Increased dependencies among plant performance traits, root exudates and the rhizosphere microbiome under drought

Background and aims Plants interact with soil microbes via root exudates. In turn, soil microbes can improve the plants’ access to water and nutrients. The beneficial effects of root exudates and microbes may become particularly important when plants are at risk of losing access to water and nutrients, helping to sustain resource acquisition under stressful conditions. Consequently, tighter links among plant performance, root exudate compounds and microbes are expected under drought. Method We tested this expectation in a drought experiment with Arabidopsis lyrata. Root exudates were quantified using gas chromatography, and the rhizosphere bacteria and fungi were identified by sequencing. Together with plant traits, their link was investigated by network analysis. Key result We found that drought stress changed the root exudate composition and the bacterial, but not the fungal community in the rhizosphere. Network analysis revealed higher connectedness under drought, indicating an increase in associations among plant performance traits (such as flowering or biomass), exudate compounds and the rhizosphere microbiota. Positive correlations between performance traits and known plant growth-promoting bacteria suggest that the stressed plants benefit from enhanced interdependencies with the rhizosphere microbiota. Conclusion The study reveals interconnected dynamic responses of plants, root exudates and soil microorganisms to drought, highlighting the importance of dependencies for plant survival and growth under challenging conditions.