Plant: Tissue Systems
There are many variants of the generalized plant cell and its parts. Similar kinds of cells are organized into structural and functional units, or tissues, which make up the plant as a whole, and new cells (and tissues) are formed at growing points of actively dividing cells. These growing points, called meristems, are located either at the stem and root tips (apical meristems), where they are responsible for the primary growth of plants, or laterally in stems and roots (lateral meristems), where they are responsible for secondary plant growth. Three tissue systems are recognized in vascular plants: dermal, vascular, and ground (or fundamental). Dermal System The dermal system consists of the epidermis, or outermost layer, of the plant body. It forms the skin of the plant, covering the leaves, flowers, roots, fruits, and seeds. Epidermal cells vary greatly in function and structure. The epidermis may contain stomata, openings through which gases are exchanged with the atmosphe