Vertical Gradients of Water Potential and Tissue Water Relations in Sitka Spruce Trees Measured with the Pressure Chamber

Hellkvist, Jerk; Richards, G. P.; Jarvis, P. G.

doi:10.2307/2402215

Cited by 313 publications

(125 citation statements)

References 63 publications

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“…This is also in contrast to results by Salleo et (19). The dp/dxs we found for stems of B. fassoglensis, of about 0.08 MPa m-', were much less steep than has been reported for small herbaceous plants (3,14), but similar to those found in coniferous trees ( 14). The difference in xylem water potential between bagged and unbagged leaves is taken as the drop in xylem water potential in going from the stem to a transpiring (unbagged) leaf.…”

Section: Discussioncontrasting

confidence: 99%

“…The bagged leaf method (14) was employed to measure the stem I at different points along the stem. In B. fassoglensis leaves persist on stems for up to 55 nodes after they mature, which represents a distance of 4 m. A set of adjacent distal and a set ofadjacent proximal leaves were bagged to eliminate their transpiration and thus allow them to equilibrate with their insertion point on the stem.…”

Section: Predicted Khmentioning

confidence: 99%

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Water Transport in the Liana Bauhinia fassoglensis (Fabaceae)

Ewers¹,

Fisher²,

Chiu³

1989

Plant Physiol.

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To determine the efficiency of xylem conductance in the liana (woody vine) Bauhinia fassoglensis Kotschy ex Schweinf., we measured hydraulic conductance per unit stem length (measured Kh), leaf-specific conductivity (LSC = Kh/distal leaf area), transpiration rate (E), xylem water potential (I), vessel number, and vessel diameter. The measured Kh was 49% (SE = 7%) of the predicted Kh from Poiseuille's law. The mean LSC for unbranched stem segments was 1.10 x 10-6 square meters per megapascal per second (SE = 0.07). LSCs were much lower (about 0.2) at branch junctions. At midday, with E at 7 x 10-6 meters per second, the measured drop in 'I was about 0.08 megapascal per meter along the stems and branches and about 0.27 megapascal in going from stem to leaf. In addition, there was a drop of about 0.20 megapascal at branch junctions as predicted by E/LSC. In diurnal measurements leaf ' never dropped below about -1.2 megapascal. For long (e.g. 16 meters) stems, the predicted midday drop in I through the xylem transport system might be great enough to have substantial physiological impact.draulic pathways is to measure Kh in isolated stem segments from throughout the shoot systems (8,11,12,27,28).Poiseuille's law for ideal capillaries can be used to relate vessel number and diameter to Kh by the following formula:predicted Kh = ir 2 d4/128 v (1) with K-in m4 MPa-' s-', i = dynamic viscosity of the fluid (MPa s), and the summation is over all conducting elements (diameter di) for the ith capillary in m.To determine how effective a stem is at supplying its leaves, we need to consider not only measured Kh and predicted Kh, but also the leaf area that the stem segment supplies and the E of the leaves (27). LSC is equal to measured Kh divided by the leaf area distal to the stem segment. LSCs have the advantage that they allow a theoretical basis for relating measured Kh to dp/dxs in shoot systems with long and complex transport pathways (19,(26)(27)(28): dp/dx = E/LSCThe long and slender stems of lianas (woody vines) are commonly thought to be extremely efficient in water transport due to their long and wide vessels (5, 6, 8, 15-17, 29, 30). However, although there is much evidence that liana vessels are wider than in closely related trees (5,8,10), there are few published data to indicate whether liana stems are particularly efficient at supplying their leaves with water.Xylem transport efficiency is often expressed as the measured hydraulic conductance per unit stem length (measured Kh2), which is defined as the xylem flow rate divided by the pressure gradient (dp/dx). When such measurements are made on intact plants, they are valid only when taken along unbranched portions of the plant axis that do not bear leaves. On branched systems and/or systems with different transport distances to each leaf, a single Kh measurement can be meaningless (18,26). Our approach to modeling the various hy-'

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Section: Discussioncontrasting

confidence: 99%

Section: Predicted Khmentioning

confidence: 99%

Water Transport in the Liana Bauhinia fassoglensis (Fabaceae)

Ewers¹,

Fisher²,

Chiu³

1989

Plant Physiol.

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“…Acid input to the foliage and soil via wet and dry deposition may be a major factor in causing decline directly or indirectly by predisposing the tree to additional biotic and/or abiotic stress factors. (Hellkvist et al, 1974). Eight replicate branches from pH ?-.5, 3.0, 4.0 and 5.0 treated trees were measured.…”

Section: Introductionmentioning

confidence: 99%

The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves of red spruce seedlings

Eamus¹,

Leith²,

Fowler³

1989

Ann. For. Sci.

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“…In dry temperate regions, such as the redwood forests of California (Prat 1953, Azevedo & Morgan 1974 and the radiata pine forests of the adjacent coastal islands, fog is also a significant contributor to the water balance of the forests (Rutter 1981). Reduction in evapotranspiration and increased precipitation from interception of the fog by the foliage (Rutter 1981) are thought to be the main factors but direct uptake by the foliage is also probable (Gaertner 1964, Martin & Juniper 1970, Levitt 1972, Hellkvist et al 1974.…”

Section: Introductionmentioning

confidence: 99%

Diurnal patterns of water potential in the evergreen cloud forests of the Kaimai Ranges, North Island, New Zealand

Green

Jane

1983

New Zealand Journal of Botany

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Water potentials were measured on six species of evergreen trees growing at a range of altitudes, including the cloud zone, on two ridges in the Kaimai Ranges. Diurnal sampling at intervals throughout the summer showed little evidence of plant water stress. Dawn potentials were about -0.1 MPa and minimum potentials were down to -1.2 MPa except in QUintinia acutifolia. a seral shrub. This species yeilded low dawn potentials (-0.6 MPa) at a 600 m a.s.l. site which was below the cloud zone. Plants of unhealthy appearance growing on poor sites had lower potentials than healthy plants on adjacent good sites. Fog occurrence produced higher dawn potentials but had no effect on daily minimum potentials. The results contrast with leaf conductance studies in the same area which showed severe stress with rapid afternoon stomatal closure. It is suggested that the fog promotes soil waterlogging leading to water stress which is reflected in stomatal sensitivity but not shoot water potential.

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Vertical Gradients of Water Potential and Tissue Water Relations in Sitka Spruce Trees Measured with the Pressure Chamber

Cited by 313 publications

References 63 publications

Water Transport in the Liana Bauhinia fassoglensis (Fabaceae)

Water Transport in the Liana Bauhinia fassoglensis (Fabaceae)

The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves of red spruce seedlings

Diurnal patterns of water potential in the evergreen cloud forests of the Kaimai Ranges, North Island, New Zealand

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