枫香叶片衰老过程中光合能力的变化

利用Li-6400XT便携式光合作用测定系统,于2014年10—12月测定枫香叶片衰老过程中光合作用光响应曲线,采用叶氏模型和非直角双曲线模型进行模拟,分析枫香叶片衰老过程中光合能力的变化.结果表明: 随着枫香叶片逐渐变黄变红,其净光合速率的光响应能力逐渐降低,实测的最大净光合速率从叶片开始泛黄时的2.88 μmol CO₂·m^-2·s^-1下降到叶片衰老后期(12月8日)的0.95 μmol CO₂·m^-2·s^-1.2种光响应模型均较好地模拟了观测的光响应数据,其中叶氏模型表现更优.模拟得到的最大净光合速率、表观量子效率、光补偿点的量子效率、暗呼吸速率等参数均随枫香叶片衰老凋落而逐渐下降,反映出枫香叶片衰老过程中光合能力缓慢下降的过程.在树梢红叶未落期间,枫香叶片仍具有一定的净光合作用能力,这有利于增加秋冬季节的碳吸收量.

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.