The limited numbers of nodules produced on legumes by different strains of Rhizobium

Abstract

Pot experiments were made with red clover and with soy beans to determine how far the number of nodules developed was a specific character of the strain of Rhizobium supplied.The number of nodules per gram of root was found to reach a limit specific to each strain. This limiting equilibrium was attained regardless of the size of the root system or the age of plant at which the culture was first supplied, provided enough time were allowed for the limit to be reached.When two different strains were applied to the root surroundings in succession, the final number of nodules was determined by the limit specific to the strain in contact with the roots while these were making most of their growth. In clover this was the second and in soy beans the first applied strain.