3.4 MASS TRANSPORT IN PLANTS

Question 1

describe cohesion-tension theory of water tranpsport in the xylem

Answer 1

1. loss of water via transpiration in the leaves
2. lowers the water potential in the leaf cells/mesophyll
3. water is pulled up the xylem
4. water molecules form hydrogen bonds with eachother so they stick together
5. forming a continuous water column
6. adhesion of water to the walls of the xylem

Question 2

safety procedures in cutting stalks

Answer 2

1. use a sharp scalpel
2. cut away from yourself/your body
3. cut agains a hard/non-slip/flat surface

Question 3

how could an underwater plant live without a xylem

Answer 3

1. large surface area and thin to provide short diffusion pathway
2. surface being permeable to water

Question 4

describe the mass flow hypothesis for the mechanism of translocation in plants

Answer 4

1. sucrose is actively transported out of a source cell into the phloem
2. by companion cells
3. this lowers the water potential of the sieve cells/tube of the phloem
4. increasing the hydrostatic pressure causing mass movement
5. down the hydrostatic pressure gradient
6. sucrose used/converted in root for respiration/storage

Question 5

how to find the surface area of a leaf

Answer 5

1. draw around the leaf on graph paper and count the squares
2. on both sides of the leaf

Question 6

information needed to calculate mean rate of movement of substances down a trunk/stem

Answer 6

length of trunk/stem
concentration of substance
time taken