Well, I agree with you about this part anyway. The bit about the accessory pigments seems off, however. The action spectrum is based on "whole plant" rather than isolated pigments, so the influence of the accessory pigments is included in the curve.
Originally Posted by 2la
I think lighting spectra are just like any other aspect of maintaining a relatively algae-free tank: It requires balance.
The action spectrum is a direct relationship between photosysnthetic rate of whole-plant pieces to specific wavelengths (more likely, narrow bands) of light, so it is fair to say that increasing pure
blue emissions at 445 nm, where relative photosynthetic efficiency is ~80%, will will give more punch than increasing pure
red emissions at 615 nm by the same amount, where photosynthetic efficiency is ~30%. The issue that you might be alluding to is whether there is a synergistic effect, where the sum of the combined effect for the blue and red light is more than the effect of each wavelength separately. I don't know of any studies that have looked at that, so I would be speculating to say "yay" or "nay."
However, if you want to take the point a bit further, I will say that plants are adapted to true sunlight and no
fluorescent bulb comes close to matching that broad spectrum; the bulbs used for planted tanks all seem to emit in three, relatively narrow phosphor bands. So, at least at that level, plants seem to respond pretty well to narrow wavelength bands. If the synergistic effect of broad bandwidth was a major
factor in plant growth, we would all be using mecury-halogen (MH) lighting. However, the fact that commercial hydroponics do
use MH lighting might argue that the broad-bandwidth synergy is "non-negligible." I certainly wouldn't recommend growing a plant in pure blue light...although it would be interesting to see the effect!!!
29 gal planted tank, 30" FW Aqualights w/ 1x 65W 6700K CF & 1x 55W 9325K CF, 20-lb CO2 w/ Milwaukee SMS122 controller, reverse-flow UGF (bah!), gravel substrate (also bah!), 4 Praecox, 3 Ottocats, 1 SAE, 1 Bristlenose cat, 2-3 C. japonica, 5 Red Cherry Shrimp, & too many detestable pond snails!!!