β-cyclocitral elicits rapid signaling distinct from the excess-light response in Arabidopsis

β-Cyclocitral (β-cc), a β-carotene oxidation product, has been proposed as an early retrograde signal that primes protection against photooxidative stress. Its temporal relationship with photosynthetic acclimation, however, remains unresolved. Exogenous β-cc elicited cytosolic Ca²⁺ changes within minutes and induced the β-cc-responsive pAER::LUC detoxification reporter within 40 min. We exposed Arabidopsis thaliana plants to 1500 μmol photons m⁻² s⁻¹ under ventilation creating a high-irradiance regime without concomitant heat stress and with a relatively mild photooxidative outcome (RT-EL). Non-photochemical quenching increased, whereas PSII maximum quantum yield progressively decreased during RT-EL, with both responses approaching a plateau by 16 h. Volatile β-cc pretreatment did not improve photosynthetic performance or NPQ dynamics, whereas endogenous β-cc and β-cyclocitric acid accumulated only after prolonged RT-EL exposure (16 h). By contrast, hormone profiling and RNA-seq revealed extensive β-cc–dependent reprogramming that was largely opposite to the RT-EL transcriptional response. Together, these results reveal a kinetic separation between rapid β-cc signaling and its endogenous production. Under RT-EL major photosynthetic adjustments precede detectable β-cc accumulation, whereas β-cc triggers cellular responses within minutes once present. We therefore propose that the timing of β-cc action during excess light is determined primarily by the onset of substantial β-carotene oxidation.