Which of these is released by plant during nodule formation and symbiotic `N_(2)` fixation ?

Options

A. Cytokinin
B. Haem part of Leghaemoglobin
C. Rhicadhesin
D. Globin part of Leghaemoglobin

Answer

To answer the question regarding which substance is released by plants during nodule formation and symbiotic nitrogen fixation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Nodule Formation**:
- Nodule formation occurs in certain plants, particularly those in the Fabaceae family (also known as Leguminaceae). These plants form a symbiotic relationship with nitrogen-fixing bacteria called Rhizobium.

2. **Role of Flavonoids**:
- During the nodule formation process, plants release specific chemicals known as flavonoids. These flavonoids play a crucial role in attracting the Rhizobium bacteria to the plant roots.

3. **Bacterial Response**:
- Once the Rhizobium bacteria are attracted to the plant roots, they secrete a protein called **ric adhesin**. This protein is essential for the adhesion of the bacteria to the plant's cell wall.

4. **Infection and Nodule Development**:
- After adhesion, the bacteria infect the plant roots, leading to the formation of root nodules. Inside these nodules, the bacteria transform into a form known as bacteroids, which are responsible for nitrogen fixation.

5. **Conclusion**:
- The specific substance released by the plant during nodule formation and symbiotic nitrogen fixation is **ric adhesin**. Therefore, the correct answer to the question is option number 3: **ric adhesin**.