The Chinese medicinal plants rhizosphere: Metabolites, microorganisms, and interaction

Rhizosphere is a hot spot for plant-microbe-soil information and material exchanges, and is inseparable from plant growth and development. The purpose of this paper is to review the progress of research concerning the rhizospheric microorganisms of medicinal plants, the types of root secretions and their interactions. The majority of medicinal plants have strong obstacles to continuous cropping, so we reviewed studies on the effects of root exudates and microbial communities in rhizosphere on continuous cropping obstacles. In the context of continuous cropping, medicinal plants secrete secondary metabolites in order to resist abiotic stress, which accumulate in the soil and produce autotoxic effects. These autotoxins have a concentration effect on medicinal plants; the higher the concentration, the stronger the inhibitory effect on growth. They are also highly species-specific, with autotoxins differing from one medicinal plant to another. As a result of these autotoxins, the structure of the rhizospheric soil microbial community is destabilized, resulting in an increase in the number of harmful microorganisms and a decrease in the number of beneficial microorganisms. The present study provides an insight into the interactions between medicinal plants and rhizospheric microorganisms.