Sustained and significant negative water pressure in xylem

@article{Pockman1995SustainedAS,
  title={Sustained and significant negative water pressure in xylem},
  author={William T. Pockman and John S. Sperry and James W. O'leary},
  journal={Nature},
  year={1995},
  volume={378},
  pages={715-716}
}
DESPITE two centuries of research, the mechanism of water transport in plants is still debated1–8.The prevailing cohesion–tension theory2,3, which states that water is pulled upwards by capillarity in cell-wall pores, remains vulnerable to challenge because its corollary is difficult to prove: that large negative pressures exist in xylem conduits4–7. Recent xylem pressure-probe and z-tube experiments suggest that cavitation limits xylem pressures to above −0.5 MPa, despite the much more… 
New evidence for large negative xylem pressures and their measurement by the pressure chamber method
Pressure probe measurements have been interpreted as showing that xylem pressures below c. -0.4 MPa do not exist and that pressure chamber measurements of lower negative pressures are invalid. We
Xylem Surfactants Introduce a New Element to the Cohesion-Tension Theory1[OPEN]
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TLDR
The centrifuge method was used to evaluate the relationship between freeze-thaw embolism and conduit diameter across a range of xylem pressures (Px) in the conifers Pinus contorta and Juniperus scopulorum and suggested that the bubbles causing cavitation are smaller in proportion to tracheid diameter in narrow tracheids than in wider ones.
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Xylem Wall Collapse in Water-Stressed Pine Needles
TLDR
Investigating the changes in xylem geometry during water stress in needles of four pine species found a progressive collapse of tracheids below a specific threshold pressure that correlates with the onset of cavitation in the stems, suggesting a tradeoff betweenxylem efficiency, xyleM vulnerability to collapse, and the cost of wall stiffening.
Applications of the compensating pressure theory of water transport.
  • M. Canny
  • Environmental Science
    American journal of botany
  • 1998
TLDR
Far from being a metastable system on the edge of disaster, the water transport system of the xylem is ultrastable: robust and self-sustaining in response to many kinds of stress.
The relationship between xylem conduit diameter and cavitation caused by freezing.
TLDR
The centrifuge method, modified to include freeze-thaw cycles, may be useful in separating the interactive effects of xylem pressure and freezing on cavitation, and vulnerability to cavitation by freezing was correlated with the hydraulic conductivity per stem transverse area.
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