title: Nitrogen fertilization and δ18O of CO2have no effect on18O-enrichment of leaf water and cellulose in Cleistogenes squarrosa (C4) - is VPD the sole control?
abstract: The oxygen isotope composition of cellulose (δ18OCel) archives hydrological and physiological information. Here, we assess previously unexplored direct and interactive effects of the δ18O of CO2(δ18OCO2), nitrogen (N) fertilizer supply and vapour pressure deficit (VPD) on δ18OCel,18O-enrichment of leaf water (Δ18OLW) and cellulose (Δ18OCel) relative to source water, and pexpx, the proportion of oxygen in cellulose that exchanged with unenriched water at the site of cellulose synthesis, in a C4grass (Cleistogenes squarrosa). δ18OCO2and N supply, and their interactions with VPD, had no effect on δ18OCel, Δ18OLW, Δ18OCeland pexpx. Δ18OCeland Δ18OLWincreased with VPD, while pexpxdecreased. That VPD-effect on pexpxwas supported by sensitivity tests to variation of Δ18OLWand the equilibrium fractionation factor between carbonyl oxygen and water. N supply altered growth and morphological features, but not18O relations; conversely, VPD had no effect on growth or morphology, but controlled18O relations. The work implies that reconstructions of VPD from Δ18OCelwould overestimate amplitudes of VPD variation, at least in this species, if the VPD-effect on pexpxis ignored. Progress in understanding the relationship between Δ18OLWand Δ18OCelwill require separate investigations of pexand pxand of their responses to environmental conditions.
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Hai Tao
authors: HT
authors: Liu
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Xiao Ying
authors: 0000-0002-4983-5645
authors: XY
authors: Gong
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Rudi
authors: R
authors: Schäufele
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Fang
authors: F
authors: Yang
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Regina Theresia
authors: RT
authors: Hirl
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Anja
authors: A
authors: Schmidt
authors: Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, 85354, Freising, Germany.
authors: Hans
authors: H
authors: Schnyder
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002482:Cellulose / Q000032:analysis / Q000378:metabolism*; D005308:Fertilizers; D009584:Nitrogen / Q000378:metabolism*; D010103:Oxygen Isotopes / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry / Q000378:metabolism*; D006109:Poaceae / Q000378:metabolism*; D055548:Vapor Pressure
chemical_list: D005308:Fertilizers; D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D002482:Cellulose; D009584:Nitrogen
keywords: growth and morphology; leaf water; nitrogen fertilizer; oxygen isotopes in CO2 and water; pexpx; vapour pressure deficit