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1.
The amaranthaceous dwarf glasswort, Swiss chard, table beet, spinach and Mexican tea were grown in solutions containing 0, 20, 40, 80, 120, 160, 180 and 200 mol m?3 sodium chloride (NaCl). Maximum growth and increase of biomass production compared to that at 0 mol m?3 of dwarf glasswort was observed at 200 mol m?3 (245%), and Swiss chard (146%), table beet (128%) and spinach (138%) at 80 mol m?3. The growth of these species increased with increasing sodium (Na) concentration of shoot until it reached 4.18, 2.42, 1.60 and 1.58 mol kg?1, respectively. These indicate that the order of Na-loving character is dwarf glasswort >> Swiss chard > table beet = spinach. The water contents increased with increasing Na concentration until growth reached maximum in dwarf glasswort and Swiss chard. In these highly Na-loving species, Na is activity transported to shoots and utilized for producing osmotic pressure to absorb water.  相似文献   

2.
Abstract

To evaluate the chance to reduce leaf NO3 content and to increase capability to use NH4‐N even in the absence of NO3‐N in the nutrient solution, plants of two Apiaceae species, fennel (Foeniculum vulgare Miller var. azoricum Mill. Thell.) and celery (Apium graveolens L. var. dulce Mill. Pers.), and of one species of Chenopodiaceae, Swiss chard (Beta vulgaris L. var. vulgaris), were hydroponically grown in a growth chamber with three different NH4‐N: NO3‐N (NH4: NO3) ratios (100: 0,50: 50, and 0: 100), but with the same total N level (4 mM) for 14 days. Swiss chard growth was inhibited by NH4 nutrition and reached the highest values with the NH4: NO3 ratio 0: 100. For all the morphological and yield features analyzed, fennel and celery resulted to be quite unresponsive to nitrogen (N) chemical form. Water use efficiency increased in Swiss chard and decreased in fennel and celery with the increase of NO3‐N percentage in the nutrient solution. The dependency of N uptake rate on shoot increment per unit root was more conspicuous for Swiss chard than fennel and celery. All species took more NO3‐N than NH4‐N when N was administered in mixed form. In the best conditions of N nutrition, Swiss chard accumulated NO3 in leaves in high concentration (3,809 mg kg"1 fresh mass). On average, fennel and celery accumulated 564 mg NO3 kg?1 fresh mass with the ratio NH4: NO3100: 0 and showed that by using NH4 produce having very low NO3 content can be obtained. By increasing NO3‐N percentage in the nutrient solution; NO3 leaf content of fennel and celery increased remarkably (7,802 mg kg?1 fresh mass with the ratio N H4: NO3 0: 100).  相似文献   

3.
The present study was carried out to analyze the factors that affected the growth of sugar beet in four different soil types by using concrete-framed plots as follows: soil acidity (soil pH, exchange acidity y 1) and nitrification of fertilizer introduced by row application. Comparison of the value of the exchange acidity y 1 of the four soil types with the pH value adjusted to the same level (pH 5.1) revealed that the Humic Gray Upland soil displayed the highest y 1 value (y 1: 18.0), followed by the Humic Volcanogenous Regosol (y 1: 6.9), Haplic Brown Lowland soil (y 1: 5.3), and Low-humic Andosol (y 1: 2.2). Al release to the soil solution was considered to occur at soil pH values of 4.8 and lower except in the Low-humic Andosol. Al concentration in the soil solution of the Low-humic Andosol was substantially lower than that of the other soils. On the other hand, the soil pH value decreased temporarily by nitrification of the fertilizer introduced by row application, especially in the Humic Gray Upland soil. In this case, the soil pH value became lower than 4.8 for a time. At this pH level, Al release to the soil solution was assumed to occur. As described above, the soils displayed different properties in terms of soil acidity. In the four soils, although the growth of sugar beet was significantly related to both soil pH and exchange acidity y 1 values before sowing, these relations were not strictly valid. On the other hand, the linear correlation coefficients of the relationships between the growth of sugar beet (leaf length) and NO3-N content in rows were higher than those of the soil pH and exchange acidity y 1. No appreciable variation associated with the differences in the soil types was observed in this relation. Furthermore, the values of both soil pH and exchange acidity y 1 were closely related to the NO3-N content in rows and the relationship between the NO3-N content and y 1 value appeared to be somewhat closer than that with the soil pH. These closer relations had two important implications. Firstly, NO3-N content reflected the nitrogen nutrient conditions. NO3-N promoted the growth of sugar beet directly. Secondly, the NO3-N content was affected by the soil acidity, which is expressed by the value of the exchange acidity y 1. Low NO3-N content indicated indirectly the toxicity of soil acidity to sugar beet growth. It was thus suggested that in the present study, nitrification of the fertilizer expressed by the NO3-N content was a beneficial factor for the growth of sugar beet regardless of the soil types. Finally, to promote the nitrification of fertilizer and to minimize the Al toxicity enhanced by the decrease of the soil pH associated with nitrification, it is important to avoid low values for the soil pH.  相似文献   

4.
ABSTRACT

A study was carried out to determine the influence of nitrogen (N) sources on the growth, nitrate (NO3 ?) accumulation, and macronutrient concentrations of pakchoi (Brassica chinensis L.) in hydroponics. Plants were supplied with NO3 ? and two amino acids (AA), glutamic acid (Glu), and glutamine (Gln), at six NO3 ?-N/AA-N molar ratios: (1) 100:0, (2) 80:20, (3) 60:40, (4) 40:60, (5) 20:80, (6) 0:100. The total N concentration was 12.5 mmol/L for all treatments in nutrient solutions. Both AAs reduced plant growth with decreasing NO3 ?-N/AA-N ratios, but the reduction was for Gln than for Glu. At 80:20 NO3 ?-N: Gln-N ratio, the Gln had no significant effect on pakchoi fresh weights. Decreasing NO3 ?-N/AA-N ratios reduced NO3 ? concentrations in the plant, regardless of AA sources. Adding an appropriate portion of AA-N to nutrient solutions for hydroponic culture increased concentrations of N, phosphorus (P), and potassium (K) in pakchoi shoots. Substituting 20% or less of NO3 ?-N with Gln-N in hydroponic culture will increase the pakchoi quality by reducing NO3 ? concentration and increasing mineral nutrient concentrations in shoots without significant reduction of crop yields.  相似文献   

5.
Spinach (Spinacia oleracea cv. Okame) was grown in hydroponic pot culture with an Enshi nutrient solution amended with 0, 20, or 50% urea with or without nickel addition (Ni; 0.05 mg L-1), while the total concentration of N (17.33 mmol L-1) remained constant in all the cases to evaluate the effect of partial urea application, with or without the addition of Ni, on the absorption of NO3-N, urea-N, NH4-N, minerals (e.g. Ca, K, Mg, P) by plants. Fresh and dry weight of the shoots was highest when a 20% urea solution with Ni addition was used. The variation in spinach yield was related to the absorption of total-N by the plants. The absorption of total-N, attributed mainly to NO3-N and urea-N, differed between the treatments. In the case of short-term absorption, determination by using 15N-urea and 15N-KNO3 showed that, the urea-N absorption significantly increased with the increase in the urea concentration in the nutrient solution. When the urea solutions were used, regardless of Ni addition, the absorption of NO3-N was more than four times higher than that of urea-No The addition of Ni in the urea solutions stimulated and increased both urea-N and NO3-N absorption. In the case of long-term absorption, the NO3-N absorption decreased with the decrease of the NO3-N concentration when NO3-N was partially replaced with urea in the nutrient solution. The addition of Ni in the urea solutions resulted in the increase of the absorption of both urea-N and NO3-N, but the NO3-N absorption remained lower in all the treatments compared to the control. In the urea solutions, the absorption of urea-N with or without the addition of Ni increased at a lower rate over time (sampling stages). Application of urea, with or without the addition of Ni in the nutrient solution, increased Ca absorption but decreased K and Mg absorption, whereas, P absorption was unaffected. It is suggested that spinach could grow adequately in an Enshi nutrient solution modified with 20% urea with the addition of 0.05 mg Ni L-1, when urea totally replaced NH4-N and partially replaced NO3-N.  相似文献   

6.
Forty-two-day-old wheat (Triticum aestivum L. var. Asakazekomugi) plants were treated with complete, K-free (—K), Ca-limited (—Ca), and Mg-free (—Mg) nutrient solutions for 10 days using 2 mM NH4NO3 as the nitrogen source, which was replaced with 4 mM 15 NH4C1 or Na15NO3 for the subsequent 2 days to investigate the absorption, translocation, and assimilation of inorganic nitrogen in relation to the mineral supply. In another experiment plants were grown on NO3 ?, NH4 +, NH4N03, and K-free and Ca-limited NH4N03 nutrient solutions for 10 days, and then in the latter three treatments the nitrogen source was replaced with NO3 ? and half of the —K plants received K for 6 days to examine the changes in the nitrate reductase activity (NRA).

Wheat plants absorbed NH4 ?N and NO3-N at a similar rate. Influence of K on the absorption of N03-N was stronger than that on the absorption of NH4-N in wheat plants. The supply of K to the —K plants increased the absorption of NO3-N, while the absorption of NH4-N still remained at a lower rate in spite of the addition of K. A limited supply of Ca and lack of Mg in nutrient media slightly affected the absorption of NH4-N. The influence of K was stronger on the translocation of nitrogen from roots to shoots, while Ca and Mg had little effect. When K was supplied again to the —K plants the translocation of NO3,-N was more accelerated than that of NH4-N. Incorporation of NH4-N into protein was higher than that of NO3-N in all the tissues; root, stem, and leaf. Assimilation of NH4-N and NO3-N decreased by the —K and —Mg treatments.

Leaf NRA of wheat plants decreased in the —K and —Ca plants. Higher leaf NRA was found when K was given again to the —K plants than when the plants were continuously grown in K-free media. Replacement of NO3 ? with NH4 + as the nitrogen source caused a decline of leaf NRA, while the supply of both NH4 ?N and NO3-N slightly affected the leaf NRA.  相似文献   

7.
Abstract

Pot experiments were conducted to determine effects of applied N on NO3‐N and total N concentrations in Swiss chard (Beta vulgaris var. cicla) and of applied N, P, and K on Bloomsdale spinach (Spinacia oleracea L.) and on curly mustard (Brassica pervirdis L.). Ammonium nitrate produced greater increases in NO3‐N and total N concentrations in chard than did sulfur‐coated urea at the same rates of applied N. Both N and K increased yields and NO3‐N accumulation in spinach and mustard; response to applied P resulted only in decreased NO3‐N. Both total and NO3‐N concentrations decreased with dilution and/or assimilation associated with time of growth and higher yields.

An examination of published results with several spinach cultivars indicates that differences in NO3‐N accumulation attributed to leaf type can also be explained by the higher yields of the low NO3‐N accumulators. The same is true for differences in NO3‐N accumulations attributed to light and temperature effects.  相似文献   

8.
Optimal fertilizer nitrogen (N) rates result in economic yield levels and reduced pollution. A soil test for determining optimal fertilizer N rates for wheat has not been developed for Quebec, Canada, or many other parts of the world. Therefore, the objectives were to determine: 1) the relationship among soil nitrate (NO? 3)- N, soil ammonium (NH + 4)- N and N fertilizer on wheat yields; and 2) the soil sampling times and depths most highly correlated with yield response to soil NO? 3-N and NH + 4-N. In a three year research work, wet and dried soil samples of 0- to 30- and 30- to 60-cm depths from 20 wheat fields that received four rates of N fertilizer at seeding and postseeding (plants 15 cm tall) were analyzed for NH + 4-N and NO? 3 -N using a quick-test (N-Trak) and a standard laboratory method. Wheat yield response to N fertilizer was limited, but strong to soil NO? 3-N.  相似文献   

9.
Zeolite minerals improve the efficiency of nutrient use by plants by helping to regulate the release of nitrogen and nitrate accumulation in tissues. The main objectives of this research were to evaluate effects of the addition of zeolite enriched with potassium nitrate (KNO3) on the nitrate (NO3-N) and potassium (K) levels of lettuce shoot. Treatments arranged in a completely randomized block design with three replications comprised two types of the natural zeolite: concentrated zeolite, zeolite + KNO3, and a control grown in substrate fertilized with a nutrient solution without zeolite supply. Four levels of enriched zeolite were tested (20, 40, 80, and 160 g per pot). Nitrogen, K, and NO3-N data were evaluated and response equations were fitted. The results indicated that zeolite enriched with KNO3 released the macronutrients N and K to lettuce plants. The concentrations of total N, total K, and NO3-N increased with zeolite levels, and there was a positive correlation between total N and NO3-N forms. To keep levels of NO3-N? in shoots within the safe limit for human consumption, based upon the regression equation for NO3-N the recommended dose of KNO3-enriched zeolite should be up to 78 g per plant.  相似文献   

10.
A 56-day aerobic incubation experiment was performed with 15-nitrogen (N) tracer techniques after application of wheat straw to investigate nitrate-N (NO3-N) immobilization in a typical intensively managed calcareous Fluvaquent soil. The dynamics of concentration and isotopic abundance of soil N pools and nitrous oxide (N2O) emission were determined. As the amount of straw increased, the concentration and isotopic abundance of total soil organic N and newly formed labeled particulate organic matter (POM-N) increased while NO3-N decreased. When 15NO3-N was applied combined with a large amount of straw at 5000 mg carbon (C) kg?1 only 1.1 ± 0.4 mg kg?1 NO3-N remained on day 56. The soil microbial biomass N (SMBN) concentration and newly formed labeled SMBN increased significantly (P < 0.05) with increasing amount of straw. Total N2O-N emissions were at levels of only micrograms kg?1 soil. The results indicate that application of straw can promote the immobilization of excessive nitrate with little emission of N2O.  相似文献   

11.
Abstract

In view of the unreasonable application of chemical fertilizers in agriculture and the groundwater pollution caused by nitrogen (N) leaching, a nitrogen dynamic hydroponic culture was used to simulate the dynamics variation of ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) in the leaching loss soil. Solutions with different ratio of NO3-N and NH4-N (100:0, 70:30, 50:50, 30:70 and 0:100) were prepared as well as the same solutions that not containing NO3-N .Water spinach was chosen to culture in the two solutions that differ from NO3-N every two (E2) or five days (E5) to observe the growth, quality and nutrient solution uptake. In terms of the growth, uptake of N source, N use efficiency and the chemical indicators, plants grown in the balanced solution all showed the best results. The nitrogen dynamic hydroponic culture showed some differences between E2 and E5 in some aspects. Under the same N source level, plants in E2 showed a better growth and higher NO3-N uptake than E5. On the other hand, the uptake of NH4-N seemed to be affected significantly by the interchanged frequency, which showed the same variations of glutamine synthetase activity. The activity of nitrate reductase and glutamine synthetase showed the coexist of NO3-N and NH4-N could play synergistic effect. It is not recommended to supplement NO3-N frequently in the case of N leaching loss, which has little impact on the growth and may lead to the hard taste and groundwater pollution.  相似文献   

12.
Monitoring was conducted in a basin with a history of agricultural pollution (mainly due to the spreading of livestock slurry) to evaluate the response of stream water ion concentrations to the change from agricultural land use to forest. We measured pH, electrical conductivity (EC), and major dissolved elements [phosphate (PO4) phosphorus (P), nitrite (NO2) nitrogen (N), nitrate (NO3) N, ammonium (NH4) N, silicon (Si), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), sulfate (SO4), and chloride (Cl)] in the stream water during the period 1997–2002 at irregular time intervals. Median values were significantly greater in the agricultural period than in the forest period (P < 0.05). Median pH values remained slightly acidic (5.8–6) for both land uses. NO3-N was the dominant form of dissolved inorganic nitrogen (DIN) under both land uses (agricultural use: 80 percent; forest use: 98 percent. In the forest period, the median PO4-P and NH4-N concentrations were reduced by 95 percent compared to the agricultural period. The median NO2-N and K concentrations decreased by 83 percent and 70 percent, respectively, whereas NO3-N, Cl, Na, and Si showed minor differences (decreases of 15–20 percent). These findings are consistent with the poor agricultural management practices that have been developed in the basin, especially as regards the application of slurry.  相似文献   

13.
Abstract

Sodium (Na) movement between plants and humans is one of the more critical aspects of bioregenerative systems of life support, which NASA is studying for the establishment of long‐term bases on the Lunar or Martian surface. This study was conducted to determine the extent to which Na can replace potassium (K) in red beet (Beta vulgaris L. ssp vulgaris) without adversely affecting metabolic functions such as water relations, photosynthetic rates, and thus growth. Two cultivars, Ruby Queen and Klein Bol, were grown for 42 days at 1200 μmol mol?1 CO2 in a growth chamber using a re‐circulating nutrient film technique with 0%, 75%, 95%, and 98% Na substitution for K in a modified half‐strength Hoagland solution. Total biomass of Ruby Queen was greatest at 95% Na substitution and equal at 0% and 98% Na substitution. For Klein Bol, there was a 75% reduction in total biomass at 98% Na substitution. Nearly 95% of the total plant K was replaced with Na at 98% Na substitution in both cultivars. Potassium concentrations in leaves decreased from 120 g kg?1 dwt in 0% Na substitution to 3.5 g kg?1 dwt at 98% Na substitution. Leaf chlorophyll concentration, photosynthetic rate, and osmotic potential were not affected in either cultivar by Na substitution for K. Leaf glycinebetaine levels were doubled at 75% Na substitution in Klein Bol, but decreased at higher levels of Na substitution. For Ruby Queen, glycinebetaine levels in leaf increased with the first increase of Na levels and were maintained at the higher Na levels. These results indicate that in some cultivars of red beet, 95% of the normal tissue K can be replaced by Na without a reduction in growth.  相似文献   

14.
The experiment was conducted to evaluate the effects of various nitrate/ chloride (NO3/Cl) ratios on growth, nitrate accumulation, and mineral absorption in carrot, Daucus carota L., plants in a controlled environment. The experiment included two Cl sources [potassium chloride (KC1) and calcium chloride (CaCl2)] and five NO/Clratios at 100/0, 90/10, 80/20, 70/30, and 60/40 with total‐nitrogen (N) concentration of 400 mg NO3 kg‐1 soil in 100/0 treatment. Fresh and dry weights of shoots and storage roots, and length and diameter of storage roots increased significantly with mixed NO3/C1 treatments with both Cl sources as compared to single NO3 (100/0) treatment. Growth was enhanced up to the 80/20 NO3/C1 treatments. With Cl present in the treatments, the concentration of total‐N unchanged and NO3 decreased in plants, and Cl and potassium (K) increased with the Cl sources. In KC1 treatments, Na absorption decreased. Calcium (Ca) content of the plants significantly differed by the treatments. It was concluded that N fertilization provided with combined Cl forms and NO3/Cl rates can enhance production of better quality carrot and at the same time decrease of the N fertilizer input.  相似文献   

15.
Abstract

We studied the effect of crop residues with various C:N ratios on N2O emissions from soil. We set up five experimental plots with four types of crop residues, onion leaf (OL), soybean stem and leaf (SSL), rice straw (RS) and wheat straw (WS), and no residue (NR) on Gray Lowland soil in Mikasa, Hokkaido, Japan. The C:N ratios of these crop residues were 11.6, 14.5, 62.3, and 110, respectively. Based on the results of a questionnaire survey of farmer practices, we determined appropriate application rates: 108, 168, 110, 141 and 0 g C m?2 and 9.3, 11.6, 1.76, 1.28 and 0 g N m?2, respectively. We measured N2O, CO2 and NO fluxes using a closed chamber method. At the same time, we measured soil temperature at a depth of 5 cm, water-filled pore space (WFPS), and the concentrations of soil NH+ 4-N, NO? 3-N and water-soluble organic carbon (WSOC). Significant peaks of N2O and CO2 emissions came from OL and SSL just after application, but there were no emissions from RS, WS or NR. There was a significant relationship between N2O and CO2 emissions in each treatment except WS, and correlations between CO2 flux and temperature in RS, soil NH+ 4-N and N2O flux in SSL and NR, soil NH+ 4-N and CO2 flux in SSL, and WSOC and CO2 flux in WS. The ratio of N2O-N/NO-N increased to approximately 100 in OL and SSL as N2O emissions increased. Cumulative N2O and CO2 emissions increased as the C:N ratio decreased, but not significantly. The ratio of N2O emission to applied N ranged from ?0.43% to 0.86%, and was significantly correlated with C:N ratio (y = ?0.59 ln [x] + 2.30, r 2 = 0.99, P < 0.01). The ratio of CO2 emissions to applied C ranged from ?5.8% to 45% and was also correlated with C:N ratio, but not significantly (r 2 = 0.78, P = 0.11).  相似文献   

16.
The effects of sodium chloride (NaCl) salinity (0 and 200 mM) and ammonium (NH4):nitrate (NO3) ratios (100:0, 25:75, 50:50, and 75:25) on growth, photosynthesis, fatty acids and the activity of antioxidative enzymes were investigated in canola plants. Leaf area and fresh and dry weights of leaves were significantly reduced by the salinity. The reduction in vegetative characteristics varied in both salinized and unsalinized plants according to the NH4:NO3 ratios so that the lowest reduction was observed with the 50:50 (NH4:NO3) ratio. Increased NH4 up to 50 percent (50:50) of total N, promotes the yield at both salinized and unsalinized plants. In both salinized and unsalinized plants, the increased NH4 and NO3 ratio in the nutrient solution reduced the photosynthetic (Pn) rate and stomatal conductance; however, the reduction in Pn rate was severely impaired at a higher ratio of NH4 in the nutrient solution. In both salinized and unsalinized plants, the 75:25 ratio had the lowest potassium (K) and sodium (Na) content; however, the K/Na ratio was the highest in 50:50 ratio. An increase of NH4 in the solution led to a significant increase in NH4 content in both salinized and unsalinized plants. Salinity increased NH4 content so that the salinized plant had nearly twice as high NH4 content in the leaves. The activity of nitrate reductase was increased by increasing NH4 from 0 to 50% and then reduced at a higher ratio of NH4 in the solution. The activities of antioxidative enzymes increased in salinized plants regardless of the NH4:NO3 ratios. In salinized plants, the activities of superoxide dismutase and catalase enzymes were increased by 44.4 % and 97.5%, respectively. Within salinized and unsalinized treatments, the highest activities of all antioxidant were observed in 75:25 ratio, while they remained unchanged for all NH4:NO3 ratios. The increased NH4 content in the solution increased the oil content and the maximum oil content in both salinized and unsalinized plant was obtained in both 50:50 and 75:25 ratios. The percentage of oleic acid was affected by both salinity and NH4:NO3 ratios. The ratios of NH4:NO3 had no effect on the protein content; however, salinity reduced the protein content by 20%.  相似文献   

17.
Ion-selective electrodes (ISEs) are simple tools used for rapid measurement of nitrate nitrogen (NO3-N) and potassium (K) concentrations in plant sap. With the development of best management practices (BMPs), interest exists in using ISEs for soil leachate and soil and fertilizer solutions. Nitrate N and K concentrations in the 0 to 10,000 mg L–1 ISE working range were measured in diluted solutions of common salts to assess ionic interference of calcium (Ca2+), ammonium (NH4 +), chloride (Cl–), and sulfate (SO4 2–). The effects of meter (replication) were unexpectedly significant in one out of three ranges for NO3-N and K (P values of 0.50, 0.72, and 0.01 for NO3-N and 0.99, 0.01, and 0.74 for K, for the 0–100, 100–1,000 and 1,000–10,000 mg L–1 ranges, respectively). The responses of calculated NO3-N and K concentrations to measured NO3-N and K concentrations were linear, but slopes ranged from 0.85 to 1.54, from 0.24 to 2.72, and from 0.93 to 5.48 for NO3-N and from 0.80 to 1.01, from 0.71 to 1.39, and from 0.93 to 2.21 for K for the 0–100, 100–1,000, and 1,000–10,000 mg L–1 measuring ranges, respectively. All slopes were significantly different from zero, and several were significantly different from each other and the 1:1 line. Pairwise slope comparisons conducted with covariance analysis showed that SO4 2– alone interfered with NO3-N measurements at concentrations ranging from 34 to 171 mg L–1, which was less than the manufacturer's information, and by its presence in combination with K+, NH4 +, Ca2+, and Cl– within the medium and high concentration ranges. Potassium measurements were not subject to interference from the ions tested for all three concentration ranges. These results highlight the importance of using quality assurance / quality control (QA/QC) samples in the set of unknown samples to detect inacceptable departure from linearity in routine analysis. The increase in measurement variability from one range to the next showed the importance of keeping measurements within a single concentration range by using dilutions. Hence, ISEs may be used for field measurements of NO3-N and K concentrations in soil leachate as well as soil and nutrient solutions and are therefore a practical BMP tool. However, ISEs should not be used as substitutes for the laboratory methods when official measurements are needed.  相似文献   

18.
The influx and partitioning of sodium (Na) is controlled by potassium (K)/Na selectivity/exchange mechanisms. Since ammonium‐nitrogen (NH4‐N) has been shown to inhibit K absorption and K/Na selectivity/exchange mechanisms control Na influx and partitioning, our objective was to observe if NH4‐N affects Na influx and partitioning in muskmelon. Muskmelon (Cucumis melo L.) were grown in a pH controlled nutrient solution with 100 mM NaCl in a complete nutrient solution containing either 10 mM nitrate‐nitrogen (NO3‐N) or NH4‐N. With NH4‐N, Na accumulation and partitioning to the leaf blade increased while K absorption was almost completely inhibited. A second study omitted K to simulate the inhibition of K absorption by NH4‐N and monitored Na accumulation and partitioning as K was depleted in the plant. Sodium accumulation and partitioning to the leaf increased as K decreased in the plant, mirroring the effect of NH4‐N. Roots appeared healthy in both studies. Our work indicates that at a given level of NaCl stress, NO3‐N reduces the level of stress experienced by muskmelon plants through reducing the net rate of Na influx and transport to the sensitive leaf blade, not by reducing chloride (Cl) absorption, thereby permitting these plants to “avoid”; this stress.  相似文献   

19.
The effects of soil residual nitrate (NO3-N) and ammonium (NH4-4) on wheat (Triticum aestivum L.) grain yield and N uptake were evaluated in a three-year experiment from 1991 to 1993, in the province of Quebec, Canada. Soil samples were collected at harvest from the depth of 0-30 and 30–60 cm from 20 wheat sites and analyzed in the laboratory for NO3-N and NH4-N. Wheat yield and N-uptake was also determined. Using statistical analysis system (SAS) and Matlab, data were analyzed and the best-fitted regression equations were plotted. Significant amounts of soil NO3-N was found in the soil ranging from 31.6 to 61.6 kg/ha. The amount of soil NH4-N varied from 9.2 to 23.3 kg/ha. The statistical effects of model parameters indicated that soil NO3-N and soil NH4-N significantly influenced wheat yield and N uptake. It may be possible to investigate wheat behavior at harvest using soil residual NO3-N and NH4-N.  相似文献   

20.
不同铵硝配比对弱光下白菜氮素吸收及相关酶的影响   总被引：2，自引：0，他引：2  
以黑色遮阳网覆盖模仿弱光环境, 使光照强度为自然光的20%左右, 以自然光照为对照, 采用精确控制水培溶液氮素营养, 研究NH4+-N/NO3--N 比例分别为0/100、25/75、50/50、75/25、100/0 对弱光下白菜氮代谢及硝酸还原酶和谷氨酰胺合成酶活性的影响。结果表明, 弱光下, 白菜的鲜重及叶片总氮量以NH4+-N/NO3--N 比为25/75 时最大, NH4+-N/NO3--N 比为100/0 时最低。随弱光处理的进行, 白菜叶片中硝酸还原酶活性及谷氨酰胺合成酶活性均呈下降趋势, 但NH4+-N/NO3--N 比为25/75 时, 可维持叶片内较高的硝酸还原酶活性及谷氨酰胺合成酶活性。试验表明, NH4+-N/NO3--N 比25/75 是白菜在弱光下生长的较适宜氮素形态配比。  相似文献   

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