Introduction:

C4 plants are a group of plants that have evolved a unique mechanism for carbon fixation known as the C4 pathway. This mechanism allows them to overcome the limitations of traditional photosynthesis in high temperature and low water conditions. In this chapter, we will explore the C4 pathway, its mechanism, ecological significance, and examples of C4 plants.

C4 Pathway Mechanism:

• The C4 pathway involves a spatial separation of carbon dioxide fixation and the Calvin cycle. In this mechanism, carbon dioxide is first fixed into a four-carbon molecule called oxaloacetate in the mesophyll cells. This reaction is catalyzed by the enzyme PEP carboxylase, which has a higher affinity for carbon dioxide than rubisco, the enzyme responsible for carbon dioxide fixation in traditional photosynthesis.
• The four-carbon molecule is then transported to the bundle sheath cells, where it is converted back into carbon dioxide and enters the Calvin cycle. This allows the plant to carry out photosynthesis and produce glucose while minimizing water loss through transpiration.

Ecological Significance of the C4 Pathway:

• The C4 pathway provides several ecological advantages to plants in hot and dry environments. Firstly, it allows them to fix carbon dioxide with greater efficiency and at a higher rate than traditional photosynthesis. This allows them to produce more glucose per unit of carbon dioxide and water, increasing their water use efficiency.
• Secondly, the spatial separation of carbon dioxide fixation and the Calvin cycle allows the plant to concentrate carbon dioxide in the bundle sheath cells, reducing its concentration in the mesophyll cells and minimizing photorespiration. Photorespiration is a process that occurs in traditional photosynthesis when rubisco binds with oxygen instead of carbon dioxide, reducing the efficiency of photosynthesis and increasing water loss through transpiration.

Examples of C4 Plants:

C4 plants are found in many different plant families, including grasses, sedges, and succulents. Some examples of C4 plants include corn, sorghum, sugarcane, and switchgrass. These plants are able to grow in hot and dry environments, making them important crops in regions with low water availability.

Conclusion:

The C4 pathway is a unique mechanism for carbon fixation in plants that allows them to overcome the limitations of traditional photosynthesis in hot and dry environments. The spatial separation of carbon dioxide fixation and the Calvin cycle allows the plant to fix carbon dioxide more efficiently, increasing water use efficiency and reducing photorespiration. Examples of C4 plants include corn, sorghum, sugarcane, and switchgrass. Understanding the C4 pathway is important for managing and conserving plant species in hot and dry environments and for increasing agricultural productivity in these regions.