There are three internal zones in a plant root. The meristem, which is at the tip of the root, is the area in which new cells grow and divide. Behind the meristem, cells absorb water and food in the elongation zone. Here, the enlarged cells push the root into the soil. In the maturation zone, which is behind the elongation zone, cells develop into different types of plant tissue, such as vascular and epidermal tissue.
Root tissue is composed of layers of cells. In the outermost layer or epidermis, cells absorb water and nutrients through fine root hairs which extend into the soil. The root hairs also increase the surface area available for absorption. The next layer of cells is the cortex, which conducts water into the root’s vascular system. Casparian strips are fatty cells which determine the types of nutrients absorbed. Branch roots develop from an inner layer of cells known as the pericycle. The endodermis is a filtration layer of cells between the cortex and pericycle.
At the center of the root, vascular tissue transports water and nutrients between the root system and the rest of the plant. In some plants, known as monocots, vascular tissue is located around the center of the root. Phloem is a type of vascular tissue which carries photosynthesis products from the leaves to the roots. Xylem tissue carries water and nutrients from the roots to the rest of the plant.
The root cap is an outer layer of cells at the tip of the root. It sheds the oldest cells, which protect the meristem as it pushes through the soil. The root cap also detects gravity and determines the root’s growth direction. A layer of mucigel coats and lubricates the root cap, and makes some nutrients more available to the plant. The University of Miami Department of Biology describes mucigel as a mucus-like substance.