Plant tissues, topic 2

• Tissue


  A group of cells that have a similar structure and function
• Types of plant tissue


  • Epidermal
  • Palisade mesophyll
  • Spongy mesophyll
  • Xylem
  • Phloem
  • Meristematic
• Epidermal tissue


  • Covers the whole plant
  • Covered with a waxy cuticle
  • Helps to reduce water loss by evaporation, as the waxy cuticle prevents water from moving out
• Palisade mesophyll tissue


  • Found underneath the epidermal tissue
  • Has lots of chloroplasts (photosynthesis takes place within these structures)
  • Having many chloroplasts means photosynthesis can happen rapidly
  • They are positioned at the top of the leaf so they receive lots of light
• Spongy mesophyll tissue


  • Found underneath the palisade mesophyll
  • Has lots of air spaces
  • This allows gases to diffuse in and out of cells
• Xylem


  • Found in the roots, stems and leaves
  • Made up of dead cells joined together, creating a continuous tube
  • Strengthened with a substance called lignin, but this has some holes in it along the tube called bordered pits
  • Allows the movement of water and mineral ions from the roots to the stem and leaves, where it evaporates and leaves the plant (transpiration stream)
  • Lignin makes it strong and waterproof, so water will not leave except at bordered pits, allowing minerals to go to specific places in the plant
• Phloem


  • Found in the roots, stems and leaves
  • Elongated cells with holes in the cell walls (the end walls are now called sieve plates)
  • Many organelles from the cells are removed so cell sap can move through
  • Food substances can be moved in both directions, from the leaves where they are made for use, or from storage (underground) to parts of the plant that need it
  • This process is called translocation
• Meristematic tissue


  • Found at the tips of shoot and roots
  • It is able to differentiate into different types of plant cell
  • This allows the plant to Grow