Biology

• What is the role of xylem tissue?

  transports mineral ions and water (up)
• What is the role of phloem?

  Transports dissolved sugars.
• Adaptations of xylem tissues:

  • made of dead cells
  • cell wall made of lignin
  • cross-walls are absent
  • no cytoplasm
  • flow is upwards
• Adaptations of phloem tissue:

  • made of living cells
  • cell wall made of cellulose
  • has sieve plates
  • flow is upwards and downwards
  • tissue also has companion cell
• What do root hair cells absorb?

  - Water by osmosis

  • Mineral ions by active transport
• Palisade mesophyll contains lots of chloroplasts to absorb light for photosynthesis.
• Glucose is made in the leaves during photosynthesis.
• Stomata open when it's hot, humid or dark so that water can evaporate from the leaf surface which cools the plant.
• Glucose and other dissolved sugars are transported to other parts of the plant in the phloem - this is called translocation.
• What does the epidermal layer do?

  - covers the surface and protects them and secretes a waxy substance to prevent waterloss.
• What does the palisade mesophyll do?

  - contains lots of chloroplasts

  • contain chlorophyll which absorbs light energy for photosynthesis
• What is the role of spongy mesophyll?

  • contains chloroplasts for photosynthesis.
  • Have big air spaces and a large surface area for the diffusion of gases.
• Adaptations of the meristem:

  • found at the growing tips of roots and shoots.
  • made up of rapidly dividing cells.
  • the dividing cells grow and differentiate into all the types of cells needed.