杨梅根瘤的显微和亚显微结构及固氮活性

杨梅根瘤的横切面是圆形、对称的,含菌组织位于皮层的中部。未成熟根瘤的感染细胞充满内生菌丝。内生菌丝是分枝。具隔膜的Frankia菌。成熟根瘤中,内生菌丝顶端膨大形成无隔膜、表面光滑、球形的泡囊,直径比菌丝直径大,内含有某种内含物。泡囊的大量出现可能是固氮活力提高的标志,成熟壮瘤的固氮活性比幼瘤和衰老瘤的高。     

大叶相思的结瘤固氮和吸氢酶活性

本文报道大叶相思的结瘤固氮和氢酶活性的研究结果。大叶相思结瘤状况与其他含羞草亚科的树种相似,刚形成的幼瘤为单生球状或椭圆形,以后顶端伸长或分叉,呈分叉状、姜状和扇状。同一植株的不同成熟度根瘤的固氮活性也不同,成熟壮瘤固氮活性最高,幼瘤次之,衰老瘤最低。不同立地条件下种植的大叶相思根瘤固氮活性虽有差异,但生长在pH4.7的酸性红壤中的大叶相思,根瘤固氮活性仍具有较高水平。大叶相思根瘤固氮活性也有明显的季节变化,夏秋较高,春冬较低。根瘤离体后7小时内固氮活性变化不大,甚至在离体后21小时内仍维持一定水平的固氮活性。大叶相思根瘤具有吸氢酶,其吸H_2活性在最初3小时内随时间延长而升高,3—7小时内仍维持一定水平。在根瘤固氮系统中注入外源分子H_2,可提高固氮酶活性,外源H_2最适浓度为7.5％。由于其根瘤具有催化吸收分子H_2的氢酶系统,能吸收利用固氮反应所放出的大量H_2,因而能更有效地利用光合产物于固氮过程。大叶相思根瘤离体后能较长时间维持高的固氮活性水平,可能与其吸H_2酶系统有关。     

羊奶果结瘤固氮特性研究

羊奶果根瘤多年生,初发生时呈2—3分又状,后经多次分叉生长,形成珊瑚状的根瘤簇,外形球状或扁球状,直径可达数厘米。根瘤固氮活性较高,全年平均固氮活性8.86微摩乙烯/克鲜瘤/小时。固氮活性秋夏较高,冬春较低。根瘤离体后固氮能力持续时间较长,可达9小时。固氮作用最适温度为30℃,低温使固氮活性显著下降,短时间高温(37℃)能提高根瘤固氮活性,但持续高温会抑制固氮活性。 羊奶果根瘤具有氢酶,表现出较高吸氢活性(9.52微摩氢/克鲜瘤/小时),且持续时间较长。外源氢能明显提高根瘤固氮活性,提高幅度达60％左右。 羊奶果各器官硝酸还原酶活力为根>根瘤>叶片>枝条,叶片NR活力呈季节性变化,秋夏较高,冬春较低。根瘤NR活力变化较大,且与根瘤固氮活性变化的趋势基本一致。     

与某些非豆科植物共生的弗兰克氏菌(Frankia sp.)的泡囊及其固氮作用

非豆科植物的共生固氮作用大多数是由弗兰克氏菌的侵染形成根瘤引起。其中泡囊是弗氏菌在根瘤内的固氮场所(Akkermans等1977,Tjepkema等1981)。我们采用光学及电子显微镜对泡囊进行了观察,并对根瘤不同部位的泡囊数量及其固氮活性与其它生理活性的关系进行了研究。     

台湾相思结瘤固氮与吸氢酶活性研究

台湾相思的根系具有多年生的根瘤,根瘤初发生时球状,以后发育成分叉瘤和扇状瘤。根瘤固氮活性因苗龄、成熟度不同而有明显差异。环境条件影响结瘤及固氮活性。15℃时结瘤受到明显抑制,固氮作用最适温度条件是25～30℃。光照不足降低根瘤固氮活性。短期轻度干旱不影响根瘤固氮活性,但持续干旱使固氮活性明显下降。pH4.5～8.5条件能正常结瘤,pH5.5时结瘤最好。根瘤固氮作用时不释放H_2,具有较高的吸氢酶活性,在固氮反应系统中加入5％的H_2,能提高根瘤固氮活性。     

哈茨木霉发酵液中肽类物质对豇豆根瘤结构和功能的影响

通过树脂吸附、离子交换、薄层层析、高效液相色谱系统等分离、纯化方法,从哈茨木霉(Trichoderm aharzianum)T2-16菌株发酵液中分离得到一种对豆科作物生长具促进作用的物质,通过质谱等方法鉴定为肽类物质。为探明该活性物质对豆科作物的促生机制,用该活性物质对豇豆种子浸种处理后,进行盆栽实验,通过对盆栽实验中根瘤结构与固氮活性变化的研究,结果显示,该活性物质可增加根瘤侵染组织的面积和根瘤细胞中类菌体的数量,降低根瘤细胞液泡化程度,促进根瘤中公共细胞周膜较多形成,加快类菌体的发育成熟,提高根瘤豆血红蛋白的含量,从而提高根瘤的固氮活性。     

气候因子对三种豆科树种固氮的影响

研究了气候因子对台湾相思(Acacia confusa)、大叶相思(A．awriculaeformis)和南岭黄檀(Dalbergia balansae)根瘤固氮酶和吸氢酶活性的影响。3种树木根瘤均具有吸氢酶活性,外源H：可提高固氮酶活性,表明吸氢酶有助于固氮效率的提高。3树种根瘤的固氮活性有明显季节变化,夏秋活性较高,早春及冬季活性较低。离体根瘤固氮和吸H2活性表达的最适温度为25—30℃。光照强度及土壤湿度均显著影响根瘤固氮和吸H2活性。     

马桑共生固氮根瘤及其内生放线菌

马桑型非豆科内生放线菌的共生固氮根瘤的含菌组织与桤木型不同。前者为一马蹄形整体,围绕着中柱维管束;后者完全包围中柱,其中含菌细胞和不含菌细胞交错存在或形成分散的含菌细胞组织团。尼泊尔马桑(Coriaria nepalensis Wall.)根瘤的内生放线菌菌丝形态与桤木根瘤的内生菌形态相同,具有一层电子密度很高的单层壁和具有单层壁的横隔膜。菌丝分枝,具有中间体。成熟的含菌细胞内有一围绕着中央液泡的栅栏排列的柱形泡囊,它们是菌丝的顶端细胞,其电子密度比菌丝高。含菌组织的衰老部分有颗粒体,颗粒体有双层壁,内层壁与菌丝的相同,外层壁比内层壁厚数倍,电子密度低。     

大豆—根瘤菌共生固氮氢代谢的研究

检测了四株大豆根瘤菌在不同的大豆品种上形成根瘤的放氢、吸氢、固氮活性及豆血红蛋白的含量;同时测定了植株干物质的积累。结果表明,所有固氮根瘤都放氢,自生条件下Hup~-根瘤菌形成的根瘤仍不具吸氢活性,相对固氮率在0.75左右。而Hup~(?)菌株根瘤的相对固氮率在0.91～1之间。寄主植物对Hup~(?)菌株的吸氢活性有影响。相关分析表明,根瘤的豆血红蛋白与吸氢活性呈负相关。干物质积累与固氮酶活性关系最密切,氢酶活性的影响是次要的。     

羊奶果根瘤内生菌的亚显微结构

羊奶果是桤木型根瘤。根瘤的横切面是轴对称的圆形结构,含菌细胞分散于皮层组织中。随着根瘤的发育,内生菌也有不同的形态结构。侵染初期的内生菌是一种分枝、具隔膜的菌丝体。幼龄菌丝中含有电子半透明的颗粒,成熟菌丝没有这种颗粒。成熟菌丝顶端会臌大形成具隔膜的椭圆球状泡囊,直径比菌丝大。不同发育时期的泡囊,其形态结构也有差异。     

Observations on the Ultrastructure of the Root Nodules and Its Endophyte of Elaeagnus mollis Diels

The ultrastructure of the root nodule infecting cell of Elaeagnus mollis Diels and its shapes of the endophyte were observed by light microscope, scanning electron microscope and transmission electron microscope. The endophyte in the root nodules of Elaeagnus mollis D. has five different developing forms: hyphae, nitrogen fixing vesicles, sporangia, sporangio-spores and bacteroid-like cells. The roles played by the different forms of the endophytes in symbiotic nitrogen fixation arc discussed also.     

Plant-endophyte symbiosis in non-leguminous plants

Summary A wide taxonomic range of non-leguminous dicotyledonous plants bear root nodules and are able to fix atmospheric nitrogen. These plants belong to the orders Casuarinales, Myricales, Fagales, Rhamnales, Coriariales, and Rosales. Actinomycetes are involved in the root-nodule symbiosis. Nitrogen fixation is inhibited by hydrogen and carbon monoxide. Combined nitrogen depress nodule formation, but nitrogen fixation still occurs in the presence of combined nitrogen in the medium. In nitrogen-free medium Alnus plants fix in one season of 48 weeks 500 mg N per plant and Ceanothus plants 760 mg N per plant. Fixation by the other plant species is about of the same order. Field estimates showed that the nitrogen increase of the soil was about 61.5–157 kg N per ha per annum, depending on the age of the trees, under Alnus, 58.5 kg N per ha per annum under Casuarina, about 60 kg N per ha per annum under Ceanothus, 27–179 kg N per ha per annum underHippopha? rhamnoides, and about 61.5 kg N per ha per annum underDryas drummondii with someShepherdia spp. Non-leguminous root nodules belong to two types: coralloid root nodules and root nodules where the apex of each nodule lobe produces a negatively geotropic root. The primary infection occurs through the root hairs where a curling effect is observed. In the host cells the endophyte presents itself in three forms: hyphae, vesicles and bacteria-like cells. Vesicles are probably associated with nitrogen fixation, whereas the bacteria-like cells function in the endophyte's survival and dispersal. The endophyte is an obligate symbiont. TheAlnus glutinosa endophyte has been isolated and grownin vitro in root-nodule callus tissue. However, the isolated endophyte produces only ineffective root nodules in re-inoculation tests.     

Continuous CO2 enrichment leads to increased nodule biomass, carbon availability to nodules and activity of carbon-metabolising enzymes but does not enhance specific nitrogen fixation in pea

Recent research has shown that nodule nitrogen fixation is limited under a wide range of environmental constraints by lowered carbon flux within the nodule due to down-regulation of sucrose synthase activity. The aim of this work was to elucidate whether an increase in both carbon flux and activity of enzymes of carbon metabolism in nodules may lead to an increased nitrogen fixation. We report the effects caused by a continuous exposure to atmospheric CO₂ enrichment in nodulated pea plants. CO₂ enrichment led to an enhanced whole-plant growth and increased nodule biomass. Moreover, nodules of plants grown at increased CO₂ showed a higher sugar content as well as enhancement of some activities related to nodule carbon metabolism, such as sucrose synthase, UDP glucose pyrophosphorylase and phosphoenolpyruvate carboxylase. Indeed, acetylene reduction activity, measured by the classical technique, was increased more than four times. However, when specific nitrogen fixation was determined as hydrogen evolution, no significant differences were detected, consistent with the lack of changes of enzymes involved in nitrogen metabolism such as glutamate synthase and aspartate aminotransferase. These results are discussed in the context of the regulation of nitrogen fixation and nodule metabolism.     

Studies on the Relationship Between Photosynthesis and Nitrogen Fixation in the Symbiotic System of Soybean and Nodule Bacteria( Rhizobium)

The relationship between photosynthesis of soybean and nitrogen fixation of the nodules by symbiotic Rhizobium was studied. The contents of total nitrogen and chlorophyll, the net photosynthetic rate and seed yield of soybean were much higher in either hydroponically cultivated or field-grown plants inoculated with Rhizobium B16–11C (or Clark nodulating strain) than in control without inoculation (or Clark non-nodulating strain). These results show that the symbiotic nitrogen fixation has a beneficial effect on photosynthesis. However, the effect was indirect and slow so that there was no change in the net photosynthetic rate of the soybean leaves until three clays after removing nodules from the soybean roots. On the other hand, decreasing the photosynthate supply to nodule by shade, defoliation or shoot removal of the soybean, the nodule activity declined significantly. It seems that the supply of photosynthate to root nodule is a limiting factor for symbiotic nitrogen fixation. However, the diurnal variation of the nodule activity could not be explained by change neither in the contents of sucrose and starch of the root nodules nor in the ambient temperature. The factor controlling the diurnal variation deserves further study.     

大豆-根瘤菌共生体系光合与固氮关系研究

水培大豆和田间生长的大豆,接种根瘤菌 Rhizobium B16-11C 后植株全氮含量、叶片叶绿素含量和净光合速率及种子产量都明显增加。比较 Clark 大豆的结瘤品系和不结瘤品系获类似结果。摘除根瘤后3天内叶片净光合速率无明显变化。大豆植株遮阴、去叶或切掉地上部导致根瘤活性明显下降。但去豆荚不能提高根瘤固氮的比活性。根瘤活性的日变化不能用根瘤蔗糖、淀粉含量或周围温度的变化来解释,其控制因子尚待深入研究。     

A Quantitative Study of Fixation and Transfer of Nitrogen in Alnus

A quantitative study of the fixation of nitrogen and of itstransfer from the nodules to the remainder of the plant hasbeen made in Alnus plants during their first season of growth.Fixation per plant reached a maximum in late August but fellrapidly with the onset of autumn, while fixation per unit dryweight of nodule tissues was greatest in young nodules and wasof the same order as in nodulated legumes. Throughout the growthseason there was a steady transfer from the nodules of some90 per cent, of the nitrogen fixed. The rate of fixation relativeto the growth of the endophyte is much higher than in free-livingnitrogen-fixing organisms and is clearly governed by the nitrogenrequirements of the entire symbiotic system. These findingsare compatible with the view that the fixation process is extracellularto the endophyte.     

Consequences of Sporangial Development for Nodule Function in Root Nodules of Comptonia peregrina and Myrica gale

Frankia sp., the actinomycetous endophyte in nitrogen-fixing actinorhizal nodules, may differentiate two forms from its hyphae: vesicles and sporangia. In root nodules of Comptonia peregrina (L.) Coult. and Myrica gale L., sporangia may be either absent or present. Nitrogenase activity and symbiotic efficiency were contrasted in spore(+) and spore(−) nodules of these two host genera. Seedlings of C. peregrina nodulated with the spore(+) inoculum showed only 60% of the nitrogenase activity and 50% of the net size of their spore(−) counterparts after 12 weeks of culture. Measurements of acetylene reduction (i.e., nitrogenase activity) were coordinated with samplings of nodules for structural studies. Significant differences in acetylene reduction rates were discernible between spore(+) and spore(−) nodules commencing 4 weeks after nodulation, concomitant with the maturation of sporangia in the nodule. Spore(+) nodules ultimately reached less than half of the rate of nitrogenase activity of spore(−) nodules. Both types of nodules evolved only small amounts of molecular hydrogen, suggesting that both were equally efficient in recycling electrons lost to the reduction of hydrogen ions by nitrogenase. Respiratory cost of nitrogen fixation, expressed as the quotient of micromole CO₂ to micromole ethylene evolved by excised nodules, was significantly greater in spore(+) than in spore(−) nodules. M. gale spore(−) nodules showed variable effectivity, though all had low CO₂ to ethylene evolution ratios. M. gale spore(+) nodules resembled C. peregrina spore(+), with low effectivity and high respiratory cost for nitrogen fixation.     

野生大豆（Glycine soja）酰脲含量与根瘤固氮活力的关系

野生大豆（Ｇｌｙｃｉｎｅｓｏｊａ）酰脲含量与根瘤固氮活力的关系朱长甫,苗以农,刘学军,许守民（东北师范大学生命科学学院,长春１３００２４）郑惠玉,徐豹（吉林省农业科学院大豆研究所,公主岭１３６１００）关键词：野生大豆,固氮活力,酰脲,蛋白质根据固氮豆...     

Studies of an effective strain ofFrankia fromAllocasuarina lehmanniana of the Casuarinaceae

Summary Seedlings ofCasuarina spp. andAllocasuarina spp. were grown from seed in the greenhouse and inoculated with a nodule suspension fromC. equisetifolia. Plants ofCasuarina spp. nodulated regularly and were effective in nitrogen-fixation. Only one species ofAllocasuariona, A. lehmanniana formed root nodules. Using these plants as source of inoculum, the isolation of a newFrankia sp. HFPA11I1 (HFP022 801) was made and the strain was grown in pure culture.Frankia sp. HFPA11I1 grows well in a defined medium and shows typical morphological characteristics. In media lacking combined nitrogen, the filamentours bacterium forms terminal vesicles in abundance and differentiaties large intrahyphal or terminal sporangia containing numerous spores. This strain, used as inoculum, nodulates effectively seedlings ofC. equisietifolia andC. cunninghamiana, forming nodules with verically-growing nodule roots. Although effective in acetylene reduction, the endophyte within the nodules is filamentous and lacks veiscles. When used to inoculated seedlings ofA llocasuarina lehmanniana, Frankia sp. HFPA11I1 induces root nodules which are coralloid and lacking nodule roots. The nodules are effective in acetylene reduction and the filamentous hyphae ofFrankia within the nodule lobes lack vesicles. Effective nodulation inA. Lehmanniana depends upon environmental conditions of the seedlings and proceeds much more slowly than in Casuariana.     

Interactive influence of phosphorus and iron on nitrogen fixation by soybean

Adequate supplies of phosphorus (P) and iron (Fe) to legumes have been shown to be crucial in obtaining high nitrogen fixation rates and growth. These responses are anticipated as a result of the high requirement for P in energy transfer processes in the nodule and for Fe as a constituent of nitrogenase and leghemoglobin. However, little attention has been given to documenting the response of nitrogen fixation rates resulting from concentrations of P and Fe that actually exist in nodules. In particular, an open question is whether there is an interaction between nodule P and Fe concentrations that maximize nitrogen fixation activity. This study was designed to induce various concentrations of P and Fe in the nodule and to measure the resultant nitrogen accumulation and nitrogen fixation rates. Plant nitrogen accumulation was linearly correlated with both nodule P and Fe concentration, and with total plant nitrogen fixation rate as measured by acetylene reduction rate. Therefore, total nitrogen fixation rate was also correlated with nodule P and Fe concentrations, but a higher linear correlation was obtained for Fe as compared to P concentration. Surprisingly, nodule ureide concentration, which is generally assumed to be a positive index of nitrogen fixation rate, was negatively correlated with nodule P and Fe concentrations. These results indicated that higher concentrations of P and Fe in the nodules not only stimulated higher nitrogen fixation rates, but were associated with an enhanced ability to export ureides from the nodules. Since there was a linear response to both P and Fe over the range of nodule concentrations induced in these experiments, no evidence for optimum interactive concentrations of these two elements in the nodules was obtained.