Chlorophyll fluorescence measured using the Fraunhofer line-depth principle and relationship to photosynthetic rate in the field |
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Authors: | G A CARTER A F THEISEN R J MITCHELL |
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Institution: | Science and Technology Laboratory, National Aeronautics and Space Administration, Stennis Space Center, Mississippi 39529, U.S.A.;Branch of Geophysics, U.S. Geological Survey, Denver Federal Center, Denver, Colorado 80225, U.S.A.;School of Forestry, Auburn University, Auburn, Alabama 36849, U.S.A. |
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Abstract: | Abstract. A field study was conducted to determine the relationship of solar-excited chlorophyll a fluorescence to net CO2 assimilation rate in attached leaves. The Fraunhofer line-depth principle was used to measure fluorescence at 656.3 nm wavelength while leaves remained exposed to full sunlight and normal atmospheric pressures of CO2 and O2. Fluorescence induction kinetics were observed when leaves were exposed to sunlight after 10 min in darkness. Subsequently, fluorescence varied inversely with assimilation rate. In the C4 Zea mays , fluorescence decreased from 2.5 to 0.8 mW m-2 nm-1 as CO2 assimilation rate increased from 1 to 8 μmol m-2 s-1 (r2= 0.520). In the C3 Liquidambar styraciflua and Pinus taeda , fluorescence decreased from 6 to 2 mW m-2 nm-1 as assimilation rate increased from 2 to 5 or 0 to 2 μmol m-2 s-1 (r2= 0.44 and 0.45. respectively). The Fraunhofer line-depth principle enables the simultaneous measurement of solar-excited fluorescence and CO2 assimilation rate in individual leaves, but also at larger scales. Thus, it may contribute significantly to field studies of the relationship of fluorescence to photosynthesis. |
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Keywords: | chlorophyll a fluorescence photosynthesis Fraunhofer line Zea mays Liquidambar styraciflua Pinus tacda |
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