The Rhizosphere–A Hub of Emerging Importance for Plant Biotic Interactions

Abstract

The rhizosphere is a microhabitat around plant roots that is actively created and regulated by plants, while having a major impact on plant life itself. Plants constantly enrich the rhizosphere with organic matter from their rhizodepositions and root exudates, shaping the chemical and microbiological composition of the space surrounding their roots. In this chapter, we discuss the interactions between plants and other organisms through the processes in the rhizosphere. Plant-associated microorganisms, such as plant growth-promoting bacteria and mycorrhizal fungi, play important roles in enhancing the survival of plants, through increasing the availability of nutrients from the soil to plants, degrading and immobilizing toxic compounds, alleviating the effects of abiotic stress, acting as biocontrol agents, protecting the plants from pathogens, and bolstering the efficiency of plant responses to biotic and abiotic stress. Moreover, plants use the rhizosphere as a battlefield for mutual competition by releasing allelochemicals that are detrimental to other plant species, and to harmful soil nematodes and insects. Similarly to land plants, aquatic plants also create a rhizosphere around their roots, with important implications for rice cultivation, methane emissions from wetlands, denitrification of aquatic habitats, and wastewater treatment through constructed wetlands. We emphasize how the existing and potential rhizosphere engineering approaches take advantage of the plant-associated microorganisms and allelopathic interactions between plants to improve the health and yield of agricultural crops, and help preserve the natural environment.