Rare pits, large vessels and extreme vulnerability to cavitation in a ring-porous tree species

New Phytol. 2012 Feb;193(3):713-20. doi: 10.1111/j.1469-8137.2011.03984.x. Epub 2011 Dec 7.

Abstract

• The rare pit hypothesis predicts that the extensive inter-vessel pitting in large early-wood vessels of ring-porous trees should render many of these vessels extremely vulnerable to cavitation by air-seeding. This prediction was tested in Quercus gambelii. • Cavitation was assessed from native hydraulic conductivity at field sap tension and in dehydrated branches. Single-vessel air injections gave air-seeding pressures through vessel files; these data were used to estimate air-seeding pressures for inter-vessel walls and pits. • Extensive cavitation occurred at xylem sap tensions below 1 MPa. Refilling occurred below 0.5 MPa and was inhibited by phloem girdling. Remaining vessels cavitated over a wide range to above 4 MPa. Similarly, 40% of injected vessel files air-seeded below 1.0 MPa, whereas the remainder seeded over a wide range exceeding 5 MPa. Inter-vessel walls averaged 1.02 MPa air-seeding pressure, similar and opposite to the mean cavitation tension of 1.22 MPa. Consistent with the rare pit hypothesis, only 7% of inter-vessel pits were estimated to air-seed by 1.22 MPa. • The results confirm the rare pit prediction that a significant fraction of large vessels in Q. gambelii experience high probability of failure by air-seeding.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Air
  • Circadian Rhythm
  • Dehydration
  • Phloem / anatomy & histology
  • Phloem / physiology
  • Plant Stems / anatomy & histology
  • Plant Stems / physiology
  • Porosity
  • Quercus / anatomy & histology*
  • Quercus / physiology*
  • Trees / anatomy & histology*
  • Trees / physiology*
  • Water / physiology*
  • Xylem / anatomy & histology*
  • Xylem / physiology*

Substances

  • Water