Cyclic Variations in Nitrogen Uptake Rate of Soybean Plants: Effects of External Nitrate Concentration

Net uptake of by non-nodulated soybean plants [Glycine max (L.) Merr.cv. Ransom] growing in flowing hydroponiccultures containing 0–5, 1.0 and 10-0 mol m^–3 was measured daily during a 24-d period of vegetativedevelopment to determine if amplitude of maximum and minimumrates of net uptake are responsive to external concentrations of . Removal of from the replenished solutions during each 24-h period was determinedby ion chromatography. Neither dry matter accumulation nor theperiodicity of oscillations in net uptakerate was altered bythe external concentrations. The maxima of the oscillations in net uptake rate, however, increased nearly3-fold in response to external concentrations. The maxima and minima, respectively, changed from 4.0 and 0–6mmol per gram root dry weight per day at an external solution level of 05 mol m^–3 to 15–2and -2–7 mmol per gram root dry weight per day at an external solution level of 10–0mol m^–3 . The negative values for minimum net uptake rate from10–0 mol m^–3 solutions show that net efflux was occurring andindicate thatthe magnitude of the efflux component of net uptake was responsiveto external concentration of . Key words: Nitrate uptake rate, carbon-nitrogen partitioning, flowing solution culture     

Response properties of the prothoracic AN2 auditory interneurone to model calling songs in the cricket Gryllus bimaculatus

Sound processing properties for calling song (CS) models, as described for the prothoracic L3 auditory neurone in Acheta domesticus, are investigated for the homologous auditory neurone 2 (AN2) in female Gryllus bimaculatus De Geer. AN2 of G. bimaculatus responds selectively to the syllable period (SP) of models of a male CS. The selectiveness of this response parallels the selectivity of phonotaxis females perform in response to the same SPs. Both, the responses of AN2 and female behaviour show clear interindividual variability. The SP‐selective responses of AN2 result from an SP‐dependent reduction in the spiking to subsequent syllables of the model CSs, measured as the percentage decrement. This SP‐dependent response does not primarily result from inbuilt properties of the AN2 membrane. Rather, it is dependent on inhibitory input to the AN2. However, clear inhibitory postsynaptic potentials in dendritic recordings of the AN2 are not encountered. This immediate response of AN2 to CSs is followed by an increased rate of tonic firing between stimulus CSs, which is termed the prolonged response, and is dependent on the carrier frequencies that make up the male CSs. With stimulation on the contralateral side of the soma of AN2s, more than 50% of AN2s exhibit a prolonged response. However, with stimulation from the ipsilateral side of the soma, most AN2s exhibit a prolonged response. The prolonged response of AN2 at 5 kHz may be even more sensitive than the immediate response. Thus, the AN2 neurone could provide a basis for phonotaxis that is selective for both the SPs and the carrier frequencies of potentially attractive calling songs.     

Origins, structure, and trophic significance of amorphous seston in a blackwater river

1. The role of suspended organic aggregates in aquatic systems has received much attention, but their origin and function vary between environments and conditions. 2. In the Ogeechee River (Georgia, U.S.A.) particles are constructed of clay, organic debris, and microorganisms in a matrix of mucopolysaccharide fibrils. Although these fibrils are probably of bacterial origin, microcosm studies suggest that synthesis of particles from dissolved substances can occur in the absence of microbial processing. 3. Processing of organic material and production of amorphous aggregates occurs through a series of microbial events and follows a well-defined successional cycle that results in a high concentration of protists in sestonic particles. 4. Chemical analyses show that the relatively high protein and fat content of this amorphous material is a valuable food resource for filter-feeding macroinvertebrates that are dense in this system.     

Processing of model calling songs by the prothoracic AN2 neurone and phonotaxis are significantly correlated in individual female Gryllus bimaculatus

Syllable period (SP) selective calling song processing has been demonstrated for the prothoracic, AN2 auditory neurone that correlates very well with SP‐selective phonotaxis by female cricket Gryllus bimaculatus De Geer. Both SP‐selective processing by the AN2 and the phonotactic behaviour of the female exhibit substantial plasticity. Thus, the question remains as to whether the selective responses of the AN2 neurone and the selective behaviour of the female match in an individual female. The present study is designed to answer that question. The SP‐selective phonotactic behaviour of individual females is evaluated, followed immediately by measuring the SP‐selective responses of the same female's AN2 neurone. Very significant correlations are found between the selective responses of the AN2 neurone and the same female's selective behaviour. In 208 possible comparisons (26 females, eight behavioural and neuronal tests each), 186 resulted in matches between behaviour and neuronal processing. Dividing the SP‐selective females into two groups (one group that responded phonotactically to the shortest SP tested and a second group that did not respond to this SP) resulted in significantly more selective responses to this shortest SP by the AN2 neurone in the females that responded phonotactically to the SP than for the females who did not respond to the shortest SP. The behavioural responses by these two groups to the other SPs tested are shown to be essentially identical.     

The methane cycle in ferruginous Lake Matano

In Lake Matano, Indonesia, the world’s largest known ferruginous basin, more than 50% of authigenic organic matter is degraded through methanogenesis, despite high abundances of Fe (hydr)oxides in the lake sediments. Biogenic CH₄ accumulates to high concentrations (up to 1.4 mmol L^?1) in the anoxic bottom waters, which contain a total of 7.4 × 10⁵ tons of CH₄. Profiles of dissolved inorganic carbon (ΣCO₂) and carbon isotopes (δ¹³C) show that CH₄ is oxidized in the vicinity of the persistent pycnocline and that some of this CH₄ is likely oxidized anaerobically. The dearth of NO₃^? and SO₄^2? in Lake Matano waters suggests that anaerobic methane oxidation may be coupled to the reduction of Fe (and/or Mn) (hydr)oxides. Thermodynamic considerations reveal that CH₄ oxidation coupled to Fe(III) or Mn(III/IV) reduction would yield sufficient free energy to support microbial growth at the substrate levels present in Lake Matano. Flux calculations imply that Fe and Mn must be recycled several times directly within the water column to balance the upward flux of CH₄. 16S gene cloning identified methanogens in the anoxic water column, and these methanogens belong to groups capable of both acetoclastic and hydrogenotrophic methanogenesis. We find that methane is important in C cycling, even in this very Fe‐rich environment. Such Fe‐rich environments are rare on Earth today, but they are analogous to conditions in the ferruginous oceans thought to prevail during much of the Archean Eon. By analogy, methanogens and methanotrophs could have formed an important part of the Archean Ocean ecosystem.     

'PUBLISH OR PERISH': THE PITFALLS OF DUPLICATE PUBLICATION

Abstract:  Duplication of previously published text or figures in the scientific literature without adequate citation is plagiarism or, in the case of an author's own work, self-plagiarism. It breaches the ethical standards that are expected in science and threatens the integrity of scientific journals. Three examples of duplication are noted, one of which involves Palaeontology . Redundant publication lowers the quality of scientific literature, damages the good standing of journals, and reduces the intellectual impact of a study. Multiple papers on a particular theme are only acceptable if each builds significantly upon previous work and contains only as much background information as necessary to put the new data and observations into perspective.     

GLOBE students, teachers, and scientists demonstrate variable differences between urban and rural leaf phenology

The urban heat island effect, classically associated with high impervious surface area (ISA), low vegetation fractional cover (Fr), and high land surface temperature (LST), has been linked to changing patterns of vegetation phenology, especially spring growth. In this study, a collaboration with the Global Learning and Observations to Benefit the Environment (GLOBE) program, we investigated the effect of the urban environment on the timing of leaf budburst of native deciduous trees in seven cities: Asia (Tokyo, Japan; Bangkok and Korat, Thailand), Europe (Jyväskylä, Finland; Bishkek, Kyrgyzstan), Africa (Dakar, Senegal), and North America (Fairbanks, Alaska). The cities differed not only in population size but also in climate and vegetation type. Using Landsat satellite imagery from each city, we calculated LST, Fr, and ISA, and classified sites within each study area as rural or urban. The timing of leaf flushing, measured by students using GLOBE budburst protocols, was statistically different within all cities, with absolute differences ranging from 1 to 23 days. We assessed the classic urban phenology paradigm, which proposes higher LST, lower Fr, and earlier budburst in urban areas of temperate cities. Of the four temperate cities, Tokyo followed the classic paradigm, but no other city demonstrated consistent support. Urban budburst was advanced in three of the four temperate cities, but in only one of the three tropical cities. Results suggest that while vegetation phenology is consistently different between urban and rural areas, a uniform paradigm based on the explanatory variables in this study did not emerge. Although not testable here, it is likely that alterations to chilling requirements in temperate climates and humidity in tropical climates may also influence observed budburst differences.     

Scale-Dependent Effects of Landscape Structure and Composition on Diurnal Roost Selection by Forest Bats

Abstract: Forest management affects the quality and availability of roost sites for forest-dwelling bats, but information on roost selection beyond the scale of individual forest stands is limited. We evaluated effects of topography (elevation, slope, and proximity of roads and streams), forest habitat class, and landscape patch configuration on selection of summer diurnal roosts by 6 species of forest-dwelling bats in a diverse forested landscape of the Ouachita Mountains, Arkansas, USA. Our objectives were to identify landscape attributes that potentially affect roost placement, determine whether commonalities exist among species in their response to landscape attributes, and evaluate the effects of scale. We modeled roost selection at 2 spatial scales (250- and 1,000-m radius around each roost). For each species, parameters included in models differed between the 2 scales, and there were no shared parameters for 2 species. Average coefficients of determination (R²) for small-scale models were generally higher than for large-scale models. Abundance of certain forest habitat classes were included more often than patch configuration or topography in differentiating roost from random locations, regardless of scale, and most species were more likely to roost in areas containing abundant thinned forest. Among topographic metrics, big brown bats (Eptesicus fuscus) were more likely to roost at higher elevations; roosts of big brown bats, northern long-eared bats (Myotis septentrionalis), and Seminole bats (Lasiurus seminolus) were influenced by slope; and big brown bats, evening bats (Nycticeius humeralis), and Seminole bats were more likely to roost closer to water than random. Northern long-eared bats and red bats (Lasiurus borealis) were more likely to roost closer to roads, whereas eastern pipistrelles (Perimyotis subflavus) were more likely to roost further from roads than random. Common parameters in most models included 1) positive associations with group selection (5 of 6 species) and thinned mature forest (4 species) at the small scale; 2) negative associations with unmanaged mixed pine-hardwood forest 50–99 years old at the large scale (4 species); 3) negative association with stands of immature pine 15–29 years old at the small scale (3 species); and 4) a positive association with largest patch index at the large scale (3 species). Our results suggest that, in a completely forested landscape, a variety of stand types, seral stages, and management conditions, varying in size and topographic location throughout the landscape, would likely provide the landscape components for roosting required to maintain a diverse community of forest bats in the Ouachita Mountains.