ABSTRACT
Considering the phenomena occurring at the soil-root boundary, it is necessary to define some terms, such as "bulk soil", "soil-root interface", "rhizoplane", and "rhizosphere". The term "soil-root interface" is defined as a boundary between the outermost root tissues and the particles of soil which are closest to them. "Rhizosphere" is a zone of microbial activity within and around the roots. It is provided with substances rich in energy and minerals released by the roots. As the roots extract water in wet soil, the rate of their water uptake decreases with the decrease of soil water content. The decrease is explained by the increase of hydraulic resistance in the soil-plant system. R. C. Foster et al., by combining electron microscopy with the use of undisturbed soil and root samples either as ultrathin sections for transmission electron microscopy or as frozen, dehydrated specimens for scanning electron microscopy, developed a new visual concept of the ecology of microorganisms at the root-soil interface.
