Inefficiency of Blue Light

     In reading the APD on Friday (11/15/96), there was a question about
whether or not to use an Actinic fluorescent light bulb to provide blue
	In answer to this question, I know that chlorophyll absorbs light in the
blue region (~450-500 nm), but apparently, it doesn’t use this light very
efficiently.  This is because of the absorption of blue light by the yellow
carotenoid pigments, which are not efficient photosynthesizers.  The
efficiency of photosynthesis using blue light is 20 to 80% of what it is
using red light(~680 nm) for several species of algae.  
	Also, I have found no evidence in the scientific literature that blue light
stimulates the red color in certain plants like Red Hygrophila.  The red
color, which is due to anthocyanin pigments, is stimulated by intense light
to protect the plant from UV radiation.
	Perhaps I have missed something.  Maybe there’s a reason why blue light
would be beneficial to freshwater aquatic plants-- beneficial enough to
warrant buying Actinic light?

Diana L. Walstad