In the 1600s, the Belgian physician Jan van Helmont devised an experiment to find out if plants grew by taking material out of the soil. Van Helmont determined the mass of a pot of dry soil and a small seedling. Then, he planted the seedling in the pot of soil. He watered it regularly. At the end of five years, the seedling, which by then had grown into a small tree, had gained about 75 kg. The mass of the soil, however, was almost unchanged.

He concluded that “164 pounds of wood, barks, and roots arose out of water only,” because that was the only thing that he had added. Obviously, he knew nothing of photosynthesis, in which carbon from the air, water, and minerals from the soil are used to generate new plant tissue with the presence of sunlight.

Although van Helmont did not realize it, carbon dioxide in the air made a major contribution to the mass of his tree. The carbon in carbon dioxide is used to make sugars and other carbohydrates in photosynthesis. Moreover, he could not grasp the role minerals and sunlight play in photosynthesis. Van Helmont had only part of the story, but he made a major contribution to science. Now, photosynthesis is one of the basic facts in biology, which is defined as the process during which light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds. It helps plants make their own food to survive and grow. Plants not only make their own food, but also provide all the other living creatures with the fuel they need to live.