Australian tea tree
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Australian tea tree ( Melaleuca alternifolia ) |
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| Melaleuca alternifolia | ||||||||||||
| ( Maiden & Betche ) Cheel |
The Australian tea tree ( Melaleuca alternifolia ) is a species of the genus myrtle heather ( Melaleuca ) in the myrtle family (Myrtaceae).
Some species of the genus Melaleuca , but also from the genera Baeckea , Kunzea and Leptospermum, are called tea trees. The leaves and twig tips of Melaleuca alternifolia are mainly used for the distillation of tea tree oil .
description
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origin of the name
The name "tea tree" comes from the naturalist Joseph Banks , who accompanied James Cook on his first trip. The ship's crew of the South Seas expedition used the leaves of different types of the so-called tea tree to brew a substitute drink, since tea was not available.
Vegetative characteristics
Melaleuca alternifolia is an evergreen shrub or small tree that reaches heights of 2.5 to 14 meters. It has a red-brown, paper-like flaking bark . The bark of young twigs is hairy and silky; the bark of older branches is bare. The leaves are alternate, rarely opposite or arranged in three whorls at the shoot tips, the leaf position distinguishes it from the very similar Melaleuca linariifolia , with which it can form hybrids (alternifolia means alternate leaves). The small petiole is only about 1 mm long. The simple, lanceolate to linear, partly sickle-shaped leaf blade reaches a length of 10 to 32 millimeters with a width of only 0.4 to 1 millimeter, the leaves are narrowed at the base and pointed at the tip, crescent-shaped or flat elliptical in cross-section. The leaves carry numerous, tightly fitting oil glands.
Generative characteristics
The many-flowered, 3 to 5 cm long, silky hairy, spiked inflorescences look like whitish fluff due to the many white stamens of the densely packed flowers. They sit almost end to end on young branches.
The hermaphroditic flowers are radial symmetry and five-fold with a double flower envelope and a bract . Five small sepals are fused with a 3 to 4 millimeter long calyx tube that ends in short calyx lobes. The decrepit free, white petals are 2 to almost 4 millimeters long. Each 30 to 60 white stamens are in five, many-branched, branched and feathery bundles together, they are up to about 2 centimeters long with short anthers . The three-chamber ovary is semi-subordinate to subordinate. The thick stylus is 3 to 4 millimeters long and ends in a cephalic scar .
The flowering period extends from June to February.
The woody capsule fruit is cylindrical with a diameter of 2 to 4 millimeters. When the fruit ripens, the overgrown flower cup remains attached to the capsule.
Occurrence
Melaleuca alternifolia occurs only near the coast in the Australian states of New South Wales and Queensland . The natural occurrence extends from the district of Stanthorpe to the south and east to the area of Lismore and Grafton , a separate ( disjoint ) sub-occurrence also exists at Port Macquarie . The species grows from sea level to around 800 meters above sea level, on temporarily flooded terrain or along watercourses, especially on weakly acidic, loamy alluvial soil made of weathered granite . The locations are frost-free to moderately affected by frost, with high annual rainfall of 750 to 1600 millimeters, with a maximum in summer. The average temperature in the warmest month reaches around 25 to 30 degrees Celsius.
Cultivation
Today the species grows mainly planted in plantations, for the production of tea tree oil, which is obtained from this species to about 99%. The main growing areas in Australia are northern New South Wales and the Atherton Tablelands in Queensland . The total area under cultivation in Australia is around 3000 hectares . The plants are planted in dense rows and, thanks to frequent, mechanical harvesting, remain bush-shaped. The oil is then obtained from the fresh, harvested leaves by distillation, the annual yield is around 450 to 500 tons. Today the tea tree for oil production is also widely planted in other countries, the most important producer after Australia is China with around half of Australian production. In contrast to other Melaleuca species, the Australian tea tree rarely grows wild; problems as an invasive neophyte are not known of this species.
Taxonomy
It was first described in 1905 in the rank of a variety Melaleuca linariifolia var. Alternifolia Maiden & Betche by Joseph Maiden and Ernst Betche in Proceedings of the Linnean Society of New South Wales , Volume 29, Issue 4, p. 742. The rank of a species Melaleuca alternifolia ( Maiden & Betche) Cheel received it in 1924 from Edwin Cheel : Journal and Proceedings of the Royal Society of New South Wales , Volume 58, p. 195. Information on the type material is available: Coff's Harbor to Grafton (JH Maiden and JL Boorman); November, 1903 .
The Australian tea tree belongs to the Melaleuca linariifolia species group according to its morphological characteristics , it can be distinguished from the related species by the position of the leaves, the hairiness of the flower cup and the length of the stamens. The sister group relationship to Melaleuca linariifolia was confirmed by phylogenomic studies. Unexpectedly, the species Melaleuca glauca proved to be closely related to it , which had earlier been mistakenly placed in the genus Callistemon .
use
It is possible that the Aborigines traditionally used the leaves of small-leaved tea tree species such as Melaleuca alternifolia as a wound dressing. Commercial use of the Australian tea tree for oil production began after AR Penfold described medicinal properties in the 1920s as part of a major study of Australia's vegetable essential oils . Initially, the tea tree oil was obtained from wild stocks. The plant material was hand cut and distilled on site in makeshift, mobile, wood-fired bush shelters. This is how the industry produced tea tree oil for several decades. Melaleuca alternifolia is the economically most important species, also for (alternative) medicinal purposes.
Individual evidence
- ↑ a b c Datasheet at New South Wales Flora online , last accessed 9 August 2017.
- ↑ Website of an encyclopedia of medicinal plants with further references , accessed on January 25, 2020. Entry in aponet.de , accessed on January 25, 2020.
- ↑ a b c d Joseph J. Brophy, Lyndley A. Craven, John C. Doran: Melaleucas: their botany, essential oils and uses. ACIAR Monograph No. 156. Australian Center for International Agricultural Research. Canberra. 415 pages. ISBN 978-1-922137-52-4 , Australian Center for International Agricultural Research (ACIAR) (Part Species A – Z, PDF; 26.4 MB) .
- ^ A b Edwin Cheel : Journal and Proceedings of the Royal Society of New South Wales. Volume 58, 1924, p. 195, scanned at biodiversitylibrary.org .
- ↑ Melaleuca alternifolia at Tropicos.org. Missouri Botanical Garden, St. Louis, Retrieved August 13, 2017.
- ↑ a b Data sheet at Vascular Plants - APNI = Australian Plant Name Index ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .
- ^ A b Lyn A. Craven: Behind the Names: Botany of Tea Trea, Cajaput and Niaouli . In: Ian Southwell, Robert Lowe (Eds.): Tea Tree - The Genus Melaleuca . Harwood Academic Publishers, Amsterdam 1999, ISBN 90-5702-417-9 , pp. 13 ( PDF ). PDF ( Memento of the original from August 9, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Robert D. Edwards, Lyn A. Craven, Michael D. Crisp, Lyn G. Cook: Melaleuca revisited: cpDNA and morphological data confirm that Melaleuca L. (Myrtaceae) is not monophyletic. In: Taxon. 59 (3), 2010, 744-754, JSTOR 25677666 .
- ^ Ian Southwell: Introduction . In: Ian Southwell, Robert Lowe (Eds.): Tea Tree - The Genus Melaleuca . Harwood Academic Publishers, Amsterdam 1999, ISBN 90-5702-417-9 , pp. 1-2 ( PDF ). PDF ( Memento of the original from August 9, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ A b C. F. Carson, KA Hammer, TV Riley: Melaleuca alternifolia (Tea Tree) Oil: A Review of Antimicrobial and Other Medicinal Properties. In: Clin. Microbiol. Rev. Volume 19 (1), 2006, pp. 50-62, doi : 10.1128 / CMR.19.1.50-62.2006 , PMID 16418522 , PMC 1360273 (free full text).
- ↑ B. Kränke: Allergizing potency of tea tree oil. In: The dermatologist. Issue 3/1997, Volume 48, pp. 203-204, doi : 10.1007 / s001050050572 .
Web links
- New South Wales Flora Online datasheet last accessed 9 August 2017.
- Distribution map at the Australasian Virtual Herbarium , accessed August 6, 2019.