2.5 : Cells are grouped into tissue - study

2.5 :
Cells are grouped
into tissue
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CELL STRUCTURE AND FUNCTIONS
Structures & functions:
Cell membrane and
organelles
Prokaryotic and
eukaryotic cells
Cells are grouped into
tissue
Animal
Plant
Cell transport
Microscopic structures
of plant and animal
cell
Epithelial
Nerve
Muscle
Connective
Meristem
Parenchyma
Collenchyma
Sclerenchyma
Xylem
Phloem
(B) Plant cells
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Learning Outcome:
AT THE END OF THIS TOPIC, STUDENTS SHOULD BE
ABLE TO:
Describe the structure, function and
distribution following types of cells and
tissues:
Plant - meristem, parenchyma,
collenchyma, sclerenchyma, xylem
and phloem.
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PLANT TISSUE
MERISTEMATIC TISSUE
PERMANENT TISSUE
PARENCHYMA
XYLEM
COLLENCHYMA
PHLOEM
SCLERENCHYMA
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PLANT GROWTH
MERISTEM CELL
Plant
Grow continuously throughout the
plant’s life.
Meristematic
tissues
Structure
central large nucleus
dense cytoplasm
small
vacuoles
Small, thin-walled
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CHARACTERISTIC
MERISTEM CELL
1. Small, thin-walled
2. Have a central large nucleus
3. dense cytoplasm
4. small vacuoles.
5. Closely packed with no intercellular air space.
6. Actively divide by mitosis, generating
additional cell.
7. Unspecialized
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CHARACTERISTIC
MERISTEM CELL
Mitotic division
Derivatives
 Displaced
from meristem
 Differentiate
and
incorporated
into tissues &
organs of the
growing
plants.
initial cells
 Remain as meristem
 Produce more cells.
Mitotic division
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TYPES & DISTRIBUTION
MERISTEM CELL
i) Apical meristem
•
•
Located in root tips
and shoot buds
Axillary buds
ii) Lateral meristems
• Located around the
outer edge of stem
& root
• Vascular cambium
& cork cambium
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FUNCTION
MERISTEM CELL
 Provide additional cells
 Enable plant to grow in
length [Primary Growth]
Apical Meristem
Root  allow roots to extend
throughout the soil
Shoot  increase shoots
exposure to light.
Lateral
Meristem
A group of cells which retain
the ability to divide by mitosis
 Vascular cambium
 Add layers of vascular tissue
 Cork cambium
 replaces the epidermis
with thicker, tougher
periderm.
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FUNCTION
MERISTEM CELL
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PLANT TISSUE
MERISTEMATIC TISSUE
PERMANENT TISSUE
PARENCHYMA
XYLEM
COLLENCHYMA
PHLOEM
SCLERENCHYMA
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TYPES AND SPECIALISED CELL: PLANT
 Each type of plant cell has structural
adaptations that make specific functions
possible.
Cellular differentiation
 involve changes both in the cytoplasm and its
organelles and in the cell wall.
 Modifications of cell walls are also important
in how the specialized cells of a plant
function.
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Cell Wall
TYPES AND SPECIALISED CELL: PLANT
•An adhesive layer, the
middle lamella, cements
together the cells wall of
adjacent cells.
The primary cell wall is
secreted as the cell
grows.
Some cells have
secondary walls which
develop after a cell
stops growing.
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PLANT TISSUE
TYPES AND SPECIALISED CELL: PLANT
Ground Tissues are composed of three basic cell
types:
- parenchyma cells
- collenchyma cells
- sclerenchyma cells
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TYPES OF BASIC CELL
PARENCHYMA
TYPES AND SPECIALISED CELL: PLANT
STRUCTURE :
Nucleus present
Usually isodiametric or elongated
Thin cell wall (primary wall)
containing cellulose, hemicellulose
& pectin
Have a large central vacuole
Have a thin layer of cytoplasm
pushed to the periphery
Cells are loosely packed together/
have large intercellular space
Least specialized srtucturally.
Major component of ground
tissues.
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TYPES OF BASIC CELL
TYPES AND SPECIALISED CELL: PLANT
PARENCHYMA
Function : Perform most of metabolic function of plant,
synthesizing and storing various organic products.
 Contain chloroplast for photosynthesis –
chlorenchyma
 Containain colourless plastid for starch storages.
[stem & root]
 Contain chromoplast to attarct polinating agents.
 Large intercellular spaces for gas exchange
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TYPES OF BASIC CELL
TYPES AND SPECIALISED CELL: PLANT
PARENCHYMA
Function : Perform most of metabolic function of plant,
synthesizing and storing various organic products.
 Retain the ability to divide and differentiate into
other types of plant cells.
 epidermis, mesophyll, endodermis, pericycle,
aerenchyma and secretory cells.
 Can form secondary meristematic tissue
 Vascular cambium and cork cambium.
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TYPES OF BASIC CELL
COLLENCHYMA
TYPES AND SPECIALISED CELL: PLANT
STRUCTURE :
 Nucleus present
 Polygonal-shaped and
elongated
 Cells are closely packed /
no or little intercellular
space
 Cell wall (primary wall)
unevenly thickened with
cellulose, pectin and
hemicellulose
 Pits are present between
cell wall
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TYPES OF BASIC CELL
TYPES AND SPECIALISED CELL: PLANT
COLLENCHYMA
Function :
 Supporting tissue for young parts of plant
(shoot,stem,leaf)/ herbaceous plant
 Provide flexible support without restraining
growth.  lack secondary cell wall, absent of
hardening agents lignin in primary wall.
 Giving strength
 Giving flexibility
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TYPES OF BASIC CELL
SCLERENCHYMA
TYPES AND SPECIALISED CELL: PLANT
STRUCTURE :
Has thick secondary cell wall
containing lignin
No nucleus when mature
Elongated with tapering end
(almost spherical)
Has small lumen (pits)
No intracellular space / cells
closely packed
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TYPES OF BASIC CELL
TYPES AND SPECIALISED CELL: PLANT
SCLERENCHYMA
Function :
•
As supporting elements of the
plant
•
Strengtening by lignin, specialized
for support
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TYPES
SCLERENCHYMA
1) FIBER
- Fibers are long, slender and tapered, and
usually occur in groups.
-Those from hemp fibers are used for making
rope and those from flax for weaving into
linen.
2) SCLEREIDS
- Sclereids, shorter than fibers and irregular in
shape, impart the hardness to nutshells and
seed coats and the gritty texture to pear
fruits.
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PLANT TISSUE
MERISTEMATIC TISSUE
PERMANENT TISSUE
PARENCHYMA
XYLEM
COLLENCHYMA
PHLOEM
SCLERENCHYMA
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INTRODUCTION
VASCULAR TISSUE
Vascular tissue, continuous throughout the plant,
is involved in the transport of materials between
roots and shoots.

Two types of vascular tissue are:
Xylem - conveys water and dissolved
minerals upward from roots into the
shoots.
Phloem - transports food made in mature
leaves
to the roots and to
nonphotosynthetic parts of the shoot
system.
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XYLEM


The water conducting elements of
xylem, the tracheids and vessel
elements, are elongated cells
that are dead at functional
maturity, when these cells are
fully specialized for their function.
Both tracheids and vessels have
secondary walls interrupted by
pits, thinner regions where only
primary walls are present
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XYLEM
Tracheids



Long, thin cells with tapered ends.
Water moves from cell to cell mainly
through pits because their secondary
walls are hardened with lignin
Function in support as well as transport.
Vessel elements



Generally wider, shorter, thinner walled,
and less tapered than tracheids.
Vessel elements are aligned end to end,
forming long micropipes, xylem
vessels.
The ends are perforated, enabling water
to flow freely.
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XYLEM
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PHLOEM
•In the phloem, sucrose, other organic compounds,
and some mineral ions move through tubes formed by
chains of cells, sieve-tube members.
•These are alive at functional maturity, although they
lack the nucleus, ribosomes, and a distinct vacuole.
•The end walls, the sieve plates, have pores that
presumably facilitate the flow of fluid between cells.
•A nonconducting nucleated companion cell,
connected to the sieve-tube member, may assist the
sieve-tube cell.
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PHLOEM
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End of session
Thank you for your attention
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