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Conduit Diameter (conduit + diameter)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Long-term acclimatization of hydraulic properties, xylem conduit size, wall strength and cavitation resistance in Phaseolus vulgaris in response to different environmental effects

PLANT CELL & ENVIRONMENT, Issue 5 2006
ELLEN K. HOLSTE
ABSTRACT Phaseolus vulgaris grown under various environmental conditions was used to assess long-term acclimatization of xylem structural characteristics and hydraulic properties. Conduit diameter tended to be reduced and ,wood' density (of ,woody' stems) increased under low moisture (,dry'), increased soil porosity (,porous soil') and low phosphorus (,low P') treatments. Dry and low P had the largest percentage of small vessels. Dry, low light (,shade') and porous soil treatments decreased P50 (50% loss in conductivity) by 0.15,0.25 MPa (greater cavitation resistance) compared with ,controls'. By contrast, low P increased P50 by 0.30 MPa (less cavitation resistance) compared with porous soil (the control for low P). Changes in cavitation resistance were independent of conduit diameter. By contrast, changes in cavitation resistance were correlated with wood density for the control, dry and porous soil treatments, but did not appear to be a function of wood density for the shade and low P treatments. In a separate experiment comparing control and porous soil plants, stem hydraulic conductivity (kh), specific conductivity (ks), leaf specific conductivity (LSC), total pot water loss, plant biomass and leaf area were all greater for control plants compared to porous soil plants. Porous soil plants, however, demonstrated higher midday stomatal conductance to water vapour (gs), apparently because they experienced proportionally less midday xylem cavitation. [source]

The hydraulic architecture of Juniperus communis L. ssp. communis: shrubs and trees compared

PLANT CELL & ENVIRONMENT, Issue 11 2008
BARBARA BEIKIRCHER
ABSTRACT Juniperus communis ssp. communis can grow like a shrub or it can develop a tree-like habit. In this study, the hydraulic architecture of these contrasting growth forms was compared. We analysed the hydraulic efficiency (leaf-specific conductivity, kl; specific conductivity, ks; Huber value, HV) and the vulnerability to cavitation (the water potential corresponding to a 50% loss of conductivity, ,50), as well as anatomical parameters [mean tracheid diameter, d; mean hydraulic diameter, dh; cell wall reinforcement (t/b)h2] of shrub shoots, tree stems and tree branches. Shrub shoots were similar to tree branches (especially to lower branches) in growth form and conductivity (kl = 1.93 ± 0.11 m2 s,1 MPa,1 10,7, ks = 5.71 ± 0.19 m2 s,1 MPa,1 10,4), but were similar to tree stems in their vulnerability to cavitation (,50 = ,5.81 ± 0.08 MPa). Tree stems showed extraordinarily high kl and ks values, and HV increased from the base up. Stem xylem was more vulnerable to cavitation than branch xylem, where ,50 increased from lower (,50 = ,6.44 ± 0.19 MPa) to upper branches (,50 = ,5.98 ± 0.13 MPa). Conduit diameters were correlated with kl and ks. Data indicate that differences in hydraulic architecture correspond to changes in growth form. In some aspects, the xylem hydraulics of tree-like Juniperus communis differs from that of other coniferous tree species. [source]

Interspecific relationships among growth, mortality and xylem traits of woody species from New Zealand

FUNCTIONAL ECOLOGY, Issue 2 2010
Sabrina E. Russo
Summary 1.,Wood density is considered a key functional trait influencing the growth and survival of woody plants and has been shown to be related to a slow,fast rate-of-living continuum. Wood density is, however, an emergent trait arising from several vascular properties of wood, including the diameter and frequency of xylem conduits. 2.,We aimed to test the hypotheses that there is a set of inter-related trade-offs linked to the different functions of wood, that these trade-offs have direct consequences for tree growth and survival and that these trade-offs underlie the observed correlations between wood density and demographic rates. We evaluated the covariation between xylem anatomical traits among woody species of New Zealand and whether that covariation had the potential to constrain variation in wood density and demographic rates. 3.,Several xylem traits were strongly correlated with each other, but wood density was not correlated with any of them. We also found no significant relationships between wood density and growth or mortality rate. Instead, growth was strongly related to xylem traits associated with hydraulic capacity (conduit diameter and a conductivity index) and to maximum height, whereas mortality rate was strongly correlated only with maximum height. The diameter and frequency of conduits exhibited a significant negative relationship, suggesting a trade-off, which restricted variation in wood density and growth rate, but not mortality rate. 4.,Our results suggest, for woody species in New Zealand, that growth rate is more closely linked to xylem traits determining hydraulic conductance, rather than wood density. We also found no evidence that denser woods conferred higher survival, or that risk of cavitation caused by wide conduits increased mortality. 5.,In summary, we found little support for the idea that wood density is a good proxy for position along a fast,slow rate-of-living continuum. Instead, the strong, negative relationship between vessel diameter and frequency may constrain the realized diversity of demographic niches of tree species in New Zealand. Trade-offs in function therefore have the potential to shape functional diversity and ecology of forest communities by linking selection on structure and function to population-level dynamics. [source]

Long-term acclimatization of hydraulic properties, xylem conduit size, wall strength and cavitation resistance in Phaseolus vulgaris in response to different environmental effects

Functional coordination between leaf gas exchange and vulnerability to xylem cavitation in temperate forest trees

PLANT CELL & ENVIRONMENT, Issue 4 2006
HAFIZ MAHERALI
ABSTRACT We examined functional coordination among stem and root vulnerability to xylem cavitation, plant water transport characteristics and leaf traits in 14 co-occurring temperate tree species. Relationships were evaluated using both traditional cross-species correlations and phylogenetically independent contrast (PIC) correlations. For stems, the xylem tension at which 50% of hydraulic conductivity was lost (,50) was positively associated (P < 0.001) with specific conductivity (KS) and with mean hydraulically weighted xylem conduit diameter (Dh-w), but was only marginally (P = 0.06) associated with leaf specific conductivity (KL). The PIC correlation for each of these relationships, however, was not statistically significant. There was also no relationship between root ,50 and root KS in either cross-species or PIC analysis. Photosynthetic rate (A) and stomatal conductance (gs) were strongly and positively correlated with root ,50 in the cross-species analysis (P < 0.001), a relationship that was robust to phylogenetic correction (P < 0.01). A and gs were also positively correlated with stem ,50 in the cross-species analysis (P = 0.02 and 0.10, respectively). However, only A was associated with stem ,50 in the PIC analysis (P = 0.04). Although the relationship between vulnerability to cavitation and xylem conductivity traits within specific organs (i.e. stems and roots) was weak, the strong correlation between gs and root ,50 across species suggests that there is a trade-off between vulnerability to cavitation and water transport capacity at the whole-plant level. Our results were therefore consistent with the expectation of coordination between vulnerability to xylem cavitation and the regulation of stomatal conductance, and highlight the potential physiological and evolutionary significance of root hydraulic properties in controlling interspecific variation in leaf function. [source]