Dermal Tissue System
The dermal tissue system consists of the epidermis and the periderm. The epidermis is a single layer of closely packed cells. It both covers and protects the plant. It can be thought of as the plant's "skin." Depending on the part of the plant that it covers, the dermal tissue system can be specialized to a certain extent. For instance, the epidermis of a plant's leaves secretes a coating called the cuticle that helps the plant retain water.
Epidermis CellsImage copyright Dave Webb.
The periderm, also called bark, replaces the epidermis in plants that undergo secondary growth. The periderm consists of cork cells and protects the plant from pathogens, prevents excessive water loss and provides insulation for the plant.
Xylem and PhloemImage copyright Dave Webb.
Ground Tissue System
The ground tissue system synthesizes organic compounds, supports the plant and provides storage for the plant. It is mostly made up of parenchyma cells but can also include some collenchyma and sclerenchyma cells as well.