Transport in plants

• 6CO2 = 6H2O + light —— C6H12O6 +6O2

  carbon dioxide +water +light —— glucose + oxygen
• chloroplast 


  grana - stacks of thylakoid provide increased SA for first reaction in photosynthesis take place (light dependant stage)

  stroma - fluid filled space full of enzymes for second reaction in photosynthesis to take place (light independent stage )

  circular DNA - store of genetic information - instructions to code protein

  small ribosomes - site of protein synthesis
• gas exchange in plants

  a thin flat shape provides a large surface area

  many small pores called stomata (mainly in the lower epidermis ) allows gases to diffuse into and out of the leaf

  numerous interconnected airspaces allow gases to reach the cells
• Mass transport 


  Mass transport is the movement of a fluid travelling in one direction through a series of tubes from one or more exchange surfaces to cells
• What is the primary mechanism by which water moves up the xylem?

  Transpiration pull
• How does cohesion contribute to water movement in the xylem?

  Cohesion sticks water molecules together in a continuous chain
• What role does adhesion play in the movement of water in the xylem?

  Adhesion allows water molecules to stick to the xylem wall
• What is the theory that explains the movement of water in the xylem?

  The theory of movement is called cohesion tension
• How are minerals and ions transported into root hair cells?

  Minerals and ions are actively transported into the root hair cell
• What effect does the active transport of minerals have on water potential in root hair cells?

  It lowers the water potential in these cells
• How does water move from the soil into the roots?

  Water moves into the roots from the soil via osmosis
• What is the direction of water movement during osmosis in this context?

  Water moves from higher to lower water potential
• What happens to water in the xylem as it moves into leaf cells?

  Water moves out of the xylem and into leaf cells
• How does the heat from the sun affect water in leaf cells?

  The heat from the sun evaporates the water from these cells
• Where does the evaporated water go after leaving the leaf cells?

  It diffuses out of the open stomata into the atmosphere
• What is the process of water vapor leaving the leaf called?

  Transpiration
• Transpirations - the evaporation of water from moist cell walls followed by the diffusion of water vapour from internal air spaces of the leaf to atmosphere via stomata
• transpiration

  1. water moves out of the xylem by osmosis down a water potential gradient
  2. water continues to move through neighbouring mesophyll cells by osmosis down the water potential gradient
  3. cell lose water to the air spaces by evaporation due to the heat supplied by sun
  4. the water vapour will then diffuse out the stomata down the water vapour gradient
• Factors effecting transpiration 


  Light intensity - light has heating effect so increases evaporation and transpiration

  temperature - increases evaporation of water
• potometer experiment

  cut shoot underwater

  place shoot in the potometer under water

  allow time for the plant acclimatise to its surroundings

  open tap on the reservoir to position an air bubble at the end of the scale

  keep plant in constant environmental conditions

  record movement of bubble over specified time intervals and calculate ate movement

  reset bubble and take more readings
• water movement in the xylem

  1. Water is lost from leaves via transpiration this reduces the water potential in the cells
  2. water molecules are down up the xylem as a result of cohesion between water molecules
  3. a column of water is therefore pulled up the xylem this is called transpiration pull
  4. transpiration pulls put the xylem under tension a negative pressure
  5. this combination of cohesion and tension continues to pull the water column up the xylem
• adhesion - the interaction of the water molecules with the wall of the xylem

  cohesion - water molecules form hydrogen bonds between one another and therefore stick together forming a column of water
• translocation in the phoelm

  1. active transport transports solutes into the phloem by the companion cell
  2. lowers water potential inside the sieve tubes and water enters the tubes by osmosis
  3. this creates a high (hydrostatic pressure) mass movement towards the sink
  4. solutes / sugar are used up for storage to starch orin respiration
  5. sugars are actively transported out of the phloem increases the water potential water leaves by osmosis
  6. this lowers the hydrostatic pressure
  7. pushes solutes along the sieve tubes from the source to the sink