4.8 Evaporation and transpiration

Question 1

What is transpiration

Answer 1

Loss of water vapour from the surface of the plant

Question 2

How is the stomata able to open and close

Answer 2

• High concentration of water causes osmosis to take place, making the guard cells open up the stomata
• When there is low concentration of water in the spaces compared to guard cells, osmosis causes water to leave the guard cells and resulting in them shrivelling up. This closes the stomata

Question 3

Where are most stomata present

Answer 3

Lower surface

Question 4

What is the transpiration stream

Answer 4

Constant movement of water molecules through the xylem fronm the roots to the leaves

Question 5

Describe how transpiration stream works

Answer 5

• Water moves into roots from soil by osmosis
• water and minerals move from cells to cell to the roots until they reach the xylem vessels
• water moves up through the stem and into the leaves in the xylem
• water is lost by evaporation through open stomata