The effect of certain adsorbents on the nodulation of clover plants

Abstract

The addition of charcoal to the rooting medium of clover plants inoculated with effective and ineffective strains of Rhizobium leads to a stimulation in nodule production. The time interval between inoculation and the first appearance of the nodules is reduced in the presence of charcoal. Several explanations of this phenomenon have been investigated and it is concluded that the stimulation is due to the adsorption by the charcoal of inhibitory compounds secreted by the clover roots. These compounds have been eluted from the charcoal and have been shown to affect nodule production. As a result of these experiments it is suggested that, depending on the concentration of the secretions in the eluates, either a stimulation or inhibition of nodule production may occur.Other adsorbents have also been added to the clover plants, but no consistent stimulation of nodule production has been observed. © 1955 Oxford University Press.