Plant–Microbiome Interactions for Environmental Resilience: Rhizosphere Ecology, Climate Adaptation and Ecosystem Sustainability

The rhizosphere, the narrow and dynamic zone of soil shaped by living roots, hosts some of the most consequential biological interactions on Earth. Root-associated microorganisms and symbionts influence plant nutrition, immunity, stress tolerance, soil carbon formation and ecosystem stability, and they are increasingly proposed as tools for reducing fertiliser and pesticide dependence and for adapting agriculture to climate change. Enthusiasm for microbiome-based solutions has nevertheless outpaced the evidence in several areas, and the literature combines rigorous mechanistic work with correlative surveys, optimistic extrapolation and inconsistent field outcomes. This critical narrative review evaluates what is known, what is contested and what remains speculative across the continuum from fundamental rhizosphere processes to applied and climate-oriented management. Peer-reviewed literature was identified through structured searching of multidisciplinary and biomedical bibliographic sources, supplemented by citation tracking, with emphasis on evidence published from 2005 onwards and inclusion of earlier foundational work. The synthesis examines five linked themes: the spatial and chemical definition of the rhizosphere; the assembly of root-associated microbiomes under soil, host and microbial control; the mechanisms, costs and context dependency of arbuscular mycorrhizal, rhizobial and associative symbioses; rhizosphere contributions to plant health, nutrient supply and soil carbon; and the responses of root–microbe systems to drought, warming and elevated carbon dioxide. Evidence is strongest for soil as the principal source of root microbiota, for host filtering of community composition, for the molecular basis of the major mutualisms and for context-dependent benefits of symbiosis. Evidence is weaker and frequently overstated for the general efficacy of commercial inoculants, the functional importance of common mycorrhizal networks in forests, the transferability of laboratory-defined synthetic communities to farms and the reliability of microbe-mediated stress acclimation. The review identifies predictive understanding of context dependency, long-term field experimentation, standardised functional measurements and integration of rhizosphere processes into crop breeding and carbon models as the principal priorities. Rhizosphere biology offers genuine opportunities for sustainable and climate-resilient systems, but realising them requires management grounded in ecological mechanism rather than product-driven optimism.