Photosynthesis is used by most if not all plants. It takes carbon dioxide which it takes in through pores in the cell called stomata. Water which is absorbed by the roots of the plants and travels up the stem in to the leaves. And the sunlight factor is absorbed by the leaves. The reason this occurs is so that can make glucose to make ATP to build new cells and proteins. There is also oxygen which is a waste product the plant has no use for it and we use it to live and respiration occurs which gives plants CO2 so it's just a cycle.

Photosynthesis