Trithuria bibracteata is a species of aquatic plant in the family Hydatellaceae endemic to Western Australia.
Description Vegetative characteristics Trithuria bibracteata is a small, annual, aquatic herb with simple, linear, 5-20 mm long, and 0.4 mm wide leaves. The red plants are 1 cm wide, and max. 2 cm high. The short stem bears max. 2 mm long hairs.Cooke, D. A. (1983). Two Western Australian Hydatellaceae. Muelleria, 5, 123-125. Generative characteristics It is monoecious, and the reproductive units ("flowers") are bisexual.Taylor, M. L., Macfarlane, T. D., & Williams, J. H. (2010). Reproductive ecology of the basal angiosperm Trithuria submersa (Hydatellaceae). Annals of Botany, 106(6), 909-920. The reproductive units are sessile, or pedunculate.Sokoloff, D. D., Remizowa, M. V., Yadav, S. R., & Rudall, P. J. (2010). Development of reproductive structures in the sole Indian species of Hydatellaceae, Trithuria konkanensis, and its morphological differences from Australian taxa. Australian Systematic Botany, 23(4), 217-228. The reproductive unit consists of two lanceolate, 2-3 mm long, and 1.2 mm wide involucral bracts, 1-2 stamens, and 6-10 carpels. The dehiscent fruit bears 0.4-0.6 mm long, desiccation-tolerant, black to brown, ellipsoid to ovoid seeds,Trithuria bibracteata Stapf ex D.A.Cooke. (n.d.). Atlas of Living Australia. Retrieved October 29, 2024, from https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2914405#overview which require light to germinate. Flowering occurs from September to November.
Distribution It occurs in the Southwest region of the state Western Australia.
Taxonomy It was described in 1983 as Trithuria bibracteata Stapf ex D.A.Cooke by David Alan Cooke based on previous work by Otto Stapf. The type specimen was collected by R. D. Royce in Boyanup, Western Australia in 1947. It is placed in Trithuria sect. Trithuria.Iles, W. J. D. (2013). The phylogeny and evolution of two ancient lineages of aquatic plants (Doctoral dissertation, University of British Columbia).
Etymology The specific epithet bibracteata is derived from the prefix bi- meaning two,Paleontological Research Institution, Ithaca, New York. (n.d.). Greek & Latin in Botanical Terminology. Digital Atlas of Ancient Life. Retrieved October 29, 2024, from https://www.digitalatlasofancientlife.org/learn/embryophytes/botanical-terminology/Glossary A-H. (n.d.). Missouri Botanical Garden. Retrieved October 29, 2024, from https://www.mobot.org/MOBOT/research/APweb/top/glossarya_h.html and -bracteata meaning "with bracts".A Grammatical Dictionary of Botanical Latin. (n.d.-c). Missouri Botanical Garden. Retrieved October 29, 2024, from http://www.mobot.org/mobot/latindict/keyDetail.aspx?keyWord=bracteateBaptisia bracteata var. leucophaea - Plant Finder. (n.d.). Missouri Botanical Garden. Retrieved October 29, 2024, from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=290598&isprofile=0&n=1 The reproductive units have two bracts.
Conservation It is not threatened.Western Australian Herbarium & Department of Biodiversity, Conservation and Attractions. (n.d.). Trithuria bibracteata D.A.Cooke. Florabase—the Western Australian Flora. Retrieved October 29, 2024, from https://florabase.dbca.wa.gov.au/browse/profile/1139
Ecology Habitat It occurs in clay and mud along stream edges, ephemeral pools,Sokoloff, D. D., Remizowa, M. V., Macfarlane, T. D., Tuckett, R. E., Ramsay, M. M., Beer, A. S., ... & Rudall, P. J. (2008). Seedling diversity in Hydatellaceae: implications for the evolution of angiosperm cotyledons. Annals of Botany, 101(1), 153-164. and swamps.Tillich, H. J., Tuckett, R., & Facher, E. (2007). Do Hydatellaceae belong to the monocotyledons or basal angiosperms? Evidence from seedling morphology. Willdenowia, 37(2), 399-406.Tuckett, R. E., Merritt, D. J., Rudall, P. J., Hay, F., Hopper, S. D., Baskin, C. C., ... & Dixon, K. W. (2010). A new type of specialized morphophysiological dormancy and seed storage behaviour in Hydatellaceae, an early-divergent angiosperm family. Annals of Botany, 105(6), 1053-1061. It inhabits winter-wet habitats, which dry in the Australian summer from December to February. It can occur sympatrically with Trithuria occidentalis.Department of Environment and Conservation (2012) Western Trithuria (Trithuria occidentalis) Interim Recovery Plan 2012–2017. Interim Recovery Plan No. 327. Department of Environment and Conservation, Western Australia
Seed dispersal The desiccation-tolerant seedsDalziell, E. L., Funnekotter, B., Mancera, R. L., & Merritt, D. J. (2019). Seed storage behaviour of tropical members of the aquatic basal angiosperm genus Nymphaea L.(Nymphaeaceae). Conservation Physiology, 7(1), coz021. may be dispersed by water birds.Sokoloff, D. D., Remizowa, M. V., Macfarlane, T. D., Yadav, S. R., & Rudall, P. J. (2011). Hydatellaceae: a historical review of systematics and ecology. Rheedea, 21(2), 115-138.
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