Orchid Agar

Principle And Interpretation

Orchids exhibit flowers of exquisite beauty and variety of patterns and belong to one of the largest family, the Orchidaceae. Orchids are the first floricultural crop successfully mass propagated through tissue culture technique. Orchids may be propagated either sexually or asexually. Vegetative propagation is common practice for many of the commercial orchids. Germination of seeds can be symbiotic or asymbiotic. Symbiotic seed germination is done under natural conditions, the orchid seeds germinate after being infected by fungus and mycorrhiza. Orchid seeds have only minute reserves of food and the symbiotic organisms provide the required nutrients. Lewis Knudson in 1916 formulated a medium in which orchid seed were germinated successfully without fungal infection (4). Asymbiotic germination is done by aseptic inoculation of seeds on medium.

Orchid Agar was developed by Knudson (1, 2) for the germination of orchid seeds. In his research he found the importance of the presence of minor elements like copper, manganese and zinc for the growth of orchid seeds. The medium also consists of iron, which is three times more the concentration of manganese. Somers and Shive (3) reported that double or triple the amount of iron, than manganese, in the medium is optimum for orchid seed germination. Ammonium and magnesium sulphate in the medium helps in germination of the orchid seeds. Saccharose (sucrose) is the carbohydrate source in the medium while monopotassium phosphate helps in maintaining the acidic pH of the medium by its buffering action.