3.1.3

• vascular bundle


  contains xylem and phloem
• Root structure

  A) epidermis

  B) cortex

  C) phloem

  D) xylem

  E) cambium

  F) endodermis

  
• structure of the stem

  A) xylem

  B) cambium

  C) phloem

  
• structure of the leaf

  A) xylem

  B) phloem

  
• structure of a leaf layers

  A) waxy cuticle

  B) upper epidermis

  C) palisade mesophyll

  D) spongy mesophyll

  E) lower epidermis

  F) stoma

  G) guard cells

  
• what does the cambium contain


  meristematic tissue
• what is the purpose of the phloem

  transport organic fluid
• what is the purpose of the xylem


  transport water and dissolved ions
• phloem structure

  A) companion cell

  B) sieve tube element

  C) plasmodesmata

  D) sieve end plate

  
• companion cell in phloem


  contains many mitochondria providing ATP for active transport
• sieve tube element phloem


  living cell with few organelles

  ends of cell contain holes to assist in fluid transport
• xylem structure

  A) lignin

  B) no end cell walls

  
• xylem cells


  dead hollow cells strengthened by waterproof lignin
• how is water transported from the soil into the plant root cell

  absorbed via osmosis as root hair cells have a thin cell wall and large surface area
• how does water travel from root hair cells into the xylem


  symplast or apoplast pathways
• symplast vs apoplast pathways

  A) apoplast

  B) symplast

  C) casparian strip

  
• symplast pathway


  water moves via osmosis through cytoplasm and plasmodesmata. each successive cells cytoplasm has a lower water potential so osmosis can occur down a gradient
• apoplast pathway


  water moves via cohesive forces between cell walls. The water molecules form hydrogen bonds making a continuous stream. This is faster as their is little water resistance from the cell wall but this is stopped by the casparian strip that is hydrophobic forcing the water to enter the cells before the xylem
• xerophytes


  adapted to reduce water loss and live in arid environments
• adaptations by xerophytes


  curled leaves , hairs , sunken stomata - traps moisture increasing humidity and water absorbed

  thick cuticle - reduces evaporation

  long root network - large surface area for water absorption
• hydrophytes


  adapted to increase water loss and live in water
• hydrophyte adaptations


  short roots - does not need to reach far for water

  no waxy cuticle , permanently open stomata , stomata on surface of leaf- allows for evaporation

  large wide leaves on the surface of the water - photosynthesis ( use up water )
• transpiration


  the loss of water vapour from the stomata via evaporation
• factors affecting transpiration


  light intensity

  temperature

  humidity

  wind
• light intensity


  positive correlation with transpiration

  more stomata open meaning there is a greater surface area for evaporation
• temperature


  positive correlation with transpiration

  water molecules have a greater kinetic energy so easily turn to vapour and leave
• humidity


  negative correlation with transpiration

  the greater the water potential of the environment the reducing the water potential gradient
• wind


  positive correlation with transpiration

  removes water vapour from air surrounding plant maintaining steep water potential gradient
• how is transpiration rate measured


  potometer
• cohesion


  water molecules are polar allowing them to form hydrogen bonds between the molecules creating a continuous column of water
• adhesion


  due to waters polarity it can form bonds with other molecules around it
• Adhesion in the xylem


  bonds formed with lignin
• root pressure


  the more liquid in the roots the greater the volume of liquid and the greater the pressure in the roots that forces the water upwards ( positive pressure )
• stages of cohesion tension theory


  1. transpiration - water evaporates out of stomata reducing water volume and pressure in leaves
  2. negative pressure - water is pulled into the leaves and xylem to replace the water lost
  3. cohesion - a column of water is pulled up the xylem
  4. adhesion - water pulls the walls of the xylem increasing the volume of water moved upwards as even more adhesion occurs
  5. roots pressure - Water is pushed upwards
• translocation requires


  ATP as it involves co transport
• what is translocation


  the mass flow of substance from source of production to sink of use
• example of translocation


  movement of sucrose and amino acids to respiring tissue where they are assimilated
• assimilated


  taken up and used
• source to sink explanation


  • source cells produce sucrose via photosynthesis lowering their water potential
  • water moves into the source cell via osmosis from the xylem increasing hydrostatic pressure
  • sink cells assimilate sucrose increasing their water potential
  • water moves out the sink cell via osmosis to the xylem decreasing the hydrostatic pressure
  • the hydrostatic pressure gradient forces sucrose to move to the sink cell via the phloem
• source to sink diagram

  A) low water potential

  B) high hydrostatic pressure

  C) high water potential

  D) low hydrostatic pressure