Question

In a cell if ΨP = +0.3MPa and ΨS=-0.45MPa, then the resulting Ψ is ___. Enter your answer with either a + or a - before the number and no words.

Answer 1

The answer is Ψ = -0.15 MPa.

The movement of water depends on the presence of solute, so it is referred as solute potential. But, as water enters the cells, it increases a pressure inside the cell, so this pressure is called pressure potential. The water potential (Ψ) is equal to the sum of pressure potential (ΨP) and solute potential (ΨS):
Ψ = ΨP + ΨS.
ΨP = +0.3 MPa
ΨS = -0.45 Mpa
Ψ = +0.3 MPa + -0.45MPa
Ψ = 0.3-0.45 MPa
Ψ = -0.15 MPa