title: δ(13) C of leaf-respired CO(2) reflects intrinsic water-use efficiency in barley.
abstract: Leaf intrinsic water-use efficiency (WUE), the ratio of photosynthetic rate to stomatal conductance (A/g(s) ), is a key plant trait linking terrestrial carbon and water cycles. A rapid, integrative proxy for A/g(s) is of benefit to crop breeding programmes aiming to improve WUE, but also for ecologists interested in plant carbon-water balance in natural systems. We hypothesize that the carbon isotope composition of leaf-respired CO(2) (δ(13) C(Rl) ), two hours after leaves are transferred to the dark, records photosynthetic carbon isotope discrimination and so provides a proxy for A/g(s) . To test this hypothesis, δ(13) C(Rl) was measured in four barley cultivars grown in the field at two levels of water availability and compared to leaf-level gas exchange (the ratio of leaf intercellular to ambient CO(2) partial pressure, C(i) /C(a) , and A/g(s) ). Leaf-respired CO(2) was more (13) C-depleted in plants grown at higher water availability, varied between days as environmental conditions changed, and was significantly different between cultivars. A strong relationship between δ(13) C(Rl) and δ(13) C of sucrose was observed. δ(13) C(Rl) was converted into apparent photosynthetic discrimination (Δ(13) C(Rl) ) revealing strong relationships between Δ(13) C(Rl) and C(i) /C(a) and A/g(s) during the vegetative stage of growth. We therefore conclude that δ(13) C(Rl) may provide a rapid, integrative proxy for A/g(s) in barley.
authors.affiliation: Faculty of Agriculture, Food and Natural Resources, The University of Sydney, Private Bag 4011, Narellan NSW 2567, Australia. margaret.barbour@sydney.edu.au
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Barbour
authors.forename: Guillaume
authors.initials: G
authors.lastname: Tcherkez
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Bickford
authors.forename: Caroline
authors.initials: C
authors.lastname: Mauve
authors.forename: Marlene
authors.initials: M
authors.lastname: Lamothe
authors.forename: Sarah
authors.initials: S
authors.lastname: Sinton
authors.forename: Hamish
authors.initials: H
authors.lastname: Brown
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D001467:Hordeum / Q000254:growth & development / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology*; D018526:Plant Transpiration; D013395:Sucrose / Q000032:analysis; D014867:Water / Q000502:physiology*
chemical_list: D002247:Carbon Isotopes; D014867:Water; D002245:Carbon Dioxide; D013395:Sucrose; D009584:Nitrogen