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1.
Renata Matraszek 《Acta Physiologiae Plantarum》2008,30(3):361-370
The author studied the effect of different nickel concentrations (0, 0.4, 40 and 80 μM Ni) on the nitrate reductase (NR) activity
of New Zealand spinach (Tetragonia expansa Murr.) and lettuce (Lactuca sativa L. cv. Justyna) plants supplied with different nitrogen forms (NO3
−–N, NH4
+–N, NH4NO3). A low concentration of Ni (0.4 μM) did not cause statistically significant changes of the nitrate reductase activity in
lettuce plants supplied with nitrate nitrogen (NO3
−–N) or mixed (NH4NO3) nitrogen form, but in New Zealand spinach leaves the enzyme activity decreased and increased, respectively. The introduction
of 0.4 μM Ni in the medium containing ammonium ions as a sole source of nitrogen resulted in significantly increased NR activity
in lettuce roots, and did not cause statistically significant changes of the enzyme activity in New Zealand spinach plants.
At a high nickel level (Ni 40 or 80 μM), a significant decrease in the NR activity was observed in New Zealand spinach plants
treated with nitrate or mixed nitrogen form, but it was much more marked in leaves than in roots. An exception was lack of
significant changes of the enzyme activity in spinach leaves when plants were treated with 40 μM Ni and supplied with mixed
nitrogen form, which resulted in the stronger reduction of the enzyme activity in roots than in leaves. The statistically
significant drop in the NR activity was recorded in the aboveground parts of nickel-stressed lettuce plants supplied with
NO3
−–N or NH4NO3. At the same time, there were no statistically significant changes recorded in lettuce roots, except for the drop of the
enzyme activity in the roots of NO3
−-fed plants grown in the nutrient solution containing 80 μM Ni. An addition of high nickel doses to the nutrient solution
contained ammonium nitrogen (NH4
+–N) did not affect the NR activity in New Zealand spinach plants and caused a high increase of this enzyme in lettuce organs,
especially in roots. It should be stressed that, independently of nickel dose in New Zealand spinach plants supplied with
ammonium form, NR activity in roots was dramatically higher than that in leaves. Moreover, in New Zealand spinach plants treated
with NH4
+–N the enzyme activity in roots was even higher than in those supplied with NO3
−–N. 相似文献
2.
In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO3−, NH4+, or both at equimolar concentrations (500 μM). Plants supplied with only NO3− had lower growth rates (0.17 ± 0.01 g g−1 d−1), shorter roots, smaller leaves with less chlorophyll than plants supplied with NH4+ alone or in combination with NO3− (RGR = 0.28 ± 0.01 g g−1 d−1). Ammonium was the preferred form of N taken up. The maximal rate of NH4+ uptake (Vmax) was 6–14 times higher than the maximal uptake rate of NO3− and the minimum concentration for uptake (Cmin) was lower for NH4+ than for NO3−. Plants supplied with NO3− had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO3− was primarily reduced in the roots, but NRA levels were generally low (<4 μmol NO2− g−1 DW h−1). Under natural growth conditions NH4+ is probably the main N source for S. natans, but plants probably also exploit NO3− when NH4+ concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH4+ levels in the water, even though the uptake capacity for NO3− is reduced under these conditions. 相似文献
3.
David Bryan Dail David Y. Hollinger Eric A. Davidson Ivan Fernandez Herman C. Sievering Neal A. Scott Elizabeth Gaige 《Oecologia》2009,160(3):589-599
In N-limited ecosystems, fertilization by N deposition may enhance plant growth and thus impact C sequestration. In many N
deposition–C sequestration experiments, N is added directly to the soil, bypassing canopy processes and potentially favoring
N immobilization by the soil. To understand the impact of enhanced N deposition on a low fertility unmanaged forest and better
emulate natural N deposition processes, we added 18 kg N ha−1 year−1 as dissolved NH4NO3 directly to the canopy of 21 ha of spruce-hemlock forest. In two 0.3-ha subplots, the added N was isotopically labeled as
15NH4
+ or 15NO3
− (1% final enrichment). Among ecosystem pools, we recovered 38 and 67% of the 15N added as 15NH4
+ and 15NO3
−, respectively. Of 15N recoverable in plant biomass, only 3–6% was recovered in live foliage and bole wood. Tree twigs, branches, and bark constituted
the most important plant sinks for both NO3
− and NH4
+, together accounting for 25–50% of 15N recovery for these ions, respectively. Forest floor and soil 15N retention was small compared to previous studies; the litter layer and well-humified O horizon were important sinks for
NH4
+ (9%) and NO3
− (7%). Retention by canopy elements (surfaces of branches and boles) provided a substantial sink for N that may have been
through physico-chemical processes rather than by N assimilation as indicated by poor recoveries in wood tissues. Canopy retention
of precipitation-borne N added in this particular manner may thus not become plant-available N for several years. Despite
a large canopy N retention potential in this forest, C sequestration into new wood growth as a result of the N addition was
only ~16 g C m−2 year−1 or about 10% above the current net annual C sequestration for this site. 相似文献
4.
Carbon-14 pulse labeling technique was used to study the effect of rooting medium salinity and form and availability of N
on growth and rhizodeposition of wheat (Triticum aestivum L.). Thirty days old plants grown in continuously aerated Arnon and Hoagland nutrient solution were subjected to 14C pulse labeling for 24 h and transferred to aqueous rooting medium containing 0, 150, and 300 mM NaCl in all combinations
with different forms (calcium nitrate, ammonium sulphate, and ammonium nitrate) and amounts (0.5, 1.0, 1.5, and 2.0 times
the standard N concentration (150 ppm) of Arnon and Hoagland plant growth medium). Plant samples immediately after pulse labeling,
following 7 days of growth under different rooting medium conditions, and the freeze-dried rooting medium were analyzed for
total C and 14C. Length and fresh/dry weight of root and shoot portions and calculated values of unaccounted 14C were determined. Presence of NaCl in the rooting medium led to a decrease in root and shoot portions. However, NO3
−-fed plants showed better growth than NH4
+-fed plants at all the three salinity levels. Salinity in rooting medium led to higher rhizodeposition and lower loss of 14C. Relatively higher proportion of 14C was released as rhizodeposits and retained in root/shoot portions of plants fed with NH4
+ or NH4
++NO3
−, than those with NO3
−, while less was respired. The specific activity of the rhizodeposits (kBq 14C g−1 C) was also higher under saline conditions. The rhizodeposits in NH4
+-fed plants were more highly labeled as compared to NO3
−-plants. 相似文献
5.
Nitrogen relations of natural and disturbed tropical plant communities in northern Australia (Kakadu National Park) were
studied. Plant and soil N characteristics suggested that differences in N source utilisation occur at community and species
level. Leaf and xylem sap N concentrations of plants in different communities were correlated with the availability of inorganic
soil N (NH+
4 and NO−
3). In general, rates of leaf NO−
3 assimilation were low. Even in communities with a higher N status, including deciduous monsoon forest, disturbed wetland,
and a revegetated mine waste rock dump, levels of leaf nitrate reductase, xylem and leaf NO−
3 levels were considerably lower than those that have been reported for eutrophic communities. Although NO−
3 assimilation in escarpment and eucalypt woodlands, and wetland, was generally low, within these communities there was a suite
of species that exhibited a greater capacity for NO−
3 assimilation. These “high- NO−
3 species” were mainly annuals, resprouting herbs or deciduous trees that had leaves with high N contents. Ficus, a high-NO−
3 species, was associated with soil exhibiting higher rates of net mineralisation and net nitrification. “Low-NO−
3 species” were evergreen perennials with low leaf N concentrations. A third group of plants, which assimilated NO−
3 (albeit at lower rates than the high-NO−
3 species), and had high-N leaves, were leguminous species. Acacia species, common in woodlands, had the highest leaf N contents of all woody species. Acacia species appeared to have the greatest potential to utilise the entire spectrum of available N sources. This versatility in
N source utilisation may be important in relation to their high tissue N status and comparatively short life cycle. Differences
in N utilisation are discussed in the context of species life strategies and mycorrhizal associations.
Received: 5 July 1997 / Accepted: 13 July 1998 相似文献
6.
Poornananda Madhava Naik Shirugumbi Hanamanthagouda Manohar Hosakatte Niranjana Murthy 《Acta Physiologiae Plantarum》2011,33(4):1553-1557
The present work deals with optimization of adventitious shoot culture of Bacopa monnieri for the production of biomass and bacoside A and has investigated the effects of macro elements (NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4) and nitrogen source [NH4
+/NO3
−] of Murashige and Skoog (Physiol Plant 15:473–497, 1962) medium (MS) on accumulation of biomass and bacoside A content. Optimum number of adventitious shoots (99.33 shoots explant−1), fresh weight (1.841 g) and dry weight (0.150 g) were obtained in the medium with 2.0× strength of NH4NO3. The highest production of bacoside A content was also recorded in the medium of 2.0× NH4NO3, which produced 17.935 mg g−1 DW. The number of adventitious shoot biomass and bacoside A content were optimum when the NO3
− concentration was higher than that of NH4
+. Maximum number of shoots (70.00 shoots explant−1), biomass (fresh weight 1.137 g and dry weight 0.080 g) and also bacoside A content (27.106 mg g−1 DW) were obtained at NH4
+/NO3
− ratio of 14.38/37.60 mM. Overall, MS medium supplemented with 2.0× NH4NO3 is recommended for most efficient bacoside A production. 相似文献
7.
This study examined changes in dissolved organic nitrogen (DON) and dissolved inorganic nitrogen (DIN) in coastal seawater
after exposure to sand along a high energy beach face over an annual cycle between April 2004 and July 2005. Dissolved organic
nitrogen, NO3
−, and NH4
+ were released from sand to seawater in laboratory incubation experiments clearly demonstrating that they are a potential
source of N to underlying groundwater or coastal seawater. DON increases in seawater, after exposure to surface sands in laboratory
experiments, were positively correlated with in situ water column DON concentrations measured at the same time as sand collection.
Increase in NO3
− and NH4
+ were not correlated with their in situ concentrations. This suggests that DON released from beach sands is relatively more
recalcitrant while NO3
− and NH4
+ are utilized rapidly in the coastal ocean. The release of N was seasonal with carbon to nitrogen ratios indicating that
recent primary productivity was responsible for the largest fluxes in summer while more degraded humic material contributed
to lower fluxes in winter. Fluxes of total dissolved nitrogen (DON and DIN) from surface sand (2.1 × 10−4 mol m−2 h−1) were similar to that of groundwater and more than an order of magnitude larger than rain deposition indicating the potential
importance of surface sand derived nitrogen to the coastal zone with a corresponding impact on primary productivity. 相似文献
8.
A sand-culture experiment was conducted to study the influence of a deficiency of and an excess of micronutrients on the uptake
and assimilation of NH
4
+
and NO
3
−
ions by maize. By studying the fate of15N supplied as15NH4NO3 or NH4
15NO3, it was demonstrated that in maize plants NH4−N was absorbed in preference to NO
3
−
−N. The uptake and distribution of N originating from both NH
4
+
and NO
3
−
was considerably modified by deficiency of, or an excess of, micronutrients in the growth medium. The translocation of NH
4
+
−N from roots to shoots was relatively less than that of NO
3
−
−N. Deficiency as well as excessive amounts of micronutrients, in the growth medium, substantially reduced the translocation
of absorbed N into protein. This effect was more pronounced in the case of N supplied as NO
3
−
. Amino-N was the predominant non-protein fraction in which N from both NH
4
+
and NO
3
−
tended to accumulate. The next important non-protein fractions were NO
3
−
−N when N was supplied as NO
3
−
and amide-N when NH
4
+
was the source. The relative accumulation of15N into different protein fractions was also a function of imposed micronutrient levels. 相似文献
9.
Praveen Nagella Hosakatte Niranjana Murthy 《Plant Cell, Tissue and Organ Culture》2011,104(1):119-124
Withania somnifera is an important medicinal plant that contains withanolides and withaferins, both bioactive compounds. We have tested the
effects of macroelements and nitrogen source in W. somnifera cell suspension cultures with the aim of optimizing the production of biomass and withanolide A. The effects of the macroelements
NH4NO3, KNO3, CaCl2, MgSO4 and KH2PO4 at concentrations of 0.0, 0.5, 1.0, 1.5 and 2.0× strength and of the nitrogen source [NH4
+/NO3
− (mM/mM) ratio of: 0.00/18.80, 7.19/18.80, 14.38/18.80, 21.57/18.80, 28.75/18.80, 14.38/0.00, 14.38/9.40, 14.38/18.80, 14.38/28.20,
and 14.38/37.60 (mM)] in Murashige and Skoog medium were tested for biomass and withanolide A production. The highest accumulation
of biomass [147.81 g l−1 fresh weight (FW) and 14.02 g l−1 (dry weight (DW)] was recorded in the medium containing a 0.5× concentration of NH4NO3, and the highest production of withanolide A content was recorded in the medium with 2.0× KNO3 (4.36 mg g−1 DW). The NH4
+/NO3
− ratio also influenced cell growth and withanolide A production, with both parameters being larger when the NO3
− concentration was higher than that of NH4
+. Maximum biomass growth (110.45 g l−1 FW and 9.29 g l−1 DW) was achieved at an NH4
+/NO3
− ratio of 7.19/18.80, while withanolide A production was greatest (3.96 mg g−1 DW) when the NH4
+/NO3
− ratio was 14.38/37.60 mM. 相似文献
10.
Supplying both N forms (NH4
++NO3
−) to the maize (Zea mays L.) plant can optimize productivity by enhancing reproductive development. However, the physiological factors responsible
for this enhancement have not been elucidated, and may include the supply of cytokinin, a growth-regulating substance. Therefore,
field and gravel hydroponic studies were conducted to examine the effect of N form (NH4
++NO3
− versus predominantly NO3
−) and exogenous cytokinin treatment (six foliar applications of 22 μM 6-benzylaminopurine (BAP) during vegetative growth versus untreated) on productivity and yield of maize. For untreated plants,
NH4
++NO3
− nutrition increased grain yield by 11% and whole shoot N content by 6% compared with predominantly NO3
−. Cytokinin application to NO3
−-grown field plants increased grain yield to that of NH4
++NO3
−-grown plants, which was the result of enhanced dry matter partitioning to the grain and decreased kernel abortion. Likewise,
hydroponically grown maize supplied with NH4
++NO3
− doubled anthesis earshoot weight, and enhanced the partitioning of dry matter to the shoot. NH4
++NO3
− nutrition also increased earshoot N content by 200%, and whole shoot N accumulation by 25%. During vegetative growth, NH4
++NO3
− plants had higher concentrations of endogenous cytokinins zeatin and zeatin riboside in root tips than NO3
−-grown plants. Based on these data, we suggest that the enhanced earshoot and grain production of plants supplied with NH4
++NO3
− may be partly associated with an increased endogenous cytokinin supply. 相似文献
11.
Sampling spatial and temporal variation in soil nitrogen availability 总被引:18,自引:0,他引:18
There are few studies in natural ecosystems on how spatial maps of soil attributes change within a growing season. In part,
this is due to methodological difficulties associated with sampling the same spatial locations repeatedly over time. We describe
the use of ion exchange membrane spikes, a relatively nondestructive way to measure how soil resources at a given point in
space fluctuate over time. We used this method to examine spatial patterns of soil ammonium (NH+
4) and nitrate (NO−
3) availability in a mid-successional coastal dune for four periods of time during the growing season. For a single point in
time, we also measured soil NH+
4 and NO−
3 concentrations from soil cores collected from the mid-successional dune and from an early and a late successional dune. Soil
nitrogen concentrations were low and highly variable in dunes of all ages. Mean NH+
4 and NO−
3 concentrations increased with the age of the dune, whereas coefficients of variation for NH+
4 and NO−
3 concentrations decreased with the age of the dune. Soil NO−
3 concentration showed strong spatial structure, but soil NH+
4 concentration was not spatially structured. Plant-available NH+
4 and NO−
3 showed relatively little spatial structure: only NO−
3 availability in the second sampling period had significant patch structure. Spatial maps of NH+
4 and NO−
3 availability changed greatly over time, and there were few significant correlations among soil nitrogen availability at different
points in time. NO−
3 availability in the second sampling period was highly correlated (r = 0.90) with the initial soil NO−
3 concentrations, providing some evidence that patches of plant-available NO−
3 may reappear at the same spatial locations at irregular points in time.
Received: 20 February 1998 / Accepted: 23 November 1998 相似文献
12.
M. Vuletić V. Hadži-Tašković Šukalović K. Marković J. Dragišić Maksimović 《Biologia Plantarum》2010,54(3):530-534
The activities of antioxidative enzymes and contents of proline and total phenolics were assayed in roots of two maize (Zea mays L.) genotypes grown in a medium containing nitrate (NO3
−) or both nitrogen forms, nitrate and ammonium (NH4
+/NO3
−). An increase in the activities of class III peroxidases (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), ascorbate
oxidase (AO) and proline content, and decrease in phenolic content were observed in NH4
+/NO3
− in comparison with NO3
− grown plants. When polyethylene glycol (PEG) was added to both nitrogen treatments, the content of total phenolics and proline
was increased, especially in NH4
+/NO3
− treatment. The PEG treatment decreased enzyme activities in NH4
+/NO3
− grown plants, but in NO3
− grown plants activities of POD and SOD were increased, opposite to decreased APX and AO. Isoelectric focusing demonstrated
increased activities of acidic POD isoforms in PEG treated NO3
− grown plants, and lower activities of both, acidic and basic isoforms in NH4
+/NO3
−grown plants. 相似文献
13.
Metabolic regulation and gene expression of root phosphoenolpyruvate carboxylase by different nitrogen sources 总被引:3,自引:1,他引:2
S. Pasqualini L. Ederli C. Piccioni P. Batini M. Bellucci S. Arcioni & M. Antonielli 《Plant, cell & environment》2001,24(4):439-447
Alfalfa (Medicago sativa L.) N-sufficient plants were fed 1·5 mM N in the form of NO3−, NH4+ or NO3− in conjunction with NH4+, or were N-deprived for 2 weeks. The specific activity of phosphoenolpyruvate carboxylase (PEPC) from the non-nodulated roots of N-sufficient plants was increased in comparison with that of N-deprived plants. The PEPC value was highest with NO3− nutrition, lowest with NH4+ and intermediate in plants that were fed mixed salts. The protein was more abundant in NO3−-fed plants than in either NH4+- or N mixed-fed plants. Nitrogen starvation decreased the level of PEPC mRNA, and nitrate was the N form that most stimulated PEPC gene expression. The malate content was significantly lower in NO3−-deprived than in NO3−-sufficient plants. Root malate accumulation was high in NO3−-fed plants, but decreased significantly in plants that were fed with NH4+. The effect of malate on the desalted enzyme was also investigated. Root PEPC was not very sensitive to malate and PEPC activity was inhibited only by very high concentrations of malate. Asparagine and glutamine enhanced PEPC activity markedly in NO3−-fed plants, but failed to affect plants that were either treated with other N types or N starved. Glutamate and citrate inhibited PEPC activity only at optimal pH. N-nutrition also influenced root nitrate and ammonium accumulation. Nitrate accumulated in the roots of NO3−- and (NO3− + NH4+)-fed plants, but was undetectable in those administered NH4+. Both the nitrate and the ammonium contents were significantly reduced in NO3−- and (NO3− + NH4+)-starved plants. Root accumulation of free amino acids was strongly influenced by the type of N administered. It was highest in NH4+-fed plants and the most abundant amides were asparagine and glutamine. It was concluded that root PEPC from alfalfa plants is N regulated and that nitrate exerts a strong influence on the PEPC enzyme by enhancing both PEPC gene expression and activity. 相似文献
14.
Growth, chemical composition, and nitrate reductase activity (NRA) of hydroponically cultured Rumex crispus, R. palustris, R. acetosa, and R. maritimus were studied in relation to form (NH4
+, NO3
-, or both) and level of N supply (4 mM N, and zero-N following a period of 4mM N). A distinct preference for either NH4
+ or NO3
- could not be established. All species were characterized by a very efficient uptake and utilization of N, irrespective of
N source, as evident from high concentrations of organic N in the tissues and concurrent excessive accumulations of free NO3
- and free NH4
+. Especially the accumulation of free NH4
+ was unusually large.
Generally, relative growth rate (RGR) was highest with a combination of NH4
+ and NO3
-. Compared to mixed N supply, RGR of NO3
-- and NH4
+-grown plants declined on average 3% and 9%, respectively. Lowest RGR with NH4
+ supply probably resulted from direct or indirect toxicity effects associated with high NH4
+ and/or low Ca2+ contents of tissues. NRA in NO3
- and NH4NO3 plants was very similar with maxima in the leaves of ca 40 μmol NO2
- g-1 DW h-1. ‘Basal’ NRA levels in shoot tissues of NH4
+ plants appeared relatively high with maxima in the leaves of ca 20 μmol NO2
- g-1 DW h-1. Carboxylate to organic N ratios, (C-A)/Norg, on a whole plant basis varied from 0.2 in NH4
+ plants to 0.9 in NO3
- plants.
After withdrawal of N, all accumulated NO3
- and NH4
+ was assimilated into organic N and the organic N redistributed on a large scale. NRA rapidly declined to similar low levels,
irrespective of previous N source. Shoot/root ratios of -N plants were 50–80% lower than those from +N plants. In comparison
with +N, RGR of -N plants did not decline to a large extent, decreasing by only 15% in -NH4
+ plants due to very high initial organic-N contents. N-deprived plants all exhibited an excess cation over anion uptake (net
proton efflux), and whole-plant (C-A)/Norg ratios increased to values around unity.
Possible difficulties in interpreting the (C-A)/Norg ratio and NRA of plants in their natural habitats are briefly discussed. 相似文献
15.
Preference for NH4+ or NO3− nutrition by the perennial legume Sesbania sesban (L.) Merr. was assessed by supplying plants with NH4+ and NO3− alone or mixed at equal concentrations (0.5 mM) in hydroponic culture. In addition, growth responses of S. sesban to NH4+ and NO3− nutrition and the effects on root nodulation and nutrient and mineral composition of the plant tissues were evaluated in a hydroponic setup at a range of external concentration of NH4+ and NO3− (0, 0.1, 0.2, 0.5, 2 and 5 mM). Seedlings of S. sesban grew equally well when supplied with either NH4+ or NO3− alone or mixed and had high relative growth rates (RGRs) ranging between 0.19 and 0.21 d−1. When larger plants of S. sesban were supplied with NH4+ or NO3− alone, the RGRs and shoot elongation rates were not affected by the external concentration of inorganic N. At external N concentrations up to 0.5 mM nodulation occurred and contributed to the N nutrition through fixation of gaseous N2 from the atmosphere. For both NH4+ and NO3−-fed plants the N concentration in the plant tissues, particularly water-extractable NO3−, increased at high supply concentrations, and concentrations of mineral cations generally decreased. It is concluded that S. sesban can grow without an external inorganic N supply by fixing atmospheric N2 gas via root nodules. Also, S. sesban grows well on both NH4+ and NO3− as the external N source and the plant can tolerate relatively high concentrations of NH4+. This wide ecological amplitude concerning N nutrition makes S. sesban very useful as a N2-fixing fallow crop in N deficient areas and also a candidate species for use in constructed wetland systems for the treatment of NH4+ rich waters. 相似文献
16.
Effect of nitrogen form and phosphorus source on the growth,nutrient uptake and rhizosphere soil property of Camellia sinensis L. 总被引:1,自引:0,他引:1
The effects of nitrogen form and phosphorus source on the growth, nutrient uptake and rhizosphere soil property of tea (Camellia sinensis L.) were investigated in a pot experiment. The experiment was performed with a compartmental cropping device, which enables
the collection of rhizosphere soil at defined distances from the root of tea plant. Nitrogen was supplied as nitrate or ammonium
in combination with soluble phosphorus as Ca(H2PO4)2 or insoluble P as rock phosphate. The leaf dry matter production of tea was significantly greater in the treatments with
NH4
+ than NO3
-, whereas dry matter production of root and stem was not significantly affected. Addition of phosphorus as either source did
not influence the dry matter production. The concentrations of K in root, Mg and Ca in both the shoot and root supplied with
NO3
- were significantly higher than in NH4
+ and influence of P sources was minor. On the contrary, Al and Mn concentrations were significantly larger in NH4
--fed plants which could be attributed to remarkably increased availability of Al and Mn caused by acidification of the rhizosphere
soil (the first 1-mm soil section from the root surface) with NH4–N nutrition. The concentration of N in shoot was also significantly higher in NH4- than in NO3-fed plants, indicating higher use efficiency of NH4–N. Whatever the phosphate source, rhizosphere pH declined in ammonium compared to in nitrate treatment. The pH decrease was
much larger when no P or soluble P were applied and reached 0.85–1.30 units which extended to 3–5 mm away from the root surface.
Exchangeable acidity, content of exchangeable Al and Mn were also considerably higher in the rhizosphere soils of NH4
+ fed tea plants. Significant amounts of P dissolved from rock phosphate accumulated in rhizosphere of NH4
+, not NO3
-, suggesting that the dissolution of rock phosphate was induced by the proton excreted by tea root fed with ammonium. With
soluble P addition, shoot and root P concentrations were greater in NH4
+ than in NO3
- treatment and it appeared that this difference could not be sufficiently explained by the available P content in soil which
was only slightly higher in NH4
+ treatment. With rock phosphate addition, the shoot and root P concentrations were hardly affected by nitrogen form, although
the available P content was much higher and accumulated in the rhizosphere soil supplied with ammonium. The reason for this
was discussed with regard to the inter-relationship of Al with P uptake.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Abstract Tomato plants (Lycopersicon esculentum Mill. cv. San Marzano), grown in dilute nutrient solutions containing (in meq ˙ 1-1) 0.5 NaNO3, 0.5 NH4NO3 or 0.25 (NH4)2 SO4 as the nitrogen source, were detopped for collection of xylem sap and measurement of trans-root electrical potentials. The plant parts and the xylem exudate were subsequently analysed for mineral content. The commonly observed effects of NH4+ were noted, including reduction of calcium concentration in the xylem sap, and of calcium content in stems and leaves, compared with NO3-fed plants. This effect was attributed principally to the less negative trans-root electrical potential measured in NH4+-fed plants, and the resultant reduction of inward driving force on passively moving divalent cations. 相似文献
18.
Water culture, growth chamber, greenhouse and field experiments were conducted to compare the effect of NH4−N and NO3−N on yield and N uptake of rapeseed (Brassica campestris L.). In water culture, the yields of 28-day old rapeseed plants grown at 14 μg N ml−1 were double with NO3 compared to NH4, but N uptake was little affected. There was no such effect when concentration was reduced to 3.5 or 7 μg N ml−1. The yield and N uptake of 26-day old rapeseed grown on six soils (pH 4.6 to 6.5) in pots in a growth chamber were much greater
with NO3 than with NH4, although N concentration was more in the NH4- than the NO3-grown plants. In a greenhouse experiment with rapeseed grown on 12 potted soils, the N uptake of applied N was greater with
NO3 than with NH4 on all soils. Averages were 63% with NH4 and 78% with NO3. However, NH4-fixation capacities of the soils were only weakly correlated with yield from the two sources of N (r=0.48) and the relation
was similar with N uptake. In contrast to the behavior of water culture, growth chamber and greenhouse experiments, the 33
field experiments did not show consistent difference in seed yield with NH4 and NO3 applied at time of seeding. In nine field experiments where band application was used for Ca(NO3)2, (NH4)2 SO4, NH4 NO3, yield tended to be greatest for (NH4)2SO4. However, in 19 experiments on acid soils with and without lime, yields in most cases were similar with (NH4)2SO4 and NH4 NO3. Nitrification inhibitors were added to spring banded NH4-based fertilizers in five experiments, but the yields were not influenced.
Scientific Paper No. 558, Lacombe Research Station, Agriculture Canada. 相似文献
19.
20.
Soil-mixing effects on inorganic nitrogen production
and consumption in forest and shrubland soils 总被引:1,自引:0,他引:1
Soils that are physically disturbed are often reported to show net nitrification and NO3− loss. To investigate the response of soil N cycling rates to soil mixing, we assayed gross rates of mineralization, nitrification, NH4+ consumption, and NO3− consumption in a suite of soils from eleven woody plant communities in Oregon, New Mexico, and Utah. Results suggest that the common response of net NO3− flux from disturbed soils is not a straightforward response of increased gross nitrification, but instead may be due to the balance of several factors. While mineralization and NH4+ assimilation were higher in mixed than intact cores, NO3− consumption declined. Mean net nitrification was 0.12 mg N kg−1 d−1 in disturbed cores, which was significantly higher than in intact cores (−0.19 mg N kg−1 d−1). However, higher net nitrification rates in disturbed soils were due to the suppression of NO3− consumption, rather than an increase in nitrification. Our results suggest that at least in the short term, disturbance may significantly increase NO3− flux at the ecosystem level, and that N cycling rates measured in core studies employing mixed soils may not be representative of rates in undisturbed soils. 相似文献