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1.
Plants of Datura stramonium var. tatula L. Torr. were cultivated on vermiculite and received two different mineral solutions. In one treatment only NO3
–-nitrogen was added, while in the other NO3
–-nitrogen was partly (20%) replaced by NH4
+-nitrogen. Total dose of nitrogen as well as interionic ratios were kept constant in both treatments. With the combined treatment (NO3
–-NH4
+) a significant higher hyoscyamine content was found at the time when highest biomass was reached. This was apparently the result of an increased alkaloid biosynthesis. Also scopolamine content was positively influenced, but only at a point past maximal biomass yield.No significant differences in amounts of nitrogen bound per plant were found between both treatments.The higher alkaloid content observed with the combined treatment was associated with a higher relative proportion of bound nitrogen present in the alkaloids. It seems that more nitrogen is available for secondary metabolism when NH4
+-nitrogen is present in the culture medium. 相似文献
2.
W. Marshall Darley Clay L. Montague F. Gerald Plumley William W. Sage Arthur T. Psalidas 《Journal of phycology》1981,17(2):122-128
A “planted core” system was developed to test the effect of short term (1–2 weeks) experimental manipulation of environmental parameters on edaphic microalgae under field conditions. A large number of small cores (surface area = 7 cm2) were collected, randomized and replanted in the marsh in fiddler crab exclosures with appropriate experimental treatments. Daily enrichment of the cores with NH4+ resulted in significant increases in edaphic primary productivity and levels of chlorophyll a in both summer and winter seasons in the short-Spartina marsh. Enrichment with a complete nutrient solution caused no further increases. Nutrient enrichment of creekbank sediments was much less stimulatory to the resident algal assemblage. In both sites, but especially in the creekbank, the removal of fiddler crab grazers resulted in significant increases in chlorophyll a and productivity. Experimental manipulation of light intensity showed that the average light intensity reaching the sediment surface was saturating for chlorophyll production in the short-Spartina marsh. A reciprocal transplant experiment involving unfertilized cores from the short-Spartina marsh and creekbank marsh demonstrated that NH4+ inputs occurring in the creekbank site rapidly alleviated nitrogen limitation of edaphic algae from short-Spartina marsh. Algae in creekbank cores incubated in the short-Spartina marsh were unable to sustain high productivity once the original standing stock of NH4+ declined. 相似文献
3.
Patrick C. K. Pang 《Plant and Soil》1985,84(2):167-174
Summary Four-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) saplings planted in pots with a sand and peat mix (11) were fertilized at the rate of 200 kg N/ha of (15NH2)2CO (U-15),15NH4NO3 (A-15) and NH4
15NO3(An-15). They were placed in a shadehouse and watered regularly to maintain soil moisture at field capacity over periods of one and two years. Quantity of15N in foliage generally increased from old to current growth, irrespective of the nitrogen source. Utilization of15N fertilizers by saplings after the first and second growing seasons following fertilization was greatest with nitrate labelled ammonium nitrate AN-15, and nearly equal for urea U-15 and ammonium labelled ammonium nitrate A-15. The soil immobilized more fertilizer nitrogen-15 from U-15 and A-15 than from AN-15. Data from the present study, in which leaching losses of fertilizer were minimized, demonstrated that in terms of nitrogen uptake by the saplings the nitrate fertilizer was superior to ammonium fertilizer. 相似文献
4.
Effects of soil pH and nitrogen fertility on the population dynamics of Thielaviopsis basicola 总被引:1,自引:0,他引:1
Black root rot of tobacco, caused by Thielaviopsis basicola, is generally severe at soil pH values >5.6 and suppressed under more acidic conditions (pH < 5.2). Soil acidifying fertilizers containing NH4–N are generally recommended for burley tobacco production in North Carolina, but the effects of N form and application rate on development of black root rot and on the population dynamics of T. basicola have not been determined. Greenhouse and laboratory studies were conducted to evaluate the effects of N form (NH4
+ or NO3
–) and rate on pathogen and disease parameters at several initial soil pH levels. A moderately-conducive field soil, initial pH 4.7, was adjusted to a pH of 5.5 or 6.5 by the addition of CaOH2, then amended with the desired nitrogen form and rate. Pathogen populations were determined over time. In addition, spore production in extracts of roots from plants grown in the various nitrogen and pH treatments was determined. Finally, because tobacco responds to acidic soil conditions and exposure to NH4–N by accumulating high concentrations of the polyamine putrescine, the toxicity of putrescine on vegetative growth and reproduction of T. basicola was investigated. Low soil pH and high levels of NH4–N suppressed reproduction of T. basicola in soil and in root extract, while use of NO3–N and depletion of NH4–N resulted in rapid increases in populations of T. basicola. At 20 mM, putrescine inhibited hyphal growth by 60% and aleuriospore production by 98%. Fertilizers that reduced soil pH also reduced reproduction by T. basicola, and thus have potential for management of black root rot by suppressing populations of T. basicola over multiple years of crop production. The suppression of T. basicola and black root rot observed with NH4–N amendments may partially be due to development of an inhibitory environment in the root and not solely to changes in rhizosphere pH. 相似文献
5.
The influence of various nitrogen (N) and sulphur (S) forms on the uptake of manganese (Mn) in young spring barley (Hordeum vulgare L cv Golf) plants was examined in both a hydroponic system and in a soil-based system. The soil was a typical Danish Mn-deficient soil viz. a sandy loam soil developed on old marine sediments. Plants growing in solution culture with NO3– as the only N source had a higher Mn uptake than plants receiving mixtures of NO3– and NH4+. These findings were opposite to the results obtained in the soil-based experiments, where plants fertilized with NO3– as the only N source accumulated much less Mn than plants fertilized with NH4+. Combining the results of these experiments confirmed that NH4+ acted as a powerful antagonist to Mn2+ during uptake but that this antagonistic effect was more than compensated for by the influence of NH4+ in reducing plant-unavailable Mn(IV) to plant-available Mn(II) in the soil. Furthermore the soil experiments showed that fertilizers containing sulphur in the form of reduced S (thiosulphate) had a strong mobilizing effect on Mn, and enabled the plants to accumulate large amounts of Mn in the biomass compared with oxidized S (sulphate). Thus, fertilization with thiosulphate may be very effective in alleviating Mn-deficiency in soils developed on old marine sediments where Mn availability is limiting plant growth. 相似文献
6.
Cooxidation of naphthalene and other polycyclic aromatic hydrocarbons by the nitrifying bacterium,Nitrosomonas europaea 总被引:1,自引:0,他引:1
The soil nitrifying bacterium Nitrosomonas europaea has shown the ability to transform cometabolically naphthalene as well as other 2- and 3-ringed polycyclic aromatic hydrocarbons (PAHs) to more oxidized products. All of the observed enzymatic reactions were inhibited by acetylene, a selective inhibitor of ammonia monooxygenase (AMO). A strong inhibitory effect of naphthalene on ammonia oxidation by N. europaea was observed. Naphthalene was readily oxidized by N. europaea and 2-naphthol was detected as a major product (85%) of naphthalene oxidation. The maximum naphthol production rate was 1.65 nmole/mg protein-min in the presence of 240 M naphthalene and 10 mM NH4
+. Our results demonstrate that the oxidation between ammonia and naphthalene showed a partial competitive inhibition. The relative ratio of naphthalene and ammonia oxidation, depending on naphthalene concentrations, demonstrated that the naphthalene was oxidized 2200-fold slower than ammonia at lower concentration of naphthalene (15 M) whereas naphthalene was oxidized only 100-fold slower than ammonia oxidation. NH4
+- and N2H4-dependent O2 uptake measurement demonstrated irreversible inhibitory effects of the naphthalene and subsequent oxidation products on AMO and HAO activity. 相似文献
7.
《Aquatic Botany》1986,23(4):309-320
Direct evidence of heterotrophic dinitrogen fixation associated with the emergent aquatic angiosperm, Typha latifolia L., was obtained through the exposure of actively growing plants to 15N2 gas for 7 days in a gas-tight exposure vessel. Highest enrichments of 15N were found in roots/rhizomes and leaf bases. Slight enrichments were also found in the leaves due to translocation from the roots, rhizomes and leaf bases. Total fixed 15N values were 71.8 μg for the plant and 49.1 μg for the soil.Plants growing in silica sand, which received a nutrient solution containing combined nitrogen, exhibited higher enrichments and fixed 86% more 15N after exposure to 15N2 gas than plants which received a nutrient solution lacking combined nitrogen. It is hypothesized that the concentration of combined nitrogen added was insufficient to repress nitrogen fixation and resulted in an increase in nitrogen fixation by associated microorganisms.Propane was used to trace the loss and movement of gases from the 15N2 vessel and between the upper leaf chamber and the lower root chamber. Gas was rapidly exchanged between the upper and lower chambers through the leaves and roots of T. latifolia. Further investigations showed that propane moved at a rate of 1223 μmol day−1 from the leaves to the roots and 2652 μmol day−1 from the roots to the leaves. These data demonstrated that gases diffuse rapidly through the plant body of T. latifolia. 相似文献
8.
Effect of rice plants on nitrification-denitrification loss of nitrogen under greenhouse conditions 总被引:1,自引:0,他引:1
Summary Rice is unique among cereal crops in its ability to tolerate the anaerobic environment of waterlogged soils, but little is known about the influence of these plants on nitrogen loss by nitrification-denitrification. This problem was approached by loss of urea-N in cores with and without rice plants, using the acetylene inhibition method. Considerably greater denitrification was observed for surface-applied urea as compared to subsurface application in all cases. Regardless of the application point, however, the planted system yielded greater N2O+N2 accumulation in the first two days than from the nonplanted soil. After 4–6 days from fertilization no difference was observed in denitrification loss between planted and nonplanted systems. Inorganic NH
4
+
levels were observed to decrease rapidly in planted soils. Initial enhancement of gaseous N accumulation may occur because of the oxidized rice-root rhizosphere, however the appreciable denitrification in non-planted soil suggests that other N loss mechanisms are more important than the losses occurring in the root rhizosphere. 相似文献
9.
Effects of pH on ammonium uptake by Typha latifolia L. 总被引:5,自引:0,他引:5
The effects of solution pH on NH4+ uptake kinetics and net H+ extrusion by Typha latifolia L. were studied during short-term (days) and long-term (weeks) exposure to pH in the range of pH 3.5–8.0. The NH4+ uptake kinetics were estimated from depletion curves using a modified Michaelis-Menten model. T. latifolia was able to grow in solution culture with NH4+ as the sole N source and to withstand a low medium pH for short periods (days). With prolonged exposure (weeks) to pH 3.5, however, the plants showed severe symptoms of stress and stopped growing. The solution pH affected NH4+ uptake kinetics. The affinity for NH4+, as quantified by the half saturation constant (K1/2) and Cmin (the NH4+ concentration at which uptake ceases), decreased with pH. K1/2 was increased from 7.1 to 19.2 mmol m?3 and Cmin from 2.0 to 5.7 mmol m?3 by lowering the pH in steps from 8.0 to 3.5. Vmax was, however, largely unaffected by pH (~22 μmol h?1 g?1 root dry weight). Under prolonged exposure to constant pH, growth rates were highest at PH 5.0 and 6.5. At pH 8.0 growth was slightly depressed and at pH 3.5 growth completely stopped. NH4+ uptake kinetics were similar at pH 5.0, 6.5 and 8.0 whereas at pH 3.5 NH4+ uptake almost completely stopped. The ratio between net H+ extrusion and NH4+ uptake decreased significantly at low pH. The adverse effects of low pH on NH4+ uptake kinetics are probably a consequence of a reduced H+-ATPase activity and/or an increased re-entry of H+ at low pH, and the associated decrease in the electrochemical gradient across the plasma membranes of the root cells. 相似文献
10.
We investigated whether six arctic plant species have the potential to induce nitrate reductase (NR) activity when exposed to NO3
--nitrogen under controlled environment conditions, using an in vivo assay that uses the rate of NO2
--accumulation to estimate potential NR activity. We also assessed the effect of low root temperatures on NR activity, growth and nitrogen uptake (using 15N applications) in two of the selected species. Five of the six species (Cerastium alpinum, Dryas intergrifolia, Oxyria digyna, Saxifraga cernua and Salix arctica) were capable of inducing NR activity when exposed to solutions containing 0.5 mM NO3
- at 20°C for 10 days. Although in vivo NR activity was not induced in Saxifraga oppositifolia under controlled conditions, we conclude that it was capable of growing successfully on NO3
-, due to the presence of moderate rates of NR activity observed in both NH4
+-grown and NO3
--treated plants. Exposure of O. digyna and D. integrifolia to 3°C root temperatures for two weeks, with the shoots kept at 20°C, resulted in root and leaf NR activity rates of NO3
--treated plants being reduced to rates exhibited by NH4
+-grown plants. Although these decreases in NR in both species appeared to be due to limitations in NO3
--uptake and growth rate (rather than direct low-temperature inhibition of NR synthesis per se), direct low-temperature inhibition of root NR synthesis could not be ruled out. In contrast to the temperature insensitivity of NH4
+ uptake in D. integrifolia, NO3
--uptake in D. integrifolia was inhibited by low root temperatures. We conclude that the selected arctic species have the genetic potential to utilize NO3
--nitrogen, and that low root temperatures, in conjunction with other environmental limitations, may be responsible for the lack of induction of NR in D. integrifolia and Salix arctica under field conditions. 相似文献
11.
Several boreal and alpine forests are depleted in nutrients due to acidification. Fertilization may be a remedy, but rapidly-soluble salts (N, P, K, Mg) may pose nitrate problems for the groundwater or decrease microbial activity.With the aim to investigate potential nitrogen leaching after fertilization we set up an experiment employing intact soil cores (11 cm diameter, 20–40 cm long) from a mixed forest and a Picea abies stand (soil type Rendsina) in the Northern Calcareous Alps of Austria. The cores were fertilized with a commercial NPK fertilizer or a methylene-urea-apatite-biotite (MuAB) fertilizer at a rate corresponding to 300 kg N ha-1 and incubated for 28 weeks together with unfertilized controls. Both soil water (retrieved 5 cm below the soil surface) and leachate were analyzed for nitrate and ammonium in regular intervals. After the incubation, soil microbial biomass and basal repiration were determined and a nitrogen mineralization assay was performed.For the control, in the soil water and leachate maximum NH4
+ and NO3
- concentrations of 5 and 11 mg N L-1, respectively, were found. Compared to that, MuAB fertilizer resulted in a slow increase of NH4
+ and NO3
- in the soil water (up to 11 and 35 mg N L-1 respectively) and in the leachate (4 mg NH4
+-N L-1 and 44 mg NO3
--N L-1). Highest nitrogen loads were found for the fast release NPK fertilizer, with NH4
+ and NO3
- concentrations up to 170 and 270 mg N L-1, respectively, in the soil water. NH4
+-N levels in the leachate remained below 5, while NO3-N levels were up to 190 mg L-1. Fast- release NPK caused a significant decrease of microbial biomass and basal respiration. These parameters were not affected by MuAB fertilizer.The results suggest that the MuAB fertilizer may be an ecologically appropriate alternative to fast-release mineral fertilizers for improving forest soils. 相似文献
12.
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
13.
城乡交错带土壤氮素空间分布及其影响因素 总被引:4,自引:0,他引:4
城乡交错带土壤氮素是城乡生态系统中最重要的氮源与氮汇,但是城市化下的土壤氮素分布及其影响机制还不清楚,基于3S平台研究了土壤氮素在成都西郊城乡交错带的空间分布特征及城市化对土壤氮素的影响。结果表明,研究区内土壤全氮(STN)、硝态氮(NO_3~--N)和铵态氮(NH_4~+-N)含量均值分别为(1.46±0.06)g/kg、(50.04±3.59)mg/kg和(6.72±0.53)mg/kg。区内土壤氮素含量从近郊向远郊逐渐增高,STN和NO_3~--N含量为中部高于南北部,NH_4~+-N含量则由西北部和东南部向中部递增。方差分析表明,区内不同土地利用方式下STN、NO_3~--N和NH_4~+-N含量差异显著(P0.05)。回归分析显示STN含量与建筑密度(BD)、道路密度(RD)均呈现显著线性负相关(P0.05),NO_3~--N含量与道路密度呈极显著线性负相关(P=0.001),与建筑密度关系不明显(P=0.217)。土壤NH_4~+-N与建筑密度呈显著负线性相关(P=0.001),与道路密度呈显著指数相关关系(P=0.021)。研究结果显示城市发展使得城乡交错带土壤氮素含量降低,这种影响伴随着建筑面积的增加,道路长度的增加而加强。 相似文献
14.
Gert Arnold 《Plant and Soil》1992,142(1):41-51
Three-year-old Scots pine (Pinus sylvestris) trees were grown on a sandy forest soil in pots, with the objective to determine their NH4/NO3 uptake ratio and proton efflux. N was supplied in three NH4-N/NO3-N ratios, 3:1, 1:1 and 1:3, either as 15NH4+14NO3 or as 14NH4+15NO3. Total N and 15N acquisition of different plant parts were measured. Averaged over the whole tree, the NH4/NO3 uptake ratios throughout the growing season were found to be 4.2, 2.5, and 1.5 for the three application ratios, respectively.
The excess cation-over-anion uptake value (Ca-Aa) appeared to be linearly related to the natural logarithm of the NH4/NO3 uptake ratio. Further, this uptake ratio was related to the NH4/NO3 ratio of the soil solution. From these relationship it was estimated that Scots pine exhibits an acidifying uptake pattern
as long as the contribution of nitrate to the N nutrition is lower than 70%. Under field circumstances root uptake may cause
soil acidification in the topsoil, containing the largest part of the root system, and soil alkalization in deeper soil layers. 相似文献
15.
川西北高寒草地沙化过程中土壤氮素变化特征 总被引:7,自引:0,他引:7
草地沙化是我国最严重的环境问题之一,但关于草地沙化过程中氮素变化特征的研究报道多集中于干旱半干旱地区,而半湿润地区的相关报道还比较缺乏。通过野外调查,研究了川西北半湿润地区高寒沙质草地沙化过程中土壤氮素变化特征。结果表明,草地沙化对0—100cm土层土壤氮素具有显著影响,全氮、碱解氮、铵态氮(NH_4~+-N)、硝态氮(NO_3~--N)和微生物量氮(MBN)均呈现极显著下降的变化特征,极度沙化阶段较未沙化阶段分别减少了73.95%、77.72%、76.75%、79.77%和84.12%。其中,0—20cm土层变化最显著,全氮、碱解氮、NH_4~+-N、NO_3~--N和MBN含量分别减少了86.43%、83.52%、82.11%、88.82%和91.77%。随着土层深度增加,不同程度沙化草地土壤氮素含量及其变化量逐渐减少;草地沙化过程中,不同沙化阶段土壤氮素损失数量不尽相同,其中,以轻度沙化阶段氮素损失最严重,全氮、碱解氮、NH_4~+-N、NO-3-N和MBN含量分别降低了41.18%、35.17%、46.74%、43.46%和46.88%。草地沙化过程中,土壤全氮、碱解氮、NH_4~+-N、NO_3~--N和MBN含量与土壤粉粒、粘粒含量和植被群落盖度均呈极显著正相关特征,与土壤沙粒含量呈极显著负相关特征。研究区土壤氮素损失与风蚀选择性吹蚀土壤粉粒、粘粒及地表植物覆盖状况逐渐变差密切相关,因此该区域治沙的关键是采取措施降低风蚀对地表土壤吹蚀作用,提高沙化草地地表植被覆盖。同时,还应及时对沙化前期阶段及潜在沙化的草地进行生态治理,从而避免草地沙化继续恶化。 相似文献
16.
The relative influence of the photoperiod and of periodic ammonium pulses in entraining the cell division cycle in nitrogen-limited cyclostat cultures differs dramatically in Hymenomonas carterae Braarud and Fagerl, Amphidinium carteri Hulburt and Thalassiosira weissflogii Grun. We examined how each species processes an NH4+ pulse at various times during the cell cycle and the L/D cycle. Rates of NH4+ uptake and changes in cellular concentrations of NH4+, free amino acids, and protein were examined after the addition of an NH4+ pulse. Depletion of NH4+ from the medium occurred earlier when the pulse was given at the beginning of the light period than at the beginning of the dark period in H. carterae and A. carteri. Depletion took longer in the T. weissflogii cultures and the kinetics were similar during both stages of the photocycle in this species. Similarly, the temporal phasing and maximum pool sizes varied with timing of the NH4+ pulse in H. carterae and A. carteri but complete assimilation was relatively rapid. More persistent pools of NH4+ and free amino acids accumulated in T. weissflogii, and the patterns of assimilation varied little as a function of the timing of the pulse with respect to the photocycle. Although nitrogen metabolism occurred rapidly in nitrogen-limited H. carterae and A. carteri, the entrainment of the cell division cycle by the photoperiod resulted in a large degree of uncoupling between completion of nitrogen assimilation and cell division. It is hypothesized that the strong entrainment of the cell division cycle of T. weissflogii by NH4+ pulses results from a relatively slow rate of nitrogen metabolism. 相似文献
17.
Previously the growth of Spartina alterniflora has been found to be limited by nitrogen and correlated with sediment redox potential. In this study we have investigated a possible connection between these two factors. We have found that internal O2 transport is insufficient to saturate NH4+ uptake in short S. alterniflora in hydroponic culture. Rates of NH4+ uptake and root respiration were very sensitive to O2 concentration in the rhizosphere, saturating at about 5% O2. Ammonium uptake continued at a reduced rate for at least 4 hr under anaerobic conditions. Plant to plant variations in anaerobic rates of NH4+ uptake and root respiration were significantly correlated to the diffusion rate of CH4 tracer gas from the leaves to the roots of individual plants. 相似文献
18.
Summary Nitrogen-15 labelled urea, aqueous NH3 and (NH4)2SO4 were applied to soils contained in pots. The fertilizers were injected in 5 cm3 of solution, 3.5 cm below the soil surface, to simulate a fertilizer band in the field. Ryegrass (Lolium perenne) was planted, and several cuttings and roots were harvested. Efficiency was determined as the recovery of fertilizer-N in the plant tissues and soil.Total recovery varied from 94 to 100%. There was no significant difference between the total recovery of the 3 fertilizer forms, although recovery in the soil component was lower for (NH4)2SO4 than for urea or NH3. There was a significant difference in total recovery between soils due to the soil component. Only small amounts of15N were not recovered, whereas laboratory experiments reported elsewhere had demonstrated that substantial gaseous losses of N as N2, N2O and NO +NO2 occurred in these soils during nitrification of added NH3 fertilizer. 相似文献
19.
When grown in vitro in a medium containing NH4NO3 as the sole source of nitrogen, seeds ro the orchid, Cattleya (C. labiata ‘Wonder’ X C. labiata ‘Treasure'), germinated readily and proceeded to form small plantlets. Development of the embryos was accompanied by an increase in their total nitrogen and a decline in the percent dry weight. Growth responses of the seedlings in other ammonium salts like (NH4)2SO4, (NH4)2HPO4, NH4Cl, ammonium acetate and ammonium oxalate were similar to that in NH4NO3. However, when grown in a medium containing NaNO3, development of the seedlings was drastically inhibited; KNO3, Ca(NO3)2, KNO2 and NaNO2 also were poor nitrogen sources. Attempts to grow the seedlings in NaNO3 by changing the pH or by addition of kinetin, molybdenum or ascorbic acid as supplements were completely unsuccessful. When seedlings growing in NH4NO3 for varying periods were transferred to NaNO3, it was found that those plants allowed to grow for 60 or more days in NH4NO3 could resume normal growth thereafter in NaNO3. Determination of the nitrate reductase activity in seedlings of different ages grown in NaNO3, after NH4NO3, showed that the ability of the seedlings to assimilate inorganic nitrogen was paralleled by the appearance of the enzyme. 相似文献
20.
An experiment conducted in an unheated glasshouse from October 2006 to March 2008 studied the efficiency of different macrophytes in reducing NO3-N and NH4-N concentrations and loads in synthetic wastewaters. The experimental setup consisted of plastic tanks, filled with gravel and vegetated with Carex elata All., Juncus effusus L., Phragmites australis (Cav.) Trin., Typhoides arundinacea L. Moench (syn Phalaris arundinacea L.) var. picta and Typha latifolia L. There was also a control without vegetation. From January to July, a solution of 50–60 ppm of NH4-N and NO3-N was applied monthly; then the input concentration was doubled. The total load at the end of the experimental period was 70.4 g/m2 of NO3-N and 67.3 of NH4-N. At the end of each month, water was discharged from the tanks and analysed to determine the two nitrogen forms. At the end of the experiment, 33 g/m2 of total N (almost 24% of applied N) had disappeared in the control. Among species, the highest abatement was detected in T. latifolia (72 g/m2, almost 52% of applied N) and the lowest in J. effusus (35%).A weekly chemical analysis in July showed that a large amount of NH4-N quickly disappeared in all treatments, while NO3-N only decreased in the vegetated tanks. In December, NH4-N had similar dynamics, while NO3-N increased.All water volumes entering and exiting the tanks were measured in order to evaluate evapotranspiration. T. latifolia showed the highest water consumption, reaching a cumulative value of above 1000 mm.At the end of the experiment, J. effusus presented the highest amount of nitrogen stored in the aerial parts (5.63 g/m2) and T. latifolia the lowest (1.92 g/m2). 相似文献