Physiological Study of the Symbiotic Germination of Orchid Seeds

Abstract

In two previous papers (6, 7) I have presented evidence that germination of orchid seeds is dependent upon an available supply of organic matter. These papers emphasized the nutritional aspects of the problem, and also presented certain views with respect to the possible function of the fungus in the pure culture experiments made by BERNARD (I), BURGEFF (4), and others. All who have studied the germination of orchid seeds agree that there is something very unusual about the seeds of most orchids, for they cannot germinate when merely supplied with water and nutrient salts. According to BERNARD, BURGEFF, IRAMSBOTTOM (ii), and CONSTANTIN and MAGROU (5), normal germination is dependent on infection of the embryo by the appropriate fungus. Symbiosis is believed by these men to be obligative for the normal development of orchids. Symbiosis in a broad sense means the living together of two dissimilar organisms. Under this definition, a very wide range of associations might be considered. The term as applied to the relation between the orchid and the orchid fungus includes the idea that the fungus is in some manner of benefit to the orchid plant, and, according to BERNARD, BURGEFF, and others, germination is normal-