Microscopic examination of a leaf’s surface reveals stomata, pores that allow the entry and the exit of gases. Type into your browser: leaf stomata images
Also examine the internal structure of a leaf. Note considerable amount of air space between upper and lower surfaces. Type into you browser: leaf cross section illustration
Discuss: How does the structure of a leaf facilitate taking in carbon dioxide and exiting oxygen?
Observations and experiments in from Van Helmont’s time on prove that plants obtain the bulk of their mass from carbon dioxide and water. We now know this as photosynthesis. Light energy promotes the reaction