Nitrogen Fixation In Soybean Research Articles

Combined effects of plant growth‐promoting rhizobacteria and genistein on nitrogen fixation in soybean at suboptimal root zone temperatures

Application of plant growth‐promoting rhizobacteria (PGPR) or the plant to bacteria signal molecule genistein has been shown to increase nodulation and nitrogen (N) fixation by soybean [Glycine max (L.) Merr.] over a range of root zone temperatures (RZTs) and, specifically, off‐sets at least some of the ill‐effects of low RZTs. Two sets of controlled‐environment experiments, one on a growth bench and the other in a greenhouse, were conducted to examine the combined ability of both PGPR and genistein to reduce the negative effects of low RZT on soybean nodulation and N fixation. Each of two the PGPR strains, Serratia proteamaculans 1–102 and Serratia liquefaciens 2–68 were co‐inoculated with Bradyrhizobium japonicum USDA 110 preincubated with 17.5 (somewhat inhibitory), and 15°C (very inhibitory). At RZTs of 25 and 17.5°C PGPR strains and genistein in combination increased the number of nodules and the amount of Nn fixed. The most stimulatory effect was observed at 17.5°C for the combination: S. proteamaculans 1–102 plus B. japonicum USDA 110 pre‐incubated in 15 μM genistein under greenhouse conditions. For most treatment combinations the stimulatory effects of PGPR and genistein were additive at RZTs of 17.5 and 25°C. Surprisingly, the combination of these two factors resulted in antagonism at the very inhibitory RZT of 15°C. The results suggest that the negative effects of certain low RZTs could be more effectively off‐set by combined treatments of PGPR plus geneistin pre‐incubation of rhizobial cultures than by their individual treatment.

The Role of Growth Regulators on Nodule Senescence and Nitrogen Fixation in Soybean

The Role of Growth Regulators on Nodule Senescence and Nitrogen Fixation in Soybean

Irrigation of Secondary Sewage Effluent: Salinity and Nitrogen Effects on Growth and Nitrogen Fixation of Nodulated and Non-nodulated Soybeans.

Salinity and nitrogenous components are the most critical water qualities in secondary sewage effluent (SSE) when used as an alternative resource for agricultural irrigation water. In this study a pot experiment was conducted to investigate the effects of salinity and inorganic nitrogen in the irrigation water on the growth and nitrogen fixation of soybean (Glycinema:, (L.) Merrill) isoline T201 and T202. Nitrogen in the irrigation water as the plant nutrient contributed slightly to dry matter production because the total amount of nitrogen applied into a pot was small compared to the plant's demand for nitrogen or to the dosage of applied fertilizer nitrogen. Nitrogen in the irrigation water, however, alleviated the toxic effect of salinity on nitrogen fixation of soybean. Moderate salinity that is similar to the salinity of SSE from the city sewage disposal plant slightly affected nitrogen l1xation and reduced dry matter production. Sever salinity water ~ith electroconductivity of 270 mS/m greatly reduced both growth and nitrogen fixation. We should pay more attention to salinity as the water quality of SSE rather than nitrogen components when SSE is reclaimed and used as irrigation water in upland fields.

The Earlyenod2 and the Leghemoglobin (lbc3) Genes Segregate Independently from Other Known Soybean Symbiotic Genes

Recombinant inbred lines (RILs) as well as an F2segregating population of soybean Glycine max facilitated the mapping of two expressed sequence tags involved in early nodulation and subsequent nitrogen fixation in soybean. For the early nodulin gene enod2, the parents of RILs, Minsoy and Noir1, showed a polymorphism (5.5 vs 5.9 kb) after EcoRV digestion. Restriction fragment length polymorphism (RFLP) patterns of 42 RILs were analyzed with the MAPMAKER program, linking enod2 to the seed coat color gene, I, with a distance of 11.1 cM on linkage group U3 of RIL map. enod2 and I are located close to Rhg4, a soybean cyst nematode resistance gene, and a locus for seed coat hardness. The molecular marker pA-110 and seed coat color were used to integrate enod2 on an F2segregating population (72 plants) generated from a cross between cv. Bragg and G. soja PI468.397. enod2 was mapped in the same order as on the RIL map but 18.5 cM from the I locus on the TN map. A microsatellite from the 5′ region of enod2b was mapped in the same position, demonstrating that enod2b and not enod2a was mapped. An RFLP for lbc3 (leghemoglobin) segregated independently from enod2 and the nts-1 supernodulating locus suggesting that in soybean symbiotically significant loci (including rj1, Rj2, and rj6) are not clustered.

Effect of CO2-free air treatment on nitrogen fixation of soybeans inoculated with Bradyrhizobium japonicum and Rhizobium fredii

Soybean (Glycine max L. Merr.) cultivars Akisirome and Peking were inoculated with Bradyrhizobium japonicum Is-21 and Rhizobium fredii USDA 194, respectively, and were grown in cylindrical pots containing sterilized vermiculite which were aerated with CO2-free air or ambient air to study the effects of CO2 deficiency in the rhizosphere on plant growth, nodulation, and nitrogen fixation. The repressive effects of CO2-free air treatment were more conspicuous in Peking than Akisirome, and nodule number, nodule mass, amount of biologically fixed N and plant growth of Peking were reduced remarkably by the CO2-free air treatment. Acetylene reduction activity (ARA) of Peking inoculated with USDA 194 and Akisirome inoculated Is-21 was assayed in the absence and presence of CO2, ARA of Akisirome was not affected by the absence of CO2, while that of Peking decreased drastically. Based on these results, it was concluded that nitrogen fixation by Akisirome inoculated with B. japonicum Is-21 was not appreciably influenced by CO2 deficiency in the rhizosphere, while that of Peking inoculated with R. fredii USDA 194 was severely repressed, and the decrease was estimated to be due to both the reduction of the nodule mass and specific nitrogen-fixing activity.

Dual inoculation with strains of Bradyrhizobium japonicum and Azospirillum brasilense to improve growth and biological nitrogen fixation of soybean (Glycine max L.)

The effects of inoculation with Bradyrhizobium japonicum and Azospirillum brasilense strains on the growth of soybean were evaluated with regard to the estimation of N2 fixation using the 15N isotope dilution technique. Inoculation, in general, increased the dry mass of soybean as well as nitrogen content. Dual inoculation with a mixture of B. japonicum and A. brasilense strains was superior over single inoculation with B. japonicum. Nitrogen fixed (Ndfa) varied according to inoculant and soil conditions. Percentages of nitrogen derived from air (% Ndfa) using a non-nodulating isoline were 72% and 76% for B. japonicum and B. japonicum plus A. brasilense, respectively, in non-sterile soil. A similar but higher trend was recorded in sterilized soil, in which the percentages of N2 fixed were 81% and 86% for single and dual inoculation, respectively. The correlation coefficient between N2 fixed and N uptake (r=0.94) and dry mass (r=0.89) was significant. Application of special bacterial inoculants in agricultural systems of Egypt seems to be a promising technology and could be used for improving soybean growth as well as soil fertility, thus minimizing environmental pollution.

Plant Growth-promoting Rhizobacteria and Soybean [Glycine max(L.) Merr.] Growth and Physiology at Suboptimal Root Zone Temperatures

Application of plant growth-promoting rhizobacteria (PGPR) has been shown to increase legume growth and development under optimal temperature conditions, and specifically to increase nodulation and nitrogen fixation of soybean [ Glycine max (L.) Merr.] over a range of root zone temperatures (RZTs). Nine rhizobacteria applied into soybean rooting media were tested for their ability to reduce the negative effects of low RZT on soybean growth and development by improving the physiological status of the plant. Three RZTs were tested: 25, 17.5, and 15 °C. At each temperature some PGPR strains increased plant growth and development, but the stimulatory strains varied with temperature. The strains that were most stimulatory at each temperatures were as follows: 15 °C— Serratia proteamaculans 1–102; 17.5 °C— Aeromonas hydrophila P73, and 25 °C— Serratia liquefaciens 2–68. Because enhancement of plant physiological activities were detected before the onset of nitrogen fixation, these stimulatory effects can be attributed to direct stimulation of the plant by the PGPR rather than stimulation of plant growth via improvement of the nitrogen fixation symbiosis.

Reduction of Growth and Symbiotic Nitrogen Fixation in Soybean as Affected by the Site of Simulated Acid Rain Application.

Reductions of growth and symbiotic nitrogen fixation were studied in soybean exposed to simulated acid rain (SAR) applied to different sites. Soybean cultivar Okuharawase was grown in 1/5000a pots under a rain shelter. The plants were exposed to SAR from 15 days after sowing (DAS) to the flowering stage at 36 DAS. The sites of SAR application were foliage, soil and both foliage and soil, and the pH of SAR used was 2.7, 3.5, 4.5 and 7.0 (control). At the flowering stage, leaf area per plant, apparent photosynthetic rate and root dry weight per plant decreased in proportion to decrease in the pH of SAR. The degree of decrease was similar between the plants exposed to SAR in foliage and soil and those in foliage, but the application of SAR to soil alone did not cause any change in the parameters. There was a consistent reduction in the number of nodules per plant, the fresh weight of nodules per plant and the rate of symbiotic nitrogen fixation, or acetylene reduction activity (ARA) regardless of the site of SAR application. ARA decreased in proportion to the decrease in the number and fresh weight of nodules. The root dry weight significantly correlated with nodule number or nodule fresh weight. The reduction of growth and symbiotic nitrogen fixation in plants with exposure to SAR in foliage was similar to that with exposure in both foliage and soil, whereas SAR applied to soil alone suppressed modulation only.

Biomass accumulation and allocation in soybean associated with genotypic differences in tolerance of nitrogen fixation to water deficits

Nitrogen fixation in soybean (Glycine max [L.] Merr.) is more sensitive to water deficits than many physiological processes and may therefore limit yield under nonirrigated conditions. Tolerance of nitrogen fixation to water deficits has been observed in the cultivar Jackson, however, the physiological basis for this is unclear. It was hypothesized that genotypes that could continue biomass production on limited soil water would prolong nitrogen fixation by continued photosynthate allocation to nodules. An initial greenhouse experiment compared biomass and N accumulation in six genotypes over an 8 d water deficit. Low stress intensity minimized genotypic expression of water-deficit tolerance; nevertheless, Jackson was clearly one of the most tolerant genotypes. In a second experiment, Jackson was compared to SCE82-303 at more severe stress levels. Biomass and N accumulation continued during water deficits for Jackson but ceased in SCE82-303. Individual nodule mass tended to increase during water deficits in Jackson and tended to decrease in SCE82-303, indicating greater allocation of photosynthate to Jackson's nodules in response to water deficits. Biomass accumulation of Jackson was contrasted with the USDA plant introduction (PI) 416937, which also has demonstrated tolerance to water deficits. For water-deficit treatments, total biomass accumulation was negligible for PI416937, but biomass accumulation continued at approximately 64% of the control treatment for Jackson. Transpirational losses for Jackson and PI416937 were approximately the same for the water-deficit treatment, indicating that Jackson had higher water use efficiency (WUE). Isotopic discrimination of 13C relative to12 C also indicated that Jackson had superior WUE during water deficits. Carbon-14 allocation in Jackson was compared to KS4895, a cultivar that was identified as sensitive to water deficits in an initial experiment. The comparison of water-deficit treatments of Jackson with KS4895 indicated that Jackson exported significantly greater amounts of14 C from labeled leaves and allocated approximately four times greater amounts of 14C per g of nodule. Results indicated that Jackson's sustained biomass production during water deficits resulted in the continued allocation of photosynthate to nodules and prolonged nitrogenase activity.

Possible causes of the physiological decline in soybean nitrogen fixation in the presence of nitrate

Nodulated soybean plants (Glycine max (L.) Merr. cv. Clarke) were supplied with 10 mol m-3 nitrate at the vegetative stage. This treatment caused a rapid decline in nitrogen fixation (acetylene reduction) activity and a consequent decline in ureides in the xylem sap. However, there was virtually no effect on the nitrogenase complex, according to Western blots against components 1 and 2. The effect on nitrogen fixation was matched by a decrease in nitrogenase-linked respiration and increases in nodule oxygen diffusion resistance and the carbon cost of nitrogen fixation. The addition of nitrate had little effect on protein content from either nodule plant or bacteroid fractions. Activities of nitrate reductase (NR) and nitrite reductase (NiR) from either the plant fraction or the bacteroids were affected in different ways during 8 d of NO3- supply. Nodule plant NR and bacteroid NiR were not affected. However, nodule plant NiR increased 5-fold within 2 d of supplying NO3- Bacteroid NR only increased after 6 d. These results could be interpreted in terms of a restricted nitrate access into the infected region of nodules. However, denitrification was detected within 2 d of nitrate supply in soybean nodules. The results are discussed in relation to possible causes of the nitrate-induced decline in nitrogenase activity.

Growth, nodulation and nitrogen fixation in soybean as affected by air humidity and root temperature

Growth, nodulation and N2 fixation inGlycine max L. Merr., cv. Biison as affected by the relative humidity of air (RH) during the dark period (95 or 50 – 65 %) and day/night root temperature (Tr) (28/28, 25/25, 18/18, 22/28, 22/18 °C) were studied. The growth parameters (plant fresh and dry mass, yield), nodulation (nodule number and fresh mass) and N2 fixation abilities (total nitrogen content, nitrogenase activity) increased significantly with the increasing Tr. In addition, at the same Tr during the day all studied parameters were increased at the higher Tr during the dark period. Growth, nodulation and N2 fixation were significantly enhanced at low RH. The findings indicate that all studied parameters could be regulated by environmental factors during the dark period.

5518583 Zero discharge mill distillation, salt recovery, and water management: Nykanen Tuomo S; Greenwood Brian F; Gullichsen Joha; KiiskilaErkk; Mattelmaki Esko; Phillips Joseph R; Richardsen Jan T; Ryham Rolf; Soderman Jarmo; Wiklund Karl G, Glens Falls, NY, United States assigned to A Ahlstrom Corporation

The environmental impact of hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) are under intense study due to the resistance of the breakdown product, trifluoroacetic acid (TFA), to further degradation. TFA has come under scrutiny due to its rapid and complete partitioning into aqueous phases of the environment, eventually allowing for deposition of TFA into soil via precipitation. Evidence exists that TFA may be toxic to soil microbes and plants, with little or no degradation occurring in soils. Uptake by plants and microorganisms and its similarity to acetate, implies its potential to effect the symbiotic nitrogen-fixing partners Bradyrhizobium japonicum and soybean (Glycine max). A preliminary study was performed in accordance with the Alternative Fluorocarbon Environmental Acceptability Study (AFEAS). Those results are presented here in addition to the findings of further experimentation on the initial interaction of B. japonicum with soybean. We used three levels of TFA (0.67, 6.74 and 67.40 μl TFA kg−1 soil; 0.003, 0.031 and 0.314 μl TFA l−1) for soil and hydroponics conditions and three levels (10, 100 μM and 1 mM) in bacterial culture. The results demonstrate that TFA affects growth of B. japonicum significantly, but does not affect PHB accumulation. Also no F− was found in cultures grown on TFA. Attachment of B. japonicum to soybean roots was enhanced with the lowest level of acetate or TFA and was significantly reduced with 1 mM acetate or TFA. Cultures grown on acetate or acetate with TFA do not attach well, with those grown with 1 mM TFA the least. Both effects may be attributed to pH. Soybean seedlings had significantly retarded development with levels of TFA at or above 6.74 μl TFA kg−1 soil and 0.031 μl TFA l−1 nutrient solution. No nodules formed on those plants treated with these levels of TFA except in the hydroponics trials. Nodule location was not affected regardless of the TFA level. At the lowest level used we found no effects on soybean or symbiotic nitrogen fixation. In some cases, nodulation was enhanced, but nodule weight reduced. Anaerobically isolated bacteroids had normal levels of acetylene reduction activity regardless of the level of TFA used. In summary, soybean is much more sensitive to low levels of TFA than its symbiotic counterpart B. japonicum. No detrimental effects on symbiotic nitrogen fixation in soybean should be expected unless large bioaccumulation of TFA occurs in agricultural areas.

Phenology, growth, and yield of field-grown soybean and bush bean as a function of varying modes of N nutrition

In field trials conducted at four sites in Hawaii, soybean ( Glycine max) and bush bean ( Phaseolus vulgaris) were either inoculated with homologous rhizobia, fertilized at high rates with urea, or left unamended. Crop phenology was assessed every few days. Rates of biomass and N accumulation and components of yield were measured five times during each crop cycle to assess the extent to which: (i) crops relying on soil, symbiotic, or fertilizer N differed in their growth characteristics; (ii) mode of N nutrition affected the timing of developmental stages; and (iii) effects of N nutrition on crop growth and development were related to final yield. While all measured variables differed significantly between sites, the effect of changing N source on these variables, in N limited environments, was consistent across sites. Rate and extent of node production, crop growth and yield were increased in symbiotic and N-fertilized crops as compared to unamended, non-fixing crops, while reproductive development was protracted. Extended time required to reach reproductive maturity was attributable to an increase in seed fill duration as time to flowering was not affected. Development and yield of N 2-fixing crops were similar but not equivalent to those of N-fertilized crops. To produce reliable yield estimates, legume growth simulation models must be able to accurately simulate crop growth and phenology. The present data indicate that information relating to source and supply of N must be incorporated before such models can be used to generate reliable yield estimations. Results of these trials also provide a valuable dataset for calibrating model subroutines for inorganic nitrogen uptake and nitrogen fixation in soybean and bush bean growth under field conditions and adjusting model coefficients for tropical environments.

Effect of Water Regimes and Moisture Stress at Different Growth Stages on Nodule Dynamics, Nitrogenase Activity and Nitrogen Fixation in Soybean (Glycine max (L.) Merrill)*

AbstractThe effect of water regimes and soil moisture stress on total nodule number, effective nodule number, nodule dry weight, nitrogenase activity and nitrogen fixation in soybean was studied. The effective nodule number, nodule weight, nitrogenase activity and nitrogen fixation increased due to increase in water regimes from 0.4 to 0.6 Cumulative Pan Evaporation (CPE). The stress during either flowering or pod filling reduced the effective nodule number, nodule weight, nitrogenase activity and nitrogen fixation. The amount of nitrogen fixed was maximum with 0.8 CPE (50.09 kg ha‐1 season‐1) followed by 0.6 CPE (42.08 kg ha‐1 season‐1) and 0.4 CPE (33.04 kg ha‐1 season‐1). The amount of nitrogen fixed was reduced by 17.71 % and 26.39 % due to stress during flowering and pod filling respectively compared to normal irrigation.

Soybean nitrogen fixation and growth as affected by drought stress and potassium fertilization

Abstract Several studies have identified drought stress as having particularly deleterious effects on symbiotic nitrogen fixation activity in soybean. Potassium is important in the growth of soybean and an important ion in the physiology of plant water relations. Therefore, this study was undertaken to examine the interactive effects of various levels of potassium and water in the soil on the nitrogen fixation activity of soybean. The experiment was done under greenhouse conditions to provide the plants with well‐defined levels of potassium and to control the soil water availability. No difference in vegetative growth or acetylene reductions rates was detected among the potassium treatments. However, seed yield showed an optimum for the middle potassium treatment (50 mg K2O/kg soil) and the total accumulated nitrogen was lowest for the highest potassium treatment. As expected, dramatic differences as a result of the drought treatments were detected in nitrogen fixation rates and plant growth. Overall, the...

Shoot-root control of nitrate tolerance of N2 fixation in spontaneously tolerant soybean lines: reciprocal grafting experiments

Summary — A characterization of spontaneous nitrate tolerance of nitrogen fixation in soybean was carried out by means of 2 reciprocal grafting experiments, with a top cross and a diallel type design. Shoot-root control of nitrate tolerance was studied in a spontaneous tolerant line (Tielingbaime), a non-tolerant cv (Kingsoy), and 5 progeny lines derived from their cross. Both experiments demonstrated a shoot control for nitrate tolerance of nodulation. Nitrate tolerance was expressed as the maintenance of a higher number and a greater specific mass of nodules in the presence of nitrate. Regulation of nitrogen fixation in the presence of nitrate also seemed to be related to shoot factors. However, diallel analysis of reciprocal grafts indicated that interaction effects with root control could not be excluded for this trait.

Photosynthesis and Nitrogen Fixation in Soybean Exposed to Nitrogen Dioxide and Carbon Dioxide

Abstract‘Williams‐82’ Soybean [Glycine max (L.) Merr.] plants, at the flowering stage, were exposed to NO2 (0.1 µmol mol−1, 7 h d−1) and CO2 (450 µmol mol−1, 12 h d−1) for 5 d singly and in combination in open‐top field chambers. The rate of photosynthesis (PN), specific root nodule nitrogenase activity (SNA), and leaf N were measured after exposure using the LICOR 6200 Portable Photosynthesis system, the acetylene‐ethylene reduction method, and the Kjeldahl digestion, respectively. The plants exposed to NO2 (with 350 µmol mol−1 CO2) showed significantly higher PN, SNA, and N compared with the control plants. The SNA and N were reduced, with no change in PN on exposing the plants to CO2 (in the absence of NO2). When the plants were exposed to a combination of these two gases, SNA was increased but the PN and N did not change. The stimulatory effect of NO2 was reduced by the inhibitory impact of CO2 on the parameters studied.

Sewage sludge effects on growth and nitrogen fixation of soybean

Previous studies on the effects of sewage sludge on the growth of soybeans ( Glycine max L. Merr.) have failed to resolve whether land application is an acceptable practice. To study this problem, two sludges were incorporated into soil at four rates (based upon the N requirement of the crop, i.e. 0, 78, 156, and 312 kg available N ha −1)_and at two locations. The growth, nodulation, and nitrogen fixation of soybeans were monitored. Although the electrical conductivity (EC) of the soil, which is an indication of the soluble salt content, was increased immediately after addition of the sludge, no long-lasting, adverse effects on plant growth were noted. When the EC of soil was determined at harvest, it had declined to background levels for all treatments. Although the microsymbiont of soybean ( Bradyrhizobium japonicum) is relatively sensitive to the toxic effects of soluble salts, nodulation was not affected by the application of the highest rate of sludge. In the first year, the sludge significantly increased the foliar N content of the crop. The rate of nitrogen fixation was inversely related to the amount of sludge-borne N added to soil. At the highest rate of sludge addition, N fixation provided approximately 14% of total plant N with approximately 50% of total foliar N obtained from fixation at the control rate. When the same parameters were measured during the second year, sludge application had no significant effect on any of the parameters examined. These results indicate that the application of sewage sludge to land cultivated to soybeans may be an acceptable practice.

Potential for increasing biological nitrogen fixation in soybean

Potential for increasing biological nitrogen fixation in soybean

Nitrogen Fixation in Soybean Treated with Nitrogen Dioxide and Molybdenum

AbstractSoybean plants were treated with Mo (0.0 or 2.0 mg kg−1, soil dry wt.) and exposed to NO2 (0.0, 0.05, or 0.1 µmol mol−1) at flowering stage. Specific root nodule activity (SNA), chlorophyll‐a (Ch‐a), chlorophyll‐b (Ch‐b), leaf N, number of pods, seeds per pod, weight of seeds, and shoot dry weight were measured. Compared with control, SNA did not change on the addition of 2 mg Mo to the soil, but increased by 65% on exposure to 0.1 µmol mol−1 NO2 and by 106% on treatment with both NO2 and Mo. Both Ch‐a and Ch‐b increased significantly on exposure to 0.1 µmol mol−1 NO2 and the amount of this increase with 0.05 µmol mol−1 NO2 and 2 mg MO was almost the same as with 0.1 µmol mol−1 NO2 alone. Leaf‐N increased by 46% on exposure to NO2 but did not change on the addition of Mo. Pod number, seed number and weight, and shoot dry weights showed significantly higher values on exposure to 0.1 µmol mol−1 NO2 and 2 mg Mo.