The document provides information about plant cell walls, including their discovery, types, components, structure, and functions. It can be summarized as follows: 1) Plant cell walls were first observed by Robert Hooke in 1665 and are composed of cellulose, hemicellulose, pectin, and sometimes lignin. They provide structural support and protection for plant cells. 2) The primary components of plant cell walls are the middle lamella, primary cell wall, and secondary cell wall. The middle lamella acts as cement between adjacent cells, while the primary cell wall is thin, flexible, and allows growth. 3) Secondary cell walls provide strength and are composed of cellulose microfibrils embedded

1. Welcome
to
My presentation

2. Cell Wall of
plants
Topic

3. Presented By
Name: Siraj Mia
ID : 20309014
Program : BSAg
Section : A
SL.No:16
Presented To
Professor Dr. Ismail
Hossain
Professor of college of
Agricultural Sciences,
IUBAT
International University of
Business Agriculture and
Technology-IUBAT

4. INTRODUCTION
o Cell wall was first observed and named simply as
a ''wall'' by Robert Hooke in 1665.
o In 1804, Karl Rudolphi and J.H.F. Link proved
that cells have independent cell walls.
o A cell wall is a structural layer that surrounds
some types of cells, situated outside the cell
membrane.
o It can be tough, flexible and rigid which provides
cell with both structural support and protection.

5. INTRODUCTION
o On the basis of chemical composition of cell
wall there are three types of cell wall:
1) Bacterial Cell Wall : made up of Mucopeptide
and Muramic acid.
2) Cell wall of Fungi: made up of Chitin.
3) Plant Cell wall: made up of Cellulose.

6. PLANT CELL WALL
o The plant cell wall is a remarkable structure. It
provides the most significant difference between
plant cells and other eukaryotic cells.
o The wall is rigid(up to many micrometers in
thickness) and gives plant cells a very defined
shape.
o While most cells have a outer membrane , none
is comparable in strength to the plant cell wall.
The cell wall is the reason for the difference
between plant and animal cell functions. Because
the plant has evolved this rigid structure.

7. COMPONENTS OF PLANT
CELL WALL
o The plant cell wall composed of :
1. The Middle Lamella
2. The Primary Cell Wall
3.The Secondary Cell Wall
4. The Tertiary Cell Wall

8. PLANT CELL WALL STRUCTURE
Plant CellWall
Structure
Middle
J-Lamella
Pectin-
Cross-Unking
Glycan
Cellulose
Mlcrofibrlls
Primary
Cell
Wall
:J- Plasma
Membrane
Figure1

9. 1. MIDDLE LAMELLA
o It is present between two adjacent cells.
o It is situated outside primary cell wall and
is made up of calcium and magnesium pectate.
o It acts as cement which holds the adjacent cells together.
1. PRIMARY CELL WALL
o It is formed after the middle lamella.
o A thin, flexible and extensible layer.
o It is capable of growth and expansion.
o The backbone of primary cell wall is formed by the cellulose
fibrils.
o The matrix is composed of hemicellulose, pectin compounds,
lipids, structural proteins.

10. STRUCTURE OF PRIMARY
CELL WALL
Middle
lamella L
Primary
cell wall
--H e m i c e l lul ose
- P e c t i n
..-cellulose
microfibril
Soluble protein

11. 1. SECONDARY CELL WALL
o It is extremely rigid and provides strength.
o It is not found in all cell types.
o It consists of three layers known as Sl(outer),S2(middle) and
S3(inner).
o It is composed of cellulose, hemicellulose and lignin.
Structure of secondary cell wall
- - s .
Prima,y walJ 0. 1-0.J ,, m
Mlod>e1amo11a 0.2-J.O i•m

12. 1.TERTIARY CELL WALL
o Tertiary cell wall is deposited in few cells.
o It is considered to be dry residue of protoplast .
o Besides cellulose and hemi-cellulose, xylan is also present.
►PLASMODESMATA
o Plasmodesmata are protoplasmic
strands that connect the protoplasts of
neighboring cells.
o Diameter is 40-50 nm.

13. COMPOSITION OF CELL
WALL
o The cell wall is mainly composed of carbohydrate materials.
The major components of cell wall are
cellulose,pectins, hemicelluloses, proteins and
phenolics.
Cellulose: It provides shape and strength to the cell wall. It
composes 20-30 % of the dry weight of primary wall
and accounts 40-90% of the dry weight of secondary
wall.
Pectins: They are group of polysaccharides, which are rich in
galacturonic acid, rhamnose,arabinose and galactose
.Pectins are present in high concentration in the middle
lamella where they presumably serve the function of
cementing adjacent cells together.

14. Hemicelluloses: These are matrix polysaccharides
built up of a variety of different sugars. They differ
in different species and in different cell types.
Proteins: Different varieties of protein are present in
the cell wall, most of which are linked with
carbohydrate forming glycoprotein. The cell wall
glycoprotein extensin contains an unusual amino
acid hydroxyproline (about 40%), which is
generally absent from the protoplast. Extensins are
present in the primary cell walls of dicots making
up one to ten percent of the wall.

15. SL. NO. FEATURES PRIMARY CELL WALL
SECONDARY CELL wall
1
Oecurrence In all the plants cellcells
ln only mature and non
dividing cells
2 Position Inner to middle lamella
Inner to primary cell
wall
3 Nature Elastic aud thinner
lnelastic. rigid and
thicker
4 Pits Absent Present
6
Additional Materials Absent
Present lignin
7 Amount of cellulose Low High
8 Extensibility Present Generally absent
10 Hydration more (60%) Less (30 -40%)
DIFFERENCE BETWEEN THE
PRIMARY AND SECONDARY CELL
WALL

16. FUNCTIONS OF CELL
WALL
o They determine the morphology, growth and development
of plant cells.
o They protect the protoplasm from invasion by viral,
bacterial and fungal pathogens.
o They are rigid structures and thus help the plant in
withstanding the gravitational forces.
o They are involved in the transport of materials and
metabolites into and out of cell.
o They withstand the turgor pressure which develops within
the cells due to high osmotic pressure.

17. •

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