13 Smooth Sailing Difference between C3, C4 and CAM Pathways In Tabular Form

What is the difference between C3, C4, and CAM pathways?

Green plants need sunlight to make their own food through the process of photosynthesis. The manufactured food help to facilitate plant growth and distribution on the earth.

The process of photosynthesis can occur either in light reaction or dark reaction. During the light reaction stage, the green part of the plant traps energy from the sunlight and synthesize energy-rich chemical molecules.

On the other hand, the dark reaction stage is where plants use energy-rich molecules to synthesize carbohydrates and carbon dioxide.

The lesson provides detailed insight into the difference between C3, C4, and CAM pathways for easier understanding of dark reaction pathways in plants.

What Are C3 Plants?

C3 plants are those that produce 3 carbon molecules or 3-phosphoglyceric acid as the first product during carbon fixation. The C3 pathway tends to be completed in three stages such as carboxylation, reduction, and regeneration.

According to research, about 85% of plants on the universe are C3 plants. It is the reason why C4 plants are also known as cool-season or temperate plants.

These plants have the ability to reduce carbon dioxide in the chloroplast with the help of ribulose biphosphate carboxylase to produce 3-phosphoglyceric acid.

Later the NADPH and ATP phosphorylate help to produce glucose as well as ATP. The cycle keeps on regenerating RuBP once it commences again.

Examples of C3 plants include rice, wheat, oats, orchid grass, and ryegrass among many others. These plants are perennial and regarded to contain a lot of proteins.

What Are C4 Plants?

C4 plants have the ability to convert sunlight energy into oxaloacetate acid which normally takes place before C3 cycle. It later converts oxaloacetate acid into energy and this is the reason why it is regarded to be efficient than C3 pathways.

It is a process that occurs in two steps and mostly in mesophyll and bundle sheath cells of the chloroplast. The diagram below outlines how the process takes place in a C4 plant.

Examples of C4 plants include pearl millet, corn, and sudangrass, Indian grass, switchgrass, and big bluestem. They contain little amount of proteins when compared to C3 plants.

What Are CAM Plants?

CAM plants tend to experience both the light-dependent reaction and the Calvin cycle. These two reactions tend to occur separately in the plants.

The light-dependent reaction in CAM plants occurs in mesophyll cells while dark reaction occurs in the spongy cells that are found in the bundle of the sheath.

Examples of CAM plants are bromeliads, cactus, euphorbias, and orchids. These plants tend to encourage loss of water vapor and they are normally unexploited.

Comparison Chart

Basic Terms	C3 Plants	C4 Plants	CAM Plants
Cells Involved	Mesophyll cells	Mesophyll cells and bundle sheath cell	Mesophyll cells
Examples of Plants	Cotton, Sunflower, Rice, Beans, and Spinach.	Maize, Wheat, Oats, Sorghum, and Sugarcane.	Cacti, bromeliads, euphorbias, and orchids.
Type of Plants Experiencing the cycle.	Xerophytic, Hydrophytic and Mesophytic	Mesophytic	Xerophytic
The first Molecule Produced in Pathway	3-phophoglyceric acid	Malic acid or aspartic acid	Malate
Leaf Anatomy	Typical	Kranz	Xeromorphic
Number of Steps in the Pathway	One	Two	Two
Opening of Stomata	Open during the day and closed at night	Open during the day and closed at night	Open at night and close at day time.
Photorespiration Rate	High	Low / Negligible	Very Low / Negligible
CO2 compensation point	30-70	6-10	0-5 in dark
Initial CO2 acceptor	Ribulose-1,5-biphophate(RuBP)	Phosphoenolpyruvate (PEP)	Phosphoenolpyruvate (PEP)
The ratio of products : CO2: ATP: NADPH2	1:3:2	1:5:2	1:6.5:2
The optimum temperature for photosynthesis	15-25 °C	30-40 °C	> 40 degrees °C
Take place in	All photosynthetic plants.	In tropical plants	Semi-arid condition.

Core Differences

CO2 compensation point in C3 plants is 30-70, C4 plants are 6-10, and CAM plants are 0-5 in the darkness.
C4 pathway experiences Kranz Anatomy while C3 and C4 do not occur in these plants.
THE initial CO2 acceptor of the C3 pathway is Ribulose-1, 5-biphosphate (RuBP) while C4 and CAM pathway is Phosphoenolpyruvate (PEP).
The ratio of CO2: ATP: NADPH2 in C3 is 1:3:2, C4 is 1:5:2, and CAM is 1:6.5:2.
The optimum temperature of photosynthesis in C3 is 15-25 ° C, C4 is 30-40 ° C and CAM plants are> 40°C.
The first stable products of the C3 pathway are 3-phosphoglycerate (3-PGA), C4 pathway is Oxaloacetate (OAA) and the CAM pathway is Oxaloacetate (OAA) at night and 3 PGA at daytime.
The C3 pathway requires 12 NADPH and 18 ATPs, C4 pathway requires 2 NADPH and 30 ATPs while CAM requires 12 NADPH and 39 ATPs.
Types of plants that experience the C3 cycle are mesophytic, hydrophytic, and xerophytic while those for C4 are mesophytic and CAM are xerophytic.
Examples of C3 plants are Sunflower, Spinach, Beans, Rice, and Cotton while CAM plants are Cacti, orchids and examples of C4 plants are Sugarcane, Sorghum, and Maize.
Cells involved in the C4 pathway are mesophyll cell and bundle sheath cells while the C3 pathway are mesophyll cells and CAM are mesophyll cells.

Similarities between C3, C4 and CAM Plants

Both fixes energy from sunlight
Both enhance the synthesis of carbohydrates
Both reactions take place in the chloroplast
Both reactions occur during dark stage

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Comparison Video

Conclusion

Photosynthesis is the main process of how plants make their own food. The plants are able to convert carbon dioxide from the atmosphere to energy responsible for the synthesis of glucose.

Since plants grow in different climate and habitat then they tend to differ in the process of using energy to synthesize glucose.

This is the main reason behind the creation of the article on the difference between C3, C4, and CAM pathways. I hope the information was useful in your studies.

More Sources and References

C3, C4, and CAM plants. Khan Academy
C4 and CAM Plants. Biology References