Seeds of South Australia
Trithuria submersa (Hydatellaceae)
List of species for Trithuria
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Seed collecting:
September to October
Herbarium regions:
Eyre Peninsula, Southern Lofty, Kangaroo Island, South Eastern
NRM regions:
Adelaide and Mount Lofty Ranges, Eyre Peninsula, Kangaroo Island, South East
IBRA regions
Glenelg Plain (NCP02)Naracoorte Coastal Plain
 Rare   (IUCN: RA d(i,ii))
Lucindale (NCP03) 
 Rare   (IUCN: RA d(ii))   [localised]
Tintinara (NCP04) 
 Rare   (IUCN: RA d(i,ii))
Kangaroo Island (KAN01)Kanmantoo
 Rare   (IUCN: RA d(ii))
Fleurieu (KAN02) 
 Vulnerable   (IUCN: VU D2)   [only records from Big Flat]
Eyre Hills (EYB03)Eyre Yorke Block
 Critically Endangered   (IUCN: CR B2ab(i,ii,iii))   (Definite Decline)   [needs water]
Lowan Mallee (MDD04)Murray Darling Depression
 Vulnerable   (IUCN: VU D2)   (Probable Decline)
Wimmera (MDD05) 
 Data Deficient   [imprecise location]
RSCA map:
Regional Species Conservation Assessments per IBRA subregion. Please click the thumbnail map.
AVH map:
Australian distribution map (external link)
SA Census:
Census of South Australian plants (external link)     [genus Trithuria]
Name derivation:
Trithuria from the Greek 'treis' meaning three and 'thyris' meaning window; referring to the dehiscence of the fruit of this species. Submersa meaning underwater; referring to the species aquatic habitat.
Winter annual growing in mud of stream margins, seasonal swamps and pools on Kangaroo Island and the Southeast in South Australia with isolated collections from Eyre Peninsula and Mount Lofty Ranges. Also found in Western Australia, New South Wales, Victoria and Tasmania.
Native. Uncommon in South Australia. Common in the other states.
Plant description:
Annual herb, usually becoming reddish. Leaves glabrous, straight, narrow-linear, acute, to 4 cm long and 1 mm wide. Capitula numerous, scapose rarely sessile, scapes erect, filiform, unbranched, accrescent, to 5 cm high, leafless, glabrous; involucre spreading; bracts 4-6, acuminate, 1-veined, subequal, 3-4 mm long, glabrous; male florets 2-5; anther oblong, c. 0.6 mm long, purple; filament 1-2 mm long, rigid; female florets 10-25, c. 2 mm long, densely packed in a hemispherical cluster; stigmatic hairs 3-6.
Fruit type:
Tiny ovoid capsule to 0.6 mm long, splitting along the 3 ribs, with 3 panels attached at the apex and opening outwards from the base after falling from the pedicel.
Seed type:
Tiny, brown, ovoid seed to 0.5 mm long and 0.3 mm wide.
Embryo type:
Seed collecting:
Collect mature capsules, those that are turning a pale straw colour and contain brown seeds. Can collect individual capsules or break off the whole plant.
Seed cleaning:
Place the capsules/plant in a tray and leave to dry for two weeks. Then rub the capsules gently by hand to dislodge the seeds. Use a sieve to separate the unwanted material. Be very careful as the seeds are very small. Store the seeds with a desiccant such as dried silica beads or dry rice, in an air tight container in a cool and dry place.
Seed viability:
Good seed viability. One collection of 4000 seeds had 100% viability.
Seed germination:
Seeds are non-dormant, viable seed should germinate readily when sown in winter.
Seeds stored:
LocationNo. of seeds
(weight grams)
of plants
Collection number
Collection location
% ViabilityStorage
BGA8000 (0.17 g)100+28-Oct-2009DJD1631Jun-2010100%-18°C
BGA3800 (0.11 g)100+16-Nov-2010DJD2018
South Eastern
Location: BGA — the seeds are stored at the Adelaide Botanic Gardens, MSB — the seeds are stored at the Millennium Seed Bank, Kew, England.
Number of plants: This is the number of plants from which the seeds were collected.
Collection location: The Herbarium of South Australia's region name.
% Viability: Percentage of filled healthy seeds determined by a cut test or x-ray.
Germination table:
DateResultT0T50Pre-treatment | Germination medium | Incubator: Photoperiod / Thermoperiod
20-Jul-1196%27 d34 d
1% agar with 100 mg/L potassium nitrate;
Incubated under winter conditions
20-Jul-1196%22 d34 d
1% agar;
Incubated under winter conditions
20-Jul-1192%27 d27 d
1% agar with 250 mg/L gibberellic acid;
Incubated under winter conditions
1% agar;
Incubated under winter conditions
1% agar with 100 mg/L potassium nitrate;
Incubated under spring/autumn conditions
1% agar with 250 mg/L gibberellic acid;
Incubated under spring/autumn conditions
1% agar;
Incubated under spring/autumn conditions
1% agar;
Incubated under spring/autumn conditions
Result: Maximum percentage of germination observed.
T0: Number of days before first germinant observed.
T50: Number of days to achieve 50% germination.
Pre-treatment: The initial treatment that the seeds received prior to placement on germination media.
Germination medium: The substrate that seeds were placed on for the duration of the germination experiment.
Incubator conditions:
Photoperiod: The duration of light exposure that the seeds were subject to during a 24 hour period.
Thermoperiod: The constant or diurnal temperatures that seeds were subject to during a 24 hour period.
Winter conditions: 15°C 20 h (3am→11pm); 5°C 4 h (11pm→3am) / 10 h light (8am→6pm); 14 h dark (6pm→8am)
Spring/Autumn conditions: 22°C 12 h (8am→8pm); 10°C 12 h (8pm→8am) / 12 h light (8am→8pm); 12 h dark (8pm→8am)
Summer conditions: 30°C 14 h (6am→8pm); 15°C 10 h (8pm→6am) / 14 h light (6am→8pm); 10 h dark (8pm→6am)