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. **Identify the Context**: Understand that the question pertains to leguminous plants and their symbiotic relationship with nitrogen-fixing bacteria, particularly Rhizobium.

2. **Understand Nodule Formation**: Recognize that during the process of nodule formation, plants release specific substances that facilitate the establishment of this symbiotic relationship.

3. **Identify Key Substances**: The primary substance released by leguminous plants during nodule formation is a signaling molecule known as a "pleonide."

4. **Name the Specific Pleonide**: The specific pleonide involved in this process is called "rikazobin." This substance plays a crucial role in the adhesion of Rhizobium bacteria to the root cells of the leguminous plants.

5. **Role of Calcium**: Understand that the release of rikazobin leads to an increase in calcium, which aids in the adhesion of the bacteria to the root cell walls, facilitating infection and subsequent nodule formation.

6. **Conclusion**: Therefore, the correct answer to the question is "rikazobin," as it is the substance released by plants during nodule formation and symbiotic nitrogen fixation.

### Final Answer:
The substance released by plants during nodule formation and symbiotic nitrogen fixation is **rikazobin**.