Banksia sphaerocarpa
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| Banksia sphaerocarpa R.Br. |
The Fox Banksia or Round-fruit Banksia (Banksia sphaerocarpa) is a species of shrub in the plant genus Banksia. It occurs widely throughout southwest Western Australia, and also extends north along the west coast as far as Geraldton.
[edit] Ecology
B. sphaerocarpa is one of five closely related Banksia species that have highly unusual flower nectar. Whereas other Banksia species produce nectar that is clear and watery, the nectar of these species is pale yellow initially, but gradually becomes darker and thicker, changing to a thick, olive-green mucilage within one to two days of secretion, and eventually becoming "an almost black, gelatinous lump adhering to the base of the flowers".[1] It was first noted by Byron Lamont in 1980; he attributed it to cyanobacteria that feed off the nectar sugars. Noting that many of these cyanobacteria had heterocysts, he speculated that they aid the plant by fixing atmospheric nitrogen, which is then washed off the flower heads by rain, and absorbed by the proteoid root mat. This purported symbiosis was investigated by Barrett and Lamont in 1985, but no evidence of nitrogen fixing was found.[2] Further investigation by Markey and Lamont in 1996 suggested that the discolouration is not caused by cyanobacteria or other microorganisms in the nectar, but is rather "a chemical phenomenon of plant origin". Their analyses indicated that the nectar had unusually high levels of sugar and free amino acids,[3] but three of these species, including B. sphaerocarpa, have since been shown to have normal nectar sugar compositions.[4]
[edit] References
- George, Alex (1981). "The Genus Banksia L.f. (Proteaceae)". Nuytsia 3 (3): 239–473.
- George, Alex (1999). "Banksia", in Wilson, Annette (ed.): Flora of Australia: Volume 17B: Proteaceae 3: Hakea to Dryandra. CSIRO Publishing / Australian Biological Resources Study, 175–251. ISBN 0-643-06454-0.
- Taylor, Anne and Hooper, Stephen D. (1988). The Banksia Atlas (Australian Flora and Fauna Series Number 8). Australian Government Publishing Service, Canberra. ISBN 0-644-07124-9.
- ^ Lamont, Byron B. (1980). "Blue-green algae in nectar of Banksia aff. Sphaerocarpa". West Australian Naturalist 14 (7): 193–194.
- ^ Barrett, Gregory J. and Byron B. Lamont (1985). "Absence of nitrogen fixation (acetylene reduction) by procaryotes in nectar of Banksias". Plant and Soil 85: 443–445.
- ^ Markey, Adrienne S.; Byron B. Lamont (1996). "Why do some banksias have green nectar?". International Symposium on the Biology of Proteaceae. (only abstract sighted)
- ^ Nicolson, Susan W. and Ben-Erik Van Wyk (1998). "Nectar sugars in Proteaceae: Patterns and processes". Australian Journal of Botany 46: 489–504.
[edit] External links
- Banksia sphaerocarpa. Flora of Australia Online. Department of the Environment and Heritage, Australian Government.
- Banksia sphaerocarpa. FloraBase. Department of Environment and Conservation, Government of Western Australia.
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