F. Transpiration

Question 1

What is water absorbed by (from the ground)

Answer 1

By roots through extensions called root hairs

Question 2

What is water transported by in the plant

Answer 2

Xylem vessels

Question 3

Through what process does water move through the plant

Answer 3

Transpiration

Question 4

What energy drives the process of transpiration

Answer 4

Heat energy, from the sun, that evaporates water from leaves

Question 5

What type of process is transpiration

Answer 5

Passive as energy comes from the sun

Question 6

Describe how water moves out the stomata

Answer 6

• humidity of the atmosphere is usually less than that of the air spaces next to the stomata
• as a result there is a water potential gradient between the air spaces and the air outside the stomata
• provided the stomata are open water vapour molecules diffuse out of the air spaces
• water lost by diffusion from the air spaces is replaced by water evaporating from the cell walls of surrounding mesophyll cells

Question 7

How can plants control the rate of transpiration

Answer 7

-changing the size of the stomatal pores

Question 8

Describe the movement of water across the cells of a leaf

Answer 8

• mesophyll cells lose water to the air spaces by evaporation (due to heat supplied to the sun)
• these cells have a lower water potential and so water enters via osmosis from neighbouring cells
• loss of water from these neighbouring cells lowers their water potential
• in turn they take water from their neighbours via osmosis

Question 9

Name a property of water that movement of water up the xylem relies on

Answer 9

Cohesion-tension

Question 10

Describe the movement of water up the stem of the xylem

Answer 10

• water evaporates from the mesophyll cells due to heat from the sun leading to transpiration
• water molecules form hydrogen bonds between one another causing water to have a property known as cohesion
• water forms a continuous unbroken column across the mesophyll cells and down the xylem
• as more water evaporates from the mesophyll cells into air spaces more water molecules are drawn up by cohesion

Question 11

What is the name for the column of water being pulled up the xylem

Answer 11

Transpiration pull

Question 12

Describe xylem vessels

Answer 12

• dead cells

- no end walls which means that the xylem forms a continuous unbroken tube from root to leaves

Question 13

Why can water uptake be an indicator of transpiration

Answer 13

99% of water is lost to transpiration