Ni胁迫对不同基因型谷子幼苗生长及氮素代谢的影响

采用盆栽土培法,研究了不同浓度Ni2+(0、25、50、100、150、200 mg/kg)对4种基因型谷子(13-36、B-7、晋谷51号、晋谷52号)幼苗生长,Ni2+富集与转运能力,叶片中硝态氮、氨态氮、可溶性蛋白质、脯氨酸含量及氮代谢相关酶硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、谷氨酸脱氢酶(GDH)活性的影响。结果表明:Ni2+胁迫下,4种基因型谷子幼苗的根长、苗长、生物量随Ni2+浓度增加逐渐降低,体内Ni2+含量逐渐增加,与对照组差异显著(P0.05)。在所试浓度范围内,4种基因型谷子幼苗叶片中的硝态氮含量、NR、GS、GOGAT活性表现为低浓度(25—50mg/kg)增高和高浓度(50—200 mg/kg)降低,而GDH活性在Ni2+浓度为100mg/kg以上时下降,氨态氮含量在50—150 mg/kg处理组中为对照的1.14—3.02倍。不同浓度Ni2+处理后,4种基因型谷子幼苗叶片中的脯氨酸含量均有不同程度的提高,而可溶性蛋白质含量呈明显下降趋势。实验结果证明,Ni2+胁迫抑制了谷子幼苗对硝态氮的吸收,降低了叶片中NR、GS、GOGAT活性,影响了氨的同化作用,使谷子幼苗的氮素代谢发生紊乱,不同基因型谷子对Ni2+胁迫的毒性效应存在差异。4种基因型谷子对Ni2+的耐性顺序为13-36B-7晋谷51晋谷52。     

亚低温条件下外源褪黑素对甜瓜幼苗氮代谢及渗透调节物质的影响

以甜瓜品种‘羊角酥瓜’幼苗为试材,利用人工气候室进行亚低温处理(昼/夜18℃/12℃)6 d,研究外源褪黑素(MT)对亚低温条件下甜瓜幼苗叶片氮代谢酶[硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)和谷氨酸脱氢酶(GDH)]活性、叶片总氮、铵态氮、硝态氮和渗透调节物质含量的影响.结果表明:与对照相比,亚低温处理降低了甜瓜总氮、硝态氮及硝酸还原酶活性,增加了铵态氮含量,抑制了甜瓜幼苗的生长.外源MT可显著提高亚低温下甜瓜幼苗氮代谢酶的活性,尤其可显著提高叶片GS和GOGAT活性,从而有效降低铵态氮含量;外源MT还可以提高叶片脯氨酸、可溶性蛋白质和可溶性糖的含量,进而降低了亚低温对细胞膜的伤害,表现为甜瓜叶片相对电导率和丙二醛(MDA)含量较低.总之,在亚低温条件下,外源MT在一定程度上可通过降低甜瓜叶片铵态氮含量和促进渗透调节物质的积累,降低膜质过氧化水平,从而增加其对亚低温的适应性.     

亚低温条件下外源褪黑素对甜瓜幼苗氮代谢及渗透调节物质的影响

以甜瓜品种‘羊角酥瓜’幼苗为试材,利用人工气候室进行亚低温处理(昼/夜18 ℃/ 12 ℃)6 d,研究外源褪黑素（MT）对亚低温条件下甜瓜幼苗叶片氮代谢酶\[硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)和谷氨酸脱氢酶(GDH)\]活性、叶片总氮、铵态氮、硝态氮和渗透调节物质含量的影响.结果表明：与对照相比,亚低温处理降低了甜瓜总氮、硝态氮及硝酸还原酶活性,增加了铵态氮含量,抑制了甜瓜幼苗的生长.外源MT可显著提高亚低温下甜瓜幼苗氮代谢酶的活性,尤其可显著提高叶片GS和GOGAT活性,从而有效降低铵态氮含量;外源MT还可以提高叶片脯氨酸、可溶性蛋白质和可溶性糖的含量,进而降低了亚低温对细胞膜的伤害,表现为甜瓜叶片相对电导率和丙二醛(MDA)含量较低.总之,在亚低温条件下,外源MT在一定程度上可通过降低甜瓜叶片铵态氮含量和促进渗透调节物质的积累,降低膜质过氧化水平,从而增加其对亚低温的适应性.     

外源亚精胺对高温胁迫下黄瓜幼苗氮素代谢的影响

以较为耐热的黄瓜品种‘津春4号’为试材,在人工气候箱中,采用石英砂培加营养液浇灌的栽培方式,研究了外源亚精胺( Spd)对高温胁迫(42℃)下黄瓜幼苗氮素代谢的影响.结果表明:短期高温胁迫处理,尤其是4h内,植株硝态氮含量降低而铵态氮含量升高;外源Spd预处理使幼苗体内硝态氮和铵态氮含量升高且硝酸还原酶(NR)活性增强.较长期高温胁迫处理下,幼苗根系中硝态氮含量升高但向地上部运输受阻,根系NR钝化,根系和叶片中铵态氮含量均显著升高;高温胁迫下喷施Spd,除进一步促进根系吸收硝态氮且向地上部运输外,根系和叶片NR活性亦有所升高,从较长期的效果看,外源Spd还具有防止铵态氮过度积累、促进幼苗体内氮素代谢趋于正常的作用.     

纯化腐植酸对氮胁迫下黄瓜幼苗生长和氮代谢的影响

为研究纯化腐植酸(PHA)在不同水平氮胁迫下对黄瓜植株生长和氮代谢的影响,探明PHA对逆境胁迫的缓解作用机制,采用水培方式,选用新泰密刺为供试品种,以正常氮水平(11 mmol·L^-1 NO₃^-)为对照,进行低氮(1.0 mmol·L^-1 NO₃^-)和高氮(101 mmol·L^-1 NO₃^-)胁迫处理,研究纯化腐植酸对氮胁迫下黄瓜幼苗生长和氮代谢的影响.结果表明: 低氮和高氮胁迫均抑制了黄瓜幼苗生长,株高、茎粗、叶面积、干物质积累量均低于正常氮水平处理.施用纯化腐植酸促进了正常氮水平及低氮胁迫下黄瓜干物质积累,在高氮胁迫下差异不显著.PHA影响了黄瓜幼苗NO₃^-的吸收,呈低氮下促进、高氮下抑制吸收的趋势;PHA显著降低了低氮、高氮胁迫下根系和叶片中的铵态氮含量;与正常氮水平相比,低氮、高氮胁迫下根系和叶片的硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、谷氨酸脱氢酶(GDH)活性及根系中亚硝酸还原酶(NiR)活性均显著降低,PHA不同程度地提高了NR、NiR、GS、GOGAT、GDH活性,还提高了根系和叶片中游离氨基酸、可溶性蛋白的含量.综上,添加PHA缓解了氮胁迫对黄瓜幼苗生长的抑制作用.     

外源Spd对盐碱胁迫下番茄幼苗氮代谢及主要矿质元素含量的影响

采用水培方法,研究了盐碱与Spd处理对两品种番茄（中杂9号和金棚朝冠）幼苗氮代谢及主要矿质元素含量的影响.结果表明： 盐碱胁迫下,番茄幼苗干生物量显著减少,植株生长受到抑制;叶片和根系硝酸还原酶（NR）、谷氨酰胺合成酶（GS）、谷氨酸合成酶（GOGAT）活性及硝态氮（NO₃^--N）、全N、全K、Ca²⁺、Mg²⁺含量显著降低,铵态氮（NH₄⁺-N）、Na⁺含量显著增加;两品种叶片及中杂9号根系谷氨酸脱氢酶（GDH）活性显著升高,金棚朝冠根系GDH活性变化不显著;叶片全P含量显著降低,根系全P含量显著升高（金棚朝冠）或无显著变化（中杂9号）.Spd处理通过增强NR、GS、GOGAT活性提高了植株对NH₄⁺的同化利用率,有效缓解了盐碱胁迫导致的氮代谢紊乱,进而促进不同器官对P、K、Ca、Mg、Na的吸收、释放或转运,在一定程度上维持了各元素之间的相对平衡,从而增强植株对逆境的适应能力.此外,盐碱对中杂9号的抑制作用及外源Spd对其氮代谢紊乱和营养失衡的缓解作用高于金棚朝冠.     

外源γ-氨基丁酸（GABA）对低氧胁迫下甜瓜幼苗根系GABA代谢及氨基酸含量的影响

采用水培法,通过准确控制营养液溶氧浓度,研究了外源γ-氨基丁酸（GABA）对低氧胁迫0~8 d ‘西域一号’甜瓜幼苗根系GABA代谢及氨基酸含量的影响.结果表明：与通气对照相比,低氧处理的甜瓜幼苗正常生长受到严重抑制,其根系谷氨酸脱羧酶（GAD）、谷氨酸脱氢酶（GDH）、谷氨酸合成酶（GOGAT）、谷氨酰胺合成酶（GS）、丙氨酸氨基转移酶（ALT）、天门冬氨酸氨基转移酶（AST）活性以及GABA、丙酮酸、丙氨酸、天冬氨酸含量均显著提高,而谷氨酸和α 酮戊二酸含量在处理4~8 d均显著降低.与低氧处理相比,外源GABA处理有效缓解了低氧胁迫对幼苗根系生长的抑制作用,同时甜瓜根系内源GABA、谷氨酸、α-酮戊二酸、天冬氨酸含量显著提高,但GAD、GDH、GOGAT、GS、ALT、AST活性在整个处理过程中均显著降低,丙酮酸和丙氨酸含量也显著降低.低氧同时添加GABA和γ-乙烯基 γ-氨基丁酸（VGB）处理显著降低了低氧胁迫下GABA的缓解效应.低氧胁迫下外源GABA被植物根系吸收后,通过反馈抑制GAD活性维持较高的Glu含量,保持植物体内碳、氮代谢平衡,维持正常生理代谢,从而缓解低氧胁迫对甜瓜幼苗的伤害.     

褪黑素对高温胁迫下黄瓜幼苗抗坏血酸代谢系统的影响

以‘津春4号’黄瓜幼苗为试材,采用叶面喷施的方法,研究了外源褪黑素对高温胁迫下黄瓜幼苗叶片抗坏血酸代谢系统的影响.结果表明:高温胁迫后,黄瓜幼苗叶片过氧化氢(H2O2)和丙二醛(MDA)含量明显增加;还原型抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量持续下降,脱氢抗坏血酸(DHA)和氧化型谷胱甘肽(GSSG)含量逐渐升高,AsA/DHA和GSH/GSSG大幅下降;抗坏血酸过氧化物酶(APx)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性明显升高,并在12 h达到最大.外施褪黑素能有效抑制高温胁迫下黄瓜幼苗叶片H2O2和MDA的积累,提高抗氧化物质AsA和GSH含量及抗坏血酸代谢相关酶APx、MDHAR、DHAR和GR活性,从而增强对H2O2的清除能力,抑制活性氧的产生,维持细胞膜的稳定性,减轻高温对植株造成的伤害,提高黄瓜幼苗抵御高温胁迫的能力.     

叶施NO对NaCl胁迫下红砂幼苗叶片和根系中氮代谢酶及营养物质的影响

以当年生红砂(Reaumuria soongorica)幼苗为材料,采用盆栽实验,考察叶面喷施不同浓度(0、0.01、0.10、0.25、0.50、1.00 mmol·L^-1)NO供体硝普钠 (SNP) 对NaCl(300 mmol·L^-1)胁迫下红砂根、叶中可溶性蛋白、游离氨基酸和硝态氮含量,以及谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、硝酸还原酶(NR)活性的影响,并采用主成分分析和隶属函数法筛选NO对NaCl胁迫缓解效应的氮代谢指标和最佳NO浓度,以探讨外源NO对NaCl 胁迫下红砂缓解效应的氮代谢响应机制。结果表明：(1)在300 mmol·L^-1 NaCl胁迫处理下,红砂幼苗根、叶中可溶性蛋白、硝态氮含量以及GS、GOGAT、NR活性均比对照显著下降。(2)外源NO能显著提高盐胁迫下红砂叶、根中GS、GOGAT、NR活性和硝态氮含量,增加根中可溶性蛋白和游离氨基酸含量。(3)NR和GOGAT活性可用于评价NO对NaCl胁迫下红砂幼苗的缓解作用,外源NO(SNP)对红砂幼苗在NaCl胁迫下的缓解效果强弱表现为0.25 mmol·L^-1> 0.50 mmol·L^-1> 0.10 mmol·L^-1> 1.00 mmol·L^-1> 0.01 mmol·L^-1。研究发现,300 mmol·L^-1 NaCl胁迫显著抑制了红砂幼苗氮代谢,外源NO(SNP)有助于提高盐胁迫下红砂NR活性,加快硝态氮转化为铵态氮,促进红砂叶片和根中GS/GOGAT对转化物的同化,从而增强红砂幼苗的耐盐性,并以0.25 mmol·L^-1SNP处理时缓解作用最佳;NR和GOGAT活性可作为NO缓解盐胁迫的评价指标。     

外源Spd对盐碱胁迫下番茄幼苗氮代谢及主要矿质元素含量的影响

采用水培方法,研究了盐碱与Spd处理对两品种番茄(中杂9号和金棚朝冠)幼苗氮代谢及主要矿质元素含量的影响.结果表明:盐碱胁迫下,番茄幼苗干生物量显著减少,植株生长受到抑制;叶片和根系硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)活性及硝态氮(NO3--N)、全N、全K、Ca2+、Mg2+含量显著降低,铵态氮(NH4+-N)、Na+含量显著增加;两品种叶片及中杂9号根系谷氨酸脱氢酶(GDH)活性显著升高,金棚朝冠根系GDH活性变化不显著;叶片全P含量显著降低,根系全P含量显著升高(金棚朝冠)或无显著变化(中杂9号).Spd处理通过增强NR、GS、GOGAT活性提高了植株对NH4+的同化利用率,有效缓解了盐碱胁迫导致的氮代谢紊乱,进而促进不同器官对P、K、Ca、Mg、Na的吸收、释放或转运,在一定程度上维持了各元素之间的相对平衡,从而增强植株对逆境的适应能力.此外,盐碱对中杂9号的抑制作用及外源Spd对其氮代谢紊乱和营养失衡的缓解作用高于金棚朝冠.     

不同烤烟品种衰老叶片的无机氮积累及其生理调控

以不同烤烟品种‘红花大金元’和‘中烟100’为试验对象,研究同一生育期不同部位叶片的无机氮积累及其与氮素代谢和氨挥发的关系。结果表明,烟草植株下部衰老叶片（第5片叶）NO3^-和NH4^＋的含量要高于中部叶（第10和第15片叶）和上部叶（第20片叶）,并且‘红花大金元’下部叶NO3^-和NH4^＋的含量比‘中烟100’显著偏高;‘中烟100’植株各部位叶片的氨气补偿点比‘红花大金元’高。两个品种在第5到第20叶位间的谷氨酰胺合成酶（GS）、硝酸还原酶（NR）和谷氨酸脱氢酶（GDH）活性大小及其变化不一致,是叶片无机氮积累存在品种间差异的生理基础。     

Response of Ammonia Assimilation in Cucumber Seedlings to Nitrate Stress

The influence of increased nitrate concentration—14 (control) and 140 mmol L⁻¹ (T)—in hydroponic culture on ammonia assimilation in cucumber (Cucumis sativus L. cv. Xintaimici) seedlings was investigated. The results showed that NH₃ accumulation in the roots and leaves of T seedlings increased significantly, indicating that NH₃ toxicity might be involved in nitrate stress. Under control conditions, GS and GOGAT activity were much higher in the leaves than in the roots, whereas GDH activity was much higher in the roots than in the leaves. Correlation analysis showed that NH₃ concentration had a strong negative linear relationship with GDH activity in the roots but had a strong negative linear relationship with GS and GOGAT activity in the leaves. These results indicate that NH₃ might be assimilated primarily via GDH reaction in the roots and via GS/GOGAT cycle in the leaves. Short-term nitrate stress resulted in the increase of GS and GOGAT activity in the roots and GDH activity in the leaves of T seedlings, indicating possible shifts in ammonia assimilation from the normal GDH pathway to GS/GOGAT pathway in the roots and from the normal GS/GOGAT pathway to the GDH pathway in the leaves under nitrate stress, but with the increase of treatment time, GS, GOGAT, and GDH activity in the roots and leaves of T seedlings decreased possibly due to low water potential and NH₃ toxicity.     

Bottle gourd rootstock-grafting affects nitrogen metabolism in NaCl-stressed watermelon leaves and enhances short-term salt tolerance

The plant growth, nitrogen absorption, and assimilation in watermelon (Citrullus lanatus [Thunb.] Mansf.) were investigated in self-grafted and grafted seedlings using the salt-tolerant bottle gourd rootstock Chaofeng Kangshengwang (Lagenaria siceraria Standl.) exposed to 100 mM NaCl for 3 d. The biomass and NO₃⁻ uptake rate were significantly increased by rootstock while these values were remarkably decreased by salt stress. However, compared with self-grafted plants, rootstock-grafted plants showed higher salt tolerance with higher biomass and NO₃⁻ uptake rate under salt stress. Salinity induced strong accumulation of nitrate, ammonium and protein contents and a significant decrease of nitrogen content and the activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT) in leaves of self-grafted seedlings. In contrast, salt stress caused a remarkable decrease in nitrate content and the activities of GS and GOGAT, and a significant increase of ammonium, protein, and nitrogen contents and NR activity, in leaves of rootstock-grafted seedlings. Compared with that of self-grafted seedlings, the ammonium content in leaves of rootstock-grafted seedlings was much lower under salt stress. Glutamate dehydrogenase (GDH) activity was notably enhanced in leaves of rootstock-grafted seedlings, whereas it was significantly inhibited in leaves of self-grafted seedlings, under salinity stress. Three GDH isozymes were isolated by native gel electrophoresis and their expressions were greatly enhanced in leaves of rootstock-grafted seedlings than those of self-grafted seedlings under both normal and salt-stress conditions. These results indicated that the salt tolerance of rootstock-grafted seedlings might (be enhanced) owing to the higher nitrogen absorption and the higher activities of enzymes for nitrogen assimilation induced by the rootstock. Furthermore, the detoxification of ammonium by GDH when the GS/GOGAT pathway was inhibited under salt stress might play an important role in the release of salt stress in rootstock-grafted seedlings.     

不同生育期花生叶片蛋白质含量及氮代谢相关酶活性分析

以5个珍珠豆型花生(Arachis hypogaea Linn.)品种(系)‘汕E’(‘Shan E’)、‘汕G’(‘Shan G’)、‘TH’、‘TJ’和‘泉花7号’(‘Quanhua No.7’)为研究对象,分析了花针期、结荚期和饱果期花生叶片中可溶性蛋白质含量及硝酸还原酶(NR)、谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH)活性的变化趋势,并比较了5个品种(系)荚果和秆产量的差异。结果表明:在3个生育期内,5个花生品种(系)叶片可溶性蛋白质含量和GDH活性的变化趋势基本一致,而NR和GS活性的变化趋势则有差异。其中,可溶性蛋白质含量均呈"低—高—低"的变化趋势,在结荚期最高;GDH活性均逐渐升高,至饱果期达最高;‘泉花7号’叶片NR活性呈"高—低—高"的变化趋势,而其他4个品种(系)叶片NR活性均逐渐降低;‘汕E’、‘TJ’和‘泉花7号’叶片GS活性呈逐渐降低趋势,而‘汕G’和‘TH’叶片GS活性呈"低—高—低"的变化趋势。总体上看,5个品种(系)中,‘汕G’和‘泉花7号’叶片的可溶性蛋白质含量及NR和GDH活性、‘汕E’叶片的NR和GS活性以及‘TH’叶片的GDH活性均较高。5个品种(系)的2个产量指标(单株荚果鲜质量和单株秆鲜质量)均有明显差异,总体上看,‘汕G’、‘泉花7号’和‘TH’的2个产量指标均较高,而‘汕E’和‘TJ’的2个产量指标均较低。综合分析结果显示:‘汕G’和‘泉花7号’叶片可溶性蛋白质含量及NR和GDH活性均相对较高,其荚果和秆产量也均较高,表明花生荚果和秆产量与不同生育期叶片氮代谢水平有一定关系。     

NaCl对水稻谷氨酸合酶和谷氨酸脱氢酶的胁迫作用

在ＮａＣｌ的胁迫下,水稻幼苗根和叶的谷氨酸合酶和谷氨酸脱氢酶的活性随着营养液中的ＮａＣｌ浓度的升高而降低;游离ＮＨ４＾＋在叶中积累,在根中未见明显变化。与根相比,叶对ＮａＣｌ的胁迫作用更为敏感。叶的ＮＡＤＨ－ＧＯＧＡＴ和ＮＡＤＨ－ＧＤＨ活性在ＮａＣｌ胁迫降低的程度明显大于根。无论是否有ＮａＣｌ存在,根的ＮＡＤＨ－ＧＤＨ活性明显高于叶。ＧＳ／ＧＤＨ比值分析提示,对对照下,根中的ＮＨ４＾存在,根的ＮＡ     

Effect of applied nitrate on enzymes of ammonia assimilation in nodules ofCicer arietinum L.

Summary The relationship between N₂-fixation, nitrate reductase and various enzymes of ammonia assimilation was studied in the nodules and leaves ofC. arietinum. In the nodules of the plants growing on atmospheric nitrogen, maximum activities of glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), asparagine synthetase (AS) and aspartate aminotransferase (AAT) were recorded just prior to maximum activity of nitrogenase. In nitrate fed plants, the first major peak of GDH and AS coincided with that of nitrate reductase in the nodules. With the exception of AS, application of nitrate decreased the activities of all these enzymes in nodules but not in leaves. Activities of GS, GOGAT and AAT were affected to much greater extent than that of GDH. On comparing the plants grown without nitrate and those with nitrate, the ratios of the activities of GDH/GS and GDH/GOGAT in nitrate given plants, increased by 4 and 12 fold, respectively. The results presented in this paper suggest that in nodules of nitrate fed plants, assimilation of ammonia via GDH assumes much greater importance.     

Biochar improved nodulation and nitrogen metabolism of soybean under salt stress

To investigate salt stress and biochar application effects on nodulation and nitrogen metabolism of soybeans (Glycine max cv. M7), an experiment was conducted under the control condition. The treatments comprised three biochar rates (non, 50 and 100 g kg^?1 soil) and three salinities (0, 5 and 10 dS m^?1 NaCl), with four replications of treatments. Salt stress diminished the number of nodules and their weights in the soybean roots. Nitrogen content and metabolism decreased in nodules, roots and shoots, while reducing the activity of glutamate dehydrogenase (GDH), glutamine synthetase (GS), glutamine oxoglutarate aminotransferase (GOGAT) and nitrate reductase (NR). Also, salinity brought down root and shoot weight, total plant biomass, chlorophyll content, leaf area (LA) and rubisco activity in the soybean. On the other hand, application of biochar improved nodulation, nitrogen content, rubisco activity, GDH, GS, GOGAT and NR activities in different parts of the soybean and nodules under salt stress, and consequently improved chlorophyll content, LA, root and shoot weight. Both the 50 and 100 g kg^?1 biochar rates showed similar effects in improving nitrogen metabolism and plant performance under salt stress. Generally, biochar increased nodulation and nitrogen metabolism of the soybean under saline conditions.