Hydraulic conductivity of branch junctions in three temperate tree species

Summary Hydraulic conductivities were measured in branch junctions and in the proximal segments of Quercus velutina Lam., Acer saccharum Marsh., and Tsuga canadensis (L.) Carr. In all three species, the basal proximal segment was more conductive than the junction by a factor of 1.1–1.5. There was no consistent pattern for the distal proximal segments, where the conductivities were higher, lower, or the same as the junction. These data are discussed in terms of Martin H. Zimmermann's concept of plant segmentation. It is concluded that junction constrictions to water flow contribute less to plant segmentation than the variation in leaf specific conductivity in the crown of these species.