Excretion of Thiamin and Biotin by the Roots of Higher Plants

Abstract

THE fact that soil in the immediate vicinity of plant roots supports a much higher microbial population than that existing outside the plant's zone of influence has been recognized for many years. Although it has been suggested that ‘root excretions’ account for this effect, these hypothetical exudates have never been identified, nor has their mode of action been satisfactorily explained. In studying the relation of plants to soil-borne diseases, it was considered desirable, therefore to examine the possibility that excretion of minute amounts of bacterial growth factors by the growing plant might be a fundamental factor in determining the character of the rhizosphere microflora.