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1.
ABSTRACT

The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH4 + to NO3 ? to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH4 + to NO3 ? on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L?1) in combination with six N treatments with different molar percentage ratios of NH4 + to NO3 ? (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L?1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L?1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO3 ?. Supplying high proportions of NO3 ? in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH4 + (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH4 + in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant?1, if plants received 10% of the total N as NH4 + and 90% as NO3 ?.  相似文献   

2.
Abstract

Pansy (Viola xwittrockiana Gams.) producers often observe nutrient disorders among plants grown during warm periods (>18°C) of the growing season. These disorders typically are not seen when production temperatures are optimal (≥18°C) even though fertility regimes may remain the same. Our objectives were to assess the effects of temperature and nitrogen (N) fertility on growth and nutrition of pansy. Pansies cultivar ‘Crown White’ were grown until lateral branches had open flowers. Treatments consisted of two temperatures (12 and 22°C) and three NO3 ?:NH4 + molar % ratios (100:0, 62:38, and 25:75) with a total concentration of 100 mg N L?1. A modified Hoagland's solution was used with NO3 ?‐N supplied as Ca(NO3)2 and KNO3 and with NH4 +‐N as (NH4)2SO4. Cumulative nutrient absorption and foliar nutrient content were determined when plant lateral branches flowered. Root and shoot growth were limited when NH4 + was present in solutions at high ambient air temperature (22°C), but not at low temperature (12°C). Individual absorption and accumulation of plant nutrients varied with N regimes and temperatures. Overall, pansies absorbed more total N, NH4 +, NO3 ?, calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), zinc (Zn), and less iron (Fe) and manganese (Mn) at 12°C than at 22°C. In addition, absorption of NO3 ? by pansy was negligible if any NH4 + was present in solutions at 22°C. Results suggest that pansy growers should adjust fertility programs according to production temperatures to avoid possible nutritional disorders and maximize plant growth. If maximum growth is to be obtained in warm temperatures, the use of NH4 +‐containing fertilizers should be reduced or eliminated. However, the choice of NO3 ?:NH4 + ratio for nutrition may be less important under cool growing conditions.  相似文献   

3.
《Journal of plant nutrition》2013,36(10):1561-1573
The interactions between NaCl and different NO3 ?NH4 + ratios were investigated. Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse, in 120L capacity containers filled with continuously aerated Hoagland nutrient solution. Treatments were added to observe the combined effect of two NaCl levels (30 and 60 mM) and three millimolar ratios of nitrate: ammonium (14:0, 12:2, 10:4) on growth, nutrition, and contents of chlorophyll and sugars. Saline treatments decreased growth, which was partly restored by NH4 + treatment. The leaf mineral composition showed a marked effect of nitrogen (N) source, while salinity only affected NO3 ? concentration. Changing the NO3 ?:NH4 + ratio from 14:0 to 12:2 and 10:4 produced progressive increases in the concentrations of iron (Fe), chlorophyll, and reducing sugars in leaves. Therefore, the deleterious effect of salinity on biomass production can be minimized by the use of nutrient solutions containing higher NH4 + concentrations, since this seemed to be correlated with increases in nitrogen assimilation and the levels of Fe and chlorophyll.  相似文献   

4.
ABSTRACT

An experiment was conducted to study the effects of nitrate (NO3 ?) and ammonium (NH4 +) ratios in nutrient solutions on the growth and production of fruits, runners, and daughter plants of strawberry Fragaria x ananassa Duch., grown in a hydroponic system. Five treatments were applied, consisting of different proportions of NH4 + and NO3 ? in the nutrient solution. The NH4 +:NO3 ? ratios were: T0 = 0:4, T1 = 1:3, T2 = 2:2, T3 = 3:1, and T4 = 4:0, at a constant nitrogen (N) concentration of 4 mol m?3. Growth and morphogenesis were characterized by monitoring leaf-area increase, number of flowers and fruits per plant, and number of daughter plants of first and second generations. Nitrogen and carbon (C) content were measured at the end of the experiment in the organs of both mother and daughter plants. None of the variables related to the growth of the mother plant was affected by the treatments. However, the number of fruits increased with the proportion of NH4 + in the nutrient solution. The number of daughter plants produced was affected only at high NH4 + proportions, and their size (dry matter per daughter plant) and fertility (number of second-generation plants per first-generation plants) were reduced. The N or C content of the plants was not significantly affected by the treatments, but the C/N ratio in the crowns of mother plants was higher in treatments with 25% and 50% NH4 + in the nutrient solution.  相似文献   

5.
Abstract

Broccoli (Brassica oleracea var. italica) plants were grown in the greenhouse and supplied continuously with 18 mM N in the following NH+ 4:NO? 3 ratios: 100:0, 75:25, 50:50, 25:75, 0:100. At commercial maturity, the plant characteristics and partitioning of nitrogen in xylem and phloem saps and in plant tissue were determined. Plants fed solely with NH+ 4 were stunted, exhibited signs of marginal necrosis on the lower leaves, and accumulated NH+ 4 in the foliage. The maximum yield and shortest harvest time, together with minimal NO? 3 and NH+ 4 accumulation were found at a ratio of 75:25. Ammonium concentrations in xylem sap decreased linearly with decreasing NH+ 4 portion in the nutrient solution, whereas the NO? 3 concentrations reached a maximum when NO? 3 constituted 50% of the N supply. The glutamate family dominated the amino acid composition of both xylem and phloem saps, but did not vary much with NH+ 4:NO? 3 ratio. It is suggested that the NH+ 4 concentration in xylem sap may be used to assess NH+ 4 vs NO? 3 utilization by broccoli grown under field conditions.  相似文献   

6.
The objective was to determine the most favorable nitrogen (N) source ratio of ammonium (NH4+) to nitrate (NO3?) for aeroponic culture of Chinese fragrant solomonseal Polygonatum odoratum (Mill.) Druce seedlings. Seedlings were cultured with solutions based on 50% Hoagland formula containing 0:100, 10:90, 20:80, and 30:70 NH4+:NO3? ratios for 21 days. Activities of anti-oxidant enzymes and glutathione contents of leaves with treatments of 10:90 and 20:80 NH4+:NO3? ratios were higher than that of all-nitrate treatment, and malondialdehyde (MDA) concentrations were lower than that of all-nitrate treatment. The maximum quantum yield ?Po value was normal among all of the treatments, whereas the absorption energy ABS/CSm value with 20:80 NH4+:NO3? treatment was highest and the heat dissipation DIo/CSm value with 20:80 NH4+:NO3? treatment was lowest among all of the treatments. These results supported that moderate proportion of 20% NH4+ in the solution provided optimal growth condition for (P) P. odoratum aeroponic culture.  相似文献   

7.
Abstract

Nitrogen‐form effect on nutrient uptake and the subsequent concentration of nutrients in turfgrass plant tissue has not been thoroughly investigated. This study evaluated the effects of clipping regime and N‐form on the tissue concentration of macronutrients and micronutrients and macronutrient uptake in ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.). Turfgrass plugs were grown under greenhouse conditions in a modified Hoagland's solution with a combination of three nutrient solutions (100% NO3 ?, 100% NH4 +, and 50:50 ratio of NH4 +:NO3 ?) and two cutting regimes (cut and uncut). Concentrations of macronutrients and micronutrients were determined for shoot, root and verdure. Nutrient uptake was determined weekly. Uncut NO3 ?‐treated plants accumulated higher concentrations of K, Ca, Mg, B and Cu in the shoot tissue; P, K, Ca, Mg, B, Cu, Mn and Zn in the root tissue; and P, Ca, Mg, B, Fe and Mn in the verdure compared to uncut NN4 +‐treated plants. Nitrate uptake was greater with uncut NO3 ?‐treated plants than was NH4 + absorption with uncut NH4 +‐treated plants. Plants grown with the uncut 50:50 treatment adsorbed more NH4 + than NO3 ?. Plants grown with the uncut NO3 ? and 50:50 treatments adsorbed higher amounts of P, K, and Ca compared to the NH4 + treatment. The cut NO3 ?‐treated plants accumulated higher concentrations of K in the shoot tissue; P, Ca, Mg, B, Cu, Fe and Mn in the root tissue; and B in the verdure than did the cut NH4 +‐treated plants. Cut NO3 ?‐treated plants adsorbed less NO3 ? than did cut NH4 +‐treated plants adsorbed NH4 +. The cut 50:50 treatment adsorbed more NH4 + than NO3 ?. Plants grown with NO3 ? and 50:50 treatments, under both cutting regimes, resulted in higher concentrations of most macro‐ and micronutrients and greater nutrient uptake compared to the NH4 +‐treated plants.  相似文献   

8.
《Journal of plant nutrition》2013,36(12):1975-1985
Production temperatures can affect the marketability of pansies (Viola × wittrockiana Gams.) by influencing plant growth, the presence of nutrient disorders, and the rate of floral development. The choice of nitrogen (N) form in fertility can also influence pansy growth and nutrition, but the effect of fertility on pansy flowering is not clear. Whether or not temperature and N fertility work together to influence nutrient absorption at different stages of the pansy life cycle is unknown. Our objectives were to determine the influence of temperature and N form on pansy floral development, and to identify the peak nutrient demand periods at different temperatures and ratios of NO3 ? to NH4 + in fertility. Pansies cv. ‘Crown White’ were grown in nutrient solution cultures until lateral branches had open flowers. Treatments consisted of two temperatures (12°C and 22°C) and three stages of floral development (five true leaf stage until visible bud, visible bud until first flower, first flower until flowering on lateral branches), and three NO3 ? :NH4 + molar % ratios (100:0, 62:38, 25:75) with a total concentration of 100 mg N L?1. A modified Hoagland's solution was used with NO3 ??N supplied as Ca(NO3)2 and KNO3 and with NH4 +?N as (NH4)2SO4. The effects of temperature and N form on the time required for development of different floral stages were assessed. In addition, the influence temperature and N form on nutrient absorption was determined for three pre‐determined stages of floral development to identify peak nutrient demand periods. The timing of flower bud development and first flower was not influenced by treatments. At 22°C, pansies flowered earlier on lateral branches than at 12°C, but these plants also suffered a loss in quality due to unfavorable growth characteristics and the development of nutritional disorders. Individual absorption of plant nutrients at different stages of development varied with temperature and N regime. Overall, pansies absorbed the greatest quantity of magnesium (Mg) before flower bud development, calcium (Ca) after flower bud development, and NH4 +, NO3 ? phosphorus (P), and potassium (K) after anthesis. In addition, pansies absorbed more NO3 ?, Ca, Mg, and P at 12°C than at 22°C. At times, the absorption of NO3 ? was dramatically decreased with increasing NH4 + in solutions. Results suggest that nutrient absorption by pansy in different stages of development is influenced by production temperatures and the choice of N form in fertilization. Adjusting fertility programs according to peak demand periods and production temperatures will help prevent periodic nutrient disorders during the life cycle, and may reduce fertilization costs.  相似文献   

9.
Fertigation with KNO3 as a means of reducing salinity hazards was tested with peanut (Arachis hypogaea) plants grown on dune sand, resulting in a reduction of plant growth and yield. The objective of this work was to study the interactions between N, K+ and NaCl as well as the effects of the NH4 +/NO3 ‐ ratio on vegetative and reproductive growth. Wheat (Triticum aestivum L.) plants were grown in polyethylene pots with fine calcareous dune sand with different proportions of NH4 + and NO3 ‐, under saline (60 mM NaCl) and non‐saline conditions. Three replicates were harvested at the beginning of flowering, and one was grown to grain maturity. NaCl reduced shoot dry weight in all the treatments. Increasing the NH4 + proportion in the total of 6 mM N in the nutrient solution, increased shoot dry weight, did not change nitrogen concentration in the dry mass but increased P percentage, either with or without 60 mM NaCl. The number of tillers produced in each treatment was correlated with dry matter yield. The effect of the NH4 +/NO3 ‐ ratio may be explained by alteration of the cation‐anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH4 + concentration, by alteration of the cation‐anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH4 + concentration.  相似文献   

10.
ABSTRACT

The addition of carbonates to a nutrient solution to alleviate ammonium (NH4 +) toxicity in hydroponically-grown cucumber (Cucumis sativus L.) plants was investigated. Stable isotopes [nitrogen (15N) and carbon (13C)] were used to assess the uptake of nitrogen [NH4 + or nitrate (NO3 ?)] as well as carbon [bicarbonate (HCO3 ?)/carbonate (CO3 2?)] by the roots. Ammonium as the sole N source at 5 mM decreased plant fresh weights compared to NO3 ?. However, at lower concentrations of NH4 + (25% of 5 mM total N), growth was increased compared to NO3 ? alone. Inorganic C enrichment [calcium carbonate (CaCO3)] of the nutrient solution increased the fresh weight of NH4 + grown plants with up to 150% relative to control plants receiving calcium hydroxide [Ca(OH)2] for pH regulation. Root 15N enrichment was lower in 15NH4 + supplied plants compared to 15NO3 ?, while the 13C enrichment in leaves was increased by NH4 + nutrition compared to NO3 ? or NH4NO3. The enhanced C capture was associated with high PEPCase activity in the roots. It is concluded that inorganic carbon enrichment of the root medium may alleviate NH4 + toxicity via increased synthesis of C skeletons and, accordingly, increased capacity for NH4 + assimilation and N export to the shoots.  相似文献   

11.
Strawberry (Fragaria ananasa) plants were grown in hydroponics in a greenhouse, where the supply of different ammonium (NH4+): nitrate (NO3?) ratios, was investigated to reduce the negative effect of alkalinity in nutrient solutions. The experiment was arranged in factorial combination with two factors, NH4+:NO3? ratios (0%:100%, 25%:75%, 50%:50%, 75%:25%, and 100%:0%) and bicarbonate (0, 25, 50, and 75 mM; NaHCO3). Plants treated with increasing bicarbonate concentrations exhibited significantly inhibited growth. In plants treated with NH4+ and NO3? simultaneously, there was a counteraction of the bicarbonate-induced growth suppression. Sole NO3? application in the presence of high bicarbonate resulted in poor growth and plant death due to high alkalinity. The adverse effect of alkalinity on SPAD values and maximal quantum yield of PSII photochemistry (Fv/Fm) alleviated with increasing proportion of NH4+ in nutrient solutions. The results showed that fruit numbers and yield of strawberry increased with elevation of NH4+ in nutrient solutions.  相似文献   

12.
Abstract

Sorghum [Sorghum bicolor (L.) Moench] seedlings were grown in nutrient solutions in a growth chamber to investigate the effects of different ratios of NO3 – and NH4 + on nutrient solution pH, dry matter yield, and N uptake. Nutrient solutions and plant tissues were assayed throughout the time plants grew in the nutrient solutions.

Nutrient solution pH depended on source of N. The pH rose to near 8 with NO3 – as the sole source of N and decreased to near or below 4 with NH4 + added to the solutions. Upon depletion of NH4 + from solution, pH values rose abruptly to near 8 and remained near this value throughout the duration of the experiments. Dry matter yield was generally higher for plants grown with some NH4 + compared to plants grown with NO3 – alone. Nitrogen uptake was generally higher in plants grown with the higher proportions of NH4 +. Nitrogen concentrations remained unchanged with plant age as NO3 –/ NH4 + ratio varied. For solutions low in NH4 +, N concentrations in roots increased with plant age. Severe Fe deficiency appeared in plants when solution pH reached and remained above 7.  相似文献   

13.
Abstract

Nitrite (NO2 ?‐N) toxicity symptoms have been observed on lettuce (Lactuca sativa) at various locations in California. The objective was to evaluate the symptoms of ammonium (NH4 +‐N) and nitrite (NO2 ?‐N) toxicity on Sundevil iceberg lettuce and Paragon romaine lettuce and to determine lettuce growth and biomass production under different levels of NO2 ?‐N. Hydroponic studies under greenhouse conditions were conducted using nutrient solutions containing nitrate (NO3 ?‐N) and two other forms of nitrogen (NO2 ?‐N and NH4 +‐N) applied at a constant concentration (50 mg NL?1) or using different NO2 ?‐N levels (0, 5, 10, 20, 30, and 40 mg N L?1) and a constant NO3 ?‐N level (30 mg N L?1). Crown discoloration (brownish color) was observed for lettuce grown in both NO2 ?‐N and NH4 +‐N solutions approximately 3 weeks after transplanting into the hydroponic systems. Lettuce grown in NO3 ?‐N solution produced larger biomass and greater number of leaves per plant than lettuce grown in NO2 ?‐N or NH4 +‐N solutions. Increasing the concentration of NO2 ?‐N suppressed plant height, fresh and dry biomass yield, and number of leaves and increased the root vascular discoloration. Lettuce growth was reduced more than 50% at NO2 ?‐N concentrations greater than 30 mg N L?1. Even at 5 mg NO2 ?‐N L?1, growth was reduced 14 and 24% for romaine and iceberg lettuce, respectively, relative to that obtained in nitrate solution. Although concentrations between 5 and 40 mg NO2 ?‐N L ?1 reduced dry biomass similarly for both lettuce types, toxicity symptoms were more severe in iceberg lettuce than in romaine.  相似文献   

14.
ABSTRACT

The present study was performed to characterize the interaction between nitrogen (N) form and availability with respect to growth, water relations, and mineral nutrition of wild swiss chard (Beta macrocarpa Guss). Plants were cultured hydroponically with two levels of N concentrations, high-N (2.5 mM) or low-N (0.5 mM), added as nitrate (NO? 3) or ammonium (NH+ 4). At high N, growth was affected significantly by N form. If the NO? 3 medium was considered as control, the use of NH+ 4 decreased dry matter production and leaf area by ca. 35%. Use of NH+ 4 led to water economy and did not affect the nutrient content of the plant tissues. Compared to growth with high N, plants growth fell in either low- NO? 3 or low- NH+ 4 medium. In this case, the difference between the two N sources was not significant. Our results showed that the replacement of NO? 3 by NH+ 4 as the N source decreased the NO? 3 concentration in consumable leaves and increased the water use efficiency.  相似文献   

15.
Evaluations of vegetative growth and leaf concentrations of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), and iron (Fe) were made of apple (Malus domestica Borkh. cvs. Granny Smith, Gala, and Golab) grown with five treatments of NO3?:NH4+ ratios in pot culture. The concentrations of NO3?:NH4+ ratios were 2.5:0.1, 6:0.3, 6:0.5, 6:0.7, and 6: 1 meq L?1. Regression analysis showed that growth parameters of main stems and branches were not affected by increases of NH4+ in the ratios. Granny Smith, Gala, and Golab differed in some of these parameters. Concentrations of N and Fe increased as NH4+ increased, whereas K and Ca decreased and Mg was not affected significantly. Generally, the treatment of 2.5:0.1 produced leaves with lower N but higher K, Ca, and Mg concentrations than the other treatments. This research showed that vegetative growth was not affected by NH4+ concentration whereas elemental composition was affected.  相似文献   

16.
Leaching of nutrients in soil can change the surface and groundwater quality. The present study aimed at investigating the effects of raw and ammonium (NH4+)-enriched zeolite on nitrogen leaching and wheat yields in sandy loam and clay loam soils. The treatments were one level of nitrogen; Z0: (100 kg (N) ha?1) as urea, two levels of raw zeolite; Z1:(0.5 g kg?1 + 100 kg ha?1) and Z2: (1 g kg?1 + 100 kg ha?1), and two levels of NH4+-enriched zeolite; Z3: (0.5 g kg?1 + 80 kg ha?1) and Z4: (1 g kg?1 + 60 kg ha?1). Wheat grains were sown in pots and, after each irrigation event, the leachates were collected and their nitrate (NO3?) and NH4+ contents were determined. The grain yield and the total N in plants were measured after four months of wheat growth. The results indicated that the amounts of NH4+ and NO3? leached from the sandy loam soil were more than those from the clay loam soil in all irrigation events. The maximum and minimum concentrations of nitrogen in the drainage water for both soils were observed at control and NH4+-zeolite treatments, respectively. Total N in the plants grown in the sandy loam was higher compared to plants grown in clay loam soil. Also, nitrogen uptake by plants in control and NH4+-zeolite was higher than that of raw-zeolite treatments. The decrease in the amount of N leaching in the presence of NH4+-zeolite caused more N availability for plants and increased the efficiency of nitrogen fertilizers and the plants yield.  相似文献   

17.
In this paper, the uptake kinetics of various nitrogens (nitrate (NO3?), ammonium (NH4+), urea, amino acid) by Chinese kale (Brassica oleracea L. var. Bailey) were studied under hydroponic condition. The results indicated that the uptake kinetics of organic and inorganic nitrogen (N) by Chinese kale conform to the Michaelis–Menten equation, and the maximum uptake rate (Vmax) and affinity index (1/Km) showed nitrate (NO3—N) > ammonium (NH4+-N) > urea-N > Gly-N, with significant differences between treatments (p < 0.05). Adding different types of N to NO3? nutrient solution had little impact on its affinity, but significantly decreased the NO3? Vmax, which showed NO3–N > NO3? + NH4+ > NO3? + urea > NO3? + Gly. Chinese kale preferred inorganic N to organic N, with NO3? preceding NH4+. Adding organic and NH4+ N to nutrient solution reduced the NO3? uptake capacity by the plant.  相似文献   

18.
《Journal of plant nutrition》2013,36(12):2413-2424
Abstract

Tomato and watermelon plants were grown in nutrient solutions in which nitrogen (N) was supplied as NO3 ? (6 mM‐N) or NH4 + (6 mM‐N). The experiments were conducted to evaluate the effect which different N sources exert on iron (Fe) uptake and accumulation, on the enzymatic activities of aconitase (Aco), chelate reductase (FeCH‐R), peroxidase (POD), catalase (CAT), and Fe‐superoxide dismutase (FeSOD), and on biomass production. For both species of plants, fertilization with NH4 + caused the total Fe concentration to be lower, in the roots and in the leaves in relation to the concentrations recorded in plants fertilized with NO3 ?. The response of the enzymes related to Fe correlated with their concentration. The plants treated with N?NO3 ? registered the highest activities in Aco, FeCH‐R, POD, and CAT for both tomato and watermelon. On the other hand, only in the tomato plants was the superoxide dismutase (SOD) activity appreciably influenced primarily by NH4 +, due possibly to the toxic effect of this N source. Finally, in relation to biomass production, fertilization with NH4 + drastically reduced growth in the tomato plants, while in watermelon plants, no significant alteration was detected in dry‐matter production, regardless of the N form used. It was concluded that the response of the parameters analyzed to NH4 + fertilization, in tomato and watermelon, compared to fertilization with NO3 ? was similar. By contrast, tomato plants, but not watermelon plants, were negatively influenced by NH4 +.  相似文献   

19.
ABSTRACT

Black walnut (Juglans nigra L.) half-sib 1+0 seedlings were exponentially fertilized with ammonium (NH4 +) as ammonium sulfate [(NH4)2SO4], nitrate (NO3 ?) as sodium nitrate (NaNO3), or a mixed nitrogen (N) source as ammonium nitrate (NH4NO3) at the rate of 0, 800, or 1600 mg N plant?1 and grown for three months. One month following the final fertilization, N concentration, growth, and photosynthetic characteristics were assessed. Compared with unfertilized seedlings, N addition increased plant component N content, chlorophyll content, and photosynthetic gas exchange. Net photosynthesis ranged from 2.45 to 4.84 μmol m?2 s?1 for lower leaves but varied from 5.95 to 9.06 μmol m?2 s?1 for upper leaves. Plants responded more favorably to NH4NO3 than sole NH4 + or NO3 ? fertilizers. These results suggest that N fertilization can be used to promote net photosynthesis as well as increase N storage in black walnut seedlings. The NH4NO3 appears to be the preferred N source to promote black walnut growth and physiology.  相似文献   

20.
ABSTRACT

This article presents the effects of nitrate/ammonium (NO3 ?/NH4 +), applied at different proportions to the root media with or without 5 mmol bicarbonate (HCO3 ?), on the yield and chemical composition of tomato fruit. Tomato plants were grown hydroponically (pH 6.9) in glasshouse conditions. The yield of fruit fresh matter from four clusters obtained from plants grown on the medium with NH4 + was about 25% lower than from the plants grown on the medium containing NO3 ? as the nitrogen (N) source. Supplying NO3 ?/NH4 + at a ratio of 4:1 increased the fruit yield by about 20% in comparison with the value recorded for NO3 ??plants. The enrichment of the medium with HCO3 ? stimulated the bearing, while the result depended on the ratio of NO3 ?/NH4 +. A combined treatment of HCO3 ? with NO3 ? or NH4 + in the medium increased yields by about 28% and 11%, respectively, in comparison to plants cultivated without HCO3 ?. The application of NO3 ?/NH4 + at ratios of 4:1 and 1:1 with HCO3 ? increased the respective yields by about 16% and 10% in comparison with plants grown without HCO3 ?. Modifications in the composition of the media affected the accumulation of organic solutions in the fruit. The NH4 + nutrition effected a 20% decrease in the accumulation of reducing sugars in the fruit in comparison to the fruit of plants grown in media with NO3 ?. In the cultivation of plants in media with various NO3 ?/NH4 + proportions the intermediate values of the reduced sugar concentrations were recorded in comparison with the values obtained for NO3 ??plants and NH4 +?plants. The enrichment of media with HCO3 ? increased the concentration of sugars in fruit from about 28% (for NO3 ??plants) to about 10% (for NH4 +?plants).

Malate and citrate are the main constituents of carboxylates in tomato fruit. The form of nitrogen applied to the medium did not significantly affect the concentration of carboxylates in fruit. Significant differences in carboxylate concentrations appeared in fruit grown on media enriched with HCO3 ? ions. In comparison with the cultivation without HCO3 ?, increases in the accumulation of carboxylates varied from about 22% to 30% depending on the form of the applied nitrogen. The concentration of amino acids in the fruit of plants grown with NH4 + exceeded that in NO3 ??plants by about 55%. In the plants grown on media of modified NO3 ?/NH4 + proportions, the concentration of amino acids in fruits were positively correlated with the level of NH4 + in the medium. The enrichment of media with HCO3 ? stimulated a further increase in amino acid concentration in fruit by about 9% in NO3 ? plants and about 21% in NH4 + plants compared with the respective control (without HCO3 ?).  相似文献   

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