Abstract: Climate change has exacerbated midday environmental stress, prompting plants to mitigate tissue damage through photosynthetic reduction-a phenomenon termed plant midday depression. Modern technological advancements now facilitate large-scale collection of high-frequency data on carbon–water fluxes and environmental factors. The widespread occurrence of plant midday depression introduces significant uncertainties in terrestrial carbon dynamics estimation and prediction. However, systematic understanding of this phenomenon remains insufficient. In this review, we elucidated the physiological mechanisms governing plant midday depression, and summarized its variability. We further assessed current methodologies for evaluating and predicting plant midday depression. Additionally, we discuss recent advances in understanding the complex interactions between climate change drivers and midday depression, identifying persistent challenges in this research domain. This review aims to establish a foundational framework for future researchers and to elucidate the current scientific understanding. A comprehensive understanding of plant midday depression is essential for accurate prediction of terrestrial ecosystem carbon dynamics under evolving climatic conditions.

Key words: Photosynthetic rate, Bimodal diurnal curve, Climate change, Stomatal conductance, Carbon sequestration