Showing papers on "Nitrogen fixation published in 1977"

Nitrogen Fixation In Grasses

Abstract: Publisher Summary This chapter describes nitrogen fixation in C-3 and C-4 grasses. It mentions that nitrogen-fixing bacteria, which have been found in association with grasses are all capable of fixing nitrogen in soil or culture medium without the plant. Therefore, they are generally included in the group of free-living N 2 -fixing bacteria. Emphasis is given on bacteria for which specific associations with tropical grasses have been shown. Nitrogen fixation in digitaria decumbens and paspalum notatum cores has been confirmed by the incorporation of 15 N 2 . Acetylene reduction assays over a 24-hour period in cores indicating fixation of more than 100 g N/ha per day have been obtained with several tropical forage grasses, rice, and occasionally with wheat and rye grown under tropical conditions. N 2 fixation estimated by the excised root method in maize and sorghum has been shown to be several-fold higher than the amount of N 2 fixation obtained from core assays. The chapter discusses various factors affecting nitrogen fixation in grasses—such as, (1) seasonal and diurnal fluctuations, (2) plant genotype, (3) temperature, (4) oxygen, (5) combined nitrogen.

The utilization of the Azolla - Anabaena complex as a nitrogen fertilizer for rice

Abstract: Because it contains nitrogen fixing blue-green algae Anabaefa azota in its fronds, AzoZla grows on a nitrogen-free solution, doubles its mass in 3 or 5 days, and accumulates 30 or 40 kg of N/ha in 2 weeks. A calcium or phosphorus deficiency in the Azolla culture solution produces severe deterioration on growth. The optimum solution pH for Azolia is 5.5; a higher pH produces iron deficiency. Azolia is sensitive to a temperature higher than 310C (350 day which causes reddish-brown discoloration and reduces vigor...

Ontogenetic Interactions between Photosynthesis and Symbiotic Nitrogen Fixation in Legumes

Abstract: Photosynthetic data collected from Pisum sativum L. and Phaseolus vulgaris L. plants at different stages of development were related to symbiotic N2 fixation in the root nodules. The net carbon exchange rate of each leaf varied directly with carboxylation efficiency and inversely with the CO2 compensation point. Net carbon exchange of the lowest leaves reputed to supply fixed carbon to root nodules declined in parallel with H2 evolution from root nodules. The decrease in H2 evolution also coincided with the onset of flowering but preceded the peak in N2 fixation activity measured by acetylene-dependent ethylene production. A result of these changes was that the relative efficiency of N2 fixation in peas increased to 0.7 from an initial value of 0.4. The data reveal that attempts to identify photosynthetic contributions of leaves to root nodules will require careful timing and suggest that the relative efficiency of N2 fixation may be influenced by source-sink relationships.

Physiology and chemical composition of nitrogen-fixing phytoplankton in the central North Pacific Ocean

Abstract: The magnitude and physiological characteristics of biological nitrogen fixation have been studied in the oligotrophic waters of the North pacific gyre. The filamentous blue-green algae Trichodesmium spp. and Richelia intracellularis were the important nitrogen-fixing phytoplankton. Most of the nitrogen fixation occurs in the upper 40 m of the water column, with detectable fixation as deep as 90 m, which corresponds to about the 1 % light depth. There was no evidence of photoinhibition of nitrogen fixation, although CO2 reduction was depressed slightly at the highest light levels. The rate of nitrogen fixation in the water column varied throughout the day, being highest in mid-morning and in late afternoon. Relatively high fixation rates were also found during periods of darkness. Elevated oxygen concentrations had a marked inhibitory effect on rates of nitrogen fixation, a pO2 of 0.4 atm causing a 75% inhibition. Data from studies of nitrogen fixation and assimilation rates of 15N-labelled nitrate, ammonium, and urea indicate that nitrogen fixation furnished about 3% of the total daily fixed nitrogen requirement for phytoplankton growth. Studies with isolated colonies of Trichodesmium spp. indicated that 100% of their nitrogen requirement was met by nitrogen fixation. Chemical composition of the Trichodesmium colonies showed that the C:N ratio was 4.1 and that their phosphorus content relative to carbon or nitrogen was much lower than that of the total particulate material in the water column. Elevated ratios of carbon: adenosine triphosphate (ATP) also suggest that phosphorus deficiency may be limiting the growth of Trichodesmium. The magnitude of nitrogen fixation in the gyre is seasonally dependent, with high rates in late summer and autumn. At these times the water column is stratified, with phosphate and nitrate barely detectable in the upper 100 m. Our data suggest that during these months of stratification, biological fixation of nitrogen amounts to about 33 μg-at N/m2/day.

Effects of soil acidity on rhizobia numbers, nodulation and nitrogen fixation by alfalfa and red clover

Abstract: The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse exp...

Energy requirement for symbiotic nitrogen fixation

Abstract: Comparing the energy required by legumes for symbiotic nitrogen fixation with that of assimilation of nitrate, Gibson concluded the costs to be about the same. About 15% of net photosynthetic production by the plant may be used in meeting its nitrogen requirements. If energy for the fixation of nitrogen symbiotically and that for the assimilation of NH4+ or NO3- from the soil solution are both provided by the chemical products of photosynthesis, then the CO2 respired in supplying that energy must contribute to the total efflux of CO2 from the plant in the dark. McCree and Thornley have discussed methods of partitioning the dark CO2 efflux into a growth (synthesis) and a maintenance component. Both nitrogen fixation and nitrogen assimilation can be expected to contribute to the CO2 flux associated with synthesis. If Gibson is correct, nodulated plants using only symbiotically fixed nitrogen should have the same growth coefficient as non-nodulated plants supplied with exogenous mineral nitrogen when grown in the same conditions. I have examined this hypothesis using a modification of the method used by McCree with Trifolium subterraneum L. cultivar Woogenellup as test material.

Interactions Between Growth, Phosphate Content and Nitrogen Fixation in Mycorrhizal and Non-Mycorrhizal Medicago sativa

Abstract: Nodulated Medicago sativa cv. Europe plants, both non-mycorrhizal and mycorrhizal (inoculated with Glomus mosseae), were grown in sand or soil with a range of phosphate levels. The following parameters were measured: intensity of mycorrhizal infection, intensity of nodulation, growth, phosphate content, nitrogenase activity (acetylene reduction) and nitrogen content. Both nodulation and mycorrhizal infection had occurred within 2 weeks of inoculation with the appropriate endophytes. Major increases in dry weight of mycorrhizal plants were not apparent until approximately 10 weeks from inoculation. However, mycorrhizal plants showed more extensive nodulation, coupled with higher rates of nitrogenase activity from 2 weeks onwards, and at the final (12-week) harvest had higher values of % N. Phosphate content of mycorrhizal plants (µg P/g dry wt) was also greater than non-mycorrhizal plants at 7 weeks. By 10 or 12 weeks, when significant mycorrhizal enhancement of growth was apparent, the total nitrogen and total phosphorus per mycorrhizal plant were also higher, but nitrogenase activity and phosphate content measured on a dry weight basis showed no significant differences between mycorrhizal and non-mycorrhizal plants. It is clear that mycorrhizal enhancement of phosphate uptake and nitrogen fixation precedes any effect on growth and the results indicate the importance of the time factor in the development of this tripartite symbiosis between legume, Rhizobium and mycorrhizal fungus.

Ammonia assimilation and nitrogen fixation in rhizobium meliloti

Abstract: The enzymes involved in ammonia assimilation by Rhizobium meliloti 4l and their role in the regulation of nitrogen metabolism were studied. Glutamine synthetase (GS) and glutamate synthase (GOGAT) were present at relatively high levels in cells grown in media containing either low or high concentrations of ammonia. NADP-linked glutamate dehydrogenase could not be detected. GOGAT and GS mutants were isolated and characterised. A mutant lacking GOGAT activity did not grow even on high concentrations of ammonia, it was a glutamate auxotroph and was effective in symbiotic nitrogen fixation. The GS and assimilatory nitrate reductase activities of this mutant were not repressible by ammonia but still repressible by casamino acids. A mutant with low GS activity required glutamine for optimal growth. It was ineffective and its nitrate reductase was not inducible. These findings indicate that ammonia is assimilated via the GS/GOGAT pathway in free-living R. meliloti and bacterial GOGAT is not important in symbiosis. Furthermore, GS is suggested to be a controlling element in the nitrogen metabolism of R. meliloti.

Uptake of soil nitrogen by legumes in mixed swards

Abstract: The partitioning of uptake of soil nitrogen between legumes and grasses in mown, mixed swards was studied at two sites in south-eastern Queensland. The swards contained either Lotononis bainesii, Desmodium intortum or Trifolium repens with Digitaria decumbens at one site, and either L. bainesii, T. repens, Macroptilium atropurpureum, Vigna luteola or Stylosanthes guyanensis with Chloris gayana at the other site. (15NH4)2SO4 equivalent to c. 0.3 kg nitrogen ha-1 was added every 4 weeks in an attempt to label the soil mineral nitrogen, and the partitioning of 15N uptake between species used as an estimate of the partitioning of uptake of soil nitrogen. Although two of the legumes (L. bainesii and T. repens) obtained 70–100% of the total 15N uptake at some of the spring harvests, when growth of the associated tropical grasses was limited by low temperatures, none of the legumes obtained more than c. 25% of the annual 15N uptake over a 2-year period. Proportional 15N uptake by the legumes was curvilinearly related to the proportion of legume dry matter yield in the mixtures. Annual 15N uptake by the grass-legume mixtures was up to 360% as high as by the grass control. This had only a small effect on estimates of the proportion of legume nitrogen derived from symbiotic fixation, but caused a large discrepancy in isotopic estimates of nitrogen transfer. The proportion of fixed nitrogen in the legumes averaged 94% at one site and 92% at the other, nearly always exceeded 80%, and was independent of legume yield.

Nitrate effects on the nodulation of legumes inoculated with nitrate-reductase-deficient mutants of Rhizobium.

Abstract: The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g(-1) nodule fr. wt. h(-1)), were both affected by the added nitrate.

Isolation and characterization of a marine Anabaena sp. capable of rapid growth on molecular nitrogen

Abstract: A marine filamentous cyanobacterium capable of rapid growth under N2-fixing conditions has been isolated from the Texas Gulf Coast. This organism appears to be an Anabaena sp. and has been given the strain designation CA. Cultures grown on mineral salts medium bubbled with 1% CO2-enriched air at 42°C show a growth rate of 5.6±0.1 generations per day with molecular nitrogen as the sole nitrogen source. This growth rate is higher than any other reported in the literature to date for heterocystous cyanobacteria growing on N2. Under similar growth conditions, 7.5 mM NH4Cl yields a growth rate of 6.6±0.1 generations per day while 7.5 mM KNO3 allows for a growth rate of 5.8±0.4 generations-day. Nitrogen-fixation rates, as measured by acetylene reduction, show maximum activity values in the range of 50–100 nmoles ethylene produced/minxmg protein. These values compare favorably with those obtained from heterotrophic bacteria and are much higher than values reported for other cyanobacteria. Growth experiments indicate that the organism requires relatively high levels of sodium and grows maximally at 42°C. Because of its high growth rate on N2, this newly isolated organism appears ideal for studying nitrogen metabolism and heterocyst development among the cyanobacteria.

Nitrogen fixation (acetylene reduction) in a salt marsh amended with sewage sludge and organic carbon and nitrogen compounds.

Abstract: Seasonal distribution of nitrogen fixation by Spartina alterniflora epiphytes and in surface and soil samples was investigated in a Georgia salt marsh which was amended with sewage sludge or with glucose and/or ammonium nitrate. There was no significant difference between the rates of fixation in the unamended and sewage sludge plots. Additional perturbation experiments suggested that nitrogen addition indirectly stimulates nitrogen fixation by enhancing Spartina production and root exudation. Glucose additions, on the other hand, suppressed nitrogen fixation on a long-term basis. It is suggested that the microbial population in the soil out-competed the plants for the available nitrogen and in turn suppressed plant production and possibly root exudation. A comparison of nitrogen fixation in clipped and unclipped Spartina plots substantiated the suggestion that root exudation probably supports nitrogen fixation. Fixation in the clipped plots was significantly lower (P < 0.05) than the rates in the unclipped plots.

Nitrogen Fixation by Azolla in Rice Fields

Abstract: Azolla is a floating aquatic fern widely distributed throughout temperate and tropical fresh waters. There are two indigenous species in the Sacramento Valley of central California: A. filiculoides and A. mexicana (Mason, 1957). Their natural habitats include agricultural drainage waters, ponds, and calm waters of rivers. Azolla like many species of legumes, harbors a symbiotic microorganism capable of reducing atmospheric nitrogen and supplying this fixed nitrogen to the higher plant. The prokaryote associated with Azolla is a blue-green alga (Anabaena azollae) which is able to photosynthesize independently. Unlike legumes, however, the Azolla-Anabaena pair apparently continues to fix atmospheric nitrogen in the presence of significant quantities of combined nitrogen (Becking, 1976; Peters et al., 1976). This property and high rates of acetylene reduction demonstrated for Azolla (Becking, 1976) suggest a potential agronomic role for temperate Azolla species in photosynthetic production of fertilizer nitrogen.

Nitrogen accumulation in kaolin mining wastes in cornwall

Abstract: Nitrogen accumulation was studied in mica and sand mining wastes of Cornwall after twelve forage legume varieties were established with the use of lime and fertilizers containing phosphorus and potassium. In the finetextured mica waste legume productivity and nitrogen accumulation were similar to those for upland pastures in Cornwall; but legume growth was limited by summer drought on the coarse-textured sand waste. Native perennial legumes well adapted to the British climate were the most productive and showed the highest potential for nitrogen fixation. More than 500 kg N/ha accumulated during the 2-year period whenTrifolium pratense andLotus corniculatus were established on mica waste, and more than 250 kg N/ha was accumulated by these legumes on sand waste.Trifolium pratense andLotus corniculatus were persistent on both the mica and sand waste, andMedicago lupulina showed an unusually high tolerance for competition from invading and sown grass on the sand waste.Trifolium repens andT. hybridum are recommended for waste sites where grazing is a part of management. Nitrogen accumulation on mica waste was consistent with N fixation rates expected from climatic conditions. Nitrogen fixation by free-living bacteria is limited by the low organic matter content of the wastes. The nitrogen fixation potential by legumes on sand wastes has been underestimated because leaching losses were not adequately evaluated. Since nitrogen accumulation rates by earlyTrifolium pratense andT. repens were 70 percent higher than the maximum rate estimated for natural legumesi.e. (Ulex europaeus) on sand waste, the use of forage legumes should reduce reclamation time considerably. re]19760512

Glutamine synthetase and control of nitrogen fixation in Rhizobium

Abstract: Rhizobia have recently been shown to fix nitrogen while living free1,2,3,4. Unfortunately, free-living fixation occurs only at the end of exponential growth, and there is no condition in which bacterial growth is dependent on reduction of dinitrogen by nitrogenase (EC 1.7.99.2). In the unrelated Klebsiella pneumoniae where fixation does occur in culture, nitrogenase expression is regulated by the enzyme glutamine synthetase (GS) (EC 6.3.1.2). Mutants lacking GS activty (glnˉ) fail to induce measurable nitrogenase activity5,6.

Influence of lime on nitrogen fixation by tropical and temperate legumes

Abstract: A nitrogen deficient Oxisol which had been fertilized with P, K, Zn and Mo received CaCO3 at rates which increased continuously from zero to 22 tons/ha. Liming produced a range of pH in the saturation paste from 4.7 to 7.1; a range of calcium in the saturation extract from 0.3 to 3 meq/l; and a significant decline in available manganese. Responses of 9 tropical and 7 temperate legumes were compared across the pH variable.

Nitrogen Nutrition of Cowpea (Vigna unguiculata). I. Effects of Applied Nitrogen and Symbiotic Nitrogen Fixation on Growth and Seed Yield

Abstract: Effectively nodulated cowpea plants, grown in pots without applied nitrogen, were vegetatively equal to non-nodulated plants supplied with 60 ppm N throughout growth (88 days) and produced significantly greater seed yields. Supplying non-nodulated plants with 120 or 240 ppm N improved seed yields (but not significantly) compared with plants completely dependent on symbiotic fixation. Nodulation promoted branching, and improved pod set and/or retention compared with plants relying on applied N.

Effets des souches de rhizobium meliloti et des coupes successives de la luzerne (medicago sativa) sur la fixation symbiotique d’azote

Abstract: Symbiotic nitrogen fixation with 49 isolates of Rhizobium meliloti was studied under controlled environment with alfalfa cv. Saranac. It was shown that plant yield in dry weight can be used as an indirect measurement of nitrogen fixation, and as a criterion for selecting efficient strains of R. meliloti. Statistical study on yields of three cuttings has established that the second cutting gives the most necessary information to correctly evaluate the symbiotic efficiency of the isolates. Six very efficient strains were selected.

Acetylene reduction by soil cores of maize and sorghum in Brazil.

Abstract: Nitrogenase activity was measured by the C(2)H(2) reduction method in large soil cores (29 cm in diameter by 20 cm in depth) of maize (Zea mays) and sorghum (Sorghum vulgare). The activity was compared to that obtained by a method in which the roots were removed from the soil and assayed for nitrogenase activity after an overnight preincubation in 1% O(2). In a total of six experiments and 28 soil cores, the nitrogenase activity of the cores was an average of 14 times less than the activity of roots removed from the same cores and preincubated. Nitrogenase activity in the cores was very low and extrapolated to an average nitrogen fixation rate of 2.8 g of N/hectare per day. It was shown that inadequate gas exchange was not a reason for the lower activity in the soil cores, and the core method gave satisfactory results for nitrogenase activity of soybeans (Glycine max) and Paspalum notatum.

Decomposition of rice residues in tropical soils: IV. The effect of rice straw on nitrogen fixation by heterotrophic bacteria in some Philippine soils

Abstract: The acetylene-reducing activity of waterlogged soils was stimulated by the incorporation of rice straw at a relatively early stage of its decomposition. The straw caused a decrease in the inorganic nitrogen and in redox potential, making a favorable environment for N2-fixing bacteria. But the stimulation of nitrogen fixation was observed only when the soils were kept waterlogged. Soils of Maahas and Banaue which had not been air dried showed a fairly high acetylene-reducing activity when rice straw was incorporated at a ratio of 0.5 or 1.0 percent. Also the rice stubble showed high acetylene-reducing activity when the stubbled soil was kept waterlogged.

Comparison of colony morphology, salt tolerance, and effectiveness in Rhizobium japonicum.

Abstract: Four strains of Rhizobium japonicum, two of which produce slimy and non-slimy colony types and two others which produce large and small colony types, were isolated and cloned. All were infective and nodulated Lee soybean host plants. Each colony type was characterized as to its salt sensitivity to Na+ and K+ ions, relative level of symbiotic nitrogen fixation, and relative level of free-living nitrogen fixation. Growth studies performed in the presence of salts demonstrated that the non-slimy or small colony types were sensitive to salt with significantly depressed growth rates and cell yields. Growth rates and cell yields of slimy, large, colony types were relatively unaffected by salt. Both symbiotic and free-living (non-associative) nitrogen fixation analyses (by acetylene reduction) revealed that the non-slimy, small colonies were significantly more effective than slimy, large colonies.

Influence of some environmental factors on nitrogen fixation in the rhizosphere of rice

Abstract: Nitrogen fixers make up a large percentage of the total microflora in the rhizosphere of lowland rice. There are more aerobic nitrogen fixers than there are anaerobic ones.

Nitrogenase activity of endophyte suspensions derived from root nodules of Alnus, Hippophaë, Shepherdia and Myrica spp.

Abstract: STUDIES of nitrogenase of root nodule homogenates have focused chiefly on the Rhizobium–legume system. Little is known about the nitrogenase of actinomycete-like endophytes of root nodules on woody, non-leguminous plants. Although nitrogen fixation has been reported in suspensions of the endophyte from Myrica cerifera1,2, the results were either of very low significance or irreproducible. In both cases dithionite and oxygen were added, which seems to be contradictory. Subsequent attempts to detect nitrogen fixation in non-leguminous nodule homogenates have been unsuccessful and investigations stopped at an early stage. We have found3, however, that reasonable levels of acetylene reduction by nodule homogenates of Alnus glutinosa can be measured if 0.3 M sucrose and 0.1 M dithionite are present during anaerobic homogenisation. The latter was essential because the nodule material contains large amounts of phenolic compounds, which after oxidation inhibit nitrogenase activity. While determining optimal conditions for the nitrogenase assay it was found that the reaction was ATP-dependent but that addition of an ATP-generating system (creatine phosphate (Cr ∼ P)/creatine phosphokinase) decreased the activity during short-term experiments. This inhibitory effect was not found when the same ATP-generating system was added to bacteroid suspensions derived from leguminous nodules. We report here the seemingly aberrant behaviour of the added ATP-generating system, the applicability of our method to other actinomycete-woody plant symbioses, and the separation of actively acetylene-reducing endophyte material from nodule homogenates.

Fixation, accumulation, and distribution of nitrogen in a crop of Lupinus angustifolius cv. Unicrop

Abstract: A lupin crop was sampled each week to measure nitrogen fixation by acetylene reduction assay and for determination of the total nitrogen content on the organs on each axis of the plant. Nitrogen fixation started 5 weeks after sowing, reached its maxirnum rate per plant at the beginning of flowering on the main axis, and ceased during the period of rapid grain filling, which was 4 weeks before maturity. Plants did not accumulate measurable quantities of nitrogen until 2 weeks after the start of nodular fixation as indicated by acetylene reduction. In the vegetative phase within each order of axes most nitrogen went to the leaves before they senesced. During the first half of the period of rapid grain filling, both the weight and the concentration of nitrogen in the grain increased at the expense of the vegetative components. Balance sheets for nitrogen content and the current proportional distribution of nitrogen are presented for three occasions at weeks 8-9, weeks 15-16 and weeks 18-19. Waterlogging greatly decreased acetylene reduction and plant growth.