Germination responses of four native terrestrial orchids from south-west Western Australia to temperature and light treatments

The effect of smoke derivatives and carbon utilisation on symbiotic germination of the endangered Pterostylis despectans

“…Germination.-Pterostylis despectans seed in this study had very low germination success compared to other orchid genera. For example, other Australian orchids showed high germination that reached up to 100%, including more common Pterostylis species (Batty et al 2006, Huynh et al 2004, Nikabadi et al 2014. This low germinability may indicate requirements for additional stimulants and be a contributing factor to its rarity and consequent endangered status of P. despectans.…”

“…Pterostylis despectans seed were collected 8 years prior to the experiment and may be too long for the optimum viability to be maintained. Studies on other plants have shown that time affects seed viability (Merritt et al 2003) with high orchid seed germination achieved when seed material was obtained within a year before germination (Batty et al 2001, Nikabadi et al 2014. Seed viability of Australian plants was affected by relative humidity and temperature during storage (Merritt et al 2003).…”

“…Symbiotic germination.-OMA (2.5 g L -1 finely ground rolled oats, 0.1 g L -1 yeast extract, 8 g L -1 agar, pH adjusted to 5.3-6.0) (Nikabadi et al 2014) was prepared in sterile petri dishes with three concentrations (0, 0.1 and 1 mL L -1 ) of smoke water (Regen 2000® Smokemaster, Australia) in the absence or presence (10 g L -1 ) of sucrose (Sigma Aldrich) before sterilization. One cm 2 squares of sterile Miracloth (Calbiochem, USA) were placed onto set OMA.…”

“…In this symbiotic relationship, fungi supply the orchid with nutrients including nitrogen (Girlanda et al 2011) and phosphorus (Cameron et al 2007) while the orchid supply carbon to the fungus (Cameron, Leake & Read 2006, Látalová & Baláž 2010. Carbon utilisation by mycorrhizal fungi vary with some clades from the same Rhizoctonia species inhibited by sucrose resulting in suboptimal seed germination (Huynh et al 2004, Nikabadi et al 2014, Wright et al 2009.…”

“…Some in vitro studies have successfully germinated orchid seeds asymbiotically (without fungi) using specific stimulants such as growth hormones to promote germination (Huynh et al 2004, Nikabadi et al 2014). Despite the germination success of asymbiotic plants, symbiotically germinated orchids established in soil better in the long term than those without fungi (Batty et al 2001, Rasmussen 1995 which suggests fungal superiority and importance to orchid conservation particularly for plants that reside in depleted nutrient habitats.…”