Transport In Plants Weak Areas

Question 1

State one similarity and two differences between the structure of the xylem and phloem.

Answer 1

Similarities:
-both made of cells joined end to end
- both sieve tube cells and xylem vessels lack nuclei
- both are complex tissue

Differences:
- xylem is made of a continuous column whereas ph,one is made from sieve tube elements
- xylem is lignified whereas phloem is not

Question 2

What are the pores called in dicotyledonous plants? What is the function of them in the xylem?

Answer 2

Bordered pits - lateral movement of water

Question 3

Describe one practical precaution when using a potometer that should be used.

Answer 3

Keep the screw clip closed to prevent the entry of water whilst measuring the rate of water uptake

Keep named abiotic factor controlled - affects the rate of transpiration

Don’t allow air to enter the cut end of the shoot to allow the continuous flow of water

Question 4

Plan an investigation into the rate of transpiration in two species of plants that would allow valid data to be collected.

Answer 4

Cut a shoot underwater to prevent air from entering the xylem (cut at a slant to increase the surface area available for water uptake
Assemble potometer in water and insert the shoot underwater to prevent air moving in
Remove apparatus from water but keep the end of the capillary tubing in water in a beaker
Check apparatus is watertight and air tight
Dry the leaves and allow the shoot to acclimatise and then shut the tap
Remove one end of the capillary tube until a air bubble forms and then put capillary tube back in water
Record starting position of air bubble
Start stop watch and record distance moved by the air bubble per unit time
Control all other variable - changing variable is the species (temp thermometer/ light intensity - keep same distance from the windows and do in same room / at same time of day
Humidity type and wind also kept constant

Question 5

What is the equation for volume of a cylinder

Answer 5

Pi x r^2 x l

Question 6

Suggest why it might be considered better to use a capillary tube than a calibrated pipette to measure the water uptake

Answer 6

Capillary tubing measures a smaller volume

Question 7

Suggest why it is beneficial for the carbohydrate to be transferred through the plant is in the form of sucrose rather than an alternative carbohydrate.

Answer 7

Sucrose is soluble and can be transported in the sap
Sucrose is metabolically inactive

Question 8

How is transport in the phloem similar to the transport of substances in The xylem

Answer 8

Both use mass flow

Question 9

Explain how some parts of the plant can act as both a source and a sink

Answer 9

Certain parts can store and then release carbohydrates when needed - the root/ leaf at different times of the year

Question 10

Where is sap removed from practically

Answer 10

Sieve tube of the phloem