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1.
Summary The rate of flow and nitrate and phosphorus content of the water from four drained sandy and clayey plots of size 12×60 m
cropped to continuous corn were determined following two annual applications of different rates (0, 260, 390 and 520 kg N/ha)
of cow manure slurry. The drain flow was directly related to the rainfall and was greatly influenced by soil texture. The
N losses were greater in 1972 (7.8 to 19.1 kg N/ha) than in 1971 (0.4 to 7.8 kg N/ha) because of more summer rainfall. Nitrogen
and phosphorus losses were larger from the sandy plots than from the clayey plots. The manure application rates had no apparent
effect on nitrogen losses in the drain water. 相似文献
2.
Victor M. Luque-Almagro Verity J. Lyall Stuart J. Ferguson M. Dolores Roldán David J. Richardson Andrew J. Gates 《The Journal of biological chemistry》2013,288(41):29692-29702
Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression. 相似文献
3.
Studies were conducted to compare N mineralization rates in salt-amended nonsaline soils to naturally-occurring saline soils.
NaCl, CaCl2, and Na2SO4 were added to nonsaline soils at rates that produced electrical conductivities of the saturation extracts (ECe) of 5, 10, 15, and 20 dS m−1. Saline soils with similar properties were leached to the same ECc levels. N mineralization in the Chino soil was inhibited by salt addition, particularly with sodium and calcium chlorides.
In the Domino soil there was some inhibition of N mineralization with the chloride salts, but enhancement with Na2SO4 was observed. Nitrification in both soils was more sensitive to salt addition than ammonification.
N mineralization occurred more slowly in both leached saline soils compared to the salt-amended soils. Leached saline soils
often accumulated greater amounts of inorganic N compared to their native saline counterparts, particularly with the 5 dS
m−1 Chino soil (native, 44 dS m−1) and with the 5, 10, 15 and 20 dS m−1 Domino soils (native, 32 dS m−1). Kinetic parameters were estimated by the linear least squares (LLS) and the nonlinear least squares (NLLS) methods. Generally,
the LLS transformation estimated greater values of potentially mineralizable N (No) and lower rate constants (k). With the NLLS equation, No values for the leached saline soils were usually lower, and k values usually higher than in the salt-amended soils. The nonsaline
controls generally had the highest No and lowest k estimates. Average LLS rate constants for the salt-amended and leached saline soils were 0.055 and 0.083 for
the Chino, and 0.104 and 0.137 week−1, respectively, for the Domino soils. With the NLLS equation, average k values for the salt-amended and leached saline soils
were 0.087 and 0.089 for the Chino, and 0.181 and 0.387 week−1, respectively, for the Domino soils. These results suggest that N mineralization rates obtained in salt-amended nonsaline
soils may not be representative of those in naturally-occurring saline soils. 相似文献
4.
The relationship between nitrification potential and nitrogen accumulation was studied in an early successional sere on Mt.
Fuji. Soil organic nitrogen accumulated with the invasion ofPolygonum cuspidatum and successively withMiscanthus oligostachyus and other species. Laboratory incubation experiments showed a higher nitrification potential at theM. oligostachyus state. The numbers of nitrifying bacteria increased with the progress of succession. No significant difference in nitrate
reductase activity was found between pioneer and succeeding species. The soil solution at theM. oligostachyus stage contained a lower level of nitrate than rainwater, while that of the bare ground and theP. cuspidatum stage contained a higher nitrate level than rainwater. It was concluded that the high nitrate levels in the soil solution
of the bare ground and theP. cuspidatum stage were due to lower nitrate-absorbing activity, leading to loss of nitrogen with precipitation, while the lower nitrate
levels at theM. oligostachyus stage when higher nitrification activity occurred were due to higher nitrate-absorbing activity, preventing net loss of nitrogen
from the ecosystem. 相似文献
5.
A. G. McEwan H. G. Wetzstein O. Meyer J. B. Jackson S. J. Ferguson 《Archives of microbiology》1987,147(4):340-345
The periplasmic dissimilatory nitrate reductase from Rhodobacter capsulatus N22DNAR+ has been purified. It comprises a single type of polypeptide chain with subunit molecular weight 90,000 and does not contain heme. Chlorate is not an alternative substrate. A molybdenum cofactor, of the pterin type found in both nitrate reductases and molybdoenzymes from various sources, is present in nitrate reductase from R. capsulatus at an approximate stoichiometry of 1 molecule per polypeptide chain. This is the first report of the occurrence of the cofactor in a periplasmic enzyme. Trimethylamine-N-oxide reductase activity was fractionated by ion exchange chromatography of periplasmic proteins. The fractionated material was active towards dimethylsulphoxide, chlorate and methionine sulphoxide, but not nitrate. A catalytic polypeptide of molecular weight 46,000 was identified by staining for trimethylamine-N-oxide reductase activity after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The same polypeptide also stained for dimethylsulphoxide reductase activity which indicates that trimethylamine-N-oxide and dimethylsulphoxide share a common reductase.Abbreviations DMSO
dimethylsulphoxide
- LDS
lithium dodecyl sulphate
- MVH
reduced methylviologen
- PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulphate
- TMAO
trimethylamine-N-oxide 相似文献
6.
Summary Two annual species of Bromus, an invader (B. hordeaceus, ex B. mollis) and a non-invader (B. intermedius), were grown for 28 days in growth chambers, at 5 and 100 M NO
3
-
in flowing nutrient solution. No differences between the two species were observed at either NO
3
-
level, in terms of relative growth rate (RGR) or its components, dry matter partitioning, specific NO
3
-
absorption rate, nitrogen concentration, and other characteristics of NO
3
-
uptake and photosynthesis. The effects of decreasing NO
3
-
concentration in the solution were mainly to decrease the NO
3
-
concentration in the plants through decreased absorption rate, and to decrease the leaf area ratio through increased specific leaf mass and decreased leaf mass ratio. Organic nitrogen concentration varied little between the two treatments, which may be the reason why photosynthetic rates were not altered. Consequently, RGR was only slightly decreased in the 5-M treatment compared to the 100-M treatment. This is in contrast with other species, where growth is reduced at much higher NO
3
-
concentrations. These discrepancies may be related to differences in RGR, since a log-linear relationship was found between RGR and the NO
3
-
concentration at which growth is first reduced. In addition, a strong linear relationship was found between the RGR of these species and their maximum absorption rate for nitrate, suggesting that the growth of species with low maximum RGR may be partly regulated by nutrient uptake. 相似文献
7.
Effect of simulated forest fire on the availability of N and P in mediterranean soils 总被引:4,自引:0,他引:4
The effect of soil burning on N and P availability and on mineralization and nitrification rates of N in the burned mineral
soil was studied by combustion of soils in the laboratory.
At a fire temperature of 600°C, there was a complete volatilization of NH4 and a significant increase of pH, from 7.6 in the unburned soil to 11.7 in the burned soil. Under such conditions ammonification
and nitrification reactions were inhibited. Less available P was produced immediately after the fire at 600°C, as compared
to P amount produced at 250°C. Burning the soils with plants caused a decrease in NH4-N and (NO2+NO3)-N concentrations in the soil as well as a reduction in ammonification and nitrification rates. Combustion of soil with plants
contributed additional available P to the burned soil.
The existence of a non-burned soil under the burned one played an important role in triggering ammonification and nitrification
reactions. 相似文献
8.
Nitrate reduction in roots and shoots and exchange of reduced N between organs were quantitatively estimated in intact 13-d-old seedlings of two-row barley (Hordeum vulgare L. cv. Daisengold) using the 15N-incorporation model (A. Gojon et al. (1986) Plant Physiol. 82, 254–260), except that NH
+
4
was replaced by NO
-
2
. N-depleted seedlings were exposed to media containing both nitrate (1.8 mM) and nitrite (0.2 mM) under a light-dark cycle of 12:12 h at 20°C; the media contained different amounts of 15N labeling. Experiments were started either immediately after the beginning (expt. 1) or immediately prior to the end (expt. 2) of the light period, and plants were sampled subsequently at each light-dark transition throughout 36 h. The plants effectively utilized 15NO
-
3
and accumulated it as reduced 15N, predominantly in the shoots. Accumulation of reduced 15N in both experiments was nearly the same at the end of the experiment but the accumulation pattern in roots and shoots during each 12-h period differed greatly depending on time and the light conditions. In expt. 1, the roots accounted for 31% (light), 58% (dark), and 9% (light) of nitrate reduction by the whole plants, while in expt. 2 the contributions of the root were 82% (dark), 20% (light), and 29% (dark), during each of the three 12-h periods. Xylem transport of nitrate drastically decreased in the dark, but that of reduced N rather increased. The downward translocation of reduced 15N increased while nitrate reduction in the root decreased, whereas upward translocation decreased while nitrate reduction in the shoot increased. We conclude that the cycling of reduced N through the plant is important for N feeding of each organ, and that the transport system of reduced N by way of xylem and phloem, as well as nitrate reduction by root and shoot, can be modulated in response to the relative magnitude of reduced-N demands by the root and shoot, with the one or the other predominating under different circumstances.Symbols Anl
accumulation of reduced 15N from 15NO
-
3
in 14NO
-
3
-fed roots of divided root system
- Ar
accumulation in root of reduced 15N from 15NO
-
3
- As
accumulation in shoot of reduced 15N from 15NO
-
3
- Rr
15NO
-
3
reduction in root
- Rs
15NO
-
3
reduction in shoot
- Tp
translocation to root of shoot-reduced 15N from 15NO
-
3
in phloem
- Tx
translocation to shoot of root-reduced 15N from 15NO
-
3
in xylem 相似文献
9.
Seasonal and inter-annual variations of nitrogen diagenesis in the sediments of a recently impounded basin 总被引:2,自引:2,他引:0
The Méry-sur-Oise (France) storage reservoir is an artificial basin of 9 m average depth, fed by water from the river Oise with a mean residence time of about 4 days. Sediments are accumulating at a rate of about 0.7 cm/month. In the sediments, two fractions of organic nitrogen with different rates of bacterial degradation could be distinguished, one associated with fresh phytoplankton, the other made of detrital and more refractory compounds. The fluxes of oxygen, nitrate and ammonium across the sediment-water interface were measured with a bell-jar system at different seasons during a 3 year period following flooding of the basin. The measurements show clear seasonal variations in relation with the variations of temperature and input of fresh phytoplanktonic material to the sediment. In addition, a long term trend of increasing ammonium was observed. Measurements were also carried out after dredging of all accumulated sediments of the basin. They showed a considerable reduction of the flux of nitrate to the sediments and a significant reduction of the flux of ammonium to the water column.These results are interpreted in the light of a non stationary model of N diagenesis in accumulating sediments. This model is able to predict at least the general trends of benthic N cycling of basins during the early stage of their ecological succession. 相似文献
10.
Citrobacter freundii, Paracoccus denitrificans and Pseudomonas stutzeri were grown either singly or in mixed culture in anaerobic nitrate or nitrite limited chemostats with formate and/or succinate as electron donors and carbon sources. C. freundii reduced nitrate or nitrite stoichiometrically to ammonia. Maximum molar growth yields for nitrate (nitrite) were 15.3 (9.9) g/mol for C. freundii on formate with succinate as carbon source, 15.3 (9.5) g/mol for Ps. stutzeri on succinate and 32.3 (20.4) g/mol for Pa. denitrificans on succinate. The almost identical growth yields indicate that the ATP output of the anaerobic processes in the nitrate (nitrite) ammonifying organism and Ps. stutzeri are nearly the same. In mixed cultures with either Ps. stutzeri or Pa. denitrificans, C. freundii was the best competitor for nitrate. These results show that in anaerobic environments C. freundii may compete successfully with denitrifying organisms. 相似文献