Developing A (CO₂ assimilation rate) versus C_i (internal CO₂ concentration) curves provides parameters for biochemical models of photosynthesis, which permit extrapolation of A to other environmental conditions, or comparisons among genotypes. However, developing A vs. C_i curves from steady-state measurements takes 20 to 30 minutes per leaf to obtain sufficient data points to define the model parameters.

Measuring the Assimilation of (A) versus the intercellular CO₂ concentration (C_i) of plant leaves is a valuable component of the physiologist’s toolkit. However, traditional methods of obtaining A vs. C_i curves can require laborious data collection of greater than 40 minutes per leaf sampled. We developed a fast-ramping methodology to obtain A vs. C_i curves in as few as five minutes through a simple volume correction in the gas lines of the infrared gas analyzers (IRGAs). This single-step CO₂ response method (SSCO₂R™) was validated in the field for five species of horticultural importance and was found to agree with traditional steady-state methods for obtaining A vs. Ci curves. During validation, data from various species and cultivars within species were collected using a light source including varied white and far-red light LEDs. The rate of A varied by species and cultivar, suggesting significant differences in crop responses to far-red light. Using the SSCO₂R™ method, a diverse dataset with high accuracy can be generated in a fraction of the time as steady-state methods.