Growing maize in clumps as a strategy for marginal climatic conditions

Under dryland conditions of the Texas High Plains, maize (Zea mays) production is limited by sparse and erratic precipitation that results in severe water stress particularly during grain formation. When plant populations are reduced to 2.0–3.0 plants m⁻² to conserve soil water for use during grain filling, tillers often form during the vegetative growth and negate the expected economic benefit. We hypothesized that growing maize in clumps spaced 1.0 m apart would reduce tiller formation, increase mutual shading among the plants, and conserve soil water for grain filling that would result in higher grain yield. Studies were conducted during 2006 and 2007 at Bushland, TX. with two planting geometries (clump vs. equidistant), two irrigation methods (low-energy precision applicator, LEPA, and low-elevation spray applicator, LESA) at three irrigation levels (dryland, 75 mm and 125 mm in 2006; and dryland, 50 mm and 100 mm in 2007). For dryland plots in 2007, clump plants had only 0.17 tillers (0.66 tillers m⁻²) compared with 1.56 tillers per plant (6.08 tillers m⁻²) for equidistant spacing. Tillers accounted for 10% of the stover for the equidistant plants, but less than 3% of the grain. Clump planting produced significantly greater grain yields (321 g m⁻² vs. 225 g m⁻² and 454 g m⁻² vs. 292 g m⁻² during 2006 and 2007, respectively) and Harvest Indexes (0.54 vs. 0.49 and 0.52 vs. 0.39 during 2006 and 2007, respectively) compared with equidistant plants in dryland conditions. Water use efficiency (WUE) measurements in 2007 indicated that clumps had a lower evapotranspiration (ET) threshold for initiating grain production, but the production function slopes were 2.5 kg m⁻³ for equidistant treatments compared to 2.0 kg m⁻³ for clump treatments. There was no yield difference for method of irrigation on water use efficiency. Our results suggest that growing maize in clumps compared with equidistant spacing reduced the number of tillers, early vegetative growth, and Leaf Area Index (LAI) so that more soil water was available during the grain filling stage. This may be a useful strategy for growing maize with low plant populations in dryland areas where severe water stress is common.     

The relationship between winter temperatures and the extent of potato leaf-roll virus in seed potatoes in Scotland

Summary With data on potato leaf-roll virus (PLRV) collected from the seed potato certification scheme comparisons were made with two measures of winter temperature, anomalies from the long term mean and air frost days for both single and groups of months early in the year when virus spread occurred. Good correlations between crop rejection rates for PLRV and temperature anomalies were obtained both for the whole area covered by the scheme in Scotland and one smaller area; the Lothians and East Border counties. Only when the temperature anomaly for April is added as a third factor are correlations obtained for air frost days.

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Zusammenfassung Auf Grund der schottischen Pflanzkartoffel-Anerkennungsvorschriften wurden Angaben über einen Zeitraum von 12 Jahren (Tabelle 1a) betreffend Abweisung wegen Befalls mit Kartoffel-Blattrollvirus (PLRV) gesammelt. Diese Daten wurden im Hinblick auf zwei Temperaturwerte in den letzten Wintermonaten des Pflanzkartoffel-Erzeugungsjahres analysiert. Abweichungen vom langj?hrigen Durchschnitt der Temperaturen für die Monate Februar, M?rz und April zeigten gute Korrelationen, wenn entweder einzeln angewendet oder in Kombination (Tabelle 2) sowohl für die ganze Periode als auch für die ersten 8 Jahre, wenn man die Daten von ganz Schottland nimmt. Die Regressionsgerade und die Vertrauensgrenzen für 12 Jahre sind in Abb. 2 dargestellt. Das andere Mass für die Charakterisierung der K?lte, die Frosttage (Lufttemperaturen) konnte allein nicht mit den PLRV-Daten eng verbunden werden; nur wenn als dritter Faktor die Temperaturabweichung des Monats April dazugez?hlt wird, werden sinnvolle Korrelationen erreicht. Wenn die Angaben eines Gebietes, der Grafschaften Lothian und East Border, auf gleiche Weise behandelt wurden, erhielt man bei beiden ?hnliche Resultate in bezug auf Temperatur-abweichungen (Tabelle 4 und Abb. 3) und Frosttage (Lufttemperatur). Dies trotz der Schwierigkeiten, die infolge des Transportes von Pflanzgut in das Gebiet entstanden. Daraus ist zu schliessen, dass tiefe Temperaturen in den sp?ten Wintermonaten über die Kontrolle der Entwicklung der Blattlauspopulation das Ausmass des im folgenden Jahr festgestellten PLRV beeinflussen. Besonders die April-Temperatur scheint in Schottland einen betr?chtlichen Einfluss zu haben, was nach weiteren Ueberlegungen ruft.

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Résumé Les données de refus pour virose d'enroulement (PLRV) collationnées chez l'organisme écossais de certification de plants de Pomme de terre au cours d'une période de 12 années (tableau 1a) ont été analysèes en fonction de deux systèmes d'évaluation de la température dans les derniers mois de l'année au cours de laquelle se produit l'extension de la maladie. Lorsque les données de refus pour enroulement provenaient de l'Ecosse entière, les anomalies de température des mois de février, mars et avril, par rapport à la température moyenne basée sur une longue période d'observations, montrent de bonnes corrélations, qu'elles soient utilisées seules ou en combinaison (tableau 2), à la fois pour la période entière (12 ans) ou pour les 8 premières années. La figure 2 montre la ligne de régression et les limites de confiance pour la période de 12 ans. L'autre mesure du froid, c'est-à-dire le nombre de jours de gel dans l'air, ne peut être étroitement reliée aux observations de PLRV que lorsque l'écart de température d'avril est ajoutée comme troisième facteur; dans ce cas on observe des corrélations satisfaisantes. Lorsqu'on analyse d'une fa?on semblable les données d'état sanitaire d'une rétion, à savoir les comtés de Lothian et de ‘East Border’, on obtient des résultats comparables à la fois pour les anomalies de température (tableau 4 et figure 3) et pour les jours de gel dans l'air, et ceci en dépit du mouvement des stocks de plants dans la région. Il se dégage la conclusion qu'une température basse dans les derniers mois d'hiver influence l'importance des manifestations de PLRV l'année suivante en agissant sur le développement des populations d'aphides. La température d'avril en particulier se révèle avoir un effet considérable en Ecosse et justifie d'autres études.

     

Sum rules and interlayer conductivity of high-Tc cuprates

Analysis of the interlayer infrared conductivity of cuprate high-transition temperature superconductors reveals an anomalously large energy scale extending up to midinfrared frequencies that can be attributed to formation of the superconducting condensate. This unusual effect is observed in a va- riety of materials, including Tl2Ba2CuO6+x, La2-xSrxCuO4, and YBa2Cu3O6.6, which show an incoherent interlayer response in the normal state. Midinfrared range condensation was examined in the context of sum rules that can be formulated for the complex conductivity. One possible interpretation of these experiments is in terms of a kinetic energy change associated with the superconducting transition.     

Metabolic aspects of the toxicology of diazinon. I. Hepatic metabolism in the sheep,cow, pig,guinea-pig,rat, turkey,chicken and duck

The phosphorothionate insecticide diazinon was incubated with liver microsomes from the sheep, cow, pig, guinea-pig, rat, turkey, chicken and duck. Metabolism by liver slices of most of these species was also examined. Hydroxydiazinon, isohydroxydiazinon, dehydrodiazinon, their oxons and diazoxon were identified and determined quantitatively or semi-quantitatively. An eighth metabolite was tentatively identified as the 6-aldehyde analogue of diazinon. Yields and rates of production of these metabolites varied greatly between species. Production of oxons was not generally correlated with susceptibility to diazinon poisoning, although it was lowest in the least susceptible animal, the sheep. The degradation of oxons by liver slices was too slow to explain the low toxicity of diazinon to the mammals. The relative importance of hepatic and extrahepatic metabolism in determining toxicity to vertebrates is discussed.     

Enhancing the TurtleWatch product for leatherback sea turtles,a dynamic habitat model for ecosystem‐based management

Fishery management measures to reduce interactions between fisheries and endangered or threatened species have typically relied on static time‐area closures. While these efforts have reduced interactions, they can be costly and inefficient for managing highly migratory species such as sea turtles. The NOAA TurtleWatch product was created in 2006 as a tool to reduce the rates of interactions of loggerhead sea turtles with shallow‐set longline gear deployed by the Hawaii‐based pelagic longline fishery targeting swordfish. TurtleWatch provides information on loggerhead habitat and can be used by managers and industry to make dynamic management decisions to potentially reduce incidentally capturing turtles during fishing operations. TurtleWatch is expanded here to include information on endangered leatherback turtles to help reduce incidental capture rates in the central North Pacific. Fishery‐dependent data were combined with fishing effort, bycatch and satellite tracking data of leatherbacks to characterize sea surface temperature (SST) relationships that identify habitat or interaction ‘hotspots’. Analysis of SST identified two zones, centered at 17.2° and 22.9°C, occupied by leatherbacks on fishing grounds of the Hawaii‐based swordfish fishery. This new information was used to expand the TurtleWatch product to provide managers and industry near real‐time habitat information for both loggerheads and leatherbacks. The updated TurtleWatch product provides a tool for dynamic management of the Hawaii‐based shallow‐set fishery to aid in the bycatch reduction of both species. Updating the management strategy to dynamically adapt to shifts in multi‐species habitat use through time is a step towards an ecosystem‐based approach to fisheries management in pelagic ecosystems.     

PTF 11kx: a type Ia supernova with a symbiotic nova progenitor

There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.