[Changes in photosynthetic capacity during leaf senescence of Liquidambar formosana]

In this study, the photosynthetic light response curves were measured for Liquidambar formosana during the leaf senescence from October to December in 2014. The measurements were simulated by a photosynthetic light response model (Ye model) and the conventional non-rectangular hyperbola model, in order to understand the photosynthetic capacity of senescing leaves of L. formosana. The results showed that the light sensitivity of the net photosynthetic rate decreased gra-dually during the leaf senescence. The measured maximum net photosynthetic rate was about 2.88 μmol CO₂·m^-2·s^-1 when the leaf color just turned yellow, and dropped to 0.95 μmol CO₂·m^-2·s^-1 in the later stage of leaf senescence (8th December). The two photosynthetic light-response models performed well in fitting the observation data, with Ye model being slightly better. Parameters estimated from the two models, such as the maximum net photosynthetic rate, the appa-rent quantum yield, the quantum yield at the light compensation point and the dark respiration rate, all gradually decreased with time, quantitatively describing the decrease in the photosynthetic capacity during the leaf senescence for L. formosana. The senescing leaves of L. formosana maintained positive net photosynthesis rates during the whole senescence, which had positive impact on carbon assimilation in the study area.