Genotype differences in ¹³C discrimination between atmosphere and leaf matter match differences in transpiration efficiency at leaf and whole‐plant levels in hybrid Populus deltoides ×nigra

Abstract

13C discrimination between atmosphere and bulk leaf matter (D 13 Clb) is frequently used as a proxy for transpiration efficiency (TE). Nevertheless, its relevance is challenged due to: (1) potential deviations from the theoretical discrimination model, and (2) complex time integration and upscaling from leaf to whole plant. Six hybrid genotypes of Populus deltoides ¥ nigra genotypes were grown in climate chambers and tested for whole-plant TE (i.e. accumulated biomass/water transpired). Net CO2 assimilation rates (A) and stomatal conductance (gs) were recorded in parallel to: (1) 13 C in leaf bulk material (d 13 Clb) and in soluble sugars (d 13 Css) and (2) 18 O in leaf water and bulk leaf material. Genotypic means of d 13 Clb and d 13 Css were tightly correlated. Discrimination between atmosphere and soluble sugars was correlated with daily intrinsic TE at leaf level (daily mean A/gs), and with whole-plant TE. Finally, gs was positively correlated to 18 O enrichment of bulk matter or water of leaves at individual level, but not at genotype level. We conclude that D 13 Clb captures efficiently the genetic variability of whole-plant TE in poplar. Nevertheless, scaling from leaf level to whole-plant TE requires to take into account water losses and respiration independent of photosynthesis, which remain poorly documented.

Seasonal variations in photosynthesis, intrinsic water-use efficiency and stable isotope composition of poplar leaves in a short-rotation plantation

“…Previous studies on poplars have suggested that variations among genotypes are generally driven by variations in g s (Monclus et al 2006, Fichot et al 2011, Rasheed et al 2011, Cao et al 2012) although one opposite result has been reported (Rasheed et al 2013). Our results suggest that variations in WUE i across dates and genotypes were primarily driven by variations in g s-sat .…”

“…Substantial species and genotypic variation in whole-plant WUE have been reported (Cernusak et al 2007, Linderson et al 2007, Rasheed et al 2013). At the leaf level, intrinsic water-use efficiency (WUE i ) is defined as the instantaneous ratio between net CO 2 assimilation rate ( A ) and stomatal conductance to water vapour ( g s ).…”

“…At the leaf level, intrinsic water-use efficiency (WUE i ) is defined as the instantaneous ratio between net CO 2 assimilation rate ( A ) and stomatal conductance to water vapour ( g s ). The carbon isotope discrimination (Δ 13 C) is expected to scale negatively with WUE i (Farquhar and Richards 1984), and has been commonly used as an indicator of WUE i in poplar (Ripullone et al 2004, Monclus et al 2006, Bonhomme et al 2008, Dillen et al 2008, Fichot et al 2011, Rasheed et al 2013). However, the relationship between Δ 13 C and WUE i can be disturbed because of differences in the respective time of integration (Ponton et al 2002, Ripullone et al 2004) or of variable mesophyll diffusion conductances ( g m ) (Warren and Adams 2006, Soolanayakanahally et al 2009).…”

Carbon isotope compositions (δ13C) of leaf, wood and holocellulose differ among genotypes of poplar and between previous land uses in a short‐rotation biomass plantation

“…; Rasheed et al . ). Because of its integrative nature, the stable carbon isotope ratio (δ 13 C) of plant organic matter has long been used to assess variations in plant WUE (Dawson et al .…”

Magnesium deficiency decreases biomass water-use efficiency and increases leaf water-use efficiency and oxidative stress in barley plants

“…The carbon stable isotope composition of the plant dry matter (δ 13 C) is used as time-integrated indicator for WUE as it represents a measure of plant C assimilation over the period during which dry matter is generated (Wang et al 2013). Low carbon isotope discrimination (Δ 13 C) is seen as indicator of high leaf-WUE (Farquhar et al 1982) and it has been commonly used as an indicator of leaf-WUE in wheat (Farquhar and Richards 1984), poplar (Rasheed et al 2013) and tobacco (Brueck and Senbayram 2009). However, the relationship between Δ 13 C and leaf-WUE can be unbalanced by differences in the respective time of integration (Ripullone et al 2004) or by variable mesophyll diffusion conductances (g m ) (Warren and Adams 2006;Soolanayakanahally et al 2009).…”