C3 plants

Definition

C3 plants are a group of plants that utilize the C3 pathway for photosynthesis, where carbon dioxide is fixed into a three-carbon compound, 3-phosphoglycerate (3-PGA), during the Calvin cycle. This process is efficient under normal conditions but can lead to photorespiration under high temperatures and low carbon dioxide concentrations, making these plants less adaptable to certain environmental stresses compared to C4 and CAM plants.

5 Must Know Facts For Your Next Test

1. C3 plants make up about 85% of all plant species, including many important crops like wheat, rice, and soybeans.
2. The C3 pathway is most efficient in cool, moist environments with plenty of sunlight, where conditions favor normal photosynthesis.
3. During hot and dry conditions, C3 plants often experience increased rates of photorespiration, which can reduce their overall productivity.
4. Examples of C3 plants include broadleaf plants and many temperate grasses, which thrive in regions with moderate climates.
5. Climate change poses significant challenges for C3 plants, as rising temperatures and altered precipitation patterns can exacerbate photorespiration and limit their growth.

Review Questions

• How do the physiological characteristics of C3 plants affect their photosynthetic efficiency in varying environmental conditions?
  • C3 plants rely on the C3 pathway for photosynthesis, which works best in cool, moist environments. However, when temperatures rise or water becomes scarce, these plants face increased rates of photorespiration due to the inefficiency of RuBisCO when it reacts with oxygen instead of carbon dioxide. This means that while C3 plants are productive under optimal conditions, their efficiency significantly decreases under stress, leading to reduced growth and yield.
• Evaluate the advantages and disadvantages of C3 photosynthesis compared to C4 and CAM pathways in terms of adaptation to climate change.
  • C3 photosynthesis is generally less energy-efficient under high temperatures and drought conditions compared to C4 and CAM pathways. While C4 and CAM plants have adapted mechanisms to minimize photorespiration and optimize carbon fixation under stress, C3 plants are more vulnerable to climate change impacts like rising temperatures. This makes them less adaptable in increasingly challenging climates where water scarcity and heat stress are prevalent.
• Synthesize information about the role of photorespiration in C3 plants and its implications for agricultural practices in a changing climate.
  • Photorespiration in C3 plants occurs when RuBisCO oxygenates RuBP instead of carboxylating it, leading to a loss of fixed carbon and decreased photosynthetic efficiency. This process has significant implications for agriculture, especially as climate change continues to alter growing conditions. Farmers may need to consider integrating C4 or CAM species into their cropping systems or employing agricultural practices that mitigate temperature increases and water stress to improve crop yields from C3 plants.

Related terms

Photorespiration: A process that occurs in C3 plants when the enzyme RuBisCO oxygenates RuBP, leading to a loss of fixed carbon and reduced photosynthetic efficiency.

C4 plants: Plants that have adapted a modified photosynthetic pathway to minimize photorespiration by initially fixing carbon dioxide into a four-carbon compound before it enters the Calvin cycle.

CAM plants: Plants that utilize Crassulacean Acid Metabolism (CAM) to fix carbon dioxide at night, allowing them to conserve water and reduce photorespiration during the day.