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  • 1
    Electronic Resource
    Electronic Resource
    The effects of free-air CO2 enrichment and soil water availability on spatial and seasonal patterns of wheat root growth (1999)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 5 (1999), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Spring wheat [ Triticum aestivum (L). cv. Yecora Rojo] was grown from December 1992 to May 1993 under two atmospheric CO2 concentrations, 550 μmol mol–1 for high-CO2 plots, and 370 μmol mol–1 for control plots, using a Free-Air CO2 Enrichment (FACE) apparatus. In addition to the two levels of atmospheric CO2, there were ample and limiting levels of water supply through a subsurface trip irrigation system in a strip, split-plot design. In order to examine the temporal and spatial root distribution, root cores were extracted at six growth stages during the season at in-row and inter-row positions using a soil core device (86 mm ID, 1.0 m length). Such information would help determine whether and to what extent root morphology is changed by alteration of two important factors, atmospheric CO2 and soil water, in this agricultural ecosystem.Wheat root growth increased under elevated CO2 conditions during all observed developmental stages. A maximum of 37% increase in total root dry mass in the FACE vs. Control plots was observed during the period of stem elongation. Greater root growth rates were calculated due to CO2 enhancement until anthesis. During the early vegetative growth, root dry mass of the inter-row space was significantly higher for FACE than for Control treatments suggesting that elevated CO2 promoted the production of first-order lateral roots per main axis. Then, during the reproductive period of growth, more branching of lateral roots in the FACE treatment occurred due to water stress. Significant higher root dry mass was measured in the inter-row space of the FACE plots where soil water supply was limiting. These sequential responses in root growth and morphology to elevated CO2 and reduced soil water supports the hypothesis that plants grown in a high-CO2 environment may better compensate soil-water-stress conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1999.00243.x
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment (1998)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Spring wheat was grown from emergence to grain maturity in two partial pressures of CO2 (pCO2): ambient air of nominally 37 Pa and air enriched with CO2 to 55 Pa using a free-air CO2 enrichment (FACE) apparatus. This experiment was the first of its kind to be conducted within a cereal field without the modifications or disturbance of microclimate and rooting environment that accompanied previous studies. It provided a unique opportunity to examine the hypothesis that continuous exposure of wheat to elevated pCO2 will lead to acclimatory loss of photosynthetic capacity. The diurnal courses of photosynthesis and conductance for upper canopy leaves were followed throughout the development of the crop and compared to model-predicted rates of photosynthesis. The seasonal average of midday photosynthesis rates was 28% greater in plants exposed to elevated pCO2 than in contols and the seasonal average of the daily integrals of photosynthesis was 21% greater in elevated pCO2 than in ambient air. The mean conductance at midday was reduced by 36%. The observed enhancement of photosynthesis in elevated pCO2 agreed closely with that predicted from a mechanistic biochemical model that assumed no acclimation of photosynthetic capacity. Measured values fell below predicted only in the flag leaves in the mid afternoon before the onset of grain-filling and over the whole diurnal course at the end of grain-filling. The loss of enhancement at this final stage was attributed to the earlier senescence of flag leaves in elevated pCO2. In contrast to some controlled-environment and field-enclosure studies, this field-scale study of wheat using free-air CO2 enrichment found little evidence of acclimatory loss of photosynthetic capacity with growth in elevated pCO2 and a significant and substantial increase in leaf photosynthesis throughout the life of the crop.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00320.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photosynthesis and conductance of spring wheat ears: field response to free-air CO2 enrichment and limitations in water and nitrogen supply (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The mid-day responses of wheat ear CO2 and water vapour exchange to full-season CO2 enrichment were investigated using a Free-Air CO2 Enrichment (FACE) apparatus. Spring wheat [Triticum aestivum (L). cv. Yecora Rojo] was grown in two experiments under ambient and elevated atmospheric CO2 (Ca) concentrations (approximately 370 μmol mol−1 and 550 μmol mol−1, respectively) combined first with two irrigation (Irr) schemes (Wet: 100% and Dry: 50% replacement of evapotranspiration) and then with two levels of nitrogen (N) fertilization (High: 350, Low: 70 kg ha−1 N). Blowers were used for Ca enrichment. Ambient Ca plots were exposed to blower induced winds as well the Ca× N but not in the Ca× Irr experiment. The net photosynthesis for the ears was increased by 58% and stomatal conductance (gs) was decreased by 26% due to elevated Ca under ample water and N supply when blowers were applied to both Ca treatments. The use of blowers in the Ca-enriched plots only during the Ca× Irr experiment (blower effect) and Low N supply restricted the enhancement of net photosynthesis of the ear due to higher Ca. In the latter case, the increase of net photosynthesis of the ear amounted to 26%. The decrease in gs caused by higher Ca was not affected by the blower effect and N treatment. The mid-day enhancement of net photosynthesis due to elevated Ca was higher for ears than for flag leaves and this effect was most pronounced under ample water and N supply. The contribution of ears to grain filling is therefore likely to increase in higher Ca environments in the future. In the comparison between Wet and Dry, the higher Ca did not alter the response of net photosynthesis of the ear and gs to Irr. However, Ca enrichment increased the drought tolerance of net photosynthesis of the glume and delayed the increase of the awn portion of net photosynthesis of the ear during drought. Therefore, the role of awns for maintaining high net photosynthesis of the ear under drought may decrease when Ca increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00603.x
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