Soil microorganisms and the formation of proteoid roots

Abstract

Proteoid roots are not formed in sterile soil under conditions which would otherwise allow their production. This is attributed to the absence of soil microorganisms rather than to an alteration of chemical components by autoclaving. Water extracts from proteoid roots or their associated soil did not enhance the formation of proteoid roots. High microbial numbers in the surface soil horizons are considered largely responsible for the abundance of proteoid roots in these high organic matter regions. Results of experiments indicate that the formation of proteoid roots is stimulated by soil microorganisms which themselves do not invade the parent root, though the relevant organisms have yet to be identified.