Question

Give biological reason for the following:

Sticking of water to xylem walls.

Answer 1

Adhesion

1. As the mesophyll cells of the leaves lose water through transpiration, the suction pressure increases in the xylem channels.
2. The water column in the xylem vessel comes under tension or negative pressure of around 10-20 atm.
3. However, the water column does not break due to the two forces-adhesion and cohesion.
4. Adhesion attracts water molecules to the walls of the xylem.

Hence, water molecules stick to xylem vessels because of adhesion.