云南菊科入侵物种与本地共生物种光合特性比较

为了探求菊科入侵植物的入侵机制,了解菊科入侵植物与非入侵植物光合特性的差异,以云南省包括薇甘菊(Mikania micrantha)、紫茎泽兰(Ageratina adenophora)、飞机草(Chromolaena odorata)、三叶鬼针草(Bidens pilosa)在内的4种菊科入侵物种为研究对象,并以与其共生的菊科外来非入侵物种熊耳草(Ageratum houstonianum)为对照,研究外来入侵物种与非入侵物种叶片特性及气体交换参数等方面的区别. 结果表明:薇甘菊、紫茎泽兰、飞机草和三叶鬼针草的P_nmax(maximum net photosynthetic rate, 最大净光合速率)分别为15.92、18.69、17.15和22.78 μmol/(m2·s),分别比其共生非入侵物种熊耳草的高出21.63%、42.77%、31.02%和73.99%；4种入侵物种的LSP(light saturation point, 光饱和点)和LCP(light compensation point, 光补偿点)也显著高于熊耳草,但其AQY(apparent quantum yield, 表观量子效率)却显著低于该共生种. 4种入侵物种叶片的N_mass(leaf N content per unit mass, 单位质量N含量)和CC_mass(leaf construction cost per unit mass, 单位质量建成成本)均显著高于熊耳草,除飞机草外,其他3种入侵物种的PEUE(photosynthetic energy use efficiency, 光合能量利用效率)和PNUE(photosynthetic nitrogen use efficiency, 光合氮利用效率)均显著高于熊耳草,而飞机草和熊耳草之间差异并不显著. 5种植物叶片N_mass分别与叶片SLA(specific leaf area,比叶面积)、CC_mass呈极显著正相关,与植物P_nmax、叶片P_mass(leaf N content per unit mass, 单位质量P含量)和PEUE呈显著正相关,植物P_nmax与PNUE、PEUE呈极显著正相关,与叶片SLA呈显著正相关. 研究显示,与菊科共生外来非入侵植物相比,较高的光合特性参数、叶片特性指标和能量利用效率指标可能是外来菊科入侵物种成功入侵的原因之一. 

Comparison of Photosynthetic Characteristics between Invasive and Co-Occuring Native Asteraceae Plants in Yunnan Province, China

Plant invasions have become a serious environmental and socioeconomic problem and a hot topic of ecological research worldwide. Invaders colonize resource-poor environments, but the mechanisms that contribute to their success in these systems are poorly understood. Invasive species may succeed in low-resource environments by employing resource-acquiring traits such as high resource-use efficiency. The photosynthetic characteristics were compared between four invasive Asteraceae, including Mikania micrantha, Ageratina adenophora, Chromolaena odorata and Bidens pilosa, and its co-occuring Asteraceae plant Ageratum houstonianum in Yunnan Province. We hypothesized that these exotic invaders may have higher resource capture abilities and utilization efficiencies when compared with native plants. To test the hypothesis, ecophysiological traits including net photosynthetic rate (P_n), water use efficiency (WUE), photosynthetic nitrogen use efficiency (PNUE), photosynthetic energy use efficiency (PEUE), specific leaf area (SLA), leaf P content per unit mass (P_mass), leaf N content per unit mass (N_mass), chlorophyll content, and mass-based and area-based leaf construction cost (CC_mass and CC_area) were measured. The results showed that:the maximum net photosynthetic rates (P_nmax) of M. micrantha, A. adenophora, C. odorata and B. pilosa were 15.92,8.69,7.15 and 22.78 μmol/(m2·s) respectively, significantly higher than that of A. houstonianum by 21.63%, 42.77%, 31.02% and 73.99% respectively (P<0.05). Light saturation point (LSP) and light compensation point (LCP) of the four invasive plants were also significantly higher than those of A. houstonianum, but apparent quantum yield (AQY) was significantly lower (P<0.05). PEUE and PNUE of the four invaders were also significantly higher than those of native plants, with the exception of C. odorata (P<0.05). Correlation analysis indicated that N_mass was positively correlated with leaf SLA, CC_mass, P_nmax, P_mass and PEUE, while P_nmax was positively correlated with leaf SLA, PNUE and PEUE (P<0.05). In summary, superior photosynthetic characteristics and higher energy utilization efficiency may contribute to the successful invasion of the four Asteraceae invasive plants when compared with their co-occurring natives.