“…Furthermore, WUE extrapolated from carbon isotope discrimination (Δ 13 C) or WUE derived from δ 13 C data (intrinsic WUE; WUE i ) are used to characterize long‐term trends in the internal regulation of carbon and water uptake and water loss of drought‐stressed plants (Avramova et al, 2019 ; Mininni et al, 2022 ; Seibt et al, 2008 ). Hence, careful selection of drought‐responsive morpho‐physiological trait combinations is important when WUE, in any form, is considered as the key to drought tolerance (Blum, 2005 , 2009 ; Weerarathne et al, 2021 ). Meanwhile, WUE AET , WUE ASC , and WUE i and some other morpho‐agronomic and physiological measures have been used as easily measurable proxy data instead of the time‐consuming and laborious‐to‐measure WUE A in many studies (Feldman et al, 2018 ; Moghaddam et al, 2013 ), including those on forage and pasture species (Ebdon & Kopp, 2004 ; Ghannoum et al, 2002 ; Read et al, 1991 ).…”