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If I am not mistaken the stomata are closed during the night. As a result I have a hard time to imagine how the plant can get the O2 it needs for respiration during the night. I thought the plant could produce the O2 internally through some chemical reaction. Such reaction might include splitting H2O absorbed through the roots in two. Or maybe the O2 diffuses well enough through the plant tissues.

How do plants get their O2 for respiration during the night?

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    $\begingroup$ Welcome to Biology.SE. I edited the question. Feel free to roll back if you don't like the edit. Here are a few notes on the format of your question. 1) Your title is too uninformative 2) You could use MathJax to write $O_2$ 3) No need to thank and sign at the end 4) Avoid double question marks. $\endgroup$
    – Remi.b
    Dec 14, 2015 at 18:59

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Not all plants have their stomata closed during the night. A notable exception are Crassulacean acid metabolism(CAM) plants that keep their stomata closed during the day and open it during the night. This is a common evolutionary strategy with Xerophytes.

There are also 2 other types of metabolic pathways namely C3 and C4. As a consequence we get what is called a C3 and C4 plant, which aptly represent the predominant metabolic pathway it employs.

Additionally plant cells, like all life, can produce energy without oxygen by Glycolysis. Furthermore, when stomata is closed, oxygen respiration is restricted, not blocked entirely. Finally it might be important to note that plant metabolism is reduced during the night.

Full disclosure, I am not a botanist. Please let me know if there are any glaring errors.

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The problem here lies in your assumption:

Stomata are closed during the night.

Despite the fact that most (C3) plants do indeed close their stomata during the night and open them when detect blue light in the morning, the stomata are not completely closed, that is, they are not closed to the point of not allowing any conductance.

According to Snyder (2003):

It is generally accepted that for C3 and C4 plants stomatal closure minimizes transpirational water loss (E) at night when there is no opportunity for carbon gain. However, there is increasing evidence that some species maintain substantial stomatal conductance (g) and E at night. Arabidopsis, Betula, Brassica, Chrysothamnus, Fraxinus, Picea, Rosa, Sarcobatus, and Tilia all have substantial night‐time g, based on gas exchange measurements.

Thus, these plants do absorb O2 at night.

Source:

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You are not wrong. Plants can use the oxygen obtained from the photolysis (light breaking) of water to drive cellular respiration. For every 1 $C_6H_{12}O_6$ (glucose) produced, 6 $CO_2$ and 12 $H_2O$ are consumed. In addition, 6 $H_2O$ and 6 $O_2$ are produced as well. But the primary way plants receive oxygen is the same way in which they receive carbon dioxide – through their stomata.

Photosynthesis

However, I do want to emphasize on Niobe's point of CAM plants. CAM plants have adapted to hot, arid conditions by closing their stomata during the day and opening them during the night to collect $CO_2$.

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  • $\begingroup$ "Plants use the oxygen obtained from the photolysis (light breaking) of water to drive cellular respiration." any reference? $\endgroup$ Dec 15, 2015 at 7:18
  • $\begingroup$ Well, plants provide oxygen as a byproduct of light-dependent reactions. Organisms, including photosynthetic organisms, use this oxygen as an oxidizing agent in cellular respiration. $\endgroup$
    – Sentient
    Dec 15, 2015 at 7:26
  • $\begingroup$ I would like to add that plants perform cellular respiration throughout the day and night; and the way they do it is by storing oxygen during the day. $\endgroup$
    – Sentient
    Dec 15, 2015 at 7:28
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    $\begingroup$ Plants lack proteins to accumulate oxygen. How are they supposed to "store oxygen during the day"? I'm not saying this is impossible, but the statement definitely requires a reference. $\endgroup$ Dec 15, 2015 at 8:39

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