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 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 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 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 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 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 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 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 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 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 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 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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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 -------------.
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?