Non-Symbiotic Germination of Orchids

Abstract

The propagation of orchids from seeds is a problem which has attracted the attention of many investigators. That orchids could be grown in the greenhouse from seeds was not considered extraordinary; orchid growers in Europe and in this country were successful in this line of work. Naturally scientists took up the study of the conditions of germination. In the roots of the orchid plants symbiotic fungi had been detected, and the first investigators of this problem, Bernard ('09) and Burgeff ('09) undertook experiments with the symbiotic fungus. Since they had no success without the fungus, the presence of the fungus was considered to be a conditio sine qua non. In 1922 Knudson published the results of his successful experiments on the nonsymbiotic germination of orchids, and a number of other investigators have worked on the same subject, in the majority of cases successfully. It is a well-known fact that a greater knowledge of the conditions for growing orchids is of particular interest not only to those working on the subject for commercial purposes, but also to those engaged in scientific investigations. From Knudson's ('25, '27) experiments we learn that the metabolic processes of the fungus bring about chemical changes in the medium which make it more assimilable. Chemical compounds indigestible for the seedlings are broken up or transformed into ones which can be easily used as food by the embryo. Another favorable influence of the fungus is the gradual acidification of the medium, according to Burgeff, Knudson, and Clement. However, experiments showed that it need not be necessarily the special orchid fungus. Other fungi may produce the same effect. Every one dealing with the germination of orchid seeds will have made the same discovery. From the experiments of Knudson and other investigators, such as Constantin and Magrou ('22), Ramsbottom ('22), and Clement ('24, '26, '29), our present knowledge of the requirements for successful germination of