system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If plants create oxygen with energy they get from the sun, how do they make oxygen or get energy when the sun is not out?
gpt
In short, they don’t.

During the day plants combine carbon dioxide and water to make carbohydrates (oxygen is a byproduct of this), some of which are burned then for energy and some of which are stored (in sap etc.) or used for growth.

During the night, most plants don’t do much growing, and use the stored carbs to keep themselves ticking over. During this time they use more oxygen than they are producing.