Figure 4.

Dependence of the threshold solute concentration for bubble formation via gas segregation on xylem water tension (A), freezing velocity (B), and conduit diameter (C). Xylem water tension determines the concentration at which bubble formation becomes likely, but whether that concentration is obtained during freezing depends on freezing velocity and conduit size (Pe; see Figure 2). (B,C) Show that slightly higher concentrations are needed for bubble formation become likely in small than in large conduits (Eq. 9) and if the time allowed for nucleation to take place is short (high freezing velocity, see Eq. 18). Here the initial gas concentration was set to saturation and C* values presented concentrations above saturation.