Nutritional requirements for in vitro seed germination of 12 terrestrial, lithophytic and epiphytic orchids

Although numerous media have been developed to evaluate both orchid seed germination and further seedling development after storage, few studies have attempted to relate nutritional requirements to life history traits. For a range of terrestrial, lithophytic and epiphytic orchid species, comparisons were made of germination on Knudson C, with and without activated charcoal or banana powder, Norstog and Phytamax™ media to represent variations in available nitrogen. Germination varied, with maximum values ranging from just 9% for Prosthechea cochleata, Platanthera sp. and Spathoglottis paulinae to 95% for Phragmapedium longifolium. Along with Paphiopedilum delenatii, Paphiopedilum philippinense and the epiphyte Guarianthe bowringiana, P. longifolium germinated well on most media. Germination was significantly higher on Norstog than the other media for four of the six epiphytes tested. Germination was maximum on Knudson C medium with activated charcoal for four of the six terrestrial/lithophyte species. The results indicate a greater preference for nitrogen from amino acids rather than ammonium or nitrate salts in seeds of epiphytes compared with some terrestrial orchid species.