河北省豆科植物根瘤菌资源的初步调查研究

通过对河北省全镜豆科植物的结瘤和固氮状况进行调查,共采集到２４属５３种豆科植物的根瘤样品２３５份,９８．１％的被调查豆科植物可自然结瘤,９６．２％的自然瘤可测到固氮酶活性其中海边香豌豆、野百合、阴山胡枝子、山岩黄耆、辽西苜蓿的结瘤固氮情况为首次报道。     

河北省豆科植物根瘤菌资源的初步调查研究

通过对河北省全境豆科植物的结瘤和固氮状况进行调查 ,共采集到 2 4属 5 3种豆科植物的根瘤样品 2 3 5份 ,98.1的被调查豆科植物可自然结瘤 ,96.2的自然瘤可测到固氮酶活性 .其中海边香豌豆 (L athyrus maritimus)、野百合 (Crotalaria sessilif lora)、阴山胡枝子 (L athyrusinschanica)、山岩黄耆 (H edysarum alpinum)、辽西扁苜蓿 (Melilotus ruthenicus)的结瘤固氮情况为首次报道 .     

氮阻遏之谜

正近年来,我国科学家发现,豆科植物与禾本科植物间作,能促使豆科植物更多地结瘤固氮,获得双高产。这是为什么呢?科学家积极探究,终于解开了这个谜。中国农业大学植物营养系的老师们在甘肃进行的蚕豆(豆科植物)与玉米(禾本科植     

结瘤信号途径中相关调控蛋白的研究进展

以模式豆科植物与根瘤菌的共生固氮为视角,介绍近年来在结瘤信号途径中筛选到的能够与已知关键调控蛋白相互作用的新蛋白,综述了相关新蛋白在共生结瘤过程中发挥的重要作用,进一步补充和完善了结瘤早期信号转导途径,为豆科植物与根瘤菌共生关系的研究提供参考.     

豆科根瘤菌剂的生产及应用

豆科植物一生所需氮的1/2～2/3都来源于固氮菌从空气中固的氮,根瘤菌从豆科植物吸收养料,同时根瘤菌从空气中固氮提供给豆科植物,因此,土壤中有效根瘤数量是决定产量的重要因素,本文将阐述提供根瘤菌菌剂的生产和应用.     

氮阻遏之谜

近年来,我国科学家发现,豆科植物与禾本科植物间作,能促使豆科植物更多地结瘤固氮,获得双高产。这是为什么呢?科学家积极探究,终于解开了这个谜。中国农业大学植物营养系的老师们在甘肃进行的蚕豆(豆科植物)与玉米(禾本科植物)间作试验中发现,蚕豆间作的产量比单作产量提高63.7%,玉米间作的产量比单作产量提高17.3%,双双达到高产水平。     

福建共生固氮植物资源调查(三) 50种豆科绿肥或牧草的分布、生长性特、结瘤固氮及主要用途

豆科植物与根瘤菌的共生固氮在农业生产上具有重要意义,可以增加肥源、节约能源、改良土壤、保持水土、改善生态环境。我国的豆科植物资源丰富,种类繁多,据报道,在我国已发现的豆科植物约有160属1400种(杨民权,1983)。虽然,我国是世界上利用豆科绿肥最早的国家,而且栽培面积也很广(孙醒东,1958),但是,栽培利用的仅是豆科植物资     

细菌——植物叶际联合固氮研究进展

从生态学观点来看,自然界存在着三种生物固氨体系:自生固氮体系,如自生固氮菌在土壤中或培养基中独立生活时固定分子态氮;共生固氮体系,如根瘤菌和豆科植物共生时才能固定分子态氮,或者只在共生条件下才表现旺盛的固氮作用;联合固氮体系,是自生固氮体系与共生固氮体系的中间类型,固氮菌与相应联合的植物之间有较密切的相互影响,但既不同于典型的共生固氮体系,因为它不形成根瘤一样的特殊形态结构——根瘤,也不同於自生固氮体系,因为它有较大的寄主专一性,并且固氮作用比     

花生根瘤菌诱变株感染大豆结瘤和固氮

花生根瘤菌诱变株感染大豆结瘤和固氮龙敏南，许良树，张凤章，曾定（生物学系）根瘤菌在共生固氮过程中会放Ｈ２，放Ｈ２是种能量浪费．Ｅｖａｎｓ等［１］研究表明：利用具有吸氢酶活性的根瘤菌［ＨＵｐ＋］接种豆科作物能提高固氮效率、增加作物产量．豆科植物根瘤菌的...     

贵州省豆科结瘤固氮植物资源调查

通过对贵州省豆科植物结瘤固氮资源的调查,共采集根瘤标本242份,分属豆科植物42属103种及变种,其中蝶形花亚科、含羞草亚科、云实亚科植物的结瘤率分别为95%,75%和5%;采集的根瘤中,96%生于寄主的侧根,形状以球形、长柱形为主,颜色多为白色、褐色.对分离纯化的55株根瘤菌进行了回接试验,回接结瘤率为33%.生态条件是影响根瘤的大小、数量以及有效性的原因之一.     

Amino-acid cycling drives nitrogen fixation in the legume-Rhizobium symbiosis

The biological reduction of atmospheric N2 to ammonium (nitrogen fixation) provides about 65% of the biosphere's available nitrogen. Most of this ammonium is contributed by legume-rhizobia symbioses, which are initiated by the infection of legume hosts by bacteria (rhizobia), resulting in formation of root nodules. Within the nodules, rhizobia are found as bacteroids, which perform the nitrogen fixation: to do this, they obtain sources of carbon and energy from the plant, in the form of dicarboxylic acids. It has been thought that, in return, bacteroids simply provide the plant with ammonium. But here we show that a more complex amino-acid cycle is essential for symbiotic nitrogen fixation by Rhizobium in pea nodules. The plant provides amino acids to the bacteroids, enabling them to shut down their ammonium assimilation. In return, bacteroids act like plant organelles to cycle amino acids back to the plant for asparagine synthesis. The mutual dependence of this exchange prevents the symbiosis being dominated by the plant, and provides a selective pressure for the evolution of mutualism.     

Shoot control of root development and nodulation is mediated by a receptor-like kinase

In legumes, root nodule organogenesis is activated in response to morphogenic lipochitin oligosaccharides that are synthesized by bacteria, commonly known as rhizobia. Successful symbiotic interaction results in the formation of highly specialized organs called root nodules, which provide a unique environment for symbiotic nitrogen fixation. In wild-type plants the number of nodules is regulated by a signalling mechanism integrating environmental and developmental cues to arrest most rhizobial infections within the susceptible zone of the root. Furthermore, a feedback mechanism controls the temporal and spatial susceptibility to infection of the root system. This mechanism is referred to as autoregulation of nodulation, as earlier nodulation events inhibit nodulation of younger root tissues. Lotus japonicus plants homozygous for a mutation in the hypernodulation aberrant root (har1) locus escape this regulation and form an excessive number of nodules. Here we report the molecular cloning and expression analysis of the HAR1 gene and the pea orthologue, Pisum sativum, SYM29. HAR1 encodes a putative serine/threonine receptor kinase, which is required for shoot-controlled regulation of root growth, nodule number, and for nitrate sensitivity of symbiotic development.     

豆科植物-根瘤菌共生固氮的分子机理

与豆科植物－根瘤菌共生固氮有关的基因涉及根瘤菌基因和宿主基因，根瘤菌基因有结瘤基因（nodD,nodAB-CIJ和hsn基因），根瘤菌细胞表面结构基因（exs,lps和ndv基因）和固氮基因（nif和fix基因）；宿主基因主要是结瘤素基因（ENOD和NOD基因）。根瘤菌结瘤基因表达后诱导产生结瘤因子。在根瘤发育过程中，这些基因在根瘤菌与植物之间进行着信息交换，并且具有不同的表达水平。结瘤因子和植物激素对它们进行着调节。     

Specific degradation of photosystem II D1 protein by a protease （Air3815） in heterocysts of the cyanobacterium Anabaena sp. PCC7120

Some filamentous cyanobacteria form heterocysts under conditions lacking combined nitrogen for nitrogen fixation.Photosystem II is removed from heterocyst during the process of cell differentiation.Here,we demonstrate that Alr3815 is a protease that is capable of degrading D1 protein of photosystem II.Strain-322,which lacks alr3815,is impaired in nitrogen fixation in air because some oxygen evolving activity is retained in its heterocysts.Our results also suggest that calcium may play a regulatory role in D1 degradation during heterocyst differentiation.     

接种方式对花榈木幼苗结瘤效应的影响

【目的】探讨珍贵用材树种花榈木幼苗接种根瘤菌的有效方法。【方法】设计了浸种、浸根、拌种和浇灌4种接种方式进行盆栽试验,以不接根瘤菌的盆栽苗为对照,观察接种后幼苗根系形态、结瘤数量变化,并测定幼苗生长、生理生化指标及固氮相关指标。【结果】不同接种方式处理下花榈木幼苗根系松软、呈土黄色,幼瘤多呈球形、黄褐色,结瘤部位多位于侧须根系上。不同接种方式处理的花榈木幼苗结瘤数量和质量差异明显,浇灌处理的结瘤数量最多,鲜瘤生物量最大,结瘤率最高,其次是浸根处理。接种上根瘤的花榈木幼苗生长指标均大于CK,与CK相比,4种接种方式处理下的苗高、地径和总生物量增幅分别为11.48%～29.51%、3.21%～26.61%和36.30%～148.18%; 总根长、总根表面积、根平均直径、总根体积和根尖数增幅分别为70.62%～139.39%、74.70%～140.97%、164.28%～200.00%、75.00%～250.00%和28.03%～167.42%。不同接种方式处理的花榈木结瘤幼苗生理生化指标差异显著,浇灌处理的花榈木结瘤幼苗叶绿素含量、硝酸还原酶活性、硝态氮含量和根系活力都明显高于其他处理。接种上根瘤的花榈木幼苗叶片全氮、鲜瘤豆血红蛋白含量、总氮量以及固氮量明显高于CK,浇灌和浸根处理优于其他处理。【结论】花榈木根瘤接种的适宜方式为用萌发种子浸根和用菌液浇灌长出真叶后的幼苗。     

A possible nitrogen crisis for Archaean life due to reduced nitrogen fixation by lightning.

Nitrogen is an essential element for life and is often the limiting nutrient for terrestrial ecosystems. As most nitrogen is locked in the kinetically stable form, N2, in the Earth's atmosphere, processes that can fix N2 into biologically available forms-such as nitrate and ammonia-control the supply of nitrogen for organisms. On the early Earth, nitrogen is thought to have been fixed abiotically, as nitric oxide formed during lightning discharge. The advent of biological nitrogen fixation suggests that at some point the demand for fixed nitrogen exceeded the supply from abiotic sources, but the timing and causes of the onset of biological nitrogen fixation remain unclear. Here we report an experimental simulation of nitrogen fixation by lightning over a range of Hadean (4.5-3.8 Gyr ago) and Archaean (3.8-2.5 Gyr ago) atmospheric compositions, from predominantly carbon dioxide to predominantly dinitrogen (but always without oxygen). We infer that, as atmospheric CO2 decreased over the Archaean period, the production of nitric oxide from lightning discharge decreased by two orders of magnitude until about 2.2 Gyr. After this time, the rise in oxygen (or methane) concentrations probably initiated other abiotic sources of nitrogen. Although the temporary reduction in nitric oxide production may have lasted for only 100 Myr or less, this was potentially long enough to cause an ecological crisis that triggered the development of biological nitrogen fixation.     

稀土溶液浸种对花生生长过程的影响

适宜浓度的稀土溶液浸种能促进花生种子萌芽、出苗和植株生长;能使植株根系发达,主茎和分枝缩短,分枝数增多;提高叶片叶绿素含量和净光合速率,促进于物质积累;增加单株根瘤数、根瘤重和根瘤固氮活性.最终增加单株开花数、单株饱果数和荚果产量.     

共生固氮体系大豆种子氨基酸组分分析

对三对共生固氮体系大豆种子氨基酸组分的分析表明，大豆种子氨基酸组分没有因大豆作物产量的提高而下降，通过施用相应的根瘤菌促其形成或加强共生固氮体系从而提高大豆作物产量，这种增产从氨基酸水平分析是有效的。     

Buckminsterfullerenes: a non-metal system for nitrogen fixation

In all nitrogen-fixation processes known so far--including the industrial Haber-Bosch process, biological fixation by nitrogenase enzymes and previously described homogeneous synthetic systems--the direct transformation of the stable, inert dinitrogen molecule (N2) into ammonia (NH3) relies on the powerful redox properties of metals. Here we show that nitrogen fixation can also be achieved by using a non-metallic buckminsterfullerene (C60) molecule, in the form of a water-soluble C60:gamma-cyclodextrin (1:2) complex, and light under nitrogen at atmospheric pressure. This metal-free system efficiently fixes nitrogen under mild conditions by making use of the redox properties of the fullerene derivative.