Re: How does photoprotection of plants work against UV?

Hi Peter,

I can not find any evidence that plants produce melanin, although some bacteria and fungi do.  
Instead, plants produce compounds called flavonoids that strongly absorb UV light.  In addition, 
plants produce a thin layer of wax on their leaf surfaces that acts to scatter UV light. In fact, 
exposure to UV light causes plants to produce a thicker waxy layer.

Chlorophyll does absorb UV light, and there is some evidence that the absorbed energy can 
contribute to photosynthesis.  However, the UV light causes enough damage to the photosynthetic 
machinery that the overall effect of UV light on photosynthesis is negative.  This phenomenon is 
known as UV photoinhibition.

UV light can cause genetic mutations in plants, but plants do not seem to be susceptible to tumors 
caused by mutations.  Plants do sometimes get tumors, but they are usually due to another 
organism, such as a bacterium or wasp, messing with their metabolism.  These tumors are called 
galls and are typically not a serious problem for the plant.  They do not seem to interfere with any 
major processes in the plant on a large scale, and do not spread throughout the plant the way 
cancer does in animals.

Unfortunately, I do not think there is an easy way to test for the presence of melanin in tissue 
samples withouth having access to a lab that frequently does that kind of testing.

Dr. Alex Brands