How does carbon dioxide from respiration diffuse out of the leaf during the night?

Do stomata close completely during night?

  • $\begingroup$ Salt water macro algae ( calurpa ) discharge CO2 at night , but I don't know if it is from stomata. I had a 75 salt tank with a lot of calurpa and few fish ; the pH would drop impressively each night considering the high buffering capacity. as I remember 8.7 to 8.3. $\endgroup$ Aug 4, 2021 at 18:04

3 Answers 3


Land plants might do better to keep their CO2 to use in the morning, unless they produce way too much of it.

CO2 is present in air at concentration around 0.03%. (In recent years it's gone up to 0.04%.) That's a low concentration to work against.

Remember, in the daytime those plants are sending water vapor and O2 OUT the stomata. It's a pressure gradient. Why let CO2 out at night and then depend on it coming IN against the flow the next day?

Plants have ways to grab onto CO2 so it won't just drift away. They convert it to things that aren't gases -- oxaloacetic acid or malate, or 3-phosphoglycerate, or possibly others that haven't been noticed yet.

These compounds can be stored. Then restore the CO2 precisely when and where it is needed.

Some CO2 gets this treatment at the roots (where CO2 concentration can sometimes be as high as 8%) and the storage compounds then get sent toward the leaves along with water and minerals.

CO2 from roots


Leaves have no need to 'exhale' carbon dioxide - it gets consumed by photosynthesis.

Elsewhere in the plant, metabolic processes produce carbon dioxide. This escapes via inter-cellular gas channels that, in woody plants, terminate as lenticels (little pores) on the stem surface. Oxygen for metabolism diffuses into the plant in the same inter-cellular spaces as carbon dioxide diffuses out.

With roots, the oxygen necessary for metabolic processes is dissolved in water.

If you've meant to ask about leaf adsorption of carbon dioxide and when stomata close, it depends on what carbon fixation scheme the plant exhibits, CAM, C4, or C3.

You might want to also consult an answer I gave to a similar question previously posed here.

  • $\begingroup$ +1 just for mentioning carbon fixation schemes which will each asnwer this very differently.. $\endgroup$
    – John
    Nov 18, 2017 at 6:17
  • $\begingroup$ OP is asking about the fate of CO2 at night, when the stomata are closed and there is no CO2 fixation. $\endgroup$
    – user24284
    Nov 18, 2017 at 8:06
  • $\begingroup$ I think your answer is quite good, but could use some expansion - what happens during the night with CAM, C4 or C3? And how do these affect carbon dioxide diffusion, and respiration? Further, how much respiration is occurring at night? $\endgroup$ Nov 22, 2017 at 15:24
  • 1
    $\begingroup$ Okay, @GrumpyMammoth, I added a link to a prior similar question that I answered. My original answer to this question included links to' lenticels' and 'carbons fixation'. The Wikipedia articles explain those two aspects of plant function in good enough detail, IMO. $\endgroup$
    – user24965
    Dec 19, 2017 at 6:56

Carbon dioxide is gas and can easily diffuse out through epidermal cell following concentration gradient. As during night respiration is going on, lot of Carbon dioxide accumulates inside leaf to form a concentration gradient which is sufficient to cause diffusion.


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