Bellasio, ChandraChandraBellasio2024-11-132024-11-132023 The A2023-10-30Photosynthesis Research0166-8595http://hdl.handle.net/10197/27109Quantifying water use efficiency, and the impact of stomata on CO2 uptake are pivotal in physiology and efforts to improve crop yields. Although tempting, relying on regression slopes from assimilation-stomatal conductance plots to estimate water use efficiency or stomatal control over assimilation is erroneous. Through numerical simulations, I substantiate this assertion. I propose the term ‘instantaneous transpiration efficiency’ for the assimilation-to-transpiration ratio to avoid confusion with ‘intrinsic water use efficiency’ which refers to the assimilation-to-stomatal conductance ratio, and recommend to compute both metrics for each gas exchange data point.Print-ElectronicenPhotosynthesisAnalysisResponseLimitationOptimalityJournal Article158319519910.1007/s11120-023-01054-62024-01-12https://creativecommons.org/licenses/by-nc-nd/3.0/ie/