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Photorespiration

Definition

noun

(1) The process by which in the presence of light plant consumes oxygen and releases carbon dioxide (in stead of fixing carbon dioxide) during photosynthesis, resulting in a decrease in photosynthetic output since no ATP is produced and carbon (as well as nitrogen in the form of ammonia) is lost inevitably.

(2) An alternative counter-productive metabolic pathway wherein oxygen molecule is fixed rather than carbon dioxide to produce glyceraldehyde 3-phosphate (G3P).


Supplement

Plants, especially C3 plants, face the problem of photorespiration. In hot dry days, these plants tend to close their stomata to prevent excessive loss of water (from transpiration). Inevitably, the carbon dioxide cannot enter the leaves (via the stomata) resulting in the levels of carbon dioxide within the leaves to become low. Since there are few carbon dioxide molecules to fix, the oxygen molecules are used as a substitute to produce G3P. Because of photorespiration, in stead of about 2 molecules of G3P, only one G3P is produced and a toxic phosphoglycolate (which the plant must get rid of) is also formed. Some plants such as CAM plants and C4 plants have evolved mechanisms to avoid photorespiration.


Word origin: photo (light) + respiration


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Re: Transpiration Please help Me

... plant (due to the splitting of water during photosynthesis) the photosynthetic rate decreases until it completely ceases through a process called photorespiration. This is due, in part, to the fact that RuBisCo (the enzyme responsible for the first step in carbon fixation) also fixes oxygen. The ...

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by daddyjames
Sun Oct 14, 2012 2:34 pm
 
Forum: Botany Discussion
Topic: Transpiration Please help Me
Replies: 29
Views: 28225

Photorespiration

When plants are in hot environments they'll close stomata to prevent water loss. This closing of stomata leads to low levels of CO2 which leads to photorespiration. But where is the oxygen coming from for photorespiration? In my textbook it says that it is coming from photolysis during the light-dependent ...

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by SheffJoe
Wed May 16, 2012 11:14 am
 
Forum: Botany Discussion
Topic: Photorespiration
Replies: 3
Views: 3708

is the CO2 produced by photorespiration...

is the CO2 produced by photorespiration go to the calvin cycle? (the calvin cycle input) Thanks!

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by rchow202
Tue Dec 06, 2011 1:03 am
 
Forum: Botany Discussion
Topic: is the CO2 produced by photorespiration...
Replies: 2
Views: 2242

Can anyone help me think of a project?

Are you sure you know what photorespiration is? I only ask because I never learned about it in school (unless school means someting other than graad 1-12.) It is the chain of reactions that recycle the carbon lost to the calvin cycle by ...

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by Marnitz
Sat Jun 11, 2011 4:44 pm
 
Forum: Botany Discussion
Topic: Can anyone help me think of a project?
Replies: 9
Views: 5526

Re: Can anyone help me think of a project?

Do you like to study photorespiration of plants under stress conditions? Say under the stress of added Cr in the soil? May see this link. http://knol.google.com/k/suvarna/chromium-uptake-by-fenugreek/3ecxygf1lxcn2/42?collectionId=3ecxygf1lxcn2.14# ...

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by DMRSekhar
Thu Jun 02, 2011 8:37 am
 
Forum: Botany Discussion
Topic: Can anyone help me think of a project?
Replies: 9
Views: 5526
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