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Does oxygen production in photosynthesis require CO2?

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Does oxygen production in photosynthesis require CO2?

Postby Oistrakh1 » Mon Nov 10, 2008 12:58 am

Since oxygen is produced in the light reactions and carbon dioxide is produced in the dark, and since the light reactions don't depend on the products in the dark reactions, does the carbon dioxide concentration not have an effect on the oxygen production?
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Postby xxrandompersonxx » Mon Nov 10, 2008 1:49 am

YES, to the ques. of the title. Well, photosynthesis doesn't necessary depend on the products of dark phase but if I remembered correctly, the light and dark phase uses each other's products, because the ATP and NADPH2 produced in light phase are needed in the dark phase to create other compounds. Because the CO2 produced during respiration in mitochondria's also used for photosynthesis so I suppose CO2 produced during dark phase can be used as well (during dawn when there's starting to be light). The key's that all organisms are designed in a way so that most of their products are not wasted.
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Re:

Postby MichaelXY » Mon Nov 10, 2008 2:44 am

xxrandompersonxx wrote:YES, to the ques. of the title. Well, photosynthesis doesn't necessary depend on the products of dark phase but if I remembered correctly, the light and dark phase uses each other's products, because the ATP and NADPH2 produced in light phase are needed in the dark phase to create other compounds. Because the CO2 produced during respiration in mitochondria's also used for photosynthesis so I suppose CO2 produced during dark phase can be used as well (during dawn when there's starting to be light). The key's that all organisms are designed in a way so that most of their products are not wasted.


Wrong! O2 production in the light reaction does not require CO2. Light reaction uses H2O and light, O2 is given off as a byproduct.

The Calvin cycle uses CO2 from the stomata along with NADPH and ATP created in the light reaction to make glucose C6H12O6.
Last edited by MichaelXY on Mon Nov 10, 2008 2:48 am, edited 1 time in total.
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Postby Oistrakh1 » Mon Nov 10, 2008 2:48 am

So if I cut off CO2 supplies, it would still generate O2 even if it wouldn't generate sugar?
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Re:

Postby MichaelXY » Mon Nov 10, 2008 2:50 am

Oistrakh1 wrote:So if I cut off CO2 supplies, it would still generate O2 even if it wouldn't generate sugar?


Correct, for how long I dunno as the plant would die eventually.
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Postby MichaelXY » Mon Nov 10, 2008 2:51 am

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Postby Oistrakh1 » Mon Nov 10, 2008 3:17 am

so a photosynthetic plant's oxygen production is not at all correlated to its CO2 consumption?
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Re:

Postby MichaelXY » Mon Nov 10, 2008 3:46 am

Oistrakh1 wrote:so a photosynthetic plant's oxygen production is not at all correlated to its CO2 consumption?


Well I did not say that, there is some relationship. The byproduct O2 production occurs in the manufacturing of ATP and NADPH during the light reaction to synthesize CO2 to glucose. Stomatal openings are influenced by several environmental factors. I believe CO2 concentration in the organism is one of them.
I am not sure on this one but I imagine it is like a supply and demand thing. The plant is able to control its stomata based on H2O and CO2 concentration. I suspect they work in harmony but this is beyond my understanding :oops:

I think one of the other members like Mr. Mistery can give you a more precise answer.
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Postby MrMistery » Mon Nov 10, 2008 7:27 pm

Actually you will only be able to generate oxygen for a very, very little while. This is because the light reactions require NADP+ in order to proceed. Normally the Calvin-Bensen cycle consumes the NADPH2 produced in the light reaction and produces NADP+. But if you were to turn off the Calvin cycle you would have no free NADP+, and hence you will be unable to keep the light reactions going.
I hope this clarifies the issue.
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