Rate Of NO Research Articles

Applying heat and mass balance theory to determine the flow rate for the measurement of benthic material flux in a flow-through system

Movement of water overlying the sediments has not been taken into consideration in most of the experiments conducted to estimate the dissolved material flux from the sediment. Even in recent experiments that incorporated the stirring motion, interpretation of the data is difficult, because the mixing rate used may be different from actual mixing rate in the field. We propose a method to estimate the in situ mixing rate that should be used to set the flow rate in a flow-through core incubation system. The flow rate is calculated from the vertical mixing rate of the water that is deduced from the heat diffusivity. Release rates of NO3+NO2–N obtained from our flow-through incubation system were higher by 1–3 orders of magnitude than those from the conventional diffusion calculation method that estimates the flux from the gradient of nutrient concentration across the sediment-water interface. Increase in NO3+NO2–N flux is considered to be due to intensification of the nitrification process as a result of an increase in dissolved oxygen (DO) supply with the motion of water. DO supply is also considered to be an important factor controlling macrofaunal abundance and consequently their excretory contributions to the fluxes of dissolved organic nitrogen as well as NH4–N. From this point of view, we strongly recommend the application of heat and mass balance theory to estimate nitrogen flux using a flow-through experimental system.

Dimension effects of enclosures on ecological processes in pelagic systems

Several characteristics inherent to experimental ecosystems were examined for their influence on ecological processes in five cylindrical indoor benthic‐pelagic enclosures of different size and shape. Ecosystem development diverged significantly among the mesocosm dimensions even though environmental parameters such as surface photosynthetically available radiation (400–700 nm), turbulence intensity, water exchange rate, and nutrient input were held constant across systems. Here we show that factors that lead to the development of different plankton assemblages can be related to mesocosm geometry. The ratio of light‐receiving surface area‐to‐water column volume (As:V) was shown to control both the rate of NO3− consumption and gross primary productivity. The attenuation of water column irradiance was positively correlated with the wall area‐to‐volume ratio (Aw:V). This was manifested in greater light attenuation in systems with a high Aw:V ratio. In addition, notably greater microalgal biomass developed on the walls in systems with a high Aw:V ratio. Finally, the total surface area‐to‐volume ratio (At:V) of the mesocosms influenced the rate of energy gain and dissipation and water column temperature. The differences in temperature among dimensions possibly affected biological parameters such as bacterial biomass. Although the influence of area‐to‐volume effects on biological components in artificial systems may be substantial, our analysis indicates that some of these effects may be predictable and that future experiments can be explicitly designed to minimize artifacts of enclosure.

Nitrate Uptake and Nitrogen Use Efficiency of Two Sweetpotato Genotypes during Early Stages of Storage Root Formation

Soil N availability is an important component in storage root production of sweetpotato [Ipomoea batata (L.) Lam.]. A controlled-environment experiment was conducted to characterize effects of N availability on patterns of dry matter, nonstructural carbohydrates, and N accumulation, and to determine possible components of N use efficiency that vary between two genotypes of sweetpotato. Rooted cuttings of `Jewel' and MD810 were transplanted into pots filled with sand and kept in a growth chamber for 72 days. Plants were watered during the first 30 days with a complete nutrient solution that contained 14 mm NO3- and then for the next 42 days with one of three complete nutrient solution that contained either 2, 8, or 14 mm NO3-. At 30, 44, 58, and 72 days after transplanting, three plants from each cultivar and treatment combination were sampled and separated into leaves, stems plus petioles, fibrous roots, and storage roots. Each plant fraction was freeze-dried, weighed, ground, and analyzed for total N, soluble sugars, and starch. Availability of N in the substrate, which limited dry matter accumulation at 2 mm NO3-, was nonlimiting at 8 and 14 mm NO3-. In both genotypes, net assimilation rate, efficiency of N use (i.e., increments of dry matter accumulated per increment of N taken up), and proportion of dry matter allocated to storage roots were greater for N-stressed (2 mm NO3-) than N-replete (8 and 14 mm NO3-) plants. For the N-stressed plants, however, efficiency of N use was greater in MD810 than in `Jewel'. Although rate of NO3- uptake per unit fibrous root mass was similar in the two genotypes under the N stress treatment, MD810 had greater uptake rate than `Jewel' under nonlimiting availability of NO3- in the substrate. The increased rate of uptake under nonlimiting NO3- supplies apparently was related to enhanced rates of carbohydrate transport from shoots to roots. As tissue concentration of N declined in response to the lowest application of NO3-, shoot growth was limited prior to, and to a greater extent than, the photosynthetic rate. The resulting relative decline in sink activity of shoots thus presumably increased the availability of carbohydrates for transport to roots.

Nitrate Uptake Rate by Soybean and Wheat Plants Determined by External Nitrate Concentration and Shoot-Mediated Demand

When NO3 - is maintained at concentrations greater than those required to sustain maximum cumulative uptake by wheat (Triticum aestivum) and nonnodulated soybean (Glycine max [L.] Merrill), the net rate of uptake is not constant but oscillates between maxima and minima. The amplitudes of both the maxima and the minima increase with increases in NO3 - concentration of the solution. To determine if the amplitudes of oscillations decline when NO3 - in solution is maintained at suboptimal concentrations, net rates of NO3 - uptake were monitored daily during 22 d of vegetative growth under controlled environmental conditions for wheat from solutions containing 0.1, 0.25, 0.4, 0.5, 0.8, 1.5, 3.0, and 5.0 mM NO3 - and for soybean from solutions containing 0.05, 0.1, 0.5, and 1.0 mM NO3 -. The amplitudes of variations in daily net rates of NO3 - uptake increased with the increases in concentration of NO3 - in the nutrient solutions. The differences in magnitude of the amplitudes in oscillation, expressed as coeff...

A comparison of NH4+ and NO3– net fluxes along roots of rice and maize

Net fluxes of NH4+ and NO3– along adventitious roots of rice (Oryza sativa L.) and the primary seminal root of maize (Zea mays L.) were investigated under nonperturbing conditions using ion‐selective microelectrodes. The roots of rice contained a layer of sclerenchymatous fibres on the external side of the cortex, whereas this structure was absent in maize. Net uptake of NH4+ was faster than that of NO3– at 1 mm behind the apex of both rice and maize roots when these ions were supplied together, each at 0·1 mol m–3. In rice, NH4+ net uptake declined in the more basal regions, whereas NO3– net uptake increased to a maximum at 21 mm behind the apex and then it also declined. Similar patterns of net uptake were observed when NH4+ or NO3– was the sole nitrogen source, although the rates of NO3– net uptake were faster in the absence of NH4+. In contrast to rice, rates of NH4+ and NO3– net uptake in the more basal regions of maize roots were similar to those near the root apex. Hence, the layer of sclerenchymatous fibres may have limited ion absorption in the older regions of rice roots.

Growth and Root NO3- and PO43- Uptake Capacity of Three Desert Species in Response to Atmospheric CO2 Enrichment

In a phytotron experiment, we examined growth and rates of NO-3 and PO3-4 uptake in seedlings of two desert C3 shrubs (Larrea tridentata and Prosopis glandulosa) and a desert C4 perennial grass (Bouteloua eriopoda) grown under CO2 partial pressures of 35 or 70 Pa. Plants were grown in soil but uptake studies were conducted on roots of intact seedlings placed in nutrient solutions containing both NO-3 and PO3-4. Elevated CO2 increased total biomass by 69 and 55% in Larrea and Prosopis seedlings and by 25% in Bouteloua. NO-3 and PO3-4 uptake rates were more than doubled in Bouteloua at high compared to ambient CO2. In contrast, CO2 enrichment inhibited root NO-3 uptake capacity in Larrea by about 55% without a significant effect on PO3-4 absorption rate; rates of NO-3 and PO3-4 and uptake in Prosopis were insensitive to CO2 treatment. Elevated CO2 enhanced the proportion of biomass allocated to the fine roots in Bouteloua but markedly reduced this fraction in Larrea and Prosopis. Foliar N concentration of both shrubs decreased in response to elevated CO2, but was unaffected in Bouteloua. We suggest that compensatory changes in root size and activity are critical in determining interspecies variation in plant nutrient relations under high CO2.

The Effect of Various NO-3 / NH+4 / Urea Rates on the Yield and Quality of Tomato

The effect of various NO-3/NH+4/ urea rates on the yield and quality of tomato, grown in peat+perlite under greenhouse conditions, was investigated. According to experimental results, when nutrient solution contained high percentage of NO-3, pH of the growing medium was increased. While NH+4 or urea caused pH to decrease. N, K and Fe concentrations of the plants were not affected by N sources and rates, but P and Mn contents of the plants were affected. Phosphorus concentration of the plants was found the lowest when the nutrient solution contained only NO-3. While it increased by the partial replacement of NO-3 by NH+4 or urea in the nutrient solution. Manganese concentration were found lower, when NO-3 found in the nutrient solution higher than 80%. However, Mn concentrations of the plants were increased when the rates of NO-3/NH+4/urea was 80/20/0, 80/10/10 or 70/20/10. The highest yield was obtained from The treatments containing NO-3/NH+4 / urea in the rates of 90/10/0 and 70/20/10. The hardness of the fruit was found to be higher in the treatments containing NO-3 plus NH+4 or NH+4 + urea than NO-3 alone. The pH and nitrate concentrations of the fruits were found lower in the treatments containing NO-3 and NH+4 or NH+4 + urea than the treatments containing N as only NO-3.

Influence of light and three nitrogen sources on growth ofHeterosigma carterae(Raphidophyceae)

Abstract Growth rates of Heterosigma carterae (Hulburt) comb, nov., isolated from the 1989 bloom in Big Glory Bay, New Zealand, were studied in continuous batch cultures, with 48 combinations of light and nitrogen (N) sources: NO3 –, NH4 +, and urea. Light had more influence on cultures grown with NO3 – than cultures grown with the other N sources. At 160 μmol photons m–2 s–1, the growth rate of H. carterae was highest with NO3 –, intermediate with NH+ 4, and lowest with urea. At lower irradiances, growth rates of NO3 –‐grown H. carterae were lower than those of either form of “recycled” N. For NH4 +‐ and urea‐grown cultures, nutrient concentration contributed to a greater variation of growth than did light. H. carterae exhibited signs of toxicity at high concentrations of NH4 + and urea, particularly at low light levels. The implication of the variations in growth rate under different combinations of light and N sources is that maximum growth of H. carterae in the field is probably attained in the well‐i...

Increased soil nitrate losses under mature sugar maple trees affected by experimentally induced deep frost

This work reports and discusses data gathered during soil solution monitoring that was part of an experiment conducted in the Duchesnay Experimental Forest (Quebec, Canada) to study the effects of induced deep frost, superficial frost, and superficial frost plus drought on mature sugar maple trees (Acersaccharum Marsh.). Frost treatment was applied by preventing snow from accumulating under the canopy. Soil solution chemistry was modified when mature sugar maple trees declined after exposure to a severe deep frost. The first vegetation period after treatment showed that losses of NO3− below the rooting zone were greatly increased under affected trees. The leaching rate of NO3− and basic cations was directly related to the level of change in canopy dieback and transparency. A mean NO3− concentration of 630 μmolc•L−1 (53 times the controls; max. 4500 μmolc•L−1) was measured in soil solution under the deep frost treated trees. The leaching rate of K+ (18×, relative to the control) and Mn2+ (11×) was higher than that of Mg2+ (5×) and Ca2+ (2.6×). Acidification of the soil solution (50% more H+) as a result of intense nitrification caused an increase in aluminum concentration (5×) and a decrease in SO42−. The acidification during the year after treatment was equivalent to decades of atmospheric acid deposition. The seasonal mean of SO42− did not differ between treatments, but there was evidence of a significant correlation between pH and SO42− in soil solution. Concentration of NH4+ was also enhanced but to a lesser degree (10×) than that of NO3−. Specific conductivity was a good predictor of NO3−, Ca2+, Mg2+, and total Al in soil solution. The ion balance shifted from an anion deficit to a strong cation deficit when NO3− concentrations were high. Superficial frost with or without induced summer drought did not cause any significant change in soil solution chemistry compared with the controls. These results indicated the necessity to consider perturbations induced by extreme climate conditions, like deep soil frost, for the interpretation of soil solution chemistry data in the context of acid deposition studies and forest health.

Photoheterotrophic and chemoheterotrophic dinitrogen fixation and nitrate utilization by the cyanobacteriumAnabaena torulosa

Anabaena torulosa exhibited fructose-dependent growth, heterocyst differentiation and N2 fixation in nitrate-free (diazotrophic) cultures in photoheterotrophic and chemoheterotrophic conditions. The incorporation of nitrate into such cultures inhibited the formation of heterocysts and N2 fixation. The rate of NO 3 − uptake byA. torulosa in photoautotrophic, photoheterotrophic and chemoheterotrophic conditions was similar but it increased by 100% in phototrophic conditions. The activity of glucose-6-phosphate dehydrogenase was found to be maximum in phototrophic and photoheterotrophic conditions. Ferredoxin-NADP+ reductase, nitrate reductase and glutamate-ammonia ligase activities suggest that nitrate utilization takes place in nonphotosynthetic conditions.

Nitrate and ammonium uptake by wheat seedlings as affected by salinity and light

Abstract Nitrate (NO3‐) and ammonium (NH4+) are the two main forms of nitrogen (N) taken up by plants. Several environmental factors affect the uptake of N. This work was undertaken to study the induction of NO3‐ and NH4+ transport systems in wheat (Triticum aestivum L.) roots as affected by salinity and light. Wheat seedlings were germinated in sterilized vermiculite and plants were grown in a growth chamber under controlled conditions for eight days with a nutrient solution without N, and with or without sodium chloride (NaCl). Uptake rates of NO3% NH4+, or NH4++ NO3‐ were calculated by measuring the disappearance of N from the solutions. The NO3‐ uptake developed with time, either through induction or activation. Salinity pretreatments increased net uptake rates of NO3‐ and NH4 +, suggesting that plants were in a higher N‐deficient status when grown in saline conditions. Light decreased initial NO3”; uptake but had little effect on initial NH4+ uptake.

Diurnal changes in net uptake rate of nitrate are associated with changes in estimated export of carbohydrates to roots.

The rate of NO3- uptake by soybean (Glycine max [L.] Merrill) roots generally declines during the night in association with progressive depletion of the nonstructural carbohydrate pool in the shoot as well as the concentration of carbohydrates in roots. To determine if NO3- uptake rate changes in response to variations in translocation rate of carbohydrates from shoot to roots per se or to carbohydrate status of the roots, the night period was interrupted with a low light level from incandescent lamps to alter the diurnal pattern of NO3- uptake by roots and export of carbohydrate from shoots of nonnodulated soybean. Depletion of NO3- from replenished, complete nutrient solutions containing 1 mM NO3- was measured by ion chromatography and rates of NO3- uptake were calculated. Changes in export of carbohydrates from shoot to roots during intervals of the night period were calculated as the differences between rates of disappearance in contents of nonstructural carbohydrates and their estimated rates of utilization in shoot respiration and growth. A positive, significant correlation occurred between changes in calculated rates of carbohydrate export from shoots and NO3- uptake rates. Conversely, there was no significant correlation between concentrations of nonstructural carbohydrates in roots and NO3- uptake rates. These results support the hypothesis that carbohydrate flux from shoot to roots has a direct role in regulation of nitrogen uptake by the whole plant.

Effect of Leachate Fraction on Nitrate Loading to the Soil Profile Underlying a Greenhouse Crop

Abstract Poinsettia stock plants were grown in a greenhouse and irrigated with a 20 mM (280 ppm) N solution to produce a low (10%) or high (50%) leaching fraction (LF). At two week intervals, core samples were removed from the soil underlying the crop at 15 cm (6 in) increments to a depth of 90 cm (36 in). Leachate was collected from pots following each irrigation, and plant tissue and potting medium samples were collected. All samples (soil, leachate, plant tissue and potting medium) were analyzed for nitrate-N (NO3−N) content. The rate of NO3−N accumulation and the depth to which nitrate accumulated in the soil profile were significantly affected by leaching fraction. Under high LF treated plants, nitrate moved deeper into the soil profile and accumulated at higher concentrations than under low LF treated plants. Each irrigation event in the high LF treatment resulted in an average deposition of 243 ml (8.2 fl. ounces) of effluent containing 100 mg (3.53 × 10−3 oz) of NO3−N. The average low LF irrigation event deposited an average of 65.7 ml (2.2 fl. ounces) of effluent containing 33.5 mg (1.18 × 10−3 oz) NO3−N. Poinsettia cutting production and tissue nitrogen levels did not significantly differ between treatment groups.

Nitrate and ammonium as nitrogen sources for lupins prior to nodulation

Two cultivars of Lupinus angustifolius L. were grown in a glasshouse in solutions containing NO3-, NH4+ or NH4NO3 with a total nitrogen concentration of 2.8 M m-3 in each treatment. One cultivar chosen (75A-258) was relatively tolerant to alkaline soils whereas the other (Yandee) was intolerant to alkalinity. Controlled experiments were used to assess the impact of cationic vs. anionic forms of nitrogen on the relative performance of these cultivars. Relative growth rates (dry weight basis) were not significantly different between the two cultivars when grown in the presence of NO3-, NH4+ or NH4NO3. However, when NO3- was supplied, there was a modest decline in relative growth rates in both cultivars over time. When plants grown on the three sources of nitrogen for 9 days were subsequently supplied with 15NH4NO3 or NH415NO3 for 30 h, NH4+ uptake was generally twice as fast as NO3- uptake, even for plants grown in the presence of NO3-. Low rates of NO3- uptake accounted for the decrease in growth rates over time when plants were grown in the presence of NO3-. It is concluded that the more rapid growth of 75A-258 than Yandee in alkaline conditions was not due to preferential uptake of NH4+ and acidification of the external medium. In support of this view, acidification of the root medium was not significantly different between cultivars when NH4+ was the sole nitrogen source.

Hypolimnetic O2Consumption, Denitrification, and Methanogenesis in a Thermally Stratified Lake

Hypolimnetic O2consumption, methanogenesis, and denitrification were estimated from concentration changes in O2, CH4, and nitrogen oxides (NO3−, NO2−, N2O), respectively, in the eastern basin of Lake St. George, Ontario, during thermal stratification from 1980 to 1984. NH4+accumulated in the hypolimnion throughout the period of stratification and provided an overall measure of organic matter mineralization. Anaerobic metabolism, particularly methanogenesis, predominated because anoxia was total within less than 2 mo of spring water column turnover and nitrogen oxides were always completely depleted before fall turnover. The time of onset and rate of NO3−, depletion varied considerably between years and were not always directly correlated with O2concentration. It was estimated that, on average, O2consumption, denitrification, and methanogenesïs accounted for approximately 80% of hypolimnetic organic C mineralization in the periods surveyed.

Nutrient cycling in red spruce forests of the Great Smoky Mountains

Nutrient distributions, concentrations, and fluxes in two red spruce (Picearubens Sarg.) stands in the Great Smoky Mountains are described and used to evaluate various hypotheses for recent decline of this species. These forests, like others in the southern Appalachians, were relatively rich in N and low in base cation status. The combination of high atmospheric N and S deposition, little or no N or S retention, relatively high N mineralization, and extremely acid soils caused soil solutions to be dominated by NO3−, SO42−, Al, and H+. Soil solution Al in these sites (most of which was in monomeric form) occasionally reached levels noted to inhibit base cation uptake and root growth in solution culture studies. These pulses of Al were driven by pulses of NO3− and, to a lesser extent, SO42− in soil solution. However, fine roots were present at depths of up to 60 cm in the mineral soil, indicating that Al concentrations had not become consistently toxic to roots. Solution fluxes (both throughfall and soil leaching) exceeded litter-fall fluxes for all the macronutrients at both sites, a typical situation for K and S, but most unusual for N, P, Ca, and Mg. There are significant implications of these fluxes and of the apparent net uptake of N by foliage in terms of how vegetation uptake and translocation are calculated. Some new formulations are suggested, but measurement errors in systems with such a predominance of hydrologic fluxes make foliar leaching and, therefore, uptake and translocation calculations extremely uncertain. Although there are no outward signs of decline in these forests (other than balsam fir (Abiesbalsamea (L.) Mill.) mortality due to the balsam woolly adelgid (Adelgespiceae (Ratz.))), the high rates of NO3− leaching rates and the borderline soil solution Al values suggest that these systems are under stress. Whether these factors actually lead to a dieback or growth decline remains to be seen.

Ammonium recycling limits nitrate use in the oceanic subarctic Pacific.

Seasonal and diel changes in nutrient concentrations and nitrogen assimilation rates were used to assess the effects of NH4+ on NO3− assimilation. Surface‐water NO3− concentrations ranged from 6 to 17 µM while NH4+ concentrations ranged from 0 to 0.4 µM. Total N assimilation ranged from 84 to 732 nM d−1 but showed no seasonal trend. NH4+ and urea concentrations were <1% of total dissolved inorganic N, but use of this “regenerated” N still accounted for 44–89% of total N assimilation. Rates of NO3− assimilation were negatively correlated with ambient NH4+ concentrations, and concentrations of NH4+ between 0.1 and 0.3 µM caused complete inhibition of NO3− assimilation. NO3− was more important as a source of N in spring than in summer. We attribute this pattern to a summer increase in turnover rates for NH4+. Turnover times for the dissolved NH4+ pool were half as long in August as in May. Grazing and recycling in the euphotic zone apparently both play significant roles in preventing depletion of NO3− in the oceanic subarctic Pacific.

The relative importance of denitrification and nitrate assimilation in midcontinental bogs

Denitrification rates measured in a Minnesota bog and a bog in western Ontario were similarly low (<0.20–2.28 µg m‒2 h‒1 as N). Nitrate addition stimulated denitrification at the Minnesota bog, but <1% of added NO3‒‐N (0.01–0.1 g m‒2) was denitrified in 24 h. In the Ontario bog, denitrification was not stimulated by NO3‒‐N application (0.08 g m‒2). Rates of NO3‒‐N uptake by Sphagnum, measured by nitrate reductase activity assays and NO3‒ disappearance from cultures, were much higher, 100–24,000 µg m‒2 h‒1 (0.57–48.7 µg g‒1 h‒1), than rates of denitrification at comparable NO3‒ loadings. Measurements of NO3‒ in pore water and moss throughfall confirm that NO3‒ disappears in the top 5–10 cm of moss. Plant uptake appears to be the dominant sink for NO3‒ in midcontinental bogs.

Nitrogen Uptake by Wheat Seedlings, Interactive Effects of Four Nitrogen Sources: NO3−, NO2−, NH4+, and Urea

The net influx (uptake) rates of NO3-, NH4+, NO2-, and urea into roots of wheat (Triticum aestivum cv Yecora Rojo) seedlings from complete nutrient solutions containing all four compounds were monitored simultaneously. Although urea uptake was too slow to monitor, its presence had major inhibitory effects on the uptake of each of the other compounds. Rates of NO3-, NH4+, and NO2- uptake depended in a complex fashion on the concentration of all four N compounds. Equations were developed which describe the uptake rates of each of the compounds, and of total N, as functions of concentrations of all N sources. Contour plots of the results show the interactions over the range of concentrations employed. The coefficients of these equations provide quantitative values for evaluating primary and interactive effects of each compound on N uptake.

Effects of simulated throughfall pH and sulfate concentration on a deciduous forest soil

A model deciduous forest soil (Schaffenaker loamy sand) was treated for 8 mo in the greenhouse in 25 cm reconstructed columns with simulated throughfall at pH 6.0 or 4.0, and SO4 2− levels of 12.8 or 24.8 mg L−1. Red oak seedlings grown in the microcosms showed no growth or foliar element response to the treatments. Sulfate loading had a greater impact on soil and leachate chemistry than pH. Higher available soil P in the A, horizon was associated with the pH 6.0 and high SO4 2−2 treatment combination. High SO4 2− loading also reduced exchangeable K+ in the A1−. Other soil horizons were unaffected by either treatment. Leachate chemistry was not significantly altered by througfall pH, but significantly greater export of Na+, Ca2+, Mg2+, Al3+, and NO3 −, and lower SO4 2− loss, occurred with low SO4 − input. Comparatively half as much NO3 − loss was associated with high SO4 2− deposition. The high rate of NO3 − leaching appeared responsible for greater equivalent mass loss of cations from the low SO4 2− treatment. Leachate removal of SO4 2− approximated input after 8 mo. The capacity of this soil to adsorb SO4 2− appeared relatively limited in the absence of normal element cycling. The sulfate component of simulated deciduous forest throughfall was shown to have a potentially greater impact than pH on ion leaching from forest soil. Additional consideration of the role of SO2− 4 deposition, in the context of throughfall rather than incident precipitation, is warranted in studies of acidic deposition effects on internal forest soil processes.