Microbial growth in the rhizosphere

Abstract

Barley plants were grown for up to 16 days in solution culture either under axenic conditions or in the presence of a mixed population of microorganisms. The quantities of soluble carbohydrate released by the roots grown in the absence of microorganisms and the numbers of bacteria which developed in the inoculated solutions were determined. Except for the first 4 days after germination, a greater biomass was produced than could be accounted for by the utilization of the carbohydrates released by the roots grown in the absence of microorganisms; this supports the view that the microorganisms stimulate the loss of soluble organic materials. These results are considered in relation to microbial activity in the soil and in particular to the significance of N 2 fixation by free-living rhizosphere bacteria in the nitrogen economy of plants.