UNIT 5: PLANT
TISSUE
PLANT BODY ORGANS
 Plants have organs that compose of different
tissue,
 which in turn are composed of cells of
different types.
 A tissue is a group of cells with a common
function, structure or both.
 An organ consist of several types of tissues
that together carry out particular functions.
 The three basis plant organs are:
 Roots,
 stems
 leaves.
SHOOT SYSTEM
ROOT SYSTEM
The organs are divided into
 the root system (roots and mycorhiza)
 shoot system (leaves and stems)
ROOTS
 Anchor plants
 Root hairs absorb water and minerals.
 Stores carbohydrates.
 Eudicots have a taproot system (one main
vertical root that give rise to lateral roots)
 Monocots have an adventitious root system
(roots that originate from the stem of a plant)
Fig. 35-4
Roots
Propcan
roots be modified to
Many plants havefunctions:
modified
perform different
roots
Strangling”
aerial roots
“
Storage roots
Pneumatophores
Buttress roots
STEMS
 Consist of nodes (where leaves grow) and
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internodes.
The angle between the leave and the stem is
called the axillary bud, this can form a lateral
shoot.
The shoot tip consist of an apical (end) bud.
The inhibition of axillary buds by an apical
bud is called apical dominance.
Stems support the leaves and lateral
branches of a plant.
Stems keep the plant upright.
Fig. 35-5
Rhizomes
Many plants
have modified
stems
Bulbs
Storage leaves
Stem
Stolon
Tubers
 Rhizome: Horizontal shoot that
grows just below the surface.Vertical
shoots emerge from auxillary buds on
the rhizome.
 Stolon: Horizontal shoots that grow
along the surface. Reproduce
asexually.
 Tubers: Enlarged ends of rhizome or
stolon, specialized to store food. The
eyes are clusters of auxillary buds that
mark the nodes.
LEAVES
 Main photosynthetic part of the plant (in
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most vascular plants).
Consist of a flattened blade and a stalk,
called a petiole.
Monocots have no petiole.
Monocots have parallel veins on the leaves
and Eudicots have net venation.
Leaf shape differs: simple leaves (single leaf)
and compound leaves (where the blade
consist of smaller leaflets – leaflets have no
axillary buds.)
Fig. 35-6
(a) Simple leaf
DIFFERENT
LEAF
STRUCTURES
Petiole
Axillary bud
Leaflet
(b) Compound
leaf
Petiole
Axillary bud
(c) Doubly
compound
leaf
Leaflet
Petiole
Axillary bud
Fig. 35-7
Tendrils
Some plant species
have evolved
modified leaves
that serve various
functions
Spines
Storage
leaves
Reproductive leaves
Bracts
Tissue categories in plants
 Each plant organ has:
 dermal,
 vascular and
 ground tissues.
 Each of these three categories forms a tissue
system.
 The dermal tissue system is the plant’s outer
protective covering.
 In non-woody plants it is a single layer called the
epidermis protected by a waxy layer called the
cuticle found on stems and leaves.
 In woody plants, the protective tissue is called
periderm.
 Ground tissue are neither dermal or vascular.
 Internal ground tissue is called the pith.
 Ground tissue that is external to the vascular
tissue is called cortex.
 Ground tissue includes various cells with
specialized functions such as storage,
photosynthesis and supports.
MERISTEMATIC TISSUE
 A flowering plant has the ability to grow its entire life
because it possesses meristematic (embryonic)
tissue.
 The apical meristem are located at or near the tips of
stems and roots, where they increase the length of
their structures by means of mitosis.
 This increase in length is called primary growth.
 Monocots also have an intercalary meristem, this
allows them to regrow lost parts. (It is found between
mature tissues). EXAMPLE: GRASS CUT - GROW
Organization of a plant body
MERISTEMATIC
TISSUE AT TIP
OF STEM
MERISTEMATIC
TISSUE AT TIP
OF ROOTS
APICAL MERISTEM
 Produces three types of meristems, and these
develop into the three types of specialized
primary tissues in the body of the plant:
SPECIALIZED PRIMARY TISSUES:
 Protoderm gives rise to the epidermis
 Ground meristem produced ground tissue
 Procambium produces vascular tissue
FUNCTIONS OF SPECIALIZED
TISSUES
 Epidermal tissue: forms the outer protective
covering of a plant.
 Ground tissue fills the interior of a plant.
 Vascular tissue transports water and
nutrients in a plant and provides support.
EPIDERMAL
TISSUE
EPIDERMAL TISSUE
 Single layer of closely
packed, flat, brick
shaped cells, with a
large vacuole.
 The aerial parts of the
plant are covered with
a cuticle.
 Functions:
- Cuticle minimizes
water loss (because it
has cutin)
- Protects the plant
against bacteria.
Longitudinal section
Cross section
Leaf contain upper and lower
epidermal cells
SPECIALIZE EPIDERMAL CELLS
TRICHOMES
 ROOT HAIR
 TRICHOMES
 STOMA OF LEAF
 CORK OF OLDER
STEMS
ROOT HAIRS
CORK CELLS
STOMATA
ROOT HAIRS
 They are specialized
epidermal cells of
roots.
 Unicellular outgrowth
of the epidermal cell.
 Functions:
 Increase the surface
area of the root for
absorption of water
and minerals.
 Anchor the plant.
TRICHOMES
 Specialized epidermal
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cell of stems and leaves.
Multicellular outgrowths
of the epidermis of
stems and leaves.
Functions:
Protect the plant from
sun
Conserve moisture.
Protect plant from
herbivores, produce toxic
substance.
CUTICLE
MULTICELLULAR
STOMATA
 Specialized epidermal
 FUNCTIONS:
cells called guard cells,
 Transpiration
which are bean shaped,
 Gaseous exchange
enclose an opening
take place through the
called the stoma or pore.
stomata.
 The guard cells contain a
nucleus and
chloroplasts.
 It has a thick inner
membrane and a thin
outer membrane.
 Woody plants have
lenticels.
CLOSED- NIGHT
OPEN - DAY
GROUND TISSUE
•PARENCHYMA
•COLLENCHYMA
•SCLERENCHYMA
GROUND TISSUES
PARENCHYMA TISSUE
 Occur in roots, stems and
leaves.
 Spherical, loosely
packed, big, thin-walled
cells with large vacuoles.
 Intercellular airspaces
between cells.
FUNCTIONS:
 If they have
chloroplasts –
photosynthesis.
 If they have leucoplasts
– they store products
of photosynthesis.
 They can divide to
form more specialized
cells
INTERCELLULAR AIR
SPACES
PARENCHYMA CELLS
COLLENCHYMA TISSUE
 It is composed of
unevenly thickened
primary walls with
additional cellulose and
pectin deposits
especially in the corners.
 Found just beneath the
epidermis of young
stems.
 The cells are slightly
elongated, tightly
packed and overlap each
other.
 FUNCTIONS:
 Mechanical
strengthening and
support to plant organs
SCLERENCHYMA TISSUE
 Cell walls have been
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thickened by impregnation
with lignin.
The cell wall is evenly
thickened and forms a
waterproof barrier
impermeable to water.
In the cell walls are pit
canals that serve as
channels between cells and
to the outside world.
The lumen is small.
Two types of
Sclerenchyma:
Stone cells and fibers
FUNCTIONS:
 Strengthening, support
and protection.
 Found in shell of nuts
and hard parts of fruits
 Fibers give rigidity and
flexibility to the plant.
VASCULAR TISSUE
•XYLEM
•PHLOEM
XYLEM
 Contains 2 types of conducting cells: tracheids
and vessel elements (VE).
 Both cells are hollow and non-living but the VE
is larger and has perforated plates in their end
walls and are arranged to form a continuous
vessel.
 Tracheids have tapered ends with pits.
 It also has other tissue: Xylem fibers, and Xylem
parenchyma.
FUNCTIONS OF XYLEM
 Transports water and minerals from
the roots to the leaves.
 Support and strengthening.
Xylem vessels
Xylem tracheids Xylem fibers
PHLOEM
 Consist of sieve-tubes and companion cells.
 The sieve-tubes form a continuous tube,
they have cytoplasm but no nuclei.
 They have sieve plates between cells.
 The companion cell has a nucleus that
controls both cells because they are
connected by plasmodesmata.
 It also has other tissue: Phloem fibers and
phloem parenchyma
FUNCTIONS OF PHLOEM
 Transports sucrose and other organic
substances, including hormones, from
the leaves to the roots.
 Support and strengthening.
Tissue organization of
Leaves
 KNOW CROSS SECTION THROUGH LEAF