Methyl jasmonate induces conservative trait shifts that improve drought resilience in clonal grass

Recurrent drought events are becoming increasingly frequent under climate change, yet how perennial clonal grasses adjust their functional traits and recovery trajectories across repeated drought-recovery cycles remain poorly understood. Here, we examined whether exogenous application of methyl jasmonate (MeJA) modifies physiological performance, biomass allocation, and recovery dynamics of the clonal grass Festuca rubra under recurrent drought. Plants were exposed to three consecutive drought-recovery cycles in a controlled growth-chamber experiment with factorial drought and MeJA treatments. We quantified physiological traits (chlorophyll concentration, maximum quantum efficiency of PSII), structural traits (specific leaf area, leaf dry matter content), and performance-related traits (ramet number and biomass allocation). Recurrent drought progressively reduced photosynthetic performance and ramet production, with recovery becoming increasingly incomplete across cycles. In contrast, MeJA treatment mitigated drought-induced declines in chlorophyll concentration and PSII efficiency and stabilized recovery responses. MeJA also altered biomass allocation patterns, increasing aboveground biomass and reducing root-to-shoot ratios under drought, in contrast to drought-only plants, which showed enhanced belowground investment. Post-hoc analyses revealed that MeJA + drought plants differed significantly from drought-only plants for aboveground biomass and several functional traits. Overall, our results demonstrate that MeJA modulates drought responses and recovery trajectories in F. rubra, promoting conservative trait expression and improved performance under recurrent drought. These findings highlight the potential role.