Why do C4 plants use less water?

C4 plants are a type of plant that uses a unique photosynthetic pathway. This pathway allows them to use less water than other types of plants, making them well-suited for survival in arid environments. But why do C4 plants use less water? Let's explore the reasons.

C4 pathway

The C4 pathway gets its name from the first molecule that is produced during the process, a molecule containing four carbon atoms called oxaloacetate. Unlike other plants that use the C3 pathway, C4 plants have specialized anatomy that allows them to separate the initial steps of carbon fixation from the rest of the photosynthetic process. This separation helps the plant conserve water.

Water loss

One of the main ways in which C4 plants reduce water loss is by keeping their stomata closed for longer periods. Stomata are small pores on the surface of the plant leaves. They allow plants to take in carbon dioxide for photosynthesis, but they also allow water to escape. By keeping the stomata closed, C4 plants can reduce the amount of water that is lost through transpiration.

Efficiency

Another reason why C4 plants use less water is that the C4 pathway is more efficient at fixing carbon than the C3 pathway. This means that C4 plants can produce the same amount of organic matter with less water. This efficiency comes from the fact that C4 plants can concentrate carbon dioxide around the enzyme that fixes carbon, making the process more efficient. This means that C4 plants can grow faster and produce more biomass than C3 plants in water-stressed environments.

Evolution

It is believed that the C4 pathway evolved as a response to the decreasing levels of carbon dioxide in the atmosphere during the Oligocene and Miocene epochs (about 33 to 5.3 million years ago). As carbon dioxide levels decreased, C3 plants became less efficient at photosynthesis. The evolution of the C4 pathway allowed plants to adapt to this change and still thrive in the changing environment. This adaptation was particularly important in the evolution of grasses, which are the dominant type of plants in many arid and semi-arid environments.

Conclusion

In conclusion, C4 plants use less water because of their unique photosynthetic pathway, and this allows them to thrive in arid environments. The C4 pathway is more efficient at fixing carbon than the C3 pathway, which means that C4 plants can use less water to produce the same amount of organic matter. Additionally, keeping the stomata closed for longer periods helps reduce water loss through transpiration. The evolution of the C4 pathway was an important adaptation for plants that allowed them to survive in changing environments.