Figure 7.26 Diagram of the steady growth of a plant organ. Water uptake for growth (\(dV/dt\)) is a simple linear function of the conductance (\(L\)) between the water supply (\(\Psi_o\), usually the vascular system) and the average water potential (\(\Psi_{growth-induced}\)) of all the expanding cells in the organ (top of diagram, Eq. 7). In the same organ, the cells have walls that can slip a little (\(m\)) when turgor (\(P\)) is above a threshold (\(P_th\)) (middle, Eq. 8). Combining the two relations defines the \(\Psi_{growth-induced}\) and \(P\) for the organ (Eq. 10, bottom). Notice that the \(\Psi_{growth-induced}\) is always lower than the (\(\Psi_o\). Furthermore, the position of \(\Psi_{growth-induced}\) is determined by \(L\) and \(m\). (Diagram courtesy JS Boyer)