Plant Organisation

• Xylem:

  • one way flow
  • no end walls between cells
  • walls strengthen by lignin (lignified)
  • no living material
  • hollow
  • allows rapid mass transport of water
• Phloem:

  • two way flow
  • Cells have sieve plates
  • Stay alive because of companion cells that help them respire
  • no nucleus
  • Sieve plates function as valves for two way flow
• Translocation: movement of glucose
• Transpiration: movement of water (as one water molecule leaves another enters creating a constant stream - cohesion tension theory)
• Aphids:

  • feed off plant sap
  • have a stylet that is inserted into he plant sieve
  • it is then cut off after feeding has commenced to sample the sap
  • the severed stylet stays in the plant so sap continues to flow
• Transpiration is faster on dry, warm and windy days because the gradient is steeper
• Photosynthesis symbol equation:

  • Glucose id C6H12O6
  • A big 6 is on all other reactants / products except glucose
• Guard cell: controls the opening and closing of the stomata
• Stomata: Allows water vapor and gases to move into and out of the leaf
• Xylem: Water and dissolved mineral ions from the roots to the leaves
• Phloem: Carries dissolved sugars from the leaves around the plant
• Epidermis: Covers the surface and protects them secreting a waxy substance that waterproofs the leaf
• Palisade Mesophyll: Tissues containing tightly packed chloroplasts for photosynthesis
• Spongy Mesophyll: Tissues containing some chloroplasts but also has big air spaces allow gases to diffuse in and out of the leaf easily
• Waxy cuticle: Waterproofs the leaf
• Palisade Cell Adaptations:

  • lots of chloroplasts for photosynthesis
  • continuous layers to absorb as much light as possible
  • large permanent vacuole keeps the cell rigid for osmosis
• Xylem Adaptations:

  • dies when lignin builds in spirals to strengthen the cell
  • Cell walls die to form a long hollow tube
  • Spirals of lignin builds so the cell can withstand the pressure of the water
• Phloem Cell Adaptations:

  • Don't become lignified and die
  • Dissolved sugars can move up and down depending on where they are needed
  • Cell walls break down to form sieve plates
  • Supported by companion cells with lots of mitochondria to keep the phloem cells alive
• Guard Cells & Stomata Adaptations:

  • Guard cells will become swollen with water to open the stomata
• Root Hair Cell Adaptations:

  • increased surface area
  • large permanent vacuoles
  • lots of mitochondria for energy for the active transport if nutrients and minerals