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 regarding what promotes cell division in root nodules, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Root Nodules**:
- Root nodules are specialized structures formed in the roots of leguminous plants. They are essential for nitrogen fixation, which is a process where atmospheric nitrogen is converted into a form usable by plants.

2. **Role of Plant Hormones**:
- In the formation of root nodules, specific hormones play a crucial role. The primary hormone involved is **auxin**, which is secreted by the plant's cortical cells. Auxin is known to promote cell division and growth.

3. **Role of Bacterial Secretions**:
- The bacteria involved in this symbiotic relationship, specifically **Rhizobium**, secrete a different type of hormone known as **cytokinin**. Cytokinins are also involved in promoting cell division and are crucial for the development of root nodules.

4. **Combining the Information**:
- Therefore, the cell division in root nodules is promoted by **auxin** secreted by the plant and **cytokinin** secreted by the bacteria.

5. **Final Answer**:
- The correct completion of the statement is: "Cell division in root nodules is promoted by **auxin** secreted by plant and **cytokinin** secreted by bacteria."