三叶草、豌豆和快生型大豆根瘤菌类菌体繁殖研究的进展

采用单个原生质体分离和微室培养技术研究了三叶草、豌豆和快生型大豆根瘤菌在根瘤中的分化和繁殖。结果表明:快生型大豆根瘤菌体的分化和繁殖特性与慢生型大豆根瘤菌类似,多个杆状类茵体包含在一个共同的类菌体周膜中,可区分出未成熟的细小杆状类菌体和成熟的杆状类菌体;其繁殖率在刚现瘤时<0.01％,到10周瘤龄时增加到40％以上。而三叶草和豌豆根瘤菌在根瘤中的分化过程是从小杆菌→未成熟细长杆状类菌体→成熟的棒状或Y状类菌体。在一般条件下,只有小杆菌才能繁殖,其繁殖率也随瘤龄而增加。在根瘤发育后期,少数成熟的三叶草和豌豆根瘤类菌体,在含水量较多时,可以转化为活跃运动的大杆菌,然后在分裂过程中逐次缩小并最终转变为正常的根瘤小杆菌;含水量较少时,大杆菌继续生长形成假丝状体,最后再断裂为大杆菌或停止生长。渗透压保护不是根瘤类菌体或小杆菌繁殖的必要条件,除对幼小根瘤的未成熟类菌体外,它妨碍成熟类菌体或小杆菌的生长和繁殖。     

氮锌复合作用对白三叶草根瘤生长发育和营养元素吸收的影响

采用砂培试验、中子活化和电子显微技术,研究了不同水平氮锌配施对白三叶草根瘤生长发育、营养元素吸收的影响。结果表明,随施氮水平增加,根瘤的数量、固氮酶活性、单瘤重量、细胞内类菌体数量、营养元素吸收量显著下降。与低锌条件(0.1μmol Zn/L)相比,足量锌(2.0μmol Zn/L)显著增加了根瘤的数量、单瘤重量、固氮酶活性、营养元素吸收量和细胞内类菌体数量。与其他处理相比较,低氮和足量锌处理(5mmol N/L、2.0μmol Zn/L)显著增加了根瘤的数量、单瘤重量、固氮酶活性、营养元素吸收量和细胞内类菌体数量。     

水生植物对~(134)Cs的吸收

水体中(134)~Cs的消失和水生植物对(134)~Cs的吸收均以指数回归形式进行。螃蜞菊(Alternanthera philoxeroides)对水体中(134)~Cs的吸收速率最快,富集系数最高,达560。卡州萍(Azolla caroliniana W.)为12.8。金鱼藻(Ceratophyll-um demersum L.)和水葫芦(Eichhornia crassipes)分别为4.6和3.5。因此,螃蜞菊能净化水体中的(134)~Cs。植物根系吸收(134)~Cs后,能把它运转到地上部,螃蜞菊中约有75％的(134)~Cs停留于根部,25％运转到地上部。     

辐照诱发木耳营养缺陷型突变的研究

本文用~(60)Coγ射线10—200krad辐照木耳单核担孢子,获得9株营养缺陷型菌株,其中光木耳[Auricularia auricula(L.ex Hook)Underw.]8株,琥珀木耳[Auricularia fuscosucinea(Mont.)Farlow.)1株,诱变频率为2.38×10~(-3)-44.4×10~(-3)。辐照诱变有效剂量,光木耳为200krad,琥珀木耳为10krad。突变体生理生化研究表明,突变体的菌落形态、菌丝生长速度、氨基酸含量、酯酶同工酶酶谱等均发生了变异。     

水稻黄叶突变体光合特性的日变化

对水稻黄叶突变体黄玉B及其亲本龙特甫B孕穗期的光合速率和叶绿素荧光参数的日变化所进行的研究表明:(1)在自然日照条件下,当光强上升到1043.4μmol/m2.s时,野生型出现光饱和点并表现出光抑制现象,而突变体没有出现光饱和点;(2)在野生型出现光抑制阶段(12:00—14:00),突变体的光合速率(Pn)、PSⅡ原初光化学效率(Fv/Fm)、PSⅡ光量子效率(фPSⅡ)、非循环光合电子传递速率(ETR)和热耗散(NPQ)均高于野生型。突变体在强光条件下(PFD>1149.2μmol/m2.s)能有效利用光能并耗散过剩光能,其对强光光响应能力优于野生型亲本。     

塑料簿膜覆盖下棉花氮素营养特性及增产效果

本试验应用~(15)N标记硫铵研究塑料薄膜覆盖下直播棉花的氮素营养特性及其增产效果。试验表明:盖膜棉花吸收的总氮量明显高于不盖膜处理,苗期尤为突出,盖膜棉株的总氮量为不盖膜处理的244—267%。盖膜并施肥不仅增加了棉株对土壤氮和肥料氮的吸收利用,而且,通过营养器官输往生殖器官的肥料氮量与土壤氮量也分别比不盖膜处理高50.5%和157%,初花期追肥,于初花—盛花阶段形成了吸收肥料氮的高峰,在棉株吸自肥料的氮素中有63.3—76.6%是在这一阶段吸收的。盖膜棉花对氮肥的当季利用率为36%,比不盖膜处理高9%。盖膜施肥处理棉花的产量最高,每公顷产籽棉2472公斤。     

不同抗旱性绿豆突变体的抗旱生理特性

对抗旱性不同的4个绿豆材料〔包括3个突变体172-3(高抗)、159-1(中抗)、145-1(弱抗)和原材料中绿2号(不抗)〕在不同生育期不同程度水分胁迫下的抗旱生理特性进行了研究。发现随着水分胁迫的加剧,抗旱性强的突变体其脯氨酸(proline,Pro)积累量加大,膜透性损伤程度变小,MDA含量增加幅度小,SOD活性明显高于抗性低的品种,表明这些生理特性与绿豆的抗旱性有关。     

辐照对黄籽油菜种子活力、超氧物歧化酶活性和脂质过氧化作用的影响

用~(60)Coγ射线辐照2个杂交组合高世代材料中分离出的黄籽和黑籽甘蓝型油菜(Brassica napus L.)近等基因系种子,测定辐照前、后种子在发芽过程中的种子活力,超氧物歧化酶(SOD)和脂质过氧化产物丙二醛(MDA)的变化。结果表明,辐照后,黄籽比黑籽的SOD活性上升幅度小,MDA含量上升幅度大,种子活力下降较多。黄籽油菜种子的辐射敏感性比黑籽强;油菜的辐射抗性或敏感性不仅与体内保护酶水平有关,也可能与种皮的特殊保护结构和保护物质有关。     

蓝刺头组织培养和叶片再生植株的研究

以蓝刺头(Echinops latifoliusTausch.)叶片为外植体,建立了蓝刺头的再生体系,并对其影响因素进行了研究。结果表明,MS+6-BA 1.0mg.L-1+NAA 0.1mg.L-1为最适分化培养基,再生率达48.33%,平均每个外植体再生芽数3.56;添加2.0mg.L-1的硝酸银以及暗处理15d均可显著提高不定芽的再生率和再生芽数,再生率分别提高到80.33%和63.33%。     

绍鸭垂体LHRH放射受体结合法及其结合特性

以促性腺激素释放激素(LHRH) 的高效类似物(D Lys6)LHRH 作为示踪物。在垂体膜制剂和胶原酶及胰酶分散的体外培养的垂体细胞水平上,研究了绍鸭垂体LHRH 受体的结合特性。106 个垂体细胞与125I ( D Lys6) LHRH 在4 ℃孵育90 min能获得较高的结合率,经24h 孵育后结合率显著下降。125I (D Lys6)LHRH 与垂体膜制剂的结合率随膜制剂的浓度增加而增加,在每管相当于1 ～2 个垂体浓度范围内呈正相关。特异性结合随125 I ( D Lys6 ) LHRH 量的增加而增加, 实验结果经Scatchard 分析揭示出特异性结合与结合和游离125I ( D Lys6)LHRH 之比呈线性关系,预示绍鸭垂体对( D Lys6)LHRH 存在同一类高亲和力的结合位点。垂体膜制剂和垂体整体细胞的平衡解离常数( Kd) 分别为0-34n M 和0-43n M ,两个Kd 值相近且垂体整体细胞显示出较大的最大结合容量(Bmax) ,这说明本研究的酶法消化分散垂体细胞对其LHRH 受体的损伤较小。( D Lys6) LHRH(10 - 11 ～10 - 6 M) 能取代示踪物的特异性结合。本研究结果验证了绍鸭垂体LHRH 受体的存在并提供了其基本结合特性。     

白浆土大豆结瘤及其固氮状况

黑龙江省是我国大豆主要产区,在国营农牧场中大面积机械化生产条件下,大豆的种植面积约占耕地面积的三分之一左右。一般认为,大豆与根瘤菌的共生固氮作用所固定的氮,能提供大豆整个生育过程中对氮素需要量的二分之一到三分之二。然而,在大田生产实践中,由于土壤类型、肥力水平、气候条件、前作、品种、施肥等因素的综合影响,使大豆在田间的共生固氮效率产生了很大的差异。     

Nitrogenase divarication with histological attributes distinctive for glycosylated aerial stem nodules and nitrosylated root nodules of sesbania

Exceptional symbiotic nitrogen fixation with Sesbania has provided high soil fertility for many past centuries of paddy rice production. Unique stem nodulation results in high nitrogenase activity levels of S. rostrata, Brem, during rapid growth in continuously flooded rice fields that greatly disfavor legume root nodulation and this functional development. The objective of this study was to determine plant nutrient interactions that influence contrasting root and aerial stem nodule histology governing effective nitrogenase activity levels and nitrogen fixation. Top growth, nodulation, and nitrogenase activity levels were significantly increased with increased available soil P. Response to K levels and Ca additions resulted only when soil P was adequate in all treatment combinations. However, there was no significant correlation between fresh nodule weight, nitrogenase activity, and nodules plant^‐1 for both root nodules and aerial stem nodules. Nodule histology was highly contrastive with nodule type and Rhizobium morphology, cytosol composition, and governing enzyme activity levels. Distinctive nonpleomorphic cocci bacteroids of functional aerial stem nodules have tentative designation as Azorhizobium caulinodans gen. nov. sp. nov.     

The HFC/HCFC breakdown product trifluoroacetic acid (TFA) and its effects on the symbiosis between Bradyrhizobium japonicum and soybean (Glycine max)

The environmental impact of hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) are under intense study due to the resistance of the breakdown product, trifluoroacetic acid (TFA), to further degradation. TFA has come under scrutiny due to its rapid and complete partitioning into aqueous phases of the environment, eventually allowing for deposition of TFA into soil via precipitation. Evidence exists that TFA may be toxic to soil microbes and plants, with little or no degradation occurring in soils. Uptake by plants and microorganisms and its similarity to acetate, implies its potential to effect the symbiotic nitrogen-fixing partners Bradyrhizobium japonicum and soybean (Glycine max). A preliminary study was performed in accordance with the Alternative Fluorocarbon Environmental Acceptability Study (AFEAS). Those results are presented here in addition to the findings of further experimentation on the initial interaction of B. japonicum with soybean. We used three levels of TFA (0.67, 6.74 and 67.40 μl TFA kg⁻¹ soil; 0.003, 0.031 and 0.314 μl TFA l⁻¹) for soil and hydroponics conditions and three levels (10, 100 μM and 1 mM) in bacterial culture. The results demonstrate that TFA affects growth of B. japonicum significantly, but does not affect PHB accumulation. Also no F⁻ was found in cultures grown on TFA. Attachment of B. japonicum to soybean roots was enhanced with the lowest level of acetate or TFA and was significantly reduced with 1 mM acetate or TFA. Cultures grown on acetate or acetate with TFA do not attach well, with those grown with 1 mM TFA the least. Both effects may be attributed to pH. Soybean seedlings had significantly retarded development with levels of TFA at or above 6.74 μl TFA kg⁻¹ soil and 0.031 μl TFA l⁻¹ nutrient solution. No nodules formed on those plants treated with these levels of TFA except in the hydroponics trials. Nodule location was not affected regardless of the TFA level. At the lowest level used we found no effects on soybean or symbiotic nitrogen fixation. In some cases, nodulation was enhanced, but nodule weight reduced. Anaerobically isolated bacteroids had normal levels of acetylene reduction activity regardless of the level of TFA used. In summary, soybean is much more sensitive to low levels of TFA than its symbiotic counterpart B. japonicum. No detrimental effects on symbiotic nitrogen fixation in soybean should be expected unless large bioaccumulation of TFA occurs in agricultural areas.     

Nitrogen fixing microorganisms in paddy soils XII

Introduction

We have been studying the interrelation between R. capsulatus and other various microorganisms, in which there are symbiotic relationships (I). When R. capsulatlls and Az. vinelandii co-existed, molecular nitrogen was fixed much more than in each pure culture and many slime substances (polysaccharides, muco-polysaccharides etc.) were produced (2). In order to study symbiotic nitrogen fixation between the two microorganisms, first, the nature of the cell wall of both bacteria has to be known.     

How are nitrogen fixation rates regulated in legumes?

Symbiotic nitrogen fixation by the legume‐Rhizobium symbiosis is a finely regulated process that involves significant carbon and energy metabolism by the plant. At present, there are three competing theories as to how the regulation of the process is achieved at the whole plant level. Theory one (carbon supply regulation) states that nitrogen fixation rates are regulated by either current nodule assimilate supply or through metabolism of assimilates into compounds that can be used by the bacteroids. A second theory (oxygen supply regulation) assumes that oxygen diffusion into the nodules is tightly regulated and is the principal regulatory factor for nitrogen fixation rates. A third theory (N‐feedback regulation) suggests that a product of nitrogen fixation or assimilation exerts a feedback regulatory impact. The paper summarizes experimental data which support or reject the mentioned theories. Moreover, implications of nitrogen fixation under P stress and of phenomena connected with the argon or acetylene induced decline in nitrogenase activity for the understanding of nitrogen fixation regulation are discussed. It is concluded that we currently have no theory that explains all aspects and experimental results concerning the regulation of nitrogen fixation in legumes. With our growing ability to impact the process, e.g., by genetic engineering, this understanding of nitrogen fixation regulation has potential to be translated into agronomically sustainable benefits.     

Hydrogenase Activity of Soybean Nodules Doubly Infected with Bradyrhizobium japonicum and B. elkanii

Rhizobitoxine (2-amino-4-(2-amino-3-hydropropoxy)-trans-but-3-erioic acid) is a phytotoxin produced by some strains of Bradyrhizobium species. Rhizobitoxine-producing strains often induce chlorosis in new leaves of soybean as a result of the synthesis of the toxin in nodules (Owens and Wright 1964; Owens et al. 1972). Some of the B. japonicum bacteroids possessing the hydrogen uptake (Hup) system are capable of ATP production by recycling H₂ evolved from nitrogenase (Evans et al. 1987). Adequate uptake hydrogenase activity in soybean bacteroids often enhances plant growth, as well as the efficiency of energy utilization during nitrogen fixation (Evans et al. 1987).     

PLANT GROWTH PROMOTING RHIZOBACTERIA INCREASE GROWTH,YIELD AND NITROGEN FIXATION IN PHASEOLUS VULGARIS

Nitrogen (N) fixation by legume-Rhizobium symbiosis is important to agricultural productivity and is therefore of great economic interest. Growing evidence indicates that soil beneficial bacteria can positively affect symbiotic performance of rhizobia. The effect of co-inoculation with plant growth-promoting rhizobacteria (PGPR) and Rhizobium, on nodulation, nitrogen fixation, and yield of common bean (Phaseolus vulgaris L.) cultivars was investigated in two consecutive years under field conditions. The PGPR strains Pseudomonas fluorescens P-93 and Azospirillum lipoferum S-21 as well as two highly effective Rhizobium strains were used in this study. Common bean seeds of three cultivars were inoculated with Rhizobium singly or in a combination with PGPR to evaluate their effect on nodulation and nitrogen fixation. A significant variation of plant growth in response to inoculation with Rhizobium strains was observed. Treatment with PGPR significantly increased nodule number and dry weight, shoot dry weight, amount of nitrogen fixed as well as seed yield and protein content. Co-inoculation with Rhizobium and PGPR demonstrated a significant increase in the proportion of nitrogen derived from atmosphere. These results indicate that PGPR strains have potential to enhance the symbiotic potential of rhizobia.     

茎瘤固氮根瘤菌Azorhizobium caulinodansORS571基因组分泌蛋白的生物信息学分析

为了获取茎瘤固氮根瘤菌（AzorhizobiumcaulinodansORS571）的分泌蛋白，以便更深入地了解该菌的共生固氮作用，本研究采用SignalP、TMHMM、PSORTb、TargetP、LipoP、TatP和SecretomeP软件对该菌全部4717个蛋白序列进行分析预测。结果共识别了653个分泌蛋白，其中具有分泌型信号肽的蛋白54个，具有RR—motif型信号肽的蛋白1个，具有脂蛋白信号肽的蛋白2个和非经典分泌蛋白596个。该菌含信号肽分泌蛋白仅占全部蛋白的1．2％，低于其它固氮菌。在分泌蛋白中识别了核酸内切酶和核糖核酸酶等6个核酸酶。它们可能参与宿主植物遗传物质的降解，干扰宿主遗传代谢，进一步在宿主植物侵染过程中起到重要作用。此外还识别了超氧化物歧化酶、过氧化氢酶和谷胱甘肽S-转移酶等4个抗氧化酶。它们可能参与活性氧的清除以保护固氮酶，是该菌固氮过程的重要参与者。     

Effect of glyphosate on symbiotic N2 fixation and nickel concentration in glyphosate-resistant soybeans

Decreased biological nitrogen fixation in glyphosate-resistant (GR) soybeans has been attributed directly to toxicity of glyphosate or its metabolites, to N₂-fixing microorganisms. As a strong metal chelator, glyphosate could influence symbiotic N₂ fixation by lowering the concentration of nickel (Ni) that is essential for the symbiotic microorganisms. Evaluation of different cultivars grown on different soil types at the State University of Maringá, PR, Brazil during the summer 2008 revealed, significant decreases in photosynthetic parameters (chlorophyll, photosynthetic rate, transpiration and stomatal conductance) and nickel content with glyphosate use (single or sequential application). This work demonstrated that glyphosate can influence the symbiotic N₂ fixation by lowering nickel content available to the symbiotic microorganisms.     

马占相思根瘤菌结瘤固氮特性的分析

相思属（Acacia）树种是速生的热带、亚热带豆科植物。对现在大面积种植的相思树品种——马占相思的根瘤菌进行分离和筛选，获得菌株若干株，对它们的结瘤固氮特性和对马占相思、大叶相思及厚荚相思生长的影响等进行了初步研究。结果表明。无氮条件下接种马占相思根瘤菌，能显著促进这3个树种的株重、株高和生物量的增长；苗圃接种马占相思根瘤菌。马占相思苗高增加27．6％，地径增加14．8％，植株鲜重增加32．6％，结瘤数增加83．8％。