Effects of Nitrate and Ammonium on Nitrogenase (C2H2 Reduction) Activity of Swards of Subterranean Clover, Trifolium subterraneum L

1986 ◽  
Vol 13 (2) ◽  
pp. 257 ◽  
Author(s):  
JH Silsbury ◽  
DW Catchpoole ◽  
W Wallace
Keyword(s):  
Nitrogen Fixation ◽  
Nitrate Reductase ◽  
Root System ◽  
N2 Fixation ◽  
Nitrogenase Activity ◽  
Alternative Hypothesis ◽  
Subterranean Clover ◽  
Mineral Nitrogen ◽  
Soluble Nitrogen ◽  
Split Root System

Small swards of subterranean clover plants were grown under controlled conditions without mineral nitrogen and allowed to establish an effective nitrogen fixation system. Nutrient solutions containing nitrate from 0 to 16 mM or of ammonium from 0 to 5 mM were then applied and changes in nitrogenase activity (NA) estimated by acetylene reduction assay (AR) and the rate of hydrogen evolution (HE) for periods of up to 35 days. In two experiments a split-root system was used to enable mineral nitrogen to be applied to only one-half of a nodulated root system whilst the NA of both halves was monitored. NA by subterranean clover was very sensitive to exogenous mineral nitrogen, concentrations as low as 0.5 mM NO3- suppressing activity significantly, and 3-5 mM stopping it almost completely within 7 days. The degree of inhibition induced by concentrations between 0.5 and 3 mM NO3- was less at a photon irradiance of 1000 compared with 300 �mol quanta s-1 m-2 . Under some conditions NA continued at a reduced but steady rate in the presence of nitrate. NH4+ also markedly depressed NA but a concentration greater than 5 mM was needed to effect the same response. After NO3- was applied to an active symbiosis, nitrate reductase activity increased as NA decreased. Our results do not support the hypothesis of a direct effect of NO3- on nitrogenase due to the accumulation of toxic NO2-. Although our results allow that assimilate might be diverted from the nodules after the application of NO3- thus reducing N2-fixation, an alternative hypothesis is proposed: that nitrogenase and nitrate reductase work in a complementary manner in supplying reduced nitrogen to whole plants, and NO3- depresses N2-fixation through a regulatory system involving the level of soluble nitrogen in the plant. We conclude that nitrogen fixation by subterranean clover in the field may be depressed below its potential due to the presence of soil mineral nitrogen.

Effects of temperature on germination, emergence and early seedling growth of swards of Mt Barker subterranean clover plants grown with and without nitrate

1984 ◽  
Vol 35 (4) ◽  
pp. 539 ◽  
Author(s):  
JH Silsbury ◽  
D Zuill ◽  
PH Brown
Keyword(s):  
N2 Fixation ◽  
Nitrogenase Activity ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Mineral Nitrogen ◽  
Mineral N ◽  
Area Index ◽  
Closed Canopy ◽  
Early Seedling

Effects of constant temperatures of 10, 15, 20, 25 and 30�C on the germination, emergence and early vegetative growth of Trifolium subterraneum L. cv. Mt Barker grown as swards were examined in temperature-controlled glasshouses and in a growth cabinet. Seedlings were established at a density of about 2000 plants m-2 and grown for up to 70 days. Plants were either inoculated and grown without mineral nitrogen (-N), or supplied with 7.5 mM NO-3 (+ N). Percentage germination and emergence were hardly affected by temperatures of 10-20�C, but at 25�C were reduced to 50%, and at 30�C to about 10%. The rates of germination and emergence were slowest at 10�C, but showed little change with temperature over the range 15-30�C. Time to closed canopy (leaf area index 3) and time to a dry weight of 133 g m-2 were shorter where plants were supplied with NO; than where mineral nitrogen was withheld and a symbiotic system established. Rates of N2-fixation, as measured by acetylene reduction assay, were not markedly affected by temperature over the range 10-25�C. Relative efficiency ranged from about 0.55 at 10, 15, and 20�C to about 0.66 at 25�C. At 30�C nodulation still occurred, but nitrogenase activity was very slight. It is concluded that, where swards of subterranean clover are grown in the absence of any mineral N, a period of N-starvation limits growth during the time taken for symbiotic N2-fixation to become established. Such retardation of growth is small at about 20�C, but becomes more marked at lower and higher temperatures. The establishment of subterranean clover swards in soils of low N status are likely to be retarded following an early (March) or a late (July) start in the growing season. In such cases a 'starter' application of mineral nitrogen may promote the early growth of the legume.

Phenotypic reversion of nitrogenase in pleiotropic mutants of Rhizobium meliloti

1979 ◽  
Vol 25 (3) ◽  
pp. 298-301 ◽  
Author(s):  
Ilona Barabás ◽  
Tibor Sik
Keyword(s):  
Amino Acids ◽  
Nitrogen Fixation ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Symbiotic Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Nitrogenase Activity ◽  
Reductase Activity ◽  
Amino Acid Utilization ◽  
Phenotypic Reversion

In two out of three pleiotropic mutants of Rhizobium meliloti, defective in nitrate reductase induced by amino acid utilization in vegetative bacteria and in symbiotic nitrogen fixation, nitrogenase activity could be restored completely by purines and partially by the amino acids L-glutamate, L-aspartate, L-glutamine, and L-asparagine. The compounds restoring effectiveness in nitrogen fixation did not restore nitrate reductase activity in vegetative bacteria. The restoration of effectiveness supports our earlier conclusion that the mutation is not in the structural gene for a suggested common subunit of nitrogenase and nitrate reductase.

Nitrogen and water flows under pasture - wheat and lupin - wheat rotations in deep sands in Western Australia. 1. Nitrogen fixation in legumes, net N mineralisation,and utilisation of soil-derived nitrogen

1998 ◽  
Vol 49 (3) ◽  
pp. 329 ◽  
Author(s):  
G. C. Anderson ◽  
I. R. P. Fillery ◽  
P. J. Dolling ◽  
S. Asseng
Keyword(s):  
Nitrogen Fixation ◽  
Western Australia ◽  
N2 Fixation ◽  
Supply And Demand ◽  
Subterranean Clover ◽  
High Rate ◽  
Organic N ◽  
N Mineralisation ◽  
Soil Cores ◽  
Inorganic N

Detailed studies on the eciency with which pastures and crops use soil-derived nitrogen (N) in southern Australia are limited. Inefficiencies in the N cycle are indicated by wide spread soilacidification and low N status in wheat grain. The aims of this study were to document rates of N2 fixation by subterranean clover-based pastures and narrow-leaf lupin, plant uptake of soil-derived N, mineralisation of organic N during legume and cereal phases, and export of N from pastures, lupin,and wheat in relation to climate and soil water. These measurements were undertaken in a rotation experiment conducted on a deep sand located in the northern wheat belt of Western Australia at a site with a long-term average rainfall of 460 mm. The rotations examined over 3 years were 2 years pasture-wheat and lupin-wheat. The 15N natural abundance technique was used to differentiate soil-derived N from atmospheric Nin legumes. Biomass production, grain yields, and N contents were standard plant measurements in all treatments. Net N mineralisation between growing seasons was as certained by measuring changes in soil inorganic N to 1·5 m. Growing season net N mineralisation was determined using an in situ method in which soil cores were isolated from plant roots. Anion exchange resin was used to trap NO-3 leached below the depth of the soil cores. Nitrogen fixation by subterranean clover in a mixed pasture ranged from 29 to 162 kg N/ha whereas N2 fixation by lupins was less variable, ranging from 90 to 151 kg N/ha. Pastures were large consumers of soil-derived N (range 58-154 kg N/ha), with capeweed being the most important sink (range 38-120 kg N/ha). In comparison, wheat and lupins were inefficient users of soil N, removing 29-51 kg N/ha within a season. Another 31-67 kg N/ha of inorganic N in soil was not utilised by wheat or lupin. Annual net N mineralisation ranged from 80 to 130 kg N, confirming the high rate of decomposition of organic matter in the sandy soil. Mineralisation over summer and autumn, when crop and pastures were not grown, supplied ~25% of the inorganic N produced in soil profiles in 1995 and 20-40% in1996. The study indicated that legumes used in rotations with cereals on deep sands were able to add adequate organic N to soil to insure rates of net N mineralisation sufficient to support cereal yieldsin excess of current shire averages. However, in practice, the asynchrony in supply and demand for N resulted in the inefficient use of soil-derived N by wheat.

An evaluation of 15N methods for estimating nitrogen fixation in a subterranean clover-perennial ryegrass sward

1983 ◽  
Vol 34 (4) ◽  
pp. 391 ◽  
Author(s):  
FJ Bergersen ◽  
GL Turner
Keyword(s):  
Nitrogen Fixation ◽  
Perennial Ryegrass ◽  
N2 Fixation ◽  
Slow Growth ◽  
Subterranean Clover ◽  
Natural Abundance ◽  
Nitrogen Accumulation ◽  
Plant Parts ◽  
Natural Enrichment

Nitrogen (N2) fixation by nodulated subterranean clover, in swards with perennial ryegrass, was studied by using the natural abundance of 15N in sward components compared with a method using artificial enrichment of the soil with small amounts of K15NO3. Significant differences between the 15N concentrations in ryegrass and clover enabled yield-independent estimates of the proportion (P) of clover nitrogen fixed from atmospheric N2. Yield-dependent estimates of P were also made during intervals of growth in autumn and in spring. Values of P increased with time and during spring were close to l00%, when maximum fixation rates were approximately 4 kg N ha-1 day-1. Consistent differences in 15N concentration of shoots and roots had little effect on P. Early in the experiment, natural enrichment gave lower estimates of P than 15NO-3 -enriched treatments. Yield-independent and yield-dependent methods gave similar estimates of P. During winter, when no net growth or nitrogen accumulation was recorded, there appeared to be loss of 15N from the plants, possibly because of loss of highly labelled plant parts, balanced by slow growth of tissue containing a lower 15N concentration. During winter, calculation of P was therefore unreliable.

Effect of Leaf Removal on Symbiotic Nitrogen Fixation in Peanut1

1983 ◽  
Vol 10 (2) ◽  
pp. 107-110 ◽  
Author(s):  
A. K. Osman ◽  
J. C. Wynne ◽  
G. H. Elkan ◽  
T. J. Schneeweis
Keyword(s):  
Nitrogen Fixation ◽  
N2 Fixation ◽  
Nitrogenase Activity ◽  
Correlation Coefficients ◽  
Dry Weight ◽  
Nodule Formation ◽  
Growing Period ◽  
Arachis Hypogaea L ◽  
Defoliation Treatment ◽  
C 50

Abstract The effect of varying levels of leaf defoliation on the nodulation and nitrogen fixation of a Virginia and a spanish-type peanut (Arachis hypogaea L.) cultivar was investigated in the greenhouse. Five leaf defoliation treatments - (a) control (no leaflet removal), (b) 25%, (c) 50%, (d) 75%, and (e) 100% - were carried out every 3 to 5 days throughout the growing period. All nitrogen fixation measurements were affected by the defoliation (leaflet removal) treatments. Increased leaf defoliation reduced nodule formation and N2 fixation. The reduction in plant dry weight, nodule number, nodule dry weight, and nitrogenase activity was most severe for the 100% defoliation treatment. Correlation coefficients (r) of N2 fixation measurements and leaf areas and weights were highly significant. The defoliation effect was similar in both experiments and cultivars; however, the Virginia type achieved higher values for all N2 fixation measurements.

scholarly journals Seeds with high molybdenum concentration improved growth and nitrogen acquisition of rhizobium-inoculated and nitrogen-fertilized common bean plants

2013 ◽  
Vol 37 (2) ◽  
pp. 367-378 ◽  
Author(s):  
Fernanda Fátima Delgado Almeida ◽  
Adelson Paulo Araújo ◽  
Bruno José Rodrigues Alves
Keyword(s):  
Nitrate Reductase ◽  
Common Bean ◽  
N2 Fixation ◽  
Nitrogenase Activity ◽  
N Fertilizer ◽  
Growth Stages ◽  
Mineral N ◽  
N Sources ◽  
Bean Plants ◽  
Common Bean Plants

Seeds of common bean (Phaseolus vulgaris) with high molybdenum (Mo) concentration can supply Mo plant demands, but to date no studies have concomitantly evaluated the effects of Mo-enriched seeds on plants inoculated with rhizobia or treated with N fertilizer. This work evaluated the effects of seed Mo on growth and N acquisition of bean plants fertilized either by symbiotic N or mineral N, by measuring the activities of nitrogenase and nitrate reductase and the contribution of biological N2 fixation at different growth stages. Seeds enriched or not with Mo were sown with two N sources (inoculated with rhizobia or fertilized with N), in pots with 10 kg of soil. In experiment 1, an additional treatment consisted of Mo-enriched seeds with Mo applied to the soil. In experiment 2, the contribution of N2 fixation was estimated by 15N isotope dilution. Common bean plants grown from seeds with high Mo concentration flowered one day earlier. Seeds with high Mo concentration increased the leaf area, shoot mass and N accumulation, with both N sources. The absence of effects of Mo application to the soil indicated that Mo contents of Mo-enriched seeds were sufficient for plant growth. Seeds enriched with Mo increased nitrogenase activity at the vegetative stage of inoculated plants, and nitrate reductase activity at late growth stages with both N sources. The contribution of N2 fixation was 17 and 61 % in plants originating from low- or high-Mo seeds, respectively. The results demonstrate the benefits of sowing Mo-enriched seeds on growth and N nutrition of bean plants inoculated with rhizobia or fertilized with mineral N fertilizer.

Translocation of Manganese in Subterranean Clover (Trifolium subterraneum L. Cv. Seaton Park). II. Effect of Leaf Senescence and of Restricting Supply of Manganese to Part of a Split Root System

1984 ◽  
Vol 11 (2) ◽  
pp. 113 ◽  
Author(s):  
RO Nable ◽  
JF Loneragan
Keyword(s):  
Root System ◽  
Dry Matter ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Mature Leaves ◽  
Split Root ◽  
Split Root System ◽  
Number Of Leaves ◽  
Visual Abnormalities ◽  
Mn Concentrations

Split root systems were used to examine the hypothesis that manganese is not mobile in the phloem of subterranean clover plants during vegetative growth. The effect of senescence on manganese mobility was also examined by shading mature leaves. Plants given a luxury supply of radioactive manganese to one half of a split root system failed to translocate any more than a trace of manganese to the other half. Shading and subsequent senescence of a large number of leaves did not cause movement of manganese from them. Omitting an external supply of manganese depressed growth of roots but produced no visual abnormalities even though Mn concentrations decreased to 5 �g/g dry matter of root.

scholarly journals Growth of Crotalaria juncea L. supplied with mineral nitrogen

2005 ◽  
Vol 48 (2) ◽  
pp. 181-185 ◽  
Author(s):  
Elenira Henrique Miranda Mendonça ◽  
Marlene Aparecida Schiavinato
Keyword(s):  
Nitrogen Fixation ◽  
Nutrient Solution ◽  
Nitrogenase Activity ◽  
Mineral Nitrogen ◽  
Mineral N ◽  
Crotalaria Juncea ◽  
N Content

Plants of Crotalaria juncea inoculated with Rhizobium were treated with nutrient solution containing 10 or 20mg of either N/NO3 or N/NH4.plant-1.week-1 . The control plants received nutrient solution without N. An investigation was conducted on the effect of these sources of N on growth and nitrogen fixation of plants with 30, 60 and 90 days after sowing (DAS). Those that received mineral N presented higher growth than -N plants, but the presence of nodules occurred in all the treatments. Plants treated with NH4 presented higher N content until 60 days. The highest concentrations of leghemoglobin and protein in nodules were found at 30 DAS and there was no difference in leghemoglobin content between treatments for any age and in protein from 60 DAS. Nitrogenase activity did not vary from 60 to 90 days, with the exception of plants that received 20mg N/NO3, where it was higher at 60 days

scholarly journals The Quorum Sensing Auto-Inducer 2 (AI-2) Stimulates Nitrogen Fixation and Favors Ethanol Production over Biomass Accumulation in Zymomonas mobilis

2021 ◽  
Vol 22 (11) ◽  
pp. 5628
Author(s):  
Valquíria Campos Alencar ◽  
Juliana de Fátima dos Santos Silva ◽  
Renata Ozelami Vilas Boas ◽  
Vinícius Manganaro Farnézio ◽  
Yara N. L. F. de Maria ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Quorum Sensing ◽  
Ethanol Production ◽  
N2 Fixation ◽  
Energy Demand ◽  
Zymomonas Mobilis ◽  
Biomass Accumulation ◽  
High Energy ◽  
Gram Negative ◽  
Expression Of Genes

Autoinducer 2 (or AI-2) is one of the molecules used by bacteria to trigger the Quorum Sensing (QS) response, which activates expression of genes involved in a series of alternative mechanisms, when cells reach high population densities (including bioluminescence, motility, biofilm formation, stress resistance, and production of public goods, or pathogenicity factors, among others). Contrary to most autoinducers, AI-2 can induce QS responses in both Gram-negative and Gram-positive bacteria, and has been suggested to constitute a trans-specific system of bacterial communication, capable of affecting even bacteria that cannot produce this autoinducer. In this work, we demonstrate that the ethanologenic Gram-negative bacterium Zymomonas mobilis (a non-AI-2 producer) responds to exogenous AI-2 by modulating expression of genes involved in mechanisms typically associated with QS in other bacteria, such as motility, DNA repair, and nitrogen fixation. Interestingly, the metabolism of AI-2-induced Z. mobilis cells seems to favor ethanol production over biomass accumulation, probably as an adaptation to the high-energy demand of N2 fixation. This opens the possibility of employing AI-2 during the industrial production of second-generation ethanol, as a way to boost N2 fixation by these bacteria, which could reduce costs associated with the use of nitrogen-based fertilizers, without compromising ethanol production in industrial plants.

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