plant structure

• Waxy cuticle

  • prevents water loss by evaporation
• Upper Epidermis

  • No chloroplasts, transparent so sunlight can pass through
• Palisade layer

  • applied to maximise photosynthesis, tall and thin for lots of photosynthesis , most chloroplasts
• Spongy layer

  • gas exchange
• Guard cell

  • open and close stomata
• Leaf vein

  • transports water up the plant
• Phloem vessel

  • Carries sucrose made by photosynthesis up and down the plant
  • Living cells arranged - end with cytoplasm
  • Sieve like barrier to pass between cells

  
• Phloem - sucrose is transported:

  • from sources in the root to sucrose to sinks in the leaves in winter
  • from sources in the leaves to sucrose to sinks in the root in summer
• Stoma

  • allows CO2 in and oxygen out

  
• Xylem

  • carries water and minerals from roots to up the plant
  • Long dead cells arranged end to end to form vessels
  • no cytoplasm
  • Impermeable to water
  • Tough woody walls
• Translocation

  • transport of dissolved material within a plant
  • e.g. phloem transport sucrose and amino acids from leaves to the rest to the plant
• Guard cells

  A) guard cells

  B) vacuole

  C) nucleus

  D) chloroplasts

  E) cell wall

  F) stoma

  
• A guard cell's inner cell wall is thicker than their outer one
• Water and minerals plants need are absorbed through their root hairs
• Absorption takes place in this area just behind the root tip, this area is covered in root hairs

  Each hair is a projection of an epidermal cell on the outside of the root
• Root hairs greatly increase surface are of the root which increase the rate at which water and minerals can be taken into the plant

  A) cellulose cell wall

  B) cell membrane

  C) vacuole

  D) nucleus

  E) cytoplasm

  
• What causes the stomata to open?

  Guard cells become turgid because water moves in by osmosis - they bow outwards and open the stomata. Flaccid cells meet in the middle, closing the stomata
• Structure of a leaf - labels

  A) waxy cuticle

  B) upper epidermis

  C) palisade layer

  D) spongy layer

  E) lower epidermis

  F) guard cells

  G) stoma

  H) xylem

  I) phloem

  J) leaf vein