Chlorophyll, the pigment that makes plants green, is the starter engine for photosynthesis, the process plants use to make food. Chlorophyll absorbs sunlight, converting it from solar energy to chemical energy. The plant also draws components for the food-making process by taking in water and nutrients through its roots and absorbing carbon dioxide through the leaves. Plants don't use all the food they make, which allows them to be a food source for other living things.
When a photon of light strikes a chlorophyll molecule, it starts a process that splits water molecules. This gives off oxygen for us to breathe and creates ATP, a compound that includes ribose (a sugar), phosphates and the nitrogen compound adenine. ATP is a high-energy compound, providing energy when a phosphate is removed. Hydrogen freed from the split water compound is transported for further use.
Sugars Are Formed
Using carbon dioxide, the ATP and hydrogen produce glucose, another sugar, and water. The sugar gets transported from cells in the plant's leaves to other parts of the plant where it is stored (in fruits, tubers and roots) or modified into either starch, fat or protein through the action of enzymes, which are complex protein molecules.
Carbohydrates are Formed
When the simple sugars are changed to carbohydrates, the result is starch, cellulose and other more complex sugars like sucrose. Carbohydrates are made of carbon, hydrogen and oxygen. Cellulose is a chain of glucose molecules that form fibrous bundles that the plant uses to build stems and leaves. Sucrose is used by the plant to transport simple sugars throughout the plant.
Fats are also made of carbon, hydrogen and oxygen, but there is more hydrogen in proportion to oxygen.They provide more energy than carbohydrates, so it makes sense that nuts and seeds are often rich in fat and oil, along with protein, since a new plant must grow from a seed, using its stores to grow until it can gather light and grow roots.
Elements Also Needed
Plants need 16 elements to grow. Air and water supply the carbon, hydrogen and oxygen, but the others must come from the ground where roots collect them so the plant can incorporate them into its life processes and structure.
When we fertilize plants, we are not actually feeding them. We are making it easier for roots to collect these elements. For instance, nitrogen doesn't occur naturally in soil but comes from the decomposition of living matter. Thus fertilizer formulas often contain nitrogen.