Effect of Organic Growth Supplements on Asymbiotic Seed Germination in Orchids: A Review

Orchid seeds are unique in being exceedingly small, dust like in appearance, and more or less fusiform in shape; these lack endosperm and have undifferentiated embryos enclosed within transparent seed coats. Their germination in nature is dependent upon a suitable association with a mycorrhizal fungus. Their fungal requirement can, however, be compensated by supply of sugars and other mineral nutrients in vitro, and several orchid species from diverse habits and habitats have successfully responded to asymbiotic germination, much, however, still remains to be learnt about the nutrient requirements of commercially important and/or endangered orchid species, keeping in view of the large size of the orchid family. This paper attempts to review the available literature on various aspects of asymbiotic seed germination in orchids and the role of organic supplements/additives in promoting seed germination, protocorm development and growth of seedlings.