Photosynthesis is the process by which green plants create energy from sunlight. It occurs at the cellular level in the leaves of plants and is the way in which they produce oxygen and carbohydrates. The oxygen is released into the atmosphere, and the carbohydrates, simple sugars, are used by the plant for growth. In order to carry out photosynthesis, green plants need several ingredients.
Chlorophyll, the pigment in plants that makes them green, is essential to the photosynthetic process. This chemical is produced naturally by all green plants and its role in photosynthesis is to absorb light. That light energy triggers the chemical reaction we know as photosynthesis.
The process cannot work without an energy input, and this comes from the sun. The sun starts the first reaction in photosynthesis, which is known as the light-dependent process. During this stage of photosynthesis, as the sunlight excites the chlorophyll, water is split into oxygen and hydrogen, and the oxygen is released into the atmosphere.
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As any gardener knows, plants take in water from the ground through their roots. The water travels up the stem of the plant through a complex transport system and arrives in the leaves, to be used as a raw material during photosynthesis.
This gas is abundantly available in the atmosphere around plants. Most plants have a protective waxy layer over their leaves, which prevents them from drying out. Normally, this would also prevent a gas such as carbon dioxide from entering the leaf. But the leaf also has special openings, called stomata, that allow the gas to enter the leaf’s cells. Once photosynthesis has taken place, the oxygen produced also leaves the cells via the stomata. Carbon dioxide is bonded with the hydrogen produced in the first light dependent process, to make carbohydrates.