C4 Photosynthesis

Definition

C4 photosynthesis is a specialized pathway used by certain plants to efficiently fix carbon dioxide, particularly in hot and dry environments. This process reduces photorespiration, a wasteful reaction that occurs in standard photosynthesis, by utilizing a unique mechanism that concentrates CO2 in bundle sheath cells, ensuring higher productivity under stress conditions.

5 Must Know Facts For Your Next Test

1. C4 photosynthesis involves two types of cells: mesophyll cells, which capture CO2, and bundle sheath cells, where the Calvin cycle occurs.
2. Plants using C4 photosynthesis include important crops such as maize, sugarcane, and sorghum, which thrive in warmer climates.
3. The C4 pathway requires additional energy in the form of ATP compared to C3 photosynthesis but offers advantages in water use efficiency and light saturation.
4. The adaptation of C4 photosynthesis allows these plants to minimize water loss and maximize carbon fixation during high temperatures and intense sunlight.
5. C4 photosynthesis evolved independently in several plant lineages as an adaptation to environmental stressors like drought and high temperatures.

Review Questions

• How does C4 photosynthesis reduce the effects of photorespiration compared to C3 photosynthesis?
  • C4 photosynthesis minimizes the effects of photorespiration by utilizing a unique mechanism that captures CO2 more efficiently. In C4 plants, CO2 is initially fixed into a four-carbon compound in mesophyll cells, which is then transported to bundle sheath cells where it is released for use in the Calvin cycle. This process effectively increases CO2 concentration around the enzyme RuBisCO, reducing its interaction with oxygen and thus decreasing photorespiration.
• Evaluate the advantages and disadvantages of C4 photosynthesis for plants living in arid environments.
  • C4 photosynthesis provides significant advantages for plants in arid environments by improving water use efficiency and enabling effective carbon fixation during high light conditions. However, it also comes with increased energy costs due to the additional ATP required for processing CO2. These plants can thrive under heat and drought stress, but their higher energy demands can be a disadvantage in nutrient-poor soils or less favorable conditions.
• Synthesize information from various studies on C4 photosynthesis to predict how climate change may impact C4 plant populations.
  • Climate change may affect C4 plant populations by altering temperature and precipitation patterns, potentially expanding their habitats into new regions. As temperatures rise and CO2 levels increase, C4 plants could benefit from their efficient carbon fixation capabilities. However, extreme weather events such as droughts or flooding could also challenge their survival. Studies suggest that understanding these dynamics will be essential for predicting shifts in agricultural productivity and biodiversity as global climates continue to change.

Related terms

Photorespiration: A process that occurs when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide, leading to the loss of energy and carbon in plants.

CAM Pathway: Crassulacean Acid Metabolism (CAM) is another adaptation found in some plants, allowing them to fix carbon at night to minimize water loss during the day.

Bundle Sheath Cells: Specialized cells in C4 plants where the CO2 is concentrated for the Calvin cycle, allowing for more efficient sugar production.