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What Do Plants Need for Photosynthesis?

By Dawn Walls-Thumma ; Updated September 21, 2017
During photosynthesis, plants convert energy from the sun into usable chemical energy.

Photosynthesis is the process by which plants convert light from the sun into chemical energy that aids in their own growth and provides nutrients to other organisms that consume them. The process of photosynthesis is essential to life on Earth by making the sun's energy available to living organisms. Photosynthesis is a chemical reaction and requires certain chemical reactants as well as leaf structures that enable the necessary reactions to occur. (See References 1)


Water enters the plant through absorption by the roots. During the process of photosynthesis, the water molecule is broken into hydrogen and oxygen. The hydrogen atoms are used to form a carrier molecule called NADPH that, later in the photosynthesis process, is broken down to form glucose, a sugar that organisms commonly use for energy. The oxygen from the water is released into the atmosphere, where it becomes available to animals to use for respiration. (See References 2) The role of water in the photosynthesis process illustrates why plants are essential to life on Earth. Not only do they release oxygen to breathe, but the glucose that water helps to produce nourishes animals that will feed on the plant.

Carbon Dioxide

Carbon dioxide enters the plant through structures in the leaves called stomata. Stomata act as gates for gases to pass in and out of the leaves. The oxygen released from water also passes through the stomata. Because plants can also lose water through their stomata, they have the ability to shut or open them, depending on whether the plant needs to exchange gases. During the photosynthesis reaction, the addition of hydrogen to the carbon dioxide molecule produces carbohydrates that can be used by the plant as energy. (See References 2)


Visible light is composed of a spectrum of colors ranging from red to violet. Colors vary according to the size of the light's wavelength. When a pigment absorbs light, several responses may occur, one of which is the start of a chemical reaction. When plants absorb light, the energy from the light triggers the chemical reaction of photosynthesis. (See References 2)


Chlorophyll is a pigment, or a substance that absorbs certain wavelengths of light. Chlorophyll gives plants their green coloration because it absorbs every wavelength of visible light except green. Because it reflects green light, plants appear green. All other wavelengths of light, when they strike the chlorophyll molecule, energize the molecule and start a chemical reaction. In plants, chlorophyll is contained in structures called chloroplasts that contribute additional proteins that interact with chlorophyll and help set off the photosynthesis reaction. (See References 2)


Enzymes function as catalysts in chemical reactions, meaning that they speed up chemical reactions. The process of converting light energy into oxygen and sugar is long and complex, and each chemical reaction in the process relies on a different enzyme to speed up the reaction and make photosynthesis efficient. (See References 2)