Abstract: As a key factor influencing plant productivity and material cycling, leaf temperature is an important parameter in photosynthesis and respiration models and earth system models. Leaf controls temperature by regulating stomata and morphological traits, consequently maintains leaf temperature suitable for photosynthesis and prevents leaf from being damaged by high-temperature stress. Photosynthesis-weighted leaf temperature (T_L-photo) estimated by the fractionation of plant cellulose (Δ¹⁸O_Cel) integrates leaf temperature during photosynthesis. The stability of T_L-photo indicates the effectiveness of plants in leaf thermoregulation, but the relationship between T_L-photo and air temperature remains uncertain. In this review, we discuss the eco-physiological significance and mechanism of leaf thermoregulation, with emphasis on the theoretical basis, model derivation, and uncertainty of measurement methods and results of T_L-photo estimating from Δ¹⁸O_Cel. We put forward that improving the accuracy of Δ¹⁸O_Cel T_L-photo model and its applicability in studying T_L-photo at different scales of leaf-plant-ecosystem should be the main direction of further research.

Key words: leaf thermoregulation, photosynthesis-weighted leaf temperature, leaf temperature homeostasis, cellulose ¹⁸O, plant functional trait