth aceae family . B. volubilis is the only species of the monotypic genus Bowiea . This is only divided into the two subspecies ssp. volubilis and ssp. garipensis . The genus was named in honor of the English botanist James Bowie .
features
This climbing, perennial, succulent plant reaches heights of growth of several meters. This geophyte has a green to whitish bulb with a diameter of over 10 cm to 25 cm. Most of the time, part of the fleshy onion is above ground. Occasionally, daughter onions also form. The peel of the onion is not dry, but rather fleshy. The plant does not develop any, or only very small, scale-shaped, quickly ephemeral leaves. The green, climbing stem axis takes over photosynthesis . Only the green onion can be seen during the dry season.
The succulent, twisting and leafless inflorescence has small, greenish flowers. These are inconspicuous and threefold. Two-compartment capsules with numerous black seeds develop from the flowers . The growing season and flowering time is in winter. If the onion is completely covered by the ground, this usually leads to increased growth of the storage organ.
The chromosome number for both subspecies is 2n = 20.
The Bowiea is very robust and also suitable for indoor cultivation, but contact with the onion can lead to skin irritation.
A specialty of the plant is the behavior of its climbing shoots. While most climbing plants are either strict left winds or strict right winds , Bowiea volubilis can wind right and left at will. The plant is therefore a so-called "all-rounder". Another example of an all-round winder is the knotweed .
Occurrence
The Zulu potato is widespread in South and East Africa, especially in South Africa , Zimbabwe , Malawi , Zambia and Tanzania . Outside of the tropics, the species is occasionally grown in greenhouses.
Systematics
One can distinguish between two subspecies:
- Bowiea volubilis subsp. gariepensis (van Jaarsv.) Bruyns : It occurs from Namibia to the Western Cape.
- Bowiea volubilis subsp. volubilis : It occurs from Ugande to southern Africa.
use
Traditionally, its use as a remedy in Africa is widespread and used for various ailments. The not precisely defined spectrum of application can lead to fatal poisoning due to an overdose.
Active ingredients
The parts of the plant contain several bufadienolides as active ingredients , which are structurally related to bovoside A. The main aglycs are bovoruboside, bovokryptoside and bovogenin A. The bufadienolide content of the onion is about 0.4 mg / g.
Symptoms
Ingesting a concentrated decoction of the Zulu potato quickly leads to death from heart failure, which can occur after just a few minutes. The symptoms include nausea, vomiting, increased salivation, cramps, gastrointestinal discomfort and severe diarrhea. In addition, there is general exhaustion and dysfunction of breathing and heart, such as arrhythmias , hypertension , coma and cardiac arrest. All in all, symptoms that are typical for poisoning with cardiac glycosides . Skin irritation on contact with plant material is also described.
pharmacology
The active ingredients are classified as extremely toxic cardiac poison (Ia). The onions and parts of the plants above ground are particularly toxic. These are about 30 times more toxic than digitalis and have resulted in many human and animal deaths in Africa. However, animal poisoning is rare. The mean lethal dose (LD 50 ) for the main bufadienolides in a cat is 0.11–0.19 mg / kg for intravenous administration. In sheep, eating about 15 grams of fresh onion material can cause death. The bufadienolides inhibit the Na + , K + - ATPase and therefore act as strong nerve and cell toxins. This membrane-based ion pump, which is necessary for the development of ion gradients, is of essential importance for axonal stimulus transmission and active secondary transport processes. If this ATPase is inhibited, this leads to an interruption of the neuromuscular stimulus conduction and thus to cardiac arrest. The mode of action corresponds to that of other cardiac glycosides. Bovoside A accumulates in the body similar to digitoxin .
First aid
Immediate action is required if plant material, cardiac glycosides isolated from it or if injured by arrows poisoned with the active ingredients are ingested. After the induction of vomiting, further detoxification measures must be carried out, as are typical for the treatment of poisoning with cardiac glycosides.
literature
- Ewald Kleiner: Bowiea volubilis , Kuas , Heft 8, 1980, pages 240-241.
- Michael Wink, Ben-Erik van Wyk, Coralie Wink: Handbook of poisonous and psychoactive plants. Wissenschaftliche Verlagsgesellschaft, Stuttgart 2008. ISBN 3804724256
Individual evidence
- ^ Tropicos. [1]
- ↑ a b c Rafaël Govaerts (ed.): Bowiea. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved September 4, 2016.
Web links
- Compact information on the species and its care. (engl.)
- Compact information on the species and its care. There it is written: very toxic. Other authors write that the tuber is edible. (engl.)
- Bowiea volubilis at giftpflanze.com.
- On the toxicity of the species. (Engl.)