入侵植物假臭草及其伴生种的光合特性

Comparison of photosynthetic characteristics between an invasive plant,Eupatorium catarium,and associated species

假臭草(Eupatorium catarium)是华南地区的主要入侵植物之一。采用LI-6400便携式光合仪测定假臭草及其主要伴生种苣荬菜(Sonchus arvensis)和山莴苣(Lactuca indica)的光合特性,为探讨假臭草的入侵机制及风险评价提供参考。结果表明,自然光照条件下,假臭草及其伴生种在1d中的净光合速率变化均呈现"双峰"型,但假臭草的平均净光合速率显著高于其伴生种;假臭草的光饱和点(LSP)与光补偿点(LCP)分别为1380、44.72μmo·lm-·2s-1,前者高于伴生种,后者低于伴生种,且与伴生种差异均达到显著水平,表观量子效率(AQY)为0.0568,显著高于伴生种;假臭草的CO2饱和点(CSP)与CO2补偿点(CCP)分别为1211、88.24μmo·lmol-1,前者与伴生种相当,后者显著低于伴生种,假臭草的表观羧化效率(CE)为0.0371μmol·mol-1,显著高于伴生种。较高的光能利用力与较强的光合响应机制,是假臭草能成功入侵的生理基础。

Ecophysiological properties, such as photosynthetic characteristics, contribute significantly to the success of many invasive plant species. Using a field photosynthesis measurement system （LI-6400）, we determined and compared the photosynthetic characteristics of a common invasive plant in Southern China Regions, Eupatorium catarium and two species often associated with it, Sonchus arvensis and Lactuca indica. Results showed that： （1） Net photosynthetic rates （Pn） of E.catarium, S.arvensis and L.indica all displayed ＂double-peak＂ pattern in the day, but the average Pn of E.catarium was significantly higher than that of associated species. （2） Light saturation point （LSP） and light compensation point （LCP） of E.catarium were 1 380 and 44.72 μmol·m-2·s-1, respectively, the former was higher than those of the associated species and the latter was lower. Apparent quantum yield （AQY） of E.catarium was 0.056 8, the highest among the three species, and the difference of AQY was at 5% levels. （3） CO2 saturation point （CSP） of E.catarium was about 1 211 μmol·mol-1 and equivalent to those of S.arvensis and L.indica; CO2 compensation point （CCP） of E.catarium was 88.24 μmol·mol-1, much lower than those of S.arvensis and L.indica; CO2 carboxylation efficiency （CE） was 0.037 1 and higher than those of the other two species. E.catarium had some photosynthetic advantages as important physiological basis of strong invasiveness, such as a higher utilization rate of solar energy and a stronger mechanism of photosynthetic response.