`C_4` plants are different from `C_3` plants with reference to

Options

A. The substrate that accepts `CO_2` in carbon assimilation
B. Type of end products of photosynthesis
C. Number of ATP consumed in the synthesis of sugar
D. The type of pigments involved in Photosynthesis

Answer

### Step-by-Step Solution:

1. **Understanding C3 and C4 Plants**:
- C3 and C4 plants are two different types of plants that utilize different pathways for photosynthesis. The primary distinction lies in how they fix carbon dioxide (CO2) during the process of photosynthesis.

2. **Examples of C3 and C4 Plants**:
- C3 plants include crops such as wheat, rice, and oats.
- C4 plants include crops such as maize (corn) and sugarcane.

3. **First Product of Photosynthesis**:
- In C3 plants, the first stable product of photosynthesis is a 3-carbon compound known as phosphoglyceric acid (PGA).
- In C4 plants, the first stable product is a 4-carbon compound called oxaloacetic acid (OAA).

4. **CO2 Acceptors**:
- In C3 plants, the CO2 acceptor is ribulose bisphosphate (RuBP), which is a 5-carbon compound.
- In C4 plants, the CO2 acceptor is phosphoenolpyruvate (PEP), which is a 3-carbon compound.

5. **Identifying the Key Difference**:
- The main difference between C3 and C4 plants can be summarized as:
- The substrate that accepts CO2 during carbon assimilation is different. C3 plants use RuBP, while C4 plants use PEP.

6. **Evaluating Options**:
- The options provided in the question include:
1. The substrate that accepts CO2 in carbon assimilation (Correct)
2. The end product of photosynthesis (Incorrect)
3. The number of ATP consumed in the synthesis of sugar (Incorrect)
4. The type of pigment (Incorrect)
- Therefore, the correct answer is the first option regarding the CO2 acceptor.