Studies on microbial population in the rhizosphere of higher plants with special reference to the method of study

Introduction

Many previous investigations, beginning with the observations of Hiltner¹⁹, have established the fact that soil in the rhizosphere contains a higher quantity of microorganisms than soil which is not within the influence of the plant root. It has been shown also that the balance between certain physiological groups^4,21,43,45, as well as that between morphological types of bacteria or fungi^30,50 is changed in the rhizosphere. In addition, Canadian investigators^23,34,62) have reported a change in the balance of certain nutritional groups of soil bacteria in the rhizosphere. Two excellent reviews^6,22) covering these papers have recently appeared. Since then a number of papers^{2,7,9,11,13,15-18,25,26,33,36,38-40,48,54,57-60,63)} concerning various aspects of the microbial population of the rhizosphere have been published.