Transport in plants

• Why do plants need transport systems?

  • Metabolic demands
  • Size - very tall plants etc
  • SA:V; roots have small ratio cannot rely on roots alone
• Explain the structure of a xylem vessel tissue

  • Non-living tissue
  • made up of dead cells
  • long and hollow, no cytoplasm
  • fuse together end to end
  • thick, lignified cell wall
  • Large lumen
• What’s the function of a xylem vessel?

  Transport of water, mineral ions and support
• describe the flow of materials in a xylem?


  up from the roots, to the shoots and leaves
• What’s a think-walled xylem parenchyma

  packed around xylem vessel, stores food and contains tannin deposits
• what’s tannin


  bitter chemical in xylem parenchyma n protects the plant tissue from attacks from herbivores
• what does the lignin walls proive

  mechanical strength, impermeable to water
• how can lignin be arranged in a xylem vessel

  rings, spirals or solid tubes with many unlignified bordered pits
• what does lignin help to do

  prevent the xylem from collapsing during the transpiration pull, reinforce
• Describe the structure of a phloem plant

  • living tissue
  • main transporting vessels - sieve tube elements
  • sieve tubes joined end to end making long, hollow structure
  • areas between cells - perforated walls - sieve plates
  • no nuclei, filled with phloem sap
• what are closely linked to sieve tube elements

  companion cells, linked by many plasmodesmata
• what’s plasmodesmata

  microscopic channels through cellulose cell walls, link their cytoplasm of adjacent cell walls
• describe companion cells

  • linked to sieve tube elements
  • maintain all their organelles/nucleus
  • very active cells, ‘life support system’ for sieve tube elements
• phloem tissue contain supporting tissues, fibres and sclereids (cells with very thick cell walls)
• What’s the function of a phloem tissye

  To transport food in the form of organic solutes, supplying the cells with sugars, amino acids for cellular respiration, synthesis of other molecules
• how does organic solutes get transported by the phloem

  can go up or down the plant, get material from the leaves (where products r made by photosynthesis) to around the plant
• What are root hair cells exchange surfaces in plants, water taken into the body from the soil
• adaptations of root hair cell

  • long and thin
  • microscopic size, penetrate easily between soil particles
  • each hair has a large SA:V ratio
  • each hair has thin surface layer, quick diffusion and osmosis
  • maintains water potential gradient: concentration of solves in cytoplasm of RHC and soil water
• The soil concentration outside of root hair, low concentration of dissolved mineral ions, HIGH water potential. Root hair cell has lots of different solvents: sugars, mineral ions, amino acids water potential in the cell is LOW. Water moves into RHC by osmosis
• Where does the water from the root hair cell go into next

  To the xylem in two pathways: apoplast and symplast pathway
• Describe the symplast pathway

  the water will travel through the cytoplasm of cell connected by plasmodesmata,