Choose the correct sequence of step w.r.t nodule formation in legumes.
(a) Root nodule formation
(b) Infection thread formation
(c ) Curling of root hair
(d) Division of cortical cells

Options

A. c,d,b,a
B. c,b,d,a
C. c,b,a,d
D. b,c,a,d

Answer

To determine the correct sequence of steps in nodule formation in legumes, we can break down the process as follows:

1. **Curling of Root Hair (c)**: The process begins when the Rhizobium bacteria come into contact with the root hairs of the legume plant. This contact causes the root hairs to curl, which is essential for the bacteria to enter the plant.

2. **Infection Thread Formation (b)**: After the root hair curls, the Rhizobium bacteria penetrate the root hair and form an infection thread. This thread acts as a pathway for the bacteria to move deeper into the plant tissue.

3. **Division of Cortical Cells (d)**: Once the bacteria have moved into the inner cortex through the infection thread, they induce the division of cortical cells. This division is crucial for the development of the nodule.

4. **Root Nodule Formation (a)**: Finally, as a result of the division of cortical cells, root nodules are formed. These nodules house the bacteria, allowing them to fix nitrogen for the plant.

Therefore, the correct sequence of steps is:
(c) Curling of root hair → (b) Infection thread formation → (d) Division of cortical cells → (a) Root nodule formation.

### Final Sequence:
1. Curling of root hair (c)
2. Infection thread formation (b)
3. Division of cortical cells (d)
4. Root nodule formation (a)