Factors affecting seed germination and seedling growth of terrestrial orchids cultured in vitro

The effect of two sterilization substances (calcium hypochlorite and sodium hypochlorite) on the germination rate, and the effect of nitrogen and growth regulators on seedling growth and development, was studied in three critically endangered species of terrestrial orchids (Dactylorhiza incarnata subsp. serotina, Dactylorhiza maculata subsp, maculata, Liparis loeselii). Surface sterilization of mature seeds using 7.2% calcium hypochlorite (until decolorization from brown to ivory) stimulated the germination rate. Addition of peptone at 1 g l-1 concentration or auxin 3-indoleacetic acid (IAA; 1.43 µM) with cytokinin zeatin (0.72 µM) and 1-naphthylacetic acid (NAA; 1.34 µM) to the culture medium significantly increased the growth parameters of seedlings after 12 months.