Little is known of wood properties in trees that were initially suppressed and subsequently released from suppression. The purpose of this study was to assess differences in growth ring width, specific conductivity (Ks), tracheid dimensions, moisture content, and wood density in suppressed Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock...
The cohesion-tension theory of water transport states that hydrogen bonds hold water molecules together and that they are pulled through the xylem under tension. This tension could cause transport failure in at least two ways: collapse of the conduit walls (implosion), or rupture of the water column through air-seeding. The...
Despite renewed interest in the nature of limitations on maximum tree height, the mechanisms governing ultimate and species-specific height limits are not yet understood, but likely involve water transport dynamics. Tall trees experience increased risk of xylem embolism from air-seeding because tension in their water column increases with height due...
The air‐seeding hypothesis predicts that xylem embolism resistance is linked directly to bordered pit functioning. We tested this prediction in trunks, roots, and branches at different vertical and radial locations in young and old trees of Pseudotsuga menziesii. Dimensions of bordered pits were measured from light and scanning electron micrographs,...
• There are two optima for maximizing hydraulic conductance per vasculature volume in plants. Murray's law (ML) predicts the optimal conduit taper for a fixed change in conduit number across branch ranks. The opposite, the Yarrum optimum (YO), predicts the optimal change in conduit number for a fixed taper.
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• Coniferous, diffuse‐porous and ring‐porous trees vary in their xylem anatomy, but the functional consequences of these differences are not well understood from the scale of the conduit to the individual.
• Hydraulic and anatomical measurements were made on branches and trunks from 16 species from temperate and tropical areas,...
• Hydraulic vulnerability of Douglas-fir (Pseudotsuga menziesii) branchlets
decreases with height, allowing shoots at greater height to maintain hydraulic
conductance (Kshoot) at more negative leaf water potentials (Ψl).
• To determine the basis for this trend shoot hydraulic and tracheid anatomical
properties of foliage from the tops of Douglas-fir trees...
Our goals were to quantify how non-embolism-inducing pressure gradients influence trunk sapwood specific conductivity (ks) and to compare the impacts of constant and varying pressure gradients on ks with KCl and H2O as the perfusion solutions. We studied six woody species (three conifers and three angiosperms) which varied in pit...
1. The xylem pressure inducing 50% loss of hydraulic conductivity due to embolism
widely used for comparisons of xylem vulnerability among species and across aridity
However, despite its utility as an index of resistance to catastrophic xylem failure
drought, P5o may have no special physiological relevance in the context of...
We determined the axial and radial xylem tension gradients in trunks of young Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees. Axial specific conductivity (ks-a) and sap flux density (Js) were measured at four consecutive depths within the sapwood at a stem height of 1 m. By definition, at a given position...
The volume and complexity of their vascular systems make the dynamics of long‐distance water transport in large trees difficult to study. We used heat and deuterated water (D₂O) as tracers to characterize whole‐tree water transport and storage properties in individual trees belonging to the coniferous species Pseudotsuga menziesii (Mirb.) Franco...
This study investigated the mechanisms involved in the
regulation of stomatal closure in Douglas-fir and evaluated
the potential impact of compensatory adjustments in
response to increasing tree height upon these mechanisms.
In the laboratory, we measured leaf hydraulic conductance
(Kleaf) as leaf water potential (Yl) declined for comparison
with in...
Use of Granier-style heat dissipation sensors to measure sap flow is common in plant physiology, ecology and hydrology. There has been concern that any change to the original Granier design invalidates the empirical relationship between sap flux density and the temperature difference between the probes. Here, we compared daily water...
The gravitational component of water potential and frictional resistance during transpiration lead to substantial reductions in leaf water potential (Ψl) near the tops of tall trees, which can influence both leaf growth and physiology. We examined the relationships between morphological features and gas exchange in foliage collected near the tops...
Premise of the study: The Pacific Northwest of North America experiences relatively mild winters and dry summers. For the
tall coniferous trees that grow in this region, we predicted that loss in the hydraulic conductivity of uppermost branches would
be avoided because of difficulty reversing accumulated emboli in xylem that...
In the Pacific north-west, the Cascade Mountain Range blocks much of the precipitation and maritime influence of the Pacific Ocean, resulting in distinct climates east and west of the mountains. The current study aimed to investigate relationships between water storage and transport properties in populations of Douglas-fir (Pseudotsuga menziesii) and...
We studied xylem anatomy and hydraulic architecture in 14 transgenic insertion events and a control line of hybrid poplar (Populus spp.) that varied in lignin content. Transgenic events had different levels of down‐regulation of two genes encoding 4‐coumarate:coenzyme A ligase (4CL). Two‐year‐old trees were characterized after growing either as free‐standing...
Given the fundamental importance of xylem safety and efficiency for plant survival and fitness, it is not surprising that these are among the most commonly studied features of hydraulic architecture. However, much remains to be learned about the nature and universality of conflicts between hydraulic safety and efficiency. Although selection...
Of 14 transgenic poplar genotypes (Populus tremula × Populus alba) with antisense 4-coumarate:coenzyme A ligase that were grown in the field for 2 years, five that had substantial lignin reductions also had greatly reduced xylem-specific conductivity compared with that of control trees and those transgenic events with small reductions in...