Plant Transport and Gas Exchange

Question 1

Autotroph

Answer 1

An organism that makes its own food from inorganic material such as water and carbon dioxide, using energy from light or from chemical reactions.

Question 2

Root pressure

Answer 2

Root pressure is the force of water that can push water up a stem from the root.

Question 3

Transpiration

Answer 3

Transpiration is the loss of water vapour from the surface of a plant.

Question 4

Who invented the cohesion - tension model?

Answer 4

Henry Dixon and John Joly in 1895.

Question 5

How does the cohesion - tension model work?

Answer 5

1. Water enters root hairs by osmosis.
2. Build up of water in the roots caused root pressure which pushes water up the xylem.
3. Water molecules are cohesive because of hydrogen bonds.
4. As each water molecule is pulled up due to transpiration, it pulls the next water molecule with it, creating tension in the unbroken column of water.