Why is thsi the answer to this question? In nature, during a 24-hour period, green plants?

Question

(1) carbon dioxide, only

(2) both carbon dioxide and oxygen

(3) oxygen, only

(4) neither carbon dioxide nor oxygen

The answer is 3 but why isn't it 1 or 4? The plants take in carbon dioxide for photosynthesis but they don't go through photosynthesis 24 hours so why isn't it 4?

Answer 1

Part of your question is missing. That is, "during a 24-hour period, green plants ... (do what/produce what/uptake what)?"

In general, plants take up carbon dioxide and produce oxygen during photosynthesis, and release carbon dioxide during transpiration (but not as much as was taken up during photosynthesis).

Read more about photorespiration here:

http://www.sciencedaily.com/releases/200...