Lund Vision Group, Lund University, Sölvegatan 35, Lund, 223 62, Sweden.
Zoological Institute, University of Hamburg, Martin-Luther-King Platz 3, Hamburg, 20146, Germany.
Nat Commun. 2019 Jan 22;10(1):238. doi: 10.1038/s41467-018-08142-5.
UV vision is prevalent, but we know little about its utility in common general tasks, as in resolving habitat structure. Here we visualize vegetated habitats using a multispectral camera with channels mimicking bird photoreceptor sensitivities across the UV-visible spectrum. We find that the contrast between upper and lower leaf surfaces is higher in a UV channel than in any visible channel, and that this makes leaf position and orientation stand out clearly. This was unexpected since both leaf surfaces reflect similarly small proportions (1-2%) of incident UV light. The strong UV-contrast can be explained by downwelling light being brighter than upwelling, and leaves transmitting < 0.06% of incident UV light. We also find that mirror-like specular reflections of the sky and overlying canopy, from the waxy leaf cuticle, often dwarf diffuse reflections. Specular reflections shift leaf color, such that maximum leaf-contrast is seen at short UV wavelengths under open canopies, and at long UV wavelengths under closed canopies.
紫外视觉很普遍，但我们对其在常见的一般任务中的用途知之甚少，例如在解析栖息地结构方面。在这里，我们使用多光谱相机可视化植被栖息地，该相机的通道模拟鸟类感光器在紫外-可见光谱范围内的敏感度。我们发现，与任何可见通道相比，在紫外通道中，上下叶片表面之间的对比度更高，这使得叶片的位置和方向清晰可见。这出乎意料，因为两个叶片表面都反射出相似的小比例（1-2%）的入射紫外光。强烈的紫外对比可以解释为下向光比上向光更亮，并且叶子透射的入射紫外光<0.06%。我们还发现，来自蜡质叶片表皮的天空和上方树冠的镜面反射的天空和上方树冠的镜面反射常常使漫反射相形见绌。镜面反射会改变叶片的颜色，因此在开阔树冠下的短紫外波长下可以看到最大的叶片对比度，而在封闭树冠下的长紫外波长下则可以看到最大的叶片对比度。
