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Direct measurement of intercellular CO2 concentration in a gas-exchange system resolves overestimation using the
Jun Tominaga1,2, Hiroshi Shimada2, Yoshinobu Kawamitsu1
1Faculty of Agriculture, University of the Ryukyus, Okinawa, Japan.
Journal of Experimental Botany
|February 13, 2018
Summary
Directly measuring intercellular CO2 concentration (Ci) in leaves is more accurate than calculating it, especially when stomata close. This study modified equipment to directly measure Ci, revealing overestimations in calculated Ci under various conditions.
Area of Science:
- Plant physiology
- Photosynthesis research
- Gas exchange analysis
Background:
- Intercellular CO2 concentration (Ci) is vital for photosynthesis.
- Calculating Ci can be inaccurate, particularly when stomata close.
- Current methods may overestimate Ci, impacting photosynthesis studies.
Purpose of the Study:
- To develop and validate a method for direct intercellular CO2 concentration (Ci) measurement.
- To compare directly measured Ci (Ci(m)) with calculated Ci (Ci(c)) across different plant species and leaf surfaces.
- To assess the impact of stomatal density and leaf structure on Ci calculation accuracy.
Main Methods:
- Modification of a commercial gas-exchange system to enable simultaneous direct Ci measurement.
- Gas exchange and Ci measurements on passion fruit, sunflower, and common bean leaves.
- Comparative analysis of Ci(m) and Ci(c) on adaxial and abaxial leaf surfaces.
Main Results:
- Directly measured Ci (Ci(m)) provides a more accurate estimate than calculated Ci (Ci(c)) when stomatal conductance is restricted.
- Overestimation of Ci(c) was observed, with variations depending on plant species and measurement side.
- Leaf cuticle significantly impacts Ci calculation accuracy, especially on astomatous surfaces.
Conclusions:
- Direct measurement of intercellular CO2 concentration (Ci) is recommended for improved accuracy in photosynthesis research.
- The developed method offers a more reliable approach to assessing Ci, overcoming limitations of traditional calculation methods.
- Understanding discrepancies between measured and calculated Ci is crucial for precise plant physiological studies.
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