氯化钠影响下蓝藻Anabaena 7120的固氮活性和去铵阻抑

正常培养液中NaCl浓度增高时,蓝藻固氮活性明显下降,去铵阻抑速率也减慢。NaCl浓度越高,阻抑程度越大。如果NaCl浓度过高,固氮酶活性即完全丧失,铵阻抑效应也不能消除。低光照度、光合抑制剂、O_2、N_2以及N_2+CO_2都加剧高浓度NaCl对蓝藻固氮酶活性和去铵阻抑的阻抑,而外源蔗糖、H_2和H_2+O_2则有一定程度的促进。     

蓝藻Anabaena 7120固氮酶活性表达和生理条件的关系

经暗处理24小时的蓝藻转到光下后,开始一段时间不表达固氮酶活性,嗣后出现活性,并随光照时间延长而增高;加蔗糖促进固氮酶活性的表达,但比预光下培养的蓝藻低.厌氧(氩和氮气中)、氧、光合抑制剂和MSX都延缓暗处理蓝藻固氮酶活性的表达,加蔗糖后固氮活性提前表达,并且活性有所提高。分子氢对暗处理蓝藻固氮酶活性及其表达有促进作用,而对光预处理蓝藻则未表现促进作用。氢和氧同时加入或加蔗糖,对光预处理蓝藻固氮酶活性的表达均有明显的促进作用。     

固氮粪产碱菌ntrC基因的表达及固氮调节功能研究

采用双亲结合方法，将粪产碱菌Ａ１１５０ｌｎｔｒＣ和ｎｔｒＣ－ｌａｃＺ融合基因转入Ａ１５０１中，获得携带双拷贝ｎｔｒＣ的结合子Ａ１５０１（ｐＬＡＣ１）和ｎｔｒＣ－ｌａｃＺ融合基因的结合子Ａ１５０１（ｐＬＡＣ２）。在微好氧条件下，当铵为６ｍｍｏｌ时结合子Ａ１５０１（ｐＬＡＣ１）仍保持３４．８％的固氮活性，表明在粪产碱菌中ｎｔｒＣ具有固氮正调节功能。在不同铵、氧、ｐＨ和盐浓度等条件下测定结合子Ａ１５０１     

nifH—lacZ融合基因在粪产碱菌中及联合固氮条件下的表达调节

将巴西固氮螺菌ｎｉｆＨ－ｌａｃＺ转入粪产碱菌Ａ１５０１中，β－Ｇａｌａｃｔｏｓｉｄａｓｅ活性测定结果表明，该转录型融合基因ｎｉｆＨ－ｌａｃＺ在Ａ１５０１中的表达为诱导型的，在固氮条件下高水平表达，在高铵好氧下低水平表达，在无铵好氧下部分表达。Ｓｏｕｔｈｅｒｎ杂交分析证明在粪产碱菌中存在ｎｉｆＡ、ｒｐｏＮ和ｎｔｒＣ基因的同源序列，表明粪产碱菌ｎｉｆＨＤＫ的转录启始可能为ＮｉｆＡ和α＾５４依赖型的。携     

渗透胁迫下的蓝藻固氮作用

渗透胁迫下,蓝菏的固氮活性下降,去铵阻抑速率减小,下降程度随渗透胁迫的增高而增大,光合使用受抑Ｏ２和Ｎ２分压增高均加剧渗透胁迫对固氮酶活性的抑制。添加外源蒸糖,供应ＣＯ２,同时供应ＣＯ２和Ｎ２或Ｈ２和Ｏ２时,渗透胁迫对固氮酶活性的抑制程度明显减弱。     

短时间高温对蓝藻Anabaena 7120固氮酶活性的影响

蓝藻Anabaena 7120经短时间高温处理后,其固氮酶活性、吸氢和放氧活性均下降,固氮酶活性对氧和pH变化的敏感性增大,受分子氢支持和一氧化碳抑制的程度增高。光合抑制剂或弱光加剧短时间高温处理对蓝藻固氮酶活性的抑制程度。     

联合固氮遗传工程菌的田间释放与风险评价

应用遗传工程技术分别将含有ｎｉｆＡ＾ｃＤＮＡ片段的质粒及含有Ｔｎ５：：ｎｉｆＡ的广泛宿主自杀性质粒ｐＳＺ３６转入了三个联合固氮菌，即粪产碱菌，阴沟肠杆菌及催娩克氏菌中；把Ｔｎ５：：ｎｉｆＡ－ｎｔｒＣ转入了粪产碱菌野生型菌株Ａ１５０１。这些转化结合子在高铵下表现出固氮活性，并能集聚在水稻根表，而野生型菌在相同条件下远离水稻根表。这些菌株的田间释放实验在严格控制条件下进行，应用＾１５Ｎ稀释技术测定其固     

山西省玉米根际固氮特性研究

玉米根际固氮活性随品种和生态条件的不同而变化，在山西土壤气候条件下，测试品种中有９１．７％具有固氮活性，变异系数为６２．８％，固氮高出现在抽雄期，大约每公顷年固氮量８．１ｋｇ。在一定条件下，秸秆覆盖栽培，增施有机肥、磷肥、少量氮肥以及人工接种均有利于提高玉米根际的固氮作用。     

固氮蓝藻的农业应用研究进展

作为可固氮固碳的自养光合微生物,固氮蓝藻是一种非常重要的微生物资源。关于固氮蓝藻在农业生产上的应用始于1939年印度首次报道用固氮蓝藻肥田,之后一段时期虽然受到国际广泛关注,但最终并未实现规模化推广应用。究其原因既与化肥在世界范围内的大规模使用有关,也与自身技术相对复杂、成本高和可靠性低有关。对于前者虽然化肥的农业增产作用巨大,但其对农业自身和生态环境的负面影响日益凸显。而对于后者,新的固氮蓝藻规模化生产技术和新的接种技术的发展正在逐步消除这些缺陷。在当前国家要求农业"减量化"和"低碳化"发展的背景下,固氮蓝藻作为生态环保的生物肥料可能迎来新的发展契机。同时,除了作为生物肥料,近年来国内外的研究表明固氮蓝藻具有多重农业应用价值,可能在作物生长调节剂和生物农药开发、农业环境污染防治和农业生态环境保护等方面发挥作用。因此,本文就国内外近5年(2013—2017年)关于固氮蓝藻的农业应用进展进行了全面综述,并就存在的问题和今后的发展方向做了展望。今后固氮蓝藻作物生长调节方面需深入研究藻激素的代谢和调控机制,藻接种技术方面需深入研究生物膜中藻类和其他微生物的互作关系,抗病虫害方面需要进行更多的田间试验以评估其实际应用效果并阐明抗性机制,降解有机农药方面需深入研究降解关键酶、降解途径和大田应用技术,生态环境保护方面需评估固氮蓝藻抗旱抗盐碱实际应用效果并阐明其机理。     

分子氢对红萍固氮活性的支持作用(英文)

本工作研究了分子氢对不同生长条件下三种红萍:细绿萍(Azollsa filiculoides),卡洲萍(Azolla caroniana)和小叶萍(Azolla microphylla)的固氮活性的支持作用,结果表明,在5000—20000lx不同光照强度下,分子氢对红萍固氮活性均有支持作用,当光照强度为10000lx时,10％的分子H_2可使红萍的固氮活性增加30—80％,在5000lx弱光条件下,相同浓度分子氢使红萍固氮活性增加的幅度比10000lx光照时大。在相同的光照条件下,大叶萍的固氮活性较高,分子氢对其固氮活性的支持作用也较强,说明了在萍藻共生体系中,光能利用、固氮效率与分子氢利用效率呈正相关。同时,分子氢对于红萍固氮活性受尿素毒害所致的抑制也有减慢作用。在培养液中尿素浓度超过5ppm时,红萍的固氮活性受到抑制,当尿素浓度达到50ppm时,其固氮活性抑制率达50—60％,但20％的分子氢可使其固氮活性恢复到正常培养下的70％以上。在一定的尿素浓度范围内,红萍固氮活性受抑程度愈大,分子氢对其减慢的作用也愈强。     

Arbuscular mycorrhizae affect the N and C economy of nodulated Phaseolus vulgaris (L.) during NH4 nutrition

In the symbiosis between nodulated legume roots and arbuscular mycorrhizal (AM) fungi, the C and N economy can be influenced by the source of N-supply from either AM-derived NH₄⁺ uptake or nodule-derived biological nitrogen fixation (BNF). This relationship was investigated in terms of NH₄⁺ supply and BNF by the two symbionts. Nodulated Phaseolus vulgaris seedlings with and without AM, were hydroponically grown with either 0 N or 1 mM NH₄⁺ supply. Plants were harvested at 30 days after emergence and measurements were taken for biomass, N₂ fixation, photosynthesis, CO₂ and O₂ root respiration, calculated C and N economy. AM roots had higher NH₄⁺ uptake and this was associated with the suppression of BNF and nodule growth. The higher NH₄⁺ uptake in AM roots occurred with lower root maintenance respiration, compared to when N was derived from BNF. There was also an increase in the below-ground sink strength of NH₄⁺ fed AM roots compared to NH₄⁺ fed non-AM roots, as evidenced by the increases in root CO₂ and O₂ respiration and photosynthetic stimulation. These results indicate that although the AM root had higher total below-ground respiratory costs during NH₄⁺ nutrition, there were lower respiratory C costs associated with N derived from AM symbionts in comparison to N from BNF.     

聚天门冬氨酸钙盐对水稻田面水中三氮动态变化的影响

利用桶栽试验探究不同浓度水平的聚天门冬氨酸钙盐(PASP-Ca)对水稻田面水中铵态氮(NH_4~+)、硝态氮(NO_3~-)和总氮(TN)浓度动态变化的影响。结果表明,施氮后,田面水中TN、NH_4~+和NO_3~-分别于第1,3,9天达到最大值,随后逐渐降低。NO_3~-/TN多在0.1以下,(NH_4~++NO_3~-)/TN多在0.5以上。因此,可以将NH_4~+和TN作为农田水污染防治的主要监测指标,NO_3~-作为辅助指标。添加一定浓度的PASP—Ca能对田面水中氮素浓度的变化起到缓释作用,其中0.3%浓度水平的PASP—Ca效果相对较好,田面水中NH_4~+和TN的下降速率分别为3.452,4.806mg/(L·d),与单施氮肥(CK)相比,分别降低了11.68%和16.25%;同时,NH_4~+的平均浓度为6.999mg/L,较CK低了3.88%;NO_3~-的平均浓度为0.396mg/L,较CK低了24.83%;TN的平均浓度为20.077mg/L,较CK提升了3.10%。施氮后田面水中TN浓度随时间呈对数递减,而NH_4~+浓度在施氮后3天内随时间呈对数增加,之后随时间呈对数递减趋势。施氮后的9天内是防止稻田田面水中氮素流失的关键时期。     

不同铵硝配比对弱光下白菜氮素吸收及相关酶的影响

以黑色遮阳网覆盖模仿弱光环境, 使光照强度为自然光的20%左右, 以自然光照为对照, 采用精确控制水培溶液氮素营养, 研究NH₄⁺-N/NO₃^--N 比例分别为0/100、25/75、50/50、75/25、100/0 对弱光下白菜氮代谢及硝酸还原酶和谷氨酰胺合成酶活性的影响。结果表明, 弱光下, 白菜的鲜重及叶片总氮量以NH₄⁺-N/NO₃^--N 比为25/75 时最大, NH₄⁺-N/NO₃^--N 比为100/0 时最低。随弱光处理的进行, 白菜叶片中硝酸还原酶活性及谷氨酰胺合成酶活性均呈下降趋势, 但NH₄⁺-N/NO₃^--N 比为25/75 时, 可维持叶片内较高的硝酸还原酶活性及谷氨酰胺合成酶活性。试验表明, NH₄⁺-N/NO₃^--N 比25/75 是白菜在弱光下生长的较适宜氮素形态配比。     

陕西省几种代表性土壤NH4+吸附、解吸动力学特征研究

采用连续液流法测定了五种土壤吸附、解吸ＮＨ＾＋４的动力学性质。研究表明：（１）ＮＨ＾＋４吸附、解吸平衡时间及反应速率，平衡时的吸附、解吸量及吸附平衡常数均随土壤粘粒和ＣＥＣ不同而变化；（２）不同动力学模型及同一模型对不同土壤的拟合性不同。     

不同铵态氮水平对水稻根际固氮活性的影响

本试验观察了在杭州生态条件下土壤中不同NH₄⁺-N水平对水稻根际固氮活性的影响。试验的结果表明:1.NH₄⁺-N肥在一定时间内对水稻根际固氮活性具有明显的抑制效应,施用量越大,其抑制作用越严重。土壤速效氮浓度与水稻根际固氮活性之间呈高度(或中度)负相关,不同生育期两者的相关系数r值在-0.4288—0.9945之间。2.土壤速效氮对水稻土柱固氮活性抑制的起始浓度为20ppm。3.NH₄⁺-N对水稻根际固氮活性的抑制时间随施用量而不同,低氮区在20天左右,中氮区和高氮区在25—30天左右。此后施氮区对水稻根际固氮活性具有促进作用。     

不同铵钾比对高铵下拟南芥地上部和根系生长的影响

钾在缓解植物铵毒害的过程中起着重要的作用。本文研究了高铵(30 mmol/L)条件下,不同铵钾比(7.5︰1和150︰1)对拟南芥(Col-0)主根、侧根以及地上部生长的影响。结果表明:30 mmol/L NH4+条件下,高铵钾比(150)处理显著加重了拟南芥铵毒害现象,地上部和根系生长所受的抑制作用更为明显并导致更严重的氧化胁迫。相比低铵钾比水平,在高铵处理下,高铵钾比使得拟南芥主根伸长量降低57.4%,侧根数量减少33.3%,而地上部鲜重减轻69.9%。DAB(3,3￠-二氨基联苯胺,3,3￠-diaminobenzidine)叶片染色结果表明,不加铵处理下,外源不同钾水平(0.2和4.0 mmol/L)对拟南芥叶片的氧化胁迫作用没有显著差异;而高铵处理下,相比低铵钾比处理,高铵钾比显著增加了叶片中过氧化氢的含量,加重了其氧化胁迫。伊文思蓝(Evans blue,EB)染色结果表明,不加铵处理下,外源不同钾水平对拟南芥地上部和根部的膜透性没有显著差异,而高铵处理下,高铵钾比显著增强了拟南芥地上部和根部的膜透性,表明其对细胞的伤害程度加重。可见,高铵抑制拟南芥根系和地上部生长,高铵钾比则会加重这种抑制,其原因除了高浓度钾能减少植物对铵的吸收外,可能与高铵钾比条件加剧了植物的氧化胁迫有关。因此,适宜的铵钾比在植物应对铵毒害的过程中发挥重要作用。     

Methionine sulfoximine suppressed the stimulation of dark carbon fixation by ammonium nutrition in wheat roots

To evaluate the role of NH₄ ⁺ assimilates in dark carbon fixation in roots in providing carbon skeletons expended for NH₄ ⁺ assimilation, the rate of dark carbon fixation in roots was measured using NaH¹⁴CO₃. The ¹⁴C-metabolites were analyzed in wheat (Triticum aestivum L.) plants grown in NH₄ ⁺ media for various periods of time with or without methionine sulfoximine (MSX) treatment. The dark carbon fixation rate in the roots of wheat plants that had been grown with NH₄ ⁺ for 1 d was approximately 6-fold higher than the rate in control roots. The stimulation of dark carbon fixation in NH₄ ⁺-grown plants, however, was not observed in MSX-treated roots. In the roots of NH₄ ⁺-grown plants, the concentration and ¹⁴C-Iabeling of acidic metabolites such as citrate and malate considerably decreased whereas those of basic metabolites, especially asparagine, increased noticeably. With MSX treatment, the incorporation of ¹⁴C into basic metabolites was negligible. In response to NH₄ ⁺, phosphoenolpyruvate carboxylase (PEPC) activity increased, and PEPC proteins accumulated in wheat roots. Neither activity nor amounts of PEPC in roots increased in the presence of MSX. These findings suggest that primary assimilation of NH₄ ⁺ in roots is essential for the stimulation of dark carbon fixation, which coincides with the increased activity of root PEPC, to sufficiently replenish carbon skeletons necessary for NH₄ ⁺ assimilation.     

Fixed ammonium and potassium release from two soils

Abstract

Release of native and added K⁺ and NH⁺ ₄ from two soils was monitored during a 166 day incubation/leaching experiment. One soil (Brookston) represented a major soil series In Ontario whereas the other (Harriston) was suspected having a relatively large fixation capacity. Treatments were imposed involving addition of 50 μM g^‐1 soil of K⁺(KCl) or NH⁺ ₄ (NH₄Cl) only or one added after the other on successive days. The addition of either K⁺ or NH⁺ ₄ on day 2 tended to inhibit the release of the other added on day I. Also the addition of either K⁺ or NH⁺ ₄ on day 1 tended to inhibit the sorption or fixation of the other on day 2. The release rate of K⁺ during the 10 to 166 day period was almost constant and not affected by the addition of NH⁺ ₄. Alternatively, the addition of K⁺ on day 2 slowed the release rate of NH⁺ ₄ measured by NO^? ₃ appearance from day 10 to 40 but had no effect thereafter. At the end of the experiment considerably more K⁺ than NH⁺ ₄ was retained suggesting that K⁺ was more firmly fixed. However, the continuing nitrification of NH⁺ ₄ must be contrasted with periodic removal of K⁺ by leaching with 0.01 M CaCl₂ solution since the equilibrium between exchangeable and fixed ions was affected. There were no notable differences between the two soils inspite of a considerable difference in clay content.     

宁夏引黄灌区稻田氮素浓度变化与迁移特征

过量施氮与不合理灌水是农田面源污染加剧的主要原因。为了寻求较优的水氮管理模式以促进农业生产和减少农田退水对黄河水体的污染, 在宁夏引黄灌区典型稻田中开展了不同水氮条件下稻田氮素迁移转化规律研究。结果表明: 不同水氮条件下稻田田面水NH₄⁺-N 与NO₃^--N 浓度伴随施肥出现明显峰值, NO₃^--N 峰值出现时间较NH₄⁺-N 晚, 且变化较平缓。3 次追肥时期和整个生育期田面水NH₄⁺-N 平均浓度与施氮量和灌水量都呈显著相关, 田面水NO₃^--N 平均浓度与施氮量呈显著正相关, 与灌水量相关性不显著。稻田30 cm与60 cm 深度的直渗水NH₄⁺-N 浓度受施肥影响较大, 与田面水NH₄⁺-N 浓度变化规律相似, 90 cm 处直渗水NH₄⁺-N 浓度峰值出现较为滞后, 且浓度较上层土体低, 120 cm 处直渗水NH₄⁺-N 浓度大体呈现持续上升趋势,整个生育期直渗水NH₄⁺-N 平均浓度与施氮量呈显著相关, 仅30 cm 处NH₄⁺-N 平均浓度与灌水量呈负相关, 其他土层深度不显著。30 cm 与60 cm 直渗水NO₃^--N 浓度在首次灌水后急剧下降, 在施肥后有较小幅度上升, 90 cm 与120 cm 直渗水NO₃^--N 浓度下降缓慢, 仅30 cm 处NO₃^--N 平均浓度与施肥量显著正相关。总的结果表明减少施肥或灌水均可达到减少农田氮素淋失的目的。     

铁铝氢氧化物对两种土壤和高岭石表面K+和NH4+解吸的影响

Potassium (K) and nitrogen (N) are essential nutrients for plants. Adsorption and desorption in soils affect K+ and NH + 4 availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH + 4 from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides, as amorphous Al(OH) 3 or Fe(OH) 3 , and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K+ and NH + 4 declined as a result of the incorporation of the Fe/Al hydroxides. Consequently, the release of exchangeable K+ and NH +4 from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K+ and NH + 4 . A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K+ and NH + 4 were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH + 4 in the soils and thus increase their leaching loss.