Chromosomal doubling for producing piolyploid plants is carried out by

Options

A. PEG
B. NAA
C. EMS
D. Colchincine.

Answer

### Step-by-Step Solution:

1. **Understanding Polyploidy**: Polyploidy refers to the condition of having more than two complete sets of chromosomes. It is a common phenomenon in plants and can lead to increased size, vigor, and adaptability.

2. **Chromosomal Doubling**: To produce polyploid plants, chromosomal doubling is necessary. This process involves increasing the number of chromosome sets in a plant cell.

3. **Role of Colchicine**: Colchicine is a chemical compound that is known for its ability to inhibit mitosis (cell division). It is specifically a mitotic inhibitor, meaning it prevents the formation of the spindle fibers that are necessary for chromosome separation during cell division.

4. **Source of Colchicine**: Colchicine is extracted from the seeds and bulbs of the plant known as autumn crocus (Colchicum autumnale), also referred to as meadow saffron.

5. **Mechanism of Action**: When applied to plant cells, colchicine disrupts the formation of microtubules, which are essential for the proper segregation of chromosomes. As a result, cells fail to divide properly, leading to the doubling of the chromosome number.

6. **Conclusion**: Therefore, the correct answer to the question of which substance is used for chromosomal doubling to produce polyploid plants is **Colchicine**.