Book Description
The rhizosphere is an ecological hotspot. Plant roots, bacteria, archaea, fungi, nematodes, and other macroscopic organisms interact here with each other. Plants represent the main influencing force as they produce a mixture of chemical molecules and extrude them in the form of root exudates. Those exudates determine not only the nutrient availability of the plant but also influence the outcome of the interactions in the vicinity of the roots. In response to the plant-derived signals, a subset of the bulk soil microbes can proliferate in the proximity of the root and some of them can eventually overcome the plant defense system to colonize the plants. The root-associated microbiota is assumed to be crucial for plant health, and belowground plant-microbe and microbe-microbe interactions can result in altered growth and nutritional quality of the aboveground plant parts. Such interactions affect community composition and productivity in natural ecosystems or crop yield in agricultural fields. Root associations with plant growth-promoting rhizobacteria (PGPR) producing phytohormones that alter root architecture, or produce antibiotics to suppress antagonistic pathogens, affecting nutrient availability and competition between plants are just a few among many examples of such belowground interactions in the rhizosphere. Moreover, the role of rhizosphere microorganisms in stimulating the plant immune system leading to Induced Systemic Resistance (ISR) has also been a focus of an active investigation. However, the molecular mechanisms are still largely unknown. On one hand, it has been proposed that plants actively recruit beneficial microorganisms under certain pathological conditions or influence the soil microbial communities and create a so-called “soil memory”, which is conveyed to future plant generations. On the other, the presence and interactions between microorganisms in the soil have a substantial impact on plant health.
