Summary
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Sorghum (Sorghum bicolor) was grown for two consecutive seasons at Maricopa, AZ, USA, using the free‐air CO2 enrichment (FACE) approach to investigate evapotranspiration of this C4 plant ...at ample and limited water supplies.
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Crop evapotranspiration (ET) was measured using two CO2 concentrations (control, c. 370 µmol mol−1; FACE, ambient +200 µmol mol−1) and two irrigation treatments (well watered and water‐limited). Volumetric soil water content was measured before and after each irrigation using neutron scattering techniques.
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Averaged over both years, elevated CO2 reduced cumulative ET by 10% when plants were given ample water and by 4% under severe drought stress. Water‐use efficiency based on grain yield (WUE‐G) increased, due to CO2 enrichment, by 9% and 19% in wet and dry plots, respectively; based on total biomass, water‐use efficiency (WUE‐B) increased by 16% and 17% in wet and dry plots, respectively.
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These data suggest that in the future high‐CO2 environment, water requirements for irrigated sorghum will be lower than at present, while dry‐land productivity will increase, provided global warming is minimal.
Increasing atmospheric carbon dioxide (CO2) likely will affect future water requirements of most plants, including agricultural crops. This research quantifies such effects on the energy balance and ...evapotranspiration (ET) of sorghum (Sorghum bicolor (L.) Moench, a C4 grain crop) using a residual energy balance approach. During the summer and autumn of 1998 and 1999, sorghum was grown under free-air CO2 enrichment (FACE) conditions near Maricopa, Arizona. Latent heat flux (λET) was determined by subtracting soil heat flux (G0) and sensible heat flux (H) from net radiation (Rn) values in both Control CO2 plots (about 370 μmol mol-1) and FACE plots (Control + 200 μmol mol-1). Rn was observed using net radiometers. G0 was measured with soil heat flux plates at a depth of 10 mm, then corrected for heat storage above the plates. H was determined using measurements of air temperature from aspirated psychrometers, leaf temperature from infrared thermometers, and wind data from a three-cup anemometer. Both FACE and Control plots were divided into semicircular halves to allow a well-watered (Wet) treatment and a drought-stressed (Dry) treatment. This allowed comparisons of the FACE effect on ET in normal and water-stressed conditions. Under Wet conditions, FACE decreased λET by 13.8±1.8% in 1998, and 11.8±1.9% in 1999. Drought-stress resulted in a reduction in λET of 8.5±3.7% for the FACE treatments in 1998, but an increase in λET of 10.5±5.1% in 1999. When soil water was readily available, midday canopy temperatures in the FACE plots were increased by 1.47±0.09 °C in 1998, and 1.85±0.20 °C in 1999, indicative of increased stomatal resistance due to CO2 enrichment. These data suggest that soil water availability is a determining factor for the FACE effect. Water use efficiency (WUE) increased about 28% due to elevated CO2 under Wet conditions due to a savings of water for about the same growth, whereas under Dry conditions it increased about 16% due to much greater relative growth on only a slightly higher amount of water.
Summary
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The likely consequences of future high levels of atmospheric CO2 concentration on wheat (Triticum aestivum L.) grain nutritional and baking quality were determined.
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Two free‐air CO2 ...enrichment (FACE; 550 mmol mol−1) experiments were conducted at ample (Wet) and limiting (Dry) levels of irrigation, and a further two experiments at ample (High‐N) and limiting (Low‐N) nitrogen concentrations. Harvested grain samples were subjected to a battery of nutritional and bread‐making quality tests.
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The Dry treatment improved grain quality slightly (protein +2%; bread loaf volume +3%). By contrast, Low‐N decreased quality drastically (protein −36%; loaf volume −26%). At ample water and N, FACE decreased quality slightly (protein −5%; loaf volume −2%) in the irrigation experiments and there was no change in the nitrogen experiments. At Low‐N, FACE tended to make the deleterious effects of Low‐N worse (protein −33% and −39%, at ambient CO2 and FACE, respectively; loaf volume −22% and −29% at ambient CO2 and FACE, respectively).
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The data suggest that future elevated CO2 concentrations will exacerbate the deleterious effects of low soil nitrogen on grain quality, but with ample nitrogen fertilizer, the effects will be minor.
Summary
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Atmospheric CO2 concentration is expected to increase by 50% near the middle of this century. The effects the free air CO2 enrichment (FACE) is presented here on growth and development of ...field‐grown grain sorghum (Sorghum bicolor) at ample (wet) and limiting (dry) levels of irrigation water at Maricopa, AZ, USA.
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Daytime CO2 mole fractions were 561 and 368 µmol mol−1 for the FACE and control treatments, respectively. Irrigation plus precipitation averaged 1132 mm for the wet plots and 396 mm in the dry plots.
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During the growing season, FACE increased biomass accumulation in the dry plots but the effects in the wet plots were inconsistent. At final harvest, FACE increased total yield from 999 to 1151 g m−2 in the dry plots and had no effect in the wet plots.
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If atmospheric CO2 continues to increase, total sorghum yield is likely to be higher in the future in areas where water is limited.
The patterns of disease recurrence after resection of pancreatic ductal adenocarcinoma with adjuvant chemotherapy remain unclear.
To define patterns of recurrence after adjuvant chemotherapy and the ...association with survival.
Prospectively collected data from the phase 3 European Study Group for Pancreatic Cancer 4 adjuvant clinical trial, an international multicenter study. The study included 730 patients who had resection and adjuvant chemotherapy for pancreatic cancer. Data were analyzed between July 2017 and May 2019.
Randomization to adjuvant gemcitabine or gemcitabine plus capecitabine.
Overall survival, recurrence, and sites of recurrence.
Of the 730 patients, median age was 65 years (range 37-81 years), 414 were men (57%), and 316 were women (43%). The median follow-up time from randomization was 43.2 months (95% CI, 39.7-45.5 months), with overall survival from time of surgery of 27.9 months (95% CI, 24.8-29.9 months) with gemcitabine and 30.2 months (95% CI, 25.8-33.5 months) with the combination (HR, 0.81; 95% CI, 0.68-0.98; P = .03). The 5-year survival estimates were 17.1% (95% CI, 11.6%-23.5%) and 28.0% (22.0%-34.3%), respectively. Recurrence occurred in 479 patients (65.6%); another 78 patients (10.7%) died without recurrence. Local recurrence occurred at a median of 11.63 months (95% CI, 10.05-12.19 months), significantly different from those with distant recurrence with a median of 9.49 months (95% CI, 8.44-10.71 months) (HR, 1.21; 95% CI, 1.01-1.45; P = .04). Following recurrence, the median survival was 9.36 months (95% CI, 8.08-10.48 months) for local recurrence and 8.94 months (95% CI, 7.82-11.17 months) with distant recurrence (HR, 0.89; 95% CI, 0.73-1.09; P = .27). The median overall survival of patients with distant-only recurrence (23.03 months; 95% CI, 19.55-25.85 months) or local with distant recurrence (23.82 months; 95% CI, 17.48-28.32 months) was not significantly different from those with only local recurrence (24.83 months; 95% CI, 22.96-27.63 months) (P = .85 and P = .35, respectively). Gemcitabine plus capecitabine had a 21% reduction of death following recurrence compared with monotherapy (HR, 0.79; 95% CI, 0.64-0.98; P = .03).
There were no significant differences between the time to recurrence and subsequent and overall survival between local and distant recurrence. Pancreatic cancer behaves as a systemic disease requiring effective systemic therapy after resection.
ClinicalTrials.gov identifier: NCT00058201, EudraCT 2007-004299-38, and ISRCTN 96397434.
•The upper homeostatic temperature range of irrigated US wheat is between 25°C and 30°C.•Absolute temperature exposure models overestimate the upper homeostatic range.•Relative temperature exposure ...models integrate temperature effects on growth and development.•Crop yield survey data obscure the temperature response due to their low interannual variability.
High temperature (HT) and drought (D) have detrimental effects on growth and phenology that result in reductions of the yields of agricultural crops. Nevertheless, homeostatic ranges of tolerance exist. Recent analysis of survey data and simulations suggest US wheat (Triticum aestivum L.) yields remain relatively stable under irrigation in the range of 35°– 40°C. Applying analogue statistical procedures on experimental data and simulations from the Hot Serial Cereal Experiment (HSC) we demonstrate that failed incorporation of the corresponding phenological acceleration due to HT and a low interannual temperature variability lead to this result. Here, we incorporate the phenological effect into the used binned temperature exposure yield model by rescaling (normalizing) the absolute seasonal temperature counts to a maximum season length. The application to observed and simulated HSC data with a wide temperature range reveals that the suggested upper homeostatic response limit of US wheat yields to HT requires a down–revision. HT stress can be reduced by transpirational cooling. However, the effect is currently not sufficient to expand the homeostatic range of irrigated wheat markedly beyond 25°C taking our analysis of the HSC experiment.
The global impact of an increased concentration of CO
2 in the atmosphere on plants has been studied extensively, but little information has been published on the effect of enrichment of atmospheric ...CO
2 on the nutritive value of grain and straw used as ruminant feeds. This paper reports the chemical composition and nutritive value of grain and straw harvested from the drought tolerant hard red spring wheat (
Triticum aestivum L.) variety Yecora Rojo managed with two carbon dioxide regimes (ambient, 350
μl/l and elevated, 550
μl/l), two rates of nitrogen application (low N: 53
kg
N/ha and high N: 393
kg
N/ha) grown under a water-fed (
i.e., no deficit) regime. Accumulation of carbon in straw did not differ among crops grown under elevated CO
2 and low N supplementation and crops grown under ambient CO
2 with low levels of N supplementation. Increased N application increased sequestration of C (P<0.05) compared to straw from crops grown under ambient CO
2 concentration. Low levels of N application and elevated CO
2 led to straw containing similar concentrations of N to those grown under ambient CO
2 conditions. Increasing N application to crops grown under ambient concentrations of CO
2 elevated the concentration of N (P<0.01) whereas crops at elevated concentrations of CO
2 did not accumulate N to the same extent. Differences in the non-structural carbohydrate and cell wall content reflected the patterns for total C. No effect of increasing the concentration of CO
2 on WSC, aNDF
om, ADF
om, hemicellulose, cellulose and lignin (sa) occurred. There was a small decline (−26
g/kg; P<0.05) in the concentration of aNDF
om in straw from crops that had received high N input. The ratio of lignin to total N was higher in straw harvested from plots with elevated CO
2 (33.5:1) compared with ambient CO
2 (24.6:1). No changes in the total C content occurred for grain samples in response to CO
2 concentration or supplemental N fertiliser. No interaction between supply of N and CO
2 concentration occurred. Changes in the total N content of grain in response to treatments were similar to the changes observed in the straw fraction. The increases in concentration of N incorporated into grain were higher from crops grown under enriched concentrations of CO
2 (
i.e., +8.6
g/kg; P<0.01) than for crops grown under ambient supply of CO
2 (+3.5
g/kg; P<0.05). Differences in concentration of starch in the grain with increasing supply of N from fertiliser occurred under FACE conditions (P<0.05), but not for grain harvested from those grown under ambient CO
2 levels. No effect of changing concentrations of CO
2 were observed for ADF
om, lignin (sa), cellulose and neutral detergent cellulose digestibility but concentrations of aNDF
om (P<0.05) and hemicellulose (P<0.05) were higher in grain grown under ambient concentrations of CO
2 irrespective of supply of N to the crop. Although effects of elevated concentrations of CO
2 on grain and straw quality were expected, this poses concerns for livestock production in systems that use lower levels of agronomic inputs. Elevated concentrations of CO
2 in the ambient environment were beneficial for development of above ground biomass and grain yield as measured by thousand-grain weight. However, straw and grain quality, in terms of crude protein and the crude protein to energy ratio will be affected by increasing concentrations of CO
2 in the atmosphere, and this may lead to a reduction in the total supply of crude protein in crops used by livestock.
In order to determine the likely effects of the increasing atmospheric CO2 concentration on future evapotranspiration, ET, plots of field-grown wheat were exposed to concentrations of 550 ...micromol/mol CO2 (or 200 micromol/mol above current ambient levels of about 360 micromol/mol) using a free-air CO2 enrichment (FACE) facility. Data were collected for four growing seasons at ample water and fertilizer (high N) and for two seasons when soil nitrogen was limited (low N). Measurements were made of net radiation, Rn; soil heat flux; air and soil temperatures; canopy temperature, Ts; and wind speed. Sensible heat flux was calculated from the wind and temperature measurements. ET, that is, latent heat flux, was determined as a residual in the energy balance. The FACE treatment increased daytime Ts about 0.6 degrees and 1.1 degrees C at high and low N, respectively. Daily total Rn was reduced by 1.3% at both levels of N. Daily ET was consistently lower in the FACE plots, by about 6.7% and 19.5% for high and low N, respectively.
A range of pulverized coals were combusted in a laboratory drop-tube furnace at temperatures of 1573, 1723, and 1873 K under oxidizing and reducing conditions to determine the effect of combustion ...stoichiometry on ash formation mechanisms. As iron mineral transformations were expected to be most affected by combustion stoichiometry, two of the test coals chosen were of high pyrite (FeS2) content and two of high siderite (FeCO3) content. It was found that the ash formation mechanisms of excluded quartz, koalinite, and calcite were not affected by oxidizing or reducing combustion conditions. Excluded pyrite was found to decompose to pyrrhotite, which oxidized to produce an FeO−FeS melt phase which was stable under reducing conditions. Under oxidizing conditions oxidation continued, producing magnetite and hematite. Excluded siderite was found to decompose to wustite, which was stable under reducing conditions, but oxidized to produce magnetite under oxidizing conditions. Included pyrite and siderite were determined to behave as for excluded pyrite and siderite if there was no contact with alumino-silicates. Included pyrite that contacted alumino-silicate minerals was observed to form two-phase FeS/Fe-glass ash particles, with incorporation of iron into the glass proceeding as the FeS phase was oxidized. Included siderite that contacted alumino-silicate minerals was determined to directly form iron alumino-silicate glass ash particles. Iron alumino-silicate glass ash was determined to form with iron in the Fe2+ state, much of which subsequently transformed to the Fe3+ state in oxidizing conditions, but remained primarily as in the Fe2+ state under reducing conditions.
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