Medicinal 1 (PDF)

# The Cell And Cell Differentiation - The Cell: - The fundamental unite of a living organism (plants and animals) - The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic contents (crystals a...

# The Cell And Cell Differentiation - The Cell: - The fundamental unite of a living organism (plants and animals) - The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic contents (crystals and aleurone grains). - Other cytoplasmic inclusions are mitochondria, Golgi bodies, lysosomes, and plastids. - A group of cells with identical form and function is known as a tissue. ## Plant Cell | Part | Description | |---|---| | Cell Wall | | | Vacuole | | | Membrane | | | Peroxisome | | | Cytoplasm | | | Chloroplast | | | Golgi Complex| | | Endoplasmic Reticulum | | | Mitochondria | | | Nucleus | | | Nucleolus | | ## The Cell Wall - The wall of mature Cell consists of: - The middle lamella is the intercellular substance, an amorphous, colloidal layer composed of pectic substance. - Primary wall or the original cambial wall is composed of cellulose and pectic substance. - Secondary wall is formed after the enlargement of the cell has been ceased. It consists mainly of cellulose associated with polysaccharides. - It undergoes to some modifications as deposition of various chemical substance as lignin, suberin and cutin. - Tertiary wall: It is the innermost layer of the cell wall and is usually thin, highly refractive and formed of cellulose. ## Properties of Different Cell Walls  ### Cellulosic Walls - Formed mainly of cellulose which may be accompanied with hemicellulose and pectin. - Cellulose is polysaccharide, composed of linear chain of glucose residue. - **Chemical Properties:** - Give blue color with iodine and sulphuric acid. - Give blue color with chloro- Zinc- iodine. - Give no color with aniline or phloroglucin and HCl. - They dissolve in ammonical solution of copper oxide (Cuoxam) and precipitated with dilute sulphuric acid. ### Mucilaginous Walls - Certain cellulosic cell walls may be converted into gums and mucilages. Mucilage is polysaccharides, consisting of sugar and uronic acid combined with metals. - **Chemical Properties:** - They are variably stained with ruthenium red, iodine sulphuric acid or corallin soda. ### Lignified Walls - Lignin is a strengthening material. - Chemically it is a complex phenylpropaniod polymer. - **Chemical Properties:** - Stain magenta red with phloroglucin and hydrochloric acid. ### Suberised and cutinized walls - Suberin and cutin are mixture of polymerized fatty acids and suberic acid - **Chemical Properties:** - Stain red with alkanna tincture and sudan III ### Chitinous walls - Chitin is a polysaccharide derivative containing acetyl and amino group. - It constitutes the organic skeletal substance of insects and many fungi. - **Chemical Properties:** - When heated with 50% potash at 160 - 170 o C for 1 hour, it is converted into chitosan C14H26016N2, ammonia and acids such as acetic and oxalic. - Chitosan gives a deep violet coloration when treated with iodine solution followed by dilute sulphuric acid. # Cell Differentiation ## Plant Tissue May Be: - **Parenchymatous Tissues:** - Is the fundamental or ground tissues of the plant - They are cellulosic, isodiametric or slightly axially elongated cells with narrow or wide intercellular spaces - The cells show different contents e.g. starch granules, calcium oxalate crystals. - They constitute most of the pith and cortex of the plant. - **Collenchymatous Tissues:** - It is a living mechanical tissue, composed of rounded or elongated cells, with unevenly thickened, nonlignified walls. - The thickening is of cellulose and located commonly in the angles (angular collenchyma) or chiefly on the tangential walls (lamellar collenchyma). - Collenchyma constitutes the typical mechanical tissue of the herbaceous stems, and of the petioles and midribs of leaves. - **Diagram:** - _lamellar collenchyma_: Thickened cell walls are on the edges. - _angular collenchyma_: Thickened cell walls are at the corners. - _lacunar collenchyma_: Thickened cell walls are in the middle, forming air spaces. - _Parenchyma_: Thin walled cells with large intercellular spaces. ## Sclerenchymatous Tissues - They are thick walled; dead, lignified celled mainly for mechanical functions, consist of sclereids and fibres. - **Sclereids:** - They are thick, lignified cells with narrow to wide lumen and isodiametrical in shape or elongated but the length is never many times as the breadth. - **Fibres:** - They are dead, very much elongated, thick, lignified, pitted, polygonal cells usually with tapering pointed ends. - They may have a tortuous irregular outline. - **Diagram:** - This diagram shows examples of **Sclereids** and **Fibres** with text labels. # Secretory Tissues: - **They may be:** - External: - e.g. glandular hair. - Internal: - Include secretory cells, secretory cavities or glands secretory ducts or canals and latex tissues ## Secretory Cells - They occur either isolated or rarely in rows having suberised walls - They differ from the other cells; by their contents and size. - The cells are named after the secretion they contain. - The secretion may be volatile oil (oil cell), resin (resin cell), gum resin, mucilage, enzyme or tannin. ## Secretory Cavities (Glands): - These are internal structures, embedded in a mass of tissue and having cavities within them in which secretions e.g. volatile oil and oleoresin, etc are secreted - According to method of formation they may be: - **Schizogenous:** - Developed by splitting a part of cells thus enclosing a cavity which then become enlarged and lined by epithelial cells formed by the division of the surrounding cells e.g. savin. - **Schizolysigenous:** - Developed at first schizogenously but, later on, increase in size by breaking down the bounding cells e.g. clove, Buchu. - **Lysigenous:** - Developed by breaking down of the cells forming a cavity. - It originates from single cell by the division in different direction forming a solid mass and then by the gradual disintegration of the resulting cells starting from the center e.g. Dictamnus. - **Diagram:** - This diagram explains the different types of glands: **Schizogenous**, **Lysigenous** and ****Schizolysigenous** with text labels. - It also shows the **Laticiferous Vessel** and **Laticiferous Cell** with text labels. ## Secretory Ducts - They are tube like structures which may extend through the whole length of the organ e.g. leaf pinus, or even through the whole of the plant. - They are developed either schizogenously as vitta of Umbelliferse, lysigenously or schizolysigenously as in Capaifera. ## Laticiferous Structures - These include tube-like cells and vessels with a colorless, milky white, yellowish or reddish viscous emulsion called latex. - Latex may contain resin, gum-resin, fat wax, proteins etc. suspended in an aqueous solution of alkaloidal salts, tannins minerals, sugar enzyme etc. - **Latex Cell:** - Usually in the form of tube, branched as in Euphorbia or unbranched as in Cannabis but not anastomosing e.g. Euphorbiaceae and Apocynaceae. - **Latex Vessel:** - They are long simple or branching tube formed by the partial or complete fusion of the transverse walls of a longitudinal series of cells. - They are anastomosing with rough walls e.g. Papaveracea and Compositae. - **Diagram:** - This diagram shows different types of **Laticiferous structures** with text labels.