A terrestrial plant is growing hydroponically in a nutrient
solution. P in the hydroponic solution will be 0, because the
solution is open to the air and has nothing that can sustain a
pressure differential. Therefore, ψ is determined only by osmotic
pressure. The top of the plant is cut off, so that there are no
leaves, only the roots in the solution and the stem in the air (see
Fig. 30-17 in your book). The stem is sealed, and a pressure gauge
attached to measure pressure in the xylem. The pressure at the
start is 0, and it begins to rise. It comes to equilibrium at 0.29
MPa. The xylem contents are sampled and are found have an osmotic
pressure of 0.32 MPa.

What is ψxylem ?

What is Δψ = ψxylem-ψhydroponic at equilibrium?

What is the osmotic pressure of the hydroponic solution?

Suppose that the hydroponic solution is exchanged for one
containing 500

mM NaCl (π = 0.22 MPa). At the instant that the solution is
changed, what is Δψ = ψxylem-ψhydroponic ?

Will water move from the solution to the xylem or from the xylem
to the solution?

What will happen to the pressure in the xylem?