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1.
Effects of nitrogen fertilization and maturity of bromegrass on nitrogen and amino acid utilization by cows. 总被引：1，自引：0，他引：1
Four nonlactating Holstein cows (593 kg) with ruminal cannulas were fed bromegrass hay that was fertilized with 0 or 89 kg of N/ha and harvested in the late-boot or full-head stage of maturity. Total tract apparent digestibility of N was less for full-head than for late-boot bromegrass (48 vs 64%; P less than .01) and was greater for N-fertilized than for unfertilized bromegrass (60 vs 52%, P less than .01). True N digestibility was greater (P less than .01) by cows fed late-boot hay than by those fed full-head bromegrass (85 vs 81%). Maturity did not affect N retention. Nitrogen fertilization increased N retained, both grams per day (70 vs 20; P less than .01) and as a percentage of N intake (P less than .01). Nitrogen and amino acid disappearance kinetics were determined in situ. Rate constants for N disappearance within rapidly and slowly degraded pools were not different among treatments, but because late-boot had a larger proportion of N in the rapidly degraded pool, overall disappearance rate for N was faster (P less than .05) for late-boot than for full-head bromegrass (12.0 vs 7.1 %/h). Treatment effects observed for individual amino acids were similar to those found for N. Both composition and kinetic data were needed to explain differences in N digestion and balance. Distribution of N within the forage had profound effects on the N economy of the cows. 相似文献
2.
【目的】研究不同的施氮制度对燕麦/豌豆间作体系中燕麦的吸收情况以及对土壤氮素的影响。【方法】采用随机区组试验设计,设N0(不施氮)、N1(基肥20%+分蘖期追肥20%+开花期追肥60%)、N2(基肥20%+分蘖期追肥30%+开花期追肥50%)和N3(基肥20%+分蘖期追肥40%+开花期追肥40%)4个施氮制度;3种种植模式(燕麦/豌豆间作、燕麦单作和豌豆单作),研究施氮制度对间作燕麦氮素吸收和土壤氮素的影响。【结果】施氮制度和间作对燕麦籽粒产量、氮素吸收和土壤氮素影响显著。间作燕麦籽粒产量在N2处理下最大,较N3增产22.48%。随着生育期的推进,在拔节期、抽穗期、灌浆期和成熟期间作燕麦的吸氮量较单作燕麦分别提高了26.5%、15.8%、7.3%和17.1%;间作燕麦在N2处理下吸氮量最大,为71.2 kg/hm2,较N0增加了49.9%。在0～20 cm土层间作燕麦的土壤全氮含量在N0、N1、N2和N3处理下分别较单作提高12.9%、11.2%、15.4%和6.9%;间作燕麦在拔节期、抽穗期、灌浆期和成熟期的土壤硝态氮含量和铵态氮均高于单作燕麦。【结论】在20～... 相似文献
3.
The objective of the study was to determine the influence of either oral or intramuscular administration of stanozolol on nitrogen retention in dogs by using a non-invasive 15N-amino acid tracer technique. Ten healthy, intact, adult male sled dogs received either stanozolol tablets, 2 mg/dog PO, q12h, for 25 days (Group 1, n = 5) or an intramuscular injection of 25 mg of stanozolol on Days 7, 14, 21, and 28 (Group 2, n = 5). A 15N amino acid (5.27 mmol) was infused intravenously into each dog on Day 0 (before stanozolol treatment) and on Day 31 (after stanozolol treatment). Urine was collected by catheterization from each animal 3 times daily for 3 consecutive days. The 15N-urea enrichment in urine was determined by high-resolution mass spectrometry and the total amount of urea in the urine was determined. Both oral and injectable stanozolol resulted in significant (P < 0.05) increases in amino acid nitrogen retention compared to pretreatment values. Oral stanozolol increased nitrogen retention from 29.2 +/- 8.2% to 50.3 +/- 9.2%, while stanozolol injection increased nitrogen retention from 26.6 +/- 9.9% to 67.0 +/- 7.5%. The response to intramuscular administration was significantly greater than the response to the oral dosing regime. Stanozolol increases amino acid nitrogen retention in dogs, as has been previously observed in rats. This action of stanozolol may be beneficial in dogs under stress of surgical trauma and chronic disease. 相似文献
4.
人类活动及化石燃料应用的加剧增加了大气中的氮沉降，对陆地生态系统氮素循环过程造成了显著影响，从而影响生态系统生产力及稳定性。草地作为陆地生态系统的重要组成部分，常因为人们的过度利用及保护意识不强，造成资源损失、养分失衡，严重限制了畜牧业的发展。探究氮沉降对草地生态系统氮循环的影响对提高草地生产力，合理开发与利用草地资源具有重要意义。通过追踪国内外已有的研究成果发现，大部分氮添加抑制了生物固氮过程，促进了土壤的硝化作用、反硝化作用和矿化作用，并抑制了固氮微生物活性，增加了硝化功能微生物氨氧化细菌（AOB）、反硝化微生物功能基因nirK、nirS、narG、nosZ的丰度。但是因为草地本底氮营养差异及施氮措施的不同导致少数研究中土壤氮循环对氮沉降的响应出现不同结果。通过总结已有研究发现：1）土壤本底营养及氮吸收阈值的不同造成氮沉降对氮循环的影响存在差异；2）微生物作为土壤氮素循环的重要参与者，对不同施氮时间、频率、数量等的响应存在差异；3）土壤中氮循环的各环节紧密耦联，相互影响，但现有的研究大多只针对某一环节开展，研究结果不具有全面性。因此，在未来的研究中，应针对不同营养水平的草地，加强氮控制条件下土壤氮循环微生物变化的研究，关注多环节的耦联关系，对于提高草地生态系统功能，并减轻氮素损失对环境造成的威胁意义重大。 相似文献
5.
本研究采用砂培、浇灌营养液方法种植颠茄(Atropa belladonna),研究不同铵硝配比(0∶100、25∶75、50∶50、75∶25、100∶0)在不同处理时间(7、14、21、28d)对颠茄干重、叶绿素和主要含氮化合物含量以及氮代谢关键酶活性的影响,为颠茄的合理施肥、科学种植提供理论依据。结果表明,颠茄叶片叶绿素、游离氨基酸(FAA)及可溶性蛋白(SP)含量随铵态氮比例增加而升高,其中叶绿素、FAA含量在铵硝比75∶25时最高,SP含量在铵硝比50∶50时最高,但这种影响在不同处理时间表现并不相同;整个处理期内,全硝营养下颠茄地上部和地下部干重明显高于铵硝混合处理及全铵处理,且叶片硝酸还原酶(NR)、谷氨酰胺合成酶(GS)活性较高,硝态氮含量也最高。综上,增加硝态氮含量能够促进颠茄干物质的积累以及NR和GS活性,合理补充铵态氮则能提高叶片叶绿素、FAA及SP含量,因此铵硝结合供氮且铵硝配比为25∶75更有利于颠茄的生长和氮素代谢。 相似文献
6.
R Beza 《Archives of Animal Nutrition》1987,37(12):1101-1114
The influence of the time (t = 3, 6, 9, 12 and 16 days) of feeding on a protein-free diet (PFD) and the size of shrunk body mass (SB), increasing with age but decreasing with the duration of feeding on PFD, on the excretion of endogenous urinary nitrogen (EUN) were investigated. The experiment was on 350 male rats from 23 to 275 days of age and mean SB from 39 to 430 grammes, divided into 14 age groups (k = 14). The material and the method of the experiment as well as the composition of PFD were described in detail in part one of this work (Beza, 1986). The linear analysis of covariance showed that the EUN excreted after 3, 6, 9, 12 and 16 days on PFD as well as the average daily EUN did not significantly correlate with the initial body mass (SBi). It were calculated: 1. In relationship EUN(t) the slope ratios bk and intercepts ak, differed between the groups of age significantly. The ak values but not the bk, were closely correlated with the initial body mass SBi (r for ak values = 0.947***) indicating that the amount but not the rate of EUN excretion was closely related to SBi; 2. the daily EUN excretion at 1, 3, 6, 9, 12 and 15 days on PFD in relation to body mass in these days-EUNd(SBd) is described by the equation: EUNd = Ad.SBd 0.872 less than 1, in which Ad decreased from 287 mg N/SBd 0.872 on the first day to 167 mg N/SBd 0.872 on the 15th day on PFD; 3. the daily excretion of EUN(y) in relation to the daily body mass (x1) and to the day on PFD (x2) is described by the equation: EUNd(y) = 286.8.x1(0.872).x2(-0.1993); R = 0.987*** with N in mg, SB in kg. There was a directly proportional relationship between EUNd and SB0d 0.872 only (b1 = 1), whereas between EUNd and SBd 0.67 as well as between EUNd and SBd 0.75 the slope ratios b1 were 1.308 and 1.163, respectively and were significantly higher than one. With prolonged feeding on PFD for 15 days, the rate of EUNd excretion decreased in accordance to b2 = -0.1993 less than 0**, independently of the age and the initial SB of the rats.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
7.
大气氮沉降对黄土高原土壤氮特征的影响 总被引：2，自引：0，他引：2
为了解氮沉降对土壤氮特征的影响,通过人工氮肥添加模拟试验,分析在不同氮添加梯度下黄土高原典型草原土壤全氮（TN）和轻组有机氮（LFON）含量的变化特征。结果显示,氮添加对黄土高原典型草原土壤0～40 cm土层TN含量没有显著影响(P>0.05);但是显著增加了土壤表层（0～10 cm）的LFON含量和LFON/TN(P<0.05)。氮添加对10～20和20～40 cm的LFON含量和LFON/TN没有显著影响(P>0.05)。本研究表明,在黄土高原典型草原实施氮添加的初期,LFON含量和LFON/TN比TN含量能更早地显示出土壤氮特征的变化。 相似文献
8.
为了揭示大气氮沉降对栽培草地植物氮同化物积累的影响,本试验以无芒雀麦（Bromus inermis）和白三叶（Trifolium repens）为对象,通过人工增氮试验（浓度设置为0、6、12和24 g N·m-2·a-1）来研究豆科和禾本科牧草的氮同化物积累的变化规律。结果表明,在不同氮浓度处理下,叶绿素、叶全氮、可溶性蛋白、精氨酸和脯氨酸等氮同化物含量变化极显著（P<0.01）,在氮沉降浓度为12 g N·m-2·a-1范围内随氮沉降浓度增加而呈增加趋势（除脯氨酸含量）,但是两种牧草氮同化物的积累量差异较大,氮沉降对禾本科牧草的氮同化物积累的影响高于豆科牧草。精氨酸含量与氮沉降浓度间存在极显著正相关（R2均达到0.99）,因此,精氨酸可作为草本植物对氮沉降增加的敏感指标。 相似文献
9.
光周期与氮肥互作对华农1号青饲玉米碳氮代谢相关酶的影响 总被引：1，自引：1，他引：1
于2005年3-7月,采用盆栽试验,设置3个不同光照长度处理和氮素水平,研究了不同光照时数及氮素水平对远缘玉米杂交种华农1号青饲玉米碳氮代谢相关酶活性的影响.结果表明,在苗期,16 h光照处理下植株叶片磷酸烯醇式丙酮酸羧化酶、蔗糖磷酸合成酶、蔗糖合成酶、谷氨酰胺合成酶和硝酸还原酶等酶的活性显著低于13和10 h光照处理;至抽雄期和收获期,13和10 h处理下植株叶片各种酶的活性下降速率较快,而16 h处理下酶活性下降缓慢且显著高于13和10 h处理.在抽雄期或收获期,16 h处理下叶片各种酶的活性均随施氮量的增加而增加,但在13和10 h处理下均有几种酶的活性在高氮素水平下出现下降的趋势.总的看来,在16 h光照处理下,植株苗期碳氮代谢相对较弱,到中后期代谢能力明显提高,且耐高氮能力也较强,收获期植株叶片酶的活性显著高于13和10 h处理. 相似文献
10.
高温胁迫下不同氮肥处理对高羊茅氮代谢的影响 总被引：3，自引：1，他引：2
采用盆栽试验,研究了不同氮肥（NO3--N、NH4+-N、NH4NO3-N）处理对高羊茅品种凌志Festuca arundinacea cv. Barlexas在高温38/30 ℃（昼/夜）胁迫下叶片内硝态氮含量、铵态氮含量以及参与氮同化和代谢过程的主要酶活性的影响。结果表明：随着胁迫时间的延长,经过不同氮肥处理的植株中硝态氮含量先升后降,而铵态氮含量呈上升趋势,其中NH4NO3-N处理株的硝态氮含量最高,铵态氮含量最低,NH4+-N处理株的铵态氮含量最高;不同处理株中的硝酸还原酶（NR）活性呈下降趋势,而谷氨酰胺合成酶(GS)和谷氨酸合成酶（GOGAT）活性均呈先升后降的趋势,总体上,NH4NO3-N处理株的NR、GS和GOGAT活性最高;NH4NO3-N和NO3--N处理株的谷氨酸脱氢酶（GDH）活性均呈下降趋势,而NH4+-N处理株的GDH活性呈上升趋势。在试验条件下,经NH4NO3-N处理的高羊茅受氧化胁迫程度最小,耐热性最好,有利于高羊茅越夏和延长其绿期。 相似文献
11.
Effect of nitrogen intake on nitrogen recycling and urea transporter abundance in lambs 总被引：5，自引：0，他引：5
Urea recycling in ruminants has been studied extensively in the past, but the mechanisms regulating the amount of urea recycled or excreted remain obscure. To elucidate the role of urea transporters (UT) in N recycling, nine Dorset-Finn ewe lambs (20.8 +/- 0.8 kg) were fed diets containing 15.5, 28.4, and 41.3 g of N/kg of DM for 25 d. Nitrogen balance and urea N kinetics were measured during the last 3 d of the period. Animals were then slaughtered and mucosa samples from the rumen, duodenum, ileum, and cecum, as well as kidney medulla and liver, were collected. Increasing N intake tended to increase N balance quadratically (1.5, 5.1, and 4.4 +/- 0.86 g of N/d, P < 0.09), and linearly increased urinary N excretion (2.4, 10, and 16.5 +/- 0.86 g N/d, P < 0.001) and plasma urea N concentration (4.3, 20.3, and 28.4 +/- 2.62 mg of urea N/dL, P < 0.001), but did not affect fecal N excretion (5.0 +/- 0.5 g of N/d; P < 0.94). Urea N production (2.4, 11.8, and 19.2 +/- 0.83 g of N/d; P < 0.001) and urinary urea N excretion (0.7, 7.0, and 13.4 +/- 0.73 g N/d; P < 0.001) increased linearly with N intake, as well as with the urea N recycled to the gastrointestinal tract (1.8, 4.8, and 5.8 +/- 0.40 g of N/d, P < 0.001). No changes due to N intake were observed for creatinine excretion (518 +/- 82.4 mg/d; P < 0.69) and clearance (46 +/- 10.7 mL/min; P < 0.56), but urea N clearance increased linearly with N intake (14.9, 24.4, and 34.9 +/- 5.9 mL/min; P < 0.04). Urea N reabsorption by the kidney tended to decrease (66.3, 38.5, 29.1 +/- 12.6%; P < 0.06) with increasing N content of the diet. Increasing the level of N intake increased linearly the weight of the liver as a proportion of BW (1.73, 1.88, and 2.22 +/- 0.15%, P < 0.03) but only tended to increase the weight of the kidneys (0.36, 0.37, and 0.50 +/- 0.05%, P < 0.08). Urea transporter B was present in all the tissues analyzed, but UT-A was detected only in kidney medulla, liver, and duodenum. Among animals on the three diets, no differences (P > 0.10) in UT abundance, quantified by densitometry, were found. Ruminal-wall urease activity decreased linearly (P < 0.02) with increasing level of N intake. Urease activity in duodenal, ileal, and cecal mucosa did not differ from zero (P > 0.10) in lambs on the high-protein diet. In the present experiment, urea transporter abundance in the kidney medulla and the gastrointestinal tract did not reflect the increase in urea-N reabsorption by the kidney and transferred into the gut. 相似文献
12.
Three lamb metabolism experiments were conducted to investigate the effects of chronic administration of the novel urease inhibitor N (n-butyl) thiophosphoric triamide (NBPT) on ruminal N metabolism, fermentation, and N balance. In Exp. 1, ruminally cannulated wethers (n = 28; 45.0 +/- .9 kg) were administered one of seven doses of NBPT (0 [control], .125, .25, .5, 1, 2, or 4 g of NBPT daily) and fed a common cracked corn/cottonseed hull-based diet twice daily containing 2% urea at 2.5% of initial BW for the duration of the 15-d experiment. Overall, NBPT decreased (linear P < .0001; quadratic P < .001) ruminal urease activity, resulting in linear increases (P < .0001) in ruminal urea and decreases in ruminal NH3 N concentrations. However, the detection of an NBPT x day interaction (d 2 vs 15; P < .01) indicated that this depression in urea degradation diminished as the experiment progressed. Increasing NBPT linearly decreased (P < .01) total VFA concentrations on d 2 of the experiment, but it had no effect (P > .10) on d 15. Increasing NBPT had no effect (P > .10) on DM or ADF digestibilities, but it linearly decreased (P < .01) N digestibility. Supplementing NBPT produced a linear increase (P < .05) in urinary N excretion and a linear decrease (P < .01) in N retention. In Exp. 2, ruminally cannulated wethers (n = 30; 46.8 +/- .6 kg) were fed one of two basal diets (2.0 vs 1.1% dietary urea) at 2.5% of initial BW and dosed with either 0 (control), .25, or 2 g of NBPT daily for the duration of the 15-d experiment. There were no NBPT x dietary urea interactions (P > .10) for Exp. 2. Increasing NBPT depressed (linear and quadratic P < .0001) ruminal urease activity, producing linear (P < .0001) increases in urea N and linear decreases in NH3 N in the rumen. As in Exp. 1, an NBPT x day interaction (P < .05) was noted for urea, NH3 N, and total VFA concentrations; the maximum response to NBPT occurred on d 2 but diminished by d 15 of the experiment. Administration of NBPT did not influence (P > .10) DM, ADF, or N digestibilities in Exp. 2. In Exp. 3, wether lambs (n = 30; 26.4 +/- .7 kg) were subjected to the same treatment regimen as in Exp. 2 for a 14-d N balance experiment. Although several NBPT x dietary urea interactions (P < .05) were noted, increasing NBPT did not affect (P > .10) N digestibility. Administration of NBPT quadratically increased (P < .10) urinary N excretion, producing a linear decrease (P < .05) in N retention. These results suggest that although NBPT is capable of inhibiting ruminal urease short-term, the ruminal microflora may be capable of adapting to chronic NBPT administration, thereby limiting its practical use in improving the utilization of dietary urea. 相似文献
13.
1. Quail blastoderm cells isolated from the yolk were preserved in liquid nitrogen. 2. Frozen-thawed blastoderm cells of the quail were viable and survived in vitro. By injecting the frozen-thawed cells into chick embryos, quail-chick chimaeras were produced. 相似文献
14.
施氮水平对甜高粱硝酸盐含量和氮素利用特性的影响 总被引：1，自引：0，他引：1
试验采用完全随机区组设计,分别于2009和2010年在华东农区生态条件下进行田间试验,研究不同施氮水平(0,100,200,300,400,500kg N/hm2)对大力士甜高粱硝酸盐积累,粗蛋白含量和氮素利用特性的影响。结果表明,随着生育期的推进,植株地上部硝酸盐含量不断降低,相比于叶片,茎秆更有利于硝酸盐的积累。随着施氮水平的提高,粗蛋白生产效率(CPPE),氮素干物质生产效率(NDMPE),干物质生产效率(DMPE)和表观回收率(NARR)逐渐下降,说明施氮量越高,氮素利用越低,损失越大。粗蛋白(crude protein,CP)和游离氨基酸(free amino acid,FAA)含量均随施氮量的增加而增加,但FAA的增幅低于CP,施氮量为500kg N/hm2时,CP的平均增幅为6.11%,FAA的平均增幅为2.99%,说明施氮虽然增加了植株CP含量,但优质蛋白质比例下降。施氮提高了甜高粱硝酸盐含量,施氮量大于400kg N/hm2时,甜高粱硝酸盐含量大于0.2%,青饲时易导致家畜硝酸盐中毒。综合考虑,大力士甜高粱在华东农区较为适宜的施氮量为200~300kg N/hm2,既可满足对甜高粱高产优质的需求,提高氮素的利用效率,又可减少氮素流失和对土壤及地下水的污染。 相似文献
15.
龙须眼子菜对绵羊日粮养分消化率和氮沉积的影响 总被引：1，自引：0，他引：1
本文采用全粪全尿收集法,通过绵羊体内消化代谢试验,研究不同剂量龙须眼子菜对绵羊日粮养分消化率及氮沉积的影响。试验结果表明,绵羊日粮中添加20%～40%龙须眼子菜均能提高中性洗涤纤维(NDF)的消化率(P<0.05),添加20%显著提高养分的消化率和氮沉积量(P<0.05),添加30%对养分消化率和氮沉积量无显著影响(P>0.05)。而添加40%对养分消化率无显著影响(P>0.05),却使氮沉积率和沉积量显著降低(P<0.05)。因此,建议龙须眼子菜在绵羊日粮中最佳添加比例为20%,可以添加到30%。 相似文献
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前茬施氮对皖草2号草产量影响的研究 总被引：2，自引：1，他引：2
研究前茬施氮水平和施氮方式与后茬皖草2号草产量及全年草产量的动态关系.结果表明:前茬施氮能增加皖草2号的株高,尤以前茬氮肥分期施用处理最为明显.随前茬氮肥水平的加大,后茬皖草2号的鲜草、干草产量相应提高,其中前茬纯氮肥施用量达225 kg/hm2以上时,后茬皖草2号的鲜草、干草产量达到较高水平.相同施氮水平条件下,前茬氮肥分期施用比一次性基施的鲜草、干草产量高.前茬氮肥施用量的增加与氮肥分期施用均能提高小黑麦Triticale cereale-皖草2号Sorghum bicolor×S.sudanense的全年草产量,且差异达极显著水平,前茬纯氮施用量为300和375 kg/hm2且分期施用时,2茬牧草全年干草总产量均可达到较高水平,且两者之间的差异不显著. 相似文献
18.
氮素是禾本科植物生长和发育所必需的大量元素之一,但过量施用氮肥不仅造成环境污染,而且增加生产成本、降低收益。基于青藏高原地区披碱草属牧草种子需求量大、产量较低的现状,本研究以同德短芒披碱草、青牧1号老芒麦2个披碱草属牧草品种为试验材料,设置0、45、90、135、180和225 kg N·hm-2等6个氮肥施用水平,研究分析了施氮量对披碱草属牧草种子生产和氮肥利用效率的影响,以期为披碱草属牧草种子生产提供理论依据。结果表明,施氮可促进披碱草属牧草生长,能够显著提高其株高、分蘖数等牧草营养生产性状,同时可提高种子产量及单位面积生殖枝数、每穗小穗数、每穗种子数和种子千粒重等产量组分;且随着施氮量的增加,各生长性能指标呈现先增加后降低或趋于稳定的变化趋势。随着施氮量的增加,除青牧1号老芒麦氮肥利用效率先增加后降低外,2个品种氮肥农学利用率和偏生产力逐渐降低。本研究中,同德短芒披碱草和青牧1号老芒麦的种子产量分别为712～1661 kg·hm-2和701～1626 kg·hm-2。从节约成本角度考虑,在川西北高寒地区开展披碱草属... 相似文献
19.
R Beza 《Archives of Animal Nutrition》1986,36(7):571-583
Changes in the intake of dry matter (DM) of the protein-free diet (PFD) fed ad libitum were studied on male rats in relation to the shrunk body mass (SB) and duration of protein-free feeding (t). The intake of DM and changes of SB were investigated on the same rats and during the same experimental periods. The mean intake of DM in relation to PFD feeding periods t = 3, 6, 9, 12, 16 days and the daily DM intake (DMd) in relation to the daily shrunk body mass (SBd) were calculated on logarithmical values according to a model of linear regression y = a + bx and to a model of multiple regression y = b0 + b1x1 + b2x2. The rate of DM intake in relation to the duration of PFD feeding (t) did not differ significantly between age groups (k = 14) but the ak differed significantly. The common coefficient bc = 0.871 +/- 0.012 was less than 1***. This relationship is described by the equation: DM intake = Ak X t0.871, where: DM intake = the sum of intake in the periods of 3, 6, 9, 12 and 16 days (in grams), k = age group, t = PFD feeding period. No significant correlation (P less than 0.05) was found between bk and the initial body mass (SBi) or age of rats (r = -0.21 and -0.02, respectively) but between ak and SBi or age the correlation was highly significant (r = 0.960 and 0.832). This indicates that the amount but not the rate of DM intake depended on the initial body mass or age. The relation between DMd and SBd, the latter increasing with age but decreasing with the duration of PFD feeding, is described by equation: DMd intake = Ad X SBd0.503, where: DMd intake in grams, d = day 1 to 15 of PFD feeding, SBd = daily shrunk body mass in kilograms. The values of Ad decreased with the duration of PFD feeding. The using of multiple regression permitted to describe DMd intake as a function of SBd and (d) by a common equation: DMd intake = 27.02 X SBd0.503 X d-0.103; R = 0.976. Thus the daily DM intake was closely positively correlated with SBd and negatively correlated with the duration of protein-free feeding regardless of the age of rats.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
20.
为探究紫花苜蓿体内异黄酮与结瘤固氮及氮效率的关系,以紫花苜蓿品种中氮高效的"LW6010"和氮低效的陇东苜蓿为材料,采用室内营养液砂培,设5个氮素水平,研究了不同氮效率紫花苜蓿的异黄酮含量和固氮特性以及异黄酮合酶(IFS)和结瘤信号传递通路基因(nod)的表达。结果表明:紫花苜蓿的异黄酮含量与根瘤数、单株总根瘤重以及单株固氮潜力的相关性显著,并且在低氮胁迫时紫花苜蓿的异黄酮含量以及根瘤数、单株总根瘤重和单株固氮潜力均显著上升。另外,还发现:氮高效的"LW6010"紫花苜蓿在氮胁迫时,茎叶和根系中上调的IFS基因数量和上调幅度均大于氮低效的陇东苜蓿,因此促进了nod基因的高表达,最终提高了氮效率。综上所述,1)紫花苜蓿的结瘤固氮与异黄酮含量显著正相关,在外源氮素浓度改变时,紫花苜蓿能通过茎叶和根系中不同IFS基因的表达提高体内异黄酮含量,从而刺激nod基因表达来促进结瘤和提高单株固氮潜力;2)紫花苜蓿体内异黄酮含量的差异是决定其氮效率高低的重要原因,氮高效紫花苜蓿在氮胁迫时通过多个IFS基因的高表达促进异黄酮合成,进而刺激结瘤固氮,从而表现出氮高效。 相似文献