Table of contents | |
C₃ Pathway | |
C₄ Pathway | |
CAM Pathway | |
Difference Between C₃, C₄, and CAM Pathway |
Note: It's worth noting that C₃ plants have their origins dating back to the Paleozoic and Mesozoic eras and precede the evolution of C₄ plants. These C₃ plants account for nearly 95 percent of the plant biomass on Earth, including essential food crops like rice, soybeans, wheat, and barley.
The Crassulacean Acid Metabolism, or CAM pathway, represents the third approach to carbon fixation in plants. CAM plants have a unique strategy where their stomata remain closed during the daytime to minimize water loss through transpiration. Instead, they open their stomata during the night to take in carbon dioxide, which is stored in the form of organic acids in mesophyll cells.
Here is a breakdown of the two-phase cycle that characterizes the CAM pathway:
Now that you have an understanding of C₃, C₄, and CAM carbon fixation processes individually, let's explore the differences between these pathways.
The key difference among C₃, C₄, and CAM photosynthesis lies in how they handle carbon fixation and their adaptation to different environmental conditions. C₃ photosynthesis involves the direct production of a three-carbon compound through the Calvin cycle. In contrast, C₄ photosynthesis initially forms a four-carbon compound, which then splits into a three-carbon compound for the Calvin cycle. CAM photosynthesis, on the other hand, collects sunlight during the day and fixes carbon dioxide at night.
C₃ photosynthesis is the most common type and is found in a majority of plant species. In contrast, C₄ photosynthesis is employed by a smaller fraction of vascular plants, about 3%, including examples like crabgrass, sugarcane, and corn. CAM photosynthesis is utilized by plants adapted to arid environments, such as cacti and pineapples.
These different photosynthesis pathways have evolved to cope with photorespiration, a wasteful process that occurs in certain conditions. C₃ plants don't have specific mechanisms to combat photorespiration, while C₄ plants overcome it by separating carbon dioxide fixation and the Calvin cycle into different cells. CAM plants, on the other hand, minimize photorespiration by conducting carbon dioxide fixation and the Calvin cycle at different times, separating day and night.
1. What is the C₃ pathway? |
2. What is the C₄ pathway? |
3. What is the CAM pathway? |
4. What are the differences between the C₃, C₄, and CAM pathways? |
5. Which plants use the C₄ and CAM pathways? |
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