Nitrogen and phosphorus nutritional interactions in a CO2 enriched environment

Nonnodulated soybean plants (Glycine max. [L.] Merr. ‘Lee') were supplied with nutrient solutions containing growth limiting concentrations of N or P to examine effects on N‐ and P‐uptake efficiencies (mg nutrient accumulated/gdw root) and utilization efficiencies in dry matter production (gdw²/mg nutrient). Nutritional treatments were imposed in aerial environments containing either 350 or 700 μL/L atmospheric CO₂ to determine whether the nutrient interactions were modified when growth rates were altered.

Nutrient‐stress treatments decreased growth and N‐ and P‐uptake and utilization efficiencies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT). Atmospheric CO₂ enrichment increased growth and N‐ and P‐utilization efficiencies at 27 DAT and seed yield in all nutritional treatments and did not affect N‐ and P‐uptake efficiencies at 27 DAT. Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO₂ enrichment and vice versa. Nutrient‐stress treatments lowered the relative seed yield response to atmospheric CO₂ enrichment.

Decreased total‐N uptake by P‐stressed plants was associated with both decreased root growth and N‐uptake efficiency of the roots. Nitrogen‐utilization efficiency was also decreased by P‐stress. This response was associated with decreased plant growth as total‐N uptake and plant growth were decreased to the same extent by P stress resulting in unaltered tissue N concentrations. In contrast, decreased total P‐uptake by N‐stressed plants was associated with a restriction in root growth as P‐uptake efficiency of the roots was unaltered. This response was coupled with an increased root‐to‐shoot dry weight ratio; thus shoot and whole‐plant growth were decreased to a much greater extent than total‐P uptake which resulted in elevated P concentrations in the tissue. Therefore, P‐utilization efficiency was markedly reduced by N stress.     

Assessment of PCDD/Fs and PCBs in Sediments from the Spanish Northern Atlantic Coast

Fluid catalytic cracking of heavy ends to high-value liquid fuels is a common unit operation in oil refineries. In this process, the heavy feedstock that contains sulfur is cracked to light products. Sulphur content is hence redistributed in the liquid and gaseous products and coke of the catalyst used in this process. The coke is later burnt in the regenerator releasing sulfur into the discharged flue gas as SO₂. In the present work, comprehensive emission inventories for a fluid catalytic cracking unit in a typical oil refinery are prepared. These inventories are based on calculations that assume complete combustion of catalyst coke in the regenerator. Yearly, material balances for both SO₂ and particulate matters emissions are carried out taking into account seasonal variations in the operation of the process unit. The results presented in this article reflect the variation of sulfur in feedstock originating from various units in the refinery. The refinery operations are not dependant on seasons but controlled by market-driven conditions to maximize the profit. The seasonal impact on refinery emissions is minimal due to its operation at optimum capacity fulfilling the international market demand. The data presented and analyzed here can be used to assess the hazardous impact of SO₂ and particulate matter emissions on surrounding areas of the refinery.     

Antibiotic Resistance, Gene Transfer, and Water Quality Patterns Observed in Waterways near CAFO Farms and Wastewater Treatment Facilities

We examined water quality indicators (pH, temperature, turbidity, total phosphorus, and fecal coliform density) and bacterial antibiotic resistance (prevalence, conjugative transfer, and genetic linkage of resistance elements) at locations impacted by confined animal feeding operations (CAFOs) and compared them to nearby reference sites. Sites located upstream and downstream of two wastewater treatment facilities were also compared. Sites near CAFO farms had poor water quality (elevated total phosphorus and turbidity), while water quality remained relatively good downstream of wastewater treatment plants. High proportions of antibiotic-resistant bacteria were observed at all study sites, and frequent conjugative transfer of resistance was observed in laboratory assays. Out of a total of 830 environmental bacterial isolates, 77.1% were resistant to only ampicillin, while 21.2% were resistant to combinations of antibiotics including ampicillin (A), kanamycin (K), chlorotetracycline (C), oxytetracycline (O), and streptomycin (S). Multi-drug-resistant bacteria were significantly more common at sites impacted by CAFO farms. In conjugation assays, 83.3% of the environmental isolates transferred one or more antibiotic resistance genes to a laboratory strain of Salmonella typhimurium. A subset of multi-drug-resistant (A, C, and O) isolates was screened for specific tetracycline resistance genes and class I and II integrons. None of the screened isolates (n?=?22) were positive for integrons, while 13 isolates contained resistance genes for tet (B) and tet (C). Our results indicate that CAFO farms not only impair traditional measures of water quality but may also increase the prevalence of multi-drug-resistant bacteria in natural waters.     

Has yield stability changed with genetic improvement of wheat yield?

The effect of plant breeding on yield and their physiological determinants has been widely studied in wheat. However, it is poorly understood how, and to what extent, yield stability has been modified. To attempt a direct analysis of changes in absolute and relative yield stability, data of yield of cultivars released in different eras in different environments were obtained from records from our lab and from the literature. Depending on the availability of data, effects of plant breeding on yield stability of cultivars released in Argentina, Australia, Italy and the United Kingdom were evaluated using a quantitative approach. In this paper it was assumed that the slope of yield vs. environmental index estimates the instability of the cultivars. In addition, a more qualitative approach for Mexico, and the former USSR complemented this analysis. There was a clear decrease in yield stability assessed in absolute terms as a consequence of wheat breeding. In Argentina, Australia, Italy and the UK this decrease was related to the magnitude of yield increases. However, the decrease in yield stability in Argentina and Australia was less than for Italy and the UK, particularly so during the last 30 years. Modern cultivars released in Argentina and Australia showed a trend to maintain yield stability as a percentage of their yield similar to that of their predecessors, while the two European countries analysed tended to a slight decrease in yield stability even in relative terms. The complementary, less quantitative evaluation of Mexico and the former USSR appeared to confirm the quantitative trends described for the other countries, i.e. a general decrease in yield stability (assessed in absolute terms) with genetic gains in yield potential. This revised version was published online in July 2006 with corrections to the Cover Date.     

The selective sequestration of glucosinolates by the cabbage aphid severely impacts a predatory lacewing

The cabbage aphid Brevicoryne brassicae is a notorious agricultural pest that specializes on plants of the Brassicaceae family, which are chemically defended by glucosinolates. By sequestering glucosinolates from its host plants and producing its own activating enzyme (myrosinase), this aphid employs a self-defense system against enemies paralleling that in plants. However, we know little about the metabolic fate of individual glucosinolates during aphid sequestration and activation and about the biochemical effects of this defense on aphid enemies. Here, we probed these questions focusing on B. brassicae and a predatory lacewing, Chrysoperla carnea. We found that distinct glucosinolates were accumulated by B. brassicae at different rates, with aliphatic glucosinolates being taken up more quickly than indolic ones. B. brassicae myrosinase enzymatic activities toward different glucosinolates were strongly correlated to their rates of accumulation in vivo. Surprisingly, after simulated predation, the production of toxic isothiocyanate products (ITCs) was quantitatively outweighed by less toxic products such as nitriles and ITC-conjugates. Nevertheless, the defensive cocktails significantly impaired C. carnea development. Tissue-specific quantification of glucosinolate metabolites revealed that the lacewings employ both conjugation and mobilization to reduce the toxicity of aliphatic ITCs, but these strategies were only partially effective. These results clarify the metabolic fates of glucosinolates after sequestration by an aphid herbivore and further in a higher trophic level, as well as the consequences for predator survival and development, and might be instructive for integrative pest management approaches targeting the cabbage aphid.

     

Implications of landscape configuration on understory forage productivity: a remote sensing assessment of native forests openings

Agroforestry Systems - Sound management of native forests used for cattle grazing requires understanding the dynamics of forage productivity in the openings. Despite their importance, forage...     

Mill variation in bending strength and stiffness of in-grade southern pine No. 2 2 × 4 lumber

Visually graded southern pine (SP) has wide variability within grade. For 2 × 4 lumber, this variability has increased because it is harvested from both natural forests and plantation forests where trees contain high percentages of juvenile wood. To investigate resource variability, six kiln-dried No. 2 2 × 4 SP packages were acquired from six mills. From each package, 124 samples were destructively tested in bending. Mean modulus of elasticity (MOE₁₅) ranged from 9.2 to 13.1 GPa, and three mills did not meet the design values (11.0 GPa). Bending strength (F _b) ranged from 7.6 to 11.9 MPa, and four mills did not meet the design values (10.3 MPa). Analysis of variance of MOE₁₅ and F _b showed significant differences between mills. MOE₁₅ explained from 33 to 51 % of the variability in F _b. These data suggest that variation between mills is high and destructive testing is critical for more accurate characterization of lumber properties.     

Thinning increases cone production of stone pine (Pinus pinea L.) stands in the Northern Plateau (Spain)

Context

Edible stone pine (Pinus pinea L.) nut is a forest product which provides the highest incomes to the owners of stone pine forests.

Aim

The objective of this work is to evaluate the effect of first thinning on growth and cone production in an artificially regenerated stand in order to determine optimum intensity.

Methods

A thinning trial was installed in 2004 to compare two thinning regimes (heavy and moderate) and a control treatment. From 2004 to 2012, six inventories of forest attributes were carried out, and the cone crop was harvested annually. We evaluated the effect of thinnings on growth using repeated measures analysis of variance with a mixed model approach. With regards to cone production, we first estimated the probability of finding cones in a tree by applying a generalized mixed model and then estimated cone production by using a mixed model, including climatic variables.

Results

We found that thinning had a positive influence on tree diameter increment. Thinning increased the probability of finding cones and cone production. However, significant differences between heavy and moderate thinnings were not found.

Conclusion

We recommend early silvicultural treatments in stone pine stands to favor the development of trees and larger edible pine nut production.