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Plants cell wall structure. The Plant Cell Wall Critical to: plant cell growth plant growth and development Organ differentiation response to biotic stress

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plants cell wall structure
Plants cell wall structure

The Plant Cell WallCritical to:

plant cell growth

plant growth and development

Organ differentiation

response to biotic stress

Higher plant cells are encased in a cell wall. The wall not only defines the cell’s shape but also contributes to the structural integrity and

morphology of the entire plant

Plant cell wall structure

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure1
Plants cell wall structure

Function of cell wall

Limits protoplast size preventing cell rupture

Contains enzymes and plays role in absorption,

transport and secretion

May play role in defense against bacteria and fungal

attack.

Provides support to cell as well as whole plant.

Provides medium for transport of water and nutrients

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure2
Plants cell wall structure

Composition

A cell wall is a fairly rigid layer surrounds a cell and located external to the cell

membrane, which provides the cell with structural support and protection. The cell wall also prevents over-expansion when water enters the cell.

Cell walls are found in plants, bacteria, archaea, fungus, and algae.

Animals and most protists do not have cell walls. In plants, the cell wall is constructed primarily from a

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure3
Plants cell wall structure

a carbohydrate polymer called cellulose

N.B. The cell membrane (plasma membrane) surrounds the cytoplasm of a cell and physically separates the intracellular components from the extra cellular environment, thereby serving a function similar to that of the skin

In plants the cell wall is constructed from different materials dependent upon the species.

During the differentiation of the cell, the original cell wall may undergo various chemical modification, which change its physical properties.

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure4
Plants cell wall structure

Component of plant cell wall

The principal modifications are the deposition of ;

Further cellulose,

Hemi-cellulose,

Lignin,

Cutin,

Suberin,

Mucilage,

and Chitin

Cellulose, a structural polysaccharide

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure5
Plants cell wall structure

Cellulosic cell wall

Cellulose is the most abounded carbohydrates; it form 50% or

more of all the carbon in plants.

The cellulose molecules is an insoluble un-branched polysaccharide

consisting of about 10,000 glucose unites .

Color reaction of cellulose:

i-Gives a blue color with chlor-zinc-iodine

ii-Dissolved in ammoniacal solution of copper oxide

iii-Give no color with phloroglucinol & HCL

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure6
Plants cell wall structure

Hemi-Cellulosic cell wall

Group of polysaccharides that are

more soluble than cellulose

They are vary in their chemical

composition from one species of

plant to another

Cellulose fibers are cement together

by a matrix of Hemi cellulose.

Color reaction of Hemi-cellulose:

i-Blue color with iodine

ii-Insoluble in ammoniacal solution of copper oxide

Lignin

Hemi cellulose

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure7
Plants cell wall structure

Lignified cell wall

Composing as much as 35% of the dry weight of the secondary cell wall

Extremely complex polymer composed of complex

molecule derived from certain amino acid (named phenyl propanoid )

Strengthening material which formed the cell wall of tracheids, vessels,fibers

and sclereids of vascular plants

Color reaction of lignin:

i-Phloroglucinol & HCL stains lignified walls pink or red

ii-Acid aniline sulphate stains lignified walls bright yellow

iii-Chlor-Zinc-iodine stains lignified walls yellow

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure8
Plants cell wall structure

Suberized cell wall

Suberin is waterproof material, formed from highly polymerized fatty acids called

suberic acid found in cork cells

Cutinized cell wall

Cutin form a secondary deposit on primary cellulosic wall. Leaves are covered with

a deposit of cutin which may show characteristic papillae

Color reaction for both suberin & cutin:

i-Yellow to brown color with Chlor-zinc-iodine

ii-Red color with Sudan III

iii-Strong solution of potash stains suberin and cutin yellow

vi-Dilute tincture of alkanna stains the walls red

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure9
Plants cell wall structure

Mucilaginous cell wall

The cellulosic cell wall, in this case, is transformed into a

gelatinous mass of carbohydrate in nature, namely gum or mucilage

Mucilaginous walls are found in the epidermal cells and

center of the pith in the gum yielding species of some plants

Chemically, mucilage is a complex molecules of sugars

e.g. glucose, arabinose and xylose With ironic acid

combined with metals

Color reaction:

i- Yellow color or granular precipitation with lead subacetate

By Dr. Youssef Ibrahim Ph.D.

plants cell wall structure10
Plants cell wall structure

Chitinous cell wall

Chemically chitin is formed from a complex unites of N-

acetyl gloucosamine joined by glycoside bonds

Chitin forms the major part of The cell wall of insects and

many fungi, e.g. Ergot

Color reaction of chitin:

Chitin, when heated with 50% of KOH at 160-170 degree

for one hour it is converted to Chitosan , which gives

violet color when treated with 5% iodine solution then

with 1% sulphuric acid

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents
Ergastic cell contents

Ergastic substances

are non-protoplasm materials found in cells.

The Ergastic cell content are usually organic or inorganic

substances that are products of plant cell metabolism

Plants and other photosynthetic organisms convert Carbon dioxide

into billions of tons of organic molecules

Chemical energy stored in these molecules and fuels the metabolic

reactions that produced either food-storage products or by

products of metabolism

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents1
Ergastic cell contents

Ergastic cell contents includes:

Carbohydrates, proteins,fixed oil and fats, alkaloids, glycosides

gums mucilage, volatile oil and resins, tannins and Calcium oxalate.

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents2
Starch

Starch is the typical form of carbohydrate used for energy storage in plants and formed in special cells called chloroplasts

It is a polymer of glucose unites occurs in two forms of different size: Amylose (un-branched glucose units) and Amylopectin (branched chain)

Starch occurs in almost all organs of plants; it is found most abundantly in roots and rhizomes

Starch

Ergastic cell contents

Starch molecule

Starch molecules

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents3
Starch gives blue to violet color with iodine solution

The common types found in powder drugs are:

i-Maize starch

ii-Potato starch

iii-wheat starch

iv-Rice starch

Ergastic cell contents

Maize

Potato

Wheat

Rice

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents4
Proteins

Portions are the most common cell components, developed in the cell as macromolecules. It is composed of amino acids (nitrogenous organic substances)

Proteins are involved in all aspects of plant cell metabolism

It stored in the plant cell in the form of aleurone grains which well seen in oily seeds e.g. caster seed and linseed

Aleurone grain consists of a mass of protein surrounded by a thin membrane, embedded in the ground protein are a rounded bodies (globoids) and angular bodies (crystalloid)

All proteins are insoluble in organic solvents and precipitated by salts of heavy metals and by tannic acid

Proteins gives red color with Millon’s reagent, yellow color with picric acid and violet color with 20% NaOH and copper sulphate solution

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents5
Fixed oil &fats

They are reserved food materials, occurs in the plant in the form of glyceryl (esters of fatty acids with glycerin)

They are greasy, non volatile, viscous liquid, semisolids or solids

Insoluble in water, soluble in ether, chloroform and petroleum ether

Hydrolyzed by aqueous alkalis, giving salt of fatty acid (soap) and glycerin

Fixed oil & fats stained red with tincture alkanna & sudan III also stained brown to black with 1% osomic acid

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents6
Alkaloids

Alkaloids are basic nitrogenous compounds, contain 1 or more nitrogen atoms usually in heterocyclic ring

Alkaloids usually have a physiological action on man or other animals e.g. nicotine in tobacco

Tests for alkaloids:

i- With Mayer’s reagent (potassium mercuric iodide) gives cream PPT

ii- With Wagner’s reagent (iodine/KI) gives brown PPT

iii- With Dragendorff’s reagent ( potassium bismuth iodide) gives reddish PPT

iv-With solution of tannic acid gives dirty white PPT

v-With saturated solution of picric acid gives yellow PPT

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents7
Glycosides

Glycoside is an organic compound of plant origin consisting of a sugar part linked to non-sugar which known as aglycone

Glycoside can be hydrolyzed either by acids or enzymes emulsinto give chemically different aglycone

These differences is the bases of the chemical classification of glycosides into:

1- Phenolic glycosides

found in uva ursi leaves

2-Antheracene glycosides

found in senna leaves

3-Flavonoid glycosides

found in buchu leaves

4-Cyanogenetic glycosides

Found in bitter almond

5-Thio glycosides

found in muster seeds

6-Cardiac glycosides

found in digitalis leaves

7-Saponin glycosides

found in quillaia bark

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents8
Gums & mucilage

Gums and mucilage are polysaccharide complexes formed from sugar & uronic acid and frequently combined with metals

They are insoluble in alcohol but dissolve or swell in water e.g. gum tragacanth

Specific color reactions are:

1-Mucilage of senna & buchu

leaves stained red with

Ruthenium red reagent

2-Muciage of squill stained red with alkaline solution of corallin soda

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents9
Volatile oil & resin

Volatile oils occur as droplets inside the cell, they are soluble in alcohol but sparingly soluble in water

Resin may be found alone as irregular masses in the cell or may be associated with volatile

oils in the form of oleoresins or associated with gum to form gumresins

They stain slowly with dilute tincture of alkanna or with iodine solution

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents10
Tannins

Tannins are widely distributed in the plants and occur in the cell sap, they are soluble in water and in alcohol

Tannins classified into two groups:

1-Hydeolysable tannins(Pyrogallol tannins)

These group hydrolysable by acids or enzymes, give blue color with ferric chloride and present in clove, galls, bearberry leaves and pomegranate bark

2-Condensied tannins

(catechol tannins)

These group include all other tannins which resist hydrolysis with acid and enzymes, give green color with ferric chloride and present in tea, hamamelis leaves, cinnamon and cinchona bark

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents11
Calcium oxalate

Very common cell content in the plant kingdom

It is formed in the cell as a result of the reaction of calcium salts absorbed from the soil and oxalic acid produced in the plant as a result of the metabolic process

Since the formed calcium oxalate is insoluble in water and in the mild acid cell-sap, it is deposited in crystalline form

Calcium oxalate crystals are insoluble in water, alcohol or

acetic acid but dissolves in HCL with out effervescence (distinction from calcium carbonate).

The crystals decomposed with 20% sulphuric acid with formation of needle-shaped crystals of calcium sulphate

Ergastic cell contents

By Dr. Youssef Ibrahim Ph.D.

ergastic cell contents12
Forms of crystals:

Different forms of calcium oxalate afford a valuable aid in the differentiation of drug even in the powder forms

i-Prisms crystals as in quillaia, cascara, and frangula barck

ii-Cluster crystals as in senna leaf

iii-Acicular or needle- shape as in Ipecacuanha root

crystals

iv-Sandy crystals as in cinchona

barck

v-Sphaero-crystal

Ergastic cell contents

Prisms and microcrystal

Cluster

Spherocrystal

Acicular or needle

By Dr. Youssef Ibrahim Ph.D.

questions
Questions

What are the differences between Cell wall and Cell membrane?

In plants, a cell wall plays mostly -------------------role rather than a role as a ---------------------

In plants, the cell wall is constructed primarily from a ------------polymer called -------------.

Food-storage products or by-products of metabolism in most plants are include:-------,-------,-------,

---------,---------,----------and--------.

In plants the cell wall is constructed from different materials dependent

upon the species, these materials are:----------,------------,-----------,-----------,--------

Proteins are most commonly stored in the plant cell in the form of----------

The aleurone grain are a rounded bodies named-------- and angular bodies named---------

Alkaloids are--------------

Glycoside is an organic compound of plant origin consisting of a ------- part linked to non-sugar which known as -------------.

questions1
Questions

The thin non-cellular layer of wax secreted by the epidermis of leaves is the:

lignin

mucilage

cuticle

trichomes

What is the color reaction of Hemi-cellulose with iodine ?

What is the strengthening material which formed the cell wall of tracheids,

vessels, fibers and sclereids of vascular plants?

Why the by-products of the plant cell metabolism are referred to

as ergastic cell conten

What is the difference between cellulose and hemicelluloses?