[Xenonman]

I am a bit more clueless than usual here.
I considered normal that UV-revealed TLC plates glow green and compounds glow dark red. We separated a plant mixture for the first time. It had a lot of colors under visible light, and more exotic ones in UV. There was a bright red and a bright yellow.

I know that red objects, under visible light, for some reason, absorb all but red light. Some species deflect certain wavelenghts, as [Co(NH₃)₆]^+2? bouncing blue light back.  Compounds with conjugate insaturations acquire a color also. Their color may change depending on the nearby functional groups.

I think these bright red and bright yellow spots are massive conjugate-insaturation compounds with varying auxochromes that give wildly different wavelenght absorption. Is this right?

Also, why would they appear red? Red wavelenghts are far away from the UV spectra.

[Xenonman]

Found a picture of it:

[Borek]

Wavelength emitted by fluorescence can be completely unrelated to the exciting UV (the only thing that you can be sure about, is that it won't be shorter).

[Xenonman]

Now I know answering this question is not an easy one, and requires studying UV and fluorescence.  I may do it one day.
Thanks, Borek.