Olearia ledifolia

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Olearia ledifolia
O.ledifolia (2).jpg
Scientific classification edit
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Olearia
Species:
O. ledifolia
Binomial name
Olearia ledifolia
(DC.) Benth., 1867
Olearia ledifolia distribution map. source: Australian virtual Herbarium
Olearia ledifolia dry inflorescence and pappus

Olearia ledifolia, commonly known as the rock daisy bush, is a flowering shrub of the family Asteraceae. It is endemic to Tasmania and found at higher altitudes where it grows as a low, compact bush with tough leathery leaves and bears numerous small white daisy-like flowers in summer.[1] The specific name ledifolia is derived from the Greek 'ledos' (woollen cloth) and the Latin 'folium' (leaf), referring to the hairy under surface of the leaves.[2] It was initially described as Eurybia ledifolia by J.D. Hooker in 1860 and then as O. ledifolia by George Bentham in the 1867 census 'Flora Australiensis: a description of the plants of the Australian territory'.[3][4]

Description[]

Olearia ledifolia typically forms a compact, low lying and rigid shrub about 0.5m tall. The branches are numerous and densely packed with young growth covered in fine rust-coloured hairs. The lower sections of the branches may have raised scars from leaves that abscise after 1– 2 years.[1][5] The dark green leaves are tough and leathery, oblong, approximately 12mm – 14mm long and arranged alternately along the stems. The upper surface of the leaf is usually glabrous, with the lower surface strongly revolute having the margins of the leaf rolled down and inwards.[6] The abaxial leaf surface is covered in fine hairs that may appear rusty brown to silver.[5][7]

Like other members of the Asteraceae family, the flowers are a compact Inflorescence consisting of a capitulum containing numerous florets, surrounded by involucral bracts.[8] The flowers are daisy-like in appearance; with 10 – 12 small, white ray florets approximately 10mm across, and deep yellow disc florets. These are borne singularly on short peduncles in the leaf axils near the tips of branches. The fruit is a shiny, glabrous achene[1][9] with seed dispersal being assisted by dry, wind borne pappus.[4][5] Flowering occurs in the southern hemisphere summer months of January and February.[1][5]

Distribution and habitat[]

Olearia ledifolia is endemic to the island state of Tasmania and has been recorded on King Island.[5][10] It is a common species in alpine heath, bolster heath, deciduous heath, fjaeldmark, alpine sedgeland and coniferous heath at altitudes above 1000m.[7][11] Its common name, the rock daisy bush, refers to its preference for sheltered rocky slopes and scree fields amongst mountain plateaus.[2]

Ecology[]

Olearia ledifolia may become a co-dominant species at higher altitudes where the growth of trees is limited by climatic factors. These environments are subject to snow and ice, low temperatures, strong winds and high UV levels.[12] The primary threat to the plant communities where O. ledifolia grows is fire, with frequent burning greatly decreasing the likelihood of recovery and leading to species impoverishment.[11][12] However, it is unclear what the response of O. ledifolia is to fire at the species level.[13] Other threats include trampling, grazing pressures from livestock and climate change.[11][14]

Strongly revolute leaf margins are a frequently recorded xeromorphic adaptions for plants that are subject to water stress, especially when coupled with growths of hair like trichomes.[15] The morphology of the leaf serves to increase the boundary layer between the stomata positioned on the underside of the leaf and the external desiccating environment, thus preventing water loss during gas exchange.[15][16] The classically thin skeletal soils of alpine Tasmania where O. ledifolia occurs have limited water holding capacity and are often subject to summer drought conditions.[12]

Similar species[]

Due to its growth habit and the leaf morphology, Olearia ledifolia bears strong superficial resemblance to Orites revoluta (a member of the Proteaceae family) when not bearing reproductive structures.[6][7] Compounding possible misidentification, these species are regularly found growing in close association with each other.[11] The two species can be separated by the lack of hairy follicles on the leaves, Proteaceous flowers and splitting follicles of O. revoluta.[1]

Cultivation[]

Olearia ledifolia is rarely cultivated because of its restrictive habitat requirements. However, surface sowing of freshly collected seed that has been allowed to dry has yielded some success, with germination occurring in 2 – 5 weeks. It prefers well-drained, moist, acidic soil in full sun and is frost and wind tolerant. It has proven resistant to the soil-borne disease Phytophthora cinnamomi, but it is intolerant to phosphorus.[1][9]

References[]

  1. ^ a b c d e f Howells, Christine (2012). Tasmania's natural flora (Second ed.). Hobart, Tasmania. ISBN 978-0-909830-66-3. OCLC 803605684.
  2. ^ a b Wapstra, Mark (2010). Tasmanian plant names unravelled. Launceston, Tas: Fullers Bookshop. ISBN 9780980472028.
  3. ^ "Olearia ledifolia (DC.) Benth. — The Plant List". www.theplantlist.org. Retrieved 2021-03-15.
  4. ^ a b Bentham, George; Mueller, Ferdinand von (1866). Flora australiensis: a description of the plants of the Australian territory. Vol. 3. London: L. Reeve and co.
  5. ^ a b c d e A guide to flowers & plants of Tasmania. Mary Cameron, Launceston Field Naturalists Club (Rev. ed.). Frenchs Forrest, N.S.W.: New Holland. 1999. ISBN 1-876334-35-5. OCLC 222625500.{{cite book}}: CS1 maint: others (link)
  6. ^ a b "Key to Tasmanian Dicots". www.utas.edu.au. Retrieved 2021-03-15.
  7. ^ a b c Kirkpatrick, J. B. (1997). Alpine Tasmania : an illustrated guide to the flora and vegetation. Peter Dombrovskis, Georgina Davis, Jo Eberhard. Melbourne: Oxford University Press. ISBN 0-19-553753-X. OCLC 37215997.
  8. ^ "Descriptions of Dicot families". www.utas.edu.au. Retrieved 2021-03-15.
  9. ^ a b "Family Index". www.understorey-network.org.au. Retrieved 2021-03-15.
  10. ^ Herbaria, jurisdiction:Australian Government Departmental Consortium;corporateName:Council of Heads of Australasian. "Partners". avh.ala.org.au. Retrieved 2021-03-15.
  11. ^ a b c d From Forest to Fjaeldmark : descriptions of Tasmania's vegetation. Stephen Harris, Anne Kitchener, Water, and Environment Tasmania. Department of Primary Industries. Hobart: Dept. of Primary Industries, Water and Environment. 2005. ISBN 0-7246-6364-9. OCLC 183151378.{{cite book}}: CS1 maint: others (link)
  12. ^ a b c Vegetation of Tasmania. James B. Reid, Australian Biological Resources Study. [Canberra, A.C.T.]: Australian Biological Resources Study. 2005. ISBN 0-646-44512-X. OCLC 224722819.{{cite book}}: CS1 maint: others (link)
  13. ^ Kirkpatrick, J. B.; Dickinson, K. J. M. (1984). "The Impact of Fire on Tasmanian Alpine Vegetation and Soils". Australian Journal of Botany. 32 (6): 613–629. doi:10.1071/bt9840613. ISSN 1444-9862.
  14. ^ "Alpine Vegetation | Department of Primary Industries, Parks, Water and Environment, Tasmania". dpipwe.tas.gov.au. Retrieved 2021-03-15.
  15. ^ a b Response of plants to multiple stresses. Harold A. Mooney. San Diego: Academic Press. 1991. ISBN 1-299-19283-1. OCLC 817706274.{{cite book}}: CS1 maint: others (link)
  16. ^ Fahn, Abraham (1986-05-01). "Structural and Functional Properties of Trichomes of Xeromorphic Leaves". Annals of Botany. 57 (5): 631–637. doi:10.1093/oxfordjournals.aob.a087146. ISSN 0305-7364.
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