PLANT TISSUES AND ORGANS
Fig. 38.6
REMEMBER:
“STEM CELLS IS TO ANIMAL CELLS
MERISTEMS IS TO PLANT CELLS”
MERISTEM
MERISTEM
Tissues of most plants consisting of undifferentiated
cells (meristematic cells), found in zones of the plant
where growth can take place (tips of the roots and
stems). The meristematic cells give rise to various
organs of the plant:
a. Terminal meristems- ends of stems, branches and roots
b. Axillary meristems- base of leaves, branches
c. Lateral meristems are parallel to sides of plant parts
and increase girth.
TYPES OF MERISTEM

Primary Growth
 Apical

Meristems
Secondary Growth
 Vascular
cambium
 Cork Cambium
PRIMARY GROWTH
The apical meristems give rise to three types of
embryonic tissue system, called primary
meristems.



Protoderm (forms the epidermis)
Procambium (produces the primary vascular tissues)
Ground Meristem (forms the ground tissues)
SECONDARY GROWTH
The secondary growth are most dramatic in
woody plants, which have two lateral meristems.


Cork Cambium
(produces the cork cells of the outer bark)
Vascular Cambium
(produces secondary vascular tissues)
PLANT TISSUES
FLOWERING PLANTS HAVE 3 BASIC
TISSUE TYPES

Dermal (from the Protoderm)
Cover surface of plant and for Protection
 The guard cells, trichomes and root hairs are specialized
cells that occurs in the epidermis


Vascular (from the Procambium)


Conducting tissue (Xylem and Phloem)
Ground (from the Ground Meristem)

Consists of the Parenchyma, Collenchyma and Sclerenchyma
cells
VASCULAR TISSUE

Xylem
 Mostly
to conduct water and nutrients
 E.g., roots to shoots

Phloem
 Mostly
to conduct sugars, amino acids, etc.
 E.g., leaves to roots or flowers
THE GROUND TISSUES
PARENCHYMA CELLS
The most abundant cells of primary tissues, which have large
vacuoles and thin walls. They have functional nuclei and are
capable of dividing, commonly also store food and water.
COLLENCHYMA CELLS
They are relatively flexible, provide support for plant organ,
allowing them to bend without breaking. The part of celery that
we eat have “strings” that consists mainly of collenhyma and
vascular bundles.
SCLERENCHYMA CELLS
They are tough and with thick walls their secondary cell walls are often
impregnated with LIGNIN, a highly branched polymer that makes cell
walls more rigid. They have two types the Fibers and Sclerids. Both of
these tough, thick-walled cell types serve to strengthen the tissue in which
they occur.
Vegetative Organs
Roots
Stems
Leaves

ROOTS and ROOT SYSTEMS
Root Structure and Function




Penetration of Soil
Gravitropism Downward Growth
Water and Mineral Intake (Absorption)
Storage of Materials
Anchor the plant
 Nitrogen Fixation
 Conduction (Xylem and Phloem)

STRUCTURE OF ROOTS:
Longitudinal Section of Roots (Length)
Root cap
 Zone of cell division
(meristematic region)
 Zone of cell elongation
 Zone of maturation

ROOT CAP
It covers and protects the delicate growing tip
of the root from injury and damage
 It continuously shed cells that facilitate the
growth of the root through the soil.
 It gives CO2 to the soil (CO2 + H2O =
Carbonic Acid) which dissolves mineral in the
soil.

MERISTEMATIC REGION

Adds new cells
to the root cap
and the region
of elongation
ZONE OF ELONGATION
1 to 3 millimeters above the meristem.
 The cell stops to divide, but the cell
walls expand and vacuoles increases in
size, making the cells longer
 Increase in the length of the roots

ZONE OF MATURATION
Cells are uniform in structure
 Cells begin to differentiate and develop
into many tissues.
 The outermost tissue becomes
Epidermis with root hairs

©1996 Norton Presentation Maker, W. W. Norton & Company
Radish seedlings have roots with long root hairs that increase
the surface area for water and mineral uptake
Zone of Maturation - cell differentiation
Zone of Cell Elongation - cell expansion
Zone of Cell Division - new cells by mitosis
Root Cap - penetration, padding
STRUCTURE OF ROOTS:
Cross Section of Root (Primary Roots)
Root hairs
Cortex
Endodermis (Casparian Strip)
Pericycle

STRUCTURE OF ROOTS:
Cross Section of Root (Secondary Growth)

Cambium – Growth Tissues
The
inner edge of Phloem tissue in the
roots is the cambium

The widening in diameter of a root is
called secondary growth
Types of Roots
……………...
Fibrous Root System
 Taproot System
 Deep-penetrating Fibrous Root
 Fleshy Taproots
 Adventitious Roots
 Brace or Prop Roots
 Climbing Roots
 Propagation Roots

THE STEM
Function of Stems
support leaves to maximize light
absorption
 part of conduit for transport of water,
minerals, and organic solutes
 storage

TWO TYPES OF STEM
Herbaceous
Stems
 Woody
Stems

HERBACEOUS STEM
WOODY STEM
Fig. 38.23
Fig. 38.28a
Fig. 38.28b
Fig. 38.28c