Incubation temperature critical to successful stimulation of in vitro zygotic embryo growth in four Australian native Cyperaceae species

Abstract

Many species of Western Australian Cyperaceae (sedges) are vital components of the indigenous flora but commonly display low seed set, poor seed quality and intractable seed dormancy. We report the effects of incubation temperature and in vitro growth media on whole seed germination compared with extracted zygotic embryo growth in Tetraria capillaris, T. octandra, Lepidosperma drummondii and L. tenue. No germination was observed from intact whole seeds of all test species regardless of the treatment evaluated. In contrast, excised zygotic embryos of all study species exhibited significant increases in growth when cultured at 15°C compared to embryos incubated at 25°C; however, optimal media for embryo growth were genera specific. Extracted embryos of T. capillaris and T. octandra exhibited maximum percentage growth (30 and 40%, respectively) at 15°C on MS medium with no plant growth regulators required. In the case of L. drummondii and L. tenue 1 lM thidiazuron was a necessary addition to the MS medium resulting in 40 and 77% growth of embryos (at 15°C), respectively. Incubation of extracted embryos at 25°C (regardless of medium treatment) resulted in \10% embryo growth for T. octandra and L. tenue, while the remaining two species (L. drummondii, T. capillaris) showed no embryo growth at 25°C on any medium treatment.

GA3 induces expression of E2F-like genes and CDKA during in vitro germination of zygotic embryos of Cocos nucifera (L.)

“…Germination begins with water uptake by seeds and terminates with the initial elongation of the embryonic axis (Bewley 1997;Panaia et al 2009). The completion of germination is visible by the emergence of the radicle.…”

Primary and repetitive secondary somatic embryogenesis of Lepidosperma drummondii (Cyperaceae) and Baloskion tetraphyllum (Restionaceae) for land restoration and horticulture

“…In addition, although there are many attractive, droughttolerant species, they are not available in horticulture because of propagation difficulties. Germination of seed is highly dependent on the collection of viable seed (Panaia et al 2009) and typically in the field that requires several seasons of wetting and drying before germination is possible (Meney and Dixon 1995a). Seeds also tend to have low seed viability and complex dormancy mechanisms (Rossetto et al 1992).…”

Biotechnology for saving rare and threatened flora in a biodiversity hotspot

“…In vitro culture is possible by extraction of seed embryos and subsequent growth of seedlings in aseptic culture from which shoot culture lines are (very slowly in most cases) derived (Willyams 2005). Somatic embryogenesis procedures have been developed at Kings Park and Botanic Garden (Panaia et al 2009) and primary and secondary SE protocols that enable greatly increased plant production over conventional micropropagation approaches (Panaia et al 2011).…”

“…It is evident that 2,4-D is highly effective for stimulation of SE in these species, especially from excised zygotic embryos, whereas hormone-free BM or BM+TDZ is most effective for conversion of somatic embryos to plants, depending on the species ( Panaia et al 2004a conversion rates (for somatic embryos to plants) are also variable and appear to be related to provenance, seed quality and incubation temperature of zygotic embryos (Panaia et al 2009). Further research is required to evaluate these differences and optimise in vitro protocols accordingly.…”