i think they mean the efficiency of the photons being absorbed by the plant. Im looking into pulsing for energy saving reasons, since energy is only required 1% of the time compared to 100% of the time. Yes the current will have to be raised 2-3X higher so that will increase the power used to about 2-3%. In the graph it shows that photosynthesis occurs at the same rate (100%) as long as the pulse is less than 100us.

The response of photosynthesis to photon flux density (PDF) was the same when the light was delivered in pulses as when it was delivered continuously, providing that the frequency was in the range of kHz.
the relative photon requirement calculations shows that the photon requirement in pulsed light is 100% of that in continuous light
so the paper based its research around determining if photon efficiency was higher when pulsed, and i did some reasoning of their research and came to the conclusion that if photosynthesis occurs at the same rate when using alot less energy, then why not use this to our advantage???