泡桐生长停止和顶芽死亡过程中的光合特性研究

以毛白33泡桐为研究对象，通过外部形态观察研究泡桐生长停止和顶芽死亡过程，同期观测其光合特性，并分析影响光合速率的主要因素。结果表明:泡桐的高生长停止于9月下旬；9月底10月初，多数泡桐顶芽已经由绿变褐而干枯；地径生长的停止期晚于高生长；泡桐光合速率的日变化是双峰型，存在光合午休现象； 叶片净光合速率与蒸腾速率、光合有效辐射、气孔导度呈极显著正相关性；叶片净光合速率与叶温呈显著正相关性；非气孔因素可能是诱导泡桐顶芽死亡的主要原因；9—10月泡桐的光合速率有所下降，但仍维持较高的水平，且主要用来粗生长和休眠侧芽的形成；泡桐顶芽枯死是进化过程中采取的一种适应策略。 

Photosynthetic characteristics of Paulownia during growth cessation and terminal buds'death

The cources of growth cessation and terminal bud's death of Paulownia tomentosa x P. Fortunei 33 were investigated through external morphology. Simultaneously, photosynthetic characteristics were observed and the main influencing factors of photosynthetic rate were analyzed. The results were as the followings:height growth stopped in late September; at the end of September and early October, most of terminal buds changed from green to brown and drying; stop date of diameter growth was later than height growth'. P_nshowed two peaks in clear day and midday depression was observed. P_nwas extremely remarkable relevant with T_x, PAR, G_s, and remarkable relevant with t_1. Terminal bud's death was mainly induced by nonstomatal factors. In September and October, P_n declined, but still maintained a high level. Photosynthate was mainly used for diameter growth and formation of lateral dormancy buds; terminal bud's death is an adaptation strategy during evolution course of Paulownia.