Understanding the Difference Between C₃, C₄, and CAM Pathway
Photosynthesis is the fundamental process by which plants convert sunlight into energy. However, different plants have adapted unique carbon fixation pathways to optimize this process under varying environmental conditions. These pathways—C₃, C₄, and CAM—help plants minimise photorespiration, enhance water efficiency, and maximise growth. Understanding their differences is crucial for studying plant adaptations, especially in the face of climate change.
What are the Differences Between C₃, C₄, and CAM Pathway
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FAQs on C₃ vs C₄ Vs CAM: Key Distinctions in Photosynthesis
1. What is the main difference between C₃, C₄, and CAM pathways?
The primary difference lies in how these pathways fix carbon dioxide. C₃ plants directly fix CO₂ into a three-carbon compound (3-PGA), C₄ plants fix CO₂ into a four-carbon compound (oxaloacetate) to reduce photorespiration, and CAM plants store CO₂ at night and use it during the day to conserve water.
2. Why do C₃ plants experience higher photorespiration?
C₃ plants have no adaptations to prevent RuBisCO from binding with oxygen instead of CO₂, leading to higher photorespiration, especially in hot and dry conditions.
3. Which plants use the C₃ pathway?
C₃ plants include major crops like wheat, rice, barley, and soybean, as well as most trees and shrubs.
4. How does the C₄ pathway help plants survive in hot climates?
C₄ plants, such as maize and sugarcane, separate carbon fixation and the Calvin cycle into different cells (mesophyll and bundle sheath cells), reducing photorespiration and increasing water-use efficiency in high temperatures.
5. What is the distinguishing difference between C₃, C₄, and CAM pathways?
The key distinguishing difference is how each pathway fixes carbon. C₃ plants produce a three-carbon compound directly in the Calvin cycle, C₄ plants create a four-carbon intermediate to reduce photorespiration, and CAM plants fix carbon dioxide at night to conserve water in dry environments.
6. How can we distinguish the difference between C₃ and C₄ plants based on photorespiration?
C₃ plants have high photorespiration due to RuBisCO binding with oxygen, while C₄ plants have low photorespiration because carbon fixation and the Calvin cycle occur in separate cells, reducing oxygen interference.
7. What is the distinguishing factor that makes CAM plants more water-efficient than C₃ and C₄ plants?
CAM plants open their stomata at night to take in CO₂, storing it as malic acid, which is used for photosynthesis during the day. This prevents water loss, making them more water-efficient than C₃ and C₄ plants.
8. How do we distinguish between C₃ and C₄ plants in terms of their first stable product?
C₃ plants form a three-carbon compound (3-PGA), while C₄ plants produce a four-carbon compound (oxaloacetate) as the first stable product.
9. What is the distinguishing difference in stomatal activity among C₃, C₄, and CAM plants?
C₃ plants: Stomata are open during the day.
C₄ plants: Stomata are partially open during the day.
CAM plants: Stomata are open at night and closed during the day to prevent water loss.
10. How do the distinguishing differences in temperature preferences affect C₃, C₄, and CAM plants?
C₃ plants thrive in cool to moderate temperatures (15–25°C), C₄ plants prefer warm temperatures (30–40°C), and CAM plants excel in hot and arid conditions (35–45°C).
