外来入侵物种空心莲子草光合日变化初步研究

A preliminary study on diurnal courses of photosynthesis in an invasive species,Alternanthera philoxeroides,North China

外来入侵物种空心莲子草(Alternanthera philoxeroides)发生广、危害重的区域多为中国南方省市,2005年发现其已大面积入侵山东省济南市境内的小清河上游。测定了空心莲子草净光合速率、气孔导度和细胞间隙CO2浓度,并与同一生境的芦苇(Phragmites communis)和水芹(Oenanthe javanica)进行了比较。空心莲子草净光合速率日变化曲线为双峰型,最高峰值24.40μmol CO2/(m2.s)出现在10:00左右,第二峰值22.80μmol CO2/(m2.s)出现在16:00左右,整个曲线明显高于对照植物芦苇和水芹。在16:00至16:30光强迅速下降阶段,其净光合速率仍能保持较高水平,为9.85μmol CO2/(m2.s)。

Biological invasion has become a serious environmental problem in China and other countries around the world. Alternanthera philoxeroides,has been issued as one of 16 key invasive species in China （State Environ mental Protection Administration of China, 2003）, and mainly distributed in southern provinces and cities between middle and downstream reaches of Yangtze River. In the summer of 2005, A. philoxeroides had infested the upper Xiaoqing River （N36°41′, El16°53′） on a large-scale in Jinan, Shandong province, North China. To improve people＇s knowledge of its invasive mechanism, net photosynthetic rate, stomata conductance, and intercellular CO2 concentration of A. philoxeroidesas well as those of two other native comparative plants Phragmites communis and Oenanthe javanica in the same habitat were measured. It was found that the diurnal course of net photosynthetic rate of A. philoxeroides varied in a double peak manner with two peaks of 24.40 μmol CO2/（m^2· s） and 22.80 μmol CO2/（m^2 · s） occurring separately at 10：00 and 16：00. This indicated a unusual photosynthetic ＂noon depression＂. Furthermore, the entire net photosynthetic curve of A. philoxeroides was significantly higher than those of P. communis and O. javanica. During the rapid descending photosynthetic active radiation period between 16：00 and 16：30, A. philoxeroides kept its net photosynthetic rate at a comparatively high level of 9. 85μmol CO2/（m^2 · s）.