Ultraviolet Flowers: Ranunculus acris

Ranunculus acris L.

Ranunculaceae

Ranunculus acris. Visible light

Visible light
Nikon D1H , UV-Nikkor 105 mm f/4.5, no flash

Ranunculus acris. UV light

UV light
Nikon D1H , UV-Nikkor 105 mm f/4.5 @800 ISO, Hoya U-360, SB-140

Ranunculus acris. IR light

IR light
Nikon D1H , UV-Nikkor 105 mm f/4.5 @800 ISO, Wratten 89 B, SB-140 + Wratten 87

Meadow Buttercup has bright yellow flowers showing a very strong UV pattern. The petals have oily glands towards their base and this area evidently absorbs UV very efficiently. The outer petals don't reflect UV to a very large extent, but still enough to achieve a prominent bull's-eye pattern.

The reflectance in near-IR is less than in UV, but interestingly even here a two-zoned pattern can be demonstrated. This is the one of the few example of such a trait found in my studies and I'm not certain about its ecological significance.