Biology

Difference Between C3 And C4 Plants

All plant species rely on photosynthesis that is a complex pathway that is used by plants to fix carbon, present in the atmosphere, into sugar to produce energy sources. The major difference between C3 and C4 plants is that C3 plants use the Calvin cycle as their mechanism for dark reactions in photosynthesis. Photosynthetic functions occur only in mesophyll cells – on the surface of the leaves. On the other hand, C4 plants use the Hatch-Stack cycle as their reaction mechanism in the dark reaction of photosynthesis. Photosynthetic functions occur in mesophyll and bundle sheath cells. In this article, you will learn and understand the basic and key differences between C3 And C4 Plants.

Difference Between C3 And C4 Plants in Tabular Form

C3 Plants

C4 Plants

In C3 Plants, Photosynthesis occurs in mesophyll tissues. Photosynthesis occurs in both mesophyll cells and bundle sheath cells.
Known as cool-season plants. Known as warm-season plants.
Requires a cool and wet environment. Requires tropical and dry environment.
The CO2 acceptor is Rubisco. The CO2 acceptor is PEP carboxylase
The 1st Stable compound is the 3C compound. The 1st Stable compound is a 4-carbon organic acid called oxaloacetate
The optimum temperature for photosynthesis is lower approximately 20-25oC. The optimum temperature for photosynthesis is higher approximately 35-44oC.
Carbon dioxide fixation is slow. Carbon dioxide fixation is faster.

What are C3 Plants?

These are the most common and the most efficient at photosynthesis in cool, wet climates. C4 plants are most efficient at photosynthesis in hot, sunny climates. C3 plants are also known as temperate plants. C3 plants reduce carbon dioxide directly in the chloroplast.  Photosynthesis is a process when carbon dioxide enters a plant through its stomata, and the enzyme Rubisco fixes carbon into sugar using the Calvin cycle. It fuels plant growth. The fixation of CO2 by rubisco is the first step of the Calvin cycle. The plants that use this mechanism of carbon fixation are called C3 plants. Approx 95% of plants on the earth are C3 plants. They are also known as temperate plants. The process of photosynthesis can occurs if the micropores (stomata) on leaves are open. The leaves of C3 plant do not show kranz anatomy. C3 plants exhibit the C3 pathway. It is the three-carbon compound (3-PGA). Here the first carbon compound produced has three carbon atoms. The Calvin cycle is used to convert carbon dioxide into carbon. It eliminates greenhouse gas carbon dioxide from the atmosphere efficiently. Calvin cycle helps plants to store energy for a more extended period. These plants are highly rich in proteins. They can be annual perennial. Wheat, rye, oats, orchard grass, etc are some examples of C3 Plants.

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What are C4 Plants?

C4 plants sound like something which should be associated with Hollywood action movies! However, C4 plants are just a type of plant that uses a specific photosynthesis mechanism (C4 photosynthesis) in order to avoid photorespiration. Photorespiration is a wasteful reaction that takes place if plants take in oxygen and give out carbon dioxide instead of taking in carbon dioxide and releasing oxygen. They contain a particular type of leaf anatomy. C4 plant uses Phosphoenolpyruvate carboxylase (PEP enzyme) instead of photorespiration to enter the Calvin cycle. By the light, the enzymes of C4 metabolism regulates. PEP enzyme is more attracted to carbon dioxide molecules and reacts less with oxygen molecules. PEP carboxylase does not tend to bind O2.

Conclusion

  • C3 plants have 50% lower photosynthesis efficiency than C4 plants.
  • C3 plants consist of 3-phosphoglycerate with three carbon atoms.
  • C4 plants have better robustness
  • C4 plants are more productive in the hot and dry climate
  • C3 plants reduce carbon dioxide directly in the chloroplast.
  • C3 plants have a denser topology
  • C3 Plants have less modularity
  • C4 Plants have high modularity
  • C3 plants have less carbon dioxide than C4 plants.
  • C3 plants have lower radiation use efficiency than C4 plants

 

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