Light supplies energy for photosynthesis, while its spectral composition also acts as an environmental signal. significantly enhanced oscillatory robustness. However, how light quality is associated with coordinated changes in circadian regulation and photosynthetic responses remains insufficiently understood. In this study, pak choi was used as the experimental material to establish a coupled analytical framework linking light-quality input, core circadian components comprising CCA1/LHY, PRR9/PRR7, PRR5/TOC1, and ELF4/LUX, and photosynthetic responses.Relative to the white-light reference, the tested continuous red-light regime showed later fitted peak times of core clock genes, whereas the blue-light regime showed earlier phases. These differences were observed under unequal source PPFDs and treatment DLIs. In contrast, red-blue combined light, particularly dynamic intermittent red-blue supplementation, significantly enhanced oscillatory robustness and maintained a circadian pattern closer to that under white light. Among the photosynthesis-related genes examined, BcLhcb1 showed a pronounced response to the lighting treatments and was therefore selected for further analysis, and its expression rhythm was tightly coupled with core clock components such as CCA1/LHY. BcLhcb1 expression covaried with clock-gene expression, photosynthetic pigment contents, and photosynthetic responses measured under a common reference condition. These associations support a working hypothesis involving a BcLhcb1-associated regulatory module, but do not establish that BcLhcb1 mediates the physiological responses to the lighting treatments. Pn was measured under a common reference condition, and its time integral was interpreted as an index of reference-condition photosynthetic capacity. These findings support further evaluation of alternating lighting schedules, while their effects on actual daily carbon gain and electrical energy efficiency remain to be established. Model simulations identified the 3 h white light + 1 h red-blue combined-light schedule (3L:1X) as the most favorable among the simulated timing schemes, and this regime was subsequently evaluated experimentally. The coordinated responses support an association between clock-gene rhythms, Lhcb1 expression, and photosynthetic acclimation. However, the design does not distinguish the contributions of spectral composition, irradiance, and temporal exposure. The results identify an alternating-light regime for further evaluation using intensity-matched controls. These results suggest that alternating white and red-blue light may provide a promising temporal lighting strategy for modulating circadian and photosynthetic responses in pak choi.
