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  • Articles  (74)
  • Rhizobium  (40)
  • Rhizosphere  (36)
  • 1980-1984  (74)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (74)
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  • Articles  (74)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 80 (1984), S. 297-300 
    ISSN: 1573-5036
    Keywords: Nodulation ; Non-nodulating soybean ; Rhizobitoxine ; Rhizobium ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A significant increase in nodulation of “non-nodulating” (rj1 rj1) soybeans was obtained by inoculating with very high numbers (approx. 1011 cells/pot) of certain rhizobia when compared with inoculation at a moderate dose (approx. 109 cells/pot). Nodulating ability of rhizobial strains was not correlated with their ability to produce a detectable level of chlorosis-inducing toxin in culture.
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  • 2
    ISSN: 1573-5036
    Keywords: Arthrocnemum ; Nitrification ; Rhizosphere ; Salinity ; Suaeda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The nitrification rate in the rhizosphere of Suaeda and Arthrocnemum plants growing in saline soils, as affected by microbial populations, temperature, pH, and organic matter, was examined in the field throughout the year. The genera Nitrosomonas and Nitrobacter were most common in the rhizosphere soil. The bacterial counts in the rhizosphere of both plants fluctuated during the study period, reaching peak values during February–March and in August. The nitrate concentration in the rhizosphere soil could be related with the observed increase in the numbers of ammonium-oxidizers and nitrite-oxidizers in the latter part of the study period. The pH of the rhizosphere soils did not have any influence on the nitrification rate at the values measured. The rhizosphere organic content varied between 1.8 and 4% (w/w), showing the continuous availability of organic matter in the soil. The seasonal changes in bacterial populations in the rhizospheres of both plants was described as the result of the combination of several factors.
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  • 3
    Electronic Resource
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    Plant and soil 82 (1984), S. 329-335 
    ISSN: 1573-5036
    Keywords: Legume breeding ; Medicago sativa ; Nitrogen fixation ; Rhizobium ; Trifolium repens ; Vicia faba
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This paper examines evidence which quantifies the relative importance of legume and Rhizobium genotypes as determinants of phenotypic variation in symbiotic nitrogen fixation. It demonstrates potentially large and unpredictable effects of the Rhizobium genotype. The likely importance of such effects on crop yield is considered. The information is then used to assess ways in which legume breeding programmes may be altered to encompass the effects of genetic variation in Rhizobium.
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  • 4
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    Plant and soil 82 (1984), S. 273-284 
    ISSN: 1573-5036
    Keywords: Legume ; Nitrogen fixation ; Rhizobium ; C and N economy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Studies of the C and N economy of a range of temperate and tropical legume/Rhizobium symbioses indicate considerable variation (up to three-fold) in the cost of N2 fixation. Comparisons between and within symbioses indicate that the proportion of net photosynthate utilized in nodule functioning varies almost ten-fold from as low as 3% to as high as 25%. Factors possibly responsible for variation in efficiency of C use in nodules and in the proportioning of translocated photosynthetic products to nodules are discussed.
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  • 5
    Electronic Resource
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    Plant and soil 80 (1984), S. 407-415 
    ISSN: 1573-5036
    Keywords: Cellulase ; Infection process ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The production of cellulase byRhizobium species was studied.Rhizobium trifolii cellulase was induced by a variety of polysaccharides, including celluloses and hemicelluloses. Cellobiose and myo-inositol also allowed enzyme expression but mannitol prevented it at concentrations higher than 0.25%. Both soluble and insoluble plant root substances moderately stimulated cellulase production byRhizobium trifolii. Most substances tested did not induce the production of cellulases by the “slow-growing, cowpea type” rhizobia strain CIAT 79. Effective inducers were carboxymethylcellulose, gluconate and myo-inositol. Cellulase production was very low under all conditions tested. In most cases the enzyme activity was loosely bound to the capsular material. The enzyme in fast-growers is an 1,4-β-D-glucan-4-glucanohydrolase (endo-glucanase EC 3.2.1.4) with specificity for high molecular weight polysaccharides. There was no correlation between infectiveness ofRhizobium trifolii strains and cellulase production. One strain, which lacks the nodulation plasmid, produced cellulase at the same rate as its parental infective strain.
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  • 6
    ISSN: 1573-5036
    Keywords: Aeration status ; Microorganisms ; Mucilage ; Rhizosphere ; Ultrastructure ; Wheat root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Outer layers of wheat roots grown in aerated and unaerated nutrient solutions were studied by transmission electron microscopy. Root growth was considerably impaired in unaerated nutrient solution. In contrast to aerated roots, no mucilaginous layer but dense bacterial colonization were observed on the root caps of unaerated roots. The root cap mucilage had apparently been decomposed by the microorganisms. The peripheral root cap cells of the unaerated roots appeared to contain less cell organelles than those of the aerated roots, while the central cap cells and the meristematic cells of the root tip seemed not to be affected by lack of aeration. The bacterial population in the elongation, root hair, and lateral root zones, was also remarkably higher on roots grown in unaerated nutrient solution. In the lateral root zone of unaerated roots, even the cortical cells were invaded by bacteria.
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  • 7
    ISSN: 1573-5036
    Keywords: Acidity ; Aluminium ; Cowpea ; Nitrogen ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The interaction of pH (4 or 6), aluminium (0 or 16 ppm at pH 4) and N source (symbiotic or combined) on the growth and nutrient status of cowpea (Vigna unguiculata) was studied in a glasshouse experiment. Low pH significantly decreased the growth of the plants dependent on symbiotic nitrogen fixation but at pH 4 the addition of 16 ppm Al further depressed growth in both nitrogen regimes. Al-ions appear to exert their effect primarily on the root system, as shown by the reduction in total length and fresh weight. The symbiotic development of the plants was affected by low pH but more markedly by the Al treatment. Shoot nitrogen concentrations were reduced from ca. 2.6% at pH 6 to 1.8% and 0.9% at pH 4 without and with aluminium respectively. Calcium concentration was decreased by low pH and further by Al in both nitrogen regimes. In all Al-treated plants, the aluminium was mainly accumulated in the roots and was associated with an increase in their phosphorus concentration.
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  • 8
    ISSN: 1573-5036
    Keywords: Glycine max ; Inoculation ; IW/CPE ratio ; Nitrogen accumulation ; Nitrogen harvest ; Nitrogen re-distribution ; Nodulation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A field experiment was conducted on soybean (Glycine max (L.) Merrill) with a view to find out the effect of seed inoculation and scheduling of irrigation on nodulation, accumulation and re-distribution of nitrogen in plant tops and soil. The eight treatment combinations consists of two seed inoculations,viz. uninoculated and inoculated with rhizobium culture, and four irrigation schedules,viz. irrigation water to the cumulative pan evaporation (IW/CPE) ratio of 0.5, 0.7, 0.9 and a control (rainfed). Seed inoculation by, rhizobium culture increased the number, dry-weight and N content of nodules per plant. Inoculation of seeds also increased the N accumulation rate in plant top and it was 2.48 kg/ha/day during the flower-initiation to the pod-initiation stage (30–60 days interval). At harvest, 32.2, 47.8 and 26.2 kg N/ha was re-distributed from the stems, leaves and pods-wall of inoculated plants to the grains, respectively. A total of 186.5 kg N/ha was harvested and 64.7 kg N/ha, was accumulated in soil under the inoculated condition. Scheduling of irrigation at 0.7 IW/CPE proved better, than other irrigation schedules and helped in increasing the nodulation, nitrogen accumulation and grain yield. As compared to control, 8.4, 17.8 and 18.4 kg more of N/ha was redistributed from the stems, leaves and pods-wall respectively when the irrigations were scheduled at 0.7 IW/CPE ratio. Under this irrigation schedule the total N harvest was 200.1 kg/ha while the total N increased by 55.9 kg over that present in soil at the time of sowing.
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  • 9
    ISSN: 1573-5036
    Keywords: Clover ; Nitrogen fixation ; Rhizobium ; Root nodule ; Selection and plant breeding ; Symbiosis ; Trifolium pratense ; T. subterraneum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This paper reviews (i) basic studies on the genetics of symbiosis in red clover (a self-sterile species) and subterranean clover (cleistogamous) and (ii) work on selection and plant breeding to increase nitrogen fixation in these hosts. Symbiotic effectiveness in red clover is influenced by many major and minor genes. The highly effective phenotype is inherited in a complex manner associated with early nodulation and the formation of large amounts of persistent bacteroid-containing tissue. Lines bred to fix more nitrogen with one strain ofRhizobium trifolii do so with most but not all other strains examined. They also show slightly increased vigour when grown on nitrate. The highly effective response is correlated with abundant nodulation and an early flowering habit, the evidence from breeding studies indicating that this correlation is not absolute. Normally effective and highly effective nodules have the same specific nitrogenase activities. The expression of the highly effective response is relatively little affected by environmental factors (temperature, light intensity, day length, supplementary carbon-di-oxide). Inbreeding substantially degrades the symbiotic response. Heterosis is shown in crosses between cultivars of subterranean clover but otherwise selection to increase effectiveness in this host was unsuccessful. The relevance of these results (and their physiological aspects) for the improvement of grain legumes is discussed.
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  • 10
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    Plant and soil 82 (1984), S. 377-386 
    ISSN: 1573-5036
    Keywords: Centrosema ; Desmodium ; Inoculation ; Nitrogen yield ; Nodulation ; Oxisol ; Pueraria ; Rhizobium ; Soil cores ; Stylosanthes ; Tropical forage legumes ; Zornia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three phases of Rhizobium inoculation trials were carried out as part of a programme to select forage legume germplasm adapted to acid, infertile Oxisols of tropical America. Firstly, a range of tropical forage legumes were evaluated for their response to N fertilization or inoculation with strains previously shown to be effective in Leonard jars, using cores of undisturbed soil or in the field at Carimagua, Meta, Colombia. In pure legume stands onlyCentrosema macrocarpum andC. pubescens showed increases in N yield due to both inoculation and N fertilization;C. brasilianum responded only to N fertilization;Zornia latifolia, Z. brasiliensis andStylosanthes capitata responded to neither treatment. Trials in cores and in grass-legume mixtures showed responses ofDesmodium ovalifolium, Pueraria phaseoloides andS. capitata to N fertilization but not to inoculation. In the second phase of experiments strains were screened in soil cores with 16 ecotypes ofDesmodium, Centrosema, Stylosanthes andPueraria spp. Significant increases in N yield due to inoculation occurred with at least one strain in all the legumes exceptS. guianensis ‘tardio’, and in some trials withS. capitata. In the third phase of trials the most effective strains were tested in the field. Significant response ofP. phaseoloides andC. macrocarpum to inoculation at two sites and in the second year after establishment were shown. Further screening trials and field trials at different sites are needed in order to provide better recommendations for inoculation of grazing trials being set up in the region under study.
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  • 11
    ISSN: 1573-5036
    Keywords: Abscisic acid ; Gibberellin ; Polyethylene glycol ; Rhizobium ; Roots ; Nitrogenase ; Nodulation ; Soya ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of 2-day cycles of osmotically induced leaf moisture stress followed by partial recovery on the nodulation and nitrogenase activity of 2 soya cultivars was studied. Fourteen days after plant inoculation (mid-growth stage) the total leaf electrochemical water potential (ψwleaf) of control plants ranged from −0.8 to −1.9 bars, whereas the concentrations of osmoticum (polyethylene glycol 4000) induced ψwleaf values ranging from −1.4 (recovery value) to −3.1 bars (low stress), −1.8 to −4.4 bars (mild stress), and −2.2 to −6.2 bars (medium stress). The low stress treatment reduced nodule numbers and their specific activity in both cultivars, without affecting nodule size or the time required for nodule initiation. Nodule initiation was delayed in both cultivars by the mild and medium stress treatments, the former treatment reducing the number and size of the nodules and such nodules exhibited very low specific activity. The medium stress treatment prevented the further development of nodule initials, which remained inactive throughout the experiment. Such results imply an effect of water stress on the infection process and on nodule morphogenesis. The reduction in nodule numbers observed in water stressed plants was not associated with a reduced number of rhizobia in the rhizoplane nor due to an effect on root growth or root hair formation. At a stage prior to the formation of macroscopic nodule initials, the roots of plants under medium stress (ψwleaf=−5.5 bar)s) had a higher content of abscisic acid (ABA) (4-fold increase) and a lower content of gibberellin (GA)-like substances (21.4% reduction) as compared to control plants (ψwleaf=−1.0 bar). Although the medium stress treatment slightly increased the stomatal resistance of leaves, photosynthetic and transpiration rates were unaffected. Similar alterations of the hormononal balance occurred in the nodulated roots of plants subjected to naturally induced leaf moisture stress. Since the foliar application of ABA (1.92×10−5 M) to unstressed plants inhibited nodulation (45% reduction in nodule numbers), the increased endogenous content of thishormone in the roots of plants under leaf moisture stress may provide some physiological insight into the inhibitory effect of water stress on the nodulation process.
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  • 12
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    Plant and soil 80 (1984), S. 363-371 
    ISSN: 1573-5036
    Keywords: Fluorescence microscopy ; Exudates ; Microbial ecology ; Model root ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The construction and assembly of a model root region is described. The model was used to manipulate the soil matrix, soil microorganisms, and to simulate release of root exudates. The design of the apparatus facilitated long-term, direct microscopic observations of microbial activity in soil and on artificial roots. Preliminary studies indicate that microbial responses to osmotic stress and to changes in components of exudate solutions are easily monitored.
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  • 13
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    Plant and soil 55 (1980), S. 163-165 
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Nitrogen fixation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method is described to demonstrate nitrogen fixation by free-living Rhizobium cells. After aerobic growth in a nutrient solution, the bacteria are centrifuged. Acetylene reduction by the rhizobial cells in the pellet can be measured within a few days. Hydrogen gas frequently stimulates acetylene reduction.
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  • 14
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    Plant and soil 54 (1980), S. 95-106 
    ISSN: 1573-5036
    Keywords: Acid soil ; Antibiotic resistance ; Competition ; Rhizobium ; Soybean ; Symbiotic nitrogen fixation ; Tropical Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The efficacy of inoculating soybean cvs. TGm294-4 and TGm80 in an acid soil (pH 4.6, water) was studied in a field trial in Nigeria.Rhizobium japonicum strains CB1809str r and 46spc r which had been selected for symbiotic competence in the acid soil were used as inocula. Other treatments included no inoculation, combined nitrogen (150 kg N ha−1) and lime (1 t ha−1). Plants grown in acid soil without inoculation and lime had very few nodules, were nitrogen deficient and grain yields were poor (0.3–0.4 t ha−1). Yield responses to combined nitrogen were generally small due to fertilizer loss through leaching. Inoculation greatly increased nodulation, shoot dry matter and shoot N%; grain yields were between 1.6 and 2.0 t ha−1. Lime improved all harvest measurements in the uninoculated and nitrogen treatments but not in the inoculated treatments. In a duplicate trial without lime on near-neutral soil, similar inoculation responses were obtained at 6 weeks. However, at final harvest there were no significant differences in grain yield between treatments due to late, effective nodulation by unidentified strains in the uninoculated treatments. Assays for strain identity confirmed the successful establishment of the inocula in both soils, with 100% of nodules from inoculated plants containing an introduced strain.
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  • 15
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    Plant and soil 54 (1980), S. 163-167 
    ISSN: 1573-5036
    Keywords: Phytoalexin ; Phytophthora megasperma ; Salinity ; Soybean ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rhizosphere salinity decreased the capacity of soybean to accumulate a pterocarpanoid phytoalexin (glyceollin) in the stem in response toPhytophthora megasperma var.sojae. Rapid (48h) accumulation was depressed by NaCl, Na2SO4, CaCl2 and MgSO4 applications. Time-course accumulations was slowed by applications. Time-course accumulation was slowed by application of 0.131M NaCl. Glyceollin accumulation was also reduced in plants subjected to a period of high salinity stress (0.177M NaCl, 72 h) after a period of nonsalinized growth. Calcium chloride completely suppressed glyceollin accumulation in normally-resistant plants but no susceptibility to the fungus was observed.
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  • 16
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    Plant and soil 54 (1980), S. 185-193 
    ISSN: 1573-5036
    Keywords: Calluna vulgaris ; Dark sterile forms ; Deschampsia flexuosa ; Fascicle ; Mycoflora ; Oidiospores ; Oxycoccus palustris ; Pernettya mucronata ; Reproductive ; structures ; Rhizosphere ; Root-inhabiting fungi ; Saprophytic survival ; Segmenting ; Vaccinium myrtillus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many different species of fungi have been isolated from the root region of heath plants. In the absence of rapidly growing species,Dark Sterile forms predominated in culture plates. It is suggested that these have an important ecological role in the soil-root interface. AsDS forms do not appear in culture plates easily any floristic list of fungi from the root surface not mentioningDS forms must be accepted with caution. Attention is drawn to the fact that these are truly root-inhabiting fungi possessing some parasitic or mycorrhizal propensities.
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  • 17
    ISSN: 1573-5036
    Keywords: Brackish water alluvial soil ; Crop-induced phosphate mobilization ; Flooded soils ; Immobilization ; Resin extractable phosphate ; Rhizosphere ; Rice ; Sandy loam soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Poor or lack of response of lowland rice to P fertilization is a well-known fact. Several studies were conducted in this direction however, our understanding regarding the underlying mechanism has been far from clear. A remarkable influence of rice plants on P transformation in submerged soil is identified in this experiment which may shed light on this problem. Accordingly, in presence of rice plants P was mobilized during the initial growing period followed by immobilization. The increased microbial activity in presence of physiologically active roots was responsible for P mobilization, while capacity of rice plants to reoxidize the rhizosphere, by secretion of oxygen from roots, during later growing period was responsible for P immobilization. The extent of P mobilization decreased while that of immobilization increased with increasing P levels in different soils. At a given P level the ratio of P mobilization to immobilization was higher in a soil where crop growth was better and P uptake was higher as compared to another soil where crop growth was poor with lower P uptake. Thus, lowland rice plants appear to possess an unique physiological mechanism, to regulate the contrasting changes in P availability in the rhizosphere depending on P requirement by the plants or P availability in soil, which in turn is responsible for the poor or lack of response to P fertilization. The experiment was conducted in a growth chamber. Two soils with widely varying properties were used.
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  • 18
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    Plant and soil 56 (1980), S. 33-37 
    ISSN: 1573-5036
    Keywords: Autochthonous ; Nodule bacteria ; Nodulation ; Plantations ; Rhizobium ; Shelter belts ; Tree legumes ; Wind breaker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Twenty five species of tree legumes, belonging to genera Acacia, Albizzia, Bauhinia, Colophospermum, Dichrostachys, Leucaena, Peltophorum, Pithecolobium and Prosopis were examined for nodulation under pot culture conditions using unsterilized soil. Out of these, only nineteen tree-legumes nodulated. It was interesting to note that all the three species of Bauhinia and one each of Acacia, Colophospermum and Peltophorum did not nodulate both at Jodhpur and Delhi. Inoculation of tree legumes with their own rhizobial isolates, improved nodulation under sterilized conditions.
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  • 19
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    Plant and soil 56 (1980), S. 325-329 
    ISSN: 1573-5036
    Keywords: Cluster bean ; Cyanopsis tetragonoloba ; Rhizosphere ; Tobacco necrosis virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In TNV-bearing soils, the virus occurred adsorbed to soil colloids in low levels. By direct assay, the TNV could be more readily isolated from the rhizosphere of naturally infected cluster bean plants. The level of reaction of the TNV isolated from the rhizosphere soil was the same as TNV-D (cb isolate) in precipitin ring tests with antisera against TNV-A and TNV-D. The phenomenon of release of TNV from the infected roots into the soil and adsorption of TNV particles to colloidal particles in the soil are discussed from the point of ecology and stability of TNV in soils.
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  • 20
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Asymbiotic nitrogen fixation ; Grasslands ; Rhizosphere ; Stripmined land reclamation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary From 36 to 71% of bacteria, depending on the sampling site, that were isolated from the soil or rhizosphere of undisturbed prairie soil or reclamation sites of strip-mined grassland areas in western North Dakota were capable of reducing acetylene. These bacteria generally could be divided into two populations; one capable of acetylene reduction under aerobic conditions and another capable of acetylene reduction under anaerobic conditions. The reclamation site to which no topsoil had been applied, pH 8.5, had a bacterial population which generally was capable of higher levels of acetylene reduction than individual bacteria isolated from other sites.
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  • 21
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    Plant and soil 59 (1981), S. 473-477 
    ISSN: 1573-5036
    Keywords: Hexachloroxyclohexane ; Nitrogenase activity ; Nitrogen fixation ; Redox potential ; Rhizosphere ; Rice plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of application of hexachlorocyclohexane (HCH=gamma BHC), to a submerged tropical field soil at rates equivalent to recommended field rates (1–2.5kg a.i./ha) and twice this level, upon the rhizosphere soil nitrogenase, nitrogen fixers, and soil redox potential (Eh) was investigated. The rhizosphere soil from HCH-treated field exhibited significantly higher nitrogenase activity than that from untreated fields. HCH retarded the drop in redox potential of the field soil upto 80 days after transplantation under submerged conditions. Populations of nitrogen-fixingAzospirillum sp. and Azotobacter, to a greater extent, and anaerobic organisms, to a lesser extent, were stimulated in HCH-treated soils. Results indicate the stimulation of heterotrophic nitrogen-fixing bacteria by HCH in submerged paddy soils.
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  • 22
    ISSN: 1573-5036
    Keywords: Nutrient supply ; Nodule effectiveness ; Rhizobium competition ; Nodulation ; Lotus pedunculatus ; Lotus ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of nutrient supply on nodule formation and competition between Rhizobium strains for nodulation ofLotus pedunculatus was studied. Limiting plant growth by decreasing the supply of nutrients in an otherwise nitrogen-free medium, increased the size but decreased the number and the nitrogenase activity of nodules formed by a fast-growing strain of Lotus Rhizobium (NZP2037). In contrast decreasing nutrient supply caused only a small decline in the size, number and nitrogenase activity of nodules formed by a slow-growing strain (CC814s). Providing small quantities of NH4NO3 (50 to 250 μg N) to plants grown with a normal supply of other nutrients stimulated nodule development by both Rhizobium strains and increased the nitrogenase activity of the NZP2037 nodules. Differences in the level of effectiveness (nitrogen-fixing ability) of nodules formed by different Rhizobium strains on plants grown with a normal supply of nutrients were less apparent when the plants were grown with decreased nutrient supply or when the plants were supplied with low levels of inorganic N. Inter-strain competition for nodulation ofL. pedunculatus between the highly effective slow-growing strain CC814s and 7 other fast- and slow-growing strains, showed CC814s to form 42 to 100% of the nodules in all associations. The greater nodulating competitiveness of strain CC814s prevailed despite changes in the nutrient supply to the host plant. A tendency was observed for partially effective Lotus Rhizobium strains to become more competitive in nodule formation when plant growth was supplemented with low levels of inorganic nitrogen.
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  • 23
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    Plant and soil 61 (1981), S. 43-52 
    ISSN: 1573-5036
    Keywords: Adaptation ; Allelopathy ; Ecophysiology ; Grassland ; Plantago ; Nitrate production ; Nitrate reductase ; Nitrate uptake ; Nitrification ; Nitrifying bacteria ; Rhizosphere ; Root environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The production of nitrate in an old established dune grassland soil and its uptake by plants was studied by comparing amounts of mineral nitrogen and numbers of nitrifying bacteria in the rhizosphere on the one hand, and on the other accumulated nitrate and levels of nitrate reductase (NaR) of individual plants of three Plantago species,i. e., P. major, P. lanceolata andP. coronopus. For these three Plantago species andP. media basal levels of NaR in the absence of nitrate were determined in plants grown in culture solutions. The basal NaR levels ofP. major andP. media (species occurring on nutrient-rich soils) were significantly higher than those ofP. lanceolata andP. coronopus (species found on nutrient-poor soils). NaR activity increased in the presence of nitrate and was suppressed by ammonium. From the numbers of nitrifying bacteria in the rhizosphere and NaR activity in the leaves it was concluded that nitrate was produced in the root environments of the three Plantago species and that the compound was taken up by the plants. NaR activities and numbers of nitrifying bacteria were higher for individuals ofP. major than for those ofP. lanceolata andP. coronopus. No correlation was found between the ammonium levels and the numbers of nitrifying bacteria in the soil, and no indications of inhibition of nitrifying bacteria in the rhizosphere were obtained. For individuals ofP. lanceolata a correlation was found between the numbers of nitrifying bacteria in the soil and NaR activity in the leaves. The results are discussed in relation to the ecological habitats of the three species.
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  • 24
    ISSN: 1573-5036
    Keywords: Acridine orange ; Barley ; Cerelas ; Microdochium bolleyi ; Nuclear staining ; Phialophora radicicola ; Rhizosphere ; Root cortex death ; Take-all ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nuclear staining with acridine orange was used to assess cell viability in the cortex of wheat and barley seminal roots from glasshouse and field experiments. Results from this method correlated well with nuclear assessments made in unstained or Feulgen-stained roots, and other evidence is presented to support the validity of the method. The pattern of root cortex death (RCD) was similar in wheat and barley and consistent over a wide range of conditions. Behind the extending root tip and zone of nucleate root hairs, nuclei disappeared progressively from the outer five (of six) cortical cell layers of the root axes, starting in the epidermis. Stainable nuclei remained in the sixth cell layer, next to the endodermis, and in most cell layers around the bases of root laterals and in a small region immediately below the grain. The onset of cell death was apparently related more to the age of a root region than to its distance behind the root tip, and it was not closely correlated with endodermal or stelar development assessed by staining with phloroglucinol/HCl. The rate of RCD was much faster in wheat than barley in both glasshouse and field conditions, and faster in some spring wheat cultivars than in others in the glasshouse. RCD occurred in sterile vermiculite and perlite and was not enhanced by the presence of soil microorganisms; nor was it enhanced in soil by the addition of the non-pathogenic fungal parasitesPhialophora radicicola var..graminicola orMicrodochium bolleyi. RCD is suggested to be endogenously controlled by the amount of photosynthate reaching the cortex. Its implications for growth of soil microorganisms and especially for growth and biological control of root-infecting fungi are discussed.
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  • 25
    ISSN: 1573-5036
    Keywords: Bacteroids ; Cowpea ; Nitrogen fixation ; Peanut ; Rhizobium ; Siratro
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Acetylene reduction activity and nitrogen accumulation in the plant top per unit nodule mass were compared among peanut, cowpea and siratro plants nodulated by six different strains of Rhizobium. Peanut was found to have several fold higher values than cowpea and siratro for both parameters for all strains of Rhizobium which nodulated it effectively, but the bacteroid content of the peanut nodules was similar to those of cowpea and siratro.
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  • 26
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    Plant and soil 60 (1981), S. 349-356 
    ISSN: 1573-5036
    Keywords: Competition ; Cowpea ; Ineffective ; Mutagenesis ; Mutants ; Nodulation ; Rhizobium ; Symbiotic and asymbiotic nitrogen-fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A strain of cowpea Rhizobium was mutagenised and two ineffective mutants, M1 and M2, and an effective mutant, M3, were isolated. M1 produced more, but smaller nodules than the wild-type; these nodules lacked leghaemoglobin. M2 and the parental strain had similar nodulation characteristics, both forming large pink nodules. Plants inoculated with M3, nodulated earlier, produced more nodules (58%), had increased dry weights (26%) and the excised roots expressed greater acetylene (C2H2) reducing activity (39%) than plants inoculated with the wild-type. When competing with an indigenous population of effective rhizobia for nodule sites, M3 produced a higher proportion of the nodules (70–80%) than the parental strain (40–53%). M3 and the parental strain exhibited comparable rates of asymbiotic C2H2 reduction when grown on a defined medium, whereas M1 and M2 were inactive. The symbiotic properties of the mutants were unchanged after their reisolation following plant passage.
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  • 27
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    Plant and soil 60 (1981), S. 445-450 
    ISSN: 1573-5036
    Keywords: Rhizobium ; Symbiosis ; Soil moisture stress ; Soybeans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In a pot culture experiment, the influence of soil moisture stress at different physiological stages of soybean, cv. Hark, on nodulation, symbiosis and nitrogen accumulation was studied. Moisture stress reduced leghemoglobin content of root nodules and nitrogen uptake by plants. It had no effect on number of bacteroids. Stress at mid bloom and rapid pod filling stages reduced yield and seed protein content. However, these parameters were not affected by stress at nodule initiation and early flowering stages, though, flower initiation and maturity of the plant were delayed. Moisture stress at any stage did not alter nitrogen status of roots.
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  • 28
    ISSN: 1573-5036
    Keywords: Arthrobacter ; Blue grama ; Bouteloua gracilis ; Herbage removal ; Pseudomonas ; Rhizoplane ; Rhizosphere ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Streptomycin-resistant Pseudomonas and Arthrobacter were isolated from semi-arid grassland soil and their relative responses in the rhizosphere of blue grama (Bouteloua gracilis) subjected to herbage removal were evaluated. Using plants grown in normal soil, the two bacteria showed differential responses to herbage removal, which were most marked in the rhizoplane, where the Pseudomonas showed a two-log unit increase over a 60 hour period, while Arthrobacter, in contrast, exhibited a one-log unit decrease in viable counts for at least 48 hours after defoliation, responses which are similar to those observed in root exudate medium experiments by earlier workers. These results suggest that the rhizoplane may be a critical environment for interaction of these two types of microorganisms, and that sequential responses of the root-associated soil microorganisms may occur after herbage removal from this important rangeland plant. These responses are most likely associated with increased exudate release following herbage removal, which has been best documented using blue grama grown under sterile conditions.
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  • 29
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    Plant and soil 65 (1982), S. 345-349 
    ISSN: 1573-5036
    Keywords: Ammonium ; Fixed ammonium ; Maize ; Mineralization ; Nitrate ; Nitrite ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Significantly lower amounts of exchaneable NH4, soluble NO3 and clay-fixed NH4 forms of N were observed in the unfertilized fields with high rather than low-density cropped plots. Irrespective of planting densitites, the fixed NH4 content in soil increased with increase in the period of crop growth. N uptake by plant and total bacterial population of rhizosphere soil were significantly higher in the plots with the high than with the low-density planting. Availability of native fixed NH4 + to crops and biological utilization of a considerable amount of recently mineralized NH4 + in fixed form is indicated.
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  • 30
    ISSN: 1573-5036
    Keywords: Isotope techniques ; Nitrogen-15 ; Nitrogen fixation ; Nitrogen utilization ; Phaseolus vulgaris ; Rhizobium ; Varietal comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Differences in N2-fixation byPhaseolus vulgaris bean cultivars were successfully evaluated in the field using15N isotope dilution technique with a non-fixing test crop of a different species (wheat). The Phaseolus cultivars could have been similarly ranked for N2-fixation capacity from either seed yield or total nitrogen yield, but the isotope method provided a direct measure of N2-fixation and made it possible to estimate the proportion of fixed to total nitrogen in the crop and in plant parts. Amounts of nitrogen fixed varied between 24.59 kg N/ha for the 60-day cultivar Goiano precoce to 64.91 kg N/ha for the 90-day cultivar Carioca. The per cent of plant nitrogen due to fixation was 57–68% for the 90-day cultivars and 37% for Goiano precoce (60-day cultivar). Fertilizer utilization was 17–30% of a 20 kg N/ha fertilizer application. 100 kg N/ha fertilizer application decreased N2-fixation without suppressing it totally. Differences in yield between the highest yielding (Carioca) and the lowest (Moruna) 90-day cultivars were also due apparently to varietal differences in efficiency of conversion of nitrogen to economic matteri.e. seed, as well as to differences in capacity of genotypes for N2-fixation.
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  • 31
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    Plant and soil 65 (1982), S. 425-428 
    ISSN: 1573-5036
    Keywords: Chlorosis ; Cowpea ; Nodulation ; Rhizobitoxine ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary While screening cowpea rhizobia from West Africa for ability to nodulate various host species, foliar chlorosis was observed in young mung bean and soybean plants inoculated with certain strains. The chlorosis occurred in the first and sometimes the second trifoliate, but not on subsequent leaves. There was no correlation of symptoms with the presence of nodules. Where extreme chlorosis was induced in soybeans, there was stunting of the primary root. Disease symptoms were obtained with culture-broth supernatants free of rhizobia, indicating an extracellular toxin. In common with rhizobitoxine-producing strains ofR. japonicum, chlorosis-inducing cowpea strains were able to nodulate ‘non-nodulating’ soybeans of the rj1rj1 genotype.
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  • 32
    ISSN: 1573-5036
    Keywords: Rhizosphere ; Salt tolerance ; Soil solution ; Sugar beet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Junge Zuckerrübenpflanzen, deren Wurzeln wurzelnahen Bodenlösungen mit hohen Salzkonzentrationen (bis 〈−3,0 MPa) ausgesetzt waren, paßten sich dem Salzstreß durch Erhöhung ihrer Gehalte on osmotisch wirksamen Substanzen (OWS) an. Der OWS-Anstieg war in den Wurzeln deutlich geringer als in den Sprossen. In den wurzelnahen Bodenlösungen junger, welkender Zuckerrüben wurden maximale Salzkonzentrationen, die ψo-Werten von −1,6 bis 〈−3,0 MPa entsprachen, gefunden. Diese erheblichen Unterschiede standen in enger Beziehung mit den ψo-Werten der welkenden Sprosse. Es wird gefolgert, daß die maximale Salzkonzentration der wurzelnahen Bodenlösung, aus der eine wurzel kaum noch Wasser entziehen kann, in etwa dem ψo-Wert der welkenden Blätter entspricht.
    Notes: Summary When roots of young sugar beets were exposed to rhizospheric soil solutions of high salt concentrations (up to 〈−3,0 MPa) their adaption occurred by increasing their contents in osmotically effective substances (OES). The increase of the OES-contents was much smaller in the roots than in the shoots. In the rhizospheric soil solutions of young, wilting sugar beets there were found maximum salt concentrations ranging from −1,6 to 〈−3,0 MPa. These large differences were closely related to the ψo-values found in the wilting shoots. It is concluded that the maximum salt concentration of the rhizospheric soil solution preventing uptake of soil water corresponds to the ψo-values of the wilting shoot.
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  • 33
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    Plant and soil 68 (1982), S. 217-222 
    ISSN: 1573-5036
    Keywords: Nitrogen fixation ; Oryza sativa ; Phragmites communis ; Reed ; Rhizosphere ; Rice ; Roots ; Soil temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relation of nitrogenase activity (ethylene evolution) to soil temperature or incubation temperature of roots was determined on two genera of swamp plants, namely rice (Oryza sativa) cultivated in tropical climate and reed (Phragmites communis) grown in temperate regions. For both intact rice plants and excised rice roots the optimum temperature was 35°C. On excised roots nitrogenase activity responded more sensitivity to changes in temperature. In contrast to intact rice plants no ethylene evolution occurred on excised roots at 17 and 44°C. On reed roots temperature optimum was between 26 and 30°C which is clearly lower than on rice (35°C). The temperature range in which nitrogen fixation occurred was, however, similar to that of rice, although on a lower level. The results suggest a higher potential of the tropics for associative N2 fixation, while in cooler climates the lower temperatures appear to be a major limiting factor.
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  • 34
    ISSN: 1573-5036
    Keywords: Breeding ; Cowpea ; Nitrogen nutrition ; Rhizobium ; Seed yield ; Symbiotic interactions ; Vigna unguiculata L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Plant of cowpea (Vigna unguiculata (L.) Walp.) cv. TVu 1469 were grown in a plastic house set to simulate tropical temperatures. They were inoculated with one of two strains of Rhizobium and irrigated each day with nutrient solution either devoid of inorganic nitrogen (N) or containing 2.14 mM (30 ppm) N. Strain of Rhizobium significantly affected rates of dry matter and N accumulation as well as the total N content of mature plants. Variations in seed yield were due largely to Rhizobium effects on peduncle production and pod set on each peduncle, wheres inorganic N did not change these yield-determining components significantly. The agronomic and physiological implications of these data are discussed.
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  • 35
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    Plant and soil 70 (1983), S. 147-150 
    ISSN: 1573-5036
    Keywords: Aluminium ; Arachis hypogea ; Chlorose ; Nématode ; Rhizobium ; Sénégal ; Scutellonema cavenessi ; ‘Yellow patches’
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary The authors' analysis of Drevon and Diabaye's article on “yellow patches’ disease of peanuts in Sénégal3 underlines the weakness of the latter's conclusions which tended to attribute this disease to a combination of low soil pH, presence of exchangeable aluminium and a low number of Rhizobium. Taking into account these factors, the authors advance a more complete and better founded explanation which attributes a fundamental role to the nematodeScutellonema cavenessi, a role which has been demonstrated in many previous field and laboratory studies.
    Notes: Résumé Les auteurs, analysant l'article de Drevon et Diabaye concernant la maladie des ‘taches jaunes’ de l'arachide au Sénégal3, relèvent la faiblesse des conclusions; celles-ci tendent à attribuer cette maladie à la conjonction d'un pH bas des sol, la présences d'aluminium échangeable et le faible volume de Rhizobium. Sans négliger ces éléments, les auteurs avancent une explication plus globale et mieux fondée, dans laquelle l'action du nématodeScutellonema cavenessi reste primordiale, ainsi que de nombreuses observations et expérimentations l'ont, antérieurement, démontré.
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  • 36
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    Plant and soil 76 (1984), S. 77-91 
    ISSN: 1573-5036
    Keywords: Microorganisms ; Mycorrhizas ; Nitrogen fixation ; Phosphate uptake ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary No root systems in nature are without a microbial population. These may be freeliving or symbiotic. The incidence and nutrition of the freeliving microorganisms is discussed. Shortage of substrate makes it unlikely that the N-fixers in the population can fix useful amounts of N. There is a possibility that P supply is improved, but an analysis of possible processes shows them to be rather unlikely, and evidence for them to be poor. Manganese and iron uptake can be altered by microbial activity. Growth of plants can be affected by non-nutritional bacterial effects. The ecology of Rhizobium in the soil is briefly discussed, and the varying needs of different identified strains is stressed. Mycorrhizal infection of plants leads to large growth increases in appropriate conditions. This is almost always linked to increased P uptake, but zinc and copper nutrition can also be improved. The processes involved are briefly discussed. Rapid and extensive infection is important; it is very sensitive to temperature. New modelling methods are now becoming available to measure the behaviour of the fungal infections. The microorganisms require C compounds from the plant, and new measurements of this cost are discussed. The possibility of practical use of mycorrhizal fungi seem to be improving.
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  • 37
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    Plant and soil 78 (1984), S. 367-379 
    ISSN: 1573-5036
    Keywords: Acidity ; Aluminium ; Calcium ; Manganese ; Nodulation ; pH Rhizobium ; Rhizosphere ; Root elongation ; Root hairs ; Trifolium repens ; White clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Effects of factors associated with soil acidity (low pH, low calcium, high aluminium and high manganese) on theTrifolium repens-Rhizobium trifolii symbiosis were investigted under laboratory conditions using an axenic solution-culture technique. 200 μM manganese increased root elongation in the range pH 4.3–5.5, but had no effect on root hair formation, the number of Rhizobium in the rhizosphere, or nodule formation. Root elongation and root hair formation were unaffected at pH 4.3 when 500 or 1000μM calcium was supplied, whereas multiplication of Rhizobium in the rhizosphere and nodulation were inhibited at pH 4.3 and 4.7.50–1000μM calcium had no effect either on the multiplication of Rhizobium in the range pH 4.3–5.5, or on nodule formation in the absence of aluminium. 50 μM aluminium inhibited, root elongation and root hair formation at pH 4.3 and 4.7; the effect on root elongation was reduced by increasing the calcium concentration from 50 to 1000μM. 50μM aluminium also inhibited Rhizobium multiplication in the rhizosphere and reduced nodule formation at pH 5.5 (at which aluminium precipitated out of solution), but root elongation and root hair formation were unaffected. These, effects of aluminium at pH 5.5 may explain the poor response to inoculation by white clover in acid mineral soils after liming.
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  • 38
    ISSN: 1573-5036
    Keywords: Acid soils ; Nitrogen fertilizer ; Rhizobium ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Soybean cultivar MTD10 cultivated on a moderate acid paddy soil of the Mekong Delta responded well to a multistrain inoculation and to chemical nitrogen fertilizer. However, the efficiency of chemical nitrogen uptake by the uninoculated plants decreased with increasing nitrogen application rate. Inoculation improved all examined agronomic characteristics of plants. Inoculated plants produced grain yield 10 times greater than the uninoculated controls and 2.5 times greater than the uninoculated plants receiving 80 kg/ha of chemical nitrogen. Inoculation was superior to chemical nitrogen fertilization in all parameters of importance to market-oriented farmers.
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  • 39
    ISSN: 1573-5036
    Keywords: Centrosema ; Desmodium ; Inoculation ; Nitrogen yield ; Nodulation ; Oxisol Pueraria ; Rhizobium ; Soil cores ; Stylosanthes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three experiments were conducted in an acid infertile Oxisol from the Llanos Orientales of Colombia. It was shown that greater increases in nitrogen yield in the tops (N yield) due to N fertilization ofPueraria phaseoloides (CIAT germplasm accession no. 9900),Stylosanthes capitata no. 1019,Centrosema macrocarpum no. 5065 andDesmodium ovalifolium no. 350 occurred in undisturbed soil cores than in pots of disturbed soil. Inoculation significantly increased N yield ofC. macrocarpum in soil cores, but not in pots. In screening trials where a range of Rhizobium strains was used to inoculateD. ovalifolium, P. phaseoloides andC. macrocarpum grown in undisturbed soil cores, strains CIAT 2335, 2434 and 1780, respectively, caused the greatest increases in N yield. Inoculation caused greater increases of nodule numbers relative to the uninoculated control inC. macrocarpum than inD. ovalifolium orP. phaseoloides. When each legume was inoculated with the most effective strain by different methods, and grown in soil cores, it was found that granulated inoculant (0.5 g/seed) was more effective than seeds pelleted with 50 g inoculant/kg for the small-seededD. ovalifolium, but was similar in effectiveness to pelleted inoculant for the larger-seededP. phaseoloides. With the relatively large-seededC. macrocarpum, granulated inoculant was less effective than pelleted inoculant. No clear differences between different types of pellets were observed. The results show that undisturbed cores of acid infertile Oxisol can be used to screen for Rhizobium strains tolerant to these adverse soil conditions, although selected strains should then be subjected to further screening in the field, to determine whether they would make suitable commercial inoculants. It may not be possible to obtain maximum responses to inoculation by all legumes, unless the inoculation methods used here are improved.
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  • 40
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    Plant and soil 64 (1982), S. 369-380 
    ISSN: 1573-5036
    Keywords: French beans ; Nutrient uptake ; pH ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract French bean seedlings grown on choline, ammoniacal and nitrate forms of nitrogen together with equivalent basal application of P as KH2PO4 were tested for nutrient uptake from the rhizosphere. Statistical tests on soil (rhizosphere and non-rhizosphere) and plant (root and shoot) revealed that with the exception of P, levels of all other estimated macro-(Na+, K+, Ca2+, Mg2+) and micro-nutrients (Fe2+, Mn2+, Zn2+) were significantly changed after 42 days growth as compared to 21 days growth period. The higher uptake into shoots of Na+, K+, Fe2+, Mn2+, Zn2+ and H2PO4 − and higher biomass accumulation in the rhizosphere were associated with lower rhizosphere pH. The uptake of Ca2+ and Mg2+ increased with higher rhizosphere pH. While ammoniacal and choline forms decreased rhizosphere pH and increased the P uptake, nitrate form reversed the trend showing significant inverse relationship between shoot phosphate and rhizosphere pH. Calcium and iron were associated with an inhibition of the translocation of P from root to shoot. However, no causal relationships could be established. Both shoot weight and shoot P content were closely associated with a number of rhizosphere soil parameters.
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  • 41
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    Plant and soil 64 (1982), S. 431-435 
    ISSN: 1573-5036
    Keywords: Antarctic ; Hyphomycetes ; Monacrosporium cionopagum ; Monacrosporium ellipsosporum ; Nematophagous ; Predaceous fungi ; Rhizosphere ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The present investigation examines the comparative growth rates, at various temperatures between 4 and 30°C, of two nematophagous fungiMonacrosporium ellipsosporum (Preuss), (Grove), Cooke and Dickinson andM. cionapagum (Drechsler), (Subramanian), Cooke and Dickinson, both isolated from the Antarctic and from Britain. No psychrophilic species were found although the results clearly show that both the Antarctic isolates were psychro-tolerant, displaying lower minimum, optimum and maximum temperatures for growth than the British isolates. A modified form ofM. ellipsosporum isolated from the Antarctic grew only between 4 and 15°C, indicating it to be much better adapted to such cold habitats than the other isolates examined.
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  • 42
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    Plant and soil 67 (1982), S. 293-303 
    ISSN: 1573-5036
    Keywords: Burning ; Denitrification ; N-cycling ; N2-fixation ; Nitrification ; Oxisol ; Rhizobium ; Savanna ; South America ; Ultisol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Las sabanas ocupan alrededor de 300 millones de hectáreas de Sudamérica. Los suelos son básicamente oxisoles y ultisoles de muy baja fertilidad y alta acidez. La vegetación natural varía en densidad y en la cantidad de biomasa producida anualmente, la cual puede llegar a ser igual a la producida por bosques de la región. Entre los microorganismos fijadores de nitrógeno, los únicos bien estudiados son las bacterias del género Rhizobium. En el manejo de la biomasa de estas áreas, es importance considerar la fijación del nitrógeno, como una fuente posible que reemplace al que fué exportado en las cosechas. La nitrificación y la denitrificación en estos, es intensa pero no bien estudiada. La distribución de lluvias durante la estación de crecimiento parece tener una influencia considerable en la provisión de nitrógeno de los suelos. Se registran considerables pérdidas de nitrógeno en este ambiente, cuando amplias áreas son quemadas anualmente.
    Notes: Abstract Savannas cover about 300 million hectares of South America. The soils are mainly oxisols and ultisols and their natural fertility is very low with high acidity. The natural vegetation varies in density and in the amount of biomass produced annually, which can be equal to that produced by forests in the region. Among the nitrogen-fixing micro-organisms, the only ones well-studied are Rhizobium bacteria. In managing the biomass in these areas, it is important to consider biological nitrogen-fixation as a possible source of nitrogen to replace that removed in crops. Nitrification and denitrification in these soils are intense but not well studied. The rainfall distribution during the growing season seems to have a considerable influence of the nitrogen supply to the soils. A considerable loss of nitrogen occurs in this environment when vast areas are burned annually.
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    Plant and soil 67 (1982), S. 227-239 
    ISSN: 1573-5036
    Keywords: Extension ; Inoculant production ; Latin America ; N2-fixation ; Rhizobium ; Training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Más de 60 instituciones y 100 investigadores están trabajando de la investigación con Rhizobium en América Latina. La mitad de los investigadores están localizados en Argentina y Brasil. La actividad de investigación y la aplicación de los conocimientos científicos varían ampliamente de acuerdo con los paises. Los problemas de la investigación incluyen: 1) Entrenamiento inadecuado de los investigadores y poca atención para la simbiosis Rhizobium/Leguminosas en las escuelas de Agronomía; 2) investigaciones de baja prioridad sin consideración para las necesidades más inmediatas para los agricultores tales como identificación de los factores limitantes ambientales (por ejemplo: deficiencias nutricionales), técnicas para la producción de inoculantes en pequeña escala y poco control de calidad de los inoculantes disponibles; 3) aislamiento de los investigadores e insuficiente apoyo de literatura; 4) baja interdisciplinaridad en las investigaciones (por ejemplo: en muchas instituciones los investigadores son microbiológos sin conocimientos de agronomía, o agrónomos sin entrenamiento en microbiología y 5) insuficiente diseminación de los conocimientos científicos. Los problemas de la producción y control de inoculantes incluyen: 1) las cepas empleadas en los inoculantes (nacionales o importadas) no son seleccionadas localmente; 2) poco control de calidad de los inoculantes y como resultado, inoculantes malos traen descrédito para la práctica de la inoculación, y 3) precios muy altos de los inoculantes. Los problemas de la extensión incluyen: 1) falta o deficiencia de los programas de promoción de leguminosas por las organizaciones gubernamentales, 2) poco contacto entre los investigadores y los extensionistas y 3) administradores líderes, extensionistas y agrónomos que trabajan en el campo no poseen adecuados conocimientos sobre la simbiosis Rhizobium/Leguminosas. Algunas medidas inmediatas para promover la extensión y programas de promoción de las leguminosas y/o control oficial de la calidad de los inoculates son necesarias en Argentina, Uruguay, Brasil, México y posiblemente Colombia. Perú, Venezuela, Costa Rica y Chile necesitan esfuerzos combinados dirigidos prioritariamente para promover la investigación y extensión. En Ecuador, Paraguay, Bolivia, Nicaragua, Honduras, Guatemala, República Dominicana y Panamá, la prioridad debe ser dada para la investigación. Colombia debe ser incluída en este grupo por la razón de que las instituciones nacionales deben ser fortalecidas. La tabla 2 relaciona estas prioridades con mas detalles.
    Notes: Abstract More than 60 institutions and 100 researchers were involved in Rhizobium research in 1978 in Latin America. Half of these researchers were located in Argentina and Brazil. Research activity and the application of research findings vary widely among countries. Problems that plague research include 1) inadequate training of research personnel and insufficient attention paid to the Rhizobium/Legume symbiosis at agriculture schools; 2) poorly-established research priorities that do not sufficiently weigh the immediate needs for the farmers such as the identification of limiting environmental factors (e.g. nutritional deficiencies), techniques for smallscale inoculant production, and quality control of available inoculants; 3) isolation of the researchers and a lack of adequate library support; 4) poorly integrated research teams (e.g. in many institutes researchers are either microbiologists with no agricultural background or agronomists lacking microbiological training); and 5) insufficient dissemination of research findings. Problems with inoculant production and control include 1) a local dependence on national or imported inoculants rather than on locally-selected strains, 2) poor inoculant quality control which results in low inoculation success rates and subsequent discredit to the inoculation practice, and 3) high prices for inoculants. Extension problems include 1) lacking or deficient legume-promotion programs by government agencies, 2) poor contact between research and extension workers, and 3) administrators, leaders, extension workers and agronomists working in the field that lack adequate knowledge of the Rhizobium/Legume symbiosis. Immediate measures to foster extension and legume promotion programs and informal and/or official quality control are needed in Argentina, Uruguay, Brazil, Mexico, and probably Colombia. Countries where combined efforts should primarily be directed toward stimulating research and extension include Peru, Venezuela, Costa Rica, and Chile. In Ecuador, Paraguay, Bolivia, Nicaragua, Honduras, Guatemala, the Dominican Republic and Panama, priority should be given to research. Colombia should also be included in this group as national research institutions need to be strengthened. Table 2 lists these priorities more fully.
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    Plant and soil 69 (1982), S. 187-197 
    ISSN: 1573-5036
    Keywords: Apple monoculture ; Phytotoxins ; Replant problem ; Rhizoplane ; Rhizosphere ; Root exudates ; Soil micro-organisms ; Soil sickness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary One of the factors giving rise to soil sickness in apple orchards is the rhizosphere microflora. The composition of the microbial coenosis in the rhizosphere changes with increasing age of the apple trees. An increase in the counts of micromycetes and actinomycetes and a decrease in bacterial counts was found in agreement with the decreasing pH of the rhizosphere soil. The presence of fluorescent pseudomonads in the rhizosphere of old apple trees was rare, but the planting of apple seedling into sick soil induced their proliferation. The relative proportion of individual genera of micromycetes changed according to the tree age; fungi of the genus Mucor were more often found in the rhizosphere of younger trees than in that of older ones while fungi of the genus Penicillium had an opposite trend. Biological tests showed that Penicillium fungi form the majority of the phytotoxic microflora. The amount of phytotoxic micromycetes was higher in ‘sick’ soil as compared with control soil in which apple trees had not been grown for at least 15 years. Higher numbers of phytotoxic micromycetes were isolated also from the rhizosphere of apple seedlings grown in ‘sick’ soil as compared with those growing in control soil. An increase in the amount of phytotoxic micromycetes in apple tree rhizosphere could be induced by mere addition of 5% (w/w) ‘sick’ soil to the soil in which apple trees were grown for the first time. By adding sterilized ‘sick’ soil, the amount of phytotoxic micromycetes in the apple seedling rhizosphere was not affected. Increased numbers of phytotoxic micromycetes affected negatively the growth of apple trees and the morphology of apple tree roots. This demonstrated the possibility of transfer of a factor participating in the etiology of soil sickness in apple orchards.
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  • 45
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    Plant and soil 69 (1982), S. 341-352 
    ISSN: 1573-5036
    Keywords: Barley ; Nitrogen fixation ; Rhizoplane ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aerobic and anaerobic N2-fixing bacteria developed in the rhizosphere of barley seedlings and exhibited N2ase activity when seedlings were grown in sterilized sand-nutrient cultures containing low levels of combined nitrogen. The source of the N2-fixing bacteria appeared to be the seed. Average daily rates up to 0.9 μmoles C2H4 h−1 g−1 dry root tissue were measured, but the intensity of the activity was affected by moisture levels and concentration of combined N in the rhizosphere. Removal and washing of the roots did not remove the activity, and roots remained active even after surface-sterilization. An unidentified aerobic N2-fixing bacterium was isolated from the rhizoplane of active barley roots. Inoculation of barley seedlings with the aerobic N2-fixing bacterium enhanced N2ase activity of excised roots 10-fold, with average rates of 0.9, 1.1 and 1.3 μmoles h−1 g−1 dry root assayed under pO2 of 0.01, 0.02 and 0.04 atm respectively. The aerobic N2-fixing bacterium also exhibited N2ase activity when inoculated into the rhizosphere of oat, rice and wheat seedlings. Microscopic observations of sterilized live and stained barley roots suggest that the aerobic N2-fixing bacterium is an endophyte which infects root tissue and metamorphoses into vesicle-like structures.
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  • 46
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    Plant and soil 72 (1983), S. 13-29 
    ISSN: 1573-5036
    Keywords: Exudation ; Lupins ; Lupinus albus L. ; Micro-organisms ; Proteoid roots ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A model predicted that the concentration profile of exudate would be less steep and its concentration values higher for larger diameter roots and that rhizosphere volume/g of root would be maximised at a particular root size for a given exudation rate. Root hairs, if active in secretion, would increase the rhizosphere volume/g of root and the substrate concentrations in it. Proteoid roots would increase the concentration of diffusing substance even further, although the rhizosphere volume per g of root may decline due to overlap effects. These effects are discussed in relation to the rate and extent of reactions between exudates and the soil.
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  • 47
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    Plant and soil 76 (1984), S. 127-137 
    ISSN: 1573-5036
    Keywords: Adenylate pool ; Biomass volume ; CO2 evolution ; Chitin ; DNA ; Electron microscopy ; Enzymes ; Fluorescent antibody ; Fumigation-respiration ; Fungi Histochemistry ; Imunofluorecence ; Jones-Mollison technique ; Microcosms ; Monoclonal antibodies ; Nitrogen ; Nutrients ; Oxygen consumption ; Phosphorus ; Phytotoxins ; Plate counts ; Rhizobium ; Rhizosphere ; Sulphur ; Xenobiotics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary There is an immense literature on biological and biochemical analyses of soils. Such analyses have revealed the enormous richness of species in soil and their vast range of metabolic potentials and ecological diversity. Accordingly, the approaches used to investigate the soil biota and its biochemistry usually have to be modified or adapted depending upon the purpose of the investigation. Studies of micro-organisms in the soil environment, are complicated because microbial cells are commonly attached to surfaces where they live side-by-side with other populations in consortia usually containing different morphological and physiological types. Such assemblages of organisms cannot be described quantitatively using cultural techniques, such as plate counts, which underestimate both cell numbers and viable biomass. The development of more powerful observational and staining techniques has improved our knowledge of the diverse morphological and biochemical composition of soil micro-communities. Such findings have been amplified at a grosser level by laboratory studies with multi-component systems (microcosms) to mimic field situations and to assess the range of biochemical potentials of microbial consortia. But despite notable advances in analytical methods we are still, with a few exceptions, unable to detect or identify those microorganisms which carry out specific biochemical transformations or determine whether particular cells are alive, dormant or dead at the time of observation. Considerable work has been done to define some of the fundamental ecological attributes of microbial assemblages in soil. Productive work on the metabolic activities of the soil microbiota, specially geochemical transformations of C, N, S and P, has been under way for more than a century. But only in more recent years have more sensitive and reproducible analytical methods become available to measure viable biomass in soil. This will enable some insight to be gained into the role that microbial biomass plays as a labile source and sink for plant nutrients.
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  • 48
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    Plant and soil 76 (1984), S. 319-337 
    ISSN: 1573-5036
    Keywords: Aggregates ; Aluminium ; Bacterial mucilage ; Binding agents ; Calcium ; Cation bridges ; Complexing agents ; Dispersion ; Electron microscopy ; Electrophoretic mobility ; Fungal hyphae ; Glues Iron ; Management Periodate ; Polysaccharides ; Rhizosphere ; Roots ; Slaking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The stability of pores and particles is essential for optimum growth of plants. Two categories of aggregates macro- (〉 250 μm) and micro- (〈250 μm) depend on organic matter for stability against disruptive forces caused by rapid wetting. Dispersion of clay particles from microaggregates is promoted by adsorption of complexing organic acids which increase the negative charge on clays. The acids are produced by plants, bacteria and fungi. However, the dispersibility of clay in microaggregates is offset by the binding action of polysaccharides, mainly mucilages produced by bacteria, but also by plant roots and fungal hyphae. The stability of microaggregates is also enhanced by multivalent cations which act as bridges between organic colloids and clays. Macroaggregates are enmeshed by plant roots, both living and decomposing, and are thus sensitive to management, and increase in number when grasses are grown and the soil is not disturbed. Lack of root growth,i.e. fallow, has the opposite effect. Various implications for management of soil structure are discussed.
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  • 49
    ISSN: 1573-5036
    Keywords: Intermediate deep water rice ; Nitrogenase ; Plant density ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogenase activity in the rhizosphere soil of intermediate deep water rice was investigated employing gas chromatographic acetylene reduction assay. A raise in the plant density decreased the rhizosphere nitrogenase. Moreover, nitrogen fixation in the rhizosphere soil varied among the three rice varieties under intermediate deep water situations. Results indicate that nitrogen fixation is affected by plant density and the rice variety.
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    Plant and soil 78 (1984), S. 445-448 
    ISSN: 1573-5036
    Keywords: Leucaena ; Rhizobium ; VA mycorrhiza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Response ofLeucanea leucocephala to inoculation withGlomus fasciculatum and/or Rhizobium was studied in a phosphorus deficient unsterile soil.G. fasciculatum only inoculation improved nodulation by native rhizobia and Rhizobium only treatment improved colonization of roots by native mycorrhizal fungi. Dual inoculation with both the organisms improved nodulation, mycorrhizal colonization, dry weight, nitrogen and phosphorus content of the plants compared to single inoculation with either organism.
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    Plant and soil 78 (1984), S. 381-391 
    ISSN: 1573-5036
    Keywords: Aluminium ; Caloium ; Nodulation ; pH Phosphate ; Polymeric hydrolysis ; Rhizobium ; Rhizosphere ; Root elongation ; Root hairs ; Trifolium repens ; White clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Effects of aluminium on theTrifolium repens var Huia-Rhizobium trifolii strain HP3 symbiosis were studied using an axenic solution-culture system. With, 10 μM phosphate, 50 μM aluminium reduced or inhibited root elongation at pH〈5.0, root hair formation at pH〈 5.0–5.5, and Rhizobium multiplication in the rhizosphere and nodule formation at pH〈6.0. In the absence of aluminium, root elongation and root hair formation were reduced at pH〈4.3, and Rhizobium multiplication and nodule formation were inhibited at pH〈5.0. Root hair formation was more sensitive to aluminium at pH〈5 than was root elongation. No effect of aluminium on Rhizobium multiplication and nodule formation at pH〈5 was detected because both were sensitive to pH alone. At pH 5.5 most of the aluminium changed immediately to a form which was susceptible to low-speed centrifugation, but which was detected by the aluminon method of analysis, and after 24 h a precipitate formed. the concentration of phosphate was reduced also, to approximately 1μM. Toxicity was overcome by either increasing the phosphate concentration from 10 to 50 μM, or by increasing the pH to 6.0 and the calcium, concentration to 1000μM.
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    Plant and soil 74 (1983), S. 395-406 
    ISSN: 1573-5036
    Keywords: Fix− mutants ; Fix+ revertants ; Macroptilium lathyroides ; Nitrogen fixation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Eight ineffective mutant strains were isolated from N-methyl-N'-nitro-N-nitrosoguanidine mutagenized cultures of cowpea Rhizobium strain 32H1. Strains CR1, CR2, CR3, CR4, CR5 and CR6 induced more, but smaller, nodules than the wild type. With the exception of strain CR2, these mutant strains reduced less than 1% of the amount of acetylene reduced by the wild type, in both the free-living and symbiotic assays. Strain CR2 reduced acetylene in the free-living assay but not in the symbiotic assay. Strains CR7 and CR8 responded variably (5–20% of the wild type) in free-living and symbiotic acetylene reduction assays. Nodules also varied from small white to normal-sized pink nodules. The phenotypic characteristics of the mutant strains were consistant with all leguminous plants tested and were stable upon reisolation from nodules. Fully effective revertants were selected from 4 of the ineffective mutant strains by the use of the leguminous plant,Macroptilium lathyroides. Serology, patterns of resistance to anti-bacterial agents, phage-typing, and antibiotic resistance markers were used to confirm strain identification.
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    Plant and soil 56 (1980), S. 491-494 
    ISSN: 1573-5036
    Keywords: Aeschynomene ; Azospirillum ; Rhizobium ; Stem nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Fifteen isolates of nodule bacteria were isolated from root and stem nodules ofAeschynomene aspera and they were characterized as Rhizobium by well known laboratory tests. All these isolates together with other efficient strains of known rhizobia belonging to different cross-inoculation groups were evaluated for their nodulation abilities onAeschynomene aspera, Cajanus cajan (pigeon pea),Cicer arietinum (chickpea),Pisum sativum (pea),Trifolium repens (clover),Medicago sativa (lucerne),Lens culinaris (lentil),Glycine max (soybean),Vigna sinensis (cowpea),Vigna radiata (mung bean),Vigna mungo (urd bean) andArachis hypogea (peanut). The results demonstrated that Rhizobium fromAeschynomene could form nodules only on its homologous host (Aeschynomene) but not on other legumes tested. Secondly, none of the rhizobia of other cross-inoculation groups could nodulateA. aspera.
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  • 54
    ISSN: 1573-5036
    Keywords: Downy mildew ; Microflora ; Phyllosphere ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Analysis of phyllosphere microflora showed that in the resistant cultivar (PHB-14) there was a significantly higher population of fungi, gram positive and gram negative bacteria, compared to susceptible cultivar (NHB-3) under healthy and diseased situations. The cultivars during earhead stage supported maximum phyllosphere fungal and gram negative bacterial populations. The rhizosphere of the susceptible cultivar under downy mildew influence supported maximum fungal and gram negative bacterial populations and the rhizosphere effect was the highest in downy mildew colonized susceptible NHB-3 at the earhead stage (95 days after planting). Among the fungi isolated Cladosporium dominated the phyllosphere of resistant, susceptible and susceptible cultivar under the influence of downy mildew. Among the rhizosphere microflora the population ofAspergillus sp. was found to be greatest in resistant, susceptible and the susceptible cultivar under the influence of downy mildew.
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    Plant and soil 61 (1981), S. 71-80 
    ISSN: 1573-5036
    Keywords: Ecology ; Fluorescent antibody ; Immunofluorescence ; Rhizobium japonicum ; Rhizosphere ; Root surfaces ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Populations of nativeRhizobium japonicum 123 in the rhizospheres of field and pot grown plants as determined by immunofluorescence were calculated on the basis of root surface area. The density ofR. japonicum 123 on the root fluctuated between a few hundred to over a thousand per square centimeter of root surface. As root volume expanded rapidly, the Rhizobium density fell to less than one hundred per unit area. There was no appreciable effect due to different plant, nitrogen amendment, or addition of another strain ofR. japonicum, on the surface density of the nativeR. japonicum population on roots. Nor did the native population influence the added strain. Direct examination of root surface segments revealed that naturalized rhizobia existed sparsely on root surfaces in the form of short rods. They were observed to be attached sideways or in a polar manner on root hairs, epidermal cells, and at junctions of tap and lateral roots. There was no evidence of specific stimulation of the homologous Rhizobium by the host plant as a prelude to nodulation.
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  • 56
    ISSN: 1573-5036
    Keywords: Gene centre ; Genetic variability ; Pisum sativum ecotype fulvum ; Rhizobium ; Symbiotic nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pisum sativum ecotype fulvum forms ineffective nodules with Rhizobium strains, isolated from effective nodules of the cultivated pea in Europe. Rhizobium strains isolated from nodules of fulvum peas in Israel are fully effective on this host plant, but in association with the cultivated pea they induce nodules of poor N2-fixing activity. The distribution of these fulvum-specific Rhizobium strains is restricted to regions where the fulvum pea occurs naturally. Rhizobium strains from other geographical regions induce mainly ineffective, or partially effective nodules on fulvum plants. A wide genetic variation, with regard to symbiotic response to a standard set of Rhizobium strains, was demonstrated in the fulvum plants collected in Israel. Based on variation in N2-fixation three groups of plants can be distinguished. These plants offer the possibility for the study of host-genetic control on symbiotic nitrogen fixation.
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  • 57
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    Plant and soil 62 (1981), S. 169-182 
    ISSN: 1573-5036
    Keywords: Antagonism ; Fallow period ; Inoculum potential ; Non-host plant ; Rhizosphere ; Root exudate ; Soil amendment ; Survival ; Tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Studies on the survival ofPseudomonas solanacearum, the causal agent of bacterial wilt of tomato, under laboratory conditions showed that soil amendments had little effect on the population of the pathogen. When the host plant was grown in amended soil there was a positive influence on growth of the pathogen. The population level of the pathogen incorporated into the soil was reduced to one-half within a period of 46 days. The pathogen survived in the rhizosphere of non-host plants belonging to the families Acanthaceae and Leguminosae even in the absence of the natural hosts, but its incidence in the rhizosphere of plants belonging to Graminae and Cyperaceae was comparatively low indicating possibilities of reducing the inoculum potential of the pathogen in tomato fields by allowing such plants to grow during fallow periods.
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  • 58
    ISSN: 1573-5036
    Keywords: Azotobacter ; Glycine max ; Nodulation ; Rhizobium ; Trifolium repens ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Azotobacter vinelandii strains caused the formation of increased numbers of root nodules onGlycine max, Vigna unguiculata andTrifolium repens by their respective rhizobial symbionts. Increased nodulation due to inoculation withA. vinelandii also occurred in field grownG. max. Mutant strains ofA. vinelandii unable to fix nitrogen caused nodulation increases comparable to those caused by nitrogen-fixing strains. This indicates that nitrogen fixation byA. vinelandii was not responsible for the enhanced nodulation. The effect ofA. vinelandii on nodulation was greatest when cells from the mid-exponential phase of growth were applied as inoculants. Non viable cell preparations ofAzotobacter vinelandii were also found to cause an increase in the number of root nodules formed onGlycine max Rhizobium japonicum under greenhouse conditions. The nodulation enhancement activity was influenced by the method chosen to kill theA. vinelandii cells. Heat treatment and treatment with lethal levels of streptomycin destroyed the activity, whereas the activity was unaffected by ultraviolet-light treatment of the cells. Cell-free extracts ofA. vinelandii were found to enhance nodulation. On the other hand, culture supernatants ofA. vinelandii had no effect on nodulation. A split-root experiment suggested that the agent(s) responsible for the increased nodulation was not translocatable throughout the plant. The results suggest a non-excretable protein, produced byA. vinelandii, as a possible mechanism for nodulation enhancement.
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    Plant and soil 63 (1981), S. 123-129 
    ISSN: 1573-5036
    Keywords: Glass wall method ; Observation chamber ; Rhizosphere ; Root dynamics ; Savanna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A relatively small, low cost root observation chamber of steel construction has been designed for replicated use in a natural plant community. An undisturbed soil profile, suitable for detailed study can be obtained by avoiding conventional backfilling methods and despite such factors as the recognized need for teh chamber roof to be below ground level. Installation procedure emphasizes preparation of the observation face in established woody plant communities. The technique incorporates microscopic study of roots and simultaneous recording of major soil climatic factors.
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  • 60
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    Plant and soil 65 (1982), S. 133-135 
    ISSN: 1573-5036
    Keywords: Green gram ; Nitrogenase-activity ; Pathogenesis ; Rhizobium ; Rhizoctonia ; Specific activity ; Symbiosis ; Vigna radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A pot experiment, using cowpea Rhizobium and one percent inoculum ofRhizoctonia botaticola (Taub.) Butler was carried out on green gram (Vigna radiata cv. PS 16) to study the interaction between symbiosis and root rot in terms of plant growth and nitrogen fixation. The microtomy of the infected roots showed distortion of the outer layers of root as a possible cause for antagonistic interaction of these two bio-processes.
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  • 61
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    Plant and soil 66 (1982), S. 413-416 
    ISSN: 1573-5036
    Keywords: Growth ; Nematicide ; Nitrogen fixation ; Nodulation ; Peanut ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of two granular nematicidesviz. oxamyl and fenamiphos, on the nodulation and growth of Rhizobium inoculatedArachis hypogaea L. was studied in glasshouse and field trials. In the glasshouse trial at the suggested rates of application shoot fresh weight was significantly reduced by oxamyl whilst root fresh weight was similarly affected by fenamiphos. In the field trial vegetative growth and plant emergence were significantly reduced by both nematicides. Nodulation at the higher rates of application was increased by both oxamyl and fenamiphos whilst oxamyl caused a significant increase in pod number at the highest rate of application.
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  • 62
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    Plant and soil 66 (1982), S. 439-442 
    ISSN: 1573-5036
    Keywords: N2-fixation ; Nodulation ; Rhizobium ; Soybean ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of mineral nitrogen on establishment and activity of symbioses between soybean and several strains ofRhizobium japonicum and on the establishment of nodules ofR. japonicum isolated from nodules of field crops is studied. All strains were highly susceptible to the effects of 200 ppm NO3−N on the establishment of symbiosis; 50 ppm NO3−N had little effect. Response of symbioses establishhed in the absence of mineral N to short term exposure to nitrate or ammonium varied significantly between strains. Nodule isolates from soybean crops growing in nitrifying soil were no less susceptible to the inhibitory effects of mineral N on nodule formation than a laboratory culture of the commercial inoculant strain.
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  • 63
    ISSN: 1573-5036
    Keywords: Glycine max ; Iron deficiency ; Mycorrhizae ; Nodulation ; Platte ; Valley ; Yellows ; Rhizobium ; Soybeans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A chlorotic condition of soybeans in the river valleys of eastern Nebraska was studied. The pattern of chlorosis, presence of petiolar necrosis, reductions in rhizobial and mycorrhizal infection, and plant and soil chemical analyses suggest that the condition is more complex than normal iron deficiency chlorosis or other mineral deficiencies or toxicities. Nodulation is almost totally inhibited in affected plants. Mycorrhizal fungi, while able to infect early in the season, do not persist on affected plants. Breakdown of endodermis was observed in the roots of affected plants. The factors contributing to this condition have not yet been determined.
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  • 64
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    Plant and soil 68 (1982), S. 391-394 
    ISSN: 1573-5036
    Keywords: Concentration gradients ; Rhizosphere ; Soil-root interface ; Soil slicing method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A method is described for the determination of concentration gradients in the vicinity of plant roots. Plants are grown in small containers in which the roots are separated from the soil by a screen of nylon cloth. Root hairs but not roots penetrate the screen into the soil. In order to investigate the rhizospheric soil, the soil is frozen by liquid nitrogen and sliced into layers about 0.06 mm thick by means of a refrigerated microtome.
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  • 65
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    Plant and soil 69 (1982), S. 163-169 
    ISSN: 1573-5036
    Keywords: Biodegradation ; Catechin ; p-Hydroxybenzoate ; Oxidation ; Rhizobium ; Salicylate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The ability of rhizobia to utilize catechol, protocatechuic acid, salicylic acid, p-hydroxybenzoic acid and catechin was investigated. The degradation pathway of p-hydroxybenzoate byRhizobium japonicum, R. phaseoli, R. leguminosarum, R. trifolii andRhizobium sp. isolated from bean was also studied.R. leguminosarum, R. phaseoli andR. trifolii metabolized p-hydroxybenzoate to protocatechuate which was cleaved by protocatechuate 3,4-dioxygenasevia ortho pathway.R. japonicum degraded p-hydroxybenzoate to catechol which was cleaved by catechol 1,2-dioxygenase.Rhizobium sp., a bean isolate, dissimilatedp-hydroxybenzoate to salicylate. Salicylate was converted to gentisic acid prior to ring cleavage. The rhizobia convertedp-hydroxybenzoate to Rothera positive substance. Catechol and protocatechuic acid were directly cleaved by the species.R. japonicum converted catechin to protocatechuic acid.
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  • 66
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    Plant and soil 71 (1983), S. 445-454 
    ISSN: 1573-5036
    Keywords: Clay type ; CEC ; Douglas-fir ; Hebeloma crustuliniforme ; Mycorrhizas ; Nitrogen Phosphorus ; Pseudotsuga menziesii ; Rhizosphere ; pH ; Root-soil interface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In a greenhouse pot study, mycorrhizal and non-mycorrhizal Douglas-fir seedling were grown in a forest soil amended with clays and ammonium or nitrate fertilizer. Mycorrhizal seedlings grew taller, increased root and shoot dry weight more, and accumulated more nitrogen and phosphorus than non-mycorrhizal seedlings. Mycorrhizal effects were most pronounced in the nitrate treatment. Ammonium enhancement of phosphorus uptake was demonstrated for both mycorrhizal and control seedlings. Rhizosphere pH was altered by nitrogen source and the presence of mycorrhizas. Ammonium fertilization decreased pH, while nitrate fertilization increased pH.
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  • 67
    ISSN: 1573-5036
    Keywords: Competition ; Inoculum potential ; Nodulation ; Rhizobium growth rates ; Rhizosphere ; Temperature ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The competition between slow- and fast-growing types of rhizobia for nodulation of cowpeas was studied using modified Leonard-jars. Rhizosphere populations of Rhizobium, mixed and pure populations, were examined on cowpea plants grown in large glass tubes. At 25°C and at a low level of inoculation, the fast-growing strain, NGR 234, dominated the rhizosphere but at 30°C, the slow-growing strain CB 756 dominated or was equally represented depending on its initial level in the mixed inoculum. At 25°C/23°C (day/night), the fast-growing strain from Lablab (NGR 234) was a superior competitor for nodule sites compared with three slow-growing strains of Rhizobium. When plants were grown at 30°/26°C, the slow-growing rhizobia were the better competitors for host nodulation. Fast-growing strains from Mimosa and Leucaena were poor competiors at both temperatures. The results were influenced by the proportions of the competing strains, as well as the total numbers of rhizobia, in the mixed inoculum. Other factors, including ‘host preferences’, host compatibility and time taken for nodule initiation, also contributed to the relative success of competing strains. The results reflect the persistent isolation in tropical regions of slow-growing cowpea-type of rhizobia from most tropical legumes. Dual occupancy of nodules by both fast- and slow-growing rhizobia occurred in 0–15% of the nodules formed for most paired inocula. However, the fast-growing Leucaena isolate NGR 14/1 was present in 73 to 83% of the nodules formed by the slow-grower CB 756.
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  • 68
    ISSN: 1573-5036
    Keywords: Acetylene ; CO inhibition ; Conversion ratio C2H4/N2 ; Effect oxygen ; Hydrogen evolution ; 15N2 fixation ; δ15N measurements ; Parasponia parviflora ; Relative efficiency nitrogen fixation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Isotopic15N2 experiments confirmed nitrogen fixation inParasponia parviflora. The conversion ratio C2H4/N2 was 6.7 under the experimental conditions employed. Measurements of the δ15N in leaves of Parasponia and Trema showed on the basis of these determinations thatParasponia parviflora possesses N2-fixing capacity and can be distinguished in this respect from the non-nitrogen-fixingTrema cannabina tested by the same method. Therefore, δ15N can be used to monitor N2 fixation in natural ecosystems. Hydrogen evolution and the relative efficiency of N2 fixation in this relation have been determined. DetachedParasponia parviflora root nodules grown in soil and tested in an argon/oxygen atmosphere produced appr. 4 μmol H2.h−1.g−1 fresh weight root nodules. The relative efficiency of hydrogen utilization as measured in argon, air, and in the presence of C2H2 10% (v/v) was for both equations $$\left( {1 - \frac{{H_2 (air)}}{{H_2 (Ar)}}} \right) and \left( {1 - \frac{{H_2 (air)}}{{C_2 H_2 }}} \right)$$ used for to express this efficiency 0.96 and 0.97, respectively. This indicates that Parasponia like the root nodules of some actinorhizal symbioses (Alnus, Myrica, Elaeagnus) and some tropical legumes (Vigna sinensis) has evolved mechanisms of minimizing net hydrogen production in air, thus increasing the efficiency of electron transfer to nitrogen. The oxygen relation of nitrogen fixation (C2H2) inParasponia parviflora root nodules was determined. The nitrogenase activity of Parasponia root nodules increased at increasing oxygen concentrations up till c. 40% O2. At oxygen levels above 40% O2, the nitrogenase activity of the root nodules was nil or very erratic suggesting that at these oxygen levels the nitrogenase is not longer protected against the harmful effect of oxygen. In this respect Parasponia root nodules differ from actinorhizal root nodules in other nonlegumes, where optimal nitrogenase activity was observed in the range of 12–25% oxygen. Respiration experiments with Parasponia root nodules showed that in the range 10, 20, and 40% oxygen, the respiration rate (CO2 evolution) increased concomitantly with an increase of the acetylene reduction rate. The CO2/C2H4 values obtained varied between 8.1 and 19.2, being therefore 2–3 times higher than similar estimations in some actinorhizal and legume root nodules. The respiratory quotient (RQ) of detachedParasponia parviflora root nodules was in air initially approximately 2.0, but this value dropped to about 1.0 in a 3-hours period.
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  • 69
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    Plant and soil 76 (1984), S. 307-318 
    ISSN: 1573-5036
    Keywords: Autochthonous ; Biomass ; Cultivation ; Inoculation ; Lignocelluloses ; Polysaccharides ; Rhizosphere ; Soil stability ; Soil structure ; Zymogenous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An inherent (autochthonous) biomass is characteristic of a soil while the input of substrates for plant roots or crop residues promotes the transient (zymogenous) biomass. However successful micro-organisms will show aspects of both types of ecological strategy. The biomass generated from plant residue substrates can include toxin-producing and pathogenic species but also beneficial organisms such as N-fixers and polysaccharide-producers. Rhizosphere activity can, depending on soil, plant and microbial species, stabilize or destabilize soils. Microbial activity should be considered in soil management and it may be possible to manipulate the soil population balance towards beneficial organisms.
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  • 70
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    Plant and soil 76 (1984), S. 379-387 
    ISSN: 1573-5036
    Keywords: Actinomycetes ; Bacteria ; Chernozemic soil ; Fungi ; Rhizosphere ; Trifluralin herbicide ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study examined the effects of trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), a soil incorporated herbicide, on soil microflora both in the general soil environment and in the rhizosphere of trifluralin damaged wheat roots. Two Dark Brown Chernozemic soils were treated with various trifluralin rates in the growth chamber and wheat [Triticum aestivum L. ‘Neepawa’] was seeded. Trifluralin generally had no effect on fungi, bacteria, or actinomycete populations in either the general soil or in the rhizosphere. CO2 evolution was unchanged when trifluralin was added to the soil. In wheat plots, at two field locations, there were no significant effects of trifluralin (1.0 kg ha−1) on soil fungi, bacteria, actinomycete, denitrifying bacteria, and nitrifying Nitrobacter propulations. A pure culture study with 42 soil microorganisms showed that many isolates were inhibited at 400 to 100,000 μg g−1 but not at concentrations 〈16 μg g−1. Similar data were obtained from tests on four different soils. These studies indicate that trifluralin is unlikely to cause changes in the numbers of soil microorganisms when used at recommended levels.
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  • 71
    ISSN: 1573-5036
    Keywords: Hill soils ; Lime ; Mycorrhiza ; Nitrogen fixation ; Nodulation ; Phosphorus ; Rhizobium ; Symbioses ; White clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The responses of white clover (cv NZ Grasslands Huia grown in four UK hill soil types) to additions of lime and P, to inoculation with Rhizobium and mycorrhizal fungi, and to differences in soil water status were assessed in pot and field experiments. With a deep peat soil in pots, shoot production, nodulation and N fixation by clover were increased by 160, 130 and 85% respectively following inoculation with mycorrhiza, but in the field, despite a doubling of root infection, there was no response in growth. On a brown earth soil in the field inoculation with one endophyte (Glomus mosseae L1) out of four tested depressed production of white clover shoots by 42% but enhanced that of leeks (Allium porrum) by 50%; the others were without effect. With dry peaty podzol and brown earth soils in pots, clover shoot production was highest with added P when a water holding capacity of 80% was maintained, but roots from the latter had only 2.6 compared to 68 nodules per plant from the former. Further work is required to explain poor nodulation in the brown earth soils.
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  • 72
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    Plant and soil 77 (1984), S. 387-390 
    ISSN: 1573-5036
    Keywords: Antibiosis ; Culture filtrate ; Fungi ; Peanut ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Four strains ofRhizobium sp. from peanut (Arachis hypogaea L.) root nodules were tested for their sensitivity to metabolites (culture filtrates) of more than ten common soil inhabiting fungi, in yeast extract mannitol agar and broth cultures. Among the rhizobial strains tested strain CB-530, BU-1 and BU-2 were not sensitive to metabolites ofMyrothecium roridum andFusarium moniliforme whereas CB-1024 was sensitive. Culture filtrates ofGliocladium roseum, Thielavia basicola andDrechslera pedicellata inhibited the strains CB-530 and BU-2 but not CB-1024. Most of the soil inhabiting fungi tested were inhibitory to rhizobial growthin vitro and very few were stimulatory, their effect in either case being strain specific.
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  • 73
    ISSN: 1573-5036
    Keywords: Acid soils ; Inoculant ; Rhizobium ; Soybeans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rhizobial inoculation trials were conducted in an acid heavy clay soil in Mekong Delta, Viet Nam, using peat based inoculants produced locally and the commercial granular product of Nitragin CCo., Wisconsin, USA. The pH of these soils ranged from 4.5 to 5.1. Two soybean cultivars, MTD6 and MTD10, were tested as host plants. There were no significant differences between locally made inoculant treated plants and the uninoculated controls in both cultivars. But, the Nitragin inoculation improved all plant characteristics examined in both cultivars. Grain yields of Nitragin inoculated plants of cultivar MTD6 and cultivar MTD10 were 6.5 and 5.5 times as much as those of the controls; protein content of grain increased 11 and 16 percent, respectively. Well nodulated plants had shorter life cycles, flowering durations, and days to flowering. The Rhizobium symbiosis resulted in an additional 153 kg grain-N/ha. These studies show that a surface coated commercial multistrain inoculant can be used to successfully grow soybeans in the acid, heavy clay soils of the Mekong Delta.
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  • 74
    ISSN: 1573-5036
    Keywords: Aspergillus fumigatus ; Aspergillus niger ; Aspergillus sydowi ; Capsicum annuum ; Chilli Citrulline ; Cladosporium cladosporioides ; Exudates ; Fusarium moniliforme ; Fusarium oxysporum f. sp.Capsici ; Fusarium solani ; Inhibitory ; Methionine ; Penicillium janthocitrinum d-1-β ; phenylalanine ; Rhizoplane ; Rhizosphere ; Stimulatory ; Trichoderma viride ; d-Xylose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary From root exudates of three cultivars of chilli (Capsicum annuum L.) 12 amino acids and 7 sugars were detected. Methionine, d-1-β phenylalanine, citrulline and d-xylose were detected only from the root exudates of resdistant cultivars. The root exudates of resistant variety inhibited spore germination of the pathogen (Fusarium oxysporum f. sp.capsici), but that of susceptible variety enhanced spore germiantion of the same. Spore germiantion of antagonistic fungi (Trichderma viride andAspergillus sydowi) was also influenced by the root exudates of resistant and susceptible varieties, but the influence was different. Spore germiantion of a number of rhizosphere fungi was studied and in general root exudate of susceptible cultivar enhanced spore germiantion of majority of fungi, but spore germination of antagonistic fungi against the pathogen was inhibited. However, root exudate of resistant cultivar stimulated spore germination of antagonistic fungi.
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