Structure
Epidermis – The outer layer of cells
Root hairs – Absorptive unicellular extensions of epidermal cells of a root. These tiny, hair-like structures function as the major site of water and mineral uptake. Root hairs are extremely delicate and subject to desiccation. Root hairs are easily destroyed in transplanting. [Figure 1.]
root hairs
Figure 1. Root hairs are an extension of the epidermis.
Cortex – Primary tissues of a root bound on the outside by the epidermis and on the inside by the endodermis. In a carrot, the cortex becomes a storage organ.
Endodermis – A single layer of cells in a root that separates the cortex tissues from the pericycle.
Pericycle – A layer of cells immediately inside the endodermis. Branch roots arise from the pericycle.
Vascular system
Phloem tissue conducts products of photosynthesis from leaves throughout plant including down to the roots.
Xylem tissue conducts water and minerals up from the roots up through the plant.
Cross section of root
Figure 2. Cross section view of a root.
Zone of maturation – Pipeline section of the roots, conducting water and nutrients from the root hairs up to the stems.
Zone of elongation –Area where new cells are enlarging.
Meristematic zone
Root tip meristem – Region of cell division that supports root elongation, found at the root tips just behind the root cap.
Root cap – A thimble-shaped group of thick-walled cells at the root tip serves as a “hard hat” to push though soil. The root cap protects the tender meristem tissues.