Let's be clear here. The energy of the photon has little to do with rates of photosynthesis. However, it does matter when it comes to effects on organic tissues.Led's by their nature have a high output of energy from a small area. It's only a matter of degrees. Blue to UV photons if course have high energy and concentrated (think lenses/magnifying glass) each can transfer enough energy to "burn" things as does any "color" with the right focus, think laser.