Potential impacts of climate change on grain sorghum (Sorghum bicolor) productivity were investigated using the CERES-sorghum model in the Decision Support System for Agrotechnology Transfer v4.5. ...The model was first calibrated for a sorghum cultivar grown in a free air CO2 enrichment experiment at the University of Arizona, Maricopa, Arizona, USA in 1998. The model was then validated with an independent dataset collected in 1999. The simulated grain yield, growth, and soil water of sorghum for the both years were in statistical agreement with the corresponding measurements, respectively. Neither simulated nor measured yields responded to elevated CO2, but both were sensitive to water supply. The validated model was then applied to simulate possible effects of climate change on sorghum grain yield and water use efficiency in western North America for the years 2080-2100. The projected CO2 fertilizer effect on grain yield was dominated by the adverse effect of projected temperature increases. Therefore, temperature appears to be a dominant driver of the global climate change influencing future sorghum productivity. These results suggest that an increase in water demand for sorghum production should be anticipated in a future high-CO2 world.
Physiological responses in sour orange trees grown in open-top chambers and exposed to elevated carbon dioxide levels were studied. In particular, enriched/ambient differences in the concentrations ...of rubisco and other soluble proteins in sour orange leaves were examined. The unknown proteins were purified and identified to help understand why the enriched trees can sustain a long-term increase of about 80% in wood and fruit production. The abundances of these proteins generally were lower in CO sub(2)-enriched leaves than in ambient leaves, except in the early and late times of the year when the reverse was true. Evidence supporting the hypothesis that these proteins are vegetative storage proteins (VSPs) is presented. The decline from winter levels may provide a source of nitrogen (N) that is needed for spring branch growth in enriched trees. The N-terminal amino acid sequence is homologous to a VSP found in sweet potato tubers. And immunoelectron microscopy revealed these proteins in mesophyll cell vacuoles, where VSPs commonly are found. Elevated CO sub(2) had little effect on leaf rubisco, suggesting that enhanced branch and fruit growth under enriched CO sub(2) is not correlated with increased breakdown of rubisco.
Separating roots from soil is a laborious and costly process, but a commercially available hydropneumatic root elutriator can semi-automate the job. Hydraulic and pneumatic systems elutriate the ...roots from the soil, while the electrical system controls the on/off functions of the hydraulic system. The extruded steel frame of the elutriator serves a dual purpose; structural support and transport of water and compressed air. Water is transported in the lower and air in the upper part of the hollow inner cavity of the extruded steel frame. They exit the frame into polyethylene tubes that extend to the base of the elutriator. After prolonged use, however, this design feature can become problematic because flow to the elutriator of either system can be blocked at the nozzle inlets with rust particles that originate from the steel frame's inner walls. The blockage increases sample processing time due to dismantling, clearing, and reassembling, which eventually degrades the elutriator. To resolve these problems a 40-mesh (420 micron) in-line stainless steel water filter and a 40-micron in-line bronze air filter were installed in the polyethylene tube lines between the extruded steel frame and the base of the elutriator. These filters were found to reduce nozzle blockage, thereby increasing sample processing efficiency by 10% and improving sample quality.
Concentrations of three soluble proteins with molecular masses of 33, 31 and 21 kDa were measured weekly for a period of 1 year in leaves of sour orange (
Citrus aurantium L.) trees that had been ...grown for 6 years at atmospheric CO
2 concentrations of 400 and 700 ppm. Abundances of the proteins were generally lower in CO
2-enriched leaves than in ambient-treatment leaves during the central portion of the year. Over the early and latter parts of the year, however, they typically were much greater in leaves of the CO
2-enriched trees. The decrease from their high wintertime levels in the CO
2-enriched trees possibly provided a source of nitrogen required for the enhanced new branch growth observed in the spring on the trees growing in CO
2-enriched air. The hypothesis that they are vegetative storage proteins (VSPs) is also supported by the N-terminal amino acid sequence obtained for the 21-kDa protein, which has homology with sporamin B, an implicated storage protein in sweet potato tubers. In addition, immunoelectron microscopy demonstrated the presence of these proteins within amorphous material in the vacuoles of mesophyll cells, where VSPs are commonly located. The fact that elevated CO
2 had little impact on the amount of leaf rubisco suggests that enhanced branch and fruit growth observed in the CO
2-enriched trees was not correlated with an increased rate of breakdown of this major protein, another potential source of the nitrogen. The 33-, 31- and 21-kDa proteins appear to be specific to citrus species, as immunologically related proteins were detected in a variety of orange, grapefruit, lemon, tangelo and kumquat trees, but were not found in a large number of herbaceous plants and unrelated woody species.
• To determine the response of C4 plants to elevated CO2 it is necessary to establish whether young leaves have a fully developed C4 photosynthetic apparatus, and whether photosynthesis in these ...leaves is responsive to elevated CO2. • The effect of free-air CO2 enrichment (FACE) on the photosynthetic development of the C4 crop Sorghum bicolor was monitored. Simultaneous measurements of chlorophyll a fluorescence and carbon assimilation were made to determine energy utilization, quantum yields of carbon fixation (φ CO2) and photosystem II (φPSII), as well as photorespiration. • Assimilation in the second leaf of FACE plants was 37% higher than in control plants and lower apparent rates of photorespiration at growth CO2 concentrations were exhibited. In these leaves, φPSII: φ CO2 was high at low atmospheric CO2 concentration (Ca) due to overcycling of the C4 pump and increased leakiness. As Ca increased, φPSII: φ CO2 decreased as a greater proportion of energy derived from linear electron transfer was used by the C3 cycle. • The stimulation of C4 photosynthesis at elevated Ca in young leaves was partially due to suppressed photorespiration. Additionally, elevated Ca enhanced energy-use efficiency in young leaves, possibly by decreasing CO2 leakage from bundle sheath cells, and by decreasing overcycling of the C4 pump.
COTCO2: a cotton growth simulation model for global change Wall, G.W. (United States Water Conservation Lab., Phoenix, AZ (USA)); Amthor, J.S; Kimball, B.A
Agricultural and forest meteorology,
09/1994, Letnik:
70, Številka:
1-4
Journal Article
Abstract
Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of ...leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using free-air CO2 enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO2 uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO2 did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO2 uptake remained higher under elevated CO2. Acclimation at elevated CO2 was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO2 led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO2 therefore depended on both vertical position within the canopy and the developmental stage.
Previous
studies of photosynthetic acclimation to elevated CO
2
have
focused on the most recently expanded, sunlit leaves in the canopy. We
examined acclimation in a vertical profile of leaves ...through a canopy
of wheat (
Triticum aestivum
L.). The crop was grown at
an elevated CO
2
partial pressure of 55 Pa within a
replicated field experiment using free-air CO
2
enrichment.
Gas exchange was used to estimate in vivo carboxylation capacity and
the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis.
Net photosynthetic CO
2
uptake was measured for leaves in
situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC)
proteins, and total N were determined. Elevated CO
2
did not
affect carboxylation capacity in the most recently expanded leaves but
led to a decrease in lower, shaded leaves during grain development.
Despite this acclimation, in situ photosynthetic CO
2
uptake
remained higher under elevated CO
2
. Acclimation at elevated
CO
2
was accompanied by decreases in both Rubisco and total
leaf N contents and an increase in LHC content. Elevated
CO
2
led to a larger increase in LHC/Rubisco in lower canopy
leaves than in the uppermost leaf. Acclimation of leaf photosynthesis
to elevated CO
2
therefore depended on both vertical
position within the canopy and the developmental stage.
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