金钟藤叶片的气体交换特性

Characteristics of gas exchange in leaves of Merremia boisiana

用LI-6400便携式光合测定系统（Li-Cor Ine．，USA）对广州林区新发现的入侵杂草金钟藤（Merremia boisiana）叶片的气体交换进行了测定。结果表明；（1）净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（E）的日变化均表现为单峰型曲线，中午金钟藤未出现光合作用抑制；最大光合速率可达20／μmol CO2·m^-2·s^-1左右，Pn日平均值为8．8土0．75μmol CO2·m^-2·s^-1。（2）金钟藤光合作用的光饱和点较高，为1000～1200μmol photons·m^-2·s^-1，表现出比较典型的阳生植物的特性。结果表明，金钟藤在自然环境中具有快速生长的特性可能与其较强和较稳定的光合能力有关。研究的初步结果对了解金钟藤迅速生长、具有高生产力和强大入侵力的原因提供了进一步深入探讨的思路和基础数据。

Some characteristics of gas exchange in leaves of Merremia boisiana were measured by using LI-6400 portable photosynthesis system（Li-Cor Inc. , USA）at Longdong Forest Park in the suburb of Guangzhou City. The diurnal changes in photosynthetic rate（Pn）, stomatal conductance（Gs） and transpiration（E） in M. boisiana growing in situ all exhibited a mono-peak modal,and the peak value of Pn appeared at noon was around 20 μmol CO2·m^-2 · s^-1 without photoinhibition during the daytime, probably resulting from that maximum light radiation（PPFD,photosynthetic photon flux density）at midday nearly equal to PPFD under its light saturation point（LSP）measured by light response curve of photosynthesis and from local habitat. There were also a high er daily average Pn of 8.8±0.75μmol CO2·m^-2·s^-1 and daily maximum Pn of 19.9 μmol CO2 · m^-2 · s^-1 in M. boisiana,indicating higher capacity of gas exchange in this weed growing in natural environment. These results may supply valuable information for understanding why M. boisiana can fast grow and spread with a great production.