Cell division in root nodules is promoted by _________ secreted by plant and ________ secreted by bacteria.

Options

A. Auxin, Cytokinin
B. Cytokinin, Auxin
C. Auxin, Leghemoglobin
D. Nitrogenase, Leg hemoglobin

Answer

To answer the question, "Cell division in root nodules is promoted by _________ secreted by plant and ________ secreted by bacteria," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**: Recognize that the question pertains to the formation of root nodules, which is a symbiotic relationship between leguminous plants and rhizobium bacteria.

2. **Identify the Role of the Plant**: In the process of nodulation, the host plant (legume) plays a crucial role. During early nodule development, the root of the plant is infected by rhizobium bacteria, which triggers certain responses in the plant.

3. **Determine the Plant Secretions**: The cortical cells of the legume roots undergo de-differentiation and secrete a plant hormone known as **auxin**. This hormone is essential for promoting cell division in the root nodules.

4. **Identify the Role of Bacteria**: The rhizobium bacteria also contribute to the process. They secrete another type of hormone called **cytokinin**. This hormone works in conjunction with auxin to promote further cell division.

5. **Conclude the Answer**: Therefore, the complete answer to the question is:
- Cell division in root nodules is promoted by **auxin** secreted by the plant and **cytokinin** secreted by the bacteria.

### Final Answer:
Cell division in root nodules is promoted by **auxin** secreted by the plant and **cytokinin** secreted by bacteria.

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