Transport In Plants - Transpiration

Question 1

Define transpiration

Answer 1

Loss of water vapour from the upper parts of the plant, especially the leaves

Question 2

Define the transpiration stream

Answer 2

The flow of water through a plant from roots to leaves in the xylem vessels

Question 3

What is evaporation limited by

Answer 3

Waxy cuticle

Question 4

What are the three main processes that transpiration can be split into

Answer 4

1) Osmosis
2) Evaporation
3) Diffusion

Question 5

Describe the first stage of transpiration

Answer 5

• Water enters the leaves travelling in the xylem.
• It then passes into the mesophyll cells by osmosis.
• Water may move from cell to cell by the symplast and apoplast pathway

Question 6

Describe the second stage of transpiration

Answer 6

• the water evaporates from the surface of the mesophyll cells to form water vapour
• water vapour collects in the air spaces between mesophyll cells raising the water potential

Question 7

Describe the third stage of transpiration

Answer 7

• Once the water vapour potential is higher inside the lead than outside water molecules will diffuse out of the leaf through the stomata
• water vapour is carried away from the leaf by air movements