ARS | Publication request: System Approach for Improved Whole Canopy Photosynthesis Measurement

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 24, 2007
Publication Date: June 25, 2007
Citation: Takahashi, N., Ling, P., Klingman, M., Frantz, J. 2007. System Approach for Improved Whole Canopy Photosynthesis Measurement. Meeting Proceedings. Japanese Society of Agricultural, Biological, and Environmental Engineers and Scientists 2007 Conference, June 25-27, Sakai, Osaka, Japan.

Technical Abstract: Whole canopy photosynthetic rate (Pn) measurement is used for quantifying short term integral plant responses to the environment and for determining the final yield of a crop. Pn of an Open assimilation chamber is determined using the product of air flow rate of the chamber and CO2 differential between inlet and outlet of the chamber. Large CO2 differential is desirable for improved sensing reliability. On the other hand, too high a CO2 differential may negatively affect photosynthetic rate of a plant if the chamber CO2 concentration is not controlled accurately. While many factors affect the photosynthetic rate of plants, the CO2 differential is most accurately established by taking into account the characteristics of individual plants and the environment they are in for each and every photosynthesis measurement task. Researchers have reported various CO2 differentials, ranging from 10-35 'mol mol-1, used in their measurement systems. No methodology for the maximum CO2 differential determination was attempted in their efforts. The objectives of this study were to evaluate the effect of CO2 differential on photosynthesis of a model plant, and to develop a methodology to determine the maximum CO2 differential for the photosynthesis measurement tasks. Our goal has been to improve CO2 measurement within a system so that photosynthesis is more accurately measured in order to provide a more reliable, non-destructive method for predicting the final yield or quantifying effects of environmental, pest, and nutritional changes on the productivity of plants.