Introduction
When it comes to studying photosynthesis, there are a lot of different compounds and pigments involved. One of the first and most important compounds in the process is the molecule ribulose bisphosphate (RuBP). This is the molecule that accepts the CO2 that is gathered from the air, and is responsible for the production of the four-carbon sugar molecules needed for photosynthesis. There are actually two different types of RuBP molecules, C3 and C4.While there are many similarities between the two, there are also many differences that are important to know.
What are C3 plants?
C3 plants are a group of plants that have an intermediate level of photosynthesis. Intermediate photosynthesis means that these plants can use both the Calvin cycle and the Crassulacean acid metabolism (CAM) cycle to fix carbon dioxide. Most plants use one or the other, but C3 plants can use both to their advantage, depending on the environmental conditions. For example, if it’s hot and dry, C3 plants will use the CAM cycle to save water. In other words, compared to C4 plants, C3 plants are better at tolerating shady conditions and lower levels of sunlight. They also have a longer growing season, making them a great option for gardeners who live in colder climates.
What are C4 plants?
C4 plants are a special type of plants that have a unique way of photosynthesizing. This process is more efficient in hot and dry environments, making C4 plants well suited for tropical and subtropical climates. C4 plants are recognizable by their unique leaf structure, which has a thick midrib that the other veins run off of. Interestingly, C4 plants are not more efficient in terms of the amount of CO2 they take in or the amount of water they use. So what is the advantage of being a C4 plant? The advantage is that C4 plants can photosynthesize at much higher rates than other plants, making them better suited for hot, dry environments.
C3 vs 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. |
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.
Conclusion
So, what is the difference between C3 and C4? To answer this question it’s necessary to first understand the two types of plants. C3 plants are “dark-green leaf” plants that thrive in areas where there is less sunlight. They are considered to be “cool season” plants because they begin photosynthesis during spring or fall when temperatures are cooler. On the other hand, C4 plants are “light-green leaf” plants which grow in areas with abundant light such as summertime conditions.