Integrated circadian regulation in horticultural plants: light-environment mechanisms governing growth and development.

The circadian clock enables plants to synchronize physiological and developmental processes with daily and seasonal light fluctuations. In horticultural crops, this endogenous oscillator interacts with photoperiod, light quality, and light intensity to coordinate flowering, growth, metabolism, and stress adaptation. Photoperiodic control, mediated largely by the conserved CONSTANS (CO)-FLOWERING LOCUS T (FT) module, governs flowering transitions and vegetative-reproductive balance in horticultural crops, such as strawberry, chrysanthemum, cucumber, tomato, and potato. Spectral composition, particularly red/far-red and blue light perceived through phytochromes and cryptochromes, reshapes circadian amplitude and phase to regulate photosynthesis, morphogenesis, and secondary metabolism. Meanwhile, light intensity adjusts oscillator robustness and energy allocation, influencing rhythmic stability under controlled-environment cultivation. The emerging research topics such as on species-specific clock diversity, circadian regulation of quality traits, and precision lighting strategies aligned with rhythmic principles were also discussed. Analyzing the interaction between light signals and the biological clock will help deepen our understanding of the time regulation mechanism in horticulture plants, and can provide a basis for designing optimized periodic cultivation systems in horticulture, thereby improving yield and quality of horticultural crops. In this review, we will summarize the research findings on how light environments regulate the circadian rhythms of horticultural plants, as well as their potential applications in horticulture.