Photosynthesis is not an immediate process. The entire chain of events will not occur as soon as the sunlight hits the leaves. Some of it will actually occur in darkness when there is no visible sunlight. Photosynthesis is split into two separate parts referred to light dependent and light independent reactions. The light dependent reaction happens when sunlight is captured and used to begin the process, resulting in the creation of a molecule known as ATP. ATP is a free energy containing molecule and is produced through a chain of steps starting when chlorophyll absorbs light energy. The light independent reaction creates glucose through the Calvin cycle, which uses the ATP and carbon dioxide to make sugar. Dark or light independent reactions occur in the stroma of the plant.
Photosynthesis and all associated reactions take place at the molecular level. These microscopic reactions involve several molecules aside from chlorophyll. Some of the other molecules are water (H2O), carbon dioxide (CO2), oxygen (O2), and glucose (C6H12O6). All of the components are necessary and the absence of any one of them causes the entire process to fail. For example, if there is no water available to the plant roots, they will begin to turn brown and die, effectively stopping photosynthesis. Oxygen and glucose are not used in photosynthesis, but are byproducts of the reaction. Oxygen is released into the air, and glucose is stored inside the plant cells.
It is evident from these absorption and output plots that only the red and blue ends of the part of the are used by plants in photosynthesis. The reflection and transmission of the middle of the spectrum gives the leaves their green visual color.
In leafy plants, the process of photosynthesis occurs largely in the leaves. Because of this, all the necessary ingredients need to be present in the leaves for the reaction to take place. Carbon dioxide is absorbed into the leaves from the air, water is routed from the roots to the leaves, and sunlight is absorbed into the leaves through chlorophyll. Chlorophyll is a green pigment inside plant cells called chloroplasts - which also have several other structures within them. Chloroplasts are important because they are where photosynthesis takes place.