Germination of Lomandra sonderi (Dasypogonaceae) Promoted by Pericarp Removal and Chemical-Stimulation of the Embryo

Abstract

Lomandra Labill. is a common genus in the understorey of the jarrah (Eucalyptus marginata Sm.) forest of Western Australia. Species in this genus are difficult to propagate by seed and do not readily reestablish following mining. Limiting factors for germination success were explored and identified. Lomandra sonderii (F.Muel1.) Ewart set very few seed (seeds per flower = 0.122). Tetrazolium tests indicated that seed viability was relatively high (50%). Germination was inhibited (0%) by the inner pericarp tissues which surround the seed and are part of the diaspore. Manual removal of the inner pericarp or leaching overcame this inhibition with a fifth of seeds subsequently germinating. Similar treatments improved germination of L. drurnmondii (F. Muell. ex Benth.) Ewart from 40% to 80%. Soaking L. sonderi seeds in gibberellic acid (GA3, 50 mg L -~) further improved germination (28%). Ants (Camponotus sp, and Zridomymtex sp.) collected and dispersed L. sonderi seed and are likely to improve germination in the forest by removing and consuming the inner pericarp. Only half of the viable excised embryos of L. sonderi grew in vitro, indicating the presence of embryo dormancy.Embryo dormancy was overcome by GA3 (0.5 mM) and zeatin (0.5 mM) in the liquid culture medium.In vitro culture may be a practical means of propagating Lomandra if seed is scarce.

Relationships between seed germination requirements and ecophysiological characteristics aid the recovery of threatened native plant species in Western Australia

“…Fruit or seed coats may restrict oxygen and water exchange, and may create a physical barrier to radicle emergence (Beardsell et al 1993). Inhibitors may also be present in the seed coat, pericarp, endosperm or embryo itself and prevent germination of seed (Richmond & Chinnock 1994; Richmond & Ghisalberti 1994; Plummer et al 1995). Although some fleshy‐fruited species require leaching of the seed to wash away inhibitors and stimulate germination (Bell et al 1993), the detachment of the seed coat from the endosperm and embryo may also remove inhibitors allowing germination to proceed.…”

“…In large‐seeded species, however, light exposure may reduce maximum percentage germination under higher temperatures, but at 15°C this temperature/light interaction has minimal effect on germination percentages (Bell et al 1995). Light effects may be overcome under laboratory conditions with the application of the growth hormone gibberellic acid (Bell et al 1993, 1995; Plummer et al 1995).…”

“…Dormancy takes many forms and includes both external (coat‐imposed) and internal (embryo) controls on germination (Bewley & Black 1994). No single set of conditions will give optimal germination in all species, and a wide range of environmental cues may be required for the breaking of dormancy and the initiation of germination (Langkamp 1987; Bell et al 1993; Richmond & Chinnock 1994; Dixon et al 1995; Plummer & Bell 1995; Plummer et al 1995; Schatral 1996; Schatral et al 1997; Bell 1999).…”

Invasive ants in Australia: documented and potential ecological consequences

“…Most myrmecochores occur in the temperate sclerophyll forest and heath/shrubland in the south (Berg 1975) where they comprise 30-50% of the species in some communities (Willson et al 1990). Benefits to the seeds can include increased dispersal distance (Andersen 1988;Whitney 2002), scarification (Plummer et al 1995) or protection from fire (Auld 1986). The fate of seeds is largely dependent on the attributes of the dispersing ants (Hughes & Westoby 1992).…”

Restoring a Jarrah Forest Understorey Vegetation after Bauxite Mining in Western Australia

“…Tissue cultures of dryland rush and sedge species are initiated from extracted embryos using modifications of Meney’s methods (Meney 1993; Meney & Dixon 1995). For Lomandra species of the Dasypogonaceae, seed numbers are sufficient for tissue culture initiation by modification of Crawford’s in vitro method (Plummer et al 1995). For many species, early work found that transfer from the laboratory to the greenhouses had poor plant survival, until ventilation of the culture vessels was introduced by modification of Rosetto’s method (Rossetto et al 1992).…”