Suppose two living plant cells are in contact with each other such that water, but NOT solutes, can pass between them. Also suppose that the cells have the same water potential, and that one cell has $\varPsi$_p=0.3 MPa and $\varPsi$_s = -0.5 MPa, while the other cell has $\varPsi$_s = -0.3 MPa. What is the $\varPsi$_p of the second cell?

Question

Quizplus · Accepted Answer

Water potential ($\Psi$) in plants is determined by the equation $\Psi = \Psi_p + \Psi_s$, where $\Psi_p$ is the pressure potential and $\Psi_s$ is the solute potential. Given that both cells have the same water potential and that water can move freely between them but solutes cannot, the water potential of both cells must be equal. For the first cell, the given values are $\Psi_p = 0.3$ MPa and $\Psi_s = -0.5$ MPa. Therefore, the water potential of the first cell is $0.3 + (-0.5) = -0.2$ MPa. Since the water potential of both cells is the same, the second cell also has a water potential of $-0.2$ MPa. Given that the solute potential ($\Psi_s$) of the second cell is $-0.3$ MPa, to find its pressure potential ($\Psi_p$), we rearrange the water potential equation to $\Psi_p = \Psi - \Psi_s$. Substituting the known values gives $\Psi_p = -0.2 - (-0.3) = 0.1$ MPa.

Suppose Two Living Plant Cells Are in Contact with Each Ψ\varPsiΨ

Suppose Two Living Plant Cells Are in Contact with Each $\varPsi$