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1.
A growth experiment on agar medium and a hydroponics experiment were carried out to study the nitrogen (N) metabolism of a low-N tolerant mutant (lnt1) of Arabidopsis thaliana under different N levels as compared with the wildtype (WT) Arabidopsis. On the agar medium, no apparent growth differences were observed between the lnt1 and WT plants under a normal N level of 9 mmol L-1 NO3-. However, under a low N level of 0. 18 mmol L-1 NO3-, the growth of the WT plants was greatly retarded, while the lnt1 plants were not affected by low-N stress and showed similar growth with those grown under a normal N level. In the hydroponics experiment, the lnt1 mutant had higher activities of glutamine synthetase (GS) and NADH-dependent glutamate synthase (NADH-GOGAT) in both leaves and roots under N-deficient conditions. Moreover, they accumulated less ammonium (NH4+) but more free amino acids in leaves compared with the WT plants. These observations suggest that better N assimilation might contribute to the low-N tolerant phenotype of the lnt1 mutant. 相似文献
2.
Plants show different growth responses to N sources supplied with either NH4+ or NO3-. The uptake of different N sources also affects the rhizosphere pH and therefore the bioavailability of soil phosphorus, particularly in alkaline soils. The plant growth, P uptake, and P availability in the rhizosphere of oat (Avena nuda L.) grown in hydroponics and in soil culture were investigated under supply with sole NH4+-N, sole NO3--N, or a combination. Sole NO3--fed oat plants accumulated more biomass than sole NH4+-fed ones. The highest biomass accumulation was observed when N was suppliedw ith both NH4+-N and NO3--N. Growth of the plant root increased with the proportion of NO3- in the cultural medium. Better root growth and higher root/shoot ratio were consistently observed in NO3--fed plants. However, root vigor was the highest when N was supplied with NO3-+NH4+. NH4+ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO4 added as P source. No P deficiency was observed, and plant P concentrations were generally above 2 g kg-1. P uptake was increased when N was supplied partly or solely as NO3--N, similarly as biomass accumulation. The results suggested that oat was an NO3--preferring plant, and NO3--N was essential for plant growth and the maintenance of root absorption capacity. N supply with NH4+-N did not improve P nutrition, which was most likely due to the absence of P deficiency. 相似文献
3.
The effect of background anion on cation exchange reactions, such as Na-Ca and Na-Cu exchange reactions, on montmorillonites has been studied, but the results are not always clear and discrepancies exist in the literature. In this study, the exchange of zinc (Zn2+) for sodium (Na+) on Wyoming montmorillonite was investigated at 298°K using Cl-, ClO4-, NO3-, OAc-, and SO42- solution media at a constant total metal charge concentration of 0.0200 molc L-1. Results indicated that the clay CEC values were essential similar for Cl-, ClO4-, NO3- and SO42- solution media with an average CEC of 0.856 ± 0.008 molc kg-1; in an OAc+ solution the clay CEC was much higher than that in other anion media. The specific adsorption of Zn (SAZn), as defined by the extraction of Zn using 0.05mol L-1 Na2-EDTA, was different in the various background solutions. The highest value for SAZn was 0.359 ± 0.0350molc kg-1, which occurred in OAc-solution. There was essentially no difference in the total apparent adsorbed metals (the sum of adsorbed equivalents of Na and Zn per kilogram of clay, Q) among the various background solutions. The average Q for all anion media was 0.807 ± 0.011 molc kg-1 and was independent of exchanger composition. Experimental results indicated that there were no significant monovalent cation complexes such as ZnCl+ or ZnNO3+ that were adsorbed by montmorillonite. The Na-Zn exchange isotherms indicated that there was an adsorption preference for Zn over Na on Wyoming montmorillonite. 相似文献
4.
黄土高原半干旱区不同土地利用下的土壤有机碳、碳组分和土壤营养 总被引：5，自引：0，他引：5
Cropland (CP), native grassland (NG) and two shrub land treatments which were converted from cropland in 1985:seabuckthorn (Hippophae rhamnoides L. ) (ST), and branchytamarisk (Tamarix ramosissima) (BT) were investigated to evaluate effects of land use conversion on soil organic carbon (SOC) and soil nutrients in the semi-arid region of the Loess Plateau of China. Total organic carbon (TOC), light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), total N (TN), nitrate nitrogen (NO3--N) and nitrite nitrogen (NO2--N), ammonium nitrogen (NH4+-N), total P, and available P (AP) were measured. The results showed that SOC in NG, ST and BT were 12.7%, 27.7% and 34.8% higher than that of the cropland, respectively. LFOC, light fraction (LF) dry matter, ratio of TOC to TN (C/N) and the ratio of TOC to AP (C/P) were higher in the shrub land or native grassland than in the cropland. Cropland had the highest TN, the sum of NO3--N and NO2--N, TP and AP due to the use of chemical fertilizers. TOC significantly correlated with LFOC, HFOC and C/N. LFOC significantly correlated with dry matter of the LF and C/N. TN, the sum of NO3--N and NO2--N and AP were significantly negatively correlated with TOC and LFOC. Therefore, land use conversion from cropland to shrub land, or maybe grassland, contributed to SOC sequestration and improved soil nutrients stabilization. 相似文献
5.
上海郊区园艺土壤氮素的生物形成动态变化 总被引：3，自引：0，他引：3
Dissolved organic nitrogen (DON) represents a significant pool of soluble nitrogen (N) in soil ecosystems. Soil samples under three different horticultural management practices were collected from the Xiaxiyang Organic Vegetable and Fruit Farm, Shanghai, China, to investigate the dynamics of N speciation during 2 months of aerobic incubation, to compare the effects of different soils on the mineralization of 14C-labeled amino acids and peptides, and to determine which of the pathways in the decomposition and subsequent ammonification and nitrification of organic N represented a significant blockage in soil N supply. The dynamics of N speciation was found to be significantly affected by mineralization and immobilization. DON, total free amino acids, and NH4+-N were maintained at very low levels and did not accumulate, whereas NO3--N gradually accumulated in these soils. The conversion of insoluble organic N to low-molecular-weight (LMW) DON represented a main constraint to N supply, while conversions of LMW DON to NH4+-N and NH4+-N to NO3--N did not. Free amino acids and peptides were rapidly mineralized in the soils by the microbial community and consequently did not accumulate in soil. Turnover rates of the additional amino acids and peptides were soil-dependent and generally followed the order of organic soil > transitional soil > conventional soil. The turnover of high-molecular-weight DON was very slow and represented the major DON loss. Further studies are needed to investigate the pathways and bottlenecks of organic N degradation. 相似文献
6.
硝态氮促进水稻生长和氮素吸收的生理机制 总被引：2，自引：0，他引：2
Rice is being increasingly cultivated in intermittently irrigated regious and also in aerobic soil in which Nitrate (NO3-) plays important role in nutrition of plant. However, there is no information regarding the influence of nitrate on the overall growth and uptake of nitrogen (N) in rice plant. Solution culture experiments were carried out to study the effects of NO3- on the plant growth, uptake of N, and uptake kinetics of NH4+ in four typical rice (Oryza sativa L.) cultivars (conveutioual indica, conventional japonica, hybrid indica, and hybrid japonica), and on plasma membrane potential in roots of two conventional rice cultivars (indica and japonica) at the seedling stage. The results obtained indicated that a ratio of 50/50 NH4+-N/NO3--N increased the average biomass of rice shoots and roots by 20% when compared with that of 100/0 NH4+-N/NO3--N. In case of the 50/50 ratio, as compared with the 100/0 ratio, total N accumulated in shoots and roots of rice increased on an average by 42% and 57%, respectively. Conventional indica responds to NO3- more than any other cultivars that were tested. The NO3- supply increased the maximum uptake rate (Vmax) of NH4+ by rice but did not show any effect on the apparent Michaelis-Menten constant (Km) value, with the average value of Vmax for NH4+ among the four cultivars being increased by 31.5% in comparison with those in the absence of NO3-. This suggested that NO3- significantly increased the numbers of the ammonium transporters. However, the lack of effect on the Km value also suggested that the presence of NO3- had no effect on the affinity of the transporters for NH4+. The plasma membrane potential in the roots of conventional indica and japonica were greatly increased by the addition of NO3-, suggesting that NO3- could improve the uptake of N by roots of the rice plant. In conclusion, the mechanisms by which NO3- enhances the growth and N uptake of rice plant was found by the increased value of Vmax of NH4+ and increased plasma membrane potential. Thus promotion of nitrification in paddy soil is of great significance for improving the production of rice. 相似文献
7.
The effiects of NaCl salinity and NO3- on growth, root morphology, and nitrogen uptake of a halophyte Suaeda physophora were evaluated in a factorial experiment with four concentrations of NaCl (1, 150, 300, and 450 mmol L-1) and three NO3- levels (0.05, 5, and 10 mmol L-1) in solution culture for 30 d. Addition of NO3- at 10 mmol L-1 significantly improved the shoot (P < 0.001) and root (P < 0.001) growth and the promotive effect of NO3- was more pronounced on root dry weight despite the high NaCl concentration in the culture solution, leading to a significant increase in the root:shoot ratio (P < 0.01). Lateral root length, but not primary root length, considerably increased with increasing NaCl salinity and NO3- levels (P < 0.001), implying that Na+ and NO3- in the culture solution simultaneously stimulated lateral root growth. Concentrations of Na+ in plant tissues were also significantly increased by higher NaCl treatments (P < 0.001). At 10 mmol L-1 NO3- , the concentrations of NO3- and total nitrogen and nitrate reductase activities in the roots were remarkably reduced by increasing salinity (P < 0.001), but were unaffected in the shoots. The results indicated that the fine lateral root development and effective nitrogen uptake of the shoots might contribute to high salt tolerance of S. physophora under adequate NO3- supply. 相似文献
8.
Dynamics of fixed NH4+ in NH4+-treated soils incubated with glucose at 37±2 ℃ during the course of incubation and factors affecting it were studied. Results showed that content of fixed NH4+ in soil reached a minimum on day 7 after incubation and then increased gradually regardless of the amount of glucose added and the kind of soil tested. However, the amount of fixed NH4+ released from the soil at the given time varied with both the amount of glucose added and the kind of soil examined. In cases glucose was added at a rate of 10.0g C/kg soil, the amount of fixed NH4+ retained in soil after 7 days of incubation was almost identical to that found by Neubauer test. Addition of K+ depressed the release of fixed NH4+ significantly. Based on the results obtained a method for determining the content of available fixed NH4+ in soils was proposed and the amount of N as available fixed NH4+ in two soils measured by this method on an area profile-depth basis was presented. 相似文献
9.
In a series of laboratory incubations using soils of two contrasting sites from a temperate marsh on the Qinghai-Tibet Plateau, potential methane (CH4) oxidation rates were measured to study the effects of inorganic N inputs on CH4 oxidation. For a drained site, subsurface peat (5-15 cm) at an initial 20 μL CH4 L-1 showed a significantly different (P < 0.05) CH4 oxidation rate compared to other soil depths, with a maximal rate of 20.9 ng CH4 gDW (dry weight)-1 h-1; the underlying mineral soil layers (15-30 and 30-50 cm) also had a strong CH4 oxidation capacity at about an initial 2000 μL CH4 L-1. With a waterlogged site, the CH4 oxidation rate in an aerobic incubation was significantly greater (P < 0.05) in the surface soil layer (0-5 cm) compared to the 15-30 and 30-50 cm depths. There was generally no or a very weak effect from addition of NO3- on CH4 oxidation. In marked contrast, NH4+ salts, such as (NH4)2SO4, NH4Cl and NH4NO3, exhibited strong inhibitions, which varied as a function of the added salts and the initial CH4 level. Increasing NH4+ usually resulted in greater inhibition and increasing initial CH4 concentrations resulted in less. NH4+ inhibition on CH4 oxidation in natural high-altitude, low-latitude wetlands could be as important as has been reported for agricultural and forest soils. The NH4+ effects on the CH4 oxidation rate need to be further investigated in a wide range of natural wetland soil types. 相似文献
10.
淹水稻田氮的损失 总被引：29，自引：3，他引：29
A field microplot experiment was conducted during the tillering stage of paddy rice to investigate nitrogen(N) Iosses from flooded rice fields following fertilizer application. After application of ammonium bicarbonate, most of nitrogen in the flood water was present as NH4-N and its concentration varied widely with time. Concentrations of both NO3-N and NO2-N in the floodwater were low due to the weakened nitrification. Under flooded anaerobic reducing conditions, soil solution concentrations of NO3-N and NH4-N were nothigh, ranging from 0.6 mg L-1 to 4.8 mg L-1, and decreased with soil depth. However, the ground water wasstill contaminated with NO3-N and NH4-N. Rainfall simulation tests showed that the N losses via runoff inrice fields were closely related to the time intervals between fertilizer applications and rainfall events. Whena large rain fell for a short period after fertilizer application, the N losses via runoff could be large, which could have a considerable effect on surface water quality. Both irrigation and N fertilizer application must be controlled and managed with great care to minimize N losses via runoff from agricultural land. 相似文献
11.
Plants show different growth responses to N sources supplied with either NH4+ or NO3-.The uptake of different N sources also affects the rhizosphere pH and therefore the bioavailability of soil phosphorus,particularly in alkaline soils.The plant growth,P uptake,and P availability in the rhizosphere of oat (Arena nuda L.) grown in hydroponics and in soil culture were investigated under supply with sole NH4+-N,sole NO3--N,or a combination.Sole NO3-fed oat plants accumulated more biomass than sole NH4+-fed ones.The highest biomass accumulation was observed when N was supplied with both NH4+-N and NO3--N.Growth of the plant root increased with the proportion of NO3-in the cultural medium.Better root growth and higher root/shoot ratio were consistently observed in NO3--fed plants.However,root vigor was the highest when N was supplied with NO3-+NH4+.NH4+ supply reduced the rhizosphere pH but did not affect P uptake by plants grown in soils with CaHPO4 added as P source.No P deficiency was observed,and plant P concentrations were generally above 2 g kg-1.P uptake was increased when N was supplied partly or solely as NO3--N,similarly as biomass accumulation.The results suggested that oat was an NO3-prcferring plant,and NO3--N was essential for plant growth and the maintenance of root absorption capacity.N supply with NH4+-N did not improve P nutrition,which was most likely due to the absence of P deficiency. 相似文献
12.
Tomato (Lycopersicon esculentum L. Mill. 'Vendor') plants were grown for 21 days in flowing solution culture with N supplied as either 1.0 mM NO3- or 1.0 mM NH4+. Acidity in the solutions was automatically maintained at pH 6.0. Accumulation and distribution of dry matter and total N and net photosynthetic rate were not affected by source of N. Thus, when rhizosphere acidity was controlled at pH 6.0 during uptake, either NO3- or NH4+ can be used efficiently by tomato. Uptake of K+ and Ca2+ were not altered by N source, but uptake of Mg2+ was reduced in NH4(+)-fed plants. This indicates that uptake of Mg2+ was regulated at least partially by ionic balance within the plant. 相似文献
13.
不同水、氮条件对水稻苗生长及伤流液的影响 总被引：14，自引：2，他引：12
为探明不同水分供应和氮素形态对水稻根苗及伤流液的影响,设正常水分及50 g/L PEG模拟水分胁迫和3种不同质量比例的NH4+-N/NO3--N（9/1,5/5,1/9）氮素营养处理,测定了水稻幼苗生物量,根系形态指标,根系活力及根基伤流量。结果表明,正常水分条件下,NH4+-N促进水稻根系平均直径增大,有利于水稻地上部物质累积;NO3--N则使水稻根系总吸收面积增大,促进根系物质累积;NH4+-N/NO3--N为5/5处理的水稻活跃吸收面积最大,活跃吸收面积比亦最高。水分胁迫条件下,NH4+-N/NO3--N为5/5的处理更有利于水稻地上部分的生长,NO3--N有利于水稻鲜重和干重增加,促进根系平均直径增大,水稻的根系总吸收面积、活跃吸收面积均随NO3--N供应比例的增加呈上升趋势。正常水分条件下,水稻幼苗白天的耗水量随NH4+-N/ NO3--N比例降低呈下降趋势,水分胁迫条件降低了水稻对水分的吸收。水分胁迫显著降低各处理水稻伤流量,正常水分条件下,NH4+-N/NO3--N为5/5处理的水稻伤流量最大;水分胁迫后,9/1处理的水稻伤流量相对较多。 相似文献
14.
Zinc(Zn) is essential to plant growth and relatively mobile in soils.This study was conducted to assess the effect of common ions(Ca 2+,K +,Na +,NH + 4,Cl,NO 3,and H 2 PO 4) on sorption of Zn in surface samples of ten calcareous soils from western Iran using 10 mmol L 1 KCl,KNO 3,KH 2 PO 4,Ca(NO 3) 2,NaNO 3,and NH 4 NO 3 solutions as background electrolytes.The results indicated that both NH + 4,K +,and Ca 2+ equally decreased Zn sorption as compared to Na +.Zinc sorption was decreased by H 2 PO 4 as compared to NO 3 and Cl.The Langmuir and Freundlich equations fitted closely to the sorption data of all ions.The Langmuir maximum,bonding energy constant,and Freundlich distribution coefficient for Zn sorption differed among the various ionic background electrolytes.Langmuir sorption parameters showed that the presence of H 2 PO 4 decreased the maximum Zn adsorbed,but increased the bonding energy.Although K + and NH + 4 equally influenced maximum Zn adsorbed,they differed in their effect on the distribution coefficient of Zn in soils.Values of saturation index calculated using Visual MINTEQ indicated that at the low Zn concentration,Zn solubility was controlled by sorption reactions and at the high Zn concentration,it was mainly controlled by sorption and mineral precipitation reactions,such as precipitation of Zn 3(PO 4) 2.4H 2 O,Zn 5(OH) 6(CO 3) 2,and ZnCO 3.For most ionic background electrolytes,soil pH,CaCO 3,and cation exchange capacity(CEC) were significantly correlated with sorption parameters. 相似文献
15.
水稻耐盐性的机理 总被引：15，自引：3，他引：15
Shaheen Basmati was evolved as a salt tolerant fine rice variety by the Soil Salinity Research Institute,Pindi Bhattian, Pakistan. Water culture studies were conducted to investigate the physiological mechanism exercised by this variety in particular and rice plant in general to face the saline environment. Performance of this rice variety and the concentration and uptake of ions were studied under stress of three salinity levels(30, 60 and 90 mmolL^-1) created with NaC1. Recorded data indicated that shoot dry matter was not significantly affected by all the three levels of salinity. However, NaC1 levels of 60 and 90 mmol L^-1 affected the root dry matter significantly. Sodium concentration and uptake was enhanced significantly in root and shoot at the first level of salinity (30 mmol L^-1) but thereafter the differences were non-significant, indicating the preferential absorption of this cation. The K concentration decreased significantly in shoots at all the levels. The impact was less pronounced in roots as far as K absorption was concerned. The effect on Ca and Mg concentrations was not significant. The values of K:Na, Ca:Na and (Ca Mg):Na ratios in shoot and root were comparatively low under stress conditions, indicating that selective ion absorption may be the principal salt tolerance mechanism of variety Shaheen Basmati when grown in a saline medium. 相似文献
16.
低氮胁迫下水稻根系的发生及生长素的响应 总被引：5，自引：0，他引：5
采用水培实验,研究了5个氮(N)浓度下(0.01～5 mmol L-1)水稻的生物量、体内氮浓度、根系发育、体内生长素浓度以及生长素外流蛋白OsPIN家族基因的表达情况。结果表明,与正常供氮水平(2.5mmol L-1)相比,低氮(0.01 mmol L-1)胁迫下水稻根冠比增加28%,地上部全氮浓度降低约20%,根系全氮浓度降低约33%,种子根长度增加25%,种子根上的侧根密度降低26%,倒一叶中的生长素含量增加140%,而根茎结合处和根系的生长素浓度分别下降22%和60%;RT-PCR的结果表明,低氮(0.01 mmol L-1)胁迫下水稻根系中OsPIN1a-b、OsPIN2、OsPIN5a-b和OsPIN9基因表达显著下调;而外源生长素α-萘乙酸(NAA)和生长素极性运输抑制剂1-萘氨甲酰苯甲酸(NPA)的施加均能影响到水稻种子根长和种子根上的侧根密度。由此推论,低氮胁迫下水稻体内生长素从倒一叶到根系极性运输减少是水稻根系对低氮胁迫响应的生理机制之一。 相似文献
17.
适量施氮增强盐胁迫下高羊茅生长和抗氧化能力 总被引：2，自引：0，他引：2
为土壤盐渍地区高羊茅(Festuca arundinacea)草坪的合理施肥,该研究用NaCl浓度为0,70,140mmol/L和不同NH4NO3水平(质量浓度为0.01,0.6,1.2g/L)对盆栽高羊茅植株进行交互处理,并测定处理后其生长量和抗氧化能力。结果表明,同一水平NH4NO3相比,NaCl胁迫下高羊茅鲜质量、干质量、含水率均低于无NaCl处理;而根系脱氢酶活性、硝酸还原酶(nitratereductase,NR)活性、超氧化物歧化酶(superoxidedismutase,SOD)同工酶活性NO3-含量、质膜透性和丙二醛(malonicdialdehyde,MDA)含量均强于或高于无NaCl处理;CAT(catalase,CAT)同工酶活性及蛋白表达量发生改变。同一浓度NaCl胁迫下,随NH4NO3水平增加,其鲜质量、干质量、含水率呈上升趋势;NO3-含量、质膜透性和MDA含量呈下降趋势;SOD同工酶增强;根系脱氢酶活性、NR活性、CAT同工酶活性和蛋白表达量增强幅度明显减弱。因此,与NH4NO30.01g/L相比,NH4NO30.6g/L改善了同浓度盐胁迫下高羊茅氮素营养、抗氧化能力和蛋白质表达量,增强了其耐盐性;而NH4NO31.2g/L能一定程度上改善其氮素营养,但根系主动吸收离子能力、清除H2O2能力和蛋白质表达量增强有限,引起根际环境NH4NO3积累,严重导致土壤次生盐渍化。该研究为盐渍土壤上的高羊茅草坪合理施用NH4NO3提供参考。 相似文献
18.
Tobacco (Nicotiana tabacum L., cv. 'Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO3- or 1.0 mM NH4+ as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO3- or NH4+ uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO3- [correction of NO-] was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH4+ was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO3(-) -fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH4(+) -fed plants was increased to pH 4.0, however, specific rate of NH4+ uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH4(+) -fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH4(+) -fed plants to increased root-zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress. 相似文献