Photosynthesis Definition

by Laurent Cousineau

Photosynthesis is an endergonic (energy requiring) process by which plants take in water, minerals, and carbon dioxide from the air (or bicarbonate in water) to form carbohydrates, releasing oxygen (O2) in the process.

There are several different pathways of photosynthesis with different responses to atmospheric CO2 concentrations.

Also, the concentration of CO2 in the atmosphere changes with the seasons. This is because at winter, when plants die, CO2 is released back into the atmosphere

More specifically, there are more plants in the Northern Hemisphere than in the Southern Hemisphere. Hence, when it is winter in the Northern Hemisphere, there is more carbon dioxide overall in the atmosphere.

Photosynthesis and Climate Change

Rising surface temperatures will cause the pores of plants, known as stomata, to close. In turn, this restricts the amount of carbon dioxide that plants could absorb through their leaves.

Therefore, these plants will produce less oxygen than they would in standard temperatures. As a result, the amount of oxygen available to humans and other mammals will decrease as well.


During the photosynthesis process, plants use water (H2O).

However, the pores of plants close even more when the temperature is hot and arid. Hence, plants will take in less water during these conditions.

Less water being taken in by plants means that less oxygen will be produced. Also, plants will eventually die due to the lack of water.

Carbon Dioxide Increase

Since plants will not convert as much carbon dioxide into oxygen, the amount of carbon dioxide in the atmosphere will start to increase.

In turn, this will prevent the heat from the sun (infrared radiation) from reflecting off the Earth's surface and escaping back into space.

This is known as the greenhouse effect. Essentially, global average temperature will begin to rise dramatically.


Global warming will restrict the amount of rainfall in certain areas around the world (it will also cause floods in others).

As mentioned before, plants require water during the photosynthesis process. Without this water, these plants will eventually die.

Moreover, drought will also prevents plants from producing crops, and the amount of food available to mammals will decrease consequently.

As temperatures increase, the polar caps will melt.

This will cause water levels to rise around the world, flooding several different areas.

Soil will then collect more water than it will be able to contain which will thus rot the roots of plants, thereby disrupting photosynthesis.


Photo comes from the Greek word φώτο- which means "light."
Synthesis comes from another Greek word σύνθεσις which signifies "putting together", "composition."

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