This cactus flower appears to fluoresce with appropriate backlighting.
The shorter wavelength light, much of it invisible, is hitting the flower causing it to radiate longer wavelength visible light.
Many cacti flowers remain in bloom for less than a day, including this one. Hedgehogs tend to bloom during the daylight hours and need to attract sighted pollinators. Moving invisible radiation into visible light can only help in getting the attention of these pollinators.

This flower is a light bulb.