Observations on the Mycorrhizas of Forest Trees. II. The Rhizosphere of Pinus Radiata D. Don

Publisher Website
Google Scholar
Abstract
Two common mycorrhiza types of Pinus radiata were examined by light and electron microscopy. Large numbers of bacteria and fungal species other than those forming the mycorrhiza as well as diatoms were observed in the mycorrhizosphere. Different morphological types of bacteria were characteristic of different mycorrhizal types, and in some cases the bacteria were associated with lysed regions of the mantle. The distribution of the bacteria within the rhizosphere is discussed in relation to the clay minerals and the carbohydrate and polyphenol metabolism of the host. Within the mantle and the Hartig net, the hyphae have a structure typical of the Basidiomycetes, but within the tannin layer the hyphae have an abnormal, distorted appearance. This is correlated with changes in cytology and is construed as evidence of the production of polyphenols toxic to fungi. A possible role of these polyphenols in the control of mycorrhizal associations by selective action on soil fungi entering the rhizosphere is discussed.