共查询到20条相似文献,搜索用时 475 毫秒
1.
Most plants can use either nitrate (NO 3) or ammonium (NH 4) as a source of nitrogen. However, the degree of effectiveness of these two forms on plant growth and nutrient uptake is dependent on plant species and NH 4.: NO 3 ratio. The 77: 77 ppm NH 4: NO 3‐N concentration ratio in solution caused the most growth reduction for cabbage, melon, and corn, with corn being least affected. Bean seems to be well adapted to the use of NH 4, and was unaffected by equal concentrations of NH 4: NO 3‐N. The presence of 28 ppm NH 4‐N in the mixture reduced only cabbage growth, whereas growth of melon, bean and com was not affected. All of the species studied responded to the NH4 concentration increase by an increase in anion content in their leaf tissues. The K content in melon and corn leaf was increased with NH 4‐N up to 28 ppm. The K content in tomato and cabbage tissue was reduced at 28 ppm NH 4. The K content in all the species tested was reduced with 77: 77 ppm NH 4: NO 3‐N concentration treatment. Calcium composition reduction in all the plant species was affected at 28 ppm NH 4‐N with reduction to 50% that of all NO 3 nutrition at 77 ppm NH 4‐N. Magnesium composition of corn tissue was most severely reduced by the 77: 77 ppm NH 4: NO 3‐N nutrition. Bean Mg composition was not affected by the NH 4‐N concentration in the 14 to 77 ppm range. Magnesium was reduced in cabbage, melon, and corn by NH 4‐N concentrations above 28 ppm. 相似文献
2.
Zucchini squash ( Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO 3):ammonium (NH 4) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO 3:NH 4 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 NO 3‐N (1:0) was the sole form of N than when NH 4‐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 NH 4‐N proportion in the nutrient solution which suggest NH 4‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO 3‐N source fertilizer through the vegetative growth stage and by shifting the NO 3:NH 4 ratio during the reproductive phase. 相似文献
3.
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 (NH 4:NO 3) 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 NH 4 or NH 4:NO 3 nutrition; pH increased when NO 3 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 cm 2 and dry weight was 1.0, 12.9, 38.0, and 26.0 g/plant, with NH 4:NO 3 100:0, 70:30, 30:70, and 0:100, respectively. Leaf area ratio (LAR) was lower in plants supplied solely with NO 3 than in those with mixed NH 4‐NO 3. Increasing NO 3‐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 NH 4:NO 3 ratio, respectively. Increasing NO 3 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 NO 3 assimilation in artichoke. By increasing NH 4 percentage in the nutrient solution, the tissue content of inorganic anions was generally increased, except for NO 3, and the same figure was observed for the percentage of reduced N. Results from this study suggest that NO 3 is the N‐form preferred by artichoke. 相似文献
4.
Physiological responses of plants to ammonium (NH 4) versus nitrate (NO 3) nutrition can vary considerably. A greenhouse study was conducted to examine the effect of ammonium‐nitrogen/nitrate‐nitrogen (NH 4‐N/NO 3‐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 NH 4‐N/NO 3‐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 NH 4‐N/NO 3‐N ratio than when supplied with the other N treatments. Corn supplied with 8:1 and 1:1 ratios of NH 4‐N/NO 3‐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 NO 3. 相似文献
5.
Abstract Seedlings of four maize hybrids were grown hydroponically to investigate the impact of different N sources (Ca(NO 3) 2, (NH 4) 2SO 4 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), NO 3‐fed plants were superior. In contrast, the mixture of NH 4 and NO 3 ? 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 NH 4‐N. 相似文献
6.
Fertigation with KNO 3 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 NH 4 +/NO 3 ‐ 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 NH 4 + and NO 3 ‐, 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 NH 4 + 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 NH 4 +/NO 3 ‐ 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 NH 4 + concentration, by alteration of the cation‐anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH 4 + concentration. 相似文献
7.
Plant nitrogen (N) uptake, growth, and N use efficiency may be affected by N form (NO 3 ‐or NH 4 +) available to the root. The objectives of this study were to determine the effect of mixed N form on dry matter production and partitioning, N uptake, and biomass N use efficiency defined as total dry matter produced per unit plant N (NUE 1) in U.S. and tropical grain sorghums [Sorghum bicolor (L.) Moench]. The U.S. derived genotype CK 60 and three tropical genotypes, Malisor‐7, M 35–1, and S 34, were evaluated in a greenhouse trial using three nutrient solutions differing in their NO 3 ‐/NH 4 + ratio (100/0, 75/25, 50/50). Shoot and root biomass, N accumulation, and NUE, were determined at 10‐leaf and boot stages. Averaged over all genotypes, shoot and root biomass decreased when NH 4 + concentration was increased in the solution. Shoot biomass was reduced by 11% for 75/25 and 26% for 50/50 ratios, as compared to 100/0 NO 3 ‐/NH 4 +. Similarly, root biomass reduction was about 34% and 45% for the same ratios, respectively. Increasing NH 4 + concentration also altered biomass partitioning between shoot and root as indicated by decreasing root/shoot ratio. Total plant N content and NUE 1 were also reduced by mixed N source. Marked genotypic variability was found for tolerance to higher rates of NH 4 +. The tropical line M 35–1 was well adapted to either NO 3 ‐ as a sole source, or to an N source containing high amounts of NH 4 +. Such a characteristic may exist in some exotic lines and may be used to improve genotypes which do not do well in excessively wet soil conditions where N uptake can be reduced. 相似文献
8.
Abstract Plant growth in saline soils is regulated by the availability of nitrogen (N). High soil nitrate (NO 3)‐N can lead to poor water quality. Many workers think that NO 3‐N as a source for N can contribute to better plant growth in saline soils. The purpose of this work was to determine the necessity of NO 3‐N and the ratio of NO 3/ammonium (NH 4) in the N fertilizer which gives higher productivity of the biomass yield of corn. Corn ( Zea mays L.) plants (Var. LG11) were grown under saline soil conditions (8.5 dS m ‐1), soils taken from the Euphrates valley (ACSAO Research Station) at Deir‐Ez‐Zor, east of Syria, from the surface layer of soil (0–25 cm). Five levels of N were applied in two forms, ammonium sulfate [ 15(NH 4) 2SO 4] with enrichment (1.5% a) as the NH 4‐N form and calcium nitrate [Ca(NO 3) 2] as the NO 3‐N form, besides fixed amounts of phosphorus (P) and potassium (K) for all N treatments. The corn plants were harvested at the flowering stage (56 days old), oven dried, weighed, and analyzed for total N and 15N recovery. The results indicated that the dry matter weight for treatments which received a combination of NH 4‐N and NO 3‐N gave higher dry matter yield than a single treatment of one source of N. But, NO 3‐N was more effective in improving yield than NH 4‐N. Nitrogen recoveries on the basis of added and absorbed N derived from fertilizer were significantly more affected by NO 3‐N than NH 4‐N. 相似文献
9.
Maize ( Zea mays L. cv. Anjou 256) seedlings were grown hydroponically for 10 d in a split‐root system (3mM N; pH 5.5) under either a homogeneous supply (HS) or a simultaneous, but spatially separated supply (SS) of NH 4 + andNO 3 ‐. Treatments comprised three NH 4 +:NO 3 ‐ ratios (1:4, 1:1, 4:1). Shoot dry matter and various root traits (dry matter, number of laterals, length of main axes, total root length and total root surface area) were determined. For all NH 4 +:NO 3 ‐ ratios, shoot dry matter, root dry matter, total root length, and root surface area, were greater under HS than under SS. Under both SS and HS, increasing NH 4 +:NO 3 ‐ ratios resulted in decreased shoot and root dry matter production, but did not alter the shoot:root dry matter ratio. Under SS, root dry matter, root length, and root surface area was greater on the NO 3 ‐‐fertilized side than on the NH 4 + ‐fertilized side. The allocation of root dry matter, root length, and root surface area to the NH 4 + or NO 3 ‐ compartments was unaffected by changes in the NH 4 +:NO 3 ‐ ratio. Enhanced NH 4 + nutrition has detrimental effects on top growth, but roots are apparently unable to avoid excessive NH 4 + uptake by proliferating in zones where NO 3 ‐ is the only form of N. 相似文献
10.
We investigated the interacting effects of inorganic nitrogen and the main inorganic phosphorus form in dairy manure (dicalcium phosphate, CaHPO 4) on growth, nutrient uptake, and rhizosphere pH of young maize plants. In a pot experiment, three levels of CaHPO 4 (0, 167, and 500 mg P pot ?1) were combined with nitrogen (637 mg N pot ?1) applied at five NH 4‐N : NO 3‐N ratios (0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0) and a nitrification inhibitor in a concentrated layer of a typical acid sandy soil from Denmark. 15N‐labeled NH 4‐N was applied to differentiate the role of nitrification and to partition nitrogen uptake derived from NH 4‐N. Among treatments including nitrogen, shoot biomass, rooting and phosphorus uptake were significantly higher at the five‐leaf stage when CaHPO 4 was applied with NH 4‐N : NO 3‐N ratios of 50 : 50 and 75 : 25. In these treatments, rhizosphere pH dropped significantly in direct proportion with NH 4‐N uptake. The fertilizers in the concentrated layer had a root‐inhibiting effect in treatments without phosphorus supply and in treatments with pure NO 3‐N or NH 4‐N supply. Increased nitrogen uptake as NH 4‐N instead of NO 3‐N reduced rhizosphere pH and enhanced acquisition of applied CaHPO 4 by young maize plants, which may have positive implications for the enhanced utilization of manure phosphorus. 相似文献
11.
Abstract To evaluate the chance to reduce leaf NO 3 content and to increase capability to use NH 4‐N even in the absence of NO 3‐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 NH 4‐N: NO 3‐N (NH 4: NO 3) 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 NH 4 nutrition and reached the highest values with the NH 4: NO 3 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 NO 3‐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 NO 3‐N than NH 4‐N when N was administered in mixed form. In the best conditions of N nutrition, Swiss chard accumulated NO 3 in leaves in high concentration (3,809 mg kg" 1 fresh mass). On average, fennel and celery accumulated 564 mg NO 3 kg ?1 fresh mass with the ratio NH 4: NO 3100: 0 and showed that by using NH 4 produce having very low NO 3 content can be obtained. By increasing NO 3‐N percentage in the nutrient solution; NO 3 leaf content of fennel and celery increased remarkably (7,802 mg kg ?1 fresh mass with the ratio N H 4: NO 3 0: 100). 相似文献
12.
Abstract Soil nitrate test reports are being used more widely for making nitrogen fertilizer recommendations. Seldom does the literature refer to the ammonium concentration in the soil. Seemingly, an assumption is made that the level is insignificant or a constant. Selected soils upon which both NO 3‐N and NH 4‐Nwere analyzed were surveyed to determine the degree of variation that is found in routine soil samples from different situations. Our 134 sets of data were divided into groups by area (state) and date (month sampled). Group means and standard deviations, medians, coefficient of variations (C.V.), and ranges were determined for soil nitrate nitrogen (NO 3‐N), ammonium‐nitrogen (NH4‐N), sum of NO 3‐N + NH 4‐N (Sum N), % of N found as NO 3‐N, and ratio of NH 4‐N/ NO 3‐N. Values varied widely with date of sampling within areas as well as among areas. Observed values ranged as follows: NO 3‐N from 2 to 83 ppm, NH 4‐N from 4 to 30 ppm, sum of N from 9 to 91 ppm, % of N as NO 3‐N from 15 to 91% and NH 4‐N/NO 3‐N ratio from 0.1 to 5.5. C.V.’s ranged from 10 to 133% and were highest for NO 3‐N and NH 4‐N/NO 3‐N ratios and lowest for NH 4‐N and % NO 3‐N data. The survey data suggests that nitrogen fertilizer recommendations could be improved if the NH 4‐N were considered along with the NO 3‐N levels for predicting response to nitrogen fertilization. A method for determining both soil NO 3‐N and NH 4‐N from a single extract is described. 相似文献
13.
To evaluate chicory ( Cichorium intybus L.) and rocket salad [ Eruca vesicaria (L.) Cav.subsp. sativa (Mill.)] capability to use ammonium‐nitrogen (NH 4‐N) even in the absence of nitrate‐nitrogen (NO 3‐N) in the nutrient solution, and the chances they offer to reduce leaf NO 3 content, cultivated rocket and two cultivars of chicory ('Frastagliata’, whose edible parts are leaves and stems, and ‘Clio’, a leaf hybrid) were hydroponically grown in a growth chamber. Three nutrient solutions with the same nitrogen (N) level (4 mM) but a different NH 4‐N:NO 3‐N (NH 4:NO 3) ratio (100:0, 50:50, and 0:100) were used. Rocket growth was inhibited by NH 4 nutrition, while it reached the highest values with the NH 4:NO 3 ratio 50:50. Water and N‐use efficiencies increased in rocket with the increase of NO 3‐N percentage in the nutrient solution. In the best conditions of N nutrition, however, rocket accumulated NO 3 in leaves in a very high concentration (about 6,300 mg kg ‐1 fresh mass). For all the morphological and yield features analyzed, chicory resulted to be quite unresponsive to N chemical forms, despite it took more NO 3‐N than NH 4‐N when N was administered in mixed form. By increasing NO 3‐N percentage in the nutrient solution, NO 3 leaf content increased (5,466 mg kg ‐1 fresh mass with the ratio NH 4:NO 3 0:100). On average, both chicory cultivars accumulated 213 mg NO 3 kg ‐1 fresh mass with the ratio NH 4:NO 3 100:0 and, differently from rocket, they showed that by using NH 4 produce can be obtained very low in NO 3 content. 相似文献
14.
In a greenhouse, radish (Raphanus sativus L.), corn (Zea mays L.), soybean (Glycine max Merr), and wheat (Triticum aestivum L.) were grown in soil‐based medium with captan at 60 mg/kg and truban at 30 mg/kg and with different levels of N from (NH 4) 2SO 4 or NaNO 3. Growth of radish, soybean, and corn was restricted by NH 4‐N compared with NO 3‐N. Captan and truban stunted growth of radish and soybean. As NH 4‐N or NO 3‐N fertilizer increased, the concentration of Ca and Mg in all plants decreased, and the percentage of K in corn, soybean, and wheat increased. Application of captan and truban increased all cation concentrations in corn, wheat, and soybean but decreased Ca concentration in radish. The amount of residual NH 4‐N in the medium supplied with (NH 4) 2SO 4 was increased by application of captan or truban. Captan increased the residual NO 3‐N in the medium treated with NaNO 3. Chemical names used: captan, (N‐(trichloro)methylthio)‐4‐cyclo‐hexene‐l, 2‐dicarboximide); truban, (5‐ethoxy‐3‐trichloromethyl‐l, 2, 4,‐thiadiazole). 相似文献
15.
Water‐soluble nitrogen (N) fertilizer is intensively used in greenhouse crop production. Any N not used by a crop is subject to leaching as nitrate (NO 3‐N), which may pollute groundwater. A close correlation between N supply and N uptake by plants would increase the efficiency of N fertilization and minimize the possibility of NO 3‐N pollution. The objectives of this study were to measure N uptake by American marigold ( Tagetes erecta L. ‘First Lady') and New Guinea Impatiens (NGI) ( Impatiens hawkeri Bull. ‘Selenia') during growth, to determine the effect of plant age on N uptake, to determine if the two species have a preference for NO 3‐N or ammonium (NH 4‐N), and to determine the total N required for 70 days of growth.The plants were grown in solution culture using solutions supplying 120 mg each of NO 3‐N and NH 4‐N. At ten day intervals, six cultures were chosen at random for nutrient solution analysis and plant sampling for dry weight and tissue analysis. Nitrate‐N uptake was greater than NH 4‐N uptake throughout the experiment for both marigold and NGI. Total N uptake by marigold was greater during the first 50 days after transplanting with maximum N uptake during the period 30 to 50 days. In contrast, N uptake by NGI was greater during the period 40 to 70 days after transplanting. Maximum N uptake for NGI occurred during the period 60 to 70 days. Results of this study suggest that early N fertilization of marigold could be more important for their growth and quality than N applied later. For NGI, N fertilization later in the crop's development appears to be more important than early on. The total N absorbed by marigold during the experiment was 1.1 gm N plant ‐1; for NGI the quantity was 0.5 gm N plant‐ 1. 相似文献
16.
The influence of nitrogen (N) forms and chloride (Cl) on solution pH and ion uptake in the hydroponic culture of Ageratum houstonianum [ammonium (NH 4 +)‐tolerant] and Salvia splendens (NH 4 +‐sensitive) for a period of 216 hours was investigated. The pH of the hydroponic solution (initially 6.50) containing either NH 4 + or NH 4 ++nitrate (NO 3 ‐) was drastically lowered (3.08), whereas that of the same solution containing NO 3 ‐ was raised (7.74). Solution pH changed more by ageratum than by salvia. The solution Cl ‐ concentration did not influence pH significantly. However, addition of Cl ‐ in the solution lowered transpiration rate in both NH 4 + and NO 3 ‐ treatments. Total N uptake was the greatest in the NH 4 + + NO 3 ‐ treatment and the lowest in the NO 3 ‐treatment. In the NH 4 + + NO 3 ‐ treatment, NO 3 ‐ uptake was suppressed by NH 4 + (to about 50%), while NH 4 + uptake was not affected by NO 3 ‐. The rate of Cl ‐ uptake was the lowest in the NH 4 + treatment, but was similar in the NH 4 + + NO 3 ‐ and NO 3 ‐ treatments. Uptake of potassium (K +), dihydrogen phosphate (H 2PO 4 ‐), sulfate (SO 4 ‐2), manganese (Mn +2), and zinc (Zn +2) was significantly enhanced in the NH 4 + treatment. The uptake rate of calcium (Ca +2) and magnesium (Mg +2) was the highest in the NO 3 ‐ treatment. Absorption of copper (Cu +2) and boron (B) was not affected by N source. Ion uptake was more stable in the solution containing both NH 4 + and NO 3 ‐ than in the solution containing either NH 4 + or NO 3 ‐. The uptake rate of total N, NH 4 +, NO 3 ‐, Mn +2, Cu +2, and Zn +2 was higher, whereas that of Cl ‐ and molybdenum (Mo) was lower in ageratum than in salvia. Amounts of total anion (TA) and total cation (TC) absorbed, the sum of TC and TA, and the difference between TC and TA (TC‐TA) were affected by N source, Cl ‐ level, and their interactions. The NO 3 treatment, as compared to the NH 4 + or the NH 4 + + NO 3 ‐treatment, reduced total cation and anion uptake while increasing TC‐TA, especially in the absence of Cl ‐. Plant tissue ion contents were also affected by N source and Cl ‐ level. 相似文献
17.
Chickpea plants ( Cicer arietinum L cv. ILC 195) were grown for 24 days in water culture under two regimes of nitrogen nutrition (NO 3 or NH 4‐N) with or without Fe. For plants fed with NO 3‐N, Fe stress severely depressed fresh weight accumulation and chlorotic symptoms of Fe‐deficiency developed rapidly. Little difference in growth occurred in the NH 4‐fed plants, whether or not Fe was withheld, with no visual evidence of Fe‐deficiency indicating a beneficial effect of NH 4 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 NO 3 and decreasing with NH 4‐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 NO 3‐fed plants the uptake of all nutrients was reduced by the stress but proportionally NO 3‐ and K + were most affected. Total anion uptake was depressed more than that of cation uptake. For the NH 4‐fed plants withholding Fe resulted in an increased uptake of all ions except NH 4 + 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 NO 3‐fed plants, indicating a role for these internally produced anion charges in balancing cation charge in relation to the depression of NO 3 ‐ uptake associated with Fe‐stress. 相似文献
18.
Tomato plants were grown in sand culture with NO 3 or NH 4 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
19.
Abstract The effect of soil pH on the exchangeability and solubility of soil cations (Ca, Mg, Na, K, and NH 4‐N) and anions (NO 3‐N, Cl, and P) was investigated for 80 soils, spanning a wide range in physical and chemical properties and taxonomic groups. This information is needed from environmental and agronomic standpoints to estimate the effect of changes in soil pH on leachability and plant availability of soil nutrients. Soils were incubated with varying amounts of acid (H 2SO 4) and base (CaCO 3) for up to 30 days. Although acid and base amendments had no consistent effect on cation exchangeability (as determined by neutral NH 4OAc), amounts of water‐soluble Ca, Mg, Na, K, NH 4‐N, and P decreased, while NO 3‐N and Cl increased with an increase in soil pH. The increase in cation solubility was attributed to an increase in the negative charge of the soil surface associated with the base addition. The change in surface electrostatic potential had the opposite effect on amounts of NO 3‐N and Cl in solution, with increases in N mineralization with increasing soil pH also contributing to the greater amount of NO 3‐N in solution. The decrease in P solubility was attributed to changes in the solubility of Fe‐, A1‐, and Ca‐P complexes. The logarithm of the amount of water‐soluble cation or anion was a linear function of soil pH. The slope of this relationship was closely related (R 2 = = 0.90 ‐ 0.96) to clay content, initial soil pH, and size of the cation or anion pool maintaining solution concentration. Although the degree in soil pH buffering increased with length of incubation, no effect of time on the relationship between cation or anion solubility and pH was observed except for NO 3‐N, due to N mineralization. A change in soil pH brought about by acid rain, fertilizer, and lime inputs, thus, affects cation and anion solubility. The impact of these changes on cation and anion leachability and plant availability may be assessed using the regression equations developed. 相似文献
20.
Growth, development, and uptake of essential nutrients as influenced by nitrogen (N) form and growth stage was evaluated for ‘Freedom’ poinsettias (Euphorbia pulcherrima Willd. Ex Klotz.). Treatments consisted of five nitrate (NH 4 +):ammonium (NO 3 ‐) ratios (% NH 4 +:% NO 3 ‐) of 100:0, 75:25, 50:50, 25:75, and 0:100 with a total N concentration of 150 mg L ‐1. Plants were grown in solution culture for ten weeks under greenhouse conditions. Nutrient uptake data was combined into three physiological growth stages. Growth stage I (GSI) included early vegetative growth (long days). Growth stage II (GSII) began at floral induction and leaf and bract expansion (short days). Growth stage III (GSIII) was from visible bud through anthesis and harvest. Dry weights for all plant parts and height increased as the ratio of NO 3 ‐ increased. Leaf area and bract area were maximized with 25:75 and 50:50 N treatments, respectively. Nitrogen treatments significantly affected foliar nutrient concentrations with calcium (Ca ++) and magnesium (Mg ++) being highest when NO 3 ‐ was the predominant N form. Uptake of each macronutrient was averaged across all treatments and divided into physiological growth stages (GS) to identify peak demand periods during the growth cycle. The greatest uptake of NH 4 + and NO 3 ‐ was from the early vegetative stage to floral induction (GSI). Phosphorus (P), potassium (K +), and Mg ++ uptake were greatest from floral induction to visible bud (GSII) and Ca ++ uptake remained relatively unchanged through GSI and GSII. Uptake was lowest for all nutrients from visible bud to anthesis (GSIII). Results from this study clearly indicate that peak demand periods for macronutrient uptake existed during the growth cycle of poinsettia. 相似文献
|