Measuring solar-induced chlorophyll fluorescence (SIF) is a promising method to track the light reactions of photosynthesis using remote sensing techniques, but little is known about the mechanisms of SIF at the leaf-level. In chapter 1, a LI-COR LI-6800 gas exchange instrument was modified with a visible-near-infrared (VIS-NIR) spectrometer to measure active and passive chlorophyll fluorescence simultaneously. The system was adapted by drilling a hole into the bottom plate of the leaf chamber and inserting a fiber-optic to measure SIF from the abaxial surface of a leaf. This new set-up can concurrently measure gas exchange, passive fluorescence, and active fluorescence over the same leaf area and will allow researchers to measure leaf-level SIF in the field to validate tower-based and satellite measurements.
To test the modified instrument, measurements were performed on well-watered and water stressed walnut leaves at three light levels and a constant temperature. Measurements on these same plants were also conducted using a similarly modified Walz GFS-3000 gas exchange instrument to compare results. We found a positive linear correlation between the SIF measurements from the modified LI-6800 and GFS-3000 instruments. We also report a positive linear relationship between the SIF and the normalized steady-state chlorophyll fluorescence (Fs/Fo) from the pulse-amplitude modulation (PAM) fluorometer of the LI-6800 system. Accordingly, this modification will inform the link between spectrally resolved SIF and gas-exchange – leading to improved interpretation of how SIF tracks changes in the light reactions of photosynthesis.
In chapter 2, the relationships between SIF, SIF yield, net CO2 assimilation (Anet), and electron transport rate (ETR) at the leaf-level were explored for three plant species: grapes, walnuts, and almonds. We examine how these relationships change under three water treatments (well-watered, moderately stressed, and water stressed) that were maintained by targeting a range of leaf water potentials based on the mass percentage of water in the soil. The effects of temperature stress and light intensity were determined by exposing the leaf to varying environmental conditions imposed within the leaf chamber of a gas exchange system.
It was found that a near 100% decrease in photosynthesis corresponded to around a 30% decrease in SIF for grapes and a 20% decrease in SIF for walnuts. For grapes and walnuts, SIF was found to be relatively linearly correlated with both Anet and ETR, with the strongest relationships at 500 μmol m-2 s-1 PAR due to the light saturation of photosynthesis at 1500 μmol m-2 s-1. The measurements for the almond trees were inconclusive and did not follow the expected trends for SIF and Anet. There was a clear SIF response to temperature stress but not water stress. Future work will investigate this discrepancy for almonds.
|Advisor:||Phillips, Ronald, McElrone, Andrew J|
|Commitee:||Magney, Troy S|
|School:||University of California, Davis|
|School Location:||United States -- California|
|Source:||MAI 82/2(E), Masters Abstracts International|
|Subjects:||Plant sciences, Botany, Biochemistry, Chemical engineering|
|Keywords:||Chlorophyll fluorescence, Photosynthesis, Solar-induced chlorophyll fluorescence|
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