Nodule formation in leguminous plants occur due to
(i) Cytokinins produced by invading bacteria
(i) Auxins produced by plant cell.
(iii) Auxins produced by invading bacteria.
(iv) Cytokinin produced by plant cell.

Options

A. (i) and (ii) only
B. (i) and (iii) only
C. (iii) and (iv) only
D. (ii) and (iv) only

Answer

To solve the question regarding nodule formation in leguminous plants, we will analyze each of the provided options step by step.

### Step 1: Understand Nodule Formation
Nodules in leguminous plants are specialized structures that form on the roots as a result of infection by nitrogen-fixing bacteria, primarily from the genus Rhizobium. These nodules are crucial for the plant's ability to fix atmospheric nitrogen into a usable form.

### Step 2: Analyze the Options
Now, let's evaluate each option provided in the question:

1. **Cytokinins produced by invading bacteria**:
- Cytokinins are plant hormones that promote cell division and are involved in various plant growth processes. In the context of nodule formation, the invading bacteria (like Rhizobium) do produce substances that can stimulate the formation of nodules, including cytokinins.
- **Conclusion**: This option is correct.

2. **Auxins produced by plant cells**:
- Auxins are another class of plant hormones that play a key role in plant growth and development. They are involved in processes such as cell elongation and differentiation. During nodule formation, auxins produced by the plant cells can also contribute to the development of nodules.
- **Conclusion**: This option is also correct.

3. **Auxins produced by invading bacteria**:
- While some bacteria can produce auxins, in the context of nodule formation, it is primarily the plant's auxins that play a significant role. The contribution of auxins produced by the invading bacteria is not well-established in the literature regarding nodule formation.
- **Conclusion**: This option is incorrect.

4. **Cytokinins produced by plant cells**:
- While cytokinins produced by plant cells are important for various growth processes, the primary stimulation for nodule formation comes from the bacteria. Therefore, this option does not accurately reflect the primary cause of nodule formation.
- **Conclusion**: This option is incorrect.

### Final Conclusion
Based on the analysis:
- The correct answers are **(i) Cytokinins produced by invading bacteria** and **(ii) Auxins produced by plant cells**.

Thus, the correct choice for the question is that nodule formation occurs due to both the cytokinins produced by the invading bacteria and auxins produced by the plant cells.