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Kim E. Tripp, William K. Kroen, Mary M. Peet, and Daniel H. Willits

Eight tomato (Lycopersicon esculentum) cultivars were grown for 16 weeks in greenhouses enriched for an average of 8.1 hours daily to 1000 μl CO /liter of air or in greenhouses maintained at ambient CO. Carbon dioxide enrichment significantly decreased the mean number of greenhouse whiteflies [Trialeurodes vaporariorum (Westward), Homoptera: Aleyrodidae] as measured by counts from commercial yellow sticky traps. The number of whiteflies present was negatively correlated with both seasonal foliar C: N ratio and percent C but positively correlated with percent N in the foliage. Thus, CO enrichment apparently alters plant composition in such a way as to reduce significantly the population growth of greenhouse whiteflies.

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Xiaojie Zhao, Guihong Bi, Richard L. Harkess, Jac J. Varco, and Eugene K. Blythe

, NupE showed a more dynamic response to N availability from applied N ( Iversen et al., 2010 ). C/N ratio of biomass may indicate relative availability of C and N sources ( Herms and Mattson, 1992 ). Carbon constitutes ≈50% of plant DW and provides the

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Jen-An Lin and Yao-Chien Alex Chang

phalaenopsis is mainly controlled by low temperature, mineral nutrition also plays an important role in flowering ( Lee and Lin, 1987 ; Poole and Seeley, 1978 ; Sheehan, 1961 ; Tanaka et al., 1988 ). Ratio of tissue C and N is called C/N ratio. In the

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Mohammed B. Tahboub, William C. Lindemann, and Leigh Murray

and immobilization are largely determined by the C:N ratio of the substrate organic matter ( Paul and Juma, 1981 ; Van Veen et al., 1984 ). At optimum environmental conditions, if the incorporated organic matter has a high N content (low C:N ratio

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Mohammed B. Tahboub, William C. Lindemann, and Leigh Murray

resulting chips were generally long (2.5 to 5.0 cm in length) and narrow (2.4 to 7.9 mm in diameter). A more thorough description of wood chips was previously given ( Tahboub et al., 2007 ). Pecan wood chips (C : N ratio of 143 : 1) were incorporated (disked

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Yiwei Jiang, Yaoshen Li, Gang Nie, and Huifen Liu

( Brauer et al., 2011 ), demonstrating that N partitioning in rice during grain filling could be altered by GS1 . However, overexpressing OsGS1;1 and OsGS1;2 resulted in poor plant growth, yield and decreased C:N ratio in the stem of rice, indicating

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Maria Gannett, Marvin P. Pritts, and Johannes Lehmann

biological properties by providing soil amendments varying in C:N ratios and tilling at two different depths, and then determine if these had an impact on soil health indicators, plant establishment, growth, and yield. We hypothesized that adding soil

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Carolyn F. Scagel, Richard P. Regan, and Guihong Bi

increased rate of N application from UF in 2005 ( Table 1 ). Biomass, N content, and N concentration in all tissues in Nov. 2005 increased, but C/N ratios decreased with increasing rate of N application from UF in 2005 ( Table 1 ). Increasing N rate

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J.P. Syvertsen, L.S. Lee, and J.W Grosser

Diploid (2x) and autotetraploid (4x) Citrus L. rootstock cultivars were grown at elevated CO2 to obtain insights into limitations on growth and net gas exchange that have been associated with tetraploidy. Well-nourished 2x and 4x seedlings of `Volkamer' lemon (Volk, C. volkameriana Ten & Pasq.), `Troyer' citrange [Troy, C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.] and `Cleopatra' mandarin (Cleo, C. reticulata Blanco.), were grown in greenhouses at either ambient or twice ambient CO2 for 4 months. Plant growth, water relations, mineral nutrition, and net gas exchange characteristics of leaves were measured. Most 4x plants were smaller and had lower rates of whole plant transpiration but shorter fibrous roots than 2x plants. Fibrous roots of 4x were thicker than 2x roots as indicated by a lower specific root length (SRL) in 4x than in 2x roots. Root hydraulic conductivity was correlated to total plant growth but there were no effects of CO2 or ploidy on root conductivity. Tetraploid leaves had lower N concentrations than 2x leaves when expressed on a dry weight basis but these differences disappeared when N concentration was expressed on an leaf area basis because 4x leaves had more leaf dry weight per area (LDW/a) than 2x leaves. Plant growth was greater and SRL was lower at elevated CO2 than at ambient CO2. LDW concentrations of N, P, and K were lower at elevated CO2 than at ambient apparently due to a growth dilution effect. LDW/a, net CO2 assimilation (ACO2), and leaf water use efficiency were greater at elevated CO2 than at ambient. Overall, there was no effect of ploidy on ACO2 but 4x Volk and Troy had lower rates of ACO2 than their 2x at elevated CO2. Net gas exchange of tetraploid leaves was less responsive to elevated CO2 than 2x leaves. The low SRL of tetraploids was correlated with low whole plant transpiration rates and low leaf area-based N concentrations, which may be operative in determining the growth characteristics associated with tetraploidy.

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Carolyn F. Scagel, Richard P. Regan, Rita Hummel, and Guihong Bi

in N and C export, import, or metabolism and differences in C/N ratios were used to assess the magnitude of loss and accumulation when concurrent changes in C and N concentrations occurred. Biomass of old stems on container-grown deciduous and