Resistance to water flow in xylem of Picea abies (L.) Karst. trees grown under contrasting light conditions

Abstract

Summary. The relative hydraulic conductivity (k) of xylem and resistance (R) to water flow through trunk, primary roots and branches in Picea abies trees growing under contrasting light conditions were investigated. The xylem permeability to water was measured by forcing 10 mM water solution of KC1 through excised wood specimens. From the values of k, the sapwood transverse area and the length of conducting segments, R of the whole trunk, branches and roots was calculated. The relative conductivity of xylem in open-grown trees exceeded that of shade-grown trees by 1.4-3.1 times, while k was closely correlated with the hydraulically effective radius (re) of the largest tracheids (r 2 was 0.85-0.94 for open-and 0.51-0.79 for shade-grown trees). Because of both a low k and a smaller sapwood area in shade-grown trees the resistance to water movement through their trunk, roots and branches was many times higher. The distribution of R between single segments of the water-conducting pathway differed considerably in trees from different sites. At high water status the largest share of the total resistance in open-as well as shade-grown trees resides in the apical part of the trunk. The contribution of the branches to total xylem resistance is supposed to increase with developing water deficit.

Base water potential of Picea abies as a characteristic of the soil water status

“…This can be explained by long distance between the soil and leaves in trees and their hydraulic properties (Tyree and Ewers, 1991). This pattern, becoming more evident with decreasing soil water availability and occurring more often in trees growing in unfavourable conditions, is obviously caused by high xylem resistance of the trees under stress conditions (Sellin, 1993(Sellin, , 1996. In contrast to my results, Whitlow et al (1992) reported that maximum hu in Fraxinus pennsylvanica Marsh.…”

Temporal and spatial variation in transpiration of Norway spruce stands within a forested catchment of the Fichtelgebirge, Germany

“…A similar effect of stand age on the leaf area/sapwood area ratio of stands was reported by Albrektson [2], while Aussenac and Granier [4] showed that this ratio is influenced by tree density and, therefore, by thinning practices. Changes within stands seem to be related to the response to light climate [64]. Thinning results in large changes in tree density at the sites investigated and on the leaf area/sapwood area ratio ( figure 10).…”

Ecophysiological responses to simulated canopy gaps of two tree species of contrasting shade tolerance in elevated CO2

“…For example, high transpirational demand on the south-facing side of a mature Fraxinus americana tree resulted in higher leaf-specific conductivity in those branches compared with branches on the north side of the crown (Joyce & Steiner 1995). Opengrown Picea abies trees had 1·4-to 3·1-times greater xylem conductivity than shade-grown trees (Sellin 1993). In Sugar cane, removal of leaf area resulted in increased g w of the remaining leaves to maintain a constant relationship between crown E and stem flow and, conversely, root pruning resulted in reduced g w (Meinzer & Grantz 1990).…”