Background and Aims: Many Orchidaceous species are threatened globally by development and over-collection from their natural habitats for horticultural purposes. Artificial propagation from seeds is difficult in most terrestrial orchids native to temperate regions. Seed production is another limiting factor in the artificial propagation for these species because of the lessened probability of pollination and the destruction of fruit by insect larvae. Members of the genus Cephalanthera are distributed across Europe, Asia, and North America. C. falcata is a temperate species of East Asia and an endangered species in Japan. As successful propagation from seeds of this species has never been reported, a reproducible method is described here for seed production in situ and propagation using immature seeds in a symbiotic culture in vitro.
Methods: Effects of hand-pollination and bagging treatment of ovaries were examined. Young capsules were collected every 10 d from 50 d after pollination until 120 d after pollination. Immature seeds obtained from these capsules were cultured symbiotically on modified Kano medium and ND medium. Seed viability was examined within TTC (2,3,5-triphenyl tetrazolium chloride) test solution and histological observations were made on viable seeds by paraffin embedding at each collection stage.
Key Results and Conclusions: Hand-pollination followed by bagging treatment of ovaries with aluminum foil was effective for insect control during fruit development, and successfully yielded capsules. Of the capsules, 74.5 % survived to full maturity. The highest frequency (39 8%) of seed germination was obtained with seeds harvested 70 d after pollination. The frequency declined with the progress of seed maturity on the mother plant. Minimal germination was observed with seeds harvested 100 d or later after pollination. Histological observation suggests that the accumulation of such substances as lignin in the inner integument surrounding the embryo during seed maturation plays an important role in the induction of dormancy.