Photosynthesis is an essential process of all life. Using products from the environment, plants fuel our atmosphere and provide our food. A simple chemical reaction that is believed to have begun by bacteria more than 2 million years ago makes life possible. Let's take a look at how a plant produces food.
Photosynthesis, as the name implies, is the use of light to synthesize a product. In the case of plants and algae, the light used is the energy of the sun, which creates food using carbon dioxide from the atmosphere and releasing oxygen in return. It is the process of survival.
In order for photosynthesis to occur, a plant needs light energy, water and carbon dioxide. Using these products, sugar is created, which in turn fuels all plant processes. Photosynthesis occurs primarily in the leaves, with virtually none occurring elsewhere within the plant. Gas exchange of carbon dioxide and oxygen occurs through stomata, or pores, on the underside of the leaves. The two-step process takes place in organelles of the plant called chloroplasts using chlorophyll.
Photosynthesis consists of a light reaction and a dark reaction. In the former, chemical energy is created by converting light energy. This chemical energy is stored within the plant as ATP (adenosine triphosphate). This is the energy of the plant. The light reaction naturally occurs during the day. The dark reaction is not light-dependent. Sugar is formed using carbon dioxide collected from the atmosphere, ATP and other chemical known as NADPH (nicotinamide adenine dinucleotide phosphate-oxidase).
Climatic pressures can affect photosynthesis, necessitating adaptations by plants in extreme environments. For example, desert plants must balance water loss and transpiration, or the evaporation of water from plants. Plants have evolved physiological strategies to overcome these stresses and continue photosynthesis. Desert plants keep their stomata closed during the hottest times of the day and open them at night for carbon dioxide exchange. The carbon dioxide is then stored in plant tissues, but in a different way so the light reaction still can occur and transpiration rates can be controlled. Closing the stomata results in less evaporation, which limits the amount of carbon dioxide a plant receives. With low carbon dioxide levels, photosynthesis cannot occur.
Photosynthesis, while not visible, is a vital process for the health of the planet. It releases oxygen into the atmosphere. The very air we breathe depends upon the sun, water and carbon dioxide.