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Arthur C Cameron - One of the best experts on this subject based on the ideXlab platform.
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photoperiod and cold treatment regulate flowering of Rudbeckia fulgida goldsturm
Hortscience, 1999Co-Authors: Erik S Runkle, Arthur C Cameron, Royal D Heins, William H CarlsonAbstract:To determine the flowering requirements of Rudbeckia fulgida Ait. 'Goldsturm', plants were grown under 9-hour photoperiods until maturity, then forced at 20 °C under one of seven photoperiods following 0 or 15 weeks of 5 °C. Photoperiods consisted of a 9- hour day that was extended with incandescent lamps to 10, 12, 13, 14, 16, or 24 hours; an additional treatment was a 9-hour day with a 4-hour night interruption (NI). Noncooled 'Goldsturm' remained vegetative under photoperiods ≤13 hours, and essentially all plants flowered under photoperiods ≥14 hours or with a 4-hour NI. Flowering percentages for cooled plants were 6, 56, or ≥84 under 10-, 12-, or ≥13-hour daylengths and NI, respectively. Critical photoperiods were ≈14 or 13 hours for noncooled or cooled plants, respectively, and base photoperiods shifted from 13 to 14 hours before cold treatment to 10 to 12 hours following cold treatment. Within cold treatments, plants under photoperiods ≥14 hours or NI reached visible inflorescence and flowered at the same time and developed the same number of inflorescences. Fifteen weeks of cold hastened flowering by 25 to 30 days and reduced nodes developed before the first inflorescence by 28% to 37%. Cold treatment provided little or no improvement in other measured characteristics, such as flowering percentage and uniformity, flower number, plant height, and vigor.
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effect of forcing temperature on time to flower of coreopsis grandiflora gaillardia grandiflora leucanthemum superbum and Rudbeckia fulgida
Hortscience, 1998Co-Authors: Mei Yuan, William H Carlson, Royal D Heins, Arthur C CameronAbstract:Scheduling crops to flower on specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to quantify the effect of temperature on time to flower and plant appearance of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora (Hogg ex Sweet.) 'Sunray', Gaillardia ×grandiflora (Van Houtte) 'Goblin', and Rudbeckia fulgida (Ait.) 'Goldsturm', and tissue culture-propagated Leucanthemum ×superbum (Bergman ex J. Ingram) 'Snowcap' plants were exposed to 5 °C for 10 weeks and then grown in greenhouse sections set at 15,18,21,24, or 27 °C under 4-hour night-interruption lighting until plants reached anthesis. Days to visible bud (VB), days to anthesis (FLW), and days from VB to FLW decreased as temperature increased. The rate of progress toward FLW increased linearly with temperature, and base temperatures and degree-days of each developmental stage were calculated. For Coreopsis, Leucanthemum, and Rudbeckia, flower size, flower-bud number, and plant height decreased as temperature increased from 15 to 26 °C.
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Effect of forcing temperature on time to flower of Coreopsis grandiflora, Gaillardia×grandiflora, Leucanthemum×superbum, and Rudbeckia fulgida
Hortscience, 1998Co-Authors: Mei Yuan, William H Carlson, D. Heins, Arthur C CameronAbstract:Scheduling crops to flower on specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to quantify the effect of temperature on time to flower and plant appearance of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora (Hogg ex Sweet.) 'Sunray', Gaillardia ×grandiflora (Van Houtte) 'Goblin', and Rudbeckia fulgida (Ait.) 'Goldsturm', and tissue culture-propagated Leucanthemum ×superbum (Bergman ex J. Ingram) 'Snowcap' plants were exposed to 5 °C for 10 weeks and then grown in greenhouse sections set at 15,18,21,24, or 27 °C under 4-hour night-interruption lighting until plants reached anthesis. Days to visible bud (VB), days to anthesis (FLW), and days from VB to FLW decreased as temperature increased. The rate of progress toward FLW increased linearly with temperature, and base temperatures and degree-days of each developmental stage were calculated. For Coreopsis, Leucanthemum, and Rudbeckia, flower size, flower-bud number, and plant height decreased as temperature increased from 15 to 26 °C.
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determining the duration of the juvenile phase of coreopsis grandiflora hogg ex sweet gaillardia grandiflora van houtte heuchera sanguinea engelm and Rudbeckia fulgida ait
Scientia Horticulturae, 1998Co-Authors: Mei Yuan, William H Carlson, Royal D Heins, Arthur C CameronAbstract:Abstract The juvenile phase of Coreopsis grandiflora `Sunray', Gaillardia×grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm' was characterized by exposing plants with 0 to 20 nodes to cold treatments at 5°C. After 0, 10, or 15 weeks cold treatment, plants were grown at constant 20° C under a 9 h photoperiod with 4 h night-interruption lighting (22:00 to 02:00 h; long days) or under a 9 h photoperiod (short days). Based on flowering percentage and time to flower, we concluded that the juvenile phase of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had approximately 8, 16, 19, and 10 nodes, respectively. Coreopsis required cold treatments to flower. A cold treatment was not required for flowering of Gaillardia and Rudbeckia; however, such treatment improved their flowering percentage and greatly accelerated flowering. Increasing cold duration from 10 to 15 weeks did not influence time to flower of Coreopsis, Gaillardia, and Rudbeckia; however, the increase enhanced flowering percentage of Coreopsis and Gaillardia and hastened flowering of Heuchera. Heuchera was a day-neutral plant after ten weeks cold treatment, Rudbeckia was an obligate long-day plant, and Gaillardia and Coreopsis were quantitative long-day plants.
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Determining the duration of the juvenile phase of Coreopsis grandiflora (Hogg ex Sweet.), Gaillardia×grandiflora (Van Houtte), Heuchera sanguinea (Engelm.) and Rudbeckia fulgida (Ait.)
Scientia Horticulturae, 1998Co-Authors: Mei Yuan, William H Carlson, D. Heins, Arthur C CameronAbstract:Abstract The juvenile phase of Coreopsis grandiflora `Sunray', Gaillardia×grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm' was characterized by exposing plants with 0 to 20 nodes to cold treatments at 5°C. After 0, 10, or 15 weeks cold treatment, plants were grown at constant 20° C under a 9 h photoperiod with 4 h night-interruption lighting (22:00 to 02:00 h; long days) or under a 9 h photoperiod (short days). Based on flowering percentage and time to flower, we concluded that the juvenile phase of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had approximately 8, 16, 19, and 10 nodes, respectively. Coreopsis required cold treatments to flower. A cold treatment was not required for flowering of Gaillardia and Rudbeckia; however, such treatment improved their flowering percentage and greatly accelerated flowering. Increasing cold duration from 10 to 15 weeks did not influence time to flower of Coreopsis, Gaillardia, and Rudbeckia; however, the increase enhanced flowering percentage of Coreopsis and Gaillardia and hastened flowering of Heuchera. Heuchera was a day-neutral plant after ten weeks cold treatment, Rudbeckia was an obligate long-day plant, and Gaillardia and Coreopsis were quantitative long-day plants.
Arthur H Chappelka - One of the best experts on this subject based on the ideXlab platform.
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ambient ozone effects on gas exchange and total non structural carbohydrate levels in cutleaf coneflower Rudbeckia laciniata l growing in great smoky mountains national park
Environmental Pollution, 2012Co-Authors: Howard S Neufeld, Arthur H Chappelka, Greg L Somers, Seth J Peoples, A W Davison, Jill E Thomley, Fitzgerald L BookerAbstract:Ozone-sensitive and -tolerant individuals of cutleaf coneflower (Rudbeckia laciniata L.) were compared for their gas exchange characteristics and total non-structural carbohydrates at Purchase Knob, a high elevation site in Great Smoky Mountains National Park, USA. Photosynthesis and stomatal conductance decreased with increased foliar stipple. Sensitive plants had lower photosynthetic rates for all leaves, except the very youngest and oldest when compared to tolerant plants. Stomatal conductance decreased with increasing leaf age, but no ozone-sensitivity differences were found. Lower leaves had less starch than upper ones, while leaves on sensitive plants had less than those on tolerant plants. These results show that ambient levels of ozone in Great Smoky Mountains National Park can adversely affect gas exchange, water use efficiency and leaf starch content in sensitive coneflower plants. Persistence of sensitive genotypes in the Park may be due to physiological recovery in low ozone years.
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cutleaf coneflower Rudbeckia laciniata l response to ozone and ethylenediurea edu
Environmental Pollution, 2009Co-Authors: Zoltan Szantoi, Arthur H Chappelka, R B Muntifering, Greg L SomersAbstract:Abstract Cutleaf coneflower ( Rudbeckia laciniata L.) seedlings were placed into open-top chambers in May, 2004 and fumigated for 12 wks. Nine chambers were fumigated with either carbon-filtered air (CF), non-filtered air (NF) or twice-ambient (2×) ozone (O 3 ). Ethylenediurea (EDU) was applied as a foliar spray weekly at 0 (control), 200, 400 or 600 ppm. Foliar injury occurred at ambient (30%) and elevated O 3 (100%). Elevated O 3 resulted in significant decreases in biomass and nutritive quality. Ethylenediurea reduced percent of leaves injured, but decreased root and total biomass. Foliar concentrations of cell-wall constituents were not affected by EDU alone; however, EDU × O 3 interactions were observed for total cell-wall constituents and lignocellulose fraction. Our results demonstrated that O 3 altered the physiology and productivity of cutleaf coneflower, and although reducing visible injury EDU may be phytotoxic at higher concentrations.
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stomatal behavior of ozone sensitive and insensitive coneflowers Rudbeckia laciniata var digitata in great smoky mountains national park
New Phytologist, 2007Co-Authors: Nancy Grulke, A W Davison, Howard S Neufeld, Mark Roberts, Arthur H ChappelkaAbstract:Summary • Morphological and physiological attributes were assessed to elucidate the underlying mechanisms of ozone (O3) sensitivity in a highly sensitive species, cutleaf coneflower (Rudbeckia laciniata var. digitata). • Foliage at the same height in the canopy on paired O3-sensitive and -insensitive cutleaf coneflowers was assessed for level of foliar symptoms, stomatal density, stomatal responsiveness to dynamic changes in light and leaf-to-air vapor pressure deficit (VPD), steady-state responses to light and CO2, intrinsic transpirational efficiency, and plant water balance. • There were no morphological differences between the sensitivity types that might have contributed to greater O3 uptake in sensitive individuals. Stomata of sensitive plants were less responsive than those of insensitive plants to experimentally increased and decreased light intensities, and to increased VPD. O3-insensitive plants had greater intrinsic transpirational efficiencies, greater maximum assimilation rates under saturating CO2 and light, and greater carboxylation rates. • Different physiological attributes vary independently within an individual plant, which collectively confer sensitivity or insensitivity to O3 injury.
Jo Anne Crouch - One of the best experts on this subject based on the ideXlab platform.
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newly emerged populations of plasmopara halstedii infecting Rudbeckia exhibit unique genotypic profiles and are distinct from sunflower infecting strains
Phytopathology, 2016Co-Authors: Yazmin Rivera, Catalina Salgadosalazar, T J Gulya, Jo Anne CrouchAbstract:The oomycete Plasmopara halstedii emerged at the onset of the 21st century as a destructive new pathogen causing downy mildew disease of ornamental Rudbeckia fulgida (Rudbeckia) in the United States. The pathogen is also a significant global problem of sunflower (Helianthus annuus) and is widely regarded as the cause of downy mildew affecting 35 Asteraceae genera. To determine whether Rudbeckia and sunflower downy mildew are caused by the same genotypes, population genetic and phylogenetic analyses were performed. A draft genome assembly of a P. halstedii isolate from sunflower was generated and used to design 15 polymorphic simple sequence repeat (SSR) markers. SSRs and two sequenced phylogenetic markers measured differentiation between 232 P. halstedii samples collected from 1883 to 2014. Samples clustered into two main groups, corresponding to host origin. Sunflower-derived samples separated into eight admixed subclusters, and Rudbeckia-derived samples further separated into three subclusters. Pre-epidemic Rudbeckia samples clustered separately from modern strains. Despite the observed genetic distinction based on host origin, P. halstedii from Rudbeckia could infect sunflower, and exhibited the virulence phenotype of race 734. These data indicate that the newly emergent pathogen populations infecting commercial Rudbeckia are a different species from sunflower-infecting strains, notwithstanding cross-infectivity, and genetically distinct from pre-epidemic populations infecting native Rudbeckia hosts.
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Newly Emerged Populations of Plasmopara halstedii Infecting Rudbeckia Exhibit Unique Genotypic Profiles and Are Distinct from Sunflower-Infecting Strains
Phytopathology, 2016Co-Authors: Yazmin Rivera, T J Gulya, Catalina Salgado-salazar, Jo Anne CrouchAbstract:The oomycete Plasmopara halstedii emerged at the onset of the 21st century as a destructive new pathogen causing downy mildew disease of ornamental Rudbeckia fulgida (Rudbeckia) in the United States. The pathogen is also a significant global problem of sunflower (Helianthus annuus) and is widely regarded as the cause of downy mildew affecting 35 Asteraceae genera. To determine whether Rudbeckia and sunflower downy mildew are caused by the same genotypes, population genetic and phylogenetic analyses were performed. A draft genome assembly of a P. halstedii isolate from sunflower was generated and used to design 15 polymorphic simple sequence repeat (SSR) markers. SSRs and two sequenced phylogenetic markers measured differentiation between 232 P. halstedii samples collected from 1883 to 2014. Samples clustered into two main groups, corresponding to host origin. Sunflower-derived samples separated into eight admixed subclusters, and Rudbeckia-derived samples further separated into three subclusters. Pre-epid...
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first report of downy mildew caused by plasmopara halstedii on black eyed susan Rudbeckia fulgida cv goldsturm in maryland
Plant Disease, 2014Co-Authors: Yazmin Rivera, Karen Rane, Jo Anne CrouchAbstract:The North American perennial black-eyed Susan (Rudbeckia fulgida cv. Goldsturm) is an important nursery crop, prized by gardeners and landscapers for its persistent bloom and ease of cultivation. In September 2013, disease symptoms characteristic of downy mildew were observed from multiple R. fulgida plants at two commercial nurseries in the Maryland counties of Howard and Anne Arundel. Over 100 R. fulgida were affected by this disease in both nurseries, rendering the plants unmarketable and causing a substantial financial loss. Plants exhibited dark necrotic lesions on the adaxial leaf surface, and sporulating masses of white mycelium on the abaxial leaf surface and on the adaxial in extreme infections. Plants were stunted with a reduced number of blooms. Microscopic visualization showed coenocytic mycelium, hyaline sporangiophores (length 261 to 904 μm; = 557 μm; n = 20) that were straight and monopodially branched at right angles with several terminal branchlets. Sporangia were hyaline, ovoid to ellipt...
Mei Yuan - One of the best experts on this subject based on the ideXlab platform.
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effect of forcing temperature on time to flower of coreopsis grandiflora gaillardia grandiflora leucanthemum superbum and Rudbeckia fulgida
Hortscience, 1998Co-Authors: Mei Yuan, William H Carlson, Royal D Heins, Arthur C CameronAbstract:Scheduling crops to flower on specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to quantify the effect of temperature on time to flower and plant appearance of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora (Hogg ex Sweet.) 'Sunray', Gaillardia ×grandiflora (Van Houtte) 'Goblin', and Rudbeckia fulgida (Ait.) 'Goldsturm', and tissue culture-propagated Leucanthemum ×superbum (Bergman ex J. Ingram) 'Snowcap' plants were exposed to 5 °C for 10 weeks and then grown in greenhouse sections set at 15,18,21,24, or 27 °C under 4-hour night-interruption lighting until plants reached anthesis. Days to visible bud (VB), days to anthesis (FLW), and days from VB to FLW decreased as temperature increased. The rate of progress toward FLW increased linearly with temperature, and base temperatures and degree-days of each developmental stage were calculated. For Coreopsis, Leucanthemum, and Rudbeckia, flower size, flower-bud number, and plant height decreased as temperature increased from 15 to 26 °C.
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Effect of forcing temperature on time to flower of Coreopsis grandiflora, Gaillardia×grandiflora, Leucanthemum×superbum, and Rudbeckia fulgida
Hortscience, 1998Co-Authors: Mei Yuan, William H Carlson, D. Heins, Arthur C CameronAbstract:Scheduling crops to flower on specific dates requires a knowledge of the relationship between temperature and time to flower. Our objective was to quantify the effect of temperature on time to flower and plant appearance of four herbaceous perennials. Field-grown, bare-root Coreopsis grandiflora (Hogg ex Sweet.) 'Sunray', Gaillardia ×grandiflora (Van Houtte) 'Goblin', and Rudbeckia fulgida (Ait.) 'Goldsturm', and tissue culture-propagated Leucanthemum ×superbum (Bergman ex J. Ingram) 'Snowcap' plants were exposed to 5 °C for 10 weeks and then grown in greenhouse sections set at 15,18,21,24, or 27 °C under 4-hour night-interruption lighting until plants reached anthesis. Days to visible bud (VB), days to anthesis (FLW), and days from VB to FLW decreased as temperature increased. The rate of progress toward FLW increased linearly with temperature, and base temperatures and degree-days of each developmental stage were calculated. For Coreopsis, Leucanthemum, and Rudbeckia, flower size, flower-bud number, and plant height decreased as temperature increased from 15 to 26 °C.
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determining the duration of the juvenile phase of coreopsis grandiflora hogg ex sweet gaillardia grandiflora van houtte heuchera sanguinea engelm and Rudbeckia fulgida ait
Scientia Horticulturae, 1998Co-Authors: Mei Yuan, William H Carlson, Royal D Heins, Arthur C CameronAbstract:Abstract The juvenile phase of Coreopsis grandiflora `Sunray', Gaillardia×grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm' was characterized by exposing plants with 0 to 20 nodes to cold treatments at 5°C. After 0, 10, or 15 weeks cold treatment, plants were grown at constant 20° C under a 9 h photoperiod with 4 h night-interruption lighting (22:00 to 02:00 h; long days) or under a 9 h photoperiod (short days). Based on flowering percentage and time to flower, we concluded that the juvenile phase of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had approximately 8, 16, 19, and 10 nodes, respectively. Coreopsis required cold treatments to flower. A cold treatment was not required for flowering of Gaillardia and Rudbeckia; however, such treatment improved their flowering percentage and greatly accelerated flowering. Increasing cold duration from 10 to 15 weeks did not influence time to flower of Coreopsis, Gaillardia, and Rudbeckia; however, the increase enhanced flowering percentage of Coreopsis and Gaillardia and hastened flowering of Heuchera. Heuchera was a day-neutral plant after ten weeks cold treatment, Rudbeckia was an obligate long-day plant, and Gaillardia and Coreopsis were quantitative long-day plants.
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Determining the duration of the juvenile phase of Coreopsis grandiflora (Hogg ex Sweet.), Gaillardia×grandiflora (Van Houtte), Heuchera sanguinea (Engelm.) and Rudbeckia fulgida (Ait.)
Scientia Horticulturae, 1998Co-Authors: Mei Yuan, William H Carlson, D. Heins, Arthur C CameronAbstract:Abstract The juvenile phase of Coreopsis grandiflora `Sunray', Gaillardia×grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm' was characterized by exposing plants with 0 to 20 nodes to cold treatments at 5°C. After 0, 10, or 15 weeks cold treatment, plants were grown at constant 20° C under a 9 h photoperiod with 4 h night-interruption lighting (22:00 to 02:00 h; long days) or under a 9 h photoperiod (short days). Based on flowering percentage and time to flower, we concluded that the juvenile phase of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had approximately 8, 16, 19, and 10 nodes, respectively. Coreopsis required cold treatments to flower. A cold treatment was not required for flowering of Gaillardia and Rudbeckia; however, such treatment improved their flowering percentage and greatly accelerated flowering. Increasing cold duration from 10 to 15 weeks did not influence time to flower of Coreopsis, Gaillardia, and Rudbeckia; however, the increase enhanced flowering percentage of Coreopsis and Gaillardia and hastened flowering of Heuchera. Heuchera was a day-neutral plant after ten weeks cold treatment, Rudbeckia was an obligate long-day plant, and Gaillardia and Coreopsis were quantitative long-day plants.
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Determining the Juvenile Phases of Coreopsis grandiflora, Gaillardia grandiflora, Heuchera sanguinea, and Rudbeckia fulgida
Hortscience, 1995Co-Authors: Mei Yuan, William H Carlson, D. Heins, Arthur C CameronAbstract:Most plants have a postgermination juvenile phase in which flower induction will not occur. Some species require a cold period for flower induction and will not respond to the cold treatments during the juvenile phase. We determined juvenile phases of Coreopsis grandiflora `Sunray', Gaillardia grandiflora `Goblin', Heuchera sanguinea `Bressingham', and Rudbeckia fulgida `Goldsturm'. Plants were exposed to 5C for 0, 10, or 15 weeks when Coreopsis had 0, 2, 4, 6, 8, or 10 leaves (>1 cm); Gallardia, 4, 8, 12, or 16 leaves; Heuchera, 8, 12, 16, or 20 leaves; Rudbeckia, 5, 10, 15, or 20 leaves. Plants were grown under a 4-h night interruption lighting (LD) or under a 9-h photoperiod (SD) after cold treatments. Based on time to flower and final leaf count, the juvenility of Coreopsis, Gaillardia, Heuchera, and Rudbeckia ended when they had about 6, 10, 12, and 15 leaves, respectively. Cold treatments were necessary for flower induction of Coreopsis and Heuchera and they increased the flowering percentage of Gaillardia and Rudbeckia. Heuhera was a day-neutral plant, Rudbeckia was on obligate LD plant, and Gaillardia and Coreopsis were quantitative LD plants.
Howard S Neufeld - One of the best experts on this subject based on the ideXlab platform.
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ambient ozone effects on gas exchange and total non structural carbohydrate levels in cutleaf coneflower Rudbeckia laciniata l growing in great smoky mountains national park
Environmental Pollution, 2012Co-Authors: Howard S Neufeld, Arthur H Chappelka, Greg L Somers, Seth J Peoples, A W Davison, Jill E Thomley, Fitzgerald L BookerAbstract:Ozone-sensitive and -tolerant individuals of cutleaf coneflower (Rudbeckia laciniata L.) were compared for their gas exchange characteristics and total non-structural carbohydrates at Purchase Knob, a high elevation site in Great Smoky Mountains National Park, USA. Photosynthesis and stomatal conductance decreased with increased foliar stipple. Sensitive plants had lower photosynthetic rates for all leaves, except the very youngest and oldest when compared to tolerant plants. Stomatal conductance decreased with increasing leaf age, but no ozone-sensitivity differences were found. Lower leaves had less starch than upper ones, while leaves on sensitive plants had less than those on tolerant plants. These results show that ambient levels of ozone in Great Smoky Mountains National Park can adversely affect gas exchange, water use efficiency and leaf starch content in sensitive coneflower plants. Persistence of sensitive genotypes in the Park may be due to physiological recovery in low ozone years.
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stomatal behavior of ozone sensitive and insensitive coneflowers Rudbeckia laciniata var digitata in great smoky mountains national park
New Phytologist, 2007Co-Authors: Nancy Grulke, A W Davison, Howard S Neufeld, Mark Roberts, Arthur H ChappelkaAbstract:Summary • Morphological and physiological attributes were assessed to elucidate the underlying mechanisms of ozone (O3) sensitivity in a highly sensitive species, cutleaf coneflower (Rudbeckia laciniata var. digitata). • Foliage at the same height in the canopy on paired O3-sensitive and -insensitive cutleaf coneflowers was assessed for level of foliar symptoms, stomatal density, stomatal responsiveness to dynamic changes in light and leaf-to-air vapor pressure deficit (VPD), steady-state responses to light and CO2, intrinsic transpirational efficiency, and plant water balance. • There were no morphological differences between the sensitivity types that might have contributed to greater O3 uptake in sensitive individuals. Stomata of sensitive plants were less responsive than those of insensitive plants to experimentally increased and decreased light intensities, and to increased VPD. O3-insensitive plants had greater intrinsic transpirational efficiencies, greater maximum assimilation rates under saturating CO2 and light, and greater carboxylation rates. • Different physiological attributes vary independently within an individual plant, which collectively confer sensitivity or insensitivity to O3 injury.
