Transport in plants

Question 1

Define the term xylem.

Answer 1

vessels that transport water and mineral ions from the roots to the upper parts of plants.

they are strong to enable them to transport water without breaking - they also contribute to structural support

Question 2

Define the term phloem.

Answer 2

a tissue that transports sucrose and amino acids around plants.

Xylem tissue is closer to the upper surface of leaves while phloem is closer to the lower surface - xylem is on the top of the phloem

Question 3

What is the role of a root hair cell?

Answer 3

to absorb water and mineral ions from the soil.

Question 3

How are root hair cells adapted to aid their function?

Answer 3

They have a large surface area

They contain mitochondria which release energy for active transport

Question 4

Define the term transpiration

Answer 4

the evaporation of water from the aerial parts of the plant on the surface of the mesophyll cells which is followed by diffusion of water vapour through the stomata

• water is lost through the stomata
• more water is drawn up to replace the lost water

Question 5

What is the role of the spongy mesophyll cells in transpiration?

Answer 5

water vapour evaporates from the surface of spongy mesophyll cells and enters the leaf air spaces

water vapour diffuses from the air spaces out of the leaf

Question 5

By what process does water vapour exit the leaf air spaces?

Answer 5

diffusion through the stomata.

Question 6

Give three environmental variables that should be kept the same when investigating the effect of temperature on transpiration rate.

Answer 6

wind speed - the faster the wind the faster the water is moved away from the plant -increasing transpiration rate

light intensity

humidity

type/species of plant shoot

surface area of plant shoot / number of leaves that the plant shoot has

as the temperature increases so does the transpiration rate

Question 6

The relationship between number of stomata and transpiration rate

Answer 6

the more stomata, the faster the rate of transpiration (and vice versa)

Question 7

describe the pathway of water through a plant and how do you investigate it

Answer 7

1. root hair cell
2. root cortex cells
3. xylem
4. mesophyll cells

investigation:
- place a plant into a beaker of dyed water
- after several hours the leaves of the plant should turn the same colour as the dyed water
- this shows water is being taken up by the plant
- when a cross section of the plant in taken only the xylem vessels will be stained