Microbial damper: Rhizosphere microbiome mitigates stress-induced plant growth-defense conflicts

Plants face constant environmental stresses that induce conflicts between growth and defense. The rhizosphere microbiome helps resolve this conflict by enhancing nutrient-uptake efficiency and activating plant immunity simultaneously. In this review, we first outline the mechanisms and limitations of plant-intrinsic growth-defense trade-offs; we then describe the integrated support that rhizosphere microbial communities provide for plant nutrition and defense. Finally, we propose the "microbial-damper" framework and further elucidate the interactions and feedback mechanisms that constitute this system. The microbial damper is a conceptual framework describing the capacity of the rhizosphere microbiome to stabilize a plant's internal growth-defense resource allocation, which is otherwise perturbed by stresses such as nutrient imbalance and other environmental stresses. This framework highlights how the rhizosphere microbiome can reduce stress-induced plant growth-defense resource-allocation conflicts, thereby providing actionable strategies for designing sustainable agricultural systems.