Root Structure
How is the root organized longitudinally?
Moving from root tip toward the plant body (proximal), you will observe these structures: root cap, region of cell division, region of elongation, and the region of maturation
Region of Maturation (RoM)
Also, called the Region of Cell Differentiation
Proximal to RoE
Cells differentiate and mature
Root hairs created
Area of water absorption by plant
Region of Elongation (RoE)
An area proximal to the RCD and the apical meristem
Cells entering the G1 Period of Interphase
Cells expand in length
Region of Cell Division (RCD)
An area just behind the root cap
An area of active mitosis (cell division)
This is the Root Apical Meristem
Root Cap
The distal-most portion of the root
Cells created by the apical meristem to protect meristem
How is the root organized in cross-section?
Moving from the outside toward the center of the root, you will observe these structures: the epidermis, the cortex, the endodermis, the pericycle, and the vascular cylinder
Epidermis
The outer layer of cells that protects the root tissues
It is the "outer skin" (epi-dermis) of the organ
Root hairs are visible in the mature portions of the primary roots
Cortex
The area beneath the epidermis, up to the endodermis
This is mostly ground tissues that store materials and provide peripheral strength
Endodermis
A single ring-like band of cells that regulate water and mineral uptake
It is the "inner skin" (endo-dermis) of the organ
The cells have special thickening called Casparian Strips
Lignin (not suberin) coats the cells on the radial and transverse walls, which prevents passive movement of water from the cortex to the vascular cylinder (Geldner 2013)
Therefore, the plant has to actively move water into the vascular cylinder (symplastic transport)
Pericycle
Underneath the endodermis, is a single ring-like band of cells that creates lateral roots
These pericycle cells are embryonic, and not thickened
Vascular Cylinder or Stele
The vascular cylinder, or stele, are the names given to the area that includes the xylem and phloem
In young roots, the stele is composed of primary xylem and primary phloem, which formed from the root apical meristem