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Abstract Detail


Environmental Physiology

Bickford, Christopher P. [1], McDowell, Nate [2], Powers, Heath [2], Brown, Karen [2], Hanson, David T. [3].

Using tunable diode laser spectroscopy to determine carbon isotope discrimination and internal CO2 conductance in field-grown juniper.

We present on-line measurements of diurnal variation in carbon isotope discrimination and internal CO2 conductance measured using a new gas exchange system capable of synchronous measurements of leaf CO2, water and isotopic exchange. We coupled a tunable diode laser spectrometer, which measures the stable carbon isotope composition of CO2 at a frequency of seconds to minutes, with a portable photosynthesis system to obtain high resolution measurements of leaf carbon isotope discrimination across three dates in June-August 2006, a period associated with shifting precipitation patterns in northern New Mexico. We found highly variable gas exchange rates in leaves of the dominant overstory plant, Juniperus monosperma, throughout the day in all three months. Net photosynthetic rate and mean carbon isotope discrimination varied between 0.1-7.5 μmol m-2 s-1 and 14.1-21.4 , respectively, in response to changing light intensity and vapor pressure deficit. Internal CO2 conductance in August ranged between 0.07-0.20 mol m-2 s-1. These findings demonstrate the sensitivity and variability of J. monosperma to microclimatic variation, and provide data on juniper responses to atmospheric conditions important for partitioning ecosystem respiration and assimilation.


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1 - University of New Mexico, Biology, MSC03-2020, Biology, 1 University of New Mexico, Albuquerque, NM, 87131, USA
2 - Los Alamos National Laboratory, Earth and Environmental Sciences Division
3 - University of New Mexico, Biology

Keywords:
stable isotope
carbon isotope discrimination
internal conductance
mesophyll conductance
Juniperus.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P01036
Abstract ID:1692


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