Difference Between C3 And C4 Plants

C3 plants are defined as the plants that use the C3 pathway in the dark reaction of photosynthesis. There is no indication of Kranz anatomy by the leaves of these plants. These plants undergo the photosynthesis process only when the stomata are open. C3 plants include around 95% of the shrubs, trees, and plants. While C4 plants are defined as the plants that use the C4 pathway during the dark reaction. The chloroplasts of these plants are dimorphic and unlike C3 plants the leaves of C4 plants possess kranz anatomy. C4 plants include around 5% of plants on earth. Learn the difference between C3 and C4 plants here.

Difference Between C3 And C4 Plants

Let us understand the important difference between C3 and C4 plants.

Character	C3 plants	C4 plants
Definition	C3 plants use the C3 pathway or Calvin cycle for the dark reaction of photosynthesis.	C4 plants use the C4 pathway or Hatch-Slack Pathway for the dark reaction of photosynthesis.
Season	These plants are cool-season plants, commonly found in cool and wet areas.	These plants are warm-season plants, commonly found in dry areas.
Product	The product found in the C3 cycle is a 3 carbon compound – phosphoglyceric acid.	The product found in the C4 cycle is a 4 carbon compound – Oxaloacetic acid.
Presence	95% of total green plants on earth are C3 plants.	About 5% of plants are C4 plants on earth.
Conditions	These plants are abundant in temperate conditions.	These plants are abundant in tropical conditions.
Kranz anatomy	Leaves do not have Kranz anatomy.	Leaves have Kranz anatomy.
Chloroplast	In this, the bundle sheath cells do not contain chloroplasts.	In this, the bundle sheath cells contain chloroplasts.
CO2 acceptors	C3 plants possess only one CO2 acceptor.	C4 plants possess two CO2 acceptors.
Secondary acceptor	C3 plants do not consist of secondary CO2 acceptor.	C4 plants consist of secondary CO2 acceptor.
Photosynthesis	It performs photosynthesis only when stomata are open.	It performs photosynthesis even when stomata are close.
Peripheral reticulum	The chloroplasts do not consist of the peripheral reticulum.	The chloroplasts consist of the peripheral reticulum.
Temperature	The optimum temperature for photosynthesis is very low.	The optimum temperature for photosynthesis is high.
Efficiency	C3 plants are less efficient in photosynthesis.	C4 plants are more efficient in photosynthesis.
Photorespiration	The photorespiration rate is very high.	Photorespiration is absent.
CO2 fixation	It is slow in C3 plants.	It is comparatively faster in C3 plants.
Mesophyll Cell	In this, the dark reaction takes place only in the mesophyll cells.	In this, mesophyll cells will only perform the initial steps of the C4 cycle. main steps are carried out in bundle sheath cells.
CO2 Composition	The carbon dioxide composition point is high in these plants.	The carbon dioxide composition point is low in these plants.
Growth	The growth occurs when the soil temperature is between 4-7 degrees.	The growth occurs when the soil temperature is between 16-21 degree.
Example	Wheat, Oats, Rice, Sunflower, Cotton.	Maize, Sugarcane, Amaranthus.

C3​ plants

C3 plants are defined as a common plant that does not consist of any photosynthetic adaptations to reduce photorespiration. The plants that use fixation of the carbon dioxide by rubisco are known as C3 plants. This fixation is done by the Calvin cycle. Approximately 85% of the plants are C3​ plants, including rice, wheat, soybeans, and all trees.

C4 plants

In C4 plants, the light-dependent reactions and the Calvin cycle are physically divided. In this, the light-dependent reactions take place in the mesophyll cells. The mesophyll cell is spongy tissue present in the middle of the leaf. While the Calvin cycle occurs in special cells around the leaf veins. These cells are known as bundle-sheath cells.

Let us understand, how this division helps with the example of C4​ photosynthesis. It starts with the fixation of atmospheric CO2 in the mesophyll cells to form a simple, 4-carbon organic acid. It is also known as oxaloacetate. This process is done by a non-rubisco enzyme, PEP carboxylase, that does not tend to bind O2​.

Oxaloacetate is further converted to a similar molecule. This molecule is known as malate. It is then transported into the bundle-sheath cells. Inside the bundle sheath, this malate undergoes breaks down and releases a molecule of CO2. The rubisco plays an important role in fixing CO2 and converting it into the sugars via the Calvin cycle, similar to the C3​ photosynthesis.

Similarities Between C3 And C4 Plants

• Both plants are types of dark reactions of photosynthesis.
• Plants of these fix energy from sunlight.
• Both plants synthesize carbohydrates.
• They require chloroplasts for photosynthesis.
• Both consist of the same light reactions.
• CO2 is accepted by RuBP in both C3 and C4 plants.