What helps C4 plants avoid photorespiration?

C4 plants have developed a specialized mechanism to avoid photorespiration, which is a wasteful pathway that occurs when the enzyme Rubisco reacts with oxygen instead of carbon dioxide. This inefficiency can hinder photosynthesis, particularly in conditions where oxygen concentration is high or carbon dioxide concentration is low.

In C4 plants, carbon fixation occurs primarily in two types of cells: mesophyll cells and bundle sheath cells. The initial fixation of carbon dioxide is carried out by an enzyme called phosphoenolpyruvate carboxylase (PEP carboxylase) in the mesophyll cells, forming a four-carbon compound that is then transported to the bundle sheath cells. Within these bundle sheath cells, the four-carbon compound releases carbon dioxide, which is then used by Rubisco for the Calvin cycle. This compartmentalization effectively increases carbon dioxide concentration around Rubisco, minimizing the likelihood of Rubisco’s interaction with oxygen, hence reducing photorespiration.

This mechanism allows C4 plants to maintain higher levels of photosynthesis under conditions of stress, such as high temperatures and low water availability, where traditional C3 photosynthesis may fail. Therefore, the presence of bundle sheath cells with Rubisco is integral in enabling C4 plants to achieve more efficient photosynthesis and