Trithuria submersa

Trithuria submersa is a species of plant in the family Hydatellaceae endemic to the Australian states New South Wales, South Australia, Tasmania, Victoria, and Western Australia.

Description

Vegetative characteristics

It is a 8 cm tall, and 2-5 cm wide, annual herb with glabrous, red, 15–40(–50) mm long, and up to 1 mm wide leaves and fibrous roots. Individuals growing submerged in water are slender and green in colour.

Generative characteristics

It is a monoecious species with emergent, bisexual reproductive units ("flowers"). The several 2–3 mm wide reproductive units consist of (5–)10–32(–40) mm long stalks, (2–)4–8 ovate to lanceolate, 2–4 mm long bracts, 10–20(–35) carpels with 3-6 stigmatic hairs, and 2–4 central stamens with 2 mm long red filaments and purple anthers, which are 0.6 mm long. The three-ribbed, obovoid, 0.5–0.8 mm long fruit bears sculptured, brown, 0.5 mm long, and 0.3 mm wide seeds. It is a self-pollinating species. Flowering and fruiting occurs from September to January. Seed germination occurs in winter, once the seasonally dry habitat becomes wet.

Cytology

The diploid chromosome count is 2n = 56.

Taxonomy

It was published by Joseph Dalton Hooker in 1858. The lectotype was collected by R.C. Gunn in Macquarie River, Tasmania, Australia on the 6th of November 1845. It is the type species of its genus. It is placed in Trithuria sect. Trithuria.

Etymology

The specific epithet submersa, meaning "underwater", refers to the species aquatic habitat.

Distribution

It is endemic to the Australian states New South Wales, South Australia, Tasmania, Victoria, and Western Australia.

Conservation

Under the Threatened Species Protection Act 1995, it is classified as rare.

Ecology

It occurs in temporary pools, at the edge of streams, and seasonal swamps.

References