© 1993 Heron Publishing—Victoria, Canada
Variation in seedling hydraulic architecture as a function of species and environment
Durland L. Shumway (1), Kim C. Steiner (2) and Thomas E. Kolb (3)
1. Department of Biology, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802, USA / 2. School of Forest Resources, 313 Forest Resources Laboratory, Pennsylvania State University, University Park, PA 16802, USA / 3. School of Forest Resources, 212 Ferguson Building, Pennsylvania State University, University Park, PA 16802, USA / Received May 11, 1992
Summary
Northern red oak (Quercus rubra L.) and yellow-poplar (Liriodendron tulipifera L.) were grown for two years in full sunlight (unshaded) or 20% of full sunlight (shaded) under either well-watered or drought
conditions. There was a close association between evaporative flux (in situ) and leaf-specific conductivity (LSC) in stem
segments of both species. Shaded, drought-stressed seedlings of both species had significantly reduced leaf area, evaporative
flux, volume flow rate in xylem, flow velocity, potentially functional xylem area, and LSC than unshaded, well-watered seedlings.
Reductions in LSC associated with drought or shade were similar for both species; and within a treatment, both species had
similar
LSC. Species differed in the manner of LSC adjustment to drought and shade. Reductions in leaf area associated with drought
or shade were accompanied primarily by reductions in potentially functional xylem area for L. tulipifera, and by reductions in flow velocity for Q. rubra. These results suggest (1) the existence of a homeostatic balance between evaporative flux and LSC, (2) that species with
widely different growth patterns and xylem anatomies may develop similar LSC within the same environment, and (3) a possible
hydraulic basis for differences in habitat between ring- and diffuse-porous species.
Keywords:
diffuse-porous, drought stress, evaporative flux, irradiance, leaf area, leaf specific conductivity, ring-porous, xylem transport
capability.
