Conserved molecular components for pollen tube reception and fungal invasion

During sexual reproduction in flowering plants such as Arabidopsis, a tip-growing pollen tube (PT) is guided to the synergid cells of the female gametophyte, where it bursts and releases the two sperm. Here we show that PT reception and powdery mildew (PM) infection, which involves communication between a tip-growing hypha and a plant epidermal cell, share molecular components. NORTIA (NTA), a member of the MLO family originally discovered in the context of PM resistance, and FERONIA (FER), a receptor-like kinase, both control PT reception in synergids. Homozygous fer mutants also display PM resistance, revealing a new function for FER and suggesting that conserved components, such as FER and distinct MLO proteins, are involved in both PT reception and PM infection.     

Moisture pulses,trace gas emissions and soil C and N in cheatgrass and native grass-dominated sagebrush-steppe in Wyoming,USA

Effects of large-scale weed invasion on the nature and magnitude of moisture-pulse-driven soil processes in semiarid ecosystems are not clearly understood. The objective of this study was to monitor carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions and changes in soil carbon (C) and nitrogen (N) following the application of a water pulse in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) communities dominated by the exotic annual grass cheatgrass (Bromus tectorum) and by the native perennial grass western wheatgrass (Pascopyrum smithii). Sampling locations were established in shrub interspaces dominated by B. tectorum and P. smithi and beneath shrub canopies adjacent to interspaces dominated by B. tectorum and P. smithi, where no grass was present. Soils were classified as fine-loamy, mixed, Borollic Haplargids. Soil samples (0–10 cm) and air samples were collected at 0, 4, 8, 24, 49, 72, and 216 h following additions of 25.4 mm of water. Soil samples were analyzed for dissolved organic carbon (DOC), microbial biomass carbon (MBC), extractable ammonia (NH₄⁺), extractable nitrate (NO₃^?), and dissolved organic nitrogen (DON). Grass species induced differences in soil nitrification, N₂O and CO₂ emissions, and the quantity and timing of labile C available to microbial populations responding to increased moisture availability. In the first 8-h phase after wetting P. smithii soils had the greatest CO₂ emissions compared to other soils but B. tectorum soils had the greatest N₂O emissions and the greatest increases in CO₂ emissions relative to before wetting. Microbial biomass C in B. tectorum interspace soils increased rapidly but the response was short-lived despite sufficient water availability. After the first 8 h of soil response to wetting, the observed MBC declines in B. tectorum interspace coincided with disproportional DOC and DON concentration increases. Similar DOC and DON increases were also observed in B. tectorum soils beneath shrub canopy. In contrast, DOC and DON concentrations in P. smithii soils remained unaffected by soil wetting and small MBC increases observed during the first 8-h phase did not decline as rapidly as in B. tectorum interspace soils. In conclusion, summer drying-wetting cycles that occur frequently in areas invaded by B. tectorum can accelerate rates of nitrification and C mineralization, and contribute significantly to trace gas emissions from sagebrush-steppe grasslands. With frequent summer rainfall events, the negative consequences B. tectorum presence in the ecosystem can be significant.     

Zur Ökologie und über methoden in der Stechmückenbekämpfung

Zusammenfassung Die in der Bundesrepublik Deutschland vorliegenden über 40jährigen Erfahrungen auf dem Gebiet der Stechmückenbekämpfung haben zu der Erkenntnis geführt, daß das Problem der Massenentfaltung dieser Insekten ökologisch begründet und langfristig auch nur mit Hilfe von ökologisch orientierten Maßnahmen und nicht mit den heute der modernen Schädlingsbekämpfung zur Verfügung stehenden Mitteln und Verfahren zu lösen ist.Da die Massenentwicklung von Stechmücken in engem Zusammenhang mit den Wasserstandsverhältnissen der verschiedenartigen Feuchtbiotope innerhalb einer Landschaft zu sehen ist, so lassen sich in der Stechmückenbekämpfung Mittel und Verfahren unterscheiden, die a) eine Schwächung des Ökosystems bewirken, wie Adultizide, Larvizide, Ovizide, Wachstumsregulatoren, wasseroberflächenaktive Substanzen (Öle, Tenside, Lezithine u.a.), die b) in das Ökosystem nicht oder weniger stark schwächend eingreifen, wie Repellents, mechanische Abwehrmittel (Gazefenster), biologische Verfahren (Krankheitserreger, wie Viren, Bakterien, Rickettsien und Pilze, sowie räuberische Arthropoden), genetische Verfahren, die aber bisher noch kaum Praxisreife erlangt haben und physikalische Verfahren, wie abwehrende Schallwellen und elektrische Insektenvernichtungsgeräte, deren Wirksamkeit auf Stechmücken zweifelhaft ist, und die c) in das Ökosystem im Sinne der Landschaftshygiene verändernd, aber landschaftsschonend eingreifen, wie wasserregulatorische und landschaftsgestaltende Maßnahmen, die nicht im Widerspruch zu den Grundprinzipien der Natur stehen. Über die Funktion, die Dipterenlarven im Stoffhaushalt der Natur haben, wird berichtet.

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Ecology and methods of mosquito control

More than 40 years of experience in the field of mosquito control in the Federal Republic of Germany have resulted in the recognition of the fact that the problem of mass development of these insects has ecological reasons and that it can be resolved in the long run only with the aid of measures oriented towards ecology instead of the agents and methods presently available to pest control operators.Since a mass development of mosquitoes has to be seen in a close association with the water level of the different types of wet habitats within a given area, a differentiation is made in pest control among means and methods which a) result in a weakening of the ecosystem such as adulticides, larvicides, ovicides, growth regulators, and surface-active substances (oils, surfactants, lecithins etc.), b) those which have not or less pronounced weakening influence such as repellents, mechanical defences (wiregauze windows), biological methods (agents of disease, like viruses, bacteria, rickettsiae, and fungi as well as predatory arthropods), genetic methods which so far have not yet reached the stage of practical application in most cases and physical methods such as repelling sound waves and electrical insect destroyers of doubtful effectiveness in respect of mosquitoes and c) those which effect the ecosystem in a hygienic sense by bringing about changes which, however, do not cause any harm to the area like measures of water regulation and landscape formation which do not oppose the basic principles of nature. The function of the larvae of Diptera within the metabolisms of nature is outlined.

     

Die Tulpe als Sekundärwirtspflanze für die „Schwarzen Blattläuse” (Aphis-fabae-Gruppe im engeren und weiteren Sinn[Homoptera: Aphid idae])

Zusammenfassung Wie Testversuche mit Arten und Rassen aus derAphis-fabae-Gruppe im engeren und weiteren Sinn zeigten, handelt es sich bei den im Freiland aufTulipa spec. vorkommenden Schwarzen Blattläusen um die polyphagen SubheterözierAphis fabae, A acanthi undA. evonymi sowie um einige Rassen derAphis-fabae-Gruppesensu stricto. Unter geeigneten klimatischen Bedingungen kann es auf allen Teilen der Tulpe zur Massenentwicklung dieser Blattläuse kommen. Für monözische Blattlausarten (A. hederae, A. podagrariae undA. ilicis) und monophage Subheterözier (A. cognatella undA. tripolii), die aufTulipa spec. starke(A. ilicis) oder zumindest schwache Kolonien entwickeln, muß diese Wirtspflanze zu den künstlichen oder tertiären gezählt werden, da die Tulpe von diesen Blattlausarten unter natürlichen Bedingungen — vermutlich aus biologischen Gründen — nicht beflogen wird.

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Summary As has been shown by tests involving species and sub-species of the Aphis fabae group in a proper and a broad sense, the Black Aphids present onTulipa spec. in the field are the polyphageous and subheteroeciousAphis fabae, A. acanthi, andA. evonymi as well as some sub-species of theAphis fabae group in a proper sense. Under suitable climatic conditions, a mass development of these aphids may take place on all parts of the tulip. For monoecious species of aphids (A. hederae, A. podagrariae andA. ilicis) and monophageous subheteroecious ones (A. cognatella andA. tripolii) which develop large(A. ilicis) or at least minor colonies onTulipa spec., this host must be listed among artificial or tertiary hosts, since under natural conditions — probably for biological reasons — these aphids species will not fly to the tulip.

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Der Deutschen Forschungsgemeinschaft sei für die finanzielle Unterstützung dieser Arbeit gedankt. Für die sorgfältige Durchführung der Testversuche, die in den Frühjahren 1965 und 1966 im Institut für gärtnerische Virusforschung der Biologischen Bundesanstalt, Berlin-Dahlem erfolgten, bin ich meinen Assistentinnen Frau GERDA GLIECH und Frl. ADELHEID VON SYDOW zu Dank verpflichtet.     

The role of humic substances in the mobilization of mercury from watersheds

The total Hg concentration was estimated in eight inflowing streams from two headwater lakes and catchments in Ontario over a 2-yr period. Marked seasonal patterns in all brown water streams were evident, with highest levels usually occurring in the early fall and early spring. The seasonal pattern and the estimated export of Hg was most closely related to color, a measure of humic matter in the water. The data suggest that humic matter controls the solubility and watershed export of Hg deposited in precipitation.     

Impact of Iron Source and Concentration on Rice Flavor Using a Simulated Rice Kernel Micronutrient Delivery System

An extruded grain designed to look like a rice kernel fortified with one of two sources of iron (elemental iron and ferrous sulfate), with and without multiple fortificant (zinc, thiamin, and folic acid), was mixed with milled Calrose rice at low (1:200), medium (1:100), and high (1:50) concentrations. The intensities of water‐like, sour taste, hay‐like musty, and alfalfa/grassy/green bean flavors were enhanced by the addition of ferrous sulfate (FeSO₄) or FeSO₄ plus multiple fortificants. Astringent mouthfeel was likewise affected by addition of FeSO₄ or FeSO₄ plus multiple fortificants. Overall, the elemental iron with multiple fortificants least affected the oxidation of the extruded kernals. Lipid oxidation products in stored fortificant increased the first two to three months and concentrations were higher in samples with FeSO₄ as the iron source.     

Expression patterns of a circadian clock gene are associated with age-related polyethism in harvester ants, Pogonomyrmex occidentalis

Background  

Recent advances in sociogenomics allow for comparative analyses of molecular mechanisms regulating the development of social behavior. In eusocial insects, one key aspect of their sociality, the division of labor, has received the most attention. Age-related polyethism, a derived form of division of labor in ants and bees where colony tasks are allocated among distinct behavioral phenotypes, has traditionally been assumed to be a product of convergent evolution. Previous work has shown that the circadian clock is associated with the development of behavior and division of labor in honeybee societies. We cloned the ortholog of the clock gene, period, from a harvester ant (Pogonomyrmex occidentalis) and examined circadian rhythms and daily activity patterns in a species that represents an evolutionary origin of eusociality independent of the honeybee.