Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It only takes a minute to sign up.
Sign up to join this community
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?
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.
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:
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.
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 $CO_2$.
Yes,each one of you are correct as there are many ways in which plant can get O2 as plants respire not only by leaves but also by stems and roots which help it to get oxygen present in soil and near surface,and other than that they have photolysis.
