title: Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine.
abstract: Rising global temperature and CO2levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L-1) or elevated (800 μmol mol-1) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2(LTAC), elevated temperature/ambient CO2(ETAC), or elevated temperature/elevated CO2(ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus Our findings suggest that exposure to elevated temperature and CO2during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2also impaired freezing tolerance. However, unless the frequency and timing of extreme low-temperature events changes, this is unlikely to increase risk of freezing damage in P. strobus seedlings.
authors: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6 (C.Y.C., E.F., I.E.);Graduate Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5 (C.Y.C., E.F., I.E.);Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (F.U., S.D.M.); andGraduate Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2 (I.E.).
authors: Christine Y
authors: 0000-0001-6609-3527
authors: CY
authors: Chang
authors: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6 (C.Y.C., E.F., I.E.);Graduate Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5 (C.Y.C., E.F., I.E.);Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (F.U., S.D.M.); andGraduate Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2 (I.E.).
authors: Emmanuelle
authors: 0000-0002-2588-7942
authors: E
authors: Fréchette
authors: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6 (C.Y.C., E.F., I.E.);Graduate Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5 (C.Y.C., E.F., I.E.);Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (F.U., S.D.M.); andGraduate Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2 (I.E.).
authors: Faride
authors: 0000-0003-0842-8741
authors: F
authors: Unda
authors: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6 (C.Y.C., E.F., I.E.);Graduate Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5 (C.Y.C., E.F., I.E.);Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (F.U., S.D.M.); andGraduate Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2 (I.E.).
authors: Shawn D
authors: 0000-0002-0175-554X
authors: SD
authors: Mansfield
authors: Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6 (C.Y.C., E.F., I.E.);Graduate Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada M5S 3G5 (C.Y.C., E.F., I.E.);Department of Wood Science, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 (F.U., S.D.M.); andGraduate Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 3B2 (I.E.) ingo.ensminger@utoronto.ca.
authors: Ingo
authors: 0000-0001-9014-2499
authors: I
authors: Ensminger
mesh_terms: D000222:Adaptation, Physiological; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D003080:Cold Temperature; D005615:Freezing; D015151:Immunoblotting; D013058:Mass Spectrometry; D017440:Photoperiod; D010788:Photosynthesis / Q000502:physiology*; D028223:Pinus / Q000378:metabolism / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism; D012621:Seasons; D036226:Seedlings / Q000378:metabolism / Q000502:physiology; D013696:Temperature; D013997:Time Factors
chemical_list: D010940:Plant Proteins; C070556:dehydrin proteins, plant; D002734:Chlorophyll; D002245:Carbon Dioxide