CAM vs C4

Definition

CAM (Crassulacean Acid Metabolism) and C4 pathways are two distinct mechanisms of carbon fixation used by plants to efficiently capture carbon dioxide, particularly in environments with limited water or high temperatures. Both pathways allow plants to reduce photorespiration and enhance photosynthetic efficiency but operate under different conditions and processes. While C4 plants capture CO2 in a spatially separated manner within different cell types, CAM plants do so temporally, taking in CO2 at night to minimize water loss during the hot daytime hours.

5 Must Know Facts For Your Next Test

1. C4 plants typically thrive in hot, sunny environments, while CAM plants are adapted to extremely arid conditions.
2. In C4 photosynthesis, the initial fixation of CO2 occurs in mesophyll cells, converting it into a four-carbon compound before it enters the Calvin cycle in bundle sheath cells.
3. CAM plants open their stomata at night to fix CO2, storing it as malate for use during the day when stomata are closed to conserve water.
4. Both pathways help minimize water loss compared to traditional C3 photosynthesis by reducing the exposure of stomata to high daytime temperatures.
5. Common examples of C4 plants include maize and sugarcane, while examples of CAM plants include succulents like cacti and some orchids.

Review Questions

• How do the mechanisms of carbon fixation differ between CAM and C4 plants?
  • The primary difference between CAM and C4 plants lies in how they fix carbon dioxide. C4 plants separate the initial carbon fixation from the Calvin cycle spatially; they first convert CO2 into a four-carbon compound in mesophyll cells before it is transferred to bundle sheath cells for further processing. In contrast, CAM plants fix CO2 at night when their stomata are open and store it as malate, which is then utilized during the day when stomata are closed. This adaptation allows CAM plants to thrive in dry conditions while minimizing water loss.
• Discuss how environmental conditions influence the evolution of CAM and C4 pathways in plants.
  • Environmental factors such as temperature and water availability significantly influence whether a plant utilizes CAM or C4 pathways. C4 photosynthesis is favored in hot and sunny environments where high light intensity can be utilized for photosynthesis without excessive water loss. On the other hand, CAM is advantageous for plants in arid climates where water conservation is critical; by fixing CO2 at night, these plants avoid losing water during the hotter daytime hours. The evolution of these pathways is a response to these specific environmental pressures, allowing plants to optimize their photosynthetic efficiency while managing resource limitations.
• Evaluate the ecological significance of CAM and C4 pathways in terms of plant adaptation and survival in changing climates.
  • The ecological significance of CAM and C4 pathways becomes increasingly relevant as climate change leads to rising temperatures and altered precipitation patterns. Plants utilizing these pathways demonstrate enhanced adaptation strategies that allow them to survive in stress-prone environments. By minimizing water loss and improving carbon fixation efficiency, both types of plants play crucial roles in ecosystems by contributing to biomass production and carbon cycling. As global climate conditions become more extreme, understanding these adaptations can help inform conservation efforts and agricultural practices aimed at improving resilience and sustainability.

Related terms

Photorespiration:

A process in plants where oxygen is taken up and carbon dioxide is released, which can reduce the efficiency of photosynthesis.

Stomata: Small openings on plant leaves that regulate gas exchange, including the intake of CO2 and the release of O2 and water vapor.

Mesophyll Cells: Cells in leaves where photosynthesis occurs; in C4 plants, these cells are involved in the initial fixation of CO2.