Baeckea gunniana

Baeckea gunniana, commonly known as alpine baeckea, is a species of a compact, densely branched evergreen shrub, growing in alpine and sub-alpine Australia.[1] Baeckea is a genus of flowering plants in the myrtle family, Myrtaceae, comprising 14 species occurring in eastern Australia and Asia.[2]

Baeckea gunniana
Baeckea gunniana Photo © Greg Jordan. © 2019 University of Tasmania
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Myrtales
Family: Myrtaceae
Genus: Baeckea
Species:
B. gunniana
Binomial name
Baeckea gunniana
Schauer ex Walp.
Occurrence distribution of Baeckea gunniana Atlas of Living Australia, Map data © OpenStreetMap, imagery © CartoDB

Description

Baeckea gunniana is a smooth, compact shrub growing to 1.5 m high, although can reach up to 2 m at lower altitudes.[3] It is sometimes prostrate or spreading over rocks and boulders.[4] Branchlets are brown with a flat segment on a papery or fibrous brown bark.[2] Leaves are small (2–4 mm long; 0.6-0.8 mm wide) and crowded, obovate to oblong shaped with a blunt apex,[3] and with entire margins and petioles c. 0.5 mm long.[2] The flowers are white, small and numerous, borne solitarily in the upper leaf axils.[5] Sepals are triangular and obtuse, with a corolla 4–5 mm in diameter and circular petals c. 1–1.8 mm long. Stamens 4–6, not opposite petals. The ovary has a single locule. Style is terete and only slightly inserted into the ovary summit.[3] The unilocular ovary, where the pendulous placenta and ovules are enclosed by a single membrane, is characteristic to the species and unique in the genus.[2]

The fruit is green and cup-like when immature[5] and woody, dehiscent capsule at maturity.[3] Seeds are small and angular, remaining inconspicuous on the ground upon release.[3][5] Seed coat/covering or testa of some Baeckea species has been recorded to form a physical barrier inhibiting seed germination.[3] This may be reverted by removing or nicking the testa using a needle or scalpel, improving the rate of germination.[3] B. gunniana can also be vegetatively propagated from cuttings of semi-hardened new growth.

Distribution and habitat

Distribution is restricted to alpine or subalpine regions, from Mt Ginini in ACT to south-west Tasmania.[3][2] Baeckea gunniana is most prevalent at high altitudes between 1000 to 1400 m. However, it has been observed to grow above 2000 m near Mt Kosciusko, and as low as 450 m in western Tasmania.[2] All species in the genus Baeckea are confined to Australia, except for the type species, B. frutescens (L.), which extends from eastern Australia through Malesia to China.[2]

Baeckea gunniana is commonly found growing with species such as Callistemon pityoides, Epacris paludosa, and Empodisma minus, in heathlands or boggy sedgeland.[2] It is also common near creeks, and sometimes in shaded areas under Eucalyptus spp.[3]

Taxonomy and phylogeny

The species was first formally described by the German botanist Johannes Conrad Schauer in 1843.[6]

The closest Myrtaceae sensu stricto lineage is represented by two fleshy fruited (Myrcianthes and Acmena) and three dry fruited taxa. Angophora and Backhousia are sister genera to Baeckea, belonging to a dry-fruited lineage of Myrtaceae.[7]

Uses and cultivation

Baeckea leaves are edible and often used as a tea substitute because of their aromatic citrus-like flavour.[1][8] Extracts from B. gunniana have been found to inhibit the activity of DNA Polymerase enzyme.[9] It forms an integral part of the Broad-toothed mouse habitat in NSW, Australia, providing protection from predators and other large grazers.[8]

White Myrtaceae flowers of Baeckea gunniana Photo © Greg Jordan. © 2019 University of Tasmania

References

  1. "Key to Tasmanian Dicots". University of Tasmania. Retrieved 28 November 2019.
  2. Bean, Anthony (1997). "A revision of Baeckea (Myrtaceae) in eastern Australia, Malesia and south-east Asia". Telopea. 7 (3): 245–268. doi:10.7751/telopea19971018. ISSN 0312-9764.
  3. "Baeckea gunniana - Growing Native Plants". Australian National Botanic Gardens. Retrieved 28 November 2019.
  4. Walsh, N. Entwisle, Timothy J. (1996). Flora of Victoria. Volume 3, dicotyledons Winteraceae to Myrtaceae. Inkata. ISBN 0-409-30852-8. OCLC 223634887.CS1 maint: multiple names: authors list (link)
  5. "Flora of Victoria". vicflora.rbg.vic.gov.au. Retrieved 4 December 2019.
  6. Australia, Atlas of Living. "Baeckea gunniana". bie.ala.org.au. Retrieved 4 December 2019.
  7. Conti, Elena; Litt, Amy; Wilson, Peter G.; Graham, Shirley A.; Briggs, Barbara G.; Johnson, L. A. S.; Sytsma, Kenneth J. (1997). "Interfamilial Relationships in Myrtales: Molecular Phylogeny and Patterns of Morphological Evolution". Systematic Botany. 22 (4): 629. doi:10.2307/2419432. ISSN 0363-6445. JSTOR 2419432.
  8. Belcher, C.; Leslie, D. (2011). "Broad-toothed RatMastacomys fuscusdistribution in Buccleuch, Bago and Maragle State Forests, NSW". Australian Zoologist. 35 (3): 555–559. doi:10.7882/az.2011.007. ISSN 0067-2238.
  9. Deng, Jing-Zhen; Starck, Shelley R.; Hecht, Sidney M. (2019). "DNA Polymerase β Inhibitors fromBaeckea gunniana". Journal of Natural Products. 62 (12): 1624–1626. doi:10.1021/np990240w. ISSN 0163-3864. PMID 10654412.
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