Accounting for mesophyll conductance substantially improves 13C‐based estimates of intrinsic water‐use efficiency. Issue 3 (25th October 2020)

• Record Type: Journal Article
• Authors: Ma, Wei Ting; Tcherkez, Guillaume; Wang, Xu Ming; Schäufele, Rudi; Schnyder, Hans; Yang, Yusheng; Gong, Xiao Ying
• Is Part Of: New phytologist. Volume 229:Issue 3(2021)
• Page Start: 1326
• Page End: 1338
• Publication Date: 2020-10-25
• Subjects: 13C discrimination -- drought stress -- mesophyll conductance -- photosynthesis -- stable isotope -- stomatal conductance -- transpiration -- water‐use efficiency; Botany -- Periodicals; 580
• DOI: 10.1111/nph.16958
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: Carbon isotope discrimination (Δ) has been used widely to infer intrinsic water‐use efficiency (iWUE) of C3 plants, a key parameter linking carbon and water fluxes. Despite the essential role of mesophyll conductance ( g m ) in photosynthesis and Δ, its effect on Δ‐based predictions of iWUE has generally been neglected. Here, we derive a mathematical expression of iWUE as a function of Δ that includes g m (iWUEmes ) and exploits the g m ‐stomatal conductance ( g sc ) relationship across drought‐stress levels and plant functional groups (deciduous or semideciduous woody, evergreen woody and herbaceous species) in a global database. iWUEmes was further validated with an independent dataset of online‐Δ and CO2 and H2 O gas exchange measurements with seven species. Drought stress reduced g sc and g m by nearly one‐half across all plant functional groups, but had no significant effect on the g sc : g m ratio, with a well supported value of 0.79 ± 0.07 (95% CI, n = 198). g m was negatively correlated to iWUE. Incorporating the g sc : g m ratio greatly improved estimates of iWUE, compared with calculations that assumed infinite g m . The inclusion of the g sc : g m ratio, fixed at 0.79 when g m was unknown, proved desirable to eliminate significant errors in estimating iWUE from Δ across various C3 vegetation types.