title: Latent manganese deficiency increases transpiration in barley (Hordeum vulgare).
abstract: To investigate if latent manganese (Mn) deficiency leads to increased transpiration, barley plants were grown for 10 weeks in hydroponics with daily additions of Mn in the low nM range. The Mn-starved plants did not exhibit visual leaf symptoms of Mn deficiency, but Chl a fluorescence measurements revealed that the quantum yield efficiency of PSII (F(v)/F(m)) was reduced from 0.83 in Mn-sufficient control plants to below 0.5 in Mn-starved plants. Leaf Mn concentrations declined from 30 to 7 microg Mn g(-1) dry weight in control and Mn-starved plants, respectively. Mn-starved plants had up to four-fold higher transpiration than control plants. Stomatal closure and opening upon light/dark transitions took place at the same rate in both Mn treatments, but the nocturnal leaf conductance for water vapour was still twice as high in Mn-starved plants compared with the control. The observed increase in transpiration was substantiated by (13)C-isotope discrimination analysis and gravimetric measurement of the water consumption, showing significantly lower water use efficiency in Mn-starved plants. The extractable wax content of leaves of Mn-starved plants was approximately 40% lower than that in control plants, and it is concluded that the increased leaf conductance and higher transpirational water loss are correlated with a reduction in the epicuticular wax layer under Mn deficiency.
authors.affiliation: Department of Agriculture and Ecology, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Hebbern
authors.forename: Kristian Holst
authors.initials: KH
authors.lastname: Laursen
authors.forename: Anne H
authors.initials: AH
authors.lastname: Ladegaard
authors.forename: Sidsel B
authors.initials: SB
authors.lastname: Schmidt
authors.forename: Pai
authors.initials: P
authors.lastname: Pedas
authors.forename: Dan
authors.initials: D
authors.lastname: Bruhn
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.forename: Dvoralai
authors.initials: D
authors.lastname: Wulfsohn
authors.forename: Søren
authors.initials: S
authors.lastname: Husted
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes / Q000032:analysis; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D001467:Hordeum / Q000378:metabolism*; D008345:Manganese / Q000172:deficiency*; D018515:Plant Leaves / Q000378:metabolism; D018526:Plant Transpiration; D014867:Water / Q000502:physiology; D014885:Waxes / Q000032:analysis
chemical_list: D002247:Carbon Isotopes; D014885:Waxes; D014867:Water; D002734:Chlorophyll; D002245:Carbon Dioxide; D008345:Manganese; D000077194:Chlorophyll A