title: Elevated [CO2] does not ameliorate the negative effects of elevated temperature on drought-induced mortality in Eucalyptus radiata seedlings.
abstract: It has been reported that elevated temperature accelerates the time-to-mortality in plants exposed to prolonged drought, while elevated [CO(2)] acts as a mitigating factor because it can reduce stomatal conductance and thereby reduce water loss. We examined the interactive effects of elevated [CO(2)] and temperature on the inter-dependent carbon and hydraulic characteristics associated with drought-induced mortality in Eucalyptus radiata seedlings grown in two [CO(2)] (400 and 640 μL L(-1)) and two temperature (ambient and ambient +4 °C) treatments. Seedlings were exposed to two controlled drying and rewatering cycles, and then water was withheld until plants died. The extent of xylem cavitation was assessed as loss of stem hydraulic conductivity. Elevated temperature triggered more rapid mortality than ambient temperature through hydraulic failure, and was associated with larger water use, increased drought sensitivities of gas exchange traits and earlier occurrence of xylem cavitation. Elevated [CO(2)] had a negligible effect on seedling response to drought, and did not ameliorate the negative effects of elevated temperature on drought. Our findings suggest that elevated temperature and consequent higher vapour pressure deficit, but not elevated [CO(2)], may be the primary contributors to drought-induced seedling mortality under future climates.
authors.affiliation: Hawkesbury Institute for the Environment, Hawkesbury Campus, University of Western Sydney, Locked Bag 1797, Penrith, New South Wales, 2751, Australia.
authors.forename: Honglang
authors.initials: H
authors.lastname: Duan
authors.forename: Remko A
authors.initials: RA
authors.lastname: Duursma
authors.forename: Guomin
authors.initials: G
authors.lastname: Huang
authors.forename: Renee A
authors.initials: RA
authors.lastname: Smith
authors.forename: Brendan
authors.initials: B
authors.lastname: Choat
authors.forename: Anthony P
authors.initials: AP
authors.lastname: O'Grady
authors.forename: David T
authors.initials: DT
authors.lastname: Tissue
mesh_terms: D018533:Biomass; D002241:Carbohydrates / Q000032:analysis; D002245:Carbon Dioxide / Q000494:pharmacology*; D055864:Droughts; D005052:Eucalyptus / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D010788:Photosynthesis / Q000187:drug effects; D063245:Plant Development / Q000187:drug effects / Q000528:radiation effects; D018547:Plant Stems / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development* / Q000528:radiation effects; D012987:Soil / Q000737:chemistry; D013696:Temperature; D014867:Water
chemical_list: D002241:Carbohydrates; D012987:Soil; D014867:Water; D002245:Carbon Dioxide
keywords: carbohydrates; drought; elevated temperature; eucalyptus; hydraulic failure; rising [CO2]