Mention the constituents of periderm.

Explanation

### Step-by-Step Text Solution:

1. **Definition of Periderm**: Periderm is the outer layer of a plant that serves as a protective barrier. It is considered a secondary structure that develops during secondary growth.

2. **Constituents of Periderm**: The periderm is composed of three main parts:
- **Phellogen**: This is the meristematic tissue responsible for the formation of the other two layers. It is a layer of actively dividing cells that contributes to the growth of the periderm.
- **Phellem (Cork)**: This layer is produced by the phellogen and serves as the outer protective layer. Phellem cells are suberized, meaning they contain suberin, which makes them waterproof and provides protection against environmental factors.
- **Phelloderm**: This layer is located inward of the phellogen and primarily functions in food storage. It is composed of living cells that can store starch and other nutrients.
...