Oh yes, there are dotEdu studies and private studies on the effects of spectrum and intensity on cannabis growth and morphology. Many times these do build upon past knowledge such as Pr/Pfr phytochromes ratios, et al. Migro has created some accessible video on spectrum and growth. Such studies, along with economics, have generated what we see on the market today in terms of spectral balance.
As far as the photo-synthetic reception centers, the quantity varies by acclimatization of the plant to the light intensity. It goes both ways when moving into different environments. The most notable is low to high intensity while high to low tends to be more ‘hidden’ … but rest assured that plant will need to acclimatize by building new photo-synthetic reception centers under the newer and lower intensity lighting. Even more, light from the sun will have an intensity that is much more consistent top to bottom … so the plant is temporarily less efficient at the collection of photons particularly lower on the plant as it enters into a less intense environment.
Interesting thought. Don’t know but I’d surmise that the plant will temporarily not be able to capture enough photons and will be the limiting factor while the plants re-acclimatizes. The excess carbon in the Calvin cycle will have minimal effect as the generation of ATP is temporarily reduced due to the number of photosynthetic reaction centers available. My presumption is assuming that there is a step change in the light intensity.
Here is the spectrum and PPFD for sunlight 11AM Northeast long days:
Integral radiant (400-700nm): 341.7 W/m^2
Integral radiant (350-840nm): 483.8 W/m^2
PAR (400-700nm): 1580 umol / m^2 s
YPF (360-760nm) : 1412 umol / m^2 s
YPF/PFD: 0.89
PSS: 0.72
DLI index [12 hours] : 68.3
And, likewise, Fluence Spydr 2P PhysioSpec Indoor:
Integral radiant (400-700nm): 186.4 W/m^2
Integral radiant (350-840nm): 192.3 W/m^2
Lumens (m^2) : 54821
Spectrometer PFD (400-700nm): 889.56 umol / m^2 / s
Spectrometer PFD (350-840nm): 925.5 umol / m^2 / s
Quantum Sensor PFD (400-700nm): 850.4 umol / m^2 / s
YPF (360-760nm) : 791.86 umol / m^2 / s
YPF/PFD: 0.89
PSS: 0.86
DLI index [12 hours] : 38.4
As noted above, sunlight is comparatively intense at nearly ~1600 PPFD vs ~850 PPFD, in this instance. And, distance of the plant from the sun will not matter unlike fixtures.
There’s some example spectra here that may be of interest to those looking into spectra stuff (mostly LED though):
p.s. the YPF is a more modern take on the photosynthetic photon ‘yield’. It is weighted by spectra and extends further based on research on useable spectra. Here is an example YPF vs PAR. Each is integrated across the curves to create the PFD and YPF metrics:
Plants are capable of utilizing a broad range of spectra. Different spectra can affect plant morphology, as noted. Shade avoidance, efficiency, Pfr/Pr, etc.