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1.
Abstract

Experiments were conducted using different NO3 –/NH4 + ratios to determine the effects of these sources of N on mineral element uptake by sorghum [Sorghum bicolor (L.) Moench] plants grown in nutrient solution. The NO3 –/NH4 + ratios in nutrient solution were 200/0, 195/5, 190/10, and 160/40 mg N L–1. Nutrient solutions were sampled daily and plants harvested every other day during the 12‐day treatment period.

Moderately severe Fe deficiencies were observed on leaves of plants grown with 200/0 NO3 –/NH4 + solutions, but not on the leaves of plants grown with the other NO3 –/NH4 + ratios. As plants aged, less Fe, Mn, and Cu were translocated from the roots to leaves and leaf/root ratios of these elements decreased dramatically in plants grown with 200/0 NO3 –/NH4 + solutions. Extensive amounts of Fe, Mn, and Cu accumulated in or on the roots of plants grown with 200/0 NO3 –/NH4 + solutions. Manganese and Cu may have interacted strongly with Fe to inhibit Fe translocation to leaves and to induce Fe deficiency. As the proportion of NH4 + in solution increased, K, Ca, Mg, Mn, and Zn concentrations decreased in the leaves, and Ca, Mg, Mn, and Cu concentrations decreased in roots. Potassium and Zn tended to increase in roots as NH4 + in solution increased.  相似文献   

2.
The objective of the experiment was to identify the most favorable nitrogen (N) source ratio of ammonium (NH4 +) and nitrate (NO3 ?) for aeroponically-grown Douglas-fir when pH was maintained at pH 4.0. Seedlings were grown in controlled environments with solutions containing 0:100, 20:80, 40:60, 60:40, 80:20 or 100:0 NH4 +:NO3 ? ratios. Nutrient additions in the aeroponic culture units were controlled by solution conductivity set points. Seedling growth and nutrient allocation was observed for 45 days. Different NH4 +:NO3 ? ratios resulted in significant differences in the rate of N addition, growth, morphology, and nutrient allocation. Seedlings grown in solutions containing 60 or 80% NO3 ? were characterized by a combination of high growth and photosynthetic rates, high and stable internal plant N concentrations, and sufficient levels of other essential nutrients. High proportions of NH4 + in solution resulted in low rates of N addition, stunted lateral root growth, and may have been toxic.  相似文献   

3.
Nitrogen (N) by form of nutrition, ammonium (NH4+) or nitrate (NO3?), affects metabolic and physiological processes of plants. In general, a high proportion of N in NH4+ form results in poor growth. Nonetheless, a number of species exhibit optimum growth when high levels of NH4+ are provided. In the present study, lisianthus [Eustoma grandiflorum (Raf.) Shinn] was grown in rockwool cultures and irrigated with nutrient solutions containing 15 mM N with varying proportions of NH4+ and NO3?. The results showed that an increase in NH4+-N form increased plant height, number of flowers and leaves, leaf area, and shoot, stem, and leaf dry weight. The proportion of NH4+ also affected leaf concentration of phosphorus, potassium (K), calcium (Ca), and magnesium (Mg), although leaf N concentration was unaffected. Potassium leaf concentration was higher when a low proportion of NH4+ was supplemented in the nutrient solution; however, plants exhibited a decrease in leaf K concentration and a decrease in leaf Ca as the proportion of NH4+-N increased. Shoot dry weight was higher with low leaf K whereas high leaf Ca was associated with high shoot dry weight. Net photosynthesis rate was higher in plants irrigated with solutions containing 75% of total N in NH4+ form than in those irrigated with solutions of 0 or 25%. The results suggest that lisianthus can tolerate high levels of NH4+, probably associated with a higher assimilation of Ca.  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.
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   

6.
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   

7.
Abstract

This trial was carried out to establish an appropriate nutrient solution for Aglaonema commutatum and to investigate the nutritional effects generated by modifications in the solution. Six treatments were tested: control (T0; pH 6.5, E.C. 1.5 dS m?1, 6 mmol L?1 NO3 ?‐N, and 6 mmol L?1 K+); high nitrogen (N) level (T1; 9 mmol L?1 6:3 NO3 ?–NH4 +); N form (T2; 6 mmol L?1 N‐NH4 +); high K+ level (T3; 12 mmol L?1 K+); high electrical conductivity (T4; E.C. 4 dS m?1, 25 mmol L?1 NaCl), and basic pH (T5; pH 8). At the end of the cultivation, leaf, shoot, and root dry weights and elemental concentrations were determined. Nutrient contents and total plant uptake were calculated from the dry weights and nutrient concentrations. Plant K+ uptake increased with application of K+ or basic nutrient solution. The uptake and transport of calcium (Ca) were enhanced by the use of NO3 ?‐N and inhibited by the presence of other cations in the medium (NH4 +, K+, Na+) and by basic pH. Magnesium (Mg) uptake increased with NO3 ?‐N application and with pH. Sodium (Na) uptake was the highest in the saline treatment (T4), followed by the basic pH treatment. Sodium accumulation was detected in the roots (natrophobic plant), where the plant generated a physiological barrier to avoid damage. Dry weight did not differ significantly (p<0.05) among treatments except in the NaCl treatment. These results may help in the formulation of nutrient solutions that take into account the ionic composition of irrigation water and the physiological requirements of plants.  相似文献   

8.
Abstract

The form of nutrient solution nitrogen (either NH4‐N or NO3‐N or mixtures of the two) provided to plants influences the severity of many crop diseases. This greenhouse study was conducted to determine how growth, grain yield, and yield components of oat (Avena sativa L.) and wheat (Triticum aestivum L.) plants given nutrient solutions containing different ratios of NO3‐N to NH4‐N would react to barley yellow dwarf virus (BYDV) infection. Fifteen‐day‐old seedlings (2nd leaf stage) were either infected with BYDV (PAV strain) or left uninfected. Nutrient solution treatments (started 19 d after germination) provided three ratios of NO3‐N to NH4‐N (100% NO3, 50:50 NH4:NO3, or 100% NH4) for a 30‐d period, after which plant height and tillers plant?1 were measured. Oat and wheat plants given NH4 had fewer tillers than plants given the other nutrient solution treatments. BYDV‐infected oat and wheat plants were shorter than uninfected plants. All pots then received NO3 nutrient solution until plant maturity, after which days to anthesis, primary tiller height, grain yield and yield components were measured. In the NH4 nutrient solution treatments, BYDV infection significantly reduced individual kernel weight in oat and primary tiller height in wheat. These same measures were not significantly affected by BYDV infection in the NO3 or NH4NO3 nutrient solution treatments. There were no other significant nutrient solution by BYDV infection interactions for any other dependent variable measured. Nutrient solution treatments had no significant effect on grain yield, but BYDV infection reduced grain yield by 45% in oat and 46% in wheat. In conclusion, nutrient solution N form interacted with BYDV infection to alter disease tolerance in oat (kernel weight) and wheat (primary tiller height), but these alterations had no effect in ameliorating grain yield loss caused by BYDV disease.  相似文献   

9.
Cucumber plants were grown hydroponically in three different nutrient solutions to determine the effect of NO3 ‐/NH4 + ratio on several parameters. Top and root growth, CO2 fixation, and ion content (K+, Ca+2, NO3 ‐) were always lower when urea and ammonium nitrate were the major N source as compared with a Hoagland solution in which nitrate was the major N source. No significant differences were found in total N and protein content among the three nutrient solution treatments.  相似文献   

10.
Chickpea plants (Cicer arietinum L cv. ILC 195) were grown for 24 days in water culture under two regimes of nitrogen nutrition (NO3 or NH4‐N) with or without Fe. For plants fed with NO3‐N, Fe stress severely depressed fresh weight accumulation and chlorotic symptoms of Fe‐deficiency developed rapidly. Little difference in growth occurred in the NH4‐fed plants, whether or not Fe was withheld, with no visual evidence of Fe‐deficiency indicating a beneficial effect of NH4 in depressing the symptoms of Fe chlorosis. Typical pH changes were measured in the nutrient solution of the control plants in relation to nitrogen supply, increasing with NO3 and decreasing with NH4‐nutrition. With both forms of nitrogen, plants acidified the nutrient solution in response to Fe‐stress. Under NH4‐nutrition, acidification was enhanced by withholding Fe. In the NO3‐fed plants the uptake of all nutrients was reduced by the stress but proportionally NO3‐ and K+ were most affected. Total anion uptake was depressed more than that of cation uptake. For the NH4‐fed plants withholding Fe resulted in an increased uptake of all ions except NH4 + which was depressed. Regardless of the form of N‐supply, when Fe was withheld from the nutrient solution the net H+ efflux calculated from the (C‐A) uptake values was closely balanced by the OH” added to the nutrient solution to compensate for the pH changes. Evidence of accumulation of organic acids in the Fe‐stressed plants was found, especially in the NO3‐fed plants, indicating a role for these internally produced anion charges in balancing cation charge in relation to the depression of NO3 ‐ uptake associated with Fe‐stress.  相似文献   

11.
Nitrogen is taken up by most plant species in the form of nitrate and ammonium. The objective of this study was to investigate the effect of different nitrogen forms on the growth of watermelon seedlings. Plants were grown in hydroponic culture with five nitrate (NO3?)/ammonium (NH4+) ratios (100/0, 75/25, 50/50, 25/75, 0/100). When the proportion of NH4+ was increased, the leaf number, leaf area, shoot height, net photosynthesis, biomass, and root growth were significantly decreased. Higher concentrations of nitrogen (N) and phosphorus (P) were observed when plants were supplied with mixed NO3? and NH4+ compared to NO3? or NH4+ alone, whereas the concentrations of potassium (K), calcium (Ca), and magnesium (Mg) were decreased with increasing NH4+. The microelements concentrations were generally increased with more NH4+ added. In addition, plants fed with higher NO3?/NH4+ ratios resulted in more minerals accumulation.  相似文献   

12.
The objective of this research was to study the effects of nitrogen (N) forms (NO3–, 2.6 mM; NH4+, 2.6 mM; NO3–, 1 mM + NH4+, 1.6 mM) on the growth and mineral composition of kiwifruit plants exposed to three boron (B) levels (0.025, 0.1, 0.3 mM). The kiwifruit plants were grown in a 1:1 sand : perlite mixture and irrigated daily with nutrient solutions. Shoot height, mean shoot dry weight, the number of leaves, mean leaf dry weight, and N concentration of NH4‐treated plants were significantly higher compared to the NO3– treatment at all B levels. The concentration of 0.3 mM B significantly reduced shoot height for all N treatments. Boron toxicity symptoms appeared 14 days after starting the experiment, when plants were treated with 0.1 and/or 0.3 mM B. The nitrate supply reduced the B concentration of roots, but B levels of different leaf parts were hardly affected by the N form. Furthermore, the NH4‐N form significantly reduced the Mg concentration of the leaves.  相似文献   

13.
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   

14.
Tomato (Lycopersicon esculentum L. Mill. ‘Vendor') plants were grown for 21 days in flowing solution culture with N supplied as either 1.0 mM NO3 ‐ or 1.0 mM NH4 +. Acidity in the solutions was automatically maintained at pH 6.0. Accumulation and distribution of dry matter and total N and net photosynthetic rate were not affected by source of N. Thus, when rhizosphere acidity was controlled at pH 6.0 during uptake, either NO3 ‐ or NH4 + can be used efficiently by tomato. Uptake of K+ and Ca2+ were not altered by N source, but uptake of Mg2+ was reduced in NH4 +‐fed plants. This indicates that uptake of Mg2+ was regulated at least partially by ionic balance within the plant.  相似文献   

15.
Abstract

Tobacco (Nicotiana tabacum L., cv. ‘Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO3 ‐ or 1.0 mM NH4 + as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO3 ‐ or NH4 + uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO‐ was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH4 + was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO3 ‐ ‐fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH4 + ‐fed plants was increased to pH 4.0, however, specific rate of NH4 + uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH4 + ‐fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH4 + ‐fed plants to increased root‐zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress.  相似文献   

16.
Five winter cultivars of Triticum aestivum L., representing a known range of tolerance to aluminum (Al), were grown in nutrient solutions with and without Al for 41 days to determine long‐term changes in solution pH. Plant‐induced pH of the nutrient solutions declined for 16 to 17 days. Subsequently, the pH induced by Al‐sensitive plants grown without Al and Al‐tolerant plants grown with Al and without Al increased rapidly, presumably reflecting depletion of NH4 + from the nutrient solutions. Aluminum‐sensitive plants grown with Al showed a less pronounced pH rise after 16 to 17 days of treatment.

After nutrient solutions were renewed on days 26 and 34, plant‐induced pH patterns were similar to those during days 1 to 26. However, the time required for the onset of the rapid rise in pH decreased. In these subsequent pH cycles, the pH patterns induced by Al‐tolerant plants grown with Al progressively approximated those induced by plants grown without Al. Aluminum‐sensitive plants grown with Al did not induce a rapid rise In pH of nutrient solutions.

Differential tolerance to Al was apparent visually after three to five days growth. Cultivar tolerance to Al was correlated with the initial rate of the pH decline (days 1 to 26) as well as final pH of solutions discarded on days 26, 34, and 41. These results support the hypothesis that differential uptake of NH4 + and NO3 ‐ causes cultivar differences in plant‐induced pH of nutrient solutions and affects the relative growth of cultivars in Al‐toxic nutrient solutions.  相似文献   


17.
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   

18.
Nitrogen nutrition and Al toxicity with young beech plants. II: Mineral contents of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO3 or NH4-form. pH-changes of the solutions were either corrected to the initial pH of 4,0 after two days, or not corrected over a period of two weeks. The cation contents of the roots and shoots were greater if the nitrogen was supplied in NO3-form. Increasing Al concentrations in the nutrient solutions led to an increase in Al contents and a decrease in Ca- and Mg-contents in roots and shoots.  相似文献   

19.
Nitrogen nutrition and Al toxicity with young beech plants. I: Development of young beech plants in relation to the source of nitrogen and the Al content of the nutrient solution Young beech plants were grown in aerated nutrient solutions with different Al concentrations over a period of 14 weeks. Nitrogen was supplied in either NO3- or NH4-form. pH-changes of the solutions were either corrected to the initial pH of 4 after two days, or not corrected over a period of two weeks. Root growth of the beech seedlings was inhibited by Al. Reduction of root length and dry matter production was more severe if the plants were fed with ammonium nitrogen compared to nitrate nitrogen. Detrimental effect of Al on root growth was also influenced by the pH of the solution. NH4-N-nutrition led to pH decrease and therefore to increased solubility and toxicity of aluminium. On the contrary, NO3-N-nutrition weakened Al toxicity because of pH increase at the root surface and in the AFS. This led to an inactivation of Al in the form of insoluble hydroxy aluminium polymers. Compared to NO3-N-nutrition NH4-N promoted shoot growth. During 14 weeks no detrimental effect of Al on shoot growth was observed.  相似文献   

20.
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   

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