Plant. transport

Question 1

function of the phloem

Answer 1

transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem

Question 2

Structure phloem

Answer 2

• The cells are living cells and are not hollow
• Substances move from cell to cell through pores in the end walls of each cell

Question 3

Role of the Xylem

Answer 3

transport water and minerals from the roots to the stem and leaves

Question 4

structure of the xylem

Answer 4

• It is composed of dead cells which form hollow tubes
• Xylem cells are strengthened by lignin and so are adapted for the transport of water in the transpiration stream

Question 5

adaptions of root hair cell

Answer 5

increase the surface area to volume ratio significantly
This increases the rate of the absorption of mineral ions by active transport

high proportion of dissolved minerals and sugars in the cytoplasm (of the root hair cell) give it a low water potential

Question 6

what is the route of water through the plant

Answer 6

root hair cell → root cortex cells → xylem → leaf mesophyll cells

Question 7

transpiration

Answer 7

the evaporation of water from the surface of a plant

Question 8

The process of transpiration

Answer 8

Water moves through XYLEM VESSELS in a continuous transpiration stream from roots to leaves via the stem to replace the water that has been lost due to transpiration

Due to COHESION, the water in the xylem creates a continuous unbroken column

Transpiration produces tension on the water in the xylem vessels

If the rate of transpiration from the leaves increases, water molecules are pulled up the xylem vessels quicker

Question 9

The function of transpiration

Answer 9

1. Transporting mineral ions
2. Providing water to keep cells turgid in order to support the structure of the plant
3. Providing water to leaf cells for photosynthesis
4. Keeping the leaves cool

Question 10

what factors affect transpiration

Answer 10

Air movement
Humidity
Temperature
Light intensity

Question 11

how does air movement affect transpiration

Answer 11

good airflow removes water vapour from air surrounding leaf

sets up concentration gradient between air & leaf, INCREASING water loss

Question 12

how does humidity affect transpiration?

Answer 12

when air is saturated with water vapour, concentration gradient is weaker so LESS water is lost

Question 13

how does light. intensity affect transpiration?

Answer 13

when it’s high, guard cells become turgid and stomata open - MORE water is lost

Question 14

how does temp affect transpiration?

Answer 14

Higher temp - more particles hv more kinetic energy, water molecules evaporate faster, so transpiration at a FASTER rate

Question 15

what does a bubble potometer measure

Answer 15

uptake of water by a stem as a measure of the amount of water that is being lost by evaporation consequently pulling water up through the stem to replace it

Question 16

Investigating the effect of light intensity on transpiration using a bubble potometer

Answer 16

1. Cut a shoot underwater
   To prevent air entering the xylem and place in tube
2. Set up the apparatus as shown in the diagram and make sure it is airtight, using Vaseline to seal any gaps
3. Dry the leaves of the shoot as Wet leaves will affect the results
4. Remove the capillary tube from the beaker of water to allow a single air bubble to form and place the tube back into the water
5. Set up a lamp 10cm from the leaf and Allow the plant to adapt to the new environment for 5 minutes
6. Record the starting location of the air bubble and Leave for 30 minutes
7. Record the end location of the air bubble
8. Change the light intensity
9. Reset the bubble by opening the tap below the reservoir and Repeat the experiment
10. Calculate the rate of transpiration by dividing the distance the bubble travelled by the time period
11. The further the bubble travels in the same time period, the greater the rate of transpiration

Question 17

what are the limitations of this investigation?

Answer 17

The potometer equipment has a leak

The plant cutting has a blockage

The potometer has shown no change during the experiment