In vitro germination of three Cypripedium species in relation to time of seed collection, media, and cold treatment

Abstract

To maximize the in vitro seed germination of three Cypripedium species, C. candidum Muhl. ex Willd., C. reginae Walt., and C. calceolus var. parviflorum Salisb. Fern., the optimum time of seed collection and the suitability of various media were studied. A cold treatment was investigated for C. candidum. Seed pods were collected at regular intervals after pollination, ranging from green pods at 5 weeks to dry undehisced pods at 12 weeks. Seed was inoculated onto three media, Harvais, Van Waes and Debergh, and a modified Norstog and germination was assessed at 4-week intervals for 20 weeks. Cypripedium reginae germinated better than the other two species. Except for C. candidum in 1989 when germination peaked for seed collected at 6 weeks after pollination, seed collected at 8 weeks after pollination had the highest germination. After 8 weeks, germination decreased sharply in all species, dropping below 1% for C. candidum. There were differences among media but the effects on germination were not consistent and depended on the year, the date of collection, and the species. Subsequent development of protocorms was superior in all cases on the modified Norstog medium. The effect of cold treatment on germination of C. candidum was variable and therefore its importance is questionable. Key words: in vitro, germination, Cypripedium, lady's slippers, seed maturity.