C4 plants

Definition

C4 plants are a group of plants that utilize a specialized photosynthetic pathway to efficiently fix carbon dioxide, allowing them to thrive in environments with high temperatures and low atmospheric CO2. This process involves an additional step that captures carbon in the form of a four-carbon compound before it enters the Calvin cycle, making these plants highly efficient at photosynthesis in conditions where other plants might struggle.

5 Must Know Facts For Your Next Test

1. C4 plants have adaptations such as specialized leaf anatomy, including bundle sheath cells, which help concentrate CO2 around RuBisCO for more efficient photosynthesis.
2. Common examples of C4 plants include maize (corn), sugarcane, and sorghum, which are often found in tropical and subtropical regions.
3. The C4 pathway enables these plants to photosynthesize efficiently at higher temperatures and lower humidity levels compared to C3 plants.
4. C4 photosynthesis helps reduce photorespiration by minimizing the oxygenation reaction of RuBisCO, allowing for greater productivity under stress conditions.
5. This photosynthetic pathway can contribute to increased biomass and yield in agricultural crops, making C4 plants important for food production.

Review Questions

• How do C4 plants enhance their efficiency in photosynthesis compared to C3 plants?
  • C4 plants enhance their photosynthetic efficiency by utilizing a specialized pathway that captures carbon dioxide as a four-carbon compound before it enters the Calvin cycle. This process reduces the occurrence of photorespiration, which is common in C3 plants. By concentrating CO2 in bundle sheath cells and having adaptations that allow them to thrive in hot and arid conditions, C4 plants can maximize their productivity even when environmental conditions are less than ideal.
• Discuss the anatomical features that distinguish C4 plants from C3 plants and their roles in the photosynthetic process.
  • C4 plants have distinct anatomical features, such as Kranz anatomy, where bundle sheath cells surround vascular bundles. This arrangement allows for the spatial separation of the initial carbon fixation process from the Calvin cycle. The enzyme PEP carboxylase captures CO2 initially and converts it into a four-carbon compound. This compound is then transported to the bundle sheath cells where it is converted back into CO2 for use in the Calvin cycle. These adaptations help C4 plants reduce photorespiration and increase overall efficiency in capturing light energy.
• Evaluate the ecological significance of C4 plants in relation to global climate change and agricultural practices.
  • The ecological significance of C4 plants lies in their ability to thrive in warmer climates and their potential to contribute to food security as global temperatures rise due to climate change. Their efficiency in water use and photosynthesis makes them excellent candidates for sustainable agriculture practices, especially in regions facing drought conditions. As these plants can maintain high productivity while minimizing water loss, incorporating C4 crops into agricultural systems could help mitigate some impacts of climate change and support higher yields under stress conditions.

Related terms

Calvin Cycle:

The series of biochemical reactions that take place in the stroma of chloroplasts, where carbon fixation occurs, and energy from ATP and NADPH is used to produce glucose.

Photorespiration: A process that occurs when the enzyme RuBisCO oxygenates RuBP, leading to a wasteful pathway that reduces the efficiency of photosynthesis, especially in C3 plants.

CAM plants: Plants that utilize Crassulacean Acid Metabolism (CAM) to fix carbon dioxide at night, allowing them to minimize water loss during hot, dry days.