title: Factors preventing the performance of oxygen isotope ratios as indicators of grain yield in maize.
abstract: This paper provides new insights into source-sink relationships and transpiration processes which will eventually help to interpret δ (18) O as a genotype selection and ecophysiological tool for maize adaptation to drought. Oxygen isotope composition (δ(18)O) has been proposed as a phenotyping tool to integrate leaf transpiration in C4 crops, such as maize. Within this context we hypothesize that δ(18)O in leaves may reflect primarily environmental and genetic variability in evaporative processes, but that this signal may become dampened in transit from source to sink tissues. The aim of this study was to assess the relative importance of transpirative or translocation-related factors affecting δ(18)O in plant tissues of maize. We performed two water regime experiments, one with two varieties under semi-controlled conditions, and another in the field with 100 genotypes during two consecutive years. The δ(18)O in organic matter at the leaf base was strongly correlated with the δ(18)O in stem water, indicating that it could be a good proxy for source water in extensive samplings. Compared to leaves, we observed an (18)O depletion in silks and grains, but not in stem-soluble organic matter. We interpret this as evidence of exchange with unenriched water from source to sink, but mainly occurring within sink tissues. Although grain yield (GY) and physiological variables did not show clear intra-trial patterns against δ(18)O, the only tissues that correlated with GY in the linear regression approach were that of silks, giving an insight of evapotranspirative demand during female flowering and thus of potential maize lines that are better adapted to drought. This finding will eventually help to interpret δ(18)O as a genotype selection and ecophysiological tool for the adaption of maize and other crops to drought, offering insight into source-sink relationships and transpiration processes.
authors.affiliation: Unitat de Fisiología Vegetal, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain. rutsanchez@ub.edu.
authors.forename: Rut
authors.initials: R
authors.lastname: Sánchez-Bragado
authors.affiliation: Unitat de Fisiología Vegetal, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain. jaraus@ub.edu.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Araus
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, Freiburg im Breisgau, Germany. ursula.scheerer@ctp.uni-freiburg.de.
authors.forename: Ursula
authors.initials: U
authors.lastname: Scheerer
authors.affiliation: International Maize and Wheat Improvement Center (CIMMYT), Harare, Zimbabwe. j.cairns@cgiar.org.
authors.forename: Jill E
authors.initials: JE
authors.lastname: Cairns
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, Freiburg im Breisgau, Germany. heinz.rennenberg@ctp.uni-freiburg.de.
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, Freiburg im Breisgau, Germany. pitter.ferrio@pvcf.udl.es.|Department of Crop and Forest Sciences-AGROTECNIO Center, Universitat de Lleida, Avda. Rovira Roure 191, 25198, Lleida, Spain. pitter.ferrio@pvcf.udl.es.
authors.forename: Juan Pedro
authors.initials: JP
authors.lastname: Ferrio
mesh_terms: D055864:Droughts; D005838:Genotype; D010100:Oxygen / Q000378:metabolism*; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000235:genetics*; D013312:Stress, Physiological / Q000235:genetics*; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development / Q000502:physiology
chemical_list: D010100:Oxygen
keywords: Corn; Drought tolerance; Grain; Leaf; Organic matter; Stable isotopes; Stem water; Translocational