9 Springer-Verlag 1992 Xylem structure and water transport in a twiner, a scrambler, and a shrub of Lonicera (Caprifoliaceae)

Summary. Wood structure and function was investigated in different growth forms of temperate honeysuckles (Lon-icera spp.). All three species had many narrow vessels and relatively few wide ones, with the measured Kh (flow rate/pressure gradient) approximately 24-55 % of the theoretical Kh predicted by Poiseuille's law. Only the twiner, Lonicera japonica, had some vessels greater than 50 ~tm in diameter. The twiner also had the narrowest stem xylem diameters, uggesting the greater maximum vessel diameter hydraulically compensated for narrow stems. Conversely, the free-standing shrub, L. maackii, had the greatest annual increments of xylem but the least percent conductive xylem implying that a great portion of the wood was involved with mechanical support. The scrambler, L, sempervirens had low maximum vessel diameter, high Huber values ( = xylem area/leaf area), and low specific conductivities ( = measured Kh/xylem area), much like the shrub. The greatest vessel frequency occurred in the scram-bler (901 vessels, mm-2), the highest hus far recorded in vines. The lowest Huber value and highest specific con-ductivity occurred in the twiner, suggesting little self-sup-port but relatively efficient water conduction. LSC ( = mea-sured Kh/leaf area) and maximum vessel diameter of Lon-icera vines were near the low end of the range for vines in general