LED without LEDs -My First T5 Grow
Pr0f, from your article link, page 4 right column seems to state 550 nm is the ticket but how much? : Through fitting the data, k and s for the palisade tissue and spongy tissues for 680 and 550 nm were obtained, respectively; 680 nm is the red absorption peak of chlorophyll a in vivo, while 550 nm is green light at which leaves show maximal T L and R L .
and a bit further down...
The calculated values showed abrupt changes at the interface between the palisade and spongy tissues. This is because k and s for these tissues differed. Both k and s for the spongy tissue were much greater than those for the palisade tissue (see legend of Fig. 3 ), reflecting the enhancement of absorption by the détour effect and diffusive nature of the spongy tissue.
On the other hand, for 550 nm, k /2.3 was 1,500, much greater than ε in the green region (<500 m 2 mol –1 for the solution of chlorophylls) even for the palisade tissue. These absolute values are somewhat greater than those obtained for blue light (2,600–2,900 m 2 mol –1 ) and green light (1,000–1,300 m 2 mol –1 ) in spinach leaves ( Vogelmann and Evans 2002 ).
Am I correct thinking mj leaves are Palisade, and if so, then can we hone in on the right amount of Green?
Page 5 left column...
the chloroplasts in the lowermost part of the leaf absorb <10% of those in the uppermost part, even at a wavelength of 550 nm at which the absorption gradient is most moderate.
Page 7 left column...
For upright or pendulous leaves, it has long been known that the sharpest light response curves are obtained when these leaves are irradiated equally from both sides ( Moss 1964 , Tanaka and Matsushima 1970 , Evans et al. 1993 ).
Pr0f gets his due:
A more straightforward method to detect such a difference in light saturation would be to monitor fluorescence from both sides of the leaf, in order to assess the PSII quantum yields or Genty's parameters for each side ( Genty et al. 1989 ). After formulation by Genty et al. (1989) , the linear electron transport rate from water to NADP + for the whole leaf has been frequently estimated as: (4)
where α is the absorptance of the leaf, ϕ PSII is the fraction of
excitation energy allocated to PSII, F m ′ is the maximal fluorescence in the light, and F s ′ is the fluorescence level in the presence of actinic light.
Bottom of page 7- top of 8
The greatest decrease in F v /Fm in the uppermost part of the leaf was observed with blue light, and F v /F m approached high levels at depth. The second greatest damage to the surface chloroplasts was observed with red light, but the damage was confined to the irradiated half of the leaf. On the other hand, damage to the surface chloroplasts was least with green light, but continued deep into the leaf, probably because sufficient green light penetrated and was absorbed by the chloroplasts in the abaxial side.
As has been explained above, it is dangerous to assume that the
fluorescence signals obtained from the irradiated side of a leaf represent the quantum yield of the chloroplasts within the whole leaf. In particular, when the chloroplasts near the irradiated surface are photoinhibited, the misleading effect would be very large.
In situ quantum yield of monochromatic light in white light. As Nishio (2000) clearly postulated, and as we have detailed so far, red or blue light is preferentially absorbed by the chloroplasts in the upper part of the leaf. Then, when PPFD is high, the energy of these wavelengths tends to be dissipated as heat by the upper chloroplasts, while green light drives photosynthesis in the lower chloroplasts that are not light saturated ( Sun et al. 1998 , Nishio 2000 ). However, there has been no quantitative evaluation of this possibility. Here, we propose a new method to quantify the quantum yield of monochromatic light contained in white light.
This seems like confirmation...
Page 9 Thus, in this study, we compared the effects of green light at 550 nm and red light at 668 nm. Judging from the
action spectra of green leaves ( McCree 1972 , Inada 1976 ), the
red light at 668 nm used in this study would not cause the marked red-drop effect. Moreover, the measurements were conducted in the presence of the background white light.
The data shown in Figs. 10 and 11 clearly demonstrate that green
light more effectively drove photosynthesis than red light in
the white light at high PPFDs.
Although the light absorption profi les calculated by Nishio (2000) are spurious ( Vogelmann and Evans 2002 ), his argument has nevertheless been proven experimentally to be correct using our differential quantum yield method. Namely, red light is more effective than green light in white light at low PPFDs, but as PPFD increases, light energy absorbed by the uppermost chloroplasts tends to be dissipated as heat, while penetrating green light increases photosynthesis by exciting chloroplasts located deep in the mesophyll. Thus, for leaves, it could be adaptive to use chlorophylls as photosynthetic pigments, because, by having
chlorophyll with a ‘green window’ the leaves are able to maintain high quantum yields for the whole leaf in both weak and strong light conditions.
So while this confirms what I read on GSLs website (LED mfg) I don't think it answers the ultimate question "How much 550 nm Green do we need?" Say in my 8 bulb Bad Boy should I have 1/8, 2/8...?