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 re establish following mining. Limiting factors for germination success were explored and identified. Lomandra sonderii (F.Muell.) 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. drummondii (F. Muell. ex Benth.) Ewart from 40% to 80%. Soaking L. sonderi seeds in gibberellic acid (GA₃, 50 mg L^-1) further improved germination (28%). Ants (Camponotus sp. and Iridomyrmex 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.