, Volume 42, Issue 1, pp 133–138

Leaf Gas Exchange and Water Relations in Polylepis tarapacana at Extreme Altitudes in the Bolivian Andes


  • C. García-Núñez
    • ICAE, Facultad de CienciasUniversidad de los Andes, Mérida
  • F. Rada
    • ICAE, Facultad de CienciasUniversidad de los Andes, Mérida
  • C. Boero
    • Fundación Miguel Lillo, Tucumán
  • J. González
    • Fundación Miguel Lillo, Tucumán
  • M. Gallardo
    • Fundación Miguel Lillo, Tucumán
  • A. Azócar
    • ICAE, Facultad de CienciasUniversidad de los Andes, Mérida
  • M. Liberman-Cruz
    • Instituto de EcologíaUniversidad Mayor de San Andrés, La Paz
  • M. Hilal
    • Fundación Miguel Lillo, Tucumán
  • F. Prado
    • Fundación Miguel Lillo, Tucumán

DOI: 10.1023/B:PHOT.0000040581.94641.ed

Cite this article as:
García-Núñez, C., Rada, F., Boero, C. et al. Photosynthetica (2004) 42: 133. doi:10.1023/B:PHOT.0000040581.94641.ed


Stress-induced restrictions to carbon balance, growth, and reproduction are the causes of tree-line formation at a global scale. We studied gas exchange and water relations of Polylepis tarapacana in the field, considering the possible effects of water stress limitations imposed on net photosynthetic rate (PN). Daily courses of microclimatic variables, gas exchange, and leaf water potential were measured in both dry-cold and wet-warm seasons at an altitude of 4 300 m. Marked differences in environmental conditions between seasons resulted in differences for the dry-cold and wet-warm seasons in mean leaf water potentials (−1.67 and −1.02 MPa, respectively) and mean leaf conductances (33.5 and 58.9 mmol m−2 s−1, respectively), while differences in mean PN (2.5 and 2.8 μmol m−2 s−1, respectively) were not as evident. This may be related to limitations imposed by water deficit and lower photon flux densities during dry and wet seasons, respectively. Hence P. tarapacana has coupled its gas exchange characteristics to the extreme daily and seasonal variations in temperature and water availability of high elevations.

high Andesleaf water potentialnet photosynthetic ratestomatal conductancetranspiration ratetree growth limitwater use efficiency
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© Kluwer Academic Publishers 2004