STUDIES ON THE RHIZOSPHERE MICROFLORA OF SORGHUM IN RELATION TO HYDROCYANIC ACID CONTENT OF ROOTS

Abstract

Analysis of hydrocyanic acid contents of the roots of six sorghum strains revealed the concentration to be high in the seedling, and that it reduced with age. Hydrocyanic acid was also present in the roots of ratoon plants but in lower concentrations than in seed plants of the same strain. Rhizosphere effects on the microbial populations at different stages of plant growth were observed and the effect varied with the strain and age of plant. The rhizosphere:soil (R:S) ratio for bacteria ranged from 1 to 25, for fungi 1 to 17, and for actinomycetes 1 to 6. The rhizosphere effect continued in the ratoon plants in all strains, though to a lesser extent than in seed plants. Statistical analysis of the data for correlation between hydrocyanic acid concentration in roots and the population of rhizosphere microorganisms did not indicate any uniform effect in all the sorghum strains.