Nitrogen Fixation in Ericaceae

M. Cheveley Rayner
1922 Botanical Gazette  
Introductory Since the middle of the nineteenth century it has been known that plants belonging to the Ericaceae form mycorhiza of a characteristic kind. Further knowledge of the relations between plant and endophyte in this group has only recently been forthcoming. In I9I5 RAYNER, showed that the relationship in Calluna vulgaris is of a remarkable character, involving obligate symbiosis between the two organisms and a much more extensive distribution of the fungus throughout the green plant
more » ... the green plant than had been suspected. As in Orchidaceae, root formation by seedlings is dependent upon early infection by the endophyte, failing which, development ceases and the plant perishes in the seedling stage. Unlike the condition in Orchidaceae, infection at the appropriate moment is provided for by the presence of mycelium on the seed coat, a condition ensured by the distribution of the endophyte throughout the vegetative tissues and eventually within the ovary chamber. These facts have been demonstrated with certainty in Calluna, and the evidence points to a similar condition throughout the family. Thus ovarial infection has been reported for many species in all the suborders of Ericaceae, and the inability of seedlings to complete their development without infection has already been proved for a number of these. In such remarkable associations between flowering plants and fungi as are found in the orchids and in Ericaceae, it is of great interest to learn the exact nutritive relations between the symbionts. In orchids there is ocular evidence of digestion of mycelium by the cells of the root, and it is clear that by this means the plant can draw indirectly upon organic compounds of carbon and nitrogen in the soil. In the chlorophyllous orchids the endophyte can utilize
doi:10.1086/332977 fatcat:ooaivs3ujvhaxmoarkgre4qyum