The mycorrhizal status of Phragmites australis in several polluted soils and sediments of an industrialised region of Northern Portugal

Roots of Phragmites australis from three polluted soils and sediments (a periodically flooded stream bank containing organic pollutants, a high-pH drying sedimentation pond and an acidic, periodically flooded sand polluted by industrial effluents) were sampled over a 1-year cycle of plant growth to assess the degree of colonisation by arbuscular mycorrhizal fungi (AMF). At the dry sedimentation pond, root samples of Juncus effusus and Salix atrocinerea were also taken to assess the presence of AMF throughout the year. Root colonisation was low (<5% root length colonised) but arbuscule presence peaked in P. australis during the spring and autumn prior to flowering. These changes in arbuscule abundance were also seen in a parallel greenhouse trial using seed taken from one of the sites. Roots of J. effusus contained mainly vesicular colonisation but arbuscule activity peaked during the winter months (December–March). S. atrocinerea roots were found to be ectomycorrhizal throughout the year but the fine feeder roots were colonised by AMF. The results confirm that semi-aquatics, like P. australis, can become arbuscular mycorrhizal but that this status changes during the year depending on soil moisture content and plant phenology. The influence of AMF in these polluted soils is uncertain but the potential exists to establish a more diverse plant ecosystem during the landscaping of these areas (phytostabilisation) by management of adapted plant and AMF ecotypes. Accepted: 6 November 2000     

Bacterial corrosion of mild steel under the condition of simultaneous formation of ferrous and sulphide ions

Summary Corrosion of mild steel in cultures of a Pseudomonas species under the condition of simultaneous formation of Fe(II) and S^2- was initially inhibited by inhibiting the anodic reaction, but after long incubation the corrosion process was allowed to continue. When only S^2- was produced, the initial corrosion rate increased for up to 60 h but later declined, probably due to a protective FeS film formed on the metal. Cathodic reactions were affected in a similar fashion as the anode.Extensive pitting corrosion was observed when the mild steel coupons were immersed in bacterial culture producing Fe(IIO) and S^2-, but not in the uninoculated control.     

Influence of zinc,lead, and cadmium pollutants on the microflora of hawthorn leaves

Transect studies were conducted to determine the relative effects of zinc, lead, and cadmium pollution on microorganisms occurring on hawthorn leaves at varying distances from a smelting complex.Sporobolomyces roseus was absent from the most heavily contaminated leaves but, although lead was inhibitory, other environmental factors were also important in determining its overall population level. Conversely,Aureobasidium pullulans and nonpigmented yeasts showed a significant partial positive correlation with lead but were inhibited by zinc and/or cadmium. Numbers of bacterial colonies were only slightly reduced by the combined effect of all three metals, but total numbers of bacteria were highly negatively correlated with lead. Filamentous fungi, isolated by leaf washing, were only slightly inhibited by all three metals, and the degree of mycelial proliferation on senescent leaves was little affected by heavy metal pollution. Computer-generated maps were produced of the distribution ofA. pullulans in relation to zinc and lead fallout.     

Fungicide Enhancement of Nitrogen Fixation and Colonization of Phaseolus vulgaris by Rhizobium phaseoli

The number and weight of pods and the weight and nitrogen content of the tops of beans (Phaseolus vulgaris) derived from seeds inoculated with a thiram-resistant strain of Rhizobium phaseoli were increased if the seeds were treated with thiram before sowing in soil. A greater percentage of the nodules on 21-day-old plants were derived from the resistant strain, more nodules were formed, and these nodules were more effective in the presence of the fungicide than in its absence. These differences in nodule numbers were no longer present in 56-day-old plants, and only a small percentage of the nodules contained the resistant strain. The abundance of the fungicide-tolerant R. phaseoli increased rapidly soon after planting the seed and subsequently fell markedly, but the rate of decline was less if the seeds had been treated with the chemical. Protozoa also proliferated if thiram had not been applied to the seed, but their numbers were deleteriously influenced by thiram. Bdellovibrio, bacteriophages, and lytic micro-organisms acting on R. phaseoli were rare under these conditions. Ciliates and flagellated protozoa were initially suppressed by planting thiram-coated bean seeds in nonsterile soil, but the former were inhibited longer than the latter and the ciliate numbers never fully recovered if the seeds were treated with the fungicide. The resistant strain grew well in sterile soil also inoculated with a protozoa-free mixture of soil microorganisms whether thiram was added or not, but after an initial rise in numbers, its abundance fell if the mixture contained protozoa; the rate of this fall was delayed by the fungicide. The numbers of R. phaseoli were consistently less in sterile soil inoculated with the rhizobium plus a mixture of soil microorganisms containing ciliates and other protozoa than if the inoculum contained other protozoa but no ciliates. These results suggest that a suppression of protozoa, and possibly especially the ciliates, accounts for the enhanced growth of beans and the greater initial frequency of nodules formed by the thiram-resistant R. phaseoli in the presence of this fungicide. Thiram applied to uninoculated seed enhanced bean growth if thiram-resistant R. phaseoli were present in soil.     

Relationships of differential gene expression in leaves with heterosis and heterozygosity in a rice diallel cross

Using differential display analysis, we assessed the patterns of differential gene expression in hybrids relative to their parents in a diallel cross involving 8 elite rice lines. The analysis revealed several patterns of differential expression including: (1) bands present in one parent and F₁ but absent in the other parent, (2) bands observed in both parents but not in the F₁, (3) bands occurring in only one parent but not in the F₁ or the other parent, and, (4) bands detected only in the F₁ but in neither of the parents. Relationships between differential gene expression and heterosis and marker heterozygosity were evaluated using data for RFLPs, SSRs and a number of agronomic characters. The analysis showed that there was very little correlation between patterns of differential expression and the F₁ means for all six agronomic traits. Differentially expressed fragments that occurred only in one parent but not in the other parent or in F₁ in each of the respective crosses were positively correlated with heterosis and heterozygosity. And conversely, fragments that were detected in F₁s but in neither of the respective parents were negatively correlated with heterosis and heterozygosity. The remaining patterns of differential expression were not correlated with heterosis or heterozygosity. The relationships between the patterns of differential expression and heterosis observed in this study were not consistent with expectations based on dominance or overdominance hypotheses.     

Effects of an electric pulse on variation of bacterial community and metabolite production in kimchi-making culture

Three, six, nine, and twelve V of electric pulse (EP) was applied to a culture of Weissella cibaria SKkimchi1 in MRS medium and kimchi-making culture (KMC). Viable cell number of SKkimchi1 in MRS medium was decreased in proportion to pulse intensity but that of bacteria in KMC was not. Lactic acid and ethanol produced by SKkimchi1 tended to be decreased in proportion to EP intensity but acetic acid was proportionally increased to EP intensity. Lactic acid, ethanol, and propionic acid produced in KMC were proportionally decreased, but acetic acid was proportionally increased to the EP intensity. Bacterial community and diversity in KMC were analyzed based on culture time by a temperature gradient gel electrophoresis (TGGE) technique. Most bacterial communities grown in freshly prepared kimchi belonged to Bacillus genus. Lactic acid bacteria responsible for kimchi fermentation began to grow on day 4, and were completely substituted for Bacillus genus on day 8, but some Bacillus genus began to grow again on day 12. However, bacterial community diversities were not different based on varying EP intensity.     

Accuracy of the disk method for determining antimicrobic susceptibility of common Gram-negative bacilli

A standardized disk susceptibility test was evaluated by comparing results with minimal inhibitory concentrations obtained with agar dilution methods. The agar overlay method was used to test 152 Gram-negative bacilli against eight different antimicrobial agents. One to 3% of the isolates were resistant to an antimicrobic by the MIC method, but appeared to be susceptible by the disk method. Most very major discrepancies involved disk tests withProteus sp., a microorganism notoriously difficult to test reproducibly.Serratia sp. vs. the polymyxins andKlebsiella sp. vs. nitrofurantoin accounted for most other major discrepancies. With other microorganism-drug combinations, the disk test was a reasonably accurate technique for classifying bacteria into resistant or susceptible categories. Gentamicin disk tests were unsatisfactory, but when an intermediate zone category of 13–16 mm was applied, the false susceptible test results were reduced to 2.6%. Intermediate zone sizes were obtained with 6% of the disk tests; most of those isolates were resistant or susceptible but not intermediate in susceptibility. About 11% of the strains had intermediate MICs (5–20% with different drugs), but most of those strains were fully susceptible by the disk technique. *** DIRECT SUPPORT *** A01R4011 00007     

Two New Species of Isospora from the Desert Skink (Chalchides ocellatus) from the Egyptian Desert

Isospora chalchidis n. sp. and Isospora eimanae n. sp. were isolated from the desert skink, Chalchides ocellatus , order Squamata, from Egypt. Sporulated oocysts of I. chalchidis n. sp. were spheroidal 19 × 19 (18–20.5 × 18–20.5) μm with a 2–layered walled. Oocysts lacked a micropyle and residuum and few polar granules were present. Sporocysts were lemon-shaped 12.2 × 6.5 (9.5–13 × 5–8) μm with a Stieda body and sporocyst residuum but without a substiedal body. Isospora eimanae n. sp. were spheroidal 18.5 × 18.5 (17–19.5 × 17–19.5) μm with a 2–layered wall. There were oocysts without residuum or polar granule, but with small micropyle at 1 end. Sporocysts were ovoid 12 × 8.5(11–13 × 7.5–9) μm with a small Stieda body and sporocyst residuum but without a substiedal body.     

The effect of three herbicides on the number of spores of Rhynchosporium secalis on barley stubble and volunteer plants

Single sprays of paraquat, glyphosate or dinoseb-in-oil, were applied to barley stubble or volunteer plants and their effects on the number of spores of Rhynchosporium secalis were studied weekly. Spore concentrations were measured by washing samples of stubble or volunteer plants and counting spores using a haemocytometer. The number of spores recovered from stubbles was relatively small; both paraquat and glyphosate caused some reductions but the results were not consistent. Treatment with paraquat generally caused a transitory increase on volunteer plants; this effect was not found after glyphosate. Both herbicides caused persisting reductions from 4 wk after treatment. Volunteer plants treated with dinoseb-in-oil had fewer spores for 6 wk after treatment, but the plants were not killed and when new growth became infected, spore production recovered to equal that on untreated plants. The fungicide captafol caused some reductions in spore number on stubble but results were not consistent, applied after paraquat it had no effect. It was generally ineffective when applied to volunteer plants; applied after paraquat it tended to increase spore number, but the differences were seldom significant. Spores washed from volunteer plants treated with paraquat or glyphosate were inoculated to pot-grown barley seedlings; neither herbicide had any effect on spore viability. Viable spores were recovered in February from stubble or volunteer plants treated the previous autumn with paraquat or glyphosate respectively.     

Comparison of the effects of buthioninesulfoximine and phorone on the metabolism of sulfur-containing amino acids in rat liver

Alterations in hepatic transsulfuration reactions were determined in rats treated with a glutathione-depleting agent. A dose of l-buthionine-(S, R)-sulfoximine decreased hepatic methionine, cysteine, S-adenosylmethionine, and glutathione levels rapidly. Methionine adenosyltransferase and γ-glutamylcysteine lygase activities were decreased transiently, but significantly. The activity of cysteine dioxygenase was increased, resulting in an elevation of hypotaurine and taurine concentrations. Administration of phorone reduced hepatic glutathione and cysteine similarly, but S-adenosylmethionine concentrations were elevated for as long as 72 h. Hepatic methionine adenosyltransferase, cystathionine β-synthase, cystathionine γ-lyase, and γ-glutamylcysteine lygase activities were all increased but cysteine dioxygenase activity and taurine generation were markedly depressed. The results show that a decrease in hepatic GSH induces profound changes in sulfur amino acid metabolomics, which would subsequently influence various cellular processes. It is suggested that the change in hepatic levels of sulfur-containing substances and its physiological significance should be considered when a glutathione-depleting agent is utilized in biological experiments.     

Food selection in adults and larvae of three species of Lepidoptera: a behavioural and electrophysiological study

Adults and larvae of Spodoptera littoralis, Heliothis virescens and Heliothis armigera were tested with a range of sugars, amino acids, sugar alcohols and allelochemics. Feeding behaviour was correlated with the electrophysiological responses of maxillary styloconic sensilla in the larvae and proboscis styloconic sensilla in the adult. The neural response was more vigorous in larvae than in adults but otherwise the spectra of responses were similar in the two life stages. Phagostimulants and antifeedants stimulated maximally different sensilla in larvae but not in adults. The responses of adult sensilla to sugars and amino acids were significantly correlated to behaviour in all three species, but only in H. armigera was there a similar correlation with the sugar alcohols and allelochemics.     

Effects of three rates of aldicarb and of different degrees of resistance and tolerance in potato cultivars on yield and post-harvest population densities of the potato cyst nematodes Globodera rostochiensis and G. pallida

Three field experiments were made to determine the effectiveness of small-plot trials in detecting differences between potato cultivars/clones in their tolerance of damage by potato cyst-nematodes. A nematicide (aldicarb) was applied at three rates to decrease nematode damage. The largest rate of aldicarb increased tuber yields most but the relationship between yield response and nematicide rate was not linear. The yield increases of the cultivars and clones differed, indicating that they have different degrees of tolerance of potato cyst nematodes. The results were analysed in several ways and the untreated yield as a proportion of the treated provided the best means of expressing and comparing tolerance; but whichever method was used the tolerance rankings of the cultivars and clones were similar. At two sites infested with Globodera rostochiensis, the rankings of the 10 cultivars and clones were similar but at a third site, heavily infested with G. pallida, they were different. Aldicarb decreased the nematode population density after harvest at the G. pallida site but was less effective at the G. rostochiensis sites, which were less heavily infested. Growing resistant or partially resistant potatoes usually prevented nematode increase, and the more resistant cultivars and clones decreased population densities markedly.     

The effect of pH on the transformation of syringic and vanillic acids by the laccases of Rhizoctonia praticola and Trametes versicolor

Laccases (benzenediol: oxygen oxidoreductases, EC 1.10.3.2) from Rhizoctonia praticola and Trametes versicolor formed different products from syringic and vanillic acids at different pH values, but both enzymes generated the same chemicals at a particular pH. The products were separated by thin-layer and high-performance liquid chromatography. Four compounds were determined from syringic acid (m/z 168, 334, 350 and 486) at pH 6.9, but only two of these (m/z 168 and 334) were found at pH 3.5. In the case of vanillic acid two isomeric dimers (m/z 304) and 2-methoxy-1,4-benzoquinone (m/z 138) were identified. The dimers were formed at both pH values (pH 3.5 and 6.9), but 2-methoxy-1,4-benzoquinone appeared only at pH 3.5.     

Effects of Bacterial Prey Species and Their Concentration on Growth of the Amoebae Acanthamoeba castellanii and Hartmannella vermiformis

Two amoebae were presented with six bacterial prey at a range of concentrations, and the growth parameters of the amoebae were deduced. All but one bacterium (Synechococcus) resulted in a positive growth response, but the gram-positive bacterium Staphylococcus aureus proved to be difficult to digest and the heavily pigmented bacterium Klebsiella ozaenae induced unusual amoebic behavior prior to ingestion.     

Seedling and Sapling Dynamics of Treefall Pits in Puerto Rico1

Seedling and sapling dynamics in a Puerto Rican rain forest were compared between forest understory and soil pits created by the uprooting of 27 trees during Hurricane Hugo. Soil N and P, organic matter, and soil moisture were lower and bulk densities were higher in the disturbed mineral soils of the pits than in undisturbed forest soils ten months after the hurricane. No differences in N and P levels were found in pit or forest soils under two trees with N–fixing symbionts (Inga laurina and Ormosia krugii) compared to soils under a tree species without N–fixing sym–bionts (Casearia arborea), but other soil variables (Al, Fe, K) did vary by tree species. Forest plots had greater species richness of seedlings (<10 cm tall) and saplings (10–100 cm tall) than plots in the soil pits (and greater sapling densities), but seedling densities were similar between plot types. Species richness and seedling densities did not vary among plots associated with the three tree species, but some saplings were more abundant under trees of the same species. Pit size did not affect species richness or seedling and sapling densities. Recruitment of young Cecropia schreberiana trees (>5 m tall) 45 months after the hurricane was entirely from the soil pits, with no tree recruitment from forest plots. Larger soil pits had more tree recruitment than smaller pits. Defoliation of the forest by the hurricane created a large but temporary increase in light availability. Recruitment of C. schreberiana to the canopy occurred in gaps created by the treefall pits that had lower soil nutrients but provided a longer–term increase in light availability. Treefall pits also significantly altered the recruitment and mortality of many understory species in the Puerto Rican rain forest but did not alter species richness.     

Role of the epiphysis in organization of the infradian rhythmicity of physiological systems

In 330 control and epiphysectomized rats divided into groups (each included 15 rats), we compared the dynamics of the following indices: temperature and mass of the body, daily volume of urine, activities of succinate and α-glycerophosphate dehydrogenases in lymphocytes, activity of peroxidase in blood neutrophils, and motor activity in the open field test. In control rats, a set of infradian rhythms was manifested, and their periods were about 26; 18; 13.5; 9; 7; and 3.5 days. In epiphysectomized rats the same set of the periods was observed, but the spectral density of and phase relations between the rhythms were considerably modified. We conclude that the role of the epiphysis in organization of the infradian rhythmicity of physiological processes is significant, but it plays a rhythm-organizing, but not a pacemaker, role. Epiphysectomy results in considerable desynchronization of the studied processes.     

Effect of potato used as a trap crop on potato cyst nematodes and other soil pathogens and on the growth of a subsequent main potato crop

A field experiment in which main‐crop potatoes were grown every other year was conducted on a sandy soil from 1994 to 1999. The aim of the experiment was to control soil‐borne pathogens of potato with ecologically sound methods. Potato grown as a trap crop from the end of April to the end of June (8 wk) was used to control potato cyst nematodes (PCN) (Globodera pallida), and its effects on other important soil pathogens and on the growth of a subsequent potato crop were also assessed. Additional experimental treatments were a potato crop from which the haulm was removed and a green manure crop. Three potato cultivars with different degrees of resistance to PCN were grown as the main crop. Duplicate sets of the experiment were run concurrently. The PCN were effectively controlled by the potato trap crop. When a highly resistant potato cultivar was grown as a main crop after the trap crop, the post‐harvest soil infestation was very low. When a moderately resistant cultivar was grown after the trap crop the soil infestation also remained low. When the trap crop was alternated with a susceptible potato cultivar as a main crop, soil infestation increased slightly, but the degree of control when compared with no trap crop averaged 96%. Soil infestation with root‐knot nematodes (mainly Meloidogyne hapla) increased when potato was grown as a trap crop, but soil infestation with the root‐lesion nematode Pratylenchus crenatus was not affected. Stem canker caused by Rhizoctonia solani was not affected by the trap crop but black scurf (sclerotia of R. solani) on tubers was reduced. Soil infestation with Verticillium dahliae declined in one of the duplicate sets of the experiment but not in the other. However, stem infections by V. dahliae were significantly decreased in both sets, although the effect depended on the PCN‐resistance level of the potato cultivar. When a highly resistant potato cultivar was grown Verticillium stem infections were not significantly affected, they were decreased with a moderately resistant cultivar but the decrease was most pronounced with a PCN‐susceptible cultivar. Senescence of a following potato crop was not influenced by the trap crop when a highly PCN‐resistant cultivar was grown, but it was delayed in the case of a moderately resistant or a susceptible cultivar, resulting in higher tuber yields for those cultivars. The experiment proved that a trap crop can be an alternative to chemical soil disinfection but, for several reasons, the potato itself is not an ideal crop for this purpose; a trap crop other than potato must be developed.     

A comparison of the nodulation of diploid and tetraploid varieties of red clover inoculated with different Rhizobial strains

Summary The effectiveness of three different strains ofRhizobium trifolii on a diploid and a tetraploid variety of red clover (Trifolium pratense) grown in aseptic mineral-agar culture was compared. It was found that with two of the rhizobial strains tested, the tetraploid plants were slower to nodulate than the diploid plants, but that a hundred per cent nodulation was obtained in both cases. With the third strain, however, a sixty-six per cent nodulation of the diploid plants was reduced to an eight per cent nodulation of the tetraploids.In general, over a given period, fewer nodules were formed on the tetraploid plants, but these tended to be larger than on the diploids. The fresh weight of the tetraploid plants always exceeded that of the diploids, but less so in cases of poorly nodulated plants.     

The microflora of ripening barley grain and the effects of pre harvest fungicide application

Newly-emerged ears of barley soon became colonised by micro-organisms with numbers increasing to 5·8 × 10⁵ viable propagules/g dry weight by harvest. Bacteria were numerically predominant throughout. Yeasts and yeast-like fungi were also numerous during the early stages of grain development but were exceeded by propagules of filamentous fungi during ripening, with Cladosporium spp., Alternaria alternata, Epicoccum purpurascens and Verticillium lecanii most abundant. Numbers of most micro-organisms were greatest in a wet season but Alternaria was equally abundant in hot dry weather. Application of fungicides at or after anthesis modified the grain microflora. Captafol was most effective overall in decreasing numbers of fungi. However, benomyl decreased Cladosporium inoculum more than catpafol but was ineffective against Alternaria which became more numerous on benomyl-treated grain than on untreated. Yield increases of up to 4% were obtained by late fungicide treatment, least in a hot, dry year. Germination was also increased by some treatments by up to 5%.     

Factors controlling the time of onset of the migration of neural crest cells in the fowl embryo

Summary Transmission electron microscopy of fowl embryos during the 7–10 h preceding migration of trunk-level neural crest (NC) cells revealed extracellular material near the NC-cells. In contrast to the cells of the neural tube, the basal surfaces of NC-cells possessed projections, and were neither contiguous nor covered by a complete basal lamina. The apical zones of NC-cells showed intercellular junctions at the stage of neural-fold fusion, but such junctions were absent in some NC-cells 5 h before migration. The basal laminae of the neural tube and the ectoderm were fused lateral to the NC before migration. In vitro, NC-cell migration commenced immediately when neural anlagen were explanted onto fibronectin-rich matrices, but only when the neural anlagen were from a level where migration had commenced in vivo. Migration was delayed 4–8 h when premigratory-level expiants were used. Short-term cell-adhesion assays showed that NC-cells of both premigratory and migratory levels could adhere to fibronectin-rich matrices and to collagen gels, but only migratory NC-cells could be detached from the neural anlage. The results suggest that the precise schedule of the onset of NC-cell migration correlates with a decrease in the intercellular adhesion of NC-cells.