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1.
A pot experiment was conducted using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) amended with either citrus leaves or compost, to measure the nitrogen (N) mineralization and its availability to two citrus rootstock seedlings. A rapid increase in NH 4‐N concentration was evident in the soil amended with citrus leaves as compared to compost during the initial 14 to 20 d. Subsequently, the concentration of NH 4‐N decreased in the citrus leaves amended soil. The extractable NO 3‐N concentration was greater in the soil amended with citrus leaves as compared to compost, throughout the 270 d duration of the study. The N concentrations and N uptake by Cleopatra mandarin (CM) and Swingle citrumelo (SC) seedlings grown in citrus leaf amended soil were very similar to those in urea amended soil. Therefore, mineralization of N from dry ground citrus leaves was quite rapid. The N concentrations in both rootstock seedlings were much lower in the compost amended and unamended soils as compared to those in either citrus leaves or urea amended soils. Rapid mineralization of N from cirrus leaves added to sandy soil, resulting in an increased availability of N, suggested that the contribution of N from shed leaf mineralization must be considered while developing N rate recommendations for improving N use efficiency. 相似文献
2.
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
3.
Abstract Combinations of NH 4‐N:NO 3‐N usually result in higher tomato (Lycopersicon esculentum Mill.) yields than when either form of nitrogen (N) was used alone. Leaf chlorophyll content is closely related to leaf N content, but the effect of the NH 4‐N:NO 3‐N ratio on leaf greenness was not clear. The objective of this study was to determine the influence of NH 4‐N:NO 3‐N ratios on chlorophyll meter (SPAD) readings, and evaluate the meter as a N status estimator and tomato yield predictor in greenhouse production systems. Fruit yield and SPAD readings increased as the amount of NH 4‐N in solution increased up to 25%, while higher ratios of NH 4‐N resulted in a decline in both. The N concentration in tomato leaves increased as concentration of NH 4‐N in solution increased. Fruit yield increased as chlorophyll readings increased. SPAD readings, total N in leaves, fresh weight of shoots, and fruit yield all showed a quadratic response to NH 4‐N, reaching a peak at 25 or 50% of N as NH 4‐N. SPAD readings taken at the vegetative and flowering stages of growth had the highest correlation (r 2=0.54) with N concentration in leaves, but this could not be used as a reliable estimate of N status and fruit yield. Lack of correspondence between high N concentration values and fruit yield indicated a detrimental effect of NH 4‐N on chlorophyll molecules or chloroplast structure. The SPAD readings, however, may be used to determine the optimum NH 4‐N concentration in solution to maximize fruit yield. 相似文献
4.
The effect of elevated nitrate [(NO 3‐nitrogen (N)] or ammonium (NH 4)‐N on the response of nonmycorrhizal (NM) and ectomycorrhizal (ECM) pitch pine (Pintis rigida Mill.) seedlings to aluminum (Al) was determined in experiments in which N was increased three times above ambient levels. Seedlings with and without the mycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch were grown in sand irrigated with nutrient solution (pH 3.8) containing 0, 10, or 20 mg Al L ‐1 (0, 370, or 740 μM Al). The nutrient solution simulated that for the sandy, nutrient‐poor soil of the New Jersey Pine Barrens. Elevated NO 3‐N had no significant effect on Al toxicity in NM seedlings, but Al toxicity at ambient NH 4‐N was ameliorated by elevated NH 4‐N. Symptoms of Al toxicity in roots (thick and stunted) of ECM seedlings at ambient N levels were reduced by elevated NH 4‐N and absent at elevated NO 3‐N. When N was elevated by an increase in NO 3‐N or NH 4‐N, uptake of N and relative increases in total biomass were greater in ECM than in NM seedlings. 相似文献
5.
Abstract The form of nutrient solution nitrogen (either NH 4‐N or NO 3‐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 NO 3‐N to NH 4‐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 NO 3‐N to NH 4‐N (100% NO 3, 50:50 NH 4:NO 3, or 100% NH 4) for a 30‐d period, after which plant height and tillers plant ?1 were measured. Oat and wheat plants given NH 4 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 NO 3 nutrient solution until plant maturity, after which days to anthesis, primary tiller height, grain yield and yield components were measured. In the NH 4 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 NO 3 or NH 4NO 3 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
6.
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
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 (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
8.
The effect of suboptimal supply of nitrogen (N) and of replacing nitrate in the nutrient solution with ammonia on growth, yield, and nitrate concentration in green and red leaf lettuce was evaluated over two seasons (autumn and spring) using multiple regression analysis. The plants were grown in a greenhouse on a Nutrient Film Technique (NFT) system. Nitrogen concentrations in the nutrient solution were either 3?mM or 12?mM, and the form of N was varied as follows: 100% NO 3, 50% NO 3?+?50% NH 4, and 100% NH 4. In both seasons, the biomass (fresh weight) of lettuce heads increased with increasing NO 3 concentrations and in autumn, NO 3 even at 1.5?mM was sufficient for high yield. However, head dry weight was affected neither by the season nor by changes in the composition of the nutrient solution. The concentration of NO 3 had no effect on root dry weight, but it decreased at higher concentrations of NH 4. The number of leaves increased as the ratio of NO 3 to NH 4 in the nutrient solution increased and was higher in autumn because of the longer growth period. Increasing the concentration of NO 3 in nutrient solution increased both total N and nitrate concentration in lettuce heads (dry weight) but decreased the concentration of total C. Also, leaf nitrate concentration was lower in spring than in autumn and decreased with increasing NH 4 concentration. Nitrogen utilization efficiency was maximum when NH 4 levels in the nutrient solution were either 0% or 50% irrespective of the season. Our results thus show that suboptimal N supply in autumn will not affect lettuce yield, and that nitrate concentration in leaves is lower when NH 4 concentrations in nutrient solution are higher and also much lower in red lettuce than in green lettuce. 相似文献
9.
Effects of varying the proportions of NO 3— and NH 4+ in the growth medium on seedling growth and tomato fruit yield ( Lycopersicon esculentum L. cv. Trust F1) were investigated in greenhouse hydroponic experiments. The presence of NH 4+ as the sole N source (11 mM) was toxic: it curtailed growth and decreased chlorophyll content of the leaves. However, at low concentration (10 % of total N), the presence of NH 4+, with or without added dissolved inorganic carbon (DIC), increased vegetative growth and fruit yield by ˜ 15 %, and enhanced taste/flavor of the fruits. In DIC‐enriched treatment, pH was maintained at 5.8 by addition of KHCO 3 or as CaCO 3. The presence of NH 4+, at 10 % of total N, inhibited NO 3— uptake rates by ˜ 27 %. The rates of uptake of NO 3— and NH 4+ were comparable (13.3 and 14.2 mmol plant —1 d —1, respectively, in the presence of DIC, and 14.7 and 14.0 mmol plant —1 d —1, respectively, in the absence of DIC), despite such a large difference in their concentrations in the nutrient feed solution. A higher proportion of NH 4+ (up to 50 % of total N) had no further significant effect upon early vegetative growth, but in a long‐term experiment resulted in a high incidence of blossom end‐rot (BER) disease, thereby severely curtailing fruit yield. The presence of even 1.1 mM NH 4+ reduced Ca 2+ and Mg 2+ accumulation in the leaves as well as in fruits. 相似文献
10.
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
11.
The objective of this research was to study the effects of nitrogen (N) forms (NO 3–, 2.6 mM; NH 4+, 2.6 mM; NO 3–, 1 mM + NH 4+, 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 NH 4‐treated plants were significantly higher compared to the NO 3– 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 NH 4‐N form significantly reduced the Mg concentration of the leaves. 相似文献
12.
Abstract Nitrite (NO 2 ?‐N) toxicity symptoms have been observed on lettuce ( Lactuca sativa) at various locations in California. The objective was to evaluate the symptoms of ammonium (NH 4 +‐N) and nitrite (NO 2 ?‐N) toxicity on Sundevil iceberg lettuce and Paragon romaine lettuce and to determine lettuce growth and biomass production under different levels of NO 2 ?‐N. Hydroponic studies under greenhouse conditions were conducted using nutrient solutions containing nitrate (NO 3 ?‐N) and two other forms of nitrogen (NO 2 ?‐N and NH 4 +‐N) applied at a constant concentration (50 mg NL ?1) or using different NO 2 ?‐N levels (0, 5, 10, 20, 30, and 40 mg N L ?1) and a constant NO 3 ?‐N level (30 mg N L ?1). Crown discoloration (brownish color) was observed for lettuce grown in both NO 2 ?‐N and NH 4 +‐N solutions approximately 3 weeks after transplanting into the hydroponic systems. Lettuce grown in NO 3 ?‐N solution produced larger biomass and greater number of leaves per plant than lettuce grown in NO 2 ?‐N or NH 4 +‐N solutions. Increasing the concentration of NO 2 ?‐N suppressed plant height, fresh and dry biomass yield, and number of leaves and increased the root vascular discoloration. Lettuce growth was reduced more than 50% at NO 2 ?‐N concentrations greater than 30 mg N L ?1. Even at 5 mg NO 2 ?‐N L ?1, growth was reduced 14 and 24% for romaine and iceberg lettuce, respectively, relative to that obtained in nitrate solution. Although concentrations between 5 and 40 mg NO 2 ?‐N L ?1 reduced dry biomass similarly for both lettuce types, toxicity symptoms were more severe in iceberg lettuce than in romaine. 相似文献
13.
ABSTRACT Black walnut ( Juglans nigra L.) half-sib 1+0 seedlings were exponentially fertilized with ammonium (NH 4 +) as ammonium sulfate [(NH 4) 2SO 4], nitrate (NO 3 ?) as sodium nitrate (NaNO 3), or a mixed nitrogen (N) source as ammonium nitrate (NH 4NO 3) at the rate of 0, 800, or 1600 mg N plant ?1 and grown for three months. One month following the final fertilization, N concentration, growth, and photosynthetic characteristics were assessed. Compared with unfertilized seedlings, N addition increased plant component N content, chlorophyll content, and photosynthetic gas exchange. Net photosynthesis ranged from 2.45 to 4.84 μmol m ?2 s ?1 for lower leaves but varied from 5.95 to 9.06 μmol m ?2 s ?1 for upper leaves. Plants responded more favorably to NH 4NO 3 than sole NH 4 + or NO 3 ? fertilizers. These results suggest that N fertilization can be used to promote net photosynthesis as well as increase N storage in black walnut seedlings. The NH 4NO 3 appears to be the preferred N source to promote black walnut growth and physiology. 相似文献
14.
Abstract The efficient use of N for crop production is important because N is normally the most expensive fertilizer input. Past research has suggested that Ca ++ can be used to stimulate NH 4+ absorption by plants. The importance of plant growth stage in relation to this phenomenon has not been examined previously. The objectives of this study were to examine Ca ++ ‐ stimulated NH 4 + absorption and to examine the effect of Ca ++ concentration on N content and growth in plant tops, bulbs and roots at different growth stages. Ammonium absorption experiments were conducted in the greenhouse in 4‐L pots containing 3.5 kg of calcareous Gila sandy loam (Typic Torrifluvents) (CEC <1 cMol kg ?1). Plants (Radish, Raphanus sativas L., and onion, Allium cepa L.) were grown with a uniform nutrient solution (1/2 strength nutrient solution, all N as NO 3) to the desired growth stage at which time the soil was leached with deionized water. Afterwards, the soils were fertilized with 1/2 strength nutrient solutions (5 mol m ?3 NH 4) with Ca ++: NH 4 + molar ratios of 0, 0.25, 0.50, 1.00, and 2.00 for a period of 30 h. As Ca ++ concentration increased, NH 4 + absorption and plant growth increases were greatest with young seedlings. In the intermediate and mature growth stages, Ca ++ stimulated 15NH 4 + absorption was less rapid than in the earlier growth stages but frequently exhibited a different response (i.e., altered metabolite translocation) to the added Ca ++ ‐ concentration. However, at the intermediate and mature growth stages significantly increased N contents and plant growth also were noted in most cases. The Ca ++ ‐ increased N content in leaves and bulbs of the older plants had much less 15N suggesting that the newly absorbed 15NH 4 + was being deposited in the roots replacing older N forms that were then translocated to the bulbs or leaves. Thus, increasing Ca ++ appeared to have anadditional function of increasing the mobility of metabolites (dry matter) from the roots. Since more above‐ground plant products were produced with the same amount of N, plant N use efficiency was increased. 相似文献
15.
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
16.
Abstract Sorghum [ Sorghum bicolor (L.) Moench] seedlings were grown in nutrient solutions in a growth chamber to investigate the effects of different ratios of NO 3 – and NH 4 + on nutrient solution pH, dry matter yield, and N uptake. Nutrient solutions and plant tissues were assayed throughout the time plants grew in the nutrient solutions. Nutrient solution pH depended on source of N. The pH rose to near 8 with NO 3 – as the sole source of N and decreased to near or below 4 with NH 4 + added to the solutions. Upon depletion of NH 4 + from solution, pH values rose abruptly to near 8 and remained near this value throughout the duration of the experiments. Dry matter yield was generally higher for plants grown with some NH 4 + compared to plants grown with NO 3 – alone. Nitrogen uptake was generally higher in plants grown with the higher proportions of NH 4 +. Nitrogen concentrations remained unchanged with plant age as NO 3 –/ NH 4 + ratio varied. For solutions low in NH 4 +, N concentrations in roots increased with plant age. Severe Fe deficiency appeared in plants when solution pH reached and remained above 7. 相似文献
17.
’Shogoin’ turnip plants (Brassica rapa L.) were grown in sand culture under five nitrate:ammonium (NO 3:NH 4) ratios (N:N of 1:0, 3:1, 1:1, 1:3, 0:1). The leaves expressed symptoms of NH 4 toxicity (reduced growth and curly leaves with dark‐green areas surrounding yellow spots) when NH 4 was the dominant nitrogen (N) form. Increasing NO 3 in the nutrient solution significantly (p<0.01) increased leaf and root fresh weight and dry weight. Leaf nutrient concentration and composition of all elements analyzed, except N and calcium (Ca), responded quadratically (p<0.01) to NO 3:NH 4 ratios, and the highest values were observed with the 1:0 [for molybdenum (Mo)], 3:1 ([or magnesium (Mg)], 1:1 [for boron (B), coper (Cu), iron (Fe), manganese (Mn ), and zinc (Zn)] or 1:3 [for phosphorus (P) and potassium (K)] treatments. Nitrogen and Ca leaf concentration responses were linear and highest at 0:1 and at 1:0, respectively. Cultural practices and fertilizer applications should maintain NO 3 as the dominant N form in the root zone, and the continuous use of NH 4‐ based or NH4‐releasing fertilizers is not recommended for the production of high yields of turnip greens. 相似文献
18.
The effect of NH 4NO 3 (control) and increasing NO 3- levels in nutrient solutions containing no and 100 μM Fe respectively on iron chlorosis of Glycine max was investigated. After two weeks of growth apoplastic pH in excised leaves was measured by means of fluorescence. In plants growing without Fe supply increasing concentrations of NO 3- in the nutrient solution which also was applied to the cut end of the petiole, resulted in a pH increase in the leaf apoplast from 5.34 (NH 4NO 3) to 5.50 (NO 3-) associated with chlorosis observed with intact plants. A close negative correlation was found between chlorophyll concentration and pH in the apoplast (r = ?0.97). While leaves in the treatment exclusively fed with NO 3- were strongly chlorotic, those in the NH 4NO 3 treatment were green. With exception of the plants only fed with NO 3- the Fe concentration in the leaves was not affected by the type of N nutrition. It is therefore assumed that some Fe is immobilized in the leaf tissue by high apoplast pH induced by an increase in the proportion of nitrate in the nutrient solution. Plants fed with Fe (100 μM) showed no chlorosis, regardless of the form of N nutrition and hence regardless of apoplast pH. The Fe concentration in leaves of Fe fed plants was approximately twice those in the leaves not supplied with Fe. 相似文献
19.
Plant growth and metabolism is impaired under stress conditions, resulting in decreased crop yields. The purpose of this investigation was to evaluate the NaCl stress effects on NH + 4 metabolism in cotton plants at vegetative and reproductive stages of growth. Cotton (Gossypium hirsutum L.) plants grown in normal (control) and NaCl treated Hoagland solutions were analyzed for distribution of N15 in NH+ 4 plus amide‐N, free α‐amino‐N, total soluble‐N and protein‐N after the plants were provided 15NH4NO3 in nutrient solutions for 6, 12 and 24 h. The concentration of protein‐15N was enhanced under a low level of NaCl (‐0.4 MPa osmotic potential) at the vegetative growth stage. The difference between the protein‐15N concentration of the moderately salinized (‐0.8 MPa) plants and the controls was not significant. A high level of NaCl (‐1.2 MPa) significantly decreased protein‐N content of plants compared with the controls and any other level of salinity. The NaCl increased accumulation of NH4 + plus amide‐N, free (α‐amino‐N, and total soluble‐N in cotton shoots, at both stages of growth. Low osmotic potential (high osmotic pressure) of the nutrient solution induced by excessive amounts of NaCl in nutrient solution inhibited NH+ 4 metabolism and decreased protein synthesis, thus resulting in accumulation of soluble N‐compounds. The ionic effect probably contributed also to inhibition of protein synthesis. 相似文献
20.
Understanding the fate of different forms of nitrogen (N) fertilizers applied to soils is an important step in enhancing
N use efficiency and minimizing N losses. The growth and N uptake of two citrus rootstocks, Swingle citrumelo (SC), and Cleopatra
mandarin (CM), seedlings were evaluated in a pot experiment using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments)
without N application or with 400 mg N kg –1 applied as urea or controlled-release fertilizers (CRF; either as Meister, Osmocote, or Poly-S). Meister and Osmocote are
polyolefin resin-coated urea with longevity of N release for 270 days (at 25°C). Poly-S is a polymer and sulfur-coated urea
with release duration considerably shorter than that of either Meister or Osmocote. The concentrations of 2 M KCl extractable
nitrate nitrogen (NO 3
–-N) and ammonium nitrogen (NH 4
+-N) in the soil sampled 180 days and 300 days after planting were greater in the soil with SC than with CM rootstock seedlings.
In most cases, the extractable NH 4
+ and NO 3
– concentrations were greater for the Osmocote treatment compared to the other N sources. For the SC rootstock seedlings, dry
weight was greater with Meister or Poly-S compared with either Osmocote or urea. At the end of the experiment, ranking of
the various N sources, with respect to total N uptake by the seedlings, was: Meister = Osmocote > Poly-S > Urea > no N for
CM rootstock, and Meister = Poly-S = Osmocote > Urea > no N for SC rootstock. The study demonstrated that for a given rate
of N application the total N uptake by seedlings was greater for the CRF compared to urea treatment. This suggests that various
N losses were lower from the CRF source as compared to those from soluble fertilizers.
Received: 11 April 1997 相似文献
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