C4 Photosynthesis

Definition

C4 photosynthesis is a metabolic pathway that enables plants to efficiently fix carbon dioxide in warm and dry environments, reducing photorespiration and improving water-use efficiency. This process is especially significant in tropical and subtropical regions, where it allows certain plants, such as maize and sugarcane, to thrive under high temperatures and light intensity.

5 Must Know Facts For Your Next Test

1. C4 photosynthesis involves two distinct stages: the initial fixation of carbon dioxide into a four-carbon compound in mesophyll cells, followed by the conversion of this compound into sugars in bundle-sheath cells.
2. This adaptation allows C4 plants to concentrate carbon dioxide around the enzyme RuBisCO, reducing the likelihood of photorespiration and increasing photosynthetic efficiency.
3. C4 plants are typically more drought-resistant compared to C3 plants because they can maintain higher rates of photosynthesis even under water-stressed conditions.
4. The evolution of C4 photosynthesis is thought to have occurred independently in over 60 different plant lineages, showcasing its adaptive significance across diverse environments.
5. The prevalence of C4 plants has contributed to the expansion of grasslands and savannas during the Neogene period, influencing global carbon cycling and ecosystem dynamics.

Review Questions

• How does C4 photosynthesis improve the efficiency of carbon fixation in comparison to C3 photosynthesis?
  • C4 photosynthesis improves carbon fixation efficiency by first converting carbon dioxide into a four-carbon compound, which is then transported to bundle-sheath cells where it is converted into sugars. This mechanism minimizes photorespiration, a common issue in C3 plants where oxygen competes with carbon dioxide for RuBisCO. By concentrating CO2 around RuBisCO, C4 plants can maintain high rates of photosynthesis even under high temperatures and low water availability.
• Discuss the ecological implications of C4 photosynthesis during the Neogene period and its impact on global vegetation patterns.
  • During the Neogene period, the rise of C4 photosynthesis significantly influenced global vegetation patterns by allowing grasses to dominate warmer climates and drier environments. The adaptability of C4 plants contributed to the expansion of grasslands and savannas, reshaping ecosystems and providing new habitats for various species. This shift not only affected plant communities but also had cascading effects on herbivore populations and overall biodiversity.
• Evaluate the role of C4 photosynthesis in shaping agricultural practices today and its potential in addressing climate change challenges.
  • C4 photosynthesis plays a crucial role in modern agriculture by enhancing crop yields under challenging conditions such as high temperatures and limited water availability. Crops like maize and sugarcane exemplify this efficiency, providing significant food resources while minimizing environmental stress. As climate change continues to impact global agriculture, understanding and harnessing the mechanisms of C4 photosynthesis could be pivotal in developing resilient crop varieties capable of sustaining productivity in increasingly challenging climates.

Related terms

Calvin Cycle: The series of biochemical reactions in plants that convert carbon dioxide into glucose, occurring after the initial carbon fixation in photosynthesis.

Photorespiration: A process in which plants use oxygen instead of carbon dioxide for photosynthesis, leading to a decrease in overall productivity.

CAM Photosynthesis: Crassulacean Acid Metabolism, a type of photosynthesis that occurs in some plants that open their stomata at night to minimize water loss.