Comparison of photosynthetic characteristics in seedlings of three kinds of deciduous broad-leaved trees.
With the aid of Li-6400 portable photosynthesis system,the photosynthetic characteristics of the leaves of three kinds of broad-leaved trees Liriodendron chinense,Betula luminifera and Catalpa bungei were measured.The results showed that the net photosynthetic rate,transpiration rate and stomatal conductance of Liriodendron chinense and Betula luminifera presented double-peak curves,and their intercellular CO2 concentrations appeared to vary in W-shaped curves;the net photosynthetic rate,transpiration rate and stomatal conductance of Catalpa bungei presented a single-peak curve,and its intercellular CO2 concentration appeared to vary in a V-shaped curve;Liriodendron chinense and Betula luminifera presented a obvious midday depression of photosynthesis,and non-stomatal factor caused the decrease of the net photosynthetic rate;under same experimental condition,Catalpa bungei showed a higher net photosynthetic rate,Betula luminifera showed a higher stomatal conductance;temperature and humidity were the main environmental factors which influenced the transpiration rate of the three trees.The difference of chlorophyll content in the three trees was comparatively studied,and the results indicated that the order of the shade-tolerant ability was probably Catalpa bungeiLiriodendron chinenseBetula luminifera.