Question

Describe the cohesion-tension theory of water transport in the xylem.
[5 marks]

Accepted Answer

1. Water lost from leaf because of transpiration /
evaporation of water (molecules) / diffusion
from mesophyll / leaf cells;
OR
Transpiration / evaporation / diffusion of water
(molecules) through stomata / from leaves;
2. Lowers water potential of mesophyll / leaf
cells;
3. Water pulled up xylem (creating tension);
4. Water molecules cohere / 'stick' together by
hydrogen bonds;
5. (forming continuous) water column;
6. Adhesion of water (molecules) to walls of
xylem;

Water Leaf Molecules Transpiration Evaporation Diffusion Mesophyll Cells