Soil temperatures and inoculation techniques affect emergence and reisolation of Sclerotinia sclerotiorum from soybean

Emergence of Amsoy soybean (Glycine max) seed inoculated withSclerotinia sclerotiorum was significantly reduced below noninoculated seed at soil temperatures of 25°, 30°, and 35 °C, but not at 20 °C.S. sclerotiorum was readily reisolated from wound-inoculated stems of seedlings and nearly mature plants above the point of inoculation and below to the crown area, but not from roots. The fungus was recovered from stems but not roots of 15-day seedlings grown in sterile soil before infestation of the soil surface with a suspension of mycelium and sclerotia and assayed at 15 days after soil infestation. When compared to healthy, seeds, infected seeds withS. sclerotiorum were characterized by appearing flattened.Supported in part by the Illinois Agricultural Experiment Station; Regional Project S-72; and U.S. Agency for International Development, grant csd-1922.     

Mepiquat chloride seed treatment and germination temperature effects on cotton growth, nutrient partitioning, and water use efficiency

Cotton seed (Gossypium hirsutum L. cv. Stoneville 825), treated with 0, 0.2, 1.0, and 2.0 g active ingredient (a.i.) mepiquat chloride (MC) kg^–1, was evaluated for the effect of MC on early plant growth. Emergence rate and total emergence of MC-treated seed and control were similar regardless of germination temperature. However, the number of leaves and squares and the dry weight of leaves, stems, and roots for hydroponically grown cotton plants were significantly lower at lower germination temperatures (15°C for 3 day/30°C for 1 day and 15°C for 4 days) than at higher germination temperatures (30°C for 4 days and 30°C for 3 days/15°C for 1 day). All MC treatments significantly decreased the number of nodes, leaves, and squares, as well as dry weight of leaves, stems, and roots, as compared to control plants at 28 days after emergence. MC seed treatments also significantly reduced plant height and total leaf area compared to controls. Water-use efficiency (WUE) was significantly lower for the 1.0 g a.i. MC treatment than for control plants. In general, the highest rate of MC seed treatment resulted in greater concentrations of calcium, phosphorus, and nitrogen in plant leaves and stems and also in greater concentrations of magnesium, phosphorus, and nitrogen in roots than in controls.     

Thidiazuron-Induced High-Frequency Shoot Regeneration from Root Region of Robinia pseudoacacia L. Seedlings

High-frequency regeneration of shoots was achieved at root region of seedlings of Robinia pseudoacacia L. cultured from seeds on medium supplemented with thidiazuron (TDZ, 1.0 M). The roots of intact seedlings proliferated and formed a compact callus followed by differentiation of numerous shoots. Corresponding cultures on benzylaminopurine-containing medium exhibited much weaker response. Hypocotyl segments also formed shoots at a lower concentration of TDZ (0.1 M). The shoots formed on TDZ-containing medium were well-developed and readily rooted on hormone-free medium. The obtained plants after acclimation in culture room survived after transfer to soil.     

Ferulic acid may prevent infection of Cicer arietinum by Sclerotium rolfsii

High performance liquid chromatography analysis of different parts of Sclerotium rolfsii-infected and healthy seedlings of chickpea (Cicer arietinum) was carried out to examine the status of phenolic compounds. Three major peaks that appeared consistently were identified as gallic, vanillic and ferulic acids. Gallic acid concentrations were increased in the leaves and stems of infected plants compared to healthy ones. Vanillic acid detected in stems and leaves of healthy seedlings was not detected in infected seedlings. There was a significant increase of ferulic acid in those stem portions located above the infected collar region compared to minimal amounts in the roots of healthy seedlings. In vitro studies of ferulic acid showed significant antifungal activity against S. rolfsii. Complete inhibition of mycelial growth was observed with 1000 g of ferulic acid/ml. Lower concentrations (250, 500 and 750 g/ml) were also inhibitory and colony growth was compact in comparison with the fluffy growth of normal mycelium. Higher amounts of phenolics were found in the stems and leaves of S. rolfsii-infected seedlings in comparison to the healthy ones. A role for ferulic acid in preventing infections by S. rolfsii in the stems and leaves of chickpea plants above the infection zone is therefore feasible.     

Effect of<Emphasis Type="Italic"> p</Emphasis>CO<Subscript>2</Subscript> and temperature on the boron isotopic composition of the zooxanthellate coral<Emphasis Type="Italic"> Acropora</Emphasis> sp.

Culture experiments were carried out with Acropora sp. (a branching scleractinian coral) in seawater at two pCO₂ conditions (438 and 725 µatm) and two temperatures (25 and 28 °C) in order to establish the pH and temperature dependence of the boron isotopic composition of the skeleton. A clear pCO₂ effect, but no temperature effect, on the coral boron isotope composition is seen. For corals cultured at normal pCO₂ (438 µatm), the ¹¹B of the skeleton was 24.0±0.2 at 25 °C, and 23.9±0.3 at 28 °C. The values of ¹¹B measured for corals cultured at higher pCO₂ (725 µatm) were lower: 22.5±0.1, and 22.8±0.1 at 25 and 28 °C, respectively. The ¹¹B of corals cultivated at both high and normal pCO₂ conditions are consistent with a dominant pH control, and are very close to that calculated from theoretical considerations. Thus, the corals do not seem to significantly alter ambient seawater for calcification with respect to pH. Co-variation between boron and carbon isotope values is explored.Communicated by: Guest Editor A. Grottoli     

Glutathione synthesis in maize genotypes with different sensitivities to chilling

The effect of chilling on enzymes, substrates and products of sulfate reduction, gultathione synthesis and metabolism was studied in shoots and roots of maize (Zea mays L.) genotypes with different chilling sensitivity. At full expansion of the second leaf, chilling at 12 °C inhibited dry weight increase in shoots and roots compared to controls at 25 °C and induced an increase in adenosine 5-phosphosulfate sulfotransferase and -glutamylcysteine synthetase (EC 6.3.2.2) activity in the second leaf of all genotypes tested. Glutathione synthetase (EC 6.3.2.3) activity was about one order of magnitude higher than -glutamylcysteine synthetase activity, but remained unchanged during chilling except for one genotype. During chilling, cysteine and glutathione content of second leaves increased to significantly higher levels in the two most chilling-tolerant genotypes. Comparing the most tolerant and most sensitive genotype showed that chilling induced a greater incorporation of³⁵S from [³⁵S]sulfate into cysteine and glutathione in the chilling-tolerant than in the sensitive genotype. Chilling decreased the amount of³⁵S-label incorporated into proteins in shoots of both genotypes, but had no effect on this incorporation in the roots. Glutathione reductase (EC 1.6.4.2) and nitrate reductase (EC 1.6.6.1) activity were constitutively higher in the chilling-tolerant genotypes, but showed no changes in most examined genotypes during 3 d at 12 °C. Our results indicate that in maize glutathione is involved in protection against chilling damage.Abbreviations APSSTase adenosine 5-phosphosulfate sulfotransferase - EC -glutamylcysteine - GR glutathione reductase - OSH glutathione - NR nitrate reductase We thank M. Suter for preparing [³⁵S]adenosine 5-phosphosulfate, Dr. A. Fleming (both our Institute) for correcting the English and M. Soldati (Eschlikon, Switzerland) for his help with the plant material. This work was supported by COST 814 Crop development for the wet and cool regions of Europe.     

The initiation of somatic embryos and adventitious roots from developing zygotic embryo explants of Cercis canadensis L. cultured in vitro

Zygotic embryo explants of Cercis canadensis L. cultured in vitro responded to 1 and 5 M 2,4-dichlorophenoxyacetic acid (2,4-D) or 50 M -naphthaleneacetic acid (NAA) by initiating somatic embryos and adventitious roots. Somatic embryos and adventitous roots were formed from developing zygotic embryos, while fully developed embryos collected from mature seed initiated only adventitious roots. Following 2,4-D application, the number of somatic embryos decreased while adventitious roots increased with increasing developmental age of the explant. The greatest number of somatic embryos were initiated with a 5 to 20 day exposure to 5 M 2,4-D from zygotic embryos collected between 75 and 82 days post-anthesis in 1987. Somatic embryos formed directly from epidermal and subepidermal cells, while adventitious roots developed from interior cortex cells. Normal somatic embryos were recovered after a 20 day exposure to 5 M 2,4-D and acclimated to greenhouse conditions.     

Relations between grapevine replant disease and root colonization of grapevine (Vitis sp.) by fluorescent pseudomonads and endomycorrhizal fungi

In pot experiments cuttings of grapevine rootstock cultivar 5C were grown on a soil from a grapevine nursery affected with replant disease (replant soil) and on a similar soil that had not been planted with grapevines before (non-replant soil). Plants were also inoculated with the vesicular-arbuscular (VA) mycorrhizal fungus,Glomus mosseae, or left without mycorrhizal fungus inoculation. Shoot and root growth, mycorrhization of roots and numbers of total aerobic bacteria and fluorescent pseudomonads on the rhizoplane of grapevines were determined at several sampling dates. On replant soil, numbers of fluorescent pseudomonads on the rhizoplane were higher compared to non-replant soil, before differences in shoot and root weight between replant and non-replant soil occurred. Without inoculation withG. mosseae, the mycorrhization of roots was much lower on replant soil (13%) than on non-replant soil (51%). On replant soil, inoculation withG. mosseae increased mycorrhization to 39% and increased shoot length, leaf area and shoot weight. The beneficial effect of VA-fungus inoculation on replant soil was not due to increased nutrient concentrations in leaves. On replant soil, the inoculation withG. mosseae reduced the number of fluorescent pseudomonads on rhizoplane of grapevine, while the numbers of total aerobic bacteria were not influenced by inoculation withG. mosseae. These results suggest a direct or indirect role of fluorescent pseudomonads in replant disease of grapevine.     

Replicon properties of chromosomal DNA fibers and the duration of DNA synthesis of sunflower root-tip meristem cells at different temperatures

Chromosomal DNA fiber autoradiography was used to examine the replicon properties of root-tip meristem cells of Helianthus annuus intact seedlings grown at temperatures from 10 to 38° C and those of root-tip cells grown in vitro at 23°. The average replicon size was approximately 22 m and it did not change with temperature nor when the roots were grown in culture. The average fork rate was 6 m/h at 10° and it rose gradually to 12 m/h at 38°. The responses of replication fork movement and of the duration of S to temperature were of three types: those in which change in fork rate was primarily (more than 90%) responsible for change in the duration of S, those in which the fork rate remained constant while S increased nearly twofold, and those in which the duration of S increased even though the replication forks were moving faster. The first type of response listed was observed at temperatures from 20 to 35°, the second type listed was observed at 10 to 15°, and the third, was produced at 38°.     

Erratum: Cloning and sequencing of the phycocyanin gene from Spirulina maxima and its evolutionary analysis

The genes were cloned for the two apoprotein subunits, and ,of phycocyanin from the cyanobacterium Spirulina maxima = Arthrospiramaxima) strain F3. The - and -subunit gene-coding regionscontain 489 bp and 519 bp, respectively. The -subunit gene is upstreamfrom the -subunit gene, with a 111-bp segment separating them.Similarities between the -subunits of S. maxima and nine othercyanobacteria were between 58% and 99%, as were those between the -subunits. The maximum similarity between the - and -subunits from S. maxima was 27%.     

Effect of temperature regime on growth and subsequent responses ofSophora japonica seedlings to SO2

Summary Ten-week-oldSophora japonica seedlings were grown for 10 weeks at 17, 22, or 27°C and then exposed to 0 or 1.0 /SO₂ for 48 hours. The seedlings were subsequently grown at 22°C and harvested 12 weeks later. Effects of preconditioning temperature and SO₂ on leaf formation, seedling height and stem diameter, as well as dry weight increment and relative growth rates of leaves, stems, and roots were studied. The preconditioning temperature regime influenced growth and subsequently affected SO₂ uptake and growth. However, the responses of seedlings to temperature and SO₂ varied with the growth parameter measured. The need for greater standardization of methods and criteria for assessing pollution tolerance of plants is emphasized.Research supported by the College of Agricultural and Life Sciences, University of Wisconsin Madison, Wisconsin, USA. McIntyre-Stennis Project 2599.     

Orientation of the porphyrin ring in artificial chlorophyll membranes

Summary A sensitive photometric method is described by which the dichroism of lipid bilayer membranes in aqueous phase can be measured. The method is applied to black films with incorporated chlorophylla andb. With chlorophylla a relatively large dichroism is found in the Soret band and a much weaker dichroism in the red band. From the experimental data, the angles _B and _R between the blue and red transition moments and the membrane can be obtained. _B and _R are then used to calculate the angle of the porphyrin ring with respect to the membrane surface. For chlorophylla and three different lipids, values of between 44 and 49° are found.     

Structure and nonlinear optical properties of copper phthalocyanine thin films

This paper describes a joint study of the structure and nonlinear optical properties of vacuum evaporated thin films of copper phthalocyanine (CuPc for brevity). Film thickness ranges from 50 to 500 nm. The anisotropic paramagnetic resonance of Cu⁺⁺ ions reveals that the Pc rings lie almost parallel to the substrate plane with however a large angular distribution (30° FWHM). Third harmonic optical generation measurements performed at 1.064 m and 1.907 m fundamental wavelengths give respectively an average value of the cubic susceptibility ⁽³⁾(-3,)=(4±0.4)·10^–12 e.s.u. and (2.1+-0.2) · 10^-12 These values, although significantly higher than for a common ionic crystal, are about one order of magnitude lower than in conjugated 1-D systems, which shows that the 2-D -electron delocalization is less profitable than the 1-D one. Besides third harmonic, we have also observed second harmonic generation. Its polarization dependence is characteristic of a quadratic susceptibility enhanced in one direction, almost perpendicular to the substrate, withd _eff comprised between 30 and 60 · 10^-9 e.s.u. The possible origins ofd _eff are discussed.     

Energy requirements for growth and maintenance of Scenedesmus protuberans Fritsch in light-limited continuous cultures

Scenedesmus protuberans Fritsch was grown in light-limited continuous cultures with a light-dark cycle, at temperatures of 20° and 28° C. At 20° irradiances of 12 and 38 W m^–2 were used, at 28° 38 W m^–2.The relationships between growth rate and light uptake rate were of diphasic linear character. With the lower growth rates the relationships were defined with the parameters _e , i.e. the specific maintenance rate constant, and c, the true efficiency of light energy conversion into biomass. The _e -value was dependent on temperature, the c on irradiance.In cultures, incubated in prolonged darkness, decrease rates of biomass were comparable to the derived _e -values.Both diphasic linear relationships between growth rate and light uptake rate and the same order of magnitude of _e -values could be derived from literature data on other green algae.     

The removal response ofApis mellifera L. colonies to brood in wax and plastic cells after artificial and natural infestation withVarroa jacobsoni Oud. and to freeze-killed brood

LikeApis cerana colonies,A. mellifera colonies also show removal response toVarroa-infested brood cells. Infested worker brood cells of artificially and naturally infested combs were detected by the worker bees to various degrees in all types of comb-material used.The bees uncap brood cells and remove larvae or pupae infested with one or two mites. The removal response of worker bees was stronger towards brood cells containing two mites than cells with one mite.The specific signals which cause the removal of brood cells infested withVarroa mites are unknown. Removal response toVarroa-infested brood cells in plastic comb-material (Jenter-and ANP-comb) was significantly higher than to brood in wax combs. Up to now we do not know to what extent this tolerance mechanism is influenced by genetic and environmental factors.Our experiments comparing the removal of freeze-killed brood with the removal of brood infested withVarroa mites demonstrate positive correlations. Considering the time-consuming method of the artificial infestation with living mites, the hygienic behaviour-including the removal of brood cells infested with mites-of large series of colonies can be tested using freeze-killed brood.     

Active site directed inhibitors and mechanism of action of glycosidases

Summary A review is given on the inactivation of glycosidases by active site directed inhibitors, their use to identify functional groups at the active site, and deductions with respect to the mechanism of catalysis. The following enzymes are discussed:-glucosidases from various sources,-glucosidase from S. cerevisiae,-galactosidases from E. coli and Helix pomatia, cellulase and lysozyme. Epoxide type inhibitors appear especially suitable because their reactivity is enhanced selectively by acidic groups at the active site.In those cases where definite conclusions regarding the mechanism can be drawn, catalysis seems to occur by a carboxylate ion as base and an acid that has been identified as a carboxyl group with-glucosidase from Asp. wentii. The hydrolysis probably proceeds via a glycosyl-enzyme intermediate, which may be a stabilized carbonium ion or a covalent intermediate.an invited article     

The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre

Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.     

Relation between trace element levels in plasma and myocardium during coxsackievirus B3 myocarditis in the mouse

During most infections the plasma levels of trace elements change, but it is not clear if this reflects changes in the infected tissues. Coxsackievirus B3 (CB3) infection may result in viral replication, subsequent inflammation and changed trace element levels in the myocardium. In the present study, the trace element levels in the plasma and heart of adult male A/J mice were determined during the pre-inflammatory stage (day 4) of CB3 myocarditis for the following trace elements: aluminium (Al), arsenic (As), calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), selenium (Se), silver (Ag), vanadium (V) and zinc (Zn). The severity of the infection was assessed through clinical signs of disease and trace element levels were measured through inductively-coupled plasma mass-spectrometry (ICP-MS). In the heart, the levels decreased for V (59%; p<0.01), Co (38%; p<0.01), Al (81%; p< 0.01), As (66%; p<0.01) and Se (16%; p<0.01). Increased levels were detected for Mn (13%; p<0.05), Fe (48%; p<0.01), Cu (34%; p<0.01) and Ag (46%; p< 0.01). In the plasma, decreases were detected in the level of Zn (32%; p<0.05), whereas increases were seen in Mn (362%; p<0.05), Fe (272%; p<0.01), Co (71%; p<0.05), Cu (25%; n.s.) and Mg (43%; p<0.01) levels. A correlation was found between the levels in plasma and myocardium for Co (r _s=–0.636; p<0.05), Fe (r _s=0.764; p<0.05), Mn (r _s=0.682; p<0.05) and Mg (r _s=–0.791; p<0.05). Thus, determination of some of these trace elements in the plasma may be useful to indicate target tissue involvement in the early pre- inflammatory stage of an infectious disease. Some of these elements are important nutrients for the immune system, while others may be associated with the development of disease complications, such as cardiac arrhythmias.     

Fine structure of the flagellar apparatus of gametesin situ and motile zygotes of the green algaUlothrix flacca var.Roscoffensis (Ulotrichales) (Chlorophyta)

Summary This fine structural study ofUlothrix flacca (Dillw.) ThuretRoscoffensis variety (Berger-Perrot), a marineUlothrix, describes in detail the flagellar apparatus configuration of gametesin situ in the gametangia and in motile zygotes. The gametes's flagellar apparatus shows two basal bodies overlapping at their proximal end at a 30° angle, in an 11/5 o'clock configuration or with a counterclockwise absolute orientation. The basal bodies are interconnected by a non-striated band or capping plate. They are wrapped in their proximal part by an electron-dense sheath and obtured by a bilobed terminal cap. A cruciate microtubular root system having a 4-2-4-2 alternation pattern is present. A striated microtubule associated component (S.M.A.C.) or system I fibres accompany the two membered root R₂. The system II fibres or rhizoplasts along with striated bands associated to the microtubular roots, were not observed and are presumed to be absent.In the motile zygotes, the basal bodies are paired in a cruciate pattern. During the fusion process, two basal bodies, one of each pair, slide in a face to face position with a slight displacement into the 11/5 o'clock direction; the other two make a 30° counterclockwise rotation, thus making a 60° angle between the two basal bodies of each pair instead of 30° in the gamete.After comparison with the flagellar apparatus of other green alga gametes, it is concluded that the taxonomic affinities ofUlothrix flacca var.Roscoffensis, lie with theUlvophyceae sensuStewart andMattox 1978.Abbreviations CP capping plate - ER endoplasmic reticulum - G Golgi body - LG lipid globule - M mitochondria - MS presumed mating structure - N nucleus - R ₂,R ₄ microtubular roots - SH sheath - SMAC striated microtubule associated component - TC terminal cap - V vacuole - Ve vesicles in the anterior papilla - 1, 2, 1, 2 basal bodies numerotation     

Effects of salinity on metabolism and life history characteristics of Daphnia magna

In the Baltic Sea area, the cladoceran Daphnia magna is commonly found in brackish water rockpools and it has been suggested that salinity is one of the niche dimensions that affects the distribution of the species. The salinity tolerance of D. magna was studied both in physiological and life history experiments. The experimental salinities were freshwater, 4S and 8S. The highest respiration and ammonium excretion rates were measured in the freshwater treatment with decreasing respiration and ammonium excretion rates at higher salinities. The lowest O/N ratio (oxygen consumption to ammonium excretion), describing the metabolic status of an organism, was obtained at 8S, although the only significant differences were detected when comparing to 4S treatments. Individual growth rate, reproductive output and population growth rate were highest at 4S. At 8S growth and reproduction were reduced as compared to freshwater and 4S. The life history parameters in the performed experiments indicated higher fitness (expressed as r) as well as more favourable conditions for growth and reproduction at 4S, whereas the O/N ratio was more difficult to interpret and, in this case, gave a less clear picture of the salinity influence.