Can you be a bit more specific in your question? What wavelength or power? Otherwise, the answer could range from absolutely nothing, to stimulation of a particular set of photopigments, to burning a hole through it.
Well...I'm interested in the stimulation of growth of plants...especially if there are any studies about pulsed lasers at low frequency ( 5Hz-20KHz ), with wavelengths that stimulate photosynthesis ...the wavelength doesn't matter too much...I just want pulsed lasers that stimulate plants to grow
The wavelength matters a lot - The absorption spectrum of chlorophyll
would indicate that for max effect you would want the wavelength probably centered in somewhere in the "blues" circa
chlorophyll a : 425nm
chlorophyll b : 460nm
unless you have a "sunlight balanced" laser light source
I don't know of any studies on the effect of pusled light, so I can't comment about that.
What mechanisim do you think would be affected by either coherency or pulsing?
Ordinary florescent lighing pulses at 60Hz, even though you don't see it.
I don't know of any particular effects associated with that, given equivilent applied illumination.