Download Water Movement in plants

Water Movement in plants
Objective
To be able to explain in terms of
water potential the movement of
water between plant cells and
between plant cells and their
environment
Water Potential
• Is the total potential energy of
the water molecules in a system
• It is a measure of the tendency
for water molecules to diffuse
from one place to another along
down a water potential gradient
• Pure water has the highest water
potential and it is assigned the value
zero
• Any solution has a negative water
potential
• The more concentrated a solution the
more negative its water potential
• Water moves from a less negative
(higher) water potential to a more
negative (lower) water potential
What will happen if a
plant cell is placed in
pure water?
• When a plant cell is full of water
it is Turgid
• The contents of the cell exert a
pressure on the cell wall and this
is called a pressure potential
What will happen if a
plant cell is placed in a
strong salt solution?
• As a plant cell loses turgidity the
cytoplasm and vacuole shrink
• When they exert no pressure
potential the cell is at incipient
plasmolysis
• Eventually the cell membrane pulls
away from the cell wall and the cell
is plasmolysed
A plasmolysed
plant cell
Explain, in terms of water
potential, the movement of
water between plant cells,
and between plant cells and
their environment.