Download unit 4: plant tissue

UNIT 4: PLANT
TISSUE
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





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.
Thick inner membrane
Thin outer membrane
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





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.
FUNCTION: Transports water and minerals
from the roots to the leaves.
Support and strengthening.
XYLEM
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: Transports sucrose and other
organic substances, including
hormones, from the leaves to the
roots.
Support and strengthening.
METHODS TO STUDY CELLS
 The microscope is an instrument designed to
observe objects too small to be seen with the
naked eye.
 The human eye cannot distinguish objects
much smaller than 0.1mm.
 The microscope act as an extension of the
eye, allowing one to see smaller objects.
ELECTRON MICROSCOPE
 The electron microscope was developed in
the late 1940’s and soon used in the study of
cells.
 Much more detail can be seen under an
electron microscope. It can magnify parts of
cells at least 300 000 times.
SCANNING ELECTRON MICROGRAPH
TRANSMISSION ELECTRON MICROGRAPH