研究目的
To develop a normalization method for semi-quantitative comparison of woody tissue photosynthesis using 11C-autoradiographic imaging.
研究成果
Positron autoradiography is a sensitive technique for visualizing woody tissue photosynthesis. The developed normalization method allows semi-quantitative comparison of different experiments by accounting for time-related parameters and transpiration. This approach helps in understanding the dynamics of xylem-transported CO2 and its assimilation in woody tissues.
研究不足
The method may have discrepancies due to differences in plant architecture and chlorophyll content. It requires radioactive tracers and specialized equipment, limiting accessibility. The study was performed on detached branches, which may not fully represent in vivo conditions.
1：Experimental Design and Method Selection:
The study used positron autoradiography with 11C-labeled CO2 to visualize and semi-quantify woody tissue photosynthesis in detached poplar branches. The normalization method accounted for time-related parameters and transpiration rate.
2：Sample Selection and Data Sources:
Detached young branches of Populus tremula L. with similar diameters (1.49 and 1.52 mm) were used. They were grown from cuttings in pots and watered daily.
3：49 and 52 mm) were used. They were grown from cuttings in pots and watered daily. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Cylindrical airtight treatment chamber, light source providing PAR of 250 μmol photons m-2 s-1, portable photosynthesis system (model LI-6400, Li-Cor Inc.), gas analyzer (model LI-7000, Li-Cor Inc.), autoradiographic phosphor screen (Super Resolution (SR) storage phosphor screen, Perkin Elmer), digital read-out system (Cyclone Plus, Perkin Elmer), Fiji software for image analysis, cyclotron (18 MeV protons, IBA) for producing 11CO2, citric acid buffer, polysiloxan material (Terostat-IX, Henkel AG & Company, KGaA), vacuum grease, syringes.
4：Experimental Procedures and Operational Workflow:
Branches were cut under water and fixed into a labeling compartment. They transpired an 11CO2-enriched solution for 1.5 hours in a treatment chamber with controlled light, humidity, and temperature. After labeling, branches were positioned on a phosphor screen for autoradiography, and images were read out digitally. Transpiration was measured using gas analyzers.
5：5 hours in a treatment chamber with controlled light, humidity, and temperature. After labeling, branches were positioned on a phosphor screen for autoradiography, and images were read out digitally. Transpiration was measured using gas analyzers. Data Analysis Methods:
5. Data Analysis Methods: Image analysis was performed using Fiji software to extract line profiles of radioactivity. Normalization factors were applied based on initial radioactivity, labeling time, exposure time, and transpiration rate, using the universal law of radioactive decay.
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portable photosynthesis system
LI-6400
Li-Cor Inc.
Supplies air containing 400 ppm CO2 continuously during the experiment.
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gas analyzer
LI-7000
Li-Cor Inc.
Measures water content of air entering and leaving the treatment chamber to calculate transpiration.
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autoradiographic phosphor screen
Super Resolution (SR) storage phosphor screen
Perkin Elmer
Detects radioactivity in the tissue by capturing positrons and photons emitted by the 11C tracer.
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digital read-out system
Cyclone Plus
Perkin Elmer
Reads out the phosphor screen digitally to obtain image files in arbitrary units.
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cyclotron
18 MeV protons
IBA
Produces 11CH4 by accelerating protons towards an N2/H2 target, which is then converted to 11CO2.
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polysiloxan material
Terostat-IX
Henkel AG & Company, KGaA
Used to fix the branch into the labeling compartment.
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