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1.
Shoji Ohkuma Sakae Shimizu Masahiko Noto Yoshimichi Sai Kuninori Kinoshita Hiro-Omi Tamura 《In vitro cellular & developmental biology. Animal》1993,29(11):862-866
Summary Bafilomycin A1, a potent selective inhibitor of vacuolar H+-ATPase, inhibited the growth of a variety of cultured cells dose-dependently, including golden hamster embryo and NIH-3T3
fibroblasts, whether or not they were transformed, and PC12 and HeLa cells. The concentration of bafilomycin A1 for 50% inhibition of cell growth ranged from 10 to 50 nM. The dose response was nearly parallel with that of the bafilomycin A1-induced lysosomal pH increase. The degree of pH increase for growth inhibition produced by bafilomycin A1 was similar to that produced by NH4Cl in which little difference was recognized in effect among cell types. 相似文献
2.
The loss of nitrogen (N) from field-applied animal manure through ammonia (NH3) volatilisation and nitrous oxide (N2O) emission is of major environmental concern. Both lime and dicyandiamide (DCD) have been suggested as amendments that can
mitigate N2O emissions, but simultaneously increase the risk of NH3 volatilisation. This study evaluated the impact of lime and DCD on NH3 and N2O emissions following application of liquid hog manure. Hydrated lime (Ca(OH)2) was added to an acidic soil to achieve three pH levels (4.7, 6.3 and 7.4). Soil samples (100 g) were then placed in 500
ml screw-top Mason-jars and de-ionised water was added to bring the samples to 50, 70 and 90% water-filled pore space (WFPS).
Slurry was applied at a rate equivalent to 116,000 l ha−1, while DCD was applied at 30% of the NH4-N rate applied. Jars were sealed and incubated at 21°C for 21 d. Ammonia volatilisation was quantified using boric acid traps,
while N2O gas concentration was analysed using gas chromatography. Dicyandiamide had no effect (P>0.05) on either NH3 or N2O emissions. Both NH3 and N2O emissions increased (P<0.05) as WFPS increased, with emissions ranging from 0.9 to 1.4 kg NH3-N ha−1 and 123 to 353 g N2O-N ha−1, respectively. Liming decreased (P<0.01) N2O emissions from 547 to 46 g N2O-N ha−1, but increased (p<0.01) NH3 volatilisation from 0.36 to 1.92 kg NH3-N ha−1. Results suggest that liming to a pH ≥6.3 can reduce N2O emissions, however, this reduction will be accompanied by a substantial loss of NH3.
Section Editor: H. Lambers 相似文献
3.
免耕稻田氮肥运筹对土壤NH3挥发及氮肥利用率的影响 总被引:2,自引:0,他引:2
通过大田试验,设置5种不同的施肥比例(基肥:分蘖肥:拔节肥:穗肥-2:2:3:3(R1)、3:2:2:3(R2)、4:2:2:2(R3)、4:3:1:2(R4)与0:0:0:0(CK)),研究氮肥运筹对稻田NH3挥发和氮肥利用率的影响。结果表明,(1)相对于不施肥,施肥显著提高了稻田NH3挥发量。氮肥施用后,NH3挥发损失量占施氮量的6.2%-8.5%,其中,以分蘖期NH3挥发损失量最大,齐穗期次之,苗期和拔节期最小。施肥处理间,处理R1稻田累积NH3挥发量最小,显著低于其它施肥处理,比处理R2、R3和R4分别低9.1%(P<0.05)、10.9%(P<0.05)和17.7%(P<0.05)。(2)相关分析表明,田面水NH4+、pH值和土壤NH4+和pH值均与稻田土壤NH3挥发通量呈显著或者极显著相关;(3)处理R1水稻氮肥利用率相对于处理R2、R3和R4增加了28.4%(P<0.05)、55.4%(P<0.05)和74.9%(P<0.05)。研究表明,氮肥后移能有效降低免耕稻田NH3挥发,提高水稻的氮肥利用率。 相似文献
4.
We investigated the effects on ginseng adventitious root growth and ginsenoside production when macro-element concentrations
and nitrogen source were manipulated in the culture media. Biomass growth was greatest in the medium supplemented with 0.5-strength
NH4PO3, whereas ginsenoside accumulation was highest (9.90 mg g-1 DW) in the absence of NH4PO3. At levels of 1.0-strength KNO3, root growth was maximum, but a 2.0 strength of KNO3 led to the greatest ginsenoside content (9.85 mg g-l). High concentrations of MgSO4 were most favorable for both root growth and ginsenoside accumulation (up to 8.89 mg g-1 DW). Root growth and ginsenoside content also increased in proportion to the concentration of CaCI2 in the medium, with the greatest accumulation of ginsenoside (8.91 mg g-1 DW) occurring at a 2.0 strength. The NH4/NO3
-- ratio also influenced adventitious root growth and ginsenoside production; both parameters were greater when the NO3
- concentration was higher than that of NH4
+. Maximum root growth was achieved at an NH4
+/NO3
- ratio of 7.19/18.50, while ginsenoside production was greatest (83.37 mg L-1) when NO3
- was used as the sole N source. 相似文献
5.
Effect of activated charcoal and 6-benzyladenine on in vitro nitrogen uptake by Lagerstroemia indica 总被引:1,自引:0,他引:1
A sterile hydroponic culture system suitable for studying nitrogen (N) uptake ofLagerstroemia indica L.in vitro was developed. Four different treatments were assayed: with and without activated charcoal (AC and NAC, respectively), with
and without 50 μM of 6-benzyladenine (+BA and −BA, respectively). Medium pH, electrical conductivity (EC), NO3
− and NH4
+ concentrations were measured weekly. At the end of the culture, propagules were sampled and SPAD indices, and shoot and root
fresh weights were determined. Explants grown in media with activated charcoal were able to take up both NO3
− and NH4
+, although NH4
+ uptake was lower. Subsequently the pH of the media was maintained between 5.5–6.0. In treatments with no addition of activated
charcoal, NH4
+ uptake was preferential and the pH dropped to 3.1. Explants in these conditions were unable to raise the pH by taking up
NO3
−, especially when root morphogenesis was inhibited by addition of BA. Supply of this PGR produced root growth inhibition,
which was almost complete in the treatment without activated charcoal. This component significantly reduced the inhibitory
effect of 50 μM BA on root growth.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
The influence of nitrogen concentration and ammonium/nitrate ratio on N-uptake,mineral composition and yield of citrus 总被引:9,自引:0,他引:9
In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH4
+ at a higher rate than NO3
–. Maximum NO3
– uptake by the whole plant occurred at 120 mg L–1 NO3
–-N, whereas NH4
+ absorption was saturated at 240 mg L–1 NH4
+-N. 15NH4
+ accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO3
– was mostly partitioned between leaves and roots.Adding increasing amounts of unlabeled NH4
+ (15–60 mg L–1 N) to nutrient solutions containing 120 mg L–1 N as 15N labeled nitrate reduced 15NO3
– uptake. Maximum inhibition of 15NO3
– uptake was about 55% at 2.14 mM NH4
+ (30 mg L–1 NH4
+-N) and it did not increase any further at higher NH4
+ proportions.In a long-term experiment, the effects of concentration and source of added N (NO3
– or NH4
+) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH4
+ versus NO3
– nutrition, whereas the reverse was true for Ca, K, Zn and Mn.The effects of different NO3
–-N:NH4
+-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L–1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO3
– or NH4
+ as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO3
–-N/NH4
+-N ratio. With increasing proportions of NH4
+ in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH4
+, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO3
–-N:NH4
+-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH4
+ in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO3
–:NH4
+ ratio. 相似文献
7.
为探讨氮沉降对九寨沟藓类植物的影响,该研究以当地优势藓类植物锦丝藓(Actinothuidium hookeri)和塔藓(Hylocomium splendens)为对象,以NH4NO3为氮源,设置对照(0 kg N·hm-2·a-1)、低浓度(20 kg N·hm-2·a-1)、高浓度(50 kg N·hm-2·a-1)3种处理,开展为期6个月的氮沉降模拟实验。结果表明:(1)氮沉降处理导致两种藓类植物的活性氧、丙二醛、叶绿素、脯氨酸和可溶性蛋白含量显著增加,同时锦丝藓过氧化氢酶、过氧化物酶、超氧化物歧化酶、抗坏血酸过氧化物酶活性增加。(2)对于生长旺期和生长末期的塔藓,氮沉降导致其过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶活性降低。(3)锦丝藓的综合隶属函数值随氮沉降浓度增大而增加,在生长旺期和生长末期,塔藓综合隶属函数值对氮沉降的响应存在差异。综上认为,两种藓类植物对氮沉降处理的生理响应存在差异,高浓度氮沉... 相似文献
8.
Summary The purpose of this study was to investigate the phytotoxicity of nitrapyrin 2-chloro-6-(trichloromethyl)pyridine to sunflower
(Helianthus annuus L.) under different N regimes and to see if N forms affect the phytotoxicity of nitrapyrin. Sunflower was grown in pot culture
for 21 days and was fertilized with (NH4)2SO4, NH4NO3 and NaNO3 to provide 0, 100 and 200 ppm N and with nitrapyrin application of 0 and 20 ppm. All N-treated sunflower plants in all N
regimes and regardless of titrapyrin treatment produced more root and shoot dry weights and contained a significantly higher
N than untreated check. Nitrapyrin toxicity appeared as a curling of leaf margin and a tendril type of stem growth, the visible
toxicity symptoms decreased in the order: (NH4)2SO4>NH4NO3>NaNO3. Furthermore nitrapyrin addition suppressed sunflower growth in each N regime, the suppressing effect being greater with
(NH4)2SO4 and NH4NO3 than as with NaNO3. Although, shoot growth from plants receiving nitrapyrin was not significantly affected by any N regime, root growth of nitrapyrin-treated
plants was somewhat restricted by NH4
+−N nutrition relative to NO3
−−N nutrition. 相似文献
9.
Three columns were differentiated with feeding mixture of H2S and NH3 (MFC), feeding NH3 followed by H2S (NFC), and feeding H2S followed by NH3 (SFC). Removal performance, biodegradation capacity and microbial community structures in the three columns were compared. The results show that NFC has a shorter acclimation period for the removal of NH3 gas and nitrification than MFC. Under the high loading of H2S and NH3 at 164 and 82 g m−3 h−1, respectively, NFC exhibited high removal efficiency of NH3 (>95%) while the removal efficiencies were obtained at 63 and 75% in MFC and SFC, respectively. The removal of NH3 gas in NFC was significantly attributed to nitrification (over 50%), while adsorption and chemical reaction contributed to the removal of NH3 in MFC and SFC. The different biodegradation capacities of NH3 could be due to the dissimilarity in the microbial population presented in each column. 相似文献
10.
Yield of S-adenosylmethionine was improved significantly in recombinant Pichia pastoris by controlling NH4
+ concentration. The highest production rate was 0.248 g/L h when NH4
+ concentration was 450 mmol/L and no repression of cell growth was observed. Within very short induction time (47 h), 11.63 g/L
SAM was obtained in a 3.7 L bioreactor. 相似文献
11.
Growth inhibition by ammonia and use of a pH-controlled feeding strategy for the effective cultivation of Mycobacterium chlorophenolicum 总被引:1,自引:0,他引:1
The inhibitory effect of ammonia on the growth of the polychlorinated xenobiotic-degrading bacterium Mycobacterium chlorophenolicum was examined. The strain is inhibited by both the ionized and nonionized forms of ammonia. At pH 6.9 50% reduction of the growth rate was observed at 6.8 g l–1 total ammonium. For 23 experiments performed in shake-flask culture at different pH values and ammonium concentrations a growth model based on the extended Monod kinetic fits the data with a deviation of 5.3%. To overcome growth inhibition in bioreactors a pH-controlled feeding strategy was developed for effective cultivation of M. chlorophenolicum at an ammonium level below 0.3 g l–1. The ammonium addition was controlled on-line by the stoichiometric interdependence of ammonium consumption and pH decline. With this on-line control strategy a biomass concentration as high as 26.2 g l–1 can be achieved within less than 1 week of cultivation, compared to a biomass concentration of 15.5 g l–1 in normal batch culture after 2 weeks of cultivation. The yield is also increased from 0.32 g to 0.43 g biomass (g glucose)–1. The strategy developed provides an effective method for the production of biomass of M. chlorophenolicum serving as the inoculum in remediation technologies. 相似文献
12.
The kinetics of NH4
+ and NO3
− uptake in young Douglas fir trees (Pseudotsuga menziesii [Mirb.] Franco) were studied in solutions, containing either one or both N species. Using solutions containing a single N
species, the Vmax of NH4
+ uptake was higher than that of NO3
− uptake. The Km of NH4
+ uptake and Km of NO3
− uptake differed not significantly. When both NH4
+ and NO3
− were present, the Vmax for NH4
+ uptake became slightly higher, and the Km for NH4
+ uptake remained in the same order. Under these conditions the NO3
− uptake was almost totally inhibited over the whole range of concentrations used (10–1000 μM total N). This inhibition by NH4
+ occurred during the first two hours after addition. ei]{gnA C}{fnBorstlap} 相似文献
13.
Camañes G Bellmunt E García-Andrade J García-Agustín P Cerezo M 《Journal of plant physiology》2012,169(3):268-274
Our results show that AtNRT2.1 expression has a positive effect on the NH4+ ion influx, mediated by the HATS, as also occurs with AtAMT1.1 expression on the NO3− ion influx. AtNRT2.1 expression plays a key role in the regulation of AtAMT1.1 expression and in the NH4+ ion influx, differentiating the nitrogen source, and particularly, the lack of it. Nitrogen starvation produces a compensatory effect by AtAMT1.1 when there is an absence of the AtNRT2.1 gene. Our results also show that, in the atnrt2 mutant lacking both AtNRT2.1 and AtNRT2.2, gene functions present different kinetic parameters on the NH4+ ion influx mediated by the HATS, according to the source and availability of nitrogen. Finally, the absence of AMT1.1 also produces changes in the kinetic parameters of the NO3− influx, showing different Vmax values depending on the source of nitrogen available. 相似文献
14.
Raif Musa-Aziz Lihong Jiang Li-Ming Chen Kevin L. Behar Walter F. Boron 《The Journal of membrane biology》2009,228(1):15-31
Others have shown that exposing oocytes to high levels of (10–20 mM) causes a paradoxical fall in intracellular pH (pHi), whereas low levels (e.g., 0.5 mM) cause little pHi change. Here we monitored pHi and extracellular surface pH (pHS) while exposing oocytes to 5 or 0.5 mM NH3/NH4
+. We confirm that 5 mM causes a paradoxical pHi fall (−ΔpHi ≅ 0.2), but also observe an abrupt pHS fall (−ΔpHS ≅ 0.2)—indicative of NH3 influx—followed by a slow decay. Reducing [NH3/NH4
+] to 0.5 mM minimizes pHi changes but maintains pHS changes at a reduced magnitude. Expressing AmtB (bacterial Rh homologue) exaggerates −ΔpHS at both levels. During removal of 0.5 or 5 mM NH3/NH4
+, failure of pHS to markedly overshoot bulk extracellular pH implies little NH3 efflux and, thus, little free cytosolic NH3/NH4
+. A new analysis of the effects of NH3 vs. NH4
+ fluxes on pHS and pHi indicates that (a) NH3 rather than NH4
+ fluxes dominate pHi and pHS changes and (b) oocytes dispose of most incoming NH3. NMR studies of oocytes exposed to 15N-labeled show no significant formation of glutamine but substantial accumulation in what is likely an acid intracellular compartment. In conclusion, parallel measurements of pHi and pHS demonstrate that NH3 flows across the plasma membrane and provide new insights into how a protein molecule in the plasma membrane—AmtB—enhances
the flux of a gas across a biological membrane.
相似文献
Walter F. Boron (Corresponding author)Email: |
15.
Although mineral N generally has a negative effect on legume-rhizobia symbioses, experiments in hydroponic culture in our laboratory (Waterer et al., 1992) have shown that low concentrations of NH+
4 can stimulate nodulation in pea (Pisum sativum L.). The objectives of the current study were to determine the immediate and residual effects of NH+
4 on nodulation and N2 fixation in pea in sand culture. Peas (cv. Express) were exposed to 0.0, 0.5, 1.0, and 2.0 mM of 15N-labelled (NH4)2SO4 for 28 days after inoculation (DAI). From 28 to 56 DAI the plants were grown on a NH+
4-free nutrient solution. Plants were harvested at 7, 14, 21, 28 and 56 DAI and nitrogenase activity was measured by gas exchange at 28 and 56 DAI. Root, shoot, and nodule dry weight (DW) and total N content were obtained, in addition to nodule counts and 15N enrichment of plant composites. The 1.0 and 2.0 mM NH+
4 treatments consistently resulted in higher total plant DW accumulation than the control (0.0 mM NH+
4). At 28 DAI, plants exposed to 1.0 and 2.0 mM NH+
4 had 1.8 to 2.8 times more nodules plant-1, respectively, and plants exposed to 2.0 mM NH+
4 had 1.7 fold higher specific nodulation (nodule number g-1 root DW). However, individual nodule DW was greater in control plants, such that there were no differences in nodule DW per plant among treatments. Ammonium treatment resulted in more nitrogen derived from the atmosphere (NDFA) in peas early in the experiment, but by 28 DAI there were no treatment effects on NDFA. Whole plant and nodule specific nitrogenase activity (µmol H2 g-1 nodule DW h-1) was higher in control plants at 28 DAI. However, by 56 DAI, after an additional 4 weeks of NH+
4-free nutrition, no differences in nitrogenase activity nor whole plant or specific nodulation were detectable. This study indicates that nodulation in pea is stimulated in sand culture while exposed to NH+
4. However, once NH+
4 is removed, relative growth rate, nodulation and nitrogenase activity becomes similar to plants that were never exposed to NH+
4. 相似文献
16.
The polymerization of concentrated NH4CN solutions has been studied at various temperatures and ammonia concentrations. The products of the oligomerization of ammonium cyanide include adenine and guanine, as well as trace amounts of 2,6-diaminopurine. Our results indicate that the adenine yield is not strongly dependent on temperature. Guanine is produced in lower yield. The original studies by Oró and Kimball (1961) showed that the 6 N HCl hydrolysis of the NH4CN polymerization supernatant greatly increased the adenine yield. However, this hydrolysis also decomposes adenine and other purines. Therefore, we have measured the yields from an NH4CN polymerization as a function of hydrolysis time, and found that shorter hydrolytic periods give higher yields of adenine.We have also investigated the hydrolysis of the supernatant at pH 8, which is a more reasonable model of primitive oceanic conditions, and found that the adenine yield is comparable to that obtained with acid hydrolysis (approximately 0.1%). The yield of adenine does not decline at longer hydrolysis times because of the greater stability of adenine at pH 8. The insoluble black polymer formed from NH4CN has been analyzed by both acid and neutral hydrolysis. In both cases adenine yields of approximately 0.05% were obtained. This suggests that the polymer may have been as important a prebiotic source of purines as the usually analyzed supernatant. 相似文献
17.
J. Moreira-Silva T.K.N. Tsui J. Coimbra M.M. Vijayan Y.K. Ip J.M. Wilson 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2010,151(1):40-50
The weatherloach, Misgurnus anguillicaudatus, is a freshwater, facultative air-breathing fish that lives in streams and rice paddy fields, where it may experience drought and/or high environmental ammonia (HEA) conditions. The aim of this study was to determine what roles branchial Na+/K+-ATPase, H+-ATPase, and Rhcg have in ammonia tolerance and how the weatherloach copes with ammonia loading conditions. The loach's high ammonia tolerance was confirmed as was evident from its high 96 h LC50 value and high tissue tolerance to ammonia. The weatherloach does not appear to make use of Na+/NH4+-ATPase facilitated transport to excrete ammonia when exposed to HEA or to high environmental pH since no changes in activity were observed. Using immunofluorescence microscopy, distinct populations of vacuolar (V)-type H+-ATPase and Na+/K+-ATPase immunoreactive cells were identified in branchial epithelia, with apical and basolateral staining patterns, respectively. Rhesus C glycoprotein (Rhcg1), an ammonia transport protein, immunoreactivity was also found in a similar pattern as H+-ATPase. Rhcg1 (Slc42a3) mRNA expression also increased significantly during aerial exposure, although not significantly under ammonia loading conditions. The colocalization of H+-ATPase and Rhcg1 to the similar non-Na+/K+-ATPase immunoreactive cell type would support a role for H+-ATPase in ammonia excretion via Rhcg by NH4+ trapping. The importance of gill boundary layer acidification in net ammonia excretion was confirmed in this fish; however, it was not associated with an increase in H+-ATPase expression, since tissue activity and protein levels did not increase with high environmental pH and/or HEA. However the V-ATPase inhibitor, bafilomycin, did decrease net ammonia flux whereas other ion transport inhibitors (amiloride, SITS) had no effect. H+-ATPase inhibition also resulted in a consequent elevation in plasma ammonia levels and a decrease in the net acid flux. In gill, aerial exposure was also associated with a significant increase in membrane fluidity (or increase in permeability) which would presumably enhance NH3 permeation through the plasma membrane. Taken together, these results indicate the gill of the weatherloach is responsive to aerial conditions that would aid ammonia excretion. 相似文献
18.
生物炭具有减缓农田NH3挥发和N2O排放的重要潜力,但在施入环境后常常存在“老化”现象,这为其缓解全球变暖的长期有效性带来了不确定性。为了探明生物炭的长期效应,人工加速模拟了自然界中水分、温度、氧气、土壤矿物质及微生物多种老化因素,结合多元表征手段对比不同老化方式对生物炭性质的影响,利用主成分分析法建立新的生物炭性质综合指标来反映老化强度。再通过大田控制试验,采用原位通气法和静态箱—气相色谱法监测夏玉米生长周期内老化前后生物炭施用对农田NH3挥发和N2O排放的影响,为生物炭的可持续应用提供科学依据。结果表明,老化过程增加了原生物炭(BC)的氧含量、比表面积(SBET)、总孔容(Vt)及含氧官能团数量,降低了灰分、碱性、碳含量、平均孔径及其芳香性,各老化作用强度排序为:氧化老化生物炭(OBC)>矿化老化生物炭(KBC)>微生物老化生物炭(MBC)>干湿循环老化生物炭(WBC)>冻融循环老化生物炭(FBC)>BC。生物炭的添加减少... 相似文献
19.
Wei Yang Fuhui Xiang Hongjie Sun Yafen Chen Ewan Minter Zhou Yang 《Biochemical Systematics and Ecology》2010
The increase in concentration of ammonia in lake water during the degradation of algal blooms may last for several weeks and thus cause chronic toxicity to aquatic organisms. The purpose of this study was to assess the chronic toxicity of ammonia on the selected hematological parameters and gill Na+/K+ ATPase activity of juvenile crucian carp Carassius auratus during elevated ammonia exposure and the post-exposure recovery. Juvenile crucian carp were exposed in different ammonia solutions for 45 days and then immediately transferred to pristine freshwater to initiate a 15-day recovery period. Results showed sub-lethal ammonia significantly deters growth and a 15-day recovery period was not sufficient for the fish to compensate for the loss of growth. The fish exhibited a continuous decrease in red blood cell (RBC), the total hemoglobin (Hb), and gill Na+/K+ ATPase activity as the concentration of NH3-N increased. After the 15-day recovery period, RBC, Hb, and gill Na+/K+ ATPase activity had recovered to similar levels as the controls. 相似文献
20.
Different sensitivity of Phragmites australis and Glyceria maxima to high availability of ammonium-N
The ability to cope with NH4+-N was studied in the littoral helophytes Phragmites australis and Glyceria maxima, species commonly occupying fertile habitats rich in NH4+ and often used in artificial wetlands. In the present study, Glyceria growth rate was reduced by 16% at 179 μM NH4+-N, and the biomass production was reduced by 47% at 3700 μM NH4+-N compared to NO3−-N. Similar responses were not found in Phragmites. The amounts (mg g−1 dry wt) of starch and total non-structural carbohydrates (TNC) in rhizomes were significantly lower in NH4+ (8.9; 12.2 starch; 20.1; 41.9 TNC) compared to NO3− treated plants (28.0; 15.6 starch; 58.5; 56.3 TNC) in Phragmites and Glyceria, respectively. In addition, Glyceria showed lower amounts (mg g−1 dry wt) of soluble sugars, TNC, K+, and Mg2+ in roots under NH4+ (5.6; 14.3; 20.6; 1.9) compared to NO3− nutrition (11.6; 19.9; 37.9; 2.9, for soluble sugars, TNC, K+, and Mg2+, respectively), while root internal levels of NH4+ and Ca2+ (0.29; 4.6 mg g−1 dry wt, mean of both treatments) were only slightly affected. In Phragmites, no changes in soluble sugars, TNC, Ca2+, K+, and Mg2+ contents of roots (7.3; 14.9; 5.1; 17.3; 2.6 mg g−1 dry wt, means of both treatments) were found in response to treatments. The results, therefore, indicate a more pronounced tolerance towards high NH4+ supply in Phragmites compared to Glyceria, although the former may be susceptible to starch exhaustion in NH4+-N nutrition. In contrast, Glyceria's ability to colonize fertile habitats rich in NH4+ is probably related to the avoidance strategy due to shallow rooting or to the previously described ability to cope with high NH4+ levels when P availability is high and NO3− is also provided. 相似文献