In vitro germination of some Western European orchids

Several germination factors were studied in 23 Western European orchids in order to obtain a germination percentage which approximates the maximum percentage of coloured embryos after an adaptation of the tetrazolium test. The duration of seed pretreatment with Ca(OCl) 2 + Tween‐80 was one of the most important factors controlling the germination of Western European orchids. Best germination occurred in continuous darkness at 23°C on dilute media. The nitrogen source had a species related influence. The best results were obtained with casein hydrolysate, although it could nearly be replaced by one amino acid, L‐glutamine. A cytokinin was required by Cypripedium calceolus and Epipactis hellborine but was not necessary for Lisiera ovata and Dactylorhiza maculata. Experiments with 3 species have shown that the objective, to obtain a germination percentage, which approximated the maximum percentage of coloured embryos, was achieved. This has led to the elaboration of a basic sowing method for European orchids. The application of this method gave good germination responses with 21 of the 23 species tested.