Photosynthesis is the key to plant life and tree life. Water,sunlight and Co2 is the ingredients to make food that the plant and tree uses to grow and thrive.
To understand what plants do to grow is how gardeners can grow plants better. Monitoring your gardens intake on water, sunlight, and carbon dioxide can improve the plants growth. Giving the plant not enough supplies can have the plant stop growing and can even die. Giving the plant to much supplies can have the plant swell and drown the plant in water.
Plants also have different types of limits of supplies. So always research your plant to see their necessity for photosynthesis.