1 : Plant tissues

• Meristematic tissues are actively dividing through mitosis
• Permanent tissues are matured tissues which have experienced or are experiencing differentiation
• There are three types of permanent tissues :

  1. Epidermal tissues
  2. Ground tissues
  3. Vascular tissues
• Epidermal tissues layer 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 cuticle
• The cuticle reduces loss of water through evaporation, protects the leaf from mechanical injuries and pathogens
• Guard cells control the opening of the stoma
• Root hair cells increase the surface area of the root for water and mineral salts absorption
• Parenchyma tissues are simplest living cells
• Parenchyma tissues do not undergo differentiation
• Parenchyma tissues have the thinnest cell walls
• Parenchyma tissues are always in a turgid state providing support and maintaining the shape of herbaceous plants
• Collenchyma tissues are made of living cells which mature into cells that are flexible
• Collenchyma have cell walls made of pectin and hemicellulose
• Collenchyma tissues cell walls are thicker than the parenchyma tissues
• Sclerenchyma tissues consist of dead cells when they are matured
• Sclerenchyma tissues have the thickest cell walls
• Sclerenchyma tissues provide support and mechanical strength to the parts of matured plants
• The cell wall of xylem contains lignin
• Xylem is made up of dead cells without the cytoplasm
• Phloems are made of companion cells and sieve tubes
• Apical meristem tissue is located at the tips of plant shoots and roots
• Lateral meristem tissue consists of vascular cambium and cork cambium