Institute of Botany, Darmstadt University of Technology Darmstadt, Germany.
Front Plant Sci. 2012 Jan 13;2:117. doi: 10.3389/fpls.2011.00117. eCollection 2011.
Here we present the first study, in which a large number of different vascular epiphyte species were measured for their photosynthetic performance in the natural environment of their phorophyte in the lowland rainforest of French Guyana. More than 70 epiphyte species covered the host tree in a dense cover. Of these, the photosynthesis of 16 abundant species was analyzed intensely over several months. Moreover, the light environment was characterized with newly developed light sensors that recorded continuously and with high temporal resolution light intensity next to the epiphytes. Light intensity was highly fluctuating and showed great site specific spatio-temporal variations of photosynthetic photon flux. Using a novel computer routine we quantified the integrated light intensity the epiphytes were exposed to in a 3 h window and we related this light intensity to measurements of the actual photosynthetic status. It could be shown that the photosynthetic apparatus of the epiphytes was well adapted to the quickly changing light conditions. Some of the epiphytes were chronically photoinhibited at predawn and significant acute photoinhibition, expressed by a reduction of potential quantum efficiency (F(v)/F(m))(30'), was observed during the day. By correlating (F(v)/F(m))(30') to the integrated and weighted light intensity perceived during the previous 3 h, it became clear that acute photoinhibition was related to light environment prior to the measurements. Additionally photosynthetic performance was not determined by rain events, with the exception of an Aechmea species. This holds true for all the other 15 species of this study and we thus conclude that actual photosynthesis of these tropical epiphytes was determined by the specific and fluctuating light conditions of their microhabitat and cannot be simply attributed to light-adapted ancestors.
在这里，我们首次进行了一项研究，在法属圭亚那低地雨林中，对大量不同的附生植物物种在其宿主植物的自然环境中的光合作用性能进行了测量。超过 70 种附生植物在宿主树上形成了密集的覆盖层。其中，对 16 种丰富物种的光合作用进行了长达数月的深入分析。此外，利用新开发的光传感器来对光环境进行了研究，该传感器可以连续、高时间分辨率地记录附生植物附近的光强度。光强度波动很大，显示出具有特定地点和时间变化的光合光子通量。使用一种新的计算机程序，我们量化了附生植物在 3 小时窗口内接收到的综合光强度，并将其与实际光合作用状态的测量结果相关联。结果表明，附生植物的光合作用器官很好地适应了快速变化的光照条件。一些附生植物在黎明前就长期受到光抑制，并且在白天还观察到明显的急性光抑制，表现为潜在量子效率（F(v)/F(m)）(30')的降低。通过将（F(v)/F(m)）(30')与前 3 小时感知到的综合和加权光强度相关联，清楚地表明急性光抑制与测量前的光环境有关。此外，光合作用性能不受降雨事件的影响，除了一种 Aechmea 物种。对于本研究中的其他 15 种物种也是如此，因此我们得出结论，这些热带附生植物的实际光合作用是由其微生境的特定和波动的光照条件决定的，而不能简单地归因于适应光照的祖先。
