transport in plants

• Adaptations of hydrophytes


  Many stomata on the top surface on the leaf to maximise gas exchange

  No waxy cuticle

  leaves are flat and thin to decrease diffusion distance and increase SA
• Adaptations of xerophytes


  Rolled leaves to reduce the effect of wind

  hairs to trap moisture around the stomata to decrease the difference in water potential

  sunken stomata - reduce effect of air flow and traps moist air
• Why do plants need transport systems?

  to meet metabolic demands of cells all around the plant

  simple

  Low SA:V

  overcoming large diffusion distances
• how are ions prevented from entering the xylem through the apoplast pathways

  Casperian strips that are impermeable to water in the forces the solution to exit through the plasma membrane which the water would make it through but the ions would be repelled by the hydrophilic charged heads of the membrane
• Why do xylems have pits


  to allow lateral movement of water
• Similarites between xylem and phleom structure

  Both lack nuclei

  both are tubes that transport substances
• Differences between the xylem and phloem structure


  only the xylem contains lignin

  xylem: wide lumen, phloem: narrow lumen

  phloem has sieve plates, companion cells

  xylem has pits
• function of xylem and phloem

  phloem: transporting organic substances from sources to sinks (bidirectional)

  Xylem: transpiration stream
• image of xylem and phloem

  A) Xylem

  B) phloem