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1.
用~(15)N天然丰度法估测结瘤作物的共生固N_2量 总被引：1，自引：0，他引：1
测定了位于北京西北郊的本所农场耕地及附近几个土样的土壤总Nδ15N值,农场耕地的δ15N值为6.39±0.42‰,本所庭园土壤为5.03±0.26‰,圆明园土壤为1.66±0.49‰。农场耕地土壤总Nδ15N的垂直变化为6.09±0.77～7.71±0.67‰,水平变化为6.52±0.55～7.13±0.73‰。 无N营养液砂培大豆的测定结果表明,根瘤富含15N,δ15N值为8.32±0.16‰和10.54±0.30‰,地上部贫化15N,δ15N为—2.25±0.48～—4.16±0.75‰,说明在固N2过程中和固N2产物输送转化过程中发生了N同位素的分馏,固N2分馏因数β=1.0023～1.0042。 用15N天然丰度法估计不同大豆品种的％Ndfa表明,不同大豆品种的N素自给能力不同。固N2植物的δ15N值明显低于非固N2植物的δ15N值,一般相差3～5δ15N,说明用15N天然丰度法评价这些植物的固N2状况是可能的。然而,不固N02植物也有较低的δ15N值,即便在同一地块上,非固N2植物的δ15N值也很不相同,有待进一步研究。 相似文献
2.
田间小区试验研究了不同种植模式下苜蓿的共生固氮贡献,并利用~(15)N同位素示踪技术评估了苜蓿的％Ndfa和Ndfa,以及与之混作生长的牛尾草植株中来自苜蓿固氮产物的转移量。研究表明,豆科与禾本科牧草混作对发挥草地的优势有一定影响,混作条播在干草产量、全氮产量、％Ndfa和Ndfa等方面均优于间作与混作撒播模式,且高于单作苜蓿与牛尾草的平均值。用~(15)N同位素稀释法与~(15)N天然丰度法评估苜蓿的％Ndfa与Ndfa值时,无明显差异(P<0.05),前者还能准确测出混种牛尾革植株中的固氮产物转移量,后者则大大低估,甚至不能测出固氮产物转移。 相似文献
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本研究调查了秦山核电站站址周围50km半径范围内土壤、水和农作物的总α、总β放射性水平,土壤中天然放射性核素含量,以及γ外照射积累剂量。结果表明:土壤中总α、总β值分别为0.54—1.48×10~(-8)Ci/kg和1.90—2.96×10~(-8) Ci/kg,低于全国一般地区平均水平,且0—100cm土层变化不大。土壤中~238U、~226Ra、~232Th、~40k、~137Cs的放射性活性分别为0.67—5.00×10~(-9)、4.49—11.4×10~(-10)、0.88—1.69×10~(-9)、0.39—2.09×10~(-8)和0.89—4.32×10~(-10)Ci/kg。河水、湖水以及核电站废水排放口处海水总β值分别为1.32—8.62、3.6和2.55×10~(-12)Ci/L。大米和油菜叶中的总β值分别为2.53和3.0×10~(-9)Ci/kg。室内外月平均γ照射量各为10.6—14.7和9.16—13.7mR。 相似文献
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用~(15)N同位素稀释法研究牧草的氮素营养 总被引：4，自引：1，他引：3
利用同位素示踪技术研究不同施肥处理对黑麦草单播及黑麦草与白三叶混播条件下不同时期牧草茎叶N %与对白三叶的共生固氮的影响。结果表明 :( 1 )混播或单播黑麦草的N %在施肥后 67d达到最高值 ,其后随时间的推移逐渐降低 ;( 2 )混播白三叶的N %在施肥后 67d达到最高 ,随后稍有降低 ,其后又有所增加 ,这与白三叶固氮活性逐步提高有关 ;( 3 )施N水平较低时 ( 1 64kg硫铵 /hm2 ) ,不同时期刈割的混播黑麦草的N %均高于单播黑麦草的N % ,显然是由于白三叶共生固氮所产生的N素为黑麦草提供了新的氮源 ;( 4 )混播白三叶中N素的主要来源是共生固氮 ,混播黑麦草和单播黑麦草中N素的主要来源是土壤 ;( 5)施N处理对黑麦草和白三叶N %的影响差异显著。 相似文献
6.
丛枝菌根真菌对羊草气体交换和δ~(13)C、δ~(15)N的组成影响 总被引：1，自引：0，他引：1
采用盆栽方法研究接种两种丛枝菌根真菌Glomus intraradices,Glomus claroidum对内蒙古典型草原优势种羊草(Leymus chinensis)的气体交换和稳定性同位素组成的影响,对羊草生长第45、60和75天的测定结果表明,丛枝菌根真菌能提高植株的含磷量、叶片的气孔导度和光合速率,降低植株δ15N值,但对羊草的内在水分利用效率和δ13C的组成未产生显著影响;植株生长的不同时期对其气体交换和稳定性同位素δ13C、δ15N均产生显著影响;时间和接种的相互作用显著影响植株的光合速率、δ13C和δ15N;羊草气孔导度和光合速率的提高归因于菌根真菌改善植株磷营养和增加根系碳分配所致;而植株内在水分利用效率和δ13C无显著性差异是因为气孔导度和光合速率总是发生同方向变化造成的;菌根植物具有较低δ15N是源于菌根真菌吸收N,并富集15N,转运给植株贫化的15N所致。试验结果为认识草原植物的碳水平衡和N循环提供了新的思路和借鉴。 相似文献
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黄土塬区三种豆科牧草的土壤养分剖面分布特征与平衡 总被引：4，自引：0，他引：4
为了解豆科牧草短期种植对土壤养分环境影响的进程和规律,通过田间试验对沙打旺、苜蓿和胡枝子等3种豆科牧草以不同密度单播、混播对土壤有机质、全氮、全磷剖面分布和平衡输出的影响进行了定性和定量分析。所有处理土壤全氮和有机质含量在土壤剖面2m深度范围内均呈典型的“S”形分布,全磷呈抛物线形分布。单播牧草固氮能力与播种密度呈正相关;苜蓿固氮能力最强,高密度下表观生物固氮量达507．5kg·hm^-2。沙打旺生长1年可使土壤有机质平均净增3．51％。沙打旺和苜蓿全磷平均输出比率分别为43．14％和40．24％,显著高于胡枝子（23．74％）;胡枝子与沙打旺、苜蓿的两两混播处理和3种牧草混播处理平均全磷输出比率分别为20．73％、26．33％、25．83％。试验结果表明,3种豆科牧草均可显著提高土壤有机质累积,沙打旺和苜蓿对土壤全氮和全磷的消耗显著大于胡枝子,但前两者的固氮能力也强于后者。以适当密度进行的不同牧草混播处理由于种间良性竞争和共生协调作用可优化混播群体对土壤养分的消耗利用。 相似文献
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《核农学报》2009,23(6):1036-1042
利用预浓缩装置-气相色谱/燃烧-同位素比值质谱仪（PreCon-GC/C-IRMS）联用系统,建立了就采样、浓缩和在线质谱分析大气CH4中稳定碳同位素组成的测定方法。通过多组试验对比,分析并讨论了利用PreCon-GC/C-IRMS联用技术测定大气CH4中碳稳定同位素比值的试验条件、系统线性、稳定性及准确度和精密度等。结果表明,在本方法条件下,当离子流强度在1.0 V～20 V时,系统线性良好（斜率S=0.04 ‰/V）,在4.0 V～15 V内其线性（斜率S=0.03 ‰/V）优于总体线性;系统测量稳定性可靠,δ13C值的测定结果的S.D＜0.3 ‰,最大偏差＜0.5 ‰,回收率达99.99%,准确度和精度均符合分析与研究要求。利用该系统对室内和室外草坪地空气中CH4的碳稳定同位素组成做了初步测试,其碳同位素的平均值分别为-31.358 ‰和-33.085 ‰,且相同地点区域空气中CH4的δ13C值,在1 d内和不同日期间的变化均在0.5 ‰以内,重现性良好。 相似文献
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稳定性同位素碳、氮在牛不同组织中的变化规律 总被引：5，自引：2，他引：3
稳定同位素分析是追溯食品来源的一种有效技术。本文主要探讨了在相同的饲养条件下,牛不同组织中碳、氮同位素组成的变化情况以及品种对其的影响。利用同位素比率质谱仪测定了不同部位脱脂牛肉、不同部位粗脂肪、牛尾毛、血液、肝脏及饲料中的δ13C值和δ15N值,并进行了统计分析。结果表明,品种因素不影响组织中的碳、氮同位素组成;肌肉不同部位、血液、肝脏、牛尾毛之间的δ13C值无显著差异,而肝脏中的δ15N值极显著地高于其它组织;不同部位粗脂肪间的δ13C值也无显著差异。结果说明稳定性同位素碳、氮在牛不同组织中的分馏效应是不一致的。 相似文献
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It may be desirable to minimize dinitrogen (N2) fixation in alfalfa (Medicago saliva L.) when a source of inorganic nitrogen (N), such as manure, is readily available. Our objectives were to determine the N2 fixation response of eight alfalfa germplasms to inorganic N and to characterize plant‐to‐plant variation for this trait. Seed was sown in vermiculite and irrigated with nutrient solution in growth chambers. Herbage was removed at 71 d and treatments of 1, 3, 5, or 10 mM N were applied as 15N‐depleted ammonium nitrate (NH4NO3). After 34 d of regrowth, herbage was removed and analyzed for dry mass, total N concentration, and N isotope ratio. Increased availability of inorganic N resulted in a linear increase in herbage weight, height, shoot number, and N concentration, and consistently decreased N2 fixation for all germplasms. Estimated N2 fixation was greater than zero at the highest rate of inorganic N, which we speculate was due, in part, to remobilized root and crown N, because nodules appeared to be nonfunctional. Across all treatments, N2 fixation correlated best with herbage N concentration, but there was no relationship between these variables within a given N treatment concentration. Significant variation in reliance on N2 fixation in the presence of inorganic N existed in all eight germplasms. 相似文献
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Cotyledons arc an important nitrogen (N) source for germination and early seedling development of alfalfa (Medicago sativa L.). The objectives of these studies were to determine changes in cotyledon N or protein concentration during alfalfa seedling growth and to ascertain the influence of N availability on seedling development and cotyledon protein use. Greenhouse‐grown seedlings of effective and ineffective ‘Saranac’ were grown in sand with either minus‐N nutrient solution, or a nutrient solution containing 20 mM ammonium nitrate as an N source. Shoots, cotyledons, and roots were sampled between 3 and 43 days after planting, and N or protein concentrations and dry wts. determined. Cotyledon protein or N declined rapidly in both effective and ineffective Saranac between 3 and 15 days after planting, but was more extensive for ineffective Saranac 19 days after planting and later. Nitrogen per seedling increased in effective Saranac between 15 and 22 days after planting indicating that dinitrogen fixation had begun. At 22 days after planting root and shoot N of effective Saranac increased whereas cotyledon N continued to decline. For effective Saranac applied N did not alter the decline in cotyledon protein concentration, but cotyledon protein per seedling was slightly greater with applied N because of greater cotyledon mass per seedling. N application to ineffective Saranac resulted in responses similar to those of effective Saranac, whereas more extensive N and protein losses occurred in cotyledons of ineffective Saranac seedlings without N. Soil N application and nodule effectivity enhanced seedling development of alfalfa, but did not prevent the rapid decline in cotyledon N and protein. 相似文献
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M. I. Makarov T. I. Malysheva A. A. Ermak V. G. Onipchenko A. L. Stepanov O. V. Menyailo 《Eurasian Soil Science》2011,44(12):1381-1388
The symbiotic fixation of atmospheric nitrogen by leguminous plants in the alpine community of a lichen heath at the Teberda
State Biosphere Reserve is well adapted to low soil temperature characteristic for the altitude of 2800 m a.s.l. For the determination
of the N fixation by isotopic methods (the method of the natural 15N abundance and the method of isotopic 15N dilution), Trifolium polyphyllum was taken as the control plant. This plant was used as it does not form symbiosis with the nitrogen-fixing bacteria in the
highlands of the Northern Caucasus Region. The contribution of the N fixation to the N nutrition of different leguminous plant
species as determined by the natural 15N abundance method amounted to 28–73% at δ15N0 = 0‰ and 46–117% at δ15N0 = −1‰; for the determination of the N fixation by the method of the isotopic label’s dilution, it was 34–97%. The best correlation
of the results obtained by these two isotopic methods was observed for the natural fractionation of the N isotopes in the
course of the N fixation in the range of −0.5 to −0.7‰. The determination of the nitrogenase activity of the roots by the
acetylene method confirmed the absence of N fixation in T. polyphyllum and its different contribution to the N nutrition of different species of leguminous plants. 相似文献
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S. Kilian P. von Berswordt-Wallrabe H. Steele D. Werner 《Biology and Fertility of Soils》2001,33(5):358-364
N fixation by different faba bean (Vicia faba) cultivars was studied using the natural abundance method. The delta 15N ('15N) values of the faba beans and the reference plants differed by 4.6-7.0. The non-nodulating V. faba cv. F48 seems to be the best reference plant for nodulated and N2-fixing V. faba. Significant differences occurred in the quantity of N2 fixation of six V. faba cultivars. The average fraction of N derived from air (FNdfa) estimated from leaf material ranged between 69 and 80%. Shoot-based estimates of N fixation varied between 200 and 360 kg N ha-1. N fixation was affected more by differences in FNdfa than by differences in total N accumulation. Fixation data calculated with the non-nodulated reference plant V. faba cv. F48 were lower than those calculated with cabbage (Brassica oleracea) and ryegrass (Lolium perenne) as reference plants. Of all reference plants, non-N2-fixing V. faba cv. F48 has a root system and temporal pattern of N assimilation that is the one most similar to that of N2-fixing V. faba plants. Cv. F48 showed senescence as did the other V. faba cultivars after pod-fill was complete, whereas cabbage, ryegrass and camomile had a later senescence period. N fixation during pod-filling appears more important for a good yield than N2 fixation abilities in the earlier growth period. The best V. faba cultivars left about 100 kg N ha-1 in residual material on the field as fertilization for the following crops. 相似文献
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A grazing experiment was conducted in Brandon, Manitoba, Canada. The objectives were to examine the effects of including alfalfa and fertilizer management on N2 fixation by alfalfa and plant N dynamics, and to compare N budgets in the four contrasting pasture systems and external energy inputs between fertilizer-N-based and legume-based pasture systems. Estimates of annual amounts of N2 fixed, based on shoot herbage production in grazed mixed alfalfa/grass pastures, ranged from 40 to 118 kg N ha−1 y−1. The amounts would be in the range of 52-153 kg N ha−1 y−1, if the amounts of fixed N stored in the roots, were included. Compared to grass-only pastures, total amounts of N2 fixed in the mixed pastures should be sufficient to improve total external N inputs, replace N fertilizer and sustain plant protein for grazing. The reliance of alfalfa (Medicago sativa L.) on N2 fixation for growth was high (70-95%), and %N derived from the atmosphere by alfalfa (%Ndfa) was not affected by P fertilizer management. Thus, the amounts of N2 fixed were predominantly regulated by alfalfa dry matter productivity. The data also indicated that alfalfa fixed 27 kg N t−1 dry matter produced. In mixed alfalfa/grass pastures, high soil mineral N uptake by companion grasses, was essential to effectively utilize N that was fixed by alfalfa and returned to soils through the decomposition of alfalfa litter and roots. Compared to grass-only pastures with or without N fertilizer, alfalfa-based pastures could supply sufficient plant protein for grazing animals through N2 fixation, and at same time, sustain animal productivity with only 28% of the external energy input of the grass-only pasture with N fertilizer. 相似文献
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陕西关中地区肉牛产地同位素溯源技术初探 总被引：3，自引：1，他引：2
为应用牛组织中C、N同位素组成的区域分布和同位素指标溯源肉牛产地,本文利用同位素比率质谱仪(IRMS)对陕西关中不同区县来源的牛尾毛样品的1δ3C和1δ5N值进行检测,通过聚类分析,研究陕西关中地区肉牛组织中同位素组成的区域分布情况。结果表明,杨凌区、眉县牛尾毛样品聚为一类;乾县、永寿县样品聚为一类;麟游县样品聚为一类;扶风县、岐山县和凤翔县分类不十分明显,分散在上述3类中。说明陕西关中不同地区肉牛组织中同位素组成存在差异,利用它们可进行肉牛地域的小范围溯源。 相似文献