Organisation of Plant tissue


Organisation of Plant tissue

Plant tissue
Meristematic tissue Permanent tissue
  • Apical meristematic tissues
  • Lateral meristematic tissues
  • Epidermal tissues
  • Ground tissues:
    •          Parenchyma tissues
    •          Collenchyma tissues
    •          Sclerenchyma tissues
  • Vascular tissues:
    •          Xylem tissues
    •          Phloem tissues

Types of permanent tissues and their functions:


1. Epidermal tissues:

  • Epidermal tissues layer is at the outermost surface of stems, leaves and roots of young plants.
  • Epidermal cell walls which are exposed to the air have a waxy and waterproof layer called the cuticle.
  • The cuticle reduces loss of water through evaporation (transpiration) and protects the leaf from mechanical injuries and pathogens.

2. Ground tissue:

a)   Parenchyma tissues
  • Paracenchyma tissues are the simplest living cells and do not undergo differentiation.
  • They have the thinnest cell walls.
  • Parenchyma tissues are always in a turgid state providing support and maintaining the shape of herbaceous plants.
  • Involved in photosynthesis, helping in the storage of starch and sugar and involved in gaseous exchange.
  • Involved in the repair and regeneration of plant tissue as well as in the vascular system.
b)   Collenchyma tissues
  • Collenchyma tissues are made of living cells which mature into cells that are flexible.
  • Have cell walls made of pectin and hemicellulose.
  • Their cell walls are thicker than parenchyma tissues.
  • Provide mechanical support and elasticity to plants.
c)   Sclerenchyma tissues
  • Sclerenchyma tissues consist of dead cells when they are matured.
  • Their cell walls are the thickest among the three ground tissues.
  • Provide support and mechanical strength to the parts of matured plants.
  • These tissues also help in the transport of water and nutrients in plants.

3. Vascular tissue:

a)   Xylem
  • The xylem is made up of dead cells without cytoplasm
  • The cell wall of the xylem contains lignin.
  • Consists of xylem vessels that are elongated, hollow and connected from its roots to the leaves.
  • This enables xylem to transport water and mineral salt to all parts of a plant.
b)   Phloem
  • Phloems are made of companion cells and sieve tubes.
  • Made of living cells, which are the sieve tubes with the presence of cytoplasm.
  • The sieve tubes do not have organelles such as nucleus and ribosome as they decompose at the maturity stage.
  • Phloems consist of sieve tubes arranged from end to end forming elongated and continuous tube structures.
  • Phloems transport sugars produced from the photosynthesis from the leaves to storage organs such as roots, fruits and tubers.