Epidermis Lab

Lab.3 Slides Prepared: 1- Syringa leaf c.s. 2- Zea leaf c.s 3- Pinus leaf c.s. 4- Ficus leaf c.s 5- Orchid root c.s Epidermis Fresh specimen 1) Any leaf of crucifers 2) Ranunculus leaf (the best) or Cucurbita leaf or Chenopodium leaf 3) Carnation leaves 4) Grass leaves 5) Pelargonium ( stem and leaves) plant 6) Lavender leaf 7) Malva leaf 8) Ice plant leaf 9) Olive leaves 10) Cotton fruits with seeds 1 Lab.3 Epidermis  Epidermis is the outermost layer (or rarely layers) of cells in the primary state of growth, during secondary growth it is replaced by periderm.  It is a complex tissue composed of several types of cells.  It is derived from protoderm (meristematic) cells.  Epidermal cells are living, tubular or elongated.  The outer surface of epidermis is usually covered with separate layer of cuticle, which varies in thickness from plant to plant.  Its functions are diverse including protection, gas exchange, defense against herbivores and pathogens and decreasing rate of transpiration. Types of epidermis : During your examination for the epidermal cell, note the shape and size of epidermal cells, and note if there is a difference between upper and lower epidermis. Notice also the shape of guard cells (mostly kidney shaped, dumbbellshaped in grass leaves) 1) uniseriate epidermis (one layer of cells in thickness) 1-Study prepared slide of Syringa (dicot leaf) leaf c.s Notice the upper and lower epidermis , stomata (pore), guard cells, substomatal cavity and subsidiary cells (stomatal complex) 2- Study prepared slide of Zea leaf c,s. (monocot leaf) Notice the epidermis, stomata, guard cells and specialized epidermal cells called bulliform cells (enlarged bubble-like cells). 3- Study prepared slide of Pinus leaf c.s. (gymnosperm leaf) Notice the thick walled epidermis (may be thick secondary cell wall) , sunken stomata, guard cells and subsidiary cells (specialized epidermal cells) 2 2) Multiple epidermis (Multiseriate) more than one layer of cells. present in leaves and velamen of aerial root. 4- Study prepared slide of Ficus lea f c.s Notice the multiple upper and lower epidermis, stomata, cystolith crystal in lithocyst cell. 5- Study prepared slide of Orchid rooth c.s Notice the multiple epidermis in velamen Types of stomata: -To study types of stomata you need to make a paradermal section in fresh leaves of many plants (by making strips or peels of epidermis of fresh leaves) -Based on the arrangement of subsidiary cells around stomata, stomata could be classified into the following types a) Anomocytic with irregular cells and no subsidiary cell 6- Make a paradermal section in Chenopodium leaf (or Ranunculus leaf or Cucurbita leaf) b) Anisocytic unequal celled (3 subsidiary cells, one smaller than the other two) 7- Make a paradermal section in any Crucifer leaf (or Petunia or Kalancoe leaves) Notice the epidermis in dicot plant in this surface view too. c) Diacytic cross celled (2 subsidiary cells) 8- Make a paradermal section in Dianthus (carnation) leaf. d) Paracytic parallel celled 9- Make a paradermal section in bean leaf and 10-any monocot leaf notice in addition to stomata, surface view of the epidermis, cork cells and silica cells (specialized epidermal cells). Trichomes: Variable appendages of the epidermis, with different functions as removing salts from leaf tissue and defend the plant against insects. Types of trichomes 1) Hairs: could be unicellular or multicellular of a single row of cells or many rows of cells, could be glandular 3 (with unicellular head or multicellular head) or nonglandular. 11- Peel the epidermis of Pelargonium leaf petiole and notice the unicellular hair. -You may use the dissecting microscope if you couldn't peel the epidermis. 12- Study the epidermis of Pelargonium stem and notice the bicellular hair. 13- Study the epidermis in Pelargonium leaf and notice the multicellular hairs 14- Study the epidermis in Lycopersicon (tomato)leaf to see the uniseriate multicellular hairs. 15- Study the epidermis in Malva leaf and notice stellate hairs (branched –star shaped) 16- Study the Dendroid hairs (tree like hairs) in the epidermis of Verbascum plant or lavender leaf. 2) Scales or peltate hairs. 17- Prepare a scrub of olive leaf and notice those scales 3) Water vesicles (enlarged epidermal cells with hemispheres or ovoid shape) 18- Try to make a c.s. in ice plant leaf petiole to notice those vesicles. You may face a difficulty in this preparation so you can study the whole leaf using the dissecting microscope. 4) Stamen hairs, notice those hairs in flowers of 19-snapdragon 5) Root hairs notice the root hairs in any 20-fresh plant. 6) Papillae small hair-like epidermal cell projection. Present on petals of 21-flower. 7) Study a specimen for cotton fruit with seeds inside, notice the the epidermal hairs of cotton seed coats that are commercially called fibers. 4