Global Warming’s Upsides…

How come plants produce oxygen even though they need oxygen for respiration?

Question Date: 2012-03-08

By using the energy of sunlight, plants can convert carbon dioxide and water into carbohydrates and oxygen in a process called photosynthesis. As photosynthesis requires sunlight, this process only happens during the day. We often like to think of this as plants `breathing in carbon dioxide and `breathing out oxygen. However, the process is not exactly this simple. Just like animals, plants need to break down carbohydrates into energy. Oxygen is required to do this. Then why do the plants get rid of all the oxygen they produce during photosynthesis? The answer is, they do not.Plants actually hold on to a small amount of the oxygen they produced in photosynthesis and use that oxygen to break down carbohydrates to give them energy.

But what happens at night when there is no sunlight which is needed in photosynthesis? Interestingly, in order to maintain their metabolism and continue respiration at night, plants must absorb oxygen from the air and give off carbon dioxide (which is exactly what animals do). Fortunately for all of us oxygen breathers, plants produce approximately ten times more oxygen during the day that what they consume at night.