Plant Cell Types & Contents Lecture 6 PDF

Plant cell types & contents Presented by: Marwa Saeed Galaa Goda Department of Pharmacognosy, Faculty of Pharmacy, SCU  Objectives Plant tissues Cell contents  Cell contents  Cell contents can be identified microscopically,...

Plant cell types & contents Presented by: Marwa Saeed Galaa Goda Department of Pharmacognosy, Faculty of Pharmacy, SCU  Objectives Plant tissues Cell contents  Cell contents  Cell contents can be identified microscopically, chemically and physically.  Cell contents can be identified physically as cell membrane, cytoplasm, nucleus, and cell organelles.  Cell contents can be identified microscopically (crystals) as calcium oxalate and calcium carbonate.  Cell contents can be identified chemically (plant metabolites) as primary metabolites or secondary metabolites.  Cell contents/ Crystals a) Calcium oxalate: Raphides or Prisms Crystal sheath Cluster Crystal layer Acicular Idioblast, Microcrystals or sandy crystals Ex. Senna Ex. Rhubarb Ex. Datura Ex. Squill and Ipecacuanha Ex. Belladonna Calcium oxalate crystals are insoluble in water, glycerin, alcohol, chloral hydrate and caustic alkalis. They dissolve in acids without effervescence (cf. calcium carbonate).  Cell contents/ Crystals b) Calcium carbonate: Cystolith is deposits of calcium carbonate inside enlarged epidermal cells called lithocysts. They may serve as some kind of protection from leaf- eating insects or other animals. Calcium carbonate can be identified by the fact that it dissolves in dilute acids with effervescence. e.g. in hairs (termed cystolith), as in the leaves of Cannabis sativa.  Cell contents/ Plant metabolites (1) Primary Metabolites (Food Storage Products): Food reserve products [carbohydrates, proteins and lipids] (2) Secondary Metabolites: By-products of metabolism as [alkaloids, glycosides, volatile oils, tannins, resins, ……]  Plant metabolites I- Primary Metabolites 1) Carbohydrates (C, H and O) Starches: – Occur in plants as granules. – Consist mainly of amylose (20%), amylopectin (80%) [it is insoluble in water and gives a blue color with iodine]. Uses of starch: 1- Antidote for iodine poisoning. 2- Lubricant for surgeon gloves 3- Tablet disintegrate 4- Suspending agent for barium meals. 5- Starting product for preparation of dextrins. 6- In itching (demulcent) & skin emollient Amylose Amylopectin  Chemical identification of starch: 1- Iodine test: Starch gives blue color with iodine. 2- Molisch test: Starch gives violet ring with alc. α-naphthol+ dps of conc. sulfuric acid. 3- Fehling test: Tube I: Heat starch with dil. HCl in W.B for 20 min, and then add KOH. Tube II: Fehling A+ Fehling B (reagents) Mix Tube II and Tube I to give Reddish brown ppt.  Microscopical identification of starch: 1- Shape [rounded, oval,….] 2- Size [2 µm in rice starch] 3- Hilum: first formed part in the granule 4- Striations: due to variation in the composition of starch layers 5- Aggregation: - Simple: when the granule occupies all the leucoplast with one hilum - Compound: two or more hila in the same leucoplast and grow gradually till meet in flat surface - Semi-compound: common layer of starch is deposited around the components.  Plant metabolites I- Primary Metabolites 2) Proteins  They are nitrogenous organic compounds. They are macromolecules, polymers of L-amino acids.  Stored in plants as aleurone grains, is a specialized dry vacuole where storage proteins accumulate in a stable form in seeds, usually in the endosperm.  Tests for proteins (microscopically): Millon’s reagent: stains proteins red on warming  Plant metabolites I- Primary Metabolites 3) Fixed oils and fats  Occurs in various parts of the plants (especially the seeds).  They are greasy and non-volatile at ordinary temperature.  Fats and oils are lighter than water and insoluble in it.  They produce a permanent stain on paper.  Chemically, Dietary fats are chemically triglycerides. They are mixtures of esters of fatty acids with glycerol. They are hydrolyzed by aqueous alkalis giving soaps (salts of fatty acids) and glycerin.  Oil Red O (ORO) stain is a fat-soluble dye used to stain neutral lipids, cholesteryl esters, and lipoproteins.