Tuesday, June 21, 2011

[VIS, UV] Rudbeckia inside out - different UV reflectances inside and outside

Noticed today, how different the UV reflectance of a freshly unfolding flower (here Rudbeckia fulgida) could be, comparing the outside and inside of the flower petals. Totally invisible to the human naked eye, but surely not to pollinating insects!

UV sensitive camera, Cerco 94mm lens, Baader-U resp. UV/IR Cut filter; standardized UV palette using my ReflectionDisc

[click on images to see larger ones]

Standardized reflected false UV "colors" according to the previously described "UV color palette" related to wavelength:

UV shot:

VIS comparison shot:

I have some theory about that different reflection: I think it makes no (biological) sense that a flower attracts an insect when the flower is not ready yet, nor has anything rewarding to offer i.e. sending out (UV-) signals that would rather lead to "frustrated pollinators" which would most likely quickly learn not to visit such flowers anymore. So, having the outside, less UV-reflective "shield" the opening flower, makes it less attractive to insects, unless the flower has fully opened and also has nectar, thus rewarding pollinators for their visit.

Interesting to see how that UV pattern will develop within the next days; let's see ...

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos