Plants are continuously subjected to environmental variations, with daily rhythms consistent 24-h light and darkness patterns particularly crucial. The rhythms significantly impact plant physiology, growth, and development by controlling various processes, including photosynthesis, stomatal movement, hormone synthesis, and gene expression. The capacity of plants to predict and react to these daily fluctuations enables them to maximize their energy utilization, ensure equilibrium in water retention, and synchronize metabolic processes. This chapter examines how plants perceive and respond to daily rhythms, explicitly emphasizing the involvement of circadian clocks, photoreceptors, and hormonal pathways. This text also discusses the interaction between environmental parameters such as temperature, humidity, and light intensity with these rhythms, impacting plants' general health and productivity. Enhancing crop performance and resilience in agriculture, especially in climate change and controlled-environment agriculture, requires a comprehensive understanding of plant reactions to environmental periodicity.