Xylem conductivity and vulnerability to cavitation of ponderosa pine growing in contrasting climates

Hafiz Maherali, Evan H. DeLucia

Research output: Contribution to journalArticle

Abstract

We examined the effects of increased transpiration demand on xylem hydraulic conductivity and vulnerability to cavitation of mature ponderosa pine (Pinus ponderosa Laws.) by comparing trees growing in contrasting climates. Previous studies determined that trees growing in warm and dry sites (desert) had half the leaf/sapwood area ratio (A(L)/A(S)) and more than twice the transpiration rate of trees growing in cool and moist sites (montane). We predicted that high transpiration rates would be associated with increased specific hydraulic conductivity (K(S)) and increased resistance to xylem cavitation. Desert trees had 19% higher K(S) than montane trees, primarily because of larger tracheid lumen diameters. Predawn water potential and water potential differences between the soil and the shoot were similar for desert and montane trees, suggesting that differences in tracheid anatomy, and therefore K(S), were caused primarily by temperature and evaporative demand, rather than soil drought. Vulnerability to xylem cavitation did not differ between desert and montane populations. A 50% loss in hydraulic conductivity occurred at water potentials between-2.61 and-2.65 MPa, and vulnerability to xylem cavitation did not vary with stem size. Minimum xylem tensions of desert and montane trees did not drop below -2.05 MPa. Foliage turgor loss point did not differ between climate groups and corresponded to mean minimum xylem tensions in the field. In addition to low A(L)/A(S), high K(S) in desert trees may provide a way to increase tree hydraulic conductivity in response to high evaporative demand and prevent xylem tensions from reaching values that cause catastrophic cavitation. In ponderosa pine, the flexible responses of A(L)/A(S) and K(S) to climate may preclude the existence of significant intraspecific variation in the vulnerability of xylem to cavitation.

Original languageEnglish (US)
Pages (from-to)859-867
Number of pages9
JournalTree Physiology
Volume20
Issue number13
DOIs
StatePublished - Jul 2000

Fingerprint

Pinus ponderosa
Xylem
Climate
xylem
climate
deserts
hydraulic conductivity
water potential
transpiration
Water
Soil
Droughts
sapwood
turgor
leaves
soil
Anatomy

Keywords

  • Hydraulic conductivity
  • Leaf/sapwood area ratio
  • Temperature
  • Vapor pressure deficit
  • Xylem cavitation

ASJC Scopus subject areas

  • Physiology
  • Plant Science

Cite this

Xylem conductivity and vulnerability to cavitation of ponderosa pine growing in contrasting climates. / Maherali, Hafiz; DeLucia, Evan H.

In: Tree Physiology, Vol. 20, No. 13, 07.2000, p. 859-867.

Research output: Contribution to journalArticle

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abstract = "We examined the effects of increased transpiration demand on xylem hydraulic conductivity and vulnerability to cavitation of mature ponderosa pine (Pinus ponderosa Laws.) by comparing trees growing in contrasting climates. Previous studies determined that trees growing in warm and dry sites (desert) had half the leaf/sapwood area ratio (A(L)/A(S)) and more than twice the transpiration rate of trees growing in cool and moist sites (montane). We predicted that high transpiration rates would be associated with increased specific hydraulic conductivity (K(S)) and increased resistance to xylem cavitation. Desert trees had 19{\%} higher K(S) than montane trees, primarily because of larger tracheid lumen diameters. Predawn water potential and water potential differences between the soil and the shoot were similar for desert and montane trees, suggesting that differences in tracheid anatomy, and therefore K(S), were caused primarily by temperature and evaporative demand, rather than soil drought. Vulnerability to xylem cavitation did not differ between desert and montane populations. A 50{\%} loss in hydraulic conductivity occurred at water potentials between-2.61 and-2.65 MPa, and vulnerability to xylem cavitation did not vary with stem size. Minimum xylem tensions of desert and montane trees did not drop below -2.05 MPa. Foliage turgor loss point did not differ between climate groups and corresponded to mean minimum xylem tensions in the field. In addition to low A(L)/A(S), high K(S) in desert trees may provide a way to increase tree hydraulic conductivity in response to high evaporative demand and prevent xylem tensions from reaching values that cause catastrophic cavitation. In ponderosa pine, the flexible responses of A(L)/A(S) and K(S) to climate may preclude the existence of significant intraspecific variation in the vulnerability of xylem to cavitation.",
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