Economic
importance
of cork
Prevention of loss of
water by evaporation.
Light, compressible, non
reactive and fire resistant.
Protection against entry of microorganisms,
mechanical injury and extremes of temperature.
Light, being filled with air, hence used as
bottle stoppers, shock absorber, insulator.
Significance of Secondary Growth
Adds girth to plant and provides
support to its increasing weight.
The corky bark produced, protects the interior
from abrasion, heat, cold and infection.
Adds new conducting tissues for replacing old
nonfunctioning ones for meeting increased demand.
An Overview of Secondary Growth in Dicot stem
Primary and secondary growth in a three-year-old stem
Epidermis
Primary phloem
Periderm (mainly cork
cambia and cork)
Secondary phloem
Secondary xylem
Vascular cambium
Primary xylem
Pith
2.
3.
1.
Cortex
Epidermis
Primary
phloem
Vascular
cambium
Primary xylem
Pith
Cortex
Remnant of cortex Remnant of epidermis
Secondary phloem
(inner bark)
Periderm (outer bark)
Remnant of
primary xylem Remnant of pith
Vascular cambium
Secondary xylem
(wood)
Remnant of
primary phloem
Remnant of pith Vascular cambium
Remnant of
primary xylem
Secondary phloem
(inner bark)
Periderm (Outer bark; remnants of
primary phloem, cortex and epidermis
are gradually crushed or torn apart
Secondary and sloughed off)
xylem (wood)