In situ seed development and in vitro regeneration of three difficult-to-propagate Lepidosperma species (Cyperaceae)

Abstract

Field studies of fruit production from Lepidosperma concavum R.Br., L. laterale R.Br. and L. longitudinale Labill. showed that large proportions (21–77%) of fruits were unfilled and that filled and unfilled fruits looked alike. Bagging of inflorescences demonstrated that filled fruits tended to be shed, while empty fruits remained within the inflorescence. Time of collection was critical for obtaining viable seeds, with successful harvesting limited to a short period (weeks) after maturation. The timing of flowering and fruit maturation were fairly consistent between species, populations and years in our study area. In L. concavum fruit production was increased in cultivation compared with wild populations. In all three species, very little or no germination of fruits occurred under nursery conditions. In vitro culture initiation was attempted using intact fruits, nicked fruits and seeds on 1/2MS (Murashige and Skoog) medium with 1 µM zeatin and 0.5 µM gibberellic acid in darkness. Culture of intact fruit resulted in no germination, while nicked fruit showed some germination response. Best results were achieved from seeds with germination occurring as early as 7 to 18 days depending on the species. Germination of L. concavum, L. laterale and L. longitudinale was 86%, 64% and 83% respectively within 5 weeks. Germination response was strongly influenced by seed maturity. Mature seeds germinated significantly faster than immature seeds. On a small proportion of cultured seeds, calli formed and differentiated into numerous plantlets on growth regulator-free medium. Given the promising results observed in this study, in vitro culture appears to be a practical means of mass propagating Lepidosperma species.