Seeds of South Australia
Gahnia halmaturina (Cyperaceae)
Kangaroo Island Saw-sedge
List of species for Gahnia
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Seed collecting:
April to June, August, December to January
Herbarium region:
Kangaroo Island
NRM region:
Kangaroo Island
IBRA region
Kangaroo Island (KAN01)Kanmantoo
 Vulnerable   (IUCN: VU D2)   [in Flinders Chase only, on 1 creekline; only recently described]
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 Gahnia]
Name derivation:
Gahnia named after Dr. Henricus Gahn, 19th century Swedish botanist and student of Linnaeus. Halmaturina from halmaturus, a generic name once applied to kangaroos, and derived from the Greek 'halme' meaning a leap or bound, and commonly used as an epithet for species from Kangaroo Island.
Distribution:
Endemic to South Australia and found only on Kangaroo Island, restricted to the vicinity of West Bay in Flinders Chase National Park, growing on rocky areas along the banks and floodplains of freshwater creeks.
Status:
Native. Rare in South Australia.
Plant description:
Tufted perennial with short, compact rhizomes with culms to 65 cm high and 1.7 mm diameter, often paler than leaves. Leaves flexuose, erect to spreading; margins tightly inrolled when dried, sometimes appearing terete with a groove on one side; dull green (pale to cream at base), not glaucous, to 70 cm long and 1.8 mm wide (when dried and margins inrolled); sheath pinkish brown to dark chocolate-brown. Inflorescence pale to dark brown, linear in outline to 16 cm long and 20 mm wide with several lateral branches. Flowering between April and May.
Fruit type:
Brown spike shorter than the leaves.
Seed type:
Dark brown three sided ovoid seed to 2.5 mm long and 1.5 mm wide, with a slight pitted surface.
Embryo type:
Capitate.
Seed collecting:

Collect heads that are dying off with dark brown seeds hanging from the flowering spike.

In 2016 the first viable seed collection for this rare saw-sedge was achieved on Kangaroo island with the support of the Australian Seed Bank Partnership.

Seed cleaning:
Place the heads in a tray and leave to dry for one to two weeks. Then rub the heads with a rubber bung to dislodge the seeds. Use a sieve to separate any unwanted material. 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.
Germination table:
DateResultT0T50Pre-treatment | Germination medium | Incubator: Photoperiod / Thermoperiod
Jun-170%NANA 30% hydrogen peroxide for 20 min, water rinse, 500 mg/L gibberellic acid for 44 h;
1% agar;
Incubated under spring/autumn conditions
Jun-170%NANA dry heat 100°C oven for 10 min, 30% hydrogen peroxide for 20 min, water rinse, 500 mg/L gibberellic acid for 44 h;
1% agar;
Incubated under winter 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)