What are the importance of oxygen in plants?
Oxygen helps in the process of photosynthesis.
Not photosynthesis exactly, they also need to breathe. Photosynthesis needs carbon dioxide only.
Plants need oxygen for aerobic respiration. Although photosynthesis produces oxygen as a waste product, and this oxygen is used for aerobic respiration,
Photosynthetic plants breathe in carbon dioxide and breathe out oxygen. Oxygen is a product of photosynthesis.