We aimed to investigate the adverse effects of urban light pollution on plant growth under the hypothesis that circadian rhythms influence both growth and immunity. Kidney beans were grown under different light durations, and results showed that those exposed to a 12-hour light cycle achieved the greatest average length and exhibited the strongest antibacterial activity. These findings demonstrate that light pollution disrupts intrinsic plant rhythms, impairing health, and highlight the necessity of urban agriculture systems that provide crop-specific optimal photoperiods.