Trithuria

Trithuria is a genus of small aquatic herb, which represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand.[1][2] Most of the 12 formally characterised species of Trithuria are found in Australia, with the exception of T. inconspicua and T. konkanensis, which are found in New Zealand and India, respectively.[3][4]

Trithuria
Trithuria submersa
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Order: Nymphaeales
Family: Hydatellaceae
Genus: Trithuria
Hook.f.
Type species
Trithuria submersa
Synonyms[1]
  • Hydatella Diels
  • Juncella F.Muell. ex Hieron.

These diminutive, moss-like, aquatic plants are the closest living relatives of the two closely related families Nymphaeaceae (water-lilies) and Cabombaceae.[5] Together, these three families compose the order Nymphaeales in the APG III system of flowering plant classification. Trithuria (Hydatellaceae) diverged from the rest of Nymphaeales soon after Nymphaeales diverged from its sister taxon, which comprises all of the flowering plants except the two orders Nymphaeales and Amborellales.

Taxonomy

The genus Hydatella was recently subsumed into Trithuria based on the following morphological synapomorphies:[3]

  • lack of a vascular cambium,
  • lack of pericyclic sclerenchyma,
  • anomocytic stomata,
  • truncate anther connective,
  • boat-shaped pollen,
  • inner integument with two cell layers,
  • palisade exotesta,
  • seed operculum formed by cell enlargement in the inner integument,
  • perisperm and
  • hypogeal germination.[6]

Species and distribution
  1. Trithuria austinensis D.D.Sokoloff - Western Australia
  2. Trithuria australis (Diels) D.D.Sokoloff - Western Australia
  3. Trithuria bibracteata Stapf ex D.A.Cooke - Western Australia
  4. Trithuria cookeana D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Northern Territory of Australia
  5. Trithuria cowieana D.D.Sokoloff - Northern Territory
  6. Trithuria filamentosa Rodway - Tasmania
  7. Trithuria inconspicua Cheeseman - North Island of New Zealand
  8. Trithuria konkanensis S.R.Yadav & Janarth. - Maharashtra
  9. Trithuria lanterna D.A.Cooke - Northern Territory, Western Australia, Queensland
  10. Trithuria occidentalis Benth. - Western Australia
  11. Trithuria polybracteata D.A.Cooke ex D.D.Sokoloff, Remizowa, T.D.Macfarl. & Rudall - Western Australia
  12. Trithuria submersa Hook.f. - Western Australia, South Australia, Victoria, New South Wales, Tasmania

References
  1. Kew World Checklist of Selected Plant Families
  2. Marques, Isabel; Montgomery, Sean A.; Barker, Michael S.; Macfarlane, Terry D.; Conran, John G.; Catalán, Pilar; Rieseberg, Loren H.; Rudall, Paula J.; Graham, Sean W. (2016-04-01). "Transcriptome-derived evidence supports recent polyploidization and a major phylogeographic division in Trithuria submersa (Hydatellaceae, Nymphaeales)". New Phytologist. 210 (1): 310–323. doi:10.1111/nph.13755. ISSN 1469-8137. PMID 26612464.
  3. Dmitry D. Sokoloff, Margarita V. Remizowa, Terry D. Macfarlane, and Paula J. Rudall. 2008. "Classification of the early-divergent angiosperm family Hydatellaceae: one genus instead of two, four new species and sexual dimorphism in dioecious taxa". Taxon 57(1):179-200.
  4. Yadav SR, Janarthanam MK. 1995 Trithuria konkanensis (Hydatellaceae), eine neue Art aus Indien. Aqua Planta 20. (3): 91-97 (1995).
  5. Else Marie Friis & Peter Crane (15 March 2007), "Botany: New home for tiny aquatics", Nature, 446 (7133): 269–270, doi:10.1038/446269a, PMID 17361167
  6. Jeffery M. Saarela1; et al. (15 March 2007), "Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree", Nature, 446 (7133): 312–315, doi:10.1038/nature05612, PMID 17361182
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