Epidermis

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Chapter 2 stpm biology !

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Epidermis

  1. 1. Epidermis STRUCTURE OF CELLS AND ORGANELLES
  2. 2. We will take a look into these :- Distribution Structure of epidermis Functions
  3. 3. What is epidermis ? Epidermis or epidermal tissue is a single- layered group of cells that covers plants leaves, flowers, roots and stems.
  4. 4. Distribution One cell thick covering the entire plant . Do not have chloroplast but transparent .
  5. 5. Structure Epidermis is usually closely packed, without intercellular spaces or chloroplasts. The outer walls, which are exposed to the atmosphere and usually thickened, and may be covered by a waxy, waterproof cuticle which are made up of cutin. Apart from the normal epidermal cells there are also stomata in the epidermis of leaves and stem. A stoma is an opening (pore) which is bounded by two bean-nshaped cells called guard cells . The guard cells differ from normal epidermal cells in that they have chloroplasts and the cell walls are thickening unevenly; the outer wall is thin and the inner wall (nearest the opening) is thick. The thin-walled epidermal cells of roots give rise to root hairs. [Hair- like outgrowths may also be found in the epidermis of leaves and stems.] The root hair also known as trichomes.
  6. 6. Example of epidermis tissue in plant cell
  7. 7. Functions the epidermal cells protect the underlying cells, the waxy cuticle prevents the loss of moisture from the leaves and stems, the transparent epidermal cells allow sunlight (for photosynthesis) to pass through to the chloroplasts in the mesophyll tissue, the stomata of leaves and stems allow gaseous exchange to take place which is necessary for photosynthesis and respiration, water vapour may be given off through the stomata during transpiration, the root-hairs absorb water and dissolved ions from the soil.
  8. 8. Trichomes in epidermis cell

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