How do C4 plants perform photosynthesis differently from C3 plants?

C4 plants perform photosynthesis differently from C3 plants by using a two-step process to concentrate CO2 in specialised cells.

C3 and C4 plants both perform photosynthesis, but they do it in slightly different ways due to their adaptations to different environments. C3 plants, which include most types of plants, use a process called the Calvin cycle to convert carbon dioxide (CO2) into glucose. This process is efficient but has a downside: when the weather is hot and dry, C3 plants lose a lot of water through their stomata (the tiny pores in leaves that allow CO2 in and water out).

C4 plants, on the other hand, have developed a clever way to minimise this water loss. They use a two-step process to concentrate CO2 in specialised cells deep in their leaves, away from the air and the drying effects of the sun. This process is known as C4 photosynthesis.

In the first step, C4 plants capture CO2 in the mesophyll cells, the cells in the middle of the leaf. Here, the CO2 is combined with a three-carbon compound to form a four-carbon compound (hence the name 'C4'). This four-carbon compound is then shuttled to specialised cells called bundle sheath cells, which are located deep in the leaf, away from the air.

In the second step, the four-carbon compound releases its CO2 within the bundle sheath cells. Because these cells are deep in the leaf, they are not exposed to the air and therefore do not lose water. The CO2 is then used in the Calvin cycle to produce glucose, just like in C3 plants.

This two-step process allows C4 plants to keep their stomata closed more of the time, which reduces water loss. It also allows them to capture CO2 more efficiently, which is particularly useful in hot, dry environments where CO2 is often in short supply. This is why many C4 plants, such as maize and sugarcane, are able to thrive in conditions that would be challenging for C3 plants.