Effects of NaOC1 treatment on in vitro germination of seeds of rare endemic plant, Oreorchis coreana Finet

Oreorchis coreana Finet is threatened globally by over-collection from its natural habitats for horticultural purposes. Its rarity in nature makes this plant one of the most endangered species in Korea. In this study, we investigated the effects of sodium hypochlorite (NaOC1) on orchid seed viability and seed germination. An in vitro bioassay swelling test using immature seeds was compared with a standard chemical procedure using tripheny1 tetrazolium chloride (TTC) to test seed viability. In general, the bioassay was more appropriate for estimating embryo viability after a prolonged pre-treatment (more than 1 h) in 1% NaOC1, a surface sterilant often used to enhance germination of seeds of terrestrial paints. Therefore, an efficient method for investigating in vtiro swelling of immature seeds is urgently needed. We established a method for determining the viability and swelling of O. coreana seeds via in vitro examination of immature seeds. Treatment of immature seeds with 1%NaOC1 for 10 min greatly enhanced the extent of swelling of immature zygote embryos when compared to untreated seeds. These data obtained here appear to be comparable to viability and swelling that occurs in O. coreana seeds via asymbiotic germination.