Horticulture Principles and Practices

FIGURE 3–30 (a) Tap root
system. A tap root may be a
swollen root, as found in carrot
(Daucus carota) and radish
(Raphanus sativus). (b) Fibrous
root system.
(a) Tap root
Tap root (swollen)
(b) Fibrous root
FIGURE 3–31 Transverse
sections of dicot and monocot
roots.
Root hair
Epidermis
Cortex
Pericycle
Endodermis
Cortex
Phloem
Xylem
Pith
Pericycle
Epidermis
Phloem
(a) Dicot
Xylem
(b) Monocot
Root hair
FIGURE 3–32 A longitudinal
section of a root cap region.
Protoderm
Ground meristem
Procambium
Apical meristem
Root cap
84 Chapter 3 Plant Anatomy
conditions of the medium permit and provides a strong anchor for the plant. The
tap root system is seen in dicots and gymnosperms.
2. Fibrous root. The fibrous root system is found in monocots and is characterized by
the lack of a single dominant root (Figure 3–30). A dominant root is absent because
the radicle of the embryo dies immediately after germination. Instead, a number of
lateral roots develop, but they do not penetrate the soil as deeply as the tap root.
The transverse sections of a tap root of a dicot root and monocot root are presented
in Figure 3–31. A root exhibits endodermis in the inner layer, which is rare in
stems. The conducting vessels in the roots are connected with the vessels in the stem
and other plant parts. The tip of the root is protected by the root cap (Figure 3–32). As
the root pushes its way through the soil, it sheds its peripheral cells. These cells are
replaced as they are shed. The root epidermis is usually one cell layer thick. One feature
of the root system is the occurrence of root hairs, structures often associated with