Growth and ion uptake by wheat supplied nitrogen as nitrate,or ammonium,or both

Summary The effects of concentration and source (NH₄, NO₃, and NO₃ plus NH₄) of added N on the rate of growth, final yield, and content and rate of intake of N, P, K, Ca, Mg and S by wheat seedlings were evaluated. Rate of growth in dilute liquid cultures differed among the N sources giving yields relative to those of the all-NO₃ system of 92 per cent for the all-NH₄ system, and of 154 per cent for the NO₃ plus NH₄ system. At low rates of NH₄ intake in the all-NH₄ systems growth rates were equal to or slightly better than those of plants supplied equivalent concentrations of NO₃. Rates of NH₄ intake exceeding 100 mole g^–1 h^–1 resulted in reduced growth rates and incipient NH₄ toxicity. Yields at 95 per cent of maximum resulted with steady-state N concentrations of 80 M in all NO₃ systems, 30 M NH₄ in all-NH₄ systems, and in combined source systems when 200M NO₃ plus 30 M NH₄ were supplied. The rate of N intake and plant protein content, were maximal when both NO₃ and NH₄ were supplied. Increasing rates of NO₃ intake were associated with increases in the rates of Ca, Mg, and K intake; but with increasing rates of NH₄ absorption, intake of Ca and Mg decreased. The yield and growth rate enhancement observed from the addition of low concentrations of NH₄ to cultures supplying adequate NO₃ is suggested to result from the reduced energy requirement for utilization of NH₄, as compared to NO₃ in protein synthesis and from the increased photosynthetic capacity of the higher-protein NH₄-fed plants. In the all-NH₄ systems the maximum attainable growth rate was limited by NH₄ toxicity; whereas in the all-NO₃ systems the rate of NO₃ reduction was limiting.Contribution from the Department of Soils and Plant Nutrition, University of California, Davis, California 95616.     

Organic nitrogen content and nitrate and nitrite reductase activities in tritordeum and wheat grown under nitrate or ammonium

Tritordeum is a fertile amphiploid derived from durum wheat (Triticum turgidum L. conv. durum) × a wild barley (Hordeum chilense Roem. et Schultz.). The organic nitrogen content of tritordeum grain (34 mg g^-1 DW) was significantly higher than that of its wheat parent (25 mg g^-1 DW). Leaf and root nitrogen content became higher in tritordeum than in wheat after four weeks of growth, independently of the nitrogen source (either NO₃ ^- or NH₄ ⁺). Under NO₃ ^- nutrition, tritordeum generally exhibited higher levels of nitrate reductase (NR) activity than wheat. Nitrite reductase (NiR) levels were however lower in tritordeum than in its wheat parent. In NH₄ ⁺-grown plants, both NR and NiR activities progressively decreased in the two species, becoming imperceptible after 3 to 5 weeks of growth. Results indicate that, in addition to a higher rate of NO₃ ^- reduction, other physiological factors must be responsible for the greater accumulation of organic nitrogen in tritordeum grain.     

Growth, uptake, and assimilation of ammonium, nitrate, and urea, by three strains of Karenia brevis grown under low light

Observations of near-bottom populations of Karenia brevis suggest that these cells may derive nutrients from the sediment–water interface. Cells undergoing a metabolic-mediated migration may be in close proximity to enhanced concentrations of nutrients associated with the sediment during at least a fraction of their diel cycle. In this study, the growth, uptake and assimilation rates of ammonium, nitrate, and urea by K. brevis were examined on a diel basis to better understand the potential role of these nutrients in the near-bottom ecology of this species. Three strains of K. brevis, C6, C3, and CCMP 2229, were grown under 12:12 light dark cycle under 30 μmol photons m⁻² s⁻¹ delivered to the surface plain of batch cultures. Nitrogen uptake was evaluated using ¹⁵N tracer techniques and trichloroacetic acid extraction was used to evaluate the quantity of nitrogen (N) assimilated into cell protein. Growth rates ranged from a low of 0.12 divisions day⁻¹ for C6 and C3 grown on nitrate to a high of 0.18 divisions day⁻¹ for C3 grown on urea. Diurnal maximum uptake rates, ρ_max, varied from 0.41 pmol-N cell⁻¹ h⁻¹ for CCMP 2229 grown on nitrate, to 1.29 pmol-N cell⁻¹ h⁻¹ for CCMP 2229 grown on urea. Average nocturnal uptake rates were 29% of diurnal rates for nitrate, 103% of diurnal uptake rates for ammonium and 56% of diurnal uptake rates for urea. Uptake kinetic parameters varied between substrates, between strains and between day and night measurements. Highest maximum uptake rates were found for urea for strains CCMP2229 and C3 and for ammonium for strain C6. Rates of asmilation into protein also varied day and night, but overall were highest for urea. The comparison of maximal uptake rates as well as assimilation efficiencies indicate that ammonium and urea are utilized (taken up and assimilated) more than twice was fast as nitrate on a diel basis.     

Amino acids of barley plants in relation to nitrate,urea or ammonium nutrition

Summary When barley seedlings were transplanted into media containing either nitrate, ammonium, or urea their protein and free glutamate content increased during the first few hours. Following the commencement of active growth both the ammonium and urea assimilating plants showed greater increase in free aspartate and organic nitrogen content than the nitrate assimilating plants. Form of nitrogen had no effect on protein concentration and composition, and was of little importance as a source of differences in the total amino acid composition of the plant. re]19740503     

Manganese tolerance in subterranean clover (Trifolium subterraneum L.) genotypes grown with ammonium nitrate or symbiotic nitrogen

Summary A wide range of clover accessions were screened for reaction to manganese (Mn) in solution culture. Growth was supported with ammonium nitrate (NH₄NO₃) or symbiotic nitrogen to assess Mn effects on symbiosis and the suitability of NH₄NO₃ dependent growth for assessing Mn tolerance in clover. Reduction of dry matter at Mn 45 ppm varied 0–70%, at Mn 90 ppm, 38–92%, the extent depending on genotype. Tolerant clovers tended to restrict the movement of Mn from roots to shoots. Several previously untested lines were the most tolerant while some commercial lines possessed poor tolerance. Ranks of tolerance for the two nitrogen (N) sources at Mn 45 ppm were correlated suggesting no dominant, discriminatory effects of N source on Mn tolerance; but inclusion of symbiotic effectiveness in a multiple correlation improved the relation between relative tolerances of genotypes under different N sources. Mn affected some aspects of symbiosis. Total nodule nitrogenase activity mainly reflected effects of Mn on nodule number but nitrogenase activity per nodule also contributed. To establish relative tolerances of subterranean clover to Mn growth with NH₄NO₃ is suitable and useful when symbiotic effectiveness is unknown.     

Growth and uptake of caesium,rubidium, and potassium by ectomycorrhizal and saprotrophic fungi grown on either ammonium or nitrate as the N source

After the accident at the Fukushima Dai-ichi Nuclear Power Plant in 2011, high activities of radiocaesium have been reported in wild mushrooms in Japan. Fungi play an important role in the dynamics of radiocaesium in forest ecosystems. We examined the contents of caesium (Cs), rubidium (Rb), and potassium (K) in the mycelium of 15 isolates of ectomycorrhizal (EM) fungi and nine isolates of saprotrophic (SA) fungi in a synthetic medium with either ammonium chloride (NH₄Cl) or sodium nitrate (NaNO₃), supplemented with 1 ppm caesium chloride and rubidium chloride. The mycelia were harvested after 8 weeks of incubation, and the contents of Cs, Rb, and K were measured by inductively coupled plasma mass spectrometry. The dry weight of the mycelium in the medium with NH₄ was significantly higher than that with NO₃, although some EM species, Hebeloma, Astraeus, Scleroderma, and Pisolithus, grew well in the medium with NO₃. Among SA species, Crucibulum and Cyathus grew in the medium with NO₃. The uptakes of Cs, Rb, and K by Suillus, Pisolithus, and Rhizopogon were higher than that in other EM and SA species when they grew on the medium with NH₄, while the uptakes of these elements by Astraeus and Scleroderma were higher than those by other species grown on the medium with NO₃. The content of Rb was positively correlated with Cs (r = 0.85, p < 0.001) and K (r = 0.51, p < 0.001). The accumulation of Cs, Rb, and K was differently affected by the N source and fungal species.     

Effect of ammonium or nitrate on nitrogen fixation by a terrestrial Blue-green alga

Summary The effects of ammonium or nitrate-nitrogen on biological nitrogen fixation by an algal crust are compared. Nitrate-nitrogen up to 3.0 moles N g^–1 sand/algal crust at 60% water holding capacity did not affect fixation, whereas an ammonium-nitrogen concentration of 0.2 moles N g^–1 crust markedly depressed fixation. Consequences of these differential effects are considered.     

Competition of two marine diatom algae for urea and nitrate nitrogen under three levels of irradiance

Biomass dynamics of the plankton diatoms Thalassiosira weissflogii and Pseudo-nitzschia delicatissima were analyzed in batch mono- and mixed cultures grown on media with urea or nitrate as the sources of nitrogen, under irradiance 13, 38, and 115 microE/(m(2) x s). At the initial enrichment, nitrogen concentration was 0.18 mmol, and the nitrogen : phosphorus ratio was 5 : 1. The mechanisms of competition for the limiting resource satisfactorily described the interactions between the algae grown on urea. Competitive ability of algae was characterised according to the value of competitive eddect (CE), which was calculated as the ratio of growth rate and accumulated biomass decrease in mixed culture to that in monoculture CE of algae grown on urea increased with the increasing of irradiance and was lower than that of algae grown on nitrate. CE of P. delicatissima was higher than that T. weissflogii, independently of the source of nigrogen and the level of irradiance. At 38 and 115 microE/(m(2) x s) the growth of T. weissflogii ceased earlier than that of P. delicatissima, independently of the source o nitrogen. At 13 microE/(m(2) x s) the growth of P. delicatissima ceased earlier than of T. weissflogii in on cultures grown urea, but the growth of T. weissflogii was the first to cease on nitrate. The competition revealed in experimental communities for the nitrogen of urea between plankton algae gives reasons to suggest that in natural communities plankton algae also compere under inorganic nitrogen deficiency and organic nitrogen abundance.     

Nitrate regulation of nitrate uptake and nitrate reductase expression in barley grown at different nitrate:ammonium ratios at constant relative nitrogen addition rate

Barley (Hordeum vulgare L. cv. Golf) was cultured using the relative addition rate technique, where nitrogen is added in a fixed relation to the nitrogen already bound in biomass. The relative rate of total nitrogen addition was 0.09 day^?1 (growth limiting by 35%), while the nitrate addition was varied by means of different nitrate: ammonium ratios. In 3- to 4-week-old plants, these ratios of nitrate to ammonium supported nitrate fluxes ranging from 0 to 22 μmol g^?1 root dry weight h^?1, whereas the total N flux was 21.8 ± 0.25 μmol g^?1 root dry weight h^?1 for all treatments. The external nitrate concentrations varied between 0.18 and 1.5 μM. The relative growth rate, root to total biomass dry weight ratios, as well as Kjeldahl nitrogen in roots and shoots were unaffected by the nitrate:ammonium ratio. Tissue nitrate concentration in roots were comparable in all treatments. Shoot nitrate concentration increased with increasing nitrate supply, indicating increased translocation of nitrate to the shoot. The apparent V_max for net nitrate uptake increased with increased nitrate fluxes. Uptake activity was recorded also after growth at zero nitrate addition. This activity may have been induced by the small, but detectable, nitrate concentration in the medium under these conditions. In contrast, nitrate reductase (NR) activity in roots was unaffected by different nitrate fluxes, whereas NR activity in the shoot increased with increased nitrate supply. NR-mRNA was detected in roots from all cultures and showed no significant response to the nitrate flux, corroborating the data for NR activity. The data show that an extremely low amount of nitrate is required to elicit expression of NR and uptake activity. However, the uptake system and root NR respond differentially to increased nitrate flux at constant total N nutrition. It appears that root NR expression under these conditions is additionally controlled by factors related to the total N flux or the internal N status of the root and/or plant. The method used in this study may facilitate separation of nitrate-specific responses from the nutritional effect of nitrate.     

Ionic balance in different tissues of the tomato plant in relation to nitrate, urea, or ammonium nutrition

An investigation was carried out to study the cation-anion balance in different tissues of tomato plants supplied with nitrate, urea, or ammonium nitrogen in water culture.

Irrespective of the form of nutrition, a very close balance was found in the tissues investigated (leaves, petioles, stems, and roots) between total cations (Ca, Mg, K and Na), and total anions (NO₃⁻, H₂PO₄⁻, SO₄⁻⁻, Cl⁻) total non-volatile organic acids, oxalate, and uronic acids. In comparison with the tissues of the nitrate fed plants, the corresponding ammonium tissues contained lower concentrations of inorganic cations, and organic acids and a correspondingly higher proportion of inorganic anions. Tissues from the urea plants were intermediate between the other 2 treatments. These results were independent of concentration or dilution effects, caused by growth. In all tissues approximately equivalent amounts of diffusible cations (Ca⁺⁺, Mg⁺⁺, K⁺ and Na⁺), and diffusible anions (No₃⁻, SO₄⁻⁻, H₂PO₄⁻, Cl⁻) and non-volatile organic acids were found. An almost 1:1 ratio occurred between the levels of bound calcium and magnesium, and oxalate and uronic acids. This points to the fact that in the tomato plant the indiffusible anions are mainly oxalate and pectate. Approximately equivalent values were found for the alkalinity of the ash, and organic anions (total organic acids including oxalate, and uronic acids).

The influence of nitrate, urea, and ammonium nitrogen nutrition on the cation-anion balance and the organic acid content of the plant has been considered and the effects of these different nitrogen forms on both the pH of the plant and the nutrient medium and its consequences discussed.

     

Effect of ammonium and ferricyanide on nitrate utilization by Chlorella vulgaris

It has been shown previously that added ammonium salts cause a cessation of nitrate utilization in some Chlorella species. It has also been shown that Chlorella vulgaris can form an inactivated nitrate reductase which is an HCN complex. In the present study, a comparison has been made of the rate of nitrate utilization and the rate of nitrate reductase inactivation in Chlorella vulgaris in response to the addition of ammonium salts and light-dark changes. The rate of formation of HCN-inactivated enzyme is too slow to account for the prompt inhibition of nitrate utilization caused by adding ammonium. In contrast, when nitrate utilization is inhibited by addition of ferricyanide to intact cells, the HCN-inactivated enzyme is promptly formed in vivo, and might account for the inhibition of nitrate utilization, though inhibition of nitrate uptake can not be excluded.     

Effect of ammonium on nitrate utilization by roots of dwarf bean

The effect of exogenous NH₄⁺ on NO₃⁻ uptake and in vivo NO₃⁻ reductase activity (NRA) in roots of Phaseolus vulgaris L. cv Witte Krombek was studied before, during, and after the apparent induction of root NRA and NO₃⁻ uptake. Pretreatment with NH₄Cl (0.15-50 millimolar) affected neither the time pattern nor the steady state rate of NO₃⁻ uptake.

When NH₄⁺ was given at the start of NO₃⁻ nutrition, the time pattern of NO₃⁻ uptake was the same as in plants receiving no NH₄⁺. After 6 hours, however, the NO₃⁻ uptake rate (NUR) and root NRA were inhibited by NH₄⁺ to a maximum of 45% and 60%, respectively.

The response of the NUR of NO₃⁻-induced plants depended on the NH₄Cl concentration. Below 1 millimolar NH₄⁺, the NUR declined immediately and some restoration occurred in the second hour. In the third hour, the NUR became constant. In contrast, NH₄⁺ at 2 millimolar and above caused a rapid and transient stimulation of NO₃⁻ uptake, followed again by a decrease in the first, a recovery in the second, and a steady state in the third hour. Maximal inhibition of steady state NUR was 50%. With NO₃⁻-induced plants, root NRA responded less and more slowly to NH₄⁺ than did NUR.

Methionine sulfoximine and azaserine, inhibitors of glutamine synthetase and glutamate synthase, respectively, relieved the NH₄⁺ inhibition of the NUR of NO₃⁻-induced plants. We conclude that repression of the NUR by NH₄⁺ depends on NH₄⁺ assimilation. The repression by NH₄⁺ was least at the lowest and highest NH₄⁺ levels tested (0.04 and 25 millimolar).

     

Phytoplankton uptake of ammonium, nitrate and urea in the Neuse River Estuary, NC, USA

Uptake rates of ammonium, nitrate and urea were measured during the spring, summer and autumn (2001) in the eutrophic, nitrogen (N) limited Neuse River Estuary (NRE), North Carolina, USA. Ammonium was the dominant form of N taken up during the study, contributing approximately half of the total measured N uptake throughout the estuary. Nitrate uptake declined significantly with distance downstream comprising 33% of the total uptake in the upper estuary but only 11 and 16% in the middle and lower estuary, respectively. Urea uptake contributed least to the total pool in the upper estuary (16%), but increased in importance in the middle and lower estuary, comprising 45 and 37% of the total N taken up, respectively. The importance of regenerated N for fuelling phytoplankton productivity in the mesohaline sections of the NRE is demonstrated. The contribution of urea to the regenerated N pool suggests that internal regeneration of dissolved organic N may support a large proportion of the phytoplankton primary production and biomass accumulation in the middle and lower NRE. These results suggest that N-budgets based on dissolved inorganic N uptake rates alone will seriously under estimate phytoplankton N uptake.     

Growth of embryogenic sweet orange callus on media varying in the ratio of nitrate to ammonium nitrogen

Embryogenic callus from Citrus sinensis (L.) Osbeck cv. Hamlin was cultured for 28 days on 20 media arranged in a 5×2×2 factorial varying in the ratio of nitrate to ammonium nitrogen, total inorganic nitrogen, and benzyladenine. Fresh weight increase of callus and final medium pH were significantly affected by total inorganic nitrogen and the ratio of nitrate to ammonium. The nitrate to ammonium ratio accounted for 55% of the variation in the fresh weight increase of the callus and 93% of the variation in the final medium pH. Varying the NO₃ ^-:NH₄ ^- ratio provided adequate pH control.Abbreviation BA benzyladenine     

Carbohydrate and free amino acid contents in tomato plants grown in media with bicarbonate and nitrate or ammonium

Tomato plants were cultivated (from 2 to 23 days after germination) in media with NO ₃ ⁻ , NH ₄ ⁺ , or a mixture of both forms in different proportions used as the N source given with or without 5 mol dm⁻³ HCO ₃ ⁻ . The accumulation of soluble sugars (reducing sugars and sucrose) and free amino acids was higher in the roots and leaves of NH ₄ ⁺ -fed plants than in NO ₃ ⁻ -fed plants. Starch accumulation in NH ₄ ⁺ -fed plants was higher in leaves (about 28%) and lower in roots (about 37%) in comparison with that of NO ₃ ⁻ -fed plants. Plants cultivated in media containing a mixture of NO ₃ ⁻ /NH ₄ ⁺ were characterized by a lower content of sugars and amino acids accumulation in comparison with that in plants fed with NO ₃ ⁻ or NH ₄ ⁺ . An elevated HCO ₃ ⁻ concentration in the rhizosphere stimulated the accumulation of soluble sugars and free amino acids in all the experimental variants. There were only small differences in the starch content.