Root nodules are not formed in non-leguminous plants because they grow in

Options

A. Nitrogen deficient soils
B. Soils having bacteria for converting nitrogen into usable from
C. Soils rich in nitrogen
D. All the above.

Answer

### Step-by-Step Solution:

1. **Understanding Root Nodules**: Root nodules are specialized structures formed on the roots of certain plants, particularly legumes. These nodules house nitrogen-fixing bacteria, such as Rhizobium, which convert atmospheric nitrogen into a form that plants can use.

2. **Identifying Non-Leguminous Plants**: Non-leguminous plants are those that do not belong to the legume family. Unlike legumes, these plants do not form root nodules because they do not have a symbiotic relationship with nitrogen-fixing bacteria.

3. **Soil Composition**: Non-leguminous plants often grow in soils that already contain free-living nitrogen-fixing bacteria. These bacteria can convert atmospheric nitrogen into a usable form without the need for root nodules.

4. **Reason for Absence of Nodules**: Since non-leguminous plants can access nitrogen from the soil due to the presence of these bacteria, they do not require the formation of root nodules. Thus, they do not develop these structures.

5. **Conclusion**: The absence of root nodules in non-leguminous plants is primarily due to their growth in soil that already contains nitrogen-fixing bacteria, which provide the necessary nitrogen in a usable form.

### Final Answer:
Root nodules are not formed in non-leguminous plants because they grow in soil that contains nitrogen-fixing bacteria, which convert nitrogen into a usable form.

---