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dc.contributor.authorHoward, Ava Rose
dc.date.accessioned2014-03-04T16:21:14Z
dc.date.available2014-03-04T16:21:14Z
dc.date.issued2008-12
dc.identifier.otherhoward_ava_r_200812_phd
dc.identifier.urihttp://purl.galileo.usg.edu/uga_etd/howard_ava_r_200812_phd
dc.identifier.urihttp://hdl.handle.net/10724/25208
dc.description.abstractPlants dominate many ecosystems and play a critical role in water cycling. Most plants have a C3 photosynthetic pathway and water losses at night can include both transpiration (Enight) from the canopy and hydraulic redistribution (HR) from roots. The magnitude of water lost in these pathways is highly variable and a better understanding of the relationship between these processes and potential environmental drivers is needed. In greenhouse studies, we examined the effects of manipulating soil water and nitrogen availability on instantaneous measures of leaf conductance (gnight) and Enight in three focal species: Populus angustifolia, P. balsamifera spp. trichocarpa and wild Helianthus annuus. For all species gnight was at least five times greater than minimum leaf conductance, suggesting most gnight and Enight may be regulated. Based on known daytime responses to water limitation, we hypothesized that gnight and Enight would decrease when soil water availability was limited. Results from five studies and all three species supported this hypothesis. Based on the potential for transpiration to increase mass flow of mobile nutrients to roots, we hypothesized that gnight and Enight would increase under limiting soil nitrogen. Results from eight studies and all three species rejected this hypothesis. Nitrogen limitation sufficient to reduce biomass did not affect gnight or Enight when potentially confounding water stress was eliminated. Based on reductions of HR when transpiration is artificially increased by nighttime lighting, we hypothesized that naturally occurring Enight would reduce the magnitude of HR. We tested this hypothesis in the greenhouse using Artemisia tridentata, Helianthus anomalus and Quercus laevis. Suppressing Enight with nighttime canopy bagging resulted in increased HR for A. tridentata and H. anomalus but not Q. laevis. Overall, our studies suggest that gnight and Enight vary in response to soil water but not nutrient availability and can affect the magnitude of HR. Variability in Enight should be incorporated into models of stand and ecosystem water flux. Increased understanding the variability in Enight should also be used to improve estimates of when and to what magnitude HR may play an important role in ecosystem hydrology.
dc.languageeng
dc.publisheruga
dc.rightspublic
dc.subjecttranspiration
dc.subjectconductance
dc.subjectC3
dc.subjectnighttime
dc.subjectnocturnal
dc.subjecthydraulic redistribution
dc.subjecthydraulic lift
dc.subjectplant
dc.subjectsoil water
dc.subjectsoil nitrogen
dc.subjectHelianthus
dc.subjectPopulus
dc.subjectArtemisia
dc.subjectQuercus
dc.titleNighttime water loss from C3 plants
dc.typeDissertation
dc.description.degreePhD
dc.description.departmentPlant Biology
dc.description.majorPlant Biology
dc.description.advisorMarc Van Iersel
dc.description.advisorLisa Donovan
dc.description.committeeMarc Van Iersel
dc.description.committeeLisa Donovan
dc.description.committeeKathrin Stanger-Hall
dc.description.committeeRonald L. Hendrick, Jr.
dc.description.committeeChris J. Peterson


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