Osmosis and
Water Potential
in Plants
AP Big Ideas:
#2 & #4
Osmosis
Terms describe the solutions!
What if there is more than one
solute that can diffuse?
What is water potential?
 Defintion:
The tendency of water to
move from one area to another due to
osmosis and pressure.

A form of potential energy.
Water potential in a plant
Is the
potenti
al
relative
ly high
or low?
Role of Xylem and Phloem
Comparing Xylem and Phloem
Source vs. Sink
Let’s look at osmosis in terms of
water potential:
Salting the roads?
 How
does salting the roads affect the
ecological balance along highways?
 What about runoff of other solutes from
excessive fertilizing?
Lab:
 As
a class, we are going to compare
water potential of different plant parts:

Roots, Stems, Tubers, Leaves, Fruit
 Each
group will develop a standard curve
to estimate the water potential of their
assigned plant part.

You will be able to make a 1 M sucrose
solution, and then you will use serial dilutions
to make known sucrose standards.
How to use sucrose
concentration to solve for
water potential?
What will you use for
concentration?
 What
will your indepent and dependent
variables be?
 What can you use your standard curve to
solve for?