Latin name: Casuarina equisetifolia
Source material: Pollen
Common names: Australian pine, Common ironwood, Beefwood, Bull-oak, Whistling-pine, Horsetail tree
Casuarina is a genus of 17 species in the family Casuarinaceae, native to Australia, south-eastern Asia, and islands of the western Pacific Ocean. Once treated as the sole genus in the family, it has now been split into 3 genera. (1) It is widely redistributed in south-eastern China, India, and Australia. (2) C. equisetifolia, C. glauca, and C. cunninghamiana were introduced to Hawaii, the West Indies, and Mexico by the middle to late 1800s, and to Florida shortly thereafter. C. cunninghamiana is also common in southern Spain. (3) Most species are dioecious, but a few are monoecious.
Australian pine tree is an evergreen with native habitats typical of Casuarina, from Burma and Vietnam east to French Polynesia, New Caledonia, and Vanuatu, and south to Australia (the northern part of the Northern Territory, north and east Queensland, and north-eastern New South Wales). It is also found in India and parts of Africa. In West Africa it is known as the Filao Tree and is planted to prevent erosion of sandy soils. (4)
Not to be confused with the pine tree of the coniferous Pinus species, Australian pine tree is a pine-like tree with a large, rather untidy, greyish-green crown. What appear at first to be pine needles are in fact short twigs (0.5-1 mm in diameter, bearing minute scale-leaves in whorls of 6-8), and these are distinguished from pine needles in that the former are jointed, with several nodes and internodes. The fruit resembles a small cone, about 2 cm long and oval. Australian pine tree grows rapidly to 6-35 m within ten years. (5)
Unlike most other species of Casuarina (which are dioecious), it is monoecious, with male and female flowers produced on the same tree. The flowers develop in small catkin-like inflorescences at the ends of shootlets; the male flowers in simple spikes 0.7-4 cm long, the female flowers on short peduncles. The pistillate flowers are found on lower side branches. All species are wind-pollinated. C. equisetifolia and C. glauca pollinate from February through May in the northern hemisphere, while C. cunninghamiana pollinates from September through December, and accounts for almost 80% of pollen in October in southern Spain. (5)
The fruit is an oval woody structure 10-24 mm long and 9-13 mm in diameter. It superficially resembles a conifer cone, being made up of numerous carpels, each containing a single-winged seed 6-8 mm long.
Casuarina species have variable degrees of salt tolerance and grow very rapidly, so they are ideal for planting along sand dunes and as windbreaks to protect citrus orchards. For this reason, they were introduced into many countries. (3) Australian pine tree and C. cunninghamiana were introduced to (among others) Argentina, China, Egypt, Israel, Iraq, Kenya, Mexico, South Africa and the southern United States (in particular, Florida), and are now considered to be an invasive species. (1, 3)
A Spanish study showed that in that country, the pollen season for pine in general is relatively short. The pollen dispersion period occurs during October and November. There is a diurnal pattern, with the most influential variables in dispersion being temperature, sunshine, and rainfall. The highest concentrations of pollen occurred between 12 a.m. and 2 p.m. (6)
Australian pine tree was reported to be a significant contributor to the major tree pollen season (December through May) in the Tampa Bay area, Florida, as well as during a minor season (October and November). (7) Similarly, pollen from Australian pine tree has been recorded in the atmosphere of Darwin, Australia, (8) and Argentina. (9)
This tree is cultivated as an ornamental plant, for shade, as a windbreak, and for dune stabilisation. The wood is used for shingles, fencing, and firewood. (1)
To date no allergens have been characterised.
Cross-reactivity with other members of this distinctive family may be expected. (10)
While there is strong cross-reactivity between Betulaceae and Fagaceae, there are no studies examining Casuarinaceae cross-allergenicity with other sub-order members. (11, 12)
Through the use of rabbit antisera, no cross-antigenicity has been demonstrated between Casuarina and true conifers. (13)
IgE mediated reactions
Asthma and rhinitis occur in sensitised individuals. Skin-prick tests and in vitro tests in these patients have confirmed IgE antibodies to Australian pine tree pollen. (6)
In a study in Málaga, in southern Spain, sensitisation to Australian pine tree pollen was investigated in a non-atopic population of 210 with a previous history of autumn rhinitis or asthma. Six subjects tested positive, and of these, 5 were shown to have serum-specific IgE (RAST class > or = 2) to this pollen. (6)
Australian pine pollen-specific IgE has been demonstrated in 6 of 14 subjects (42%) with a positive nasal challenge, and in 4 of 5 subjects (80%) with a positive bronchial challenge, confirming that Australian pine pollen is an aeroallergen. (14)
Compiled by Dr Harris Steinman, email@example.com
- Wikipedia contributors, ‘Casuarina’, Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Casuarina&oldid=224865585 (accessed 15 July 2008).
- Lewis WH, Vinay P, Zenger VE. Airborne and allergenic pollen of North America. Baltimore, Johns Hopkins University Press, 1983:34-6.
- Weber RW. (On the cover) Australian pine. Ann Allergy Asthma Immunol 2008;100(5):A4.
- Wikipedia contributors, ‘Casuarina equisetifolia’, Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Casuarina_equisetifolia&oldid=223939134 (accessed 15 July 2008).
- Wodehouse RP. Hay Fever Plants, 2nd ed. New York, NY: Hafner 1971:107-10.
- Garcia JJ, Trigo MM, Cabezudo B, Recio M, Vega JM, Barber D, Carmona MJ, Cervera JA, Toro FJ, Miranda A. Pollinosis due to Australian pine (Casuarina): an aerobiologic and clinical study in southern Spain. Allergy 1997;52(1):11-7.
- Bucholtz GA, Lockey RF, Wunderlin RP, Binford LR, Stablein JJ, et al. A three-year aerobiologic pollen survey of the Tampa Bay area, Florida. Ann Allergy 1991;67(5):534-40.
- Stevenson J, Haberle SG, Johnston FH, Bowman DM. Seasonal distribution of pollen in the atmosphere of Darwin, tropical Australia: Preliminary results. Grana 2007;46(1):34-42.
- Nitiu DS. Aeropalynologic analysis of La Plata City (Argentina) during a 3-year period. Aerobiologia. 2006;22(1):79-87.
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
- Niederberger V, Pauli G, Gronlund H, Froschl R, Rumpold H, Kraft D, et al. Recombinant birch pollen allergens (rBet v 1 and rBet v 2) contain most of the IgE epitopes present in birch, alder, hornbeam, hazel, and oak pollen: a quantitative IgE inhibition. J Allergy Clin Immunol 1998;102(4 Pt 1):579-91.
- Weber RW. Cross-reactivity of plant and animal allergens. Clin Rev Allergy Immunol 2001;21(2-3):153-202.
- Yoo TJ, Spitz E, McGerity JL. Conifer pollen allergy: studies of immunogenicity and cross antigenicity of conifer pollens in rabbit and man. Ann Allergy 1975;34(2):87-93.
- Bucholtz GA, Hensel AE 3rd, Lockey RF, Serbousek D, Wunderlin RP. Australian pine (Casuarina equisetifolia) pollen as an aeroallergen. Ann Allergy 1987;59(1):52-6.