紫茎泽兰光合特性对生长环境光强的适应

测定了不同光强下生长的紫茎泽兰叶片最大净光合速率(Pmax)、叶绿素荧光参数、光合色素含量和比叶重(SLW)，探讨了其光适应能力及生理生态学机制．强光下(100％相对光强)紫茎泽兰发生了轻度光抑制，Pmax、SLW、类胡萝卜素含量和日间热耗散升高，但热耗散能力没有提高．强光下紫茎泽兰通过：1)加强日间热耗散和活性氧清除能力以及光系统Ⅱ反应中心可逆失活来耗散过剩光能；2)增大P～以增加光能利用；3)提高SLW，降低单位干重叶绿素含量以减少光能吸收3个途径避免了光合机构光破坏．弱光下(36％、12．5％和4．5％相对光强)紫茎泽兰日间热耗散很小，SLW降低，但P～较高，这有利于其增加光能吸收和利用效率．紫茎泽兰能在很大的光强范围内有效地维持光合系统正常运转，这可能是其表现较强入侵性的原因之一．

Adaptation of Eupatorium adenophorum photosynthetic characteristics to light intensity

As an invasive species, Eupatorium adenophorum threatens the biodiversity security in Southwest China. To explore its light adaptation characteristics and related eco-physiological mechanism, this paper studied the physiological and morphological properties, e. g., gas exchange, fluorescence kinetics, chlorophyll content and specific leaf weight (SLW), of E. adenophorum grown in Xishuangbanna, China, during the dry season under four light regimes (100%, 36%, 12.5% and 4.5% full sunshine). Under full sunshine, the Fv/Fm and phiPS II decreased with increasing diurnal light intensity, but quickly re-increased when light intensity decreased, indicating that photoinhibition was occurred but not serious. E. adenophorum under full sunshine could increase excessive light energy dissipation through the enhancement of diurnal thermal dissipation and anti-oxidation and the reversible inactivation of PS II reaction center, increase light energy utilization, and decrease light absorption by increasing SLW and decreasing chlorophyll concentration. All these processes enabled E. adenophorum to avoid the photodamage of photosynthetic apparatus. Under low light intensities (36%, 12.5% and 4.5% of full sunshine), E. adenophorum had a higher light absorption and utilization efficiency through decreasing SLW and diurnal thermal dissipation, increasing chlorophyll concentration, and keeping high photosynthetic capacity. The effective dissipation of excessive light energy under high light and the sufficient absorption of light energy under low light allowed E. adenophorum to utilize light energy effectively and grow healthily in a wide range of light intensity, which might be one of the reasons that made E. adenophorum a vigorous invader.