Stomatal Limitation Is Able to Modulate Leaf Coloration Onset of Temperate Deciduous Tree

Abstract

Autumn phenology, determined mainly by temperature and photoperiod, is essential for ecosystem carbon sequestration. Usually, the variations in the maximum rate of Rubisco (Vcmax) and the maximum rate of ribulose-bisphosphate regeneration (Jmax) are taken as the mechanism regulating the seasonal pattern of photosynthetic rates and autumn phenology. In this study, we used Quercus mongolicus seedlings as an example to examine the photosynthetically physiological mechanism of leaf coloration onset (LCO) responding to different warming and photoperiod treatments based on experimental data acquired from large artificial climate simulation chambers. The results indicated that: (1) LCO and the net CO2 assimilation rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), Vcmax, and Jmax of Quercus mongolicus seedlings were significantly affected by the changes of photoperiod. (2) LCO was significantly correlated only with the Pn approach, supporting the view that leaf senescence is the result of a trade-off between nutrient resorption and reserves. (3) The major variation in stomatal conductance (Gs) is the mechanism by which photoperiod regulates the seasonal pattern of photosynthetic rates, implying that both limitations of stomatal and photosynthetical capacity (Vcmax and Jmax, non-stomatal limitation) are able to modulate LCO. Our study riches the knowledge of phenology and provides a reference for phenological modelling and ecosystem carbon estimation.

Seasonal Photosynthetic Activity in the Crown Compartments of European Ash (Fraxinus excelsior)

“…It is now well established that the photosynthetic CO 2 fixation rate declines in broadleaf tree species with drought stress, i.e., whenever leaf water potential declines from 0 to a critical value of −2.0 to −3.0 MPa [45]. Moreover, photoperiod in the early autumn season appears to be one of the main driving factors decreasing photosynthesis in broadleaf tree species [46], caused by photoperiodand temperature-dependent decreases in the maximum rate of CO 2 fixation by Rubisco and the rate of ribulose-bisphosphate regeneration [47].…”