lesson 3

• What is the water potential of pure water?

  0 kPa
• How does adding solute affect the ability of water to move?

  It makes it harder for water to move
• In what direction does water move in relation to water potential?

  From high to low water potential
• What is the name of plant cells full of water?

  Turgid cells
• What are plant cells called when there is a water shortage?

  Plasmolysed cells
• What process in plant cells requires water?

  Photosynthesis
• What percentage of water taken up by the plant is used for photosynthesis?

  Approximately 1%
• What is the main process that leads to most of the water being taken up by plants?

  Transpiration
• What is the path of water in a plant?

  1. Root hair cell
  2. Cortex
  3. Endodermis around vascular tissue
  4. Xylem In root, stem then leaf
  5. Air spaces in leaf
  6. Stomata
• How does water enter the root from the soil?

  By osmosis down water potential gradient
• Through which structures does water pass to enter the root hair cell?

  Cell wall and plasma membrane
• Why does water move into the root hair cell?

  The cell cytoplasm has lowered water potential
• What are the three pathways water takes through plant tissues?

  • Apoplast pathway
  • Symplast pathway
  • Vacuolar pathway
• Which pathway offers the least resistance to water movement in plants?

  Apoplast pathway
• What does water travel along in the apoplast pathway?

  Cellulose cell walls
• What does water travel along in the symplast pathway?

  Cell cytoplasm and plasmodesmata
• What does water travel along in the vacuolar pathway?

  From vacuole to vacuole
• Which is the external surface that contact internal medium?

  Endodermis
• Which is the external surface that contacts external medium?

  Epidermis
• How does water move in response to the endodermis secreting ions into the xylem?

  Down the water potential gradient
• What effect does the endodermis secreting ions into the xylem have?

  Lowers the water potential
• How do minerals enter the xylem?

  Actively transported
• How does water move after minerals are actively transported into the xylem?

  By osmosis
• What is the function of the Casparian strip?

  Prevents water using apoplast pathway
• What substance is the Casparian strip made of?

  Suberin
• What does the presence of the Casparian strip force water to do?

  Enter the cytoplasm
• What process drives water into the root by osmosis?

  Active transport of ions
• How far can root pressure push water up a stem?

  A few metres
• How does water rise in xylem tubes via capillary action?

  By adhering to the sides of tubes
• What causes guttation at night?

  Root pressure
• Why does water rise higher in finer tubes during capillary action?

  The effect is greater
• What process draws water up the xylem as a continuous column?

  Transpiration
• How is the water column maintained in the xylem?

  Hydrogen bonds between water molecules
• What does the pull exerted by transpiration produce in the xylem?

  Tension
• What is the name for water molecules forming hydrogen bonds?

  Cohesion
• From where is water drawn to mesophyll cells in the leaf?

  Leaf xylem
• Where does water move from mesophyll cells?

  Intercellular spaces
• How does water leave the plant and enter the atmosphere?

  Via stomata down the potential gradient
• Why do stomata open?

  Allow gaseous exchange