Plants make their own food by photosynthesis. But they also use aerobic respiration to release energy from it.
Now just a quick test for you. Respiration is the process of releasing energy from food molecules, like glucose.
Drag and drop the boxes to complete the equation:
Animals breathe, plants don't. So how can the plant get oxygen?
Oxygen from the air is able to diffuse into the leaves of plants through tiny air-holes called stomata. This is obvious in plants as they take in oxygen at night-time and give out the carbon dioxide produced by respiration.
But what happens during daytime, when photosynthesis is also happening?
Look back at the equation for respiration. How does it compare with the formula for photosynthesis?
Aerobic respiration occurs in the opposite direction as photosynthesis. So in plants, photosynthesis is building up sugars at the same time as respiration is using them up.
During the daytime photosynthesis occurs more quickly than does respiration. However, during the night photosynthesis stops and respiration carries on.
Therefore during the day, plant cells can use some of the oxygen produced by photosynthesis for respiration.