Plant Tissues Lecture Slides (University of Hertfordshire) PDF

Lecture 2 Plant Tissues Importance of Microscopical Properties Identification of plants Detection of adulterants  Plant tissues Tissues are groups of cells that form a structural and functiona...

Lecture 2 Plant Tissues Importance of Microscopical Properties Identification of plants Detection of adulterants  Plant tissues Tissues are groups of cells that form a structural and functional unit Meristematic tissues Meristems are regions of cell Permanent Tissues division, which are not yet committed to developing into a specialized cell type. Simple Complex Terminal (Apical) Lateral Meristems One cell type Two or more Meristems parallel to sides of cell types. at the ends of stems, plant parts and branches and roots increase width Ground Vascular tissues tissues Intercalary (Axillary) (Xylem, Meristems at the base of leaves Phloem) and branches  Plant Tissues Fit Into 3 Main Categories Dermal tissue Ground Tissue Vascular Parenchyma Tissue Epidermis Trichomes Collenchyma Xylem (hairs) Sclerenchyma Phloem Stomata (Guard cells) Root hairs Plant Tissues Dermal Is generally a continuous single layer of tightly Tissue packed cells that covers outer surface of plant organs (Stems, Leaves,…) Composed of epidermal cells that secrete the waxy cuticle. Waxy cuticle protects against water loss Cuticle Epidermal cells Transverse section (T.S.)  Dermal Tissue Epidermis is formed of single layer of cells without intercellular spaces except for the stomata. Stomata Cuticle Modified epidermal cell Is a protective film to allow gas exchange formed covering the The osteole epidermis (stoma) May be thin or thick, Guard cells. Trichomes smooth or Anticlinal (hairs) Subsidiary striated cells walls Epidermal cells The anticlinal wall extended is the wall outward perpendicular to forming small the surface & may be Straight or projection Wavy  Anticlinal walls Straight anticlinal walls Wavy anticlinal walls Anticlinal walls with stomata under microscope Opened stomata Closed stomata Types of Dicotyledonous stomata according to character and arrangement of subsidiary cells 1-Anomocytic 3- Diacytic stomata stomata The surrounding cells The stomata is vary in number, have surrounding by no special subsidiary cells having arrangement and their long axis generally do not differ perpendicular to the from other epidermal osteole cells and of equal size e.g. Mentha e.g. Digitalis. 2-Paracytic stomata 4-Anisocytic The stomata is stomata surrounded by two The stomata is or more subsidiary surrounding by cells, two of which usually 3 or more having their long subsidiary cells, one axis parallel to the of which is distinctly osteole smaller than others e,g. Senna e.g. Belladonna  Cell Walls Suberized and Cellulosic Lignified Cutinized Chitinious Suberin and Chitin forms Lignin cutin consist of the major part Chief Complex mixtures of of insect cell polysaccharide polymer of polymerized wall of plant cell phenolic wall compoundS fatty acids esters Heated with Suberin 50% potash for Cell wall of Present in ALL thickenings are 1 h, converted tracheids, cell walls present in cells into chitosan, vessels, fibers such as cork ammonia and and sclereids cells. acids. Hemicellulose + Leaves are Chitin + 0.5% iodine Lignified covered with solution of BLUE COLOR wall+ cutin. iodine in phloroglucinol potassium Cellulose+ iodine and HCl gives Cutin and suberin iodide then no blue color red color + suddan III sulphuric acid red color violet color Trichomes or hairs Trichome has two parts: one is embedded in the epidermis; called foot and free part called body. When it falls it leaves a cicatrix. Body Non-Glandular trichomes Foot Glandular trichomes Trichomes or hairs e.g. Senna Unbranched Unicellular Branched e.g. Lavander Non- Glandular Unbranched Shaggy hair Multicellular e.g. Cumin Trichomes Branched (Hairs) e.g.Tobacco UnBranched Unbranched Unicellular stalk Glandular Digitalis Branched Branched stalk with unicellular head Hyoscyamus  Ground Tissue Parenchyma Collenchyma Schelernchyma Living Cells Non-living at Living cells maturity thin cellulosic walls thick primary Thick walled cellulosic walls lignified cells Wide intercellular No intercelllar Fibers and spaces spaces sclerides Storage , respiration, Enable the plant to photosynthesis Hard elastic secondary resist pressure, Have the ability to walls to provide flexible stretching and bending differentiate to other cell support withourt damage types. (Mechanical support)  Sclereides Circular in shape. The wall is thick and lignified. Fibers They are elongated cells with tapering ends and lignified secondary walls Ground Tissue  Mesophyll It is differentiated to palisade and spongy tissue. A. Palisade layer  One or more layers of columnar cells perpendicular to the epidermis with narrow intercellular spaces.  Upper palisade may form a continuous layer over the midrib as in Senna or a discontinuous layer as in Datura.  The mesopyll may be either isobilateral or dorsiventral B. Spongy Tissue large intercellular spaces.  Vascular Tissue  Vascular tissue is a complex tissue  There are two types of vascular tissue:  Xylem  Phloem Vascular tissue may be scattered in ground tissue or regularly arranged forming a ring. Scattered Regularly arranged (Monocots) (Dicots)  Vascular Bundles Xylem Phloem  Water conducting  Food (Organic material) conducting  Vessels are made of dead cells  Elements are made of living cells  One direction from soil to leaves  Bidirectional flow  Phloem vessels have NO lignified  Vessels have lignified walls walls  End walls disappear completely  End walls do not disappear completely  Have pits (Pitted walls)  Have plasmodesmata  Composed of  Composed of Xylem parenchyma Phloem parenchyma Vessels Sieve Tubs Tracheids Companion cells  Xylem Vascular Bundles Phloem  Composed of :  Composed of :  The sieve tubes formed from vertical  Tracheids (more like a fiber) series of elongated cells Lignified and variously thickened and interconnected by perforation in their pitted cell wall walls in areas known as sieve plates  Vessels (major conducting elements)  The companion cell or derived from vertical series of cells, plasmodesmata is intimately dissolution of the wall make continuous associated with sieve tube structurally and functionally. The companion cell is tube. (Lignified and pitted) characterized by its dense protoplast and well developed nucleus and thin cellulose wall. Xylem Phloem Introduction to Leaves Transverse section of a leaf Transverse section (T.S.) of a leaf Summary Slide Thank You Ppt