I've been doing a ridiculous amount of reading around photosynthesis recently and noticed something.

A lot of hydroponic sites show the following graph (or something very similar), which is from the Sunmaster website;



Here is the spectrum for chlorophyll (b is similar and the carotenoids aren't that far off, neither do you find much of them in leaves);



Why does their graph show plants as absorbing green, yellow and orange light almost as well as they do red and blue? It looks like they've drawn an almost straight line between the peaks.

The fact 99% of plant leaves are green should be a clue that's not right.

SunMaster are not the only people using this graph. I have seen it a lot of different places but the majority of them were selling lamps. I haven't seen it in any scientific literature. Neither are NASA's LED experiments using green, yellow or orange light sources.

Here is the spectrum of the Sunmaster Super HPS. Compare it with their own graph of plant sensitivity and that of cholorophyll's absoprtion spectra;

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Same way people pass around info about CFS vs HID Lights, or using mollasses, or all the other crap they post that starts with "I heard that............."

People will repeat anything.

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i see this alot on this forum. or people mixing up info

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I have a saying about the social dynamics of the internet, "Someone says it, someone repeats, therefore if must be true."

I did alot of research many years ago on HID lights, experimented alot, and found that you need to take spectral graphs with a grain of salt. Experience is what matters. For example, Osram used to have two 600W HPS, the regular and the Plant-A, the latter supposedly having more blue. The spectral graphs were the same. I had a link where someone said companies were falsely stamping their lamps as something they're not, rumors of premature failing, etc. If you can't trust the manufacturer to get it right, who can you trust?

Having said that, I have grown some really nice plants from start to finish with a plain jane HPS. You don't need this and that, conversion lamps, etc. unless you wish to contribute to the bank account of a hydro vendor. The best info I've seen on lighting is Jorge Cervantes' fairly new bible, the real thick one with alot of photos. He did the measurements of various kinds of hoods and lamps. You're buying light, so a well designed and well built hood is very important.

Good luck,
UB

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PLANT MOISTURE STRESS aka leaf edge/tip curling - symptoms and solutions
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Maybe because the first chart is total photosynthetic response and your second graph is chlorophyll A only.
If you look at the other photosynthetically active pigments. plants have additional pigments that participate in photosynthesis. These are indeed called antenna pigments.

β-carotene and the two xanthophylls also have conjugated double bonds and rings at either end, this gives the molecules the ability to absorb light. These are yellow-orange pigments and they absorb light in the blue and green areas of the visible spectrum.



Although you are correct, that first chart looks wrong.
Here's a better one IMO

You make some good points. It's been a while, but I believe chlorophyll A is the most important of the pigments regarding carbo production and one that most folks concentrate on in their discussions.

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PLANT MOISTURE STRESS aka leaf edge/tip curling - symptoms and solutions
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Lets make an advanced organic chemistry thread.

My guess is the manufacturers come up with their gas mixture, make the bulbs, get experimental spectral output, refer to the absorbtion spectra of the various pigments known to photosynthesis, and then model a theoretical plant with pigment proportions that would have a very impressive action spectrum match with their bulb, and print that action spectrum on the box.. Then they'd go back to their experimental spectrum, which would be a series of distinct spikes like the terpine absorbtion graphs Greenhouse Seeds posts on their strain.. And come up with some perverse d_lambda to integrate the energy over wavelength in order to make a pretty continuous spectrum that they can colour like a rainbow, and print that on the box.. (Pretty cynical huh?)
I'd LOVE to see them print actual spectral output on boxes..
On the topic, heres a neat little toy/tool..
http://www.instructables.com/id/Naff..._DVD-Spectra_/

Its simple really, your trying to compare 2 graphs which arent displaying the same data.

The first is sensitivity to light, which is not necessarily the same as light absorption, which is what is displayed in the second.

The first two graphs in post #1 are based on PAR, the 3rd one is based on visual.

Yes, certain gases are your friends.

TEXAS, where farting is considered a sport,
Tio Bendejo

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PLANT MOISTURE STRESS aka leaf edge/tip curling - symptoms and solutions
Note- Due to some technicality, I can not reply to "New visitor messages"