Schematic representation of molecular pathways within canonical PTI responses and their relationships. MAMP perception by PRRs triggers ROS burst and Ca²⁺ influx, which potentiate each other, by phosphorylating CNGC2/4 and RbohD/F, respectively, in a BIK1-dependent and MAPK-independent manner. The MAPK cascade transduces signals to transcription factors that facilitate metabolite-dependent immune responses. While these small molecules, namely, Ca²⁺, ROS, secondary metabolites, and defense-related phytohormones, are crucial for immunity against pathogens, it remains unclear whether and how they cause the growth inhibition after chronic PTI activation. It is also unclear whether transcriptional reprogramming at early stages (within days) plays a role in macroscopic plant growth phenotypes at later stages (up to weeks). Many growth-regulating phytohormones influence immune responses and are therefore suggested to be key factors in the growth vs. defense trade-off, although so far, there is no evidence that these hormones directly regulate PTI-triggered growth inhibition.