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Action Spectrum - Red vs blue?

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Action Spectrum - Red vs blue?

Postby Micky T » Thu Sep 14, 2006 4:18 pm

Chlorophyll absorbs light at either red or blue wavelengths, but there is a definite difference between the two 'peaks' in increased rate of photosynthesis.

Does anyone know why this is? any information would be extremely handy as I cannot seem to find any useful information :(
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Postby MrMistery » Thu Sep 14, 2006 6:02 pm

why? hmm,, no idea... it is about the properties of the molecule. it absorbs photons at a higher rate in the red spectrum than in the blue one. however, carotenoids can also absorb some blue light and give it to chlorophil, but red light remains the best light for most plants...
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Postby Linn » Fri Sep 15, 2006 3:25 pm

isnt the primary peak absorbtion spectrum in the blue-violet? and then in the red. Sorry if I dont understand the question :oops:
in between the difference is because Light in the green/yellow range is reflected.
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Postby Micky T » Fri Sep 15, 2006 3:32 pm

Sorry...my question writing ability isn't great. I meant that the two peaks, the red and the blue, are not equal - as in a plant can more easily absorb blue light than red light, according to the absorption spectrum, and have an increased rate of photosynthesis in blue light than in red. So why is there a difference? why can't they both be equal? :(

Or is this a pointless question as it is just because of the pigment, and thats just the way it is? :?
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Postby Linn » Fri Sep 15, 2006 5:30 pm

Micky T wrote:Sorry...my question writing ability isn't great. I meant that the two peaks, the red and the blue, are not equal - as in a plant can more easily absorb blue light than red light, according to the absorption spectrum, and have an increased rate of photosynthesis in blue light than in red. So why is there a difference? why can't they both be equal? :(

Or is this a pointless question as it is just because of the pigment, and thats just the way it is? :?


???? I dont know either
guess....The shorter the wavelength the greater the energy??? :?

= more reaction

PS: I have heard that there are pigments (cant remember the names)that are responsive to blue wavelength that control reactions, so you may be on to something there.
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Postby MrMistery » Fri Sep 15, 2006 7:44 pm

@Linn
I think the example you are looking for is zeaxantin. it serves as a receptor so that stomata open in daylight.
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Why?

Postby csi_freak_15 » Sun Feb 18, 2007 6:48 pm

Can anyone (online) please tell me why red light is more efficient than blue? :?
I haven't got a clue.
I really need to know this tonight if anyone can hellp!
Thank you!
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Postby mith » Sun Feb 18, 2007 8:44 pm

try forum search
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Postby Volvox » Mon Feb 19, 2007 1:51 am

I think red light is more efficient than blue light because although they "excite" electrons at high energy states, the energy state of blue light is higher than that of red light.
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Postby Ali Asim » Fri Feb 23, 2007 7:18 pm

Micky T and all other having confusion about RED and BLUE light infact there is no matter that one is more effective than other. both are important which help to grow the plants of paticular wehther, whcich depend on short day and long day. it can not be explained here in detail. I suggest all to search the topic by the name of "PHOTOPERIODISM" in which it is clear that how Red or blue lights are effective in growth of plants and i also suggest to see the "PHYTOCHROME" which can be search on http://www.wikipedia.com ......
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Postby MrMistery » Fri Feb 23, 2007 7:43 pm

phytochrome and photoperiodism are important, but i think you missed the point of the discussion...

By the way, red light is more effieciently used by plants because blue light has much more energy, which cannot be used. It's all in the number of photons. Look up photosynthetic photon flax density...
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Postby Micky T » Thu Mar 15, 2007 12:33 pm

This is just what I've thought of so far - correct me if you see I am wrong

If the light intenisty of the red or blue light remains constant, for both colours, both will have the same amount of energy given to the plant. But, although the energy being given to the plant is constant, the rate of photosynthesis differs between red and blue light.

As plants do not contain only one pigments, the concentration and proportions of the pigments alter the action spectrum of the plant. For example if the plant being studied contains large proportions of chlorophyll B, it will absorb more energy from light around 480nm wavelength (blue) compared to that in the 650nm wavelegnth area. However, the two peaks would be more or less equal in chlorophyll A was in the greatest proportions.

As far as I can understand, it is just the ratio of the pigments in the chloroplasts, and this is often different between different species. I have already looked into this by running chromatograms of the pigments from Elodea Canadensis and Urtica dioia. They seemed to contain differing concentrations of pigments, and almost completely different accessory pigments. I know this is all very weak, but it's the only idea I've really come up with. :(

Here are the chromatograms - you probably can't tell much from these, but i'll put them on just in case anyone wants to see them
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chromatographySN.jpg
Stinging Nettles
chromatographyElodea.jpg
Elodea
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