首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Lainé  P.  Ourry  A.  Boucaud  J.  Salette  J. 《Plant and Soil》1998,202(1):61-67
Roots of higher plants are usually exposed to varying spatial and temporal changes in concentrations of soil mineral nitrogen. A split root system was used to see how Lolium multiflorum Lam. roots adapt to such variations to cope with their N requirements. Plants were grown in hydroponic culture with their root system split in two spatially separated compartments allowing them to be fed with or without KNO3. Net NO3 - uptake, 15NO3 - influx and root growth were studied in relation to time. Within less than 24 h following deprivation of KNO3 to half the roots, the influx in NO3 - fed roots was observed to increase (about 200% of the influx measured in plant uniformly NO3 - supplied control plant) thereby compensating the whole plant for the lack of uptake by the N deprived roots. Due to the large NO3 - concentrations in the roots, the NO3 - efflux was also increased so that the net uptake rate increased only slightly (35% maximum) compared with the values obtained for control plants uniformly supplied with NO3 -. This increase in net NO3 - uptake rate was not sufficient to compensate the deficit in N uptake rate of the NO3 - deprived split root in the short term. Over a longer period (>1 wk), root growth of the part of the root system locally supplied with NO3 - was stimulated. An increase in root growth was mainly responsable for the greater uptake of nitrate in Lolium multiflorum so that it was able to fully compensate the deficit in N uptake rate of the NO3 - deprived split root.  相似文献   

2.
In bread wheat (Triticum aestivum L.), the simultaneous improvement of both yield and grain protein is difficult because of the strong negative relationship between these two traits. However, some genotypes deviate positively from this relationship and this has been linked to their ability to take up nitrogen (N) during the post-flowering period, regardless of their N status at flowering. The physiological and genetic determinants of post-flowering N uptake relating to N satiety are poorly understood. This study uses semi-hydroponic culture of cv. Récital under controlled conditions to explore these controls. The first objective was to record the effects of contrasting N status at flowering on post-flowering nitrate (NO3 -) uptake under non-limiting NO3 - conditions, while following the expression of key genes involved in NO3 - uptake and assimilation. We found that post-flowering NO3 - uptake was strongly influenced by plant N status at flowering during the first 300–400 degree-days after flowering, overlapping with a probable regulation of nitrate uptake exerted by N demand for growth. The uptake of NO3 - correlated well with the expression of the gene TaNRT2.1, coding for a root NO3 - transporter, which seems to play a major role in post-flowering NO3 - uptake. These results provide a useful knowledge base for future investigation of genetic variability in post-flowering N uptake and may lead to concomitant gains in both grain yield and grain protein in wheat.  相似文献   

3.
Lolium perenne L. cv. 23 (perennial ryegrass) plants were grown in flowing solution culture and acclimatized over 49 d to low root temperature (5°C) prior to treatment at root temperatures of 3, 5, 7 and 9°C for 41 d with common air temperature of 20/15°C day/night and solution pH 5·0. The effects of root temperature on growth, uptake and assimilation of N were compared with N supplied as either NH4 or NO3 at 10 mmol m?3. At any given temperature, the relative growth rate (RGR) of roots exceeded that of shoots, thus the root fraction (Rf) increased with time. These effects were found in plants grown with the two N sources. Plants grown at 3 and 5°C had very high dry matter contents as reflected by the fresh weight: freeze-dried weight ratio. This ratio increased sharply, especially in roots at 7 and 9°C. Expressed on a fresh weight basis, there was no major effect of root temperature on the [N] of plants receiving NHJ but at any given temperature, the [N] in plants grown with NHJ was significantly greater than in those grown with NO3. The specific absorption rate (SAR) of NH+4 was greater at all temperatures than SAR-NO3. In plants grown with NH+, 3–5% of the total N was recovered as NH+4, whereas in those grown with NO?3 the unassimilated NO?3 rose sharply between 7 and 9°C to become 14 and 28% of the total N in shoots and roots, respectively. The greater assimilation of NH+4 lead to concentrations of insoluble reduced N (= protein) which were 125 and 20% greater, in roots and shoots, respectively, than in NO?3-grown plants. Plants grown with NH+4 had very much greater glutamine and asparagine concentrations in both roots and shoots, although other amino acids were more similar in Concentration to those in NO?3 grown plants. It is concluded that slow growth at low root temperature is not caused by restriction of the absorption or assimilation of either NH+4 or NO?3. The additional residual N (protein) in NH+4 grown plants may serve as a labile store of N which could support growth when external N supply becomes deficient.  相似文献   

4.
Atmospheric CO2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO3?) or ammonium (NH4+), using membrane‐localized transport proteins in roots, which are key targets for improving N use. Although interactive effects of elevated CO2, chronic warming and N form on N relations are expected, these have not been studied. In this study, tomato (Solanum lycopersicum) plants were grown at two levels of CO2 (400 or 700 ppm) and two temperature regimes (30 or 37°C), with NO3? or NH4+ as the N source. Elevated CO2 plus chronic warming severely inhibited plant growth, regardless of N form, while individually they had smaller effects on growth. Although %N in roots was similar among all treatments, elevated CO2 plus warming decreased (1) N‐uptake rate by roots, (2) total protein concentration in roots, indicating an inhibition of N assimilation and (3) shoot %N, indicating a potential inhibition of N translocation from roots to shoots. Under elevated CO2 plus warming, reduced NO3?‐uptake rate per g root was correlated with a decrease in the concentration of NO3?‐uptake proteins per g root, reduced NH4+ uptake was correlated with decreased activity of NH4+‐uptake proteins and reduced N assimilation was correlated with decreased concentration of N‐assimilatory proteins. These results indicate that elevated CO2 and chronic warming can act synergistically to decrease plant N uptake and assimilation; hence, future global warming may decrease both plant growth and food quality (%N).  相似文献   

5.
The assimilation of N‐NO3? requires more energy than that of N‐NH4+. This becomes relevant when energy is limiting and may impinge differently on cell energy budget depending on depth, time of the day and season. We hypothesize that N‐limited and energy‐limited cells of the oceanic cyanobacterium Synechococcus sp. differ in their response to the N source with respect to growth, elemental stoichiometry and carbon allocation. Under N limitation, cells retained almost absolute homeostasis of elemental and organic composition, and the use of NH4+ did not stimulate growth. When energy was limiting, however, Synechococcus grew faster in NH4+ than in NO3? and had higher C (20%), N (38%) and S (30%) cell quotas. Furthermore, more C was allocated to protein, whereas the carbohydrate and lipid pool size did not change appreciably. Energy limitation also led to a higher photosynthetic rate relative to N limitation. We interpret these results as an indication that, under energy limitation, the use of the least expensive N source allowed a spillover of the energy saved from N assimilation to the assimilation of other nutrients. The change in elemental stoichiometry influenced C allocation, inducing an increase in cell protein, which resulted in a stimulation of photosynthesis and growth.  相似文献   

6.
Nodulated and unnodulated soybeans (Glycine max [L.] Merr.) were grown in N-free or N-containing nutrient solutions, respectively. Starting at the initial flowering stage, and throughout reproductive growth, the NO3- absorption capacity of roots of intact plants from both treatments was determined in short-term uptake experiments. Acetylene reduction activity was determined for nodulated plants. Nitrate absorption rate, expressed on a root dry weight basis, was greatest at early flowering for both nodulated and unnodulated plants. At 33 days after germination, the NO3- absorption rate of unnodulated plants was twice as great as that of nodulated plants. During the remainder of the sampling period, NO3- absorption rates of both nodulated and unnodulated plants decreased progressively and similarly. Maximum nodule specific activity occurred 30 days after germination, or initial flowering. However, maximum total C2H2 reduction activity, oner plant basis, was observed during the early stages of pod-filling. Compared to unnodulated plants dependent on NO3- assimilation, nodulated plants were smaller, had less N in vegetative tissues, and produced less seed per plant. We suggest that the higher NO3- absorption rate of unnodulated soybean roots, particularly during early reproductive growth, may have reflected a more favorable supply of photosynthate translocated to the roots from larger, more vigorous, non-N-stressed shoots.  相似文献   

7.
Root respiration associated with nitrate assimilation by cowpea   总被引:2,自引:1,他引:1  
Nitrate uptake by roots of cowpea (Vigna unguiculata) was measured using 15NO3, and the energy cost to the root was estimated by respirometry. Roots of 8-day-old cowpea seedlings respired 0.6 to 0.8 milligram CO2 per plant per hour for growth and maintenance. Adding 10 millimolar NO3 to the root medium increased respiration by 20 to 30% during the following 6 hours. This increase was not observed if the shoots were in the dark. Removal of NO3 from the root medium slowed the increase of root respiration. The ratios of additional respiration to the total nitrogen uptake and reduced nitrogen content in roots were 0.4 gram C per gram N and 2.3 grams C per gram N, respectively. The latter value is close to theoretical estimates of nitrate assimilation, and is similar to estimates of 1 to 4 grams C per gram N for the respiratory cost of symbiotic N2 fixation.  相似文献   

8.
Regulation of nitrogen uptake on the whole plant level   总被引:13,自引:0,他引:13  
M. K. Schenk 《Plant and Soil》1996,181(1):131-137
The largest part of nitrogen requirements of crops is mostly covered by nitrate. The uptake of this ion is thermodynamically uphill and thus dependent on metabolism. This article considers regulation of N uptake in higher plants putting emphasis on NO3 - and the whole plant level.In field conditions the transport rate depends on the concentration at the root surface in Michaelis-Menten-Kinetics. Maximum net influx of NO3 - (Imax) was often reported at concentrations of 100 M NO3 - and even lower. There are indications that for unrestricted growth the NO3 - concentration at root surface has to be in the order of magnitude allowing Imax if plants are not able to compensate for lower NO3 - concentrations by increasing root surface per unit of shoot.Imax is not a constant but depends for a given variety on N status of plants, the availability of NO3 - and plant age. The decrease of Imax with increasing plant age is closely related to relative growth rate as long as the relationship between N demand and new growth is linear and the root:shoot ratio keeps constant. It seems that Imax is a meaningful physiological characteristic of NO3 - uptake reflecting absolute N demand. There is evidence that shoot demand is linked to NO3 - uptake of the root through an amino acid transport pool cycling in the plant via phloem and xylem.The N demand of a crop depends on increase of dry mass and might not be linear if the critical level of nitrogen in plant dry matter changes during crop development or if retranslocation of nitrogen from older leaves to meristematic tissue occurs. Radiation and temperature drive plant growth and thus N demand of crops. These relationships can be described by mathematical models.  相似文献   

9.
Kirk  G.J.D. 《Plant and Soil》2001,232(1-2):129-134
The ways in which root–soil interactions can control nutrient acquisition by plants is illustrated by reference to the N nutrition of rice. Model calculations and experiments are used to assess how uptake is affected by root properties and N transport through the soil. Measurements of the kinetics of N absorption and assimilation and their regulation, and of interactions between NH4 + and NO3 nutrition, are described. It is shown that uptake of N from the soil–-as opposed to N in ricefield floodwater which can be absorbed very rapidly but is otherwise lost by gaseous emission–-will often be limited by root uptake properties. Rice roots are particularly efficient in absorbing and assimilating NO3 , and NH4 + absorption and assimilation are stimulated by NO3 . The uptake of NO3 formed in the rice rhizosphere by root-released O2 may be more important than previously thought, with beneficial consequences for rice growth. Other root-induced changes in the rice rhizosphere and their consequences are discussed.  相似文献   

10.
The uptake of nitrate, nitrite and ammonium by Codium fragile subsp. tomentosoides (van Goor) Silva was measured at different combinations of temperature (6–30 C) and irradiance (0–140 μEin.m-2. s-1). Uptake of all three forms of N was greater at 12–24 C than at 6 and 30 C. Although uptake was stimulated by light, saturation occurred at relatively low irradiance (7–28 μEin m-2 s-1, depending on the N source and temperature). The Michaelis-Menten uptake constants (Vmax K)varied with temperature. Vmax was greatest at intermediate temperatures and K was lowest at lower temperatures. The Vmaxfor NH4+ was higher and the K, for NH4+was lower than those for NO3-- and NO2--. Codium was capable of simultaneously taking up all three forms of inorganic N although the presence of NH4+ reduced the uptake of both NO3-- and NO2--. The results of this study indicate that part of the ecological success of Codium in a N-limited environment may be due to its N uptake capabilities.  相似文献   

11.
During their life cycle, plants must be able to adapt to wide variations in the supply of soil nitrogen (N). Changes in N availability, and in the relative concentrations of NO3 and NH4 +, are known to have profound regulatory effects on the N uptake systems in the root, on C and N metabolism throughout the plant, and on root and shoot morphology. Optimising the plant’s responses to fluctuations in the N supply requires co-ordination of the pathways of C and N assimilation, as well as establishment of the appropriate allocation of resources between root and shoot growth. Achieving this integration of responses at the whole plant level implies long-distance signaling mechanisms that can communicate information about the current availability of N from root-to-shoot, and information about the C/N status of the shoot in the reverse direction. In this review we will discuss recent advances which have contributed to our understanding of these long-range signaling pathways.  相似文献   

12.
为了解丛枝菌根真菌(AMF)和不同形态氮对杉木(Cunninghamia lanceolata)生长和养分吸收的影响,以1 a生杉木幼苗接种摩西球囊霉(Glomus mosseae)和添加不同形态氮(NH4+-N和NO3-N),对其养分元素和生长状况的变化进行研究。结果表明,AMF显著提高了杉木的苗高和生物量,促进了杉木对N、P、K、Ca、Mg、Fe和Na的吸收,AMF对微量元素Fe、Na的促进作用总体上要强于大量元素K、Ca。与NO3-N相比,AMF显著提高了NH4+-N处理杉木的生物量、总C和N、Ca、Mg、Mn含量,而且这种显著性在叶中普遍高于根和茎。接种AMF可以促进杉木幼苗的生长和对养分元素的吸收,且添加NH4+-N处理的促进作用要强于NO3-N。  相似文献   

13.
《Plant and Soil》2000,220(1-2):175-187
Several studies have previously shown that shoot removal of forage species, either by cutting or herbivore grazing, results in a large decline in N uptake (60%) and/or N2 fixation (80%). The source of N used for initial shoot growth following defoliation relies mainly on mobilisation of N reserves from tissues remaining after defoliation. To date, most studies investigating N-mobilisation have been conducted, with isolated plants grown in controlled conditions. The objectives of this study were for Lolium perenne L., grown in a dense canopy in field conditions, to determine: 1) the contribution of N-mobilisation, NH4 + uptake and NO3 - uptake to growing shoots after defoliation, and 2) the contribution of the high (HATS) and low (LATS) affinity transport systems to the total plant uptake of NH4 + and NO3 -. During the first seven days following defoliation, decreases in biomass and N-content of roots (34% and 47%, respectively) and to a lesser extent stubble (18% and 43%, respectively) were observed, concomitant with mobilisation of N to shoots. The proportion and origin of N used by shoots (derived from reserves or uptake) was similar to data reported for isolated plants. Both HATS and LATS contributed to the total root uptake of NH4 + and NO3 -. The Vmax of both the NH4 + and NO3 - HATS increased as a function of time after defoliation, and both HATS systems were saturated by substrate concentrations in the soil at all times. The capacity of the LATS was reduced as soil NO3 - and NH4 + concentrations decreased following defoliation. Data from 15N uptake by field-grown plants, and uptake rates of NH4 + and NO3 - estimated by excised root bioassays, were significantly correlated, though uptake was over-estimated by the later method. The results are discussed in terms of putative mechanisms for regulating N uptake following severe defoliation. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

14.
The dynamics of ammonium (NH4 +) and nitrate (NO3 -) concentrations in the soil solution is an important determinant of the species composition of natural vegetation. A mathematical model of uptake, assimilation and translocation of NH4 + and NO3 - is presented to assess the performance of species with respect to NO3 -/NH4 + feeding characterised by physiologically defined parameters. Nitrate efflux is explicitly considered. The capacities of NO3 -, [U NM], and NH4 + influx, [U AM], and NO3 - reduction, [A NM], appear sufficient to characterise whole-plant N metabolism including NO3 - translocation. The parameter space made up by these parameters is represented by 276 parameter combinations (`species'). Simulated total net N uptake rate and C costs for uptake and assimilation per mole total net N taken up are used to decide on how a species profits or suffers from NO3 -+NH4 + mixtures relative to pure N forms with similar total N concentration for external concentrations up to 1.6 mM. Five response categories were identified and contrasted with categories defined by Bogner (1968) on the basis of experimental results on forest plants. The largest category comprises species that respond positively to NO3 - and positively or indifferently to NH4 +. These species have intermediate to high [U NM] and [A NM] and variable [U AM] and correspond to woodland edge species and forest plants on rich soil including typical `nitrophilic' species. This category fades into a group of species that respond positively to NO3 - and negatively to NH4 +. These species have high [U NM] and low [U AM] and [A NM]; several species from oak-hornbeam woodland (Carpinion) belong to this group. Many parameter combinations were found that responded positively to NH4 + and indifferently to NO3 -: low to medium [U NM], medium to high [U AM] and variable [A NM]. This category includes all heathland species. No species were found which responded negatively to NO3 -. The physiological background of differences between the categories is explained with respect to the equilibrium NO3 - concentration in roots, influx, efflux, translocation and assimilation of NO3 - and uptake and assimilation of NH4 +. The relationship between NO3 - accumulation capacity and morphology is discussed. Some slow-growing species with high [U NM] and low [A NM] use NO3 - mainly as an osmotic solute. Respiratory costs in roots of inherently slow-growing species are discussed with respect to patterns in NH4 + and NO3 - availabilities of their habitat. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

15.
Studies that quantify plant δ15N often assume that fractionation during nitrogen uptake and intra-plant variation in δ15N are minimal. We tested both assumptions by growing tomato (Lycopersicon esculetum Mill. cv. T-5) at NH4+ or NO?3 concentrations typical of those found in the soil. Fractionation did not occur with uptake; whole-plant δ15N was not significantly different from source δ15 N for plants grown on either nitrogen form. No intra-plant variation in δ15N was observed for plants grown with NH+4. In contrast. δ15N of leaves was as much as 5.8% greater than that of roots for plants grown with NO?3. The contrasting patterns of intra-plant variation are probably caused by different assimilation patterns. NH+4 is assimilated immediately in the root, so organic nitrogen in the shoot and root is the product of a single assimilation event. NO?3 assimilation can occur in shoots and roots. Fractionation during assimilation caused the δ15N of NO?3 to become enriched relative to organic nitrogen; the δ15N of NO?3 was 11.1 and 12.9% greater than the δ15N of organic nitrogen in leaves and roots, respectively. Leaf δ15N may therefore be greater than that of roots because the NO?3 available for assimilation in leaves originates from a NO?3 pool that was previously exposed to nitrate assimilation in the root.  相似文献   

16.
Bowman DC  Paul JL 《Plant physiology》1988,88(4):1303-1309
Assimilation of NO3 and NH4+ by perennial ryegrass (Lolium perenne L.) turf, previously deprived of N for 7 days, was examined. Nitrogen uptake rate was increased up to four- to five-fold for both forms of N by N-deprivation as compared to N-sufficient controls, with the deficiency-enhanced N absorption persisting through a 48 hour uptake period. Nitrate, but not NH4+, accumulated in the roots and to a lesser degree in shoots. By 48 hours, 53% of the absorbed NO3 had been reduced, whereas 97% of the NH4+ had been assimilated. During the early stages (0 to 8 hours) of NO3 uptake by N-deficient turf, reduction occurred primarily in the roots. Between 8 and 16 hours, however, the site of reduction shifted to the shoots. Nitrogen form did not affect partitioning of the absorbed N between roots (40%) and shoots (60%) but did affect growth. Compared to NO3, NH4+ uptake inhibited root, but not shoot, growth. Total soluble carbohydrates decreased in both roots and shoots during the uptake period, principally the result of fructan metabolism. Ammonium uptake resulted in greater total depletion of soluble carbohydrates in the root compared to NO3 uptake. The data indicate that N assimilation by ryegrass turf utilizes stored sugars but is also dependent on current photosynthate.  相似文献   

17.
Solution culture studies have shown that plant uptake of NH4 + and NO3 - can be improved by increasing the concentration of Ca2+ in the root environment: the same may be true for grass grown in soil culture. An experiment was set up to see whether gypsum (CaSO4 2H2O) increased the rate at which perennial ryegrass absorbed 15NH4 + and 15NO3 - from soil.The results demonstrated that gypsum increases the rates of uptake of both NH4 + and NO3 - by perennial ryegrass. However because there was little potential for mineral-N loss from the experimental system, either by gaseous emission or by N immobilization, long term improvements in fertilizer efficiency were not observed. Nitrogen cycling from shoots to roots commenced once net uptake of N into plants had ceased. Labelled N transferred thus to roots underwent isotopic exchange with unlabelled soil N. It was suggested that this exchange of N might constitute an energy drain from the plant, if plant organic N was exchanged for soil inorganic N. The fact that the exchange occurred at all cast doubt on the suitability of the 15N-isotope dilution technique for assessing fertilizer efficiency in medium to long term experiments. There was evidence that the extra NO3 --N taken up by plants on the all-nitrate treatments as a result of gypsum application, was reduced in root tissue rather than in shoots, but to the detriment of subsequent root growth and N uptake.  相似文献   

18.
The present study with young poplar trees aimed at characterizing the effect of O2 shortage in the soil on net uptake of NO3 - and NH4 + and the spatial distribution of the N taken up. Moreover, we assessed biomass increment as well as N status of the trees affected by O2 deficiency. For this purpose, an experiment was conducted in which hydroponically grown young poplar trees were exposed to hypoxic and normoxic (control) conditions for 14 days. 15N-labelled NO3 - and NH4 + were used to elucidate N uptake and distribution of currently absorbed N and N allocation rates in the plants. Whereas shoot biomass was not affected by soil O2 deficiency, it significantly reduced root biomass and, consequently, the root-to-shoot ratio. Uptake of NO3 - but not of NH4 + by the roots of the trees was severely impaired by hypoxia. As a consequence of reduced N uptake, the N content of all poplar tissues was significantly diminished. Under normoxic control conditions, the spatial distribution of currently absorbed N and N allocation rates differed depending on the N source. Whereas NO3 - derived N was mainly transported to the younger parts of the shoot, particularly to the developing and young mature leaves, N derived from NH4 + was preferentially allocated to older parts of the shoot, mainly to wood and bark. Soil O2 deficiency enhanced this differential allocation pattern. From these results we assume that NO3 - was assimilated in developing tissues and preferentially used to maintain growth and ensure plant survival under hypoxia, whereas NH4 + based N was used for biosynthesis of storage proteins in bark and wood of the trees. Still, further studies are needed to understand the mechanistic basis as well as the eco-physiological advantages of such differential allocation patterns.  相似文献   

19.
The nitrogen isotope composition (δ15N) of plants has potential to provide time‐integrated information on nitrogen uptake, assimilation and allocation. Here, we take advantage of existing T‐DNA and γ‐ray mutant lines of Arabidopsis thaliana to modify whole‐plant and organ‐level nitrogen isotope composition. Nitrate reductase 2 (nia2), nitrate reductase 1 (nia1) and nitrate transporter (nrt2) mutant lines and the Col‐0 wild type were grown hydroponically under steady‐state NO3 conditions at either 100 or 1000 μM NO3 for 35 days. There were no significant effects on whole‐plant discrimination and growth in the assimilatory mutants (nia2 and nia1). Pronounced root vs leaf differences in δ15N, however, indicated that nia2 had an increased proportion of nitrogen assimilation of NO3 in leaves while nia1 had an increased proportion of assimilation in roots. These observations are consistent with reported ratios of nia1 and nia2 gene expression levels in leaves and roots. Greater whole‐plant discrimination in nrt2 indicated an increase in efflux of unassimilated NO3 back to the rooting medium. This phenotype was associated with an overall reduction in NO3 uptake, assimilation and decreased partitioning of NO3 assimilation to the leaves, presumably because of decreased symplastic intercellular movement of NO3 in the root. Although the results were more varied than expected, they are interpretable within the context of expected mechanisms of whole‐plant and organ‐level nitrogen isotope discrimination that indicate variation in nitrogen fluxes, assimilation and allocation between lines.  相似文献   

20.
汪庆兵  张建锋  陈光才  孙慧  吴灏  张颖  杨泉泉  王丽 《生态学报》2015,35(16):5364-5373
采用水培法,研究了旱柳苗在外源添加不同氮水平(贫氮、中氮、富氮、过氮)的铵态氮(NH+4-N)和硝态氮(NO-3-N)的生长、氮吸收、分配和生理响应。结果表明:一定范围氮浓度的增加能够促进旱柳苗的生长,但过量氮会抑制其生长,且NH+4-N的抑制作用大于NO-3-N;两种氮处理下,旱柳表现出对NH+4-N的吸收偏好,在同一氮水平时,旱柳各部位氮原子百分含量Atom%15N(AT%)、15N吸收量和来自氮源的N%(Ndff%)均为NH+4-N处理大于NO-3-N处理,且随着氮浓度的增加,差异增大,且在旱柳各部位的分布为根﹥茎﹥叶;2种氮素过量和不足均会对旱柳根和叶生理指标产生不同的影响,其中在过氮水平时,NH+4-N和NO-3-N处理下根系活力比对照减少了50.61%和增加了19.53%;在过氮水平时,NH+4-N处理柳树苗根总长、根表面积、根平均直径、根体积和侧根数分别对照下降了30.92%、29.48%、19.44%、27.01%和36.41%,NO-3-N处理柳树苗相应的根系形态指标分别对对照下降了1.66%、5.65%、1.49%、5.06%和25.72%。可见,高浓度NH+4-N对旱柳苗的胁迫影响大于NO-3-N,在应用于水体氮污染修复时可通过改变水体无机氮的比例,削弱其对旱柳的影响,从而提高旱柳对水体氮污染的修复效果。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号