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1.
Tomato plants were grown in sand culture with NO3 or NH4 N at two levels of light. Foliar sprays at three levels of N as well as combinations of foliar and root feeding were used.

Shade increased NH4 toxicity in plants sprayed with NH4 but decreased the toxicity in plants receiving NH4 through the roots. NH4‐N greatly reduced growth and cation uptake when supplied through the roots but not with foliar application. Plants sprayed with NH4 showed better growth, higher K, Ca, and Mg content and lower free NH4 in shoot, compared to plants receiving NH4 through the roots.

The overall free amino acid contents of shoots was higher for NH4‐fed plants regardless of how the N was applied. Plants sprayed with NH4 incorporated a greater amount of N into insoluble compounds compared with NO3 nutrition. The N uptake per unit of leaf area was higher for plants grown under full sun light whereas N content was higher for plants grown under hade. N content in tissue increased with N concentration in foliar spray, although plants supplied with N through the roots had higher levels of free amino acids and total nitrogen.  相似文献   


2.
Pepper plants were hydroponically grown in a growth chamber with two levels of light intensity (300 and 240 w/m2 ) and two N03:NH4 ratios (100:0 and 80:20). Plants supplied with both N forms (80:20) under high light conditions showed a decrease of nutrient uptake and produced low plant weight and yield compared to the all NO3 treated plants. By contrast, plants receiving both N forms (80:20) with light reduced over 25% showed a growth and yield slightly superior to plants supplied with N03 as sole source of N. This suggests a significant light intensity‐N form interaction that favors all NO3 nutrition for pepper at high light intensities.  相似文献   

3.
Abstract

Seedlings of four maize hybrids were grown hydroponically to investigate the impact of different N sources (Ca(NO3)2, (NH4)2SO4 and a 1:1 mixture of both) on (i) production and partitioning of root and shoot dry matter, (ii) concentration of soluble carbohydrates in roots and shoots and their partitioning to these plant parts, (iii) concentration of starch in the shoot, and (iv) N uptake. During the main phase of the experiments (duration 14d), the plants were grown in a greenhouse at 25/22°C day/night temperatures and a photoperiod of 16h. Nitrogen was supplied at three concentrations (2.8, 28, and 280 ppm). The root‐zone pH was 6.5. Under the lowest N supply, the N sources produced similar root and shoot dry matters. At the highest N level (280 ppm), NO3‐fed plants were superior. In contrast, the mixture of NH4 and NO3 ? was optimum at 28 ppm. More or less pronounced N form by N concentration interactions were also found in the concentration and distribution of soluble carbohydrates and in all remaing traits. There were almost statistically significant cultivar by N form interactions in shoot dry matter (P = 0.07) and total dry matter (P = 0.06), indicating the existence of considerable genotypic variation in sensivity to NH4‐N.  相似文献   

4.
Physiological responses of plants to ammonium (NH4) versus nitrate (NO3) nutrition can vary considerably. A greenhouse study was conducted to examine the effect of ammonium‐nitrogen/nitrate‐nitrogen (NH4‐N/NO3‐N) ratio on dry matter partitioning and radiation use efficiency in corn (Zea mays L.). The hybrid Funks G 4673A was supplied with nutrient solutions that contained 8:1, 1:1, or 1:8 ratios of NH4‐N/NO3‐N. At each of four harvests, plants were separated into leaf blades, stem + leaf sheaths, and roots. Radiation use efficiency was calculated from these dry matter harvests and measured photosynthetically active radiation. Generally, more dry matter was partitioned to the stem than to leaf tissue when supplied with the 1:8 NH4‐N/NO3‐N ratio than when supplied with the other N treatments. Corn supplied with 8:1 and 1:1 ratios of NH4‐N/NO3‐N resulted in radiation use efficiency values for total dry matter that were significantly higher by 39 and 25%, respectively, than that of corn supplied with the 1:8 ratio indicating that Funks G 4673A was more efficient in converting radiation into dry matter when supplied with high proportions of NH4 than when supplied primarily with NO3.  相似文献   

5.
The influence of N form on xylem exudate and the guttation fluid concentration in cucumber plants was studied under greenhouse conditions. Plants were hydroponically grown with three NO3:NH4 ratios (100:0, 80:20, and 60:40) at a constant pH of 6.0 in the nutrient solutions. Plants supplied with 60:40 NO3:NH4 ratio displayed a significant decrease of NO3‐N, total‐N, organic‐P, and Mn concentrations in the xylem sap and an increase of H2PO4‐P, SO4‐S, Cl, B, and Zn concentrations. Potassium and Ca uptake in these plants was slightly reduced, indicating that pH control was an important factor for cationic nutrition in cucumber plants fed with NH4. The major ions present in the nutrient solutions are concentrated in the xylem sap, particularly for NO3, K, Ca, and Na. The NO3:NH4 ratio had a small effect on the ionic levels of the guttation fluid. The concentrations of all nutrients in the guttation fluid were substantially reduced, except for Cl, showing that the leaf tissues of cucumber plants remove the excess of Cl ion. Finally, in this study, secondary effects of N source on ion uptake and release were minimized by controlling nutrient solution pH.  相似文献   

6.
Under conditions of salt stress, plants show qualitative and quantitative alterations in various organic compounds, such as nitrogen (N) compounds and organic acids. In this work, the effect of different saline levels as well as various N levels, supplied as nitrate (NO3) or as ammonium (NH4)+NO3 on the concentration of amino acids and organic acids in the leaves of tomato and cucumber plants has been studied. The effect of the source of N on individual amino acid contents varied with plant species. Most of the amino acids increased when the concentration of N in the nutrient solution was increased, except when N was added as NH4+NO3 for tomato. The effect of salt stress depended on which amino acid was considered. The data also indicate that the effect of salinity on each particular amino acid was greatly dependent on the plant species and N source. Organic acids were differently affected by salinity and by the N source, depending on the plant species. In tomato, the concentrations of short‐chain organic acids were 2–3 times higher in NO3‐supplied plants than in those grown with NH4+NO3. Finally, in cucumber, malic acid concentration increased as a function of the saline level in the medium.  相似文献   

7.
Artichoke plants (Cynara scolymus L.) were grown in a growth chamber in a modified Hoagland solution for seven weeks to determine the influence of ammonium:nitrate (NH4:NO3) ratio (100:0, 70:30, 30:70 and 0:100) on growth, water use, and the uptake of nitrogen (N) and inorganic anions and cations. Typical pH changes were recorded: the nutrient solution became acidified with NH4 or NH4:NO3 nutrition; pH increased when NO3 was the only N source. Ammonium‐fed plants (100:0 ratio) were stunted, with signs of marginal leaf necrosis, progressive wilting of leaves and poor root growth. After 49 days, leaf area was 77, 998, 2,415, and 1,700 cm2 and dry weight was 1.0, 12.9, 38.0, and 26.0 g/plant, with NH4:NO3 100:0, 70:30, 30:70, and 0:100, respectively. Leaf area ratio (LAR) was lower in plants supplied solely with NO3 than in those with mixed NH4‐NO3. Increasing NO3‐N percentage in the nutrient solution increased water use efficiency (WUE): 623, 340, and 243 mL of water were necessary to produce 1 g of dry matter in 100:0, 70:30, 30:70 or 0:100 NH4:NO3 ratio, respectively. Increasing NO3 from 0 to 100% of the total N supplied in the nutrient solution, the shoot content of inorganic cations increased on an equivalent basis by 30% and organic anions (estimated by the difference between inorganic anions and inorganic cations) increased by 2.3 times. These results suggest that leaves are the most important site of NO3 assimilation in artichoke. By increasing NH4 percentage in the nutrient solution, the tissue content of inorganic anions was generally increased, except for NO3, and the same figure was observed for the percentage of reduced N. Results from this study suggest that NO3 is the N‐form preferred by artichoke.  相似文献   

8.
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   

9.
Abstract

Tomato plants were grown in sand culture with NH+ 4, and NO? 3, forms of N and three levels of light. Plants supplied with NH+ 4, nutrition under high light intensity had symptoms of stunting, leaf roll, wilting, interveinal chlorosis of the older leaves, and one third the dry weight of N03‐fed plants. In contrast, growth of plants receiving NH+ 4, nutrition under shade appeared normal although dry weight was reduced. NH4‐N nutrition suppressed K, Ca and Mg accumulation in tissues and increased P contents as compared to NO3‐N nutrition.  相似文献   

10.
Studies on the effects of salinity and nitrogen (N) fertilization on ionic balance, biomass, and organic N production of annual ryegrass (Lolium multiflorum Lam.) were conducted. Plants grown in sand were irrigated with nutrient solution with an electrical conductivity of 2 or 11.2 dS#lbm‐1, and N in the form of sodium nitrate (NaNO3), ammonium nitrate (NH4NO3), or ammonium sulfate [(NH4)2SO4] ranging from 0.5 to 9.0 mM. Salinity increased the concentration of total inorganic cations (C) in plants and specifically sodium (Na) by more than 3‐fold higher in plants grown at high salinity as compared with plants at low salinity. Sodium (Na) concentration in roots was higher than in shoots irrespective of the salinity level, suggesting a restriction of Na transport from roots to shoots. The concentration of total inorganic anions (A) increased with salinity and when plants were supplied with nitrate (NO3), salinity increased the concentrations of NO3 and chloride (Cl) in plants. Increasing salinity and N concentration in the growth medium increased organic anions concentration in plants, estimated as the difference between C and A. The effect of different N sources on C‐A followed the order: NH4NO3 > NO3 > ammonium (NH4). The base of organic anions and inorganic ions with salinity contributed significantly to the osmotic potential of plants shoots and roots. Changes in C affected N and organic acids metabolism in plants, since C were highly correlated (p=0.0001) with C‐A and organic N (Norg) concentrations regardless of the salinity level or N source in the nutrient solutions. A high and positive linear dependency was found between Norg and C‐A in plants grown at high and low salinity levels and different N sources, pointing out the close relationship between Norg and organic anions on metabolism under these conditions. The amount of biomass produced was correlated positively with organic anion concentration in plants exposed to different salinity levels. Plant biomass increased with N concentration in the nutrient solution regardless of the salinity level applied. Biomass accumulation decreased while Norg concentration increased with salinity. Organic N content remained unaffected in plants exposed to salinity when grown in N less than 9.0 mM.  相似文献   

11.
Uptake and assimilation of inorganic N in young rice plants has been studied with labelled N (N-15). Depletion of the plants' carbohydrate content, obtained by a preceding dark period, resulted in a drastic reduction of NH4 +-N uptake. Plants exposed to low light intensity showed diminishing NH4 +-N uptake rates as compared with plants exposed to full light intensity, the latter showing constant NH4 +-N uptake rates during the whole experimental period. The percentage of labelled insoluble N in total labelled N was not significantly affected by a preceding dark period, whereas the low light intensity resulted in a lower proportion of insoluble N in roots and shoots. The incorporation of labelled N into the insoluble fraction (proteins, nucleic acids) was higher in plants fed with NH4 +-N than in those fed with NO3 -.

The uptake of NH4 +-N was not significantly affected by NO3 -, whereas the NO3- uptake rate was considerably reduced in the presence of NH4 +-N. Low energy status of plants affected the nitrate uptake more than the uptake of NH4 +-N. The results show that uptake and assimilation of inorganic N depend much on the energetic status of plants. Nitrate uptake and assimilation is more sensitive to low energy conditions than NH4 +-N.  相似文献   

12.
Abstract

In a pot experiment, the effects of NO3‐N and NH4‐N fertilizer were examined on the pH of the bulk soil and rhizosphere, and on the growth and nutrient uptake of 18–35‐d old bean plants (Phaseolus vulgaris L.) supplied with KH2PO4 or rock phosphate (Hyperphos). Prior to sowing, the soil was incubated for 16 d to ensure complete nitrification of NH4‐N which decreased bulk soil pH from 6.8 to 5.5. In other pots, a nitrification inhibitor, N‐Serve, was added together with the ammonium fertilizer and after 18 d growth, the pH of the bulk soil was 6.6 while the pH of the rhizosphere decreased to 4.5. Shoot and root dry matter yield was significally greater for plants supplied with KH2PO4 and fertilized with NH4‐N compared with NO3‐N. This increased growth by NH4‐N fed plants was presumably due to a increased nutrient availability caused by the acidification of the bulk soil. Shoot concentrations of ? and micronutrients, such as Fe, Mn, Zn, and Cu, were higher for plants supplied with NH4‐N, and more strikingly were higher for plats supplied with NH4‐N+N‐Serve when expressed on a root length basis. In this latter case, the increased nutrient acquisition by plants could only be due to acidification of the rhizopshere. The inhibitory effect of NH4‐N+N‐Serve, particularly on root growth, was not caused by NH4+ toxicity, but was due to a direct effect of N‐Serve as shown by growth comparisons with another nitrification inhibitor, dicyanodiamide (DCD).  相似文献   

13.
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   

14.
Previous experiments have indicated that under greenhouse and hydroponic conditions, spring wheat (Triticum aestivum L.) produces higher yields, more tillers and dry matter when supplied with mixtures of NH4 and NO3 than when supplied with only one of them. The goal of this study was to evaluate the effect of selected ammonium and nitrate mixtures on dry matter yield, content of soluble protein, and phosphoenolpyruvate carboxylase (PEPCase) and glutamine synthetase (GS) enzymatic activities. Cultivar ‘Salamanca’ wheat plants, 21 days old, were grown in one of five solutions containing one of the following: 7/0, 5/2, 3.5/3.5, 2/5 or 0/7 meq l‐1 of NH4NO3.

After two weeks of treatment applications, the highest dry matter production in both roots and shoots of the 35‐day‐old plants was observed in plants receiving the 2/5 NH4/NO3 ratio. The same response was observed on the accumulation of soluble protein and the potential activity of PEPCase. The specific activity of PEPCase was related to the plant applications of ammonium.

Treatments 3.5/3.5 and 2/5 NH4/NO3 ratio enhanced leaf GS activity between 28 and 57 days, and it was consistently 300–500% higher than root activity during the same period. Dry weight of the leaves, stems and grain showed the highest yields with those treatments at the physiological maturity of grains (105 days).  相似文献   

15.
Two hydroponic experiments were carried out to investigate the effects of nitrogen (N) levels and forms on the oxalate concentrations of different form in edible parts of spinach. Nitrogen was supplied at five levels (4, 8, 12, 16, 20 mM) in Experiment 1 and five ratios of nitrate (NO3 ?) to ammonium (NH4 +) (100/0, 75/25, 50/50, 25/75, 0/100) at a total N of 8 mM in Experiment 2. Biomass of spinach increased markedly from 4 mM to 8 mM N and reached the flat with further increase in N. The total oxalate and soluble oxalate in leaves and shoots (edible parts) increased significantly with increasing N levels from 4 to 12 mM, while the total oxalate and insoluble oxalate decreased markedly when N level was further increased from 12 to 20 mM. Oxalates of different forms in petioles increased first and then decreased and elevated again with increasing nitrogen levels. In the second experiment, decreasing NO3 ?/NH4 + ratios markedly increased at first and then significantly decreased the biomass of spinach plants and the maximum biomass was recorded in the treatment of the NO3 ?/NH4 + ratio of 50:50. The oxalate concentrations of different form in leaves and shoots were all decreased obviously as the ratio of NO3 ?/NH4 + decreased from 100:0 to 0:100. Concentrations of total oxalate and soluble oxalate in petioles could be reduced by increasing ammonium proportion and were the lowest as the ratio of NO3 ?/NH4 + was 50:50 and insoluble oxalate decreased as nitrate/ammonium ratio decreased. The concentrations of oxalate forms in leaves were all higher than those in petioles and soluble oxalate was predominant form of oxalates in both trials. It is evident that high biomass of spinach can be achieved and oxalate concentrations of different forms can be reduced by modulating N levels and NO3 ?/NH4 + ratio, so this will benefit for human health especially for those people with a history of calcium oxalate kidney stones.  相似文献   

16.
An investigation was conducted to determine the effect of potassium (K) nutrition on alfalfa (Medicago sativa L.) growth and metabolism of root total nonstructural carbohydrates (TNC) and proteins, and to study whether nitrogen (N) fertilization overcomes N deficiency and low root protein concentrations caused by K deficiency. In Experiment 1, nodulated alfalfa plants were grown in plastic pots containing washed quartz sand and provided minus‐N Hoagland's solution containing 0, 0.6, or 6.0 mM K. Shoot and root K concentrations increased with increasing solution K. Root N concentrations were higher in plants receiving 6.0 mM K than in plants receiving 0.6 or 0 mM K, but shoot N concentrations were similar for all treatments. Plant persistence, shoots per plant, and shoot mass increased as solution K levels increased. Root starch concentration and utilization were positively associated with K nutrition. Total amylase activity was higher, but endoamylase activity was lower in roots of plants receiving 6.0 mM K compared to plants receiving 0.6 or 0 mM K. Root soluble protein concentrations were significantly higher in plants receiving 6.0 mM K than in plants receiving 0 or 0.6 mM K. In Experiment 2, plants were supplied with Hoagland's solution containing 10 mM N as ammonium (NH4 +) or nitrate (NO3) with 0,3, or 6.0 mM K. The addition of N increased root N concentrations only in plants receiving 0 mM K. Plant persistence was reduced by NH4 + application, especially in plants receiving 0 or 3 mM K. Root starch concentrations were markedly reduced in plants receiving NH4 + at all K levels. The addition of NO3 had little effect on alfalfa root carbohydrate and protein metabolism and subsequent shoot growth. Potassium deficiency reduced starch and protein concentrations in roots; factors that were associated with poor persistence and slow shoot regrowth of alfalfa.  相似文献   

17.
Zucchini squash (Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO3):ammonium (NH4) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO3:NH4 ratio (1:0, 1:1, 1:3, or 3:1) treatments. Changing the original nitrogen (N) form ratio significantly affected plant growth, fruit yield, nutrient element, and water uptake. Growth of plants was better when NO3‐N (1:0) was the sole form of N than when NH4‐N was part of the N treatment. Fruit yields for plants fertilized with 1:0 or 1:3 N‐form ratio were double those of plants grown continuously with 3:1 N ratio. The largest leaf area and plant water use were obtained with 1:0 N ratio treatment Total uptake of calcium (Ca), magnesium (Mg), and potassium (K) decreased with increasing NH4‐N proportion in the nutrient solution which suggest NH4‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO3‐N source fertilizer through the vegetative growth stage and by shifting the NO3:NH4 ratio during the reproductive phase.  相似文献   

18.
Tomato plants were grown in sand culture with NH4 or NO3 forms of N and at two levels of light. Plants were harvested at 0, 5, 9, or 12 days after starting treatments. NH4‐N nutrition reduced growth, suppressed K, Ca, and Mg accumulation in shoot, increased P and N content and markedly reduced K, Ca, and Mg uptake per unit of root surface. Reduced light level decreased the toxic effects of NH4 and markedly decreased NH4 accumulation in shoots.  相似文献   

19.
Under greenhouse conditions, a study was made on the effects of nitrogen (N) source (N)O3 or NH4), mode of application (single vs. split) and nitrification inhibition on the N‐uptake and metabolism, of bahiagrass.

Variations in light and temperature in the greenhouse affected the N‐metabolism of bahiagrass plants. Nitrate fed plants had nitrate reductase activity (NRA) pattern different from that of NH4‐fed plants. Amino‐N accumulation patterns were similar for plants under both N‐sources, although amino‐N levels in leaves of NH4‐fed plants were much smaller than that of NO3 plants. Nitrate accumulation in leaves showed inverse trend to that of roots in plants fed both NO3 or NH4. To the sharp peaks in NO3 levels in roots due to increases in light and temperature corresponds a sharp decrease of its levels in leaves.

For both both NO3 or NH4 treatments, soluble‐N accumulated most in the rhizomes of bahiagrass plants, whereas protein N accumulated most in leaves, suggesting that rhizomes had a buffering effect on the NO3 fluxes to leaves. This presumably resulted in a lag in the NRA response of the NO3‐fed plants to increases in light and temperature.  相似文献   


20.
The effects of different forms and concentrations of N in the rooting medium on the CO2/H2O gas exchange of leaves of the pedunculate oak (Quercus robur L.) were investigated. Two-year-old seedlings were grown in nutrient solutions containing low (1.8 mM) or high (4.8 mM) concentrations of NH4+, 3.6 mM NO3?, or both NH4+ and NO3? (1.8 mM + 1.8 mM). In various sets of plants subjected to these N treatments, the following parameters were determined: biomasses of leaves and fine roots, leaf area-related net photosynthesis at light saturation (A) and leaf conductance (g), foliar concentrations of chlorophylls, N, Ca2+, Mg2+ and K+ and the ash alkalinity of the leaves (as a measure of the carboxylate content). In all treatments, the leaves were equally well supplied with nutrients. Oaks grown in high NH4+ concentrations produced significantly smaller leaf and root biomasses. Compared to oaks cultivated with both N forms or with low NH4+ concentration, oaks grown with high NH4+ supply showed lower values of A and g, but no significant differences in ash alkalinity and leaf area-related chlorophyll concentrations. Oaks fed with NO3? as the only N form had an intermediate biomass production, but low values of A and g. The time courses of A in the different treatments closely followed the patterns of g. In all N treatments, the same linear relationship was found between A and g, indicating that, within a rather wide range, the variation in the form and amount of supplied N does not affect the instantaneous water use efficiency of young pedunculate oaks.  相似文献   

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