Plants have their mechanism to survive in critical environmental conditions. Although some plants are comparatively more adaptive and hence survive longer. C4 and CAM are two such plants that are categorized as C3 plants. These plants are more adaptive to heat and hence can survive in a hotter environment, where water is hardly or readily available. Their way of minimizing the water loss makes the difference between these two plants.
C4 vs CAM Plants
The main difference between C4 and CAM Plants is that C4 plants produce 4 carbon compounds and are mesophytic. These are summer plants like sugarcane that can sustain to the hotter environment and also reduce the water supply to some extent. On the contrary, CAM plants refer to Crassulacean Acid Metabolism plants. These plants have a more effective approach towards conserving water, and they utilize CAM Photosynthesis.
C4 plant is a type of plant that utilizes C4 carbon fixation under which the carbon dioxide (CO2) is initially bound to phosphoenolpyruvate in the mesophyll cell that consequently results in the production or formation of four carbon compounds. Before entering the Calvin cycle of photosynthesis, the C4 plant is firstly fixed into a four-carbon atom compound.
CAM refers to Crassulacean Acid Metabolism. Plants like pineapple and cacti use the CAM pathway or mechanism to reduce photorespiration. During the night, the environment is comparatively more cooler; hence these plants collect carbon dioxide (CO2) and store the concentrated carbon dioxide as malate. In the daytime, it is released back and consumed for photosynthesis.
Comparison Table Between C4 and CAM Plants
| Parameters of Comparison | C4 Plants | CAM Plants |
| Definition | It is a type of plant that utilize C4 photosynthesis and produce oxaloacetate as the first stable product during the carbon dioxide fixation process | It is a type of plant that utilizes CAM photosynthesis |
| Type of Plant | C4 plants are Mesophytic | CAM plants are Xerophytic |
| First Stable Product | Oxaloacetate is the first stable product of C4 plants | In CAM plants, Oxaloacetate is formed at night while 3 PGA (phosphoglyceric acid) is formed at daytime |
| Cell Involved | Bundle sheath cells and mesophyll cells | Mesophyll cells |
| Kranz Anatomy | Present | Absent |
What are C4 Plants?
To avoid photorespiration, some plants use the C4 photosynthesis mechanism. These types of plants are called C4 plants. Photorespiration, on the other side, is just a wasteful reaction in which plants take the oxygen and release carbon dioxide. The C4 plants produce oxaloacetate as the first stable product during the carbon fixation process. These plants are mesophytic and utilize the C4 photosynthesis mechanism or pathway.
C4 plants include plants like sugarcane and corn. C4 photosynthesis is the alternative pathway that reduces the opening of stomata in the daytime and also increases the efficiency of an enzyme called Rubisco that is involved in carbon fixation. This process takes place in bundle sheath cells and mesophyll cells. Kranz anatomy is the specialized structure in which C4 photosynthesis occurs.
During the C4 photosynthesis procedure, plants use PEP (phosphoenolpyruvate), which is an alternative enzyme present in the mesophyll cells. This enzyme is used in the starting or initial step of the carbon fixation procedure. The carbon dioxide (CO2) gets fixed by PEP into C4 and then consequently to malate and then finally transmitted or transported to sheath cells. In the C4 photosynthesis pathway, the content of carbon dioxide is fixed at two regions of the leaf.
What are CAM Plants?
Crassulacean Acid Metabolism (CAM) plants are adaptive to the dry environment and include plants like aloe vera and cacti. These plants use CAM photosynthesis to prevent water loss due to transpiration and evaporation. During the night, the carbon dioxide is collected, and stomata get open. Later on, the absorbed carbon dioxide is stored as malate, which is a four-carbon compound in vacuoles.
Oxaloacetate is the first stable product produced during CAM photosynthesis at night, and 3 PGA (phosphoglyceric acid) is produced during the daytime when Oxaloacetate or malate is transported to chloroplast and re-converted to carbon dioxide to support or facilitate photosynthesis.
Main Differences Between C4 and CAM Plants
- C4 and CAM plants varied from each other in various aspects. C4 plant is a type of plant that utilizes C4 photosynthesis and produces oxaloacetate as the first stable product during the carbon dioxide fixation process. CAM plants, on the other side, utilize CAM photosynthesis.
- C4 and CAM are different types of plants.C4 plants are mesophytic, and in the production of glucose in these plants, 12 NADPH and18 ATP is required or needed. CAM plants are Xerophytic and require 12 NADPH and 39 ATP in the production of glucose.
- During photosynthesis, a stable product is formed or produced. C4 plants produced Oxaloacetate as the first stable product. On the contrary, CAM plants produced two stable products. Oxaloacetate is formed at night, while 3 PGA (phosphoglyceric acid) is formed during the daytime.
- During the procedure of carbon dioxide fixation, photosynthesis, and other cells are involved that help in proceeding the process further. Cells involved in C4 plants are bundle sheath cells and mesophyll cells. On the other side, cells involved in the CAM plant are only Mesophyll cells.
- C4 and CAM plants undergo photosynthesis similar to other plants. But Kranz Anatomy makes the difference between these two. Kranz Anatomy is a specialized structure in which the photosynthesis procedure takes place. In C4 plants, the Kranz Anatomy is present. But in CAM plants, Kranz Anatomy is absent.
Conclusion
C4 and CAM both are special category plants that perform carbon fixation mechanisms but vary from each other in their way of minimizing water loss. Both are present in arid environments and utilize the carbon fixation pathway to preserve the water content in the plant. CAM plants effectively utilize the CAM photosynthesis mechanism while C4 plants, on the other way, produce 4 carbon compounds as the first stable product.
References
- https://www.thepharmajournal.com/archives/2017/vol6issue9/PartB/6-8-66-259.pdf
- https://www.sciencedirect.com/science/article/pii/S0031942204001931