Nitrogen Fixation In Soybean Research Articles

Growth, nodulation, and nitrogen fixation of soybean plants with seeds treated with kasugamycin

Abstract For the purpose of using kasugamycin resistant rhizobium as an inoculum, the effects of kasugamycin on growth, nodulation, and nitrogen fixation of soybean were investigated. Differences in the kasugamycin tolerance among rhizobial strains were also studied. Seed treatment with kasugamycin at 2,500 ppm brought about a change of the leaf shape and also induced the growth suppression of plants semi-aseptically cultured in vermiculite sterilized by autoclave. On the contrary, the growth of the plants cultured in soil was not appreciably suppressed by the kasugamycin treatment. However, kasugamycin markedly affected the nodulation process. That is, the number of nodules formed on the treated plants (more than 500 ppm kasugamycin) decreased by about 50% of that of the non-treated plants. However kasugamycin did not affect significantly the nitrogen fixation of soybean plants. Nineteen Bradyrhizobium japonicum strains out of the 21 strains tested were sensitive to 1,000 ppm kasugamycin. On the contrary...

Nitrogen fixation of soybean and alfalfa on sewage sludge-amended soils

Metal uptake by growing plants varies among species. A greenhouse experiment was conducted to determine growth, heavy metal uptake and N 2 fixation of soybean ( Glycine max (L.) Merr.) and alfalfa ( Medicago sativa (L.) using two soils and two sources of sewage sludge. The municipal sludges were collected from an industrialized city and a small town with little industry, and were applied at rates of 35 and 70 Mg ha −1. The root and shoot dry weights of both alfalfa and soybean were increased by the application of limed anaerobically digested, low-metal sludge. Dinitrogen fixation, however, was not significantly affected by low-metal sludge application. Dry matter and N 2 fixation of both soybean and alfalfa were significantly decreased by the application of high-metal sludge in plants grown on both soils.

Influence of Bradyrhizobium japonicum Location and Movement on Nodulation and Nitrogen Fixation in Soybeans

The influence of seed and soil inoculation on bradyrhizobial migration, nodulation, and N(2) fixation was examined by using two Bradyrhizobium japonicum strains of contrasting effectiveness in N(2) fixation. Seed-inoculated strains formed fewer nodules on soybeans (mostly restricted to the tap and crown roots within 0 to 5 cm from the stem base) than did bradyrhizobia distributed throughout the soil or inoculated at specific depths. Nodulation was greater below the depths at which bradyrhizobial cells were located rather than above, even though watering was done from below to minimize passive bradyrhizobial migration with percolating water. The most profuse nodulation occurred within approximately 5 cm below the point of placement and was generally negligible below 10 cm. These and other results suggest that bradyrhizobial migration from the initial point of placement was very limited. Nevertheless, the more competitive strain, effective strain THA 7, migrated into soil to a greater extent than the ineffective strain THA 1 did. Nitrogen fixation resulting from the dual-strain inoculations differed depending on the method of inoculation. For example, the amount of N(2) fixed when both strains were slurried together onto the seed was about half that obtained from mixing the effective strain into the soil with the ineffective strain on the seed. The results indicate the importance of rhizobial distribution or movement into soil for nodulation, nodule distribution, strain competitiveness, and N(2) fixation in soil-grown legumes.

Nitrogen fixation in soybean ( Glycine max L. merrill) as affected by nodulation patterns

Greenhouse and field experiments were made to investigate the influence of root nodule position on nitrogen fixation in soybean. The N-15 isotope dilution method was used to quantify N 2 fixed. Differences in the location of nodules on roots were induced through varying the inoculation procedure, timing or depth of inoculum placement in the soil. Movement of Bradyrhizobium japonicum in soil and rhizosphere was very limited, and nodule formation was restricted largely to the vicinity within which the bradyrhizobia were placed. With seed inoculation, most of the nodules occurred on the crown of the roots (0–5 cm segment of root), in contrast to the profuse and well distributed nodules when the inoculum was applied throughout the soil. Nodules were mostly on the lower portions of the roots when inoculum was below the seed. Nodule position affected N 2 fixation, with nodules formed on the lower part of the root system fixing significantly more N 2 than the crown nodules, and the later-formed nodules contributed also substantially to the total amount of N 2 fixed by the soybean. There appears to be a very strong case for improving inoculation methods and for selecting rhizobia not only for effectiveness but also for migration in soil and along the root in a range of conditions.

Effect of tillage on yield, nodulation and nitrogen fixation of soybean in far north-coastal New South Wales

An experiment to examine the effect of tillage practice on yield, nodulation and nitrogen fixation of soybean in a podsolic soil on the far north coast of New South Wales is reported. Soybeans were sown into either a cultivated or no-tilled seedbed following pasture in 1983 and 1984, and following soybeans in 1984 and 1985. Results over the 3 seasons indicated substantially improved nodulation under no-tillage. The mean nodulation index (nodule mass as a percentage of shoot mass) was 4.5 for no-tillage soybean and 2.3 for the cultivated crops. Nitrogen fixation, assessed using the ureide technique, was higher in the no-tillage plots, especially during early plant growth, Plant growth and seed yield were increased by no-tillage in the wetter 1984 season; the reverse occurred in the other 2 less favourable years. Data on crop N, seed N, and fixed N (estimated by partitioning N accumulated by the crops during successive periods of growth, according to the relative ureide values) were combined to calculate N balances. Potential gains of soil N were greatest under the no-tilled soybeans (as much as 110 kg Nha; mean over all seasons was 80 kg Nha). The cultivated crops showed a maximum gain of 86 kg N/ha and an average gain of 30 kg N/ha. The data indicate that soybean has the potential to improve the N fertility of podsolic coastal soils, particularly when grown using no-tillage practices.

Hydrogen metabolism and nitrogen fixation of soybean (Glycine max. L.) inoculated with different strains ofRhizobium spp.

Hydrogenase activities and N2-fixing capacities of soybean nodules (Glycine max. cv. Hodgson), inoculated with strains ofBradyrhizobium japonicum andRhizobium fredii from different geographical regions, were measured after 35 days of culture under controlled conditions. Of the strains tested, 47% induced nodules with bacteroids which recycled H2. The data obtained suggest that H2-recycling ability is not a major factor influencing early N2-fixation which depends essentially on the precocity and intensity of the initial nodulation.

Genotypic Variation for Nitrogen Fixation in Soybean

AbstractTwenty soybean cultivars from maturity groups IV, V, VI, VII and VIII were screened in the growth chamber study to determine their response to two Rhizobium strains through N‐fixation rates. Cultivars Lee 74, Essex and Bay showed high nitrogenase activities of 201.00, 93.75 and 74.86 nM C2H2/pl/hr, respectively. Braxton, Hutton and Bragg showed low nitrogenase activity rates of 4.73, 4.20 and 3.0 nM C2H2/pl/hr, respectively. A range of variation was found among the cultivars in shoot fresh and dry weights, nodule number and nodule weight.

Soybean nodule gas permeability, nitrogen fixation and dirunal cycles in soil temperature

While diurnal cycles in nitrogen fixation rates are sometimes assumed to result from diurnal variation in photosynthetically active radiation, contradicting evidence exists that indicate soil temperature is the primary environmental influence. These studies assessed the significance of temperature on soybean nitrogen fixation under field conditions. Two groups of intact field-grown soybean plants, one at ambient and the other exposed to a 10°C diurnal variation in soil temperature, were nondestructively assayed for acetylene reduction rates. Activity was closely associated with soil temperature (R2=0.85), even when temperature was 12 h out of phase with ambient. Data were also obtained to determine if the effects of rhizosphere temperature on nitrogen fixation are mediated through an effect on the nodule oxygen permeability. Nodule oxygen permeability of intact, aeroponically grown soybean was closely correlated with the diurnal changes in temperature (R2=0.90).

Effect ofRhizobium inoculation and the application of phosphate on the growth, yield and nitrogen fixation of soybeans

Application of phosphate at 60, 90 and 120 kg P ha−1 to the ‘Bragg’ variety of soybeans inoculated with a mixture of three strains ofRhizobium japonicum (TAL 102 + TAL 377 + TAL 379) and grown in silty loam soil in a pot experiments, significantly improved the number of nodules per plant and increased production of shoots and roots by 65, 36 and 17%, the yield of pods by 38, 12 and 3% and N2-fixing capacity by 57, 29 and 20%, respectively. Rhizobium inoculation alone with the test strains caused a positive but poor nodulation of the crop and increased its dry-matter production of shoots and roots by 22%, pods yield by 7% and N2-fixing capacity by 6%. Soybean plants from uninoculated treatments were without nodules indicating that indigenous rhizobia associated with this crop are absent in the test soil. Phosphate concentration in the total dry matter of mature crop exhibited an increasing tendency as a result of all the applied levels of phosphorus.

Regulation of Soybean Nitrogen Fixation in Response to Rhizosphere Oxygen

Nodule nitrogen fixation rates are regulated by a mechanism which is responsive to the rhizosphere oxygen concentration. In some legumes, this oxygen-sensitive mechanism appears to involve changes in the gas permeability of a diffusion barrier in the nodule cortex. In soybean evidence for such a mechanism has not been found. The purpose of this research was to make quantitative measurements of soybean nodule gas permeability to test the hypothesis that soybean nodule gas permeability is under physiological control and responsive to the rhizosphere oxygen concentration. Intact hydroponically grown soybean plants were exposed to altered rhizosphere oxygen concentrations, and the nodule gas permeability, acetylene reduction and nodule respiration rates were repeatedly assayed. After a change in the external oxygen concentration, nitrogenase activity and nodule respiration rates displayed a short-term transient response after which the values returned to rates similar to those observed under ambient oxygen conditions. In contrast to steady-state nitrogenase activity and nodule respiration, nodule gas permeability was dramatically affected by the change in oxygen concentration. Decreasing the external oxygen concentration to 0.1 cubic millimeter per cubic millimeter resulted in a mean increase in nodule gas permeability of 63%. Increasing the rhizosphere oxygen concentration resulted in decreased nodule gas permeability. These data are consistent with the hypothesis that soybean nodules are capable of regulating nitrogen fixation and nodule respiration rates in response to changes in the rhizosphere oxygen concentration and indicate that the regulatory mechanism involves physiological control of the nodule gas permeability.

Regulation of Soybean Nitrogen Fixation in Response to Rhizosphere Oxygen

Nitrogen fixation (acetylene reduction) rates of nodules on intact field-grown soybean (Glycine max) subjected to altered oxygen concentration (0.06-0.4 cubic millimeter per cubic millimeter) returned to initial rates during an 8-hour transitory period. Hydroponically grown soybean plants also displayed a transitory (1-4 hours) response to changes in the rhizosphere oxygen concentration after which the fixation rates returned to those observed under ambient oxygen concentrations. It was hypothesized that soybean nodules contain a regulatory mechanism which maintains a stable oxygen concentration inside nodules at a sufficiently low concentration to allow nitrogenase to function. A possible physiological mechanism which could account for this regulation is adjustment in nodule respiration activity such that nodule oxygen concentration and nitrogen fixation are maintained at stable levels. Experiments designed to characterize the non-steady-state oxygen response and to test for the presence of nodule respiratory control are presented. Non-steady-state acetylene reduction and nodule respiration (oxygen uptake) rates measured after alterations in the external oxygen concentration indicated that the regulatory mechanism required 1 to 4 hours to completely adjust to changes in the external oxygen concentration. Steady-state nodule respiration, however, did not respond to alterations in the rhizosphere oxygen concentration. It was concluded that soybean nodules can adjust to a wide range of rhizosphere oxygen concentrations, but the mechanism which controls nitrogen fixation rates does not involve changes in the nodule respiration rate.

Effect of combined nitrogen on nitrogen fixation of soybean (Glycine max L. Merill.) as affected by cultivar and rhizobial strain

Nine strains ofRhizobium japonicum (Bradyrhizobium japonicum) were screened for nitrogen fixation in combination with two cultivars of soybean, Chippewa and Dunadja at two levels of nitrogen fertilization,i.e. 20 kg N ha−1 and 100 kg N ha−1 using15N isotope dilution method. Plant dry weight, nitrogen yield, percent N derived from atmosphere (% Ndfa) and total amount of N2 fixed were strongly influenced by the specific combination of host-genotype and rhizobial strain. The interaction between the host and microsymbiont were so specific that accurate prediction of symbiotic performance of either partner in relation to a particular host or strain of Rhizobium appears impossible. The sensitivity of nitrogen fixation to combined nitrogen was furthermore dependent upon both the rhizobial strain and host-Rhizobium association. It is therefore, inadvisable to describe a certain bacterium as being fully effective/ineffective or sensitive/tolerant to combined nitrogen, except in relation to a particular host-genotype. There is scope for obtaining promising host-Rhizobium associations tolerant to combined nitrogen through exploiting the interactive effects between the host-genotypes and strains of Rhizobium.

Nitrogen fixation in soybean as influenced by cultivar and Rhizobium strain

Nitrogen fixation in soybean as influenced by cultivar and Rhizobium strain

Growth and nitrogen fixation in soybean (Glycine max (L.) Merr.) as affected by gibberellic acid treatment during reproductive development

Nodulated soybean (Glycine max (L.) Merr.) plants cv. ‘Williams’ were grown on a N-free medium and sprayed daily, after flowering, with a solution of 0,0.5 or 1.0 mg/l gibberellic acid (GA3). Relative growth rate, net assimilation rate and mean N2-fixation rate decreased in control plants from flowering to mid-pod filling. The decline of growth and N2-fixation was attenuated by GA3. Lesser decline of growth and N2-fixation in GA3-treated plants was linked to enhancement of vegetative growth, to delay of fruit development and to arrest of root decay.

Reproductive Development and Nitrogen Fixation in Soybean (Glycine max[L.] Merril)

Gomes, M. A. F. and Sodek, L. 1987. Reproductive development and nitrogen fixation in soybean (Glycine max (L.) Merril).—J. exp. Bot. 38: 1982–1987. Nitrogenase activity (acetylene reduction) was measured during the growth cycle of soybean plants induced to flower at two different ages. The decline in nitrogenase activity towards the end of the cycle was clearly associated with pod-filling for both flowering dates when plants were cultivated under lower light and temperature conditions (out of season). Under higher light and temperature conditions (normal growing season) the decline was independent of the flowering date. Furthermore, the timing of the decline was not altered when plants were maintained under long-day (vegetative) conditions nor when flowers were removed. It is suggested that under more favourable growth conditions the diversion of assimilates by the fruits is not the primary cause of the decline in nodule activity, but competition by the fruits may be important when the production of photo-assimilates is more limited.

Effects of red and far red lights on nodulation and nitrogen fixation in soybean (Glycine max L.Merr)

Rooted leaves and plants were irradiated at the end of the photoperiod with red light for 15 minutes, while another group was also irradiated with red light and immediately afterwards with far- red light. The reduction in Pfr/Ptotal established by far red irradiation promoted nodulation probably by affecting an hormonal balance.

Nitrogen fixation in soybeans as influenced by cultivar and Rhizobium strain differences

The effect of soybean variety and Rhizobium strain, as well as the level of nitrogen fertilizer, were tested in a field experiment in Greece. Three nodulating varieties were used and one non-nodulating variety as control, with two Rhizobium strains, one commercially available and one isolated from the soil of the experimental site. Nitrogen fertilizer labeled with 15N enabled the nitrogen derived from the atmosphere (Ndfa), from the soil (Ndfs), and from the fertilizer (Ndff) to be estimated. Statistical analyses showed that the combined variety-strain effect was responsible for most of the variation observed in all parameters, either measured directly or calculated, while the nitrogen level had no effect. The locally isolated strain generally performed equally as well as the commercial one. With the highest yielding variety in particular, the nitrogen-fixing efficiency of soybean nodules, expressed as plant total nitrogen in excess of that in the non-nodulated control in relation to nodule dry weight, was even superior. Taking into account the low fertilizer recovery by plants, it is suggested that adapted cultivars properly inoculated can fix most of the nitrogen they need for high yields. This is of great economic importance for crops with high nitrogen-fixing efficiency, like the soybeans used in this work, which can fix more than 200 kg N/ha, as 15N dilution and nitrogen difference evaluations have confirmed. The local cultivars in this connection were superior to the United States cultivar, while the difference between cultivars in symbiotic performance were not due to the ability to nodulate, but rather to a much higher nodule-specific efficiency. The commercially available strain was found to produce generally more nodules and the locally isolated strain produced less but larger and more efficient nodules. Finally, the grains from the nodulated plants contained significantly smaller quantities of Fe, Ni, Cu, Zn, and especially Mo compared with non-nodulated plants, as determined by X-ray fluorescence techniques.

A comparison of inhibition of French‐bean and soybean nitrogen fixation by nitrate, 1% oxygen or direct assimilate deprivation

Inhibition by NO−3 of acetylene reduction in bean (Phaseolus vulgaris L. cv. Contender) and soybean (Glycine max L. cv. Amsoy 71) was measured in parallel with nodule carbohydrate and nitrate metabolism. In bean the onset of inhibition of C2H2 reduction (6 h) coincided with decreased import of assimilates and a lowering of carbohydrate pools (sucrose, glucose and starch). Nitrate reductase (EC 1.6.6.1) activity was induced in all plant organs after 3 h but no nitrite was detected in the nodules. In soybean, nodule carbohydrate concentrations and import of assimilates into the nodules increased markedly between 6 to 24 h after supply of nitrate when the nitrogenase (EC 1.7.99.2) was progressively inhibited. High nitrate reductase activity was observed in the nodules and nitrites accumulated because of insufficient nitrite reductase activity. The nitrate‐induced inhibition of nitrogenase was compared with the inhibition observed with low oxygen around the roots (1% O2) or with direct assimilate deprivation (girdling or decapitation). Soybean and bean appeared equally sensitive to these treatments as regards to acetylene reduction. The results are discussed in relation to the current hypotheses explaining nitrate‐induced inhibition of dinitrogen fixation: assimilate deprivation or nitrite poisoning. Present data are in favour of the first for bean and of the second for soybean.

Effects of plant breeding and selection on yields and nitrogen fixation in soybeans under two soil nitrogen regimes

Soybeans (Glycine max (L.) Merr.) have a high N requirement which is fulfilled by soil N uptake and N2-fixation. This study was concerned with the effects of past yield selection on N2-fixation in soybeans. The soybean cultivars, ‘Lincoln’, ‘Shelby’, and ‘Williams’, which represent successive improvements in the ‘Lincoln’ germplasm, and a non-nodulating control were planted in a soil containing15N labelled organic matter. Two replications occurred on soil previously cropped to alfalfa and two on soil previously cropped to soybeans. Plants were harvested at five growth stages and leaf area, plant weight, total N, and atom percent15N were determined. Mature grain was harvested and yield components were also determined, as well as the total N and15N content. Cultivar differences in total dry matter were only evident at physiological maturity, when Williams contained the greatest dry matter. Williams exhibited the longest period of seed formation and seed fill and also had the highest grain yield which resulted from a larger weight per seed. The N content of the cultivars did not vary until physiological maturity when Williams contained the highest percent N. The quantity of N fixed at physiological maturity was highest for Williams and lowest for Lincoln. Fixed N contained in the harvested grain was greater for Williams than for the other two cultivars. The fraction of the total plant N derived from fixation was not greatly affected by cultivar and all cultivars acquired an average of 50% of their total N through N2-fixation. Previous cropping history greatly affected the quantity of N fixed and the fraction of the total plant N derived from fixation. Soybeans following soybeans were more dependent upon N2-fixation than soybeans following alfalfa with the former deriving 65% of the total plant N from fixation and the latter only 32%. These soybean cultivars apparently utilized soil N first and then used N2-fixation to satisfy their N requirement. The past selection for higher yield has resulted in soybean cultivars with improved capacities to fix atmospheric N2 and an improved ability to take up available soil N.

Nodulin-24 gene of soybean codes for a peptide of the peribacteroid membrane and was generated by tandem duplication of a sequence resembling an insertion element

A nodulin gene coding for a polypeptide with an apparent M(r) of 24,000 (nodulin-24) was isolated from soybean (Glycine max). DNA sequence analysis of this gene revealed that its coding capacity is for a polypeptide of only M(r) 15,100 and is interrupted by four introns. The three middle exons and their flanking segments appear to have been generated by duplications of a unit resembling an insertion sequence. This unit is bounded by a 12-base-pair inverted repeat and encompasses the 54-base-pair exon corresponding to each of three central hydrophobic domains of the protein, nodulin-24. The resulting repeated hydrophobic structure of this protein may be responsible for an apparent increase in M(r) from 15,100 to 24,000. In vitro translation and immunological studies suggest that nodulin-24 is a precursor and is processed cotranslationally into a M(r) 20,000 polypeptide. This polypeptide is a component of the membrane envelope enclosing the bacteroids (peribacteroid membrane) synthesized during symbiosis with Rhizobium. The low degree (<6%) of sequence divergence among the repeated units suggests that this gene has been generated recently during the evolution of symbiotic nitrogen fixation in soybean.