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Nitrogen fixation

About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.


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TL;DR: Analysis of the specificity of interactions between different plant genotypes and bacterial strains (via two-factor analysis of variance) demonstrates the strain-specific plant polygenes are of a special importance in controlling the intensity of nitrogen fixation.
Abstract: Leguminous crops are genetically polymorphous for the balance between symbiotrophic and combined types of nitrogen nutrition. In pea, polebean, alfalfa and fenugreek the wild-growing populations and local varieties exceed the agronomically advanced cultivars in the activity of N2 fixation that occurs in symbiosis with nodule bacteria (rhizobia). Combined nitrogen nutrition ensures higher productivity than symbiotrophic one in the “old” leguminous crops (pea, alfalfa, common vetch, polebean, soybean), while the symbiotrophic type dominates in some “young” crops (hairy vetch, kura clover, goat's rue). An importance is emphasized of using the symbiotically active wild-growing genotypes as the initial material for breeding the legume cultivars. The data on high heritability (broad sense, narrow sense, realized) of the legume symbiotic activity demonstrate that the plant selection for this activity may be highly effective. A range of methods to select the legumes for an improved symbiotic activity is available including plant growth in N-depleted substrates, analysis of nodulation scores, direct (“isotopic”) and indirect (acetylene reduction) estimation of nitrogenase activity. Analysis of the specificity of interactions between different plant genotypes and bacterial strains (via two-factor analysis of variance) demonstrates the strain-specific plant polygenes are of a special importance in controlling the intensity of nitrogen fixation. Therefore, a coordinated plant-bacteria breeding is required to create the optimal combinations of partners' genotypes. Selection and genetic construction of the commercially attractive rhizobia strains should involve improvement of nitrogen fixing, nodulation and competitive abilities expressed in combination with the symbiotically active plant genotypes, Breeding of the leguminous crops for the preferential nodulation by highly active rhizobia strains, for the ability to support N2 fixation under moderate N fertilization levels and to ensure a sufficient energy supply of symbiotrophic nitrogen nutrition is required

110 citations

Journal ArticleDOI
TL;DR: Nitrogen fixation in the rhizospheres of field grown tropical forage grasses was studied by the acetylene reduction method and values varied considerably between sites but indicate the possible economic importance of several of the species studied.
Abstract: Nitrogen fixation in the rhizospheres of field grown tropical forage grasses was studied by the acetylene reduction method Values varied considerably between sites but indicate the possible economic importance of several of the species studied Maximal nitrogenase activity measured (nmoles C 2 H 4 g −1 dry roots h −1 ) was 754 for Pennisetum purpureum , 750 for Brachiaria mutica , 341 for Digitaria decumbens , 299 for Panicum maximum , 283 for Paspalum notatum , 269 for Cynodon dactylon , 41 for Melinis minutiflora and 29 for Hyparrhenia rufa Nitrogenase activity varied considerably with season and was maximal during active vegetative growth of two of the grasses Significant differences between Paspalum notatum ecotypes and cultivars in Azotohacter paspali occurrence and nitrogen fixation, indicate the possibility of plant breeding to enhance nitrogen fixation in grass rhizospherc associations Other research lines of agronomic importance are fertilizer effects In intact soil plant cores with the Paspalum system 10 parts/10 6 NH 4 + J-N inhibited nitrogenase activity within 2 h and 10 parts/10 6 NO − 3 -N within 4 h but after 1 week these effects were negligible In the field, nitrogenase activity on roots of P purpureum and D decumbens , assayed 2 weeks after top dressings of 20 kg N ha −1 as NH 4 NO 3 was not affected even after eight such dressings

110 citations

Journal ArticleDOI
TL;DR: In this article, the process of ammonia fixation has been studied in three well characterized and structurally diverse fulvic and humic acid samples, and liquid phase 15N NMR spectrometry was performed on the samples before and after reaction with ammonium hydroxide.

109 citations

Journal ArticleDOI
TL;DR: Whether commercially grown chickpea and faba bean crops in the northern grain belt of New South Wales were depleting, maintaining or enhancing soil N fertility, and whether current farm management practices were maximising the N2 fixation potential of the crops were established.
Abstract: Summary. Nitrogen (N 2 ) fixation accords pulse crops the potential to sustain or enhance total soil nitrogen (N) fertility. However, regional field experiments have shown that this potential is often not realised because N 2 fixation is inhibited by the supply of nitrate N in the root zone (0‐90 cm) coupled with a low demand for N during plant growth. The objectives of this study were to establish whether commercially grown chickpea and faba bean crops in the northern grain belt of New South Wales were depleting, maintaining or enhancing soil N fertility, and whether current farm management practices were maximising the N 2 fixation potential of the crops. Fifty-one rainfed crops of chickpea (Cicer arietinumL.) and faba bean (Vicia faba L.) were surveyed in the Moree, Walgett and Gunnedah districts of north-west New South Wales during the winters of 1994 and 1995. Nitrogen fixation was measured using the natural 15 N abundance technique. Net N balance was calculated for each crop by subtracting grain N harvested from fixed N 2 . Soil, plant and fallow conditions with potential to influence N 2 fixation were also documented. The percentage of crop N derived from N 2 fixation (P fix ) ranged from 0 to 81% for chickpea and 19 to 79% for faba bean. Nitrogen fixation of chickpea was uniformly low in the 1994 drought. Total N 2 fixed ranged from 0 to 99 kg/ha for chickpea and 15 to 171 kg/ha for faba bean. Net N balance ranged from ‐ 47 to +46 kg N/ha for chickpea crops, and ‐12 to +94 kg N/ha for faba bean crops. About 60% of the difference in P fix between chickpea and faba bean at the average level of soil nitrate (65 kg/ha) was explained by the higher N demand of the latter. The remaining 40% could be due to greater tolerance of the faba bean symbiosis to nitrate effects. In addition, faba bean had a lower N harvest index than chickpea, which meant that proportionally less N needed to be fixed by faba bean to offset removal of grain N. On average, P fix needed to exceed 35% for chickpea and 19% for faba bean to balance soil N. The equivalent soil nitrate levels were 43 kg nitrate N/ha for chickpea and 280 kg/ha for faba bean (extrapolated from the relationship between measured P fix and soil nitrate). Double-cropping chickpea into summer cereal or grass pasture stubble provided the most consistent strategy for achieving the low levels of soil nitrate.

109 citations

Journal ArticleDOI
TL;DR: The results indicate that the losses of fixed carbon from the nodulated roots of legumes are likely to be substantial, and that the respiratory costs of fixing nitrogen may vary with the specific biochemistry of the bacteroid.
Abstract: Soyabean, cowpea, and white clover, inoculated with effective rhizobia, were grown singly with a standard mineral nutrition and light regime in controlled environments until seed maturation (in soyabean and cowpea) or late vegetative growth (white clover). Day/night temperature regimes were 23/18, 30/24, and 20/15 °C in soyabean, cowpea, and white clover, respectively. The respiratory losses of C02 from the nodulated root systems were studied in relation to the concurrent rate of fixation of atmospheric nitrogen. Despite differences in development, the effectiveness of the symbioses, and the temperature of growth, all three legumes exhibited similar respiratory losses from nodulated roots per unit of nitrogen fixed. During intense nitrogen fixation, the average respiratory losses for the three legumes varied between 6-3 and 6-8 mg C rng"1 N; within each species, the losses varied more widely at different stages of development. These respiratory burdens reflect the total cost to the plant of the nodule/nitrogen fixation syndrome including the subtending roots. The results are discussed in relation to the respiratory effluxes from nodules and roots, and to biochemical investigations of the costs of nitrogen fixation. INTRODUCTION Studies of the biochemistry of biological nitrogen fixation have repeatedly emphasized the energy-intensive nature of the reduction of the dinitrogen molecule to ammonia (Bulen and LeComte, 1966; Winter and Burris, 1968; Bergersen, 1971; Hardy and Havelka, 1975). Furthermore, there is increasing evidence that a proportion of the reducing power generated at the nitrogenase of the legume nodule may be utilized in the formation of hydrogen from protons (Dixon, 1968, 1972; Schubert and Evans, 1976; Schubert, Engelke, Russell, and Evans, 1977) and, moreover, that not many agricultural legume symbioses possess the appropriate biochemistry to recapture some or all of this energy—if indeed it can be recaptured (Evans, Ruiz-Argiieso, and Russell, 1978). Such studies indicate that the losses of fixed carbon from the nodulated roots of legumes are likely to be substantial, and that the respiratory costs of fixing nitrogen may vary with the specific biochemistry of the bacteroid. 1 The Grassland Research Institute is financed through the Agricultural Research Council. This content downloaded from 157.55.39.143 on Wed, 15 Jun 2016 04:50:37 UTC All use subject to http://about.jstor.org/terms 136 Ryle, Powell, and Gordon—Nitrogen Fixation and Respiration This paper reports experiments designed to measure the respiratory losses of fixed carbon from the nodulated roots of three legumes, soyabean, cowpea, and white clover, during their normal cycle of growth. The three legumes were deliberately chosen to provide contrasts in habit, growth cycle, geographical origin, and symbiotic effectiveness. All three were grown in the same light and nutritional conditions but the temperatures were selected to reflect their geographical origin. A detailed account of the carbon economy of the soyabean plants has been published elsewhere (Ryle, Powell, and Gordon, 1978). The respiratory losses of carbon from the nodulated root systems of the three legumes are considered in relation to their concurrent rates of fixation of atmospheric nitrogen. MATERIALS AND METHODS Plants of Fiskeby V soyabean (Glycine max (L.) Merr.), cowpea ( Vigna unguiculata (L.) Walp.) var. K28O9, and white clover (Trifolium repens L.) var. Blanca were grown singly in 9-5 cm diameter pots of Perlite. Seeds of soyabean and cowpea were sterilized with u.v. radiation and inoculated with Nitrogerm Rhizobium CB 1809 and CB 756. respectively, suspended in a sucrose milk-peat mixture. After sterilization with u.v. radiation, seeds of white clover were sown in shallow dishes of Perlite, inoculated at germination with Rothamsted Rhizobium 5 suspended in distilled water, and transplanted to pots at the time of emergence of the first leaf. They were subsequently reinoculated with the same Rhizobium about 7 d after transplantation. All plants were grown in Saxcil growth cabinets which provided a photoperiod of 12 h of light from daylight fluorescent tubes (soyabean only) or from daylight fluorescent tubes plus incandescent lamps (810 ± 10 /?Einsteins m~2 s_1: Lamda PAR meter). An automatic C02 injection system prevented the C02 levels from falling below 320 parts 10~6. Day/night temperature regimes were 23/18 °C (soyabean), 30/24 °C (cowpea), and 20/15 °C (white clover). All plants were provided daily with a nutrient solution containing essential macroand micronutrients with the exception of nitrogen (Ryle et al., 1978), which was normally completely absent. It proved impossible to grow cowpea and white clover from germination without any combined nitrogen, and so some nitrate nitrogen (20 parts 10~6) was added to these plants until the nodules developed leghaemoglobin, after which nitrate was completely withdrawn. As the plants increased in size the amount of nutrient solution provided was progressively increased to a maximum of 400 ml d_l per plant. Measurements of respiration were made by enclosing groups of plants (2-4, according to size) in Perspex chambers of up to 50 1 capacity, through which outside air was passed. Samples of air were drawn off before and after passing through the chamber and their C02 contents compared in an infrared gas analyser. The chamber was enclosed in a Saxcil cabinet adjusted to provide the appropriate temperature. Initially whole plants were held in the dark for 30-40 min at a temperature midway between that of day and night (e.g. in soyabean at 20-5 °C) for the effect of temperature to become stabilized. Subsequently, the plants were removed from the chamber, decapitated at Perlite level, returned to the chamber, and a measurement taken of the respiration of the nodulated root. The porous nature of the Perlite rooting medium ensured rapid equilibration of gas exchange. At intervals the validity of the decapitated root measurements was tested separately by comparison with root respiration measurements made on intact plants. Plants were removed from their pots and their roots gently shaken free of Perlite, and then sealed into 1 1 bottles of dilute nutrient solution with a 5 cm air gap immediately beneath the base of the shoots. Approximately 400 ml min-1 of outside air was bubbled through the solution continuously. After allowing 1-2 h for equilibration, respiration of the enclosed root system was determined by comparing the C02 content of the air with an infrared gas analyser before and after its passage through the solution. On some occasions, a second measurement of respiration was made after some of the more accessible nodules had been removed from the nodulated root system. The rate of respiration of the nodules removed from the nodulated root system could then be calculated by difference. Furthermore, after detaching the remaining nodules and determining their weight, the rate of respiration of root could also be calculated. These tests with intact plants indicated that the respiration of nodulated roots was generally unaffected for 30-60 min following decapitation, after which it usually declined. This content downloaded from 157.55.39.143 on Wed, 15 Jun 2016 04:50:37 UTC All use subject to http://about.jstor.org/terms Ryle, Powell, and Gordon—Nitrogen Fixation and Respiration 137 Cowpea was particularly sensitive in this respect and the respiration of its root system often began to decrease only 15-20 min after decapitation. Measurements of nodulated root respiration were made between the second and tenth hour of the photoperiod and, whenever possible, were successively rotated from early to late in the photoperiod at consecutive observations to eliminate potential bias. For the same reason, temperatures midway between those of day and night were chosen for the measurements so as to provide a mean rate of respiration as far as possible representative of a whole diurnal period. Ancillary measurements of root performance with decapitated plants and with sealed root systems both indicated that diurnal fluctuations in the rate of respiration (Fig. 1) and of acetylene reduction (Fig. 5) largely reflected the cycling of temperature in the rooting medium.

109 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023390
2022831
2021263
2020240
2019250
2018261