What are the main functions of the epidermis in plants?

The epidermis is the outermost protective layer of plant organs like leaves, stems, and roots. Its main functions include: 
1. Protection: Protects underlying tissues from mechanical injury, pathogen invasion, and excessive water loss. 
2. Regulation of gas exchange: Contains stomata (in leaves and young stems) for the exchange of oxygen, carbon dioxide, and water vapor. 
3. Absorption: In roots, epidermal cells form root hairs for water and mineral absorption. 
4. Secretion: May secrete protective substances like wax (cuticle).