Water relations of stem succulent trees in north-central Baja California |
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Authors: | E. T. Nilsen M. R. Sharifi P. W. Rundel I. N. Forseth J. R. Ehleringer |
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Affiliation: | (1) Biology Department, Virginia Polytechnic Institute and State University, 24061 Blacksburg, VA, USA;(2) LBES, University of California, 900 Veteran Avenue, 90024 Los Angeles, CA, USA;(3) Department of Botany, University of Maryland, 20742 College Park, MD, USA;(4) Biology Department, University of Utah, 84112 Salt Lake City, UT, USA |
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Abstract: | Summary Water relations of several stem succulent trees were measured in north-central Baja California in comparisons to other growth forms in the same habitat. Our research concentrated on three stem succulent species (Idria collumnaris, Pachycormus discolor and Bursera microphylla) each with a different succulent stem morphology. The stem succulent trees had 1 to 4 kg H2O/m3 of trunk while the other trees and shrubs in the same habitat had 0.6 to 0.8 kg H2O/m3. The diurnal and seasonal variation in leaf water potential was small for the stem succulent species in comparison to deciduous and evergreen species as a consequence of the stem-water, buffering capacity. In addition, the leaf conductance of the stem succulent species was low (60 mmol m–2 s–1) and yet, the leaf conductance decreased through the day similar to adjacent evergreen and deciduous species. The leaves of the stem succulent trees lost turgor at low saturated water deficits (0.06 to 0.14), had comparatively high osmotic potentials, and high values of elastic modulus in comparison to adjacent evergreen and deciduous species. The stem acts as an important buffering mechanism allowing for the maintenance of leaf turgor in these stem succulent trees. The low transpiration rates of the stem succulent trees may be a mechanism to minimize leaf saturated water deficit and extend leaf longevity. |
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Keywords: | Succulent C3 trees Capacitance Baja California Idria collumnaris |
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