51. Gas exchange measurements in the unsteady state
- Author
-
Jon M. Welles and Aaron J. Saathoff
- Subjects
Stomatal conductance ,Time Factors ,Steady state ,Physiology ,business.industry ,Botany ,Biological Transport ,Plant Science ,High-Throughput Screening Assays ,Software portability ,Systems design ,Environmental science ,Point (geometry) ,Gases ,State (computer science) ,Process engineering ,business ,Throughput (business) ,Plant Physiological Phenomena ,Water vapor - Abstract
Leaf level gas exchange is a widely used technique that provides real-time measurement of leaf physiological properties, including CO2 assimilation (A), stomatal conductance to water vapour (gsw ) and intercellular CO2 (Ci ). Modern open-path gas exchange systems offer greater portability than the laboratory-built systems of the past and take advantage of high-precision infrared gas analyzers and optimized system design. However, the basic measurement paradigm has long required steady-state conditions for accurate measurement. For CO2 response curves, this requirement has meant that each point on the curve needs 1-3 min and a full response curve generally requires 20-35 min to obtain a sufficient number of points to estimate parameters such as the maximum velocity of carboxylation (Vc,max ) and the maximum rate of electron transport (Jmax ). For survey measurements, the steady-state requirement has meant that accurate measurement of assimilation has required about 1-2 min. However, steady-state conditions are not a strict prerequisite for accurate gas exchange measurements. Here, we present a new method, termed dynamic assimilation, that is based on first principles and allows for more rapid gas exchange measurements, helping to make the technique more useful for high throughput applications.
- Published
- 2021