Epidermal Tissue System – Class 11 | Chapter – 6 | Short Notes Series PDF

Epidermal Tissue System: A group of tissues performing a common function irrespective/ regardless (different) of their position and origin is called as epidermal tissue system. Epidermal tissue system is also known as, ‘dermal tissue system’.

  • It forms the outermost protective covering of various plant organs which remains in direct contact with the environment.
  • It originates from the outermost layer of the apical meristem.
  • It performs various functions including protection, absorption, excretion, gaseous exchange, restriction of transpiration, secretion etc.

Epidermal Tissue System Diagram

Epidermal Tissue System Components

1. Epidermis
2. Cuticle
3. Stomata
4. Trichomes

1) Epidermis-

  • It is uniseriate in most of the plant organs but in some plants it may be multilayered. e.g. Ficus, Nerium.
  • Its cells are parenchymatous and compactly arranged. The outer tangential walls are usually thicker as compared to inner walls.
  • Each cell has a large central vacuole & a peripheral thin cytoplasm. They may contain chloroplasts, anthocyanin pigments, tannins, oils and crystals etc.
  • Some upper epidermal cells in some monocot leaf become larger, thin-walled, have vacuoles & are called bulliform cells. They play an important role in the folding of leaves during deficiency of water e.g. Grasses.
  • In aerial roots of epiphytes, the multiple epidermal cells are modified to velamen which absorbs moisture from the atmosphere.

2) Stomata-

  • Stomata are minute pores in the epidermis. Each pore is surrounded by two kidney-shaped cells, called guard cells.
  • Guard cells are dumb-bell shaped in the members of the Gramineae family (Monocots).
  • Guard cells contain chloroplasts. The inner wall of the guard cell is thickened.
  • Guard cells in some cases are surrounded by another group of less modified epidermal cells called subsidiary cells.
  • All these components together are termed as stomatal apparatus.
  • Usually, there is a large air cavity below each stomata. It is called a substomatal cavity.
  • Stomata are absent in roots, underground parts and submerged hydrophytes.
  • In xerophytes stomata are sunken in grooves due to which transpiration is greatly reduced, stomata are embedded in Pinus.
  • The function of stomata is the exchange of gases and control of transpiration.

3) Cuticle and Wax-

  • Cutin is a fatty substance deposited over the outer surface of epidermal cells in the form of a separate layer which is called the cuticle.
  • The cutinised walls are less permeable to water. The impermeability depends upon the thickness of the cutin.
  • Cuticle is-
    – thick in xerophytes,
    – thin in mesophytes and
    – absent in submerged parts of hydrophytes.
    – It is also absent in underground parts.

4) Trichomes:

  • They are found on the stems of plants.
  • They are multicellular structures, unlike root hairs.
  • They are found in two different types, i.e. scales and hairs.
  • These could be branched (scales) or unbranched (hairs).
  • These might be stiff or soft in nature.
  • These can also act as secretory cells.
  • They help in preventing water loss due to transpiration.

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By Team Learning Mantras