南京椴和心叶椴苗期光合特性比较

利用Li 6400便携式光合作用测定仪，分别测定南京椴(Tilia miqueliana)和心叶椴(T.cordata)2年生苗木叶片的净光合速率(Pn)、气孔导度(Cond)、蒸腾速率(Tr)和胞间CO2浓度(Ci)等指标的日变化，对两树种光合特性进行对比分析。结果表明：8月中旬天气晴朗时，两种椴树净光合速率、气孔导度和蒸腾速率均呈双峰曲线，胞间CO2浓度变化呈单谷曲线；两树种的光补偿点分别为36.2 μmol/(m2·s)和22.8 μmol/(m2·s)，光饱和点分别为1 384.8 μmol/(m2·s)和1 216.5 μmol/(m2·s)，CO2补偿点分别为76.4 μmol/mol和80.9 μmol/mol，CO2饱和点则分别为1 872.5 μmol/mol和1 655 μmol/mol。基于对这两个树种净光合作用的分析，笔者发现南京椴净光合速率日均值大于心叶椴。

Comparison on the photosynthetic characteristics between Tilia miqueliana nd T.cordata at seedling stage

The photosynthetic rate, stomatal conductance, transpiration rate and intercellular CO2 concentration of the 2-year-old Tilia miqueliana and T.cordata were measured under field condition on sunlight day of August using Li-6400 portable photosynthesis system. The photosynthetic characteristics of the two species were compared. The results showed the rate of foliar photosynthesis, the rate of foliar respiration, the rate of foliar transpiration and stomatal conductance changed in a double-peak curve. However,...