RT Journal Article SR Electronic T1 A universal model for carbon dioxide uptake by plants JF bioRxiv FD Cold Spring Harbor Laboratory SP 040246 DO 10.1101/040246 A1 Han Wang A1 I. Colin Prentice A1 William K. Cornwell A1 Trevor F. Keenan A1 Tyler W. Davis A1 Ian J. Wright A1 Bradley J. Evans A1 Changhui Peng YR 2016 UL http://biorxiv.org/content/early/2016/02/19/040246.abstract AB The rate of carbon uptake by land plants depends on the ratio of leaf-internal to ambient carbon dioxide partial pressures1, here termed χ. This quantity is a key determinant of both primary production and transpiration and the relationship between them. But current models for χ are empirical and incomplete, contributing to the many uncertainties afflicting model estimates and future projections of terrestrial carbon uptake2,3. Here we show that a simple evolutionary optimality hypothesis4,5 generates functional relationships between χ and growth temperature, vapour pressure deficit and elevation that are precisely and quantitatively consistent with empirical χ values from a worldwide data set containing > 3500 stable carbon isotope measurements. A single global equation embodying these relationships then unifies the empirical light use efficiency model with the standard model of C3 photosynthesis1, and successfully predicts gross primary production as measured at flux sites. This achievement is notable because of the equation′s simplicity (with just two parameters, both independently estimated) and applicability across biomes and plant functional types. Thereby it provides a theoretical underpinning, grounded in eco-evolutionary principles, for large-scale analysis of the CO2 and water exchanges between atmosphere and land.