Difference between C3 Plants and C4 Plants

C3 plants vs C4 plants

Difference between C3 Plants and C4 Plants: Green plants are unique to possess the ability to fix light energy from sunlight through a process called photosynthesis. The photosynthesis essential involves the synthesis of carbohydrates with atmospheric carbon dioxide, water and energy obtained from the sunlight. The process of photosynthesis in plants is completed in two broad steps, a light dependent ‘Light Reaction’ and a light independent ‘Dark Reaction”.

In the light reaction, the chlorophyll molecules in the plants absorb energy from sunlight and synthesize energy rich chemical molecules such as ATP and reduced coenzymes (NADPHH+). In the dark reaction, these energy rich molecules are used up for the synthesis of carbohydrates with carbon dioxide. There are essentially three different types of dark reaction pathways are operated in different plants on earth and they are named on the basis of the components of these pathways. They are C3 plants, C4 plants and CAM plants. The present post describes the similarities and differences between C3 plants and C4 Plants.

Learn more: Difference between C3 and C4 Cycle

C3 Plants: Plants which uses C3 cycle (Calvin cycle) of dark reaction of photosynthesis. C3 cycle is the first described dark reaction pathway. Majority of the plants (~95%) on earth are C3 type. The first stable product formed in C3 cycle is a three carbon (3C) compound, hence the name. The photosynthetic efficiency of C3 plants is comparatively less due the high rate or photorespiration. For a considerable period of time, the C3 cycle was thought to be the only dark reaction pathway in plants.

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C4 Plants: These plants in addition to C3 cycle, uses an additional dark reaction pathway called C4 cycle. Very few plants (~5%) on earth are C4 type. The first stable product formed in C4 cycle is a four carbon (4C) compound, hence the name. The photosynthetic efficiency of C4 plants is very high due to the absence of photorespiration.

Similarities between C3 and C4 Plants

@. Both C3 and C4 are types of dark reactions of photosynthesis.

@. Both C3 and C4 plants fix energy from sunlight.

@. Both C3 and C4 plants synthesize carbohydrates.

@. The general equation of photosynthesis (6CO₂ + 12H₂O → 6C₆H₁₂O₆ + 6O₂ + 6H₂O) is similar in both C3 and C4 plants.

@. Both C3 and C4 plants require 6 molecules of CO2 and 12 molecules of water to synthesis one molecule of glucose.

@. The carbohydrate product of both C3 and C4 cycle is a three-carbon sugar phosphate molecules called Glyceraldehyde 3 phosphate (G3P).

@. Both C3 and C4 plants requires chloroplasts for doing photosynthesis.

@. The light reaction of photosynthesis is similar in both C3 and C4 plants.

@. RuBP can accept CO₂ in both C3 and C4 plants.