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PLANT TISSUES AND ORGANS
Fig. 38.6
“STEM CELLS IS TO ANIMAL CELLSMERISTEMS IS TO PLANT CELLS”
REMEMBER:
MERISTEM
a. Terminal meristems- ends of stems, branches and roots
b. Axillary meristems- base of leaves, branchesc. Lateral meristems are parallel to sides of plant
parts and increase girth.
MERISTEMTissues 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:
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
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.
PARENCHYMA 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.
COLLENCHYMA 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.
SCLERENCHYMA CELLS
Vegetative OrgansRootsStemsLeaves
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 structureCells begin to differentiate and develop into many tissues.
The outermost tissue becomes Epidermis with root hairs
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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 hairsCortexEndodermis (Casparian Strip)Pericycle
STRUCTURE OF ROOTS: Cross Section of Root (Secondary Growth)
Cambium – Growth TissuesThe 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
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