The manganese toxicity of cotton

Cotton plants (Gossypium hirsutum. Linn. var. Sankar 4) were grown at normal and toxic levels of substrate manganese, and the altered metabolism of manganese toxic plants was studied. The tissues of plants exposed to toxic levels of manganese had higher activities of peroxidase and polyphenol oxidase, and the activities of catalase, ascorbic acid oxidase, glutathione oxidase and cytochrome c oxidase were lowered. In addition, the high manganese tissue had lower contents of ATP and glutathione but higher amounts of ascorbic acid. The respiration of the partially expanded leaves and the growing tips of toxic plants were depressed when compared to that of the normal tissues. The metabolic changes of manganese toxicity of cotton are placed in the following order: accumulation of manganese in the leaf tissue; a rise in respiration; stimulation of polyphenol oxidase; the appearance of initial toxicity symptoms; the evolution of ethylene and stimulation of peroxidase; the presence of severe toxicity symptoms; the depression of terminal oxidases and respiration; abscission of the growing tip and proliferation of the stem tissue. The early stimulation of polyphenol oxidase may be used to detect potential manganese toxicity.     

The influence of substrate contact on gravity orientation

Summary Tilting of the animal with respect to gravity results in compensatory eyestalk movements and in leg counterforce reactions which vary with the number and sequential position of legs touching the body-fixed substrate board (Figs. 2, 3). The gravity response is reduced with increasing number of legs touching the substrate. The results fit an interpretation that the weight of the substrate input interacting with gravity signals results from superposition of the weighted effects of the single legs involved (Figs. 2, 4).Acknowledgements are due to the Max-Planck-Institut (D. M. Neil, N. Scapini) and to the Carnegie Trust (D. M. Neil) for financial support. We want to thank renate Alton for her co-operative help.     

Effects of substrate analogues and pH on manganese superoxide dismutases

The effect of the substrate analogues azide and fluoride on the manganese(II) zero-field interactions of different manganese-containing superoxide dismutases (SOD) was measured using high-field electron paramagnetic resonance spectroscopy. Two cambialistic types, proteins that are active with manganese or iron, were studied along with two that were only active with iron and another that was only active with manganese. It was found that azide was able to coordinate directly to the pentacoordinated Mn(II) site of only the MnSOD from Escherichia coli and the cambialistic SOD from Rhodobacter capsulatus. The formation of a hexacoordinate azide-bound center was characterized by a large reduction in the Mn(II) zero-field interaction. In contrast, all five SODs were affected by fluoride, but no evidence for hexacoordinate Mn(II) formation was detected. For both azide and fluoride, the extent of binding was no more than 50%, implying either that a second binding site was present or that binding was self-limiting. Only the Mn(II) zero-field interactions of the two SODs that had little or no activity with manganese were found to be significantly affected by pH, the manganese-substituted iron superoxide dismutase from E. coli and the Gly155Thr mutant of the cambialistic SOD from Porphyromonas gingivalis. A model for anion binding and the observed pK involving tyrosine-34 is presented.     

The influence of manganese on the development of potato scab

Summary The development of common scab on potato crops growing in slightly acid to neutral soils has been shown to be greatly reduced by application of manganese sulphate to the soil at planting time. A general improvement in health and appearance of tubers was noted and increased yields of marketable tubers were obtained. The possibility that environmental factors known to influence the development of scab are only important in so far as they affect the solubility of soil manganese is discussed.     

The influence of high substrate concentrations on microbial kinetics

High substrate concentrations inhibit growth and may distort the metabolism of microorganisms. Mechanisms causing substrate inhibition are discussed and used to derive several mathematical models representative of the entire concentration range, including stimulation of growth by low substrate concentrations. These kinetic models are tested with a variety of batch culture measurements of specific growth rate and respiration rate at widely-ranging substrate concentrations. Using one of the kinetic models, equations are developed for batch, continuous, and exponential-feed reactors. Comparison of results obtained in continuous culture with results from exponential-feed culture systems is shown to offer a novel experimental method for evaluating the effect of the cell age distribution on the properties and metabolic activity of a culture.     

Effect of chemical amendments and foliar application on lentil wilt

Summary Mn and Zn salt amendments in soil, presoaking of seeds in Mn and Zn salt solutions, foliar application of Mn and Zn salt sprays has been tried in order to control the lentil wilt pathogen. Best disease control was obtained at 80 ppm of Mn and Zn salt amendments. Presoaking the seeds also considerably reduced the disease. Foliar sprays of Zn and Mn salts were also equally effective in controlling the disease. From the point of view of practical agriculture it can be suggested that presoaking the seeds of lentil with Zn and Mn salts at 80 ppm concentration can form a very good and effective     

The influence of calcium and magnesium on manganese transport and utilization in Mice

Biological Trace Element Research - The influence of high but not extreme concentrations of Ca and Mg in water (25 µmol/mL) and of similar concentrations in food (25 µmol/g) on the...     

The influence of morphological differences in bracken pinnules on the foliar uptake of aminotriazole

Bracken growing on an open hillside had greater development of both the upper and lower cuticular membranes than that growing under moderate shade. However, in the latter, aminotriazole uptake was less. This could be due to decreased spreading of the applied solution on the upper surface of shade-grown fronds and a decrease in stomatal and/or leaflet hair densities on the lower surface.     

Plant homeostasis of foliar manganese sinks: specific variation in hyperaccumulators

Plant manganese (Mn) hyperaccumulation provides unusual insight into homeostasis of this essential micronutrient, in particular its excessive storage in shoot tissues. The compartmentation of hyperaccumulated foliar Mn appears exceptional among metal hyperaccumulators, since it occurs via specific microdistribution patterns. Here, three associated Mn hyperaccumulators, Virotia neurophylla, Maytenus fournieri, and Garcinia amplexicaulis exhibiting distinctly different Mn detoxification strategies were examined. Non-invasive sample preparation in conjunction with cryo scanning electron microscopy (SEM) was used to obtain in vivo quantitative microprobe X-ray and anatomical data from fully hydrated cells. Highly vacuolated large palisade mesophyll cells in V. neurophylla leaves were found to contain around 650?mM Mn. The large non-photosynthetic hypodermal cells of M. fournieri leaves, also with high vacuolar content, and the main site for Mn disposal, had an estimated mean vacuolar Mn concentration of around 600?mM. Previous qualitative X-ray mapping had shown Mn to be almost evenly sequestered across the entire leaf cross section of G. amplexicaulis. However, quantitative data obtained here showed a marked variation in localised concentrations that ranged between?~15 and?>800?mM. Notable among these were mean values of?>600?mM in spongy mesophyll cells, and?~800?mM within cells of a narrow sub epidermal layer preceding the palisade mesophyll. This study demonstrated the extraordinary Mn carrying capacities of different types of leaf cell vacuoles.     

The use of microbial siderophores for foliar iron application studies

Experiments were conducted to assess the distribution of foliar applied Fe-containing compounds using microbial siderophores. Fe was measured in leaf fluid obtained by centrifugation according to a determination method based on Fe chelation by desferrioxamine E and HPLC separation on a reversed phase column. To avoid sample Fe contamination, treatments were only applied to a part of the leaf following a systematic and reproducible procedure and iron concentration was exclusively determined in fluid obtained from non-treated leaf surfaces. The increase in leaf fluid Fe concentration associated with the distribution of leaf applied Fe-siderophores, Fe–EDTA and FeSO₄ × 7H₂O was evaluated using Vicia faba L., Nicotiana tabacum L. and Citrus madurensis Lour. plants. The method proved useful to investigate the process of leaf Fe penetration and its distribution within the plant. Evidence of the penetration and distribution of leaf applied Fe-rhizoferrin, Fe-coprogen hydrolysis products and Fe-dimerum acid is presented in this study.     

The influence of substrate quality and stream size on wood decomposition dynamics

Woody materials decayed more rapidly in a first order stream than in larger streams in eastern Quebec, Canada. The rate of annual mass loss (k) was highest (k=1.20) for alder wood chips in a first order stream and lowest (k=0.04) for black spruce wood chips in a ninth order stream. Decay rates for woody materials in a first order stream were inversely related to their initial lignin to nitrogen ratios. In larger streams, decay rates of woody materials were inversely related to their initial lignin concentrations. A number of quantifiable relationships were found to exist between the initial lignin and nitrogen contents of woody materials and the nitrogen dynamics of decaying wood.     

Effect of foliar application of urea on the root microflora

The author studied the effect of the foliar application of urea on the microflora of the wheat root surface in relation to time. The effect of this treatment was manifested in the dry weight of the roots and in the parts above the ground seven days after application. The number of bacteria on the plants increased markedly on the first days after application, while the number of fungi showed a pronounced decrease. In time the differences were equalized. Bacteria requiring amino acids and growth factors predominated on the roots of treated plants, while the main fungi were members of the genusFusarium and in the control plants members of the genusPenicillium.     

The influence of substrate peptide length on human beta-tryptase specificity.

Combinatorial chemistry approach was applied to design chromogenic substrates of human beta-tryptase. The most active substrate, Ala-Ala-Pro-Ile-Arg-Asn-Lys-ANB-NH(2), was selected from among over 9 million heptapeptides. The amide of 5-amino-2-nitrobenzoic acid (ANB-NH(2)) attached at the C-terminus served as a chromophore. In order to determine the optimal length of the tryptase substrate, a series of N-terminally truncated fragments of this substrate was synthesized. Pro-Ile-Arg-Asn-Lys-ANB-NH(2), with the determined value of the specificity constant (k(cat)/K(M)) above 9 x 10(6) M(-1) s(-1), appeared to be the most specific substrate of tryptase. This substrate was twice as active as the parent heptapeptide substrate. We postulate that the optimal size of the pentapeptide substrate for the interaction with human beta-tryptase is associated with the unique structure of this proteinase, comprising four almost identical monomer subunits arranged in a square flat ring with its substrate pockets faced inside, forming a tetramer with a central pore that can be penetrated by this short peptide. Copyright (c) 2008 European Peptide Society and John Wiley & Sons, Ltd.     

Effect of manganese toxicity on the indoleacetic Acid oxidase system of cotton

The effect of substrate manganese on tissue manganese levels and activity of the indoleacetic acid (IAA)-oxidase system of cotton (Gossypium hirsutum, L.) was investigated. A sand culture technique was used with 1, 3, 9, 27 and 81 mg manganese (MnSO₄) per liter nutrient solution applied in various experiments.

The following relationships held for both long-term (126 days) and short-term (12-14 days) exposures to manganese treatment: A) There was a direct relationship between substrate and tissue manganese. B) Only the 81 mg/liter Mn plants exhibited severe manganese toxicity symptoms. C) At the toxic level of manganese an increased IAA-oxidase activity and decreased IAA-oxidase inhibitor activity was observed. There was a direct relationship between degree of enzyme response and severity of visible symptoms. D) With the manganese toxicity plants, but none of the other treatments, extracts of the young leaves contained as much IAA-oxidase activity as extracts of much older leaves. E) Crude extracts from the plants grown with 81 mg manganese per liter solution, in contrast to those of other treatments, destroyed IAA without addition of MnCl₂ to the assay medium.

A hypothesis is advanced stating that manganese toxicity symptoms in cotton are expressions of auxin deficiency caused by IAA-oxidase activity increased by the abnormal tissue levels of manganese.

     

The influence of foliar applications of sugars on the susceptibility of sugar beet to downy mildew

Spraying sugar-beet seedlings in the glasshouse, with 1% or 10% solutions of sucrose, 24 h before inoculation with Peronospora farinosa, significantly reduced their susceptibility to downy mildew. The proportion of inoculated plants that became infected was reduced by spraying with sucrose but the main effect was the inhibition of sporulation. Applications of glucose or fructose also increased the resistance of beet seedlings to P. farinosa. Spraying with sucrose 1 or 2 days before inoculation was much more effective than was spraying shortly before inoculation, or 24 h afterwards, or adding sucrose to the inoculum. Washing sucrose-sprayed seedlings with distilled water 1–2 h before inoculation removed only part of the effect of sucrose on sporulation. Although the mechanism by which applications of sugars affected susceptibility to downy mildew is not understood, the results suggest that the main effects occurred inside the host plant rather than externally. The possible significance of these results, in breeding for resistance to downy mildew and in the control of this disease in the field, is discussed.     

The influence of substrate particle size on the microdistribution of stream macrobenthos

Summary Substrate microhabitat preferences of ten species of benthic macroinvertebrates were investigated in a laboratory flowing water system and compared with preliminary field data. Eight particle size categories of both silted and non-silted substrates were tested in the laboratory.The correspondence between field and laboratory data indicated primary microhabitat selection on the basis of substrate particle size by the stonefly Perlesta placida, the riffle beetle Stenelmis crenata and the caddisflies Pycnopsyche guttifer and P. lepida. Broad substrate responses in the laboratory and lack of correspondence with field data indicated a secondary importance of substrate particle size in microhabitat selection by the pulmonate snail Helisoma anceps, the caddisfly Helicopsyche borealis, the cranefly Tipula caloptera, the alderfly Sialis vagans and the mayflies Caenis latipennis and Ephemera simulans.Silting had minor effects on substrate selection patterns in all species tested except Caenis latipennis and Perlesta placida in which it enhanced selection for the intersticies of coarse sediments.

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Zusammenfassung Die Vorliebe für Substratarten mit Rücksicht auf die Substratpartikelgrösse von zehn Arten im Benthos lebender Wirbelloser wurde in einer Labor-Fliesswasseranlage untersucht und mit vorläufigen Feldergebnissen verglichen. Acht Anordnungen von Substratpartikelgrössen, sowohl verschlammt als auch nicht verschlammt, wurden im Labor untersucht.Die Entsprechung zwischen Feld- und Laborergebnissen zeigte dass die Wahl des Lebensraumes in erster Linie durch die Substratpartikelgrösse bestimmt wurde für die Steinfliege Perlesta placida, den Hakenkäfer Stenelmis crenata und die Köcherfliegen Pycnopsyche gutiffer und P. lepida. Die breite Streuwirkung des Substrates im Labor und der Mangel an Übereinstimmung mit den Feldergebnissen zeigte, dass die Substratpartikelgrösse in der Wahl des Lebensraumes eine untergeordnete Rolle spielte bei der Lungenschnecke Helisoma anceps, der Köcherfliege Helicopsyche borealis, der Schnake Tipula caloptera, der Schlammfliege Sialis vagans und den Eintagsfliegen Caenis latipennis and Ephemera s simulans.Die Verschlammung hatte geringen Effekt auf die Auswahl des Substratesbei allen untersuchten Arten mit Ausnahme von Caenis latipennis und Perlesta placida. In diesen Fällen verstärkte sich die Besiedlung wegen der Zwischenräume in dem groben Sediment.

     

Toxicity of seven foliar insecticides to four insect parasitoids attacking citrus and cotton pests

Laboratory studies were carried out to compare the toxicity of seven foliar insecticides to four species of adult beneficial insects representing two families of Hymenoptera: Aphelinidae (Aphytis melinus Debach, Eretmocerus eremicus Rose & Zolnerowich, and Encarsiaformosa Gahan) and Mymaridae (Gonatocerus ashmeadi Girault) that attack California red scale, Aonidiella aurantii (Maskell); sweetpotato whitefly, Bemisia tabaci (Gennadius) (both E. eremicus and E. formosa); and glassy-winged sharpshooter, Homalodisca vitripennis (Germar), respectively. Insecticides from four pesticide classes were evaluated using a petri dish bioassay technique across a range of concentrations to develop dosage-mortality regressions. Insecticides tested included acetamiprid (neonicotinoid); chlorpyrifos (organophosphate); bifenthrin, cyfluthrin, and fenpropathrin (pyrethroids); and buprofezin and pyriproxyfen (insect growth regulators [IGRs]). Chlorpyrifos was consistently the most toxic pesticide to all four species of beneficial insects tested based on LC50 values recorded 24 h posttreatment compared with 48-h LC50 values with the neonicotinoid and pyrethroids or 96 h with the IGRs. Among the three pyrethroids, fenpropathrin was usually less toxic (except similar toxicity to A. melinus) than was cyfluthrin, and it was normally less toxic (except similar toxicity with E. formosa) than was bifenthrin. Acetamiprid was generally less toxic than bifenthrin (except similar toxicity with G. ashmeadi). The IGRs buprofezin and pyriproxyfen were usually less toxic than the contact pesticides, but we did not test for possible impacts on female fecundity. For all seven pesticides tested, A. melinus was the most susceptible parasitoid of the four test species. The data presented here will provide pest managers with specific information on the compatibility of select insecticides with natural enemies attacking citrus and cotton, Gossypium hirsutum L., pests.