title: The δ18O and δ2H of water in the leaf growth-and-differentiation zone of grasses is close to source water in both humid and dry atmospheres.
abstract: The oxygen and hydrogen isotope composition of water in the leaf growth-and-differentiation zone, LGDZ, (δ18OLGDZ, δ2HLGDZ) of grasses influences the isotopic composition of leaf cellulose (oxygen) and wax (hydrogen) - important for understanding (paleo)environmental and physiological information contained in these biological archives - but is presently unknown. This work determined δ18OLGDZand δ2HLGDZ,18O- and2H-enrichment of LGDZ (∆18OLGDZand ∆2HLGDZ), and the18O- and2H-enrichment of leaf blade water (∆18OLW,∆2HLW) in two C3and three C4grasses grown at high and low vapor pressure deficit (VPD). The proportion of unenriched water (px) in the LGDZ ranged from 0.9 to 1.0 for18O and 1.0 to 1.2 for2H. VPD had no effect on the proportion of18O- and2H-enriched water in the LGDZ, and species effects were small or nonsignificant. Deuterium discrimination caused depletion of2H in LGDZ water, increasing (apparent) px-values > 1.0 in some cases. The isotopic composition of water in the LGDZ was close to that of source water, independent of VPD and much less enriched than previously supposed, but similar to reported xylem water in trees. The well-constrained pxwill be useful in future investigations of oxygen and hydrogen isotopic fractionation during cellulose and wax synthesis, respectively.
authors.affiliation: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising-Weihenstephan, Germany.
authors.forename: Hai Tao
authors.initials: HT
authors.lastname: Liu
authors.affiliation: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising-Weihenstephan, Germany.
authors.forename: Rudi
authors.initials: R
authors.lastname: Schäufele
authors.affiliation: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising-Weihenstephan, Germany.
authors.forename: Xiao Ying
authors.identifier: http://orcid.org/0000-0002-4983-5645
authors.initials: XY
authors.lastname: Gong
authors.affiliation: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising-Weihenstephan, Germany.
authors.forename: Hans
authors.identifier: http://orcid.org/0000-0002-0139-7535
authors.initials: H
authors.lastname: Schnyder
mesh_terms: D002482:Cellulose / Q000737:chemistry; D002980:Climate; D003903:Deuterium / Q000032:analysis*; D006813:Humidity; D010103:Oxygen Isotopes / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry* / Q000254:growth & development*; D006109:Poaceae / Q000737:chemistry* / Q000254:growth & development; D014867:Water; D014885:Waxes / Q000737:chemistry
chemical_list: D010103:Oxygen Isotopes; D014885:Waxes; D014867:Water; D002482:Cellulose; D003903:Deuterium
keywords: C3 and C4 grass species; hydrogen isotope; leaf growth-and-differentiation zone (LGDZ) water; leaf water; oxygen isotope