no but I would guess if it were used on a big concave surface it could create a hot spot if enough light hit it in just the right way. but most people use flat walls I would imagine :-). I also bet that if the light lumen output was just enough for optimal grow conditions for the amount you have growing then the more you can bounce that amount of lumens to the plant all around then the plant will thrive. aluminum I think will actually sponge more of the lumens than even flat white paint could.
oh nice icon by the way my old band opened for Pantera back in 1994 :-)