THE NODULAR MYCORRHIZAE OF PODOCARPUS ROSPIGLIOSII

Abstract

Podocarpus is a genus of southern hemisphere and tropical conifers which are often important timber trees in their respective ranges. Nodular short-roots were early noted as being similar in gross aspect to legume nodules, and it was inferred that they are Rhizobium-bearing symbiotic structures which fix atmospheric nitrogen. In histological section the nodular short-roots of the Venezuelan species Podocarpus rospigliosii were shown to contain endotrophic mycorrhizae. In a Koch's Postulates test, a fungus isolated from Podocarpus induced the formation of nodular structures on aseptic seedlings. A Nitrogen¹⁶ test was negative for fixation of atmospheric N₂. Recent work in New Zealand has shown comparable histology in other species of the genus. The mycorrhizae may be important in forestry practice, though not as a source of nitrogen.