Underground Signals: The Ecological Power of Root Volatiles.

Root volatiles mediate diverse belowground interactions among plants, microbes, and invertebrates, but biological and environmental conditions strongly influence their production, movement, perception, and ecological effects. This review synthesizes current knowledge through an integrative conceptual framework linking five dimensions: (1) chemical diversity and biosynthesis; (2) regulation by biotic and abiotic factors; (3) plant internal signaling and resource allocation; (4) ecological adaptation and reciprocal evolutionary interactions with soil organisms; and (5) implications for agricultural management. Key roles include defense against herbivores and pathogens, recruitment of beneficial microbes and natural enemies, plant recognition, allelopathy, systemic signaling between roots and shoots, and coordination across multitrophic networks. The synthesis examines how volatile identity and concentration, soil properties, microbial transformation, and plant genotype influence signal transmission and ecological outcomes. Comparisons across taxa, compounds, and experimental systems clarify which mechanisms are broadly supported and which remain context-dependent. Priorities include resolving molecular pathways, tracing volatile transport and persistence in soil, distinguishing volatile effects from those of nonvolatile exudates, and validating functions under field conditions. A deeper mechanistic and ecological understanding of root volatiles is therefore essential for developing resilient crop protection strategies, reducing dependence on agrochemical inputs, advancing sustainable agroecology, and sustaining long-term soil health.