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Bruguiera sexangula

Bruguiera sexangula propagule.jpg
Mature propagules of Bruguiera sexangula, Singapore. Photo: John Yong

Common Names

Upriver Orange Mangrove ([1])

Family

Rhizophoraceae

Name Reference

Bruguiera sexangula (Lour.) Poir.
Bruguiera sexangula propagule growth.jpg
Progression from bud, to flower and propagule in Bruguiera sexangula, Singapore. Photo: John Yong

Origin of Name

Bruguiera is named after the French biologist and explorer Jean-Guillaume Bruguiere (1750-1798), who was famous for his naming of molluscs, marine life and plants.

Sex-angula means 'six-angled' (in Latin), referring to the angular sides of the calyx and hypocotyl of this species ([1]).

Summary

Bruguiera sexangula is a columnar or multi-stemmed tree growing to 20 m with large opposite, glossy leaves. It is found in estuaries along the northern coastline from the Peter John River, Arnhem Bay, Northern Territory to the Herbert River in Queensland.

Species Feature - Open flower showing petals with no hairs at lobe tips ([2]).

Description

Bruguiera sexangula is a columnar or multi-stemmed tree or shrub generally growing to 20 m high (recorded up to 33 m high). It has light brown to grey bark with fine longitudinal fissuring. There are short, fin-like buttresses at the base of the trunk, occasional prop aerial roots and thick knee-like air-breathing roots (pneumatophores).

The leaves are simple, opposite, glossy green, smooth, narrowly elliptic to elliptic-oblong in shape, 8 - 20 cm long, 3 - 7 cm wide, with a pointed apex. The leaves occur in clusters at the end of branches and the petiole is 1.5 - 6 cm long.

The inflorescence is one-flowered and axillary. Flowers have a pink-orange to pale yellowish-green calyx with 10 - 14 calyx lobes, 20-24 stamens and 10 - 12 creamy-orange, bi-lobed petals with no, or minute (less than 0.5 mm long) bristles on each apex and 1 conspicuous bristle in the sinus (indentation between the petal lobes) that is shorter than the petal lobes. The viviparous propagule grows from within the calyx and is cigar-shaped and green, has longitudinal ribbing and is 5 - 12 cm long and 1 - 2 cm wide ( [3], [1], [4], [5]).

Botanical Description

GROWTH FORM


Tree or shrub to 15 m, evergreen, columnar or multi-stemmed; bark grey, fine longitudinal fissuring; stem with fin-like buttresses, occasional prop aerial roots low-placed; roots knee-like pneumatophores.

FOLIAGE


Leaves opposite, simple, elliptic-oblong, glossy green, smooth, 10-20 cm L, 4-7 cm W, margin entire, apex pointed, base cuneate; petiole to 4 cm L, green; stipules paired, lanceolate, occasional pinkish tinge, enclosing terminal bud, to 8 cm L.

REPRODUCTIVE PARTS


Inflorescence axillary, 1-flowered, peduncle 0.5-1.1 cm L; flowers pink-orange to pale yellowish-green, recurved, 3-3.5 cm L; calyx tube turbinate, ribbed, with 12-14 narrow pointed lobes longer than tube, 1.6-1.9 cm L; petals 10-12, creamy orange, 9-15 mm L, bilobed, apices blunt with bristles absent or minute to 0.5 mm L, sinus between with spine not exceeding lobes 4-6 mm L; stamens 20-24, enclosed 2 in each petal, dehiscing precociously; style slender, 12-21 mm L, minutely 3(-4)-lobed stigma; fruit within calyx tube, enlarged, turbinate, ribbed, lobes slightly reflexed; germination viviparous, hypocotyl emergent from calyx during maturation.

DISPERSAL PROPAGULE


Hypocotyl cigar-shaped, terete, stout, green, slight longitudinal ribbing, 5-12 cm L, 1-1.5 cm W, distal tip blunt, buoyant.

([2]).

Bruguiera sexangula.jpeg
Distribution of Bruguiera sexangula in Australia.
Image: Australia's Virtual Herbarium, 2010

Distribution

Bruguiera sexangula is distributed from India to Asia, through the Indonesian Archipelago to New Caledonia and the northern coast of Australia. In Australia, the species occurs in estuaries along the northern coastline from the Peter John River, Arnhem Bay, Northern Territory (12° 15' S, 136° 22’ E) in the west, to the Herbert River, Queensland (18° 31' S, 146° 19’ E) in the east. ([1]). It is rare in the Northern Territory, occurring mostly as scattered individuals and occasionally in significant stands, in north-east Arnhem Land on on Groote Eylandt ([3]).

The restricted nature of this species in the Northern Territory has not been previously recognised due to specimens of B. gymnorhiza and B. exaristata being mistakenly identified as B. sexangula. Miss-identification generally occurs on specimens without petals ([3]).

Localities (not complete):

Habitat

Usually found in the upper reaches of river-dominated estuaries with high rainfall and significant freshwater input, in a variety of substrates. Other Bruguiera, especially B. gymnorhiza, dominate the lower and intermediate sections of these estuaries. It tolerates freshwater to brackish substrates below 33ppt ([3], [1], [11]).

Mid intertidal, upstream estuarine position ([2]).

Biology

Peak flowering occurs in August and September, and maturation of propagules from September to December ([1]).

Associates include: Rhizophora stylosa, Avicennia marina, Camptostemon schultzii and Bruguiera parviflora ([3]).

Biological Interactions  
Group Taxon
  21 taxa
Vascular Plants Acanthus ilicifolius
Vascular Plants Acrostichum speciosum
Vascular Plants Aegiceras corniculatum
Vascular Plants Avicennia marina
Vascular Plants Barringtonia spp.
Vascular Plants Bruguiera gymnorhiza
Vascular Plants Bruguiera parviflora
Vascular Plants Camptostemon schultzii
Vascular Plants Ceriops pseudodecandra
Vascular Plants Cynometra iripa
Vascular Plants Diospyros geminata
Vascular Plants Excoecaria agallocha
Vascular Plants Heritiera littoralis
Vascular Plants Hibiscus tiliaceus
Vascular Plants Nypa fruticans
Vascular Plants Rhizophora apiculata
Vascular Plants Rhizophora mucronata
Vascular Plants Rhizophora stylosa
Vascular Plants Sonneratia alba
Vascular Plants Sonneratia caseolaris
Vascular Plants Xylocarpus granatum

Ethnobotany

In the Philippines timber in harvested, the fruit is used to treat sore eyes, the roots are used as incense and the leaves used to treat tumors ([12]).

Similar Species

Bruguiera can be distinguished from other genera in the Rhizophoraceae family by the number of calyx lobes (8-15). Ceriops spp. have 5 calyx lobes while Rhizophora spp. have 4.

B. sexangula closely resembles B. gymnorhiza as well as Bruguiera X rhynchopetala a hybrid of these two species. This combination of closely related taxa has resulted in considerable confusion and mis-identification for each entity. B. sexangula is distinguished from other Bruguiera by: large solitary-flowered inflorescence with petals having a spine slightly shorter than the paired-lobes, as distinct from from B. parviflora, B. cylindrica and B. hainesii; and, blunt petal lobes with single minute or absent bristles, and relatively short hypocotyls, as distinct from B. gymnorhiza and B. X rhynchopetala. ([2]).

For illustration and further description of the above distinguishing characters see Mangrove Watch Australia: http://www.mangrovewatch.org.au/index.php?option=com_content&view=category&layout=blog&id=35&Itemid=300173

Calyx colour is also a useful character to distinguish between Bruguiera spp. (see image). Not included are Bruguiera exaristata which has a green calyx and B. X rhynchopetala which has a calyx that is green or green with a reddish tinge.

Bruguiera flower comparative.jpg
The calyx colour is useful when identifying the different Bruguiera species. From the left: B. gymnorhiza (red), Bruguiera sexangula (yellow), Bruguiera hainesii (does not occur in Australia), Bruguiera cylindrica (yellowish-green) and Bruguiera parviflora, Singapore. Photo: John Yong

Notes

Flora of Australia Online: http://www.anbg.gov.au/abrs/online-resources/flora/stddisplay.xsql?pnid=48119
Wild Singapore: http://www.wildsingapore.com/wildfacts/plants/mangrove/bruguiera/sexangula.htm

Bruguiera sexangula propagule2.jpg
Mature propagules of Bruguiera sexangula , Singapore. Photo: John Yong

References

  1. Duke, N.C. (2006). Australia's Mangroves. The authoritative guide to Australia's mangrove plants. University of Queensland, Brisbane. (more)
  2. Duke, N. (2011). Mangroves of Australia. Manuscript. Vers.: 27 Sept 2011. (more)
  3. Wightman, G. (2006). Mangroves of the Northern Territory, Australia: identification and traditional use. Northern Territory. Dept. of Natural Resources, Environment and the Arts, Palmerston. (more)
  4. !McCusker, A. (1984). Rhizophoraceae. Flora of Australia. 22: 1-10. (Australian Government Publishing Service: Canberra.) (more)
  5. Ding Hou (1958). Rhizophoraceae. Flora Malesiana. Ser. 1, Vol. 5, (P. Noordhoff Ltd: Groningen.), pp. 429-493. (more)
  6. Bunt, J.S. (1982b). Mangrove Transect Data from Northern Queensland. Coastal Studies Series, Australian Institute of Marine Science AIMS-CS-82-1. Australian Institute of Marine Science. 41 p. Available online: http://data.aims.gov.au/extpubs/attachmentDownload?docID=2326 (more)
  7. Duke, N.C. and Ge, X.-J. (2011). Bruguiera (Rhizophoraceae) in the Indo-West Pacific: a morphometric assessment of hybridization within single-flowered taxa. Blumea 56: 36-48. (more)
  8. Department of Environment, Water, Heritage and the Arts (DEWHA)(2010). Christmas Island National Park. Available at: http://www.environment.gov.au/parks/christmas/index.html (more)
  9. Bunt, J.S. (1997). The Mangrove Floral and Vegetational Diversity of Hinchinbrook Island and the Adjacent Coast. Australian Institute of Marine Science, Townsville. Available online: http://data.aims.gov.au/extpubs/attachmentDownload?docID=3018 (more)
  10. Robertson, A.I., Giddins, R. and Smith, T.J. (1990). Seed predation by insects in tropical mangrove forests: extent and effects on seed viability and the growth of seedlings. Oecologia 83: 213-219. Available online: http://www.springerlink.com/content/h6567208r2v14176/fulltext.pdf (more)
  11. Wells, A.G. (1982). Mangrove vegetation of northern Australia. In. Clough, B.F. (ed.) Mangrove ecosystems in Australia: structure function and management. Australian National University Press, Canberra. (more)
  12. Jara, R.S. (1987). Traditional uses of mangroves in the Philippines. In: Field, C.D. and Dartnall, A.J. (eds.), Mangrove ecosystems of Asia and the Pacific: status, exploitation and management. Australian Institute of Marine Science, Townsville. (more)

Biological Interactions
Relation Taxon GroupSorted ascending
OccursWith Acanthus_ilicifolius Vascular_Plants
OccursWith Acrostichum_speciosum Vascular_Plants
OccursWith Aegiceras_corniculatum Vascular_Plants
OccursWith Avicennia_marina Vascular_Plants
OccursWith Barringtonia_racemosa Vascular_Plants
OccursWith Bruguiera_gymnorhiza Vascular_Plants
OccursWith Bruguiera_parviflora Vascular_Plants
OccursWith Ceriops_pseudodecandra Vascular_Plants
OccursWith Cynometra_iripa Vascular_Plants
OccursWith Diospyros_geminata Vascular_Plants
OccursWith Excoecaria_agallocha Vascular_Plants
OccursWith Heritiera_littoralis Vascular_Plants
OccursWith Hibiscus_tiliaceus Vascular_Plants
OccursWith Nypa_fruticans Vascular_Plants
OccursWith Rhizophora_apiculata Vascular_Plants
OccursWith Rhizophora_mucronata Vascular_Plants
OccursWith Rhizophora_stylosa Vascular_Plants
OccursWith Sonneratia_alba Vascular_Plants
OccursWith Sonneratia_caseolaris Vascular_Plants
OccursWith Xylocarpus_granatum Vascular_Plants
OccursWith Barringtonia Vascular_Plants
Occurs with Camptostemon_schultzii Vascular_Plants