The influence of Rhizobium and arbuscular mycorrhizal fungi on nitrogen and phosphorus accumulation by Vicia faba

BACKGROUND AND AIMS: The aim of this study was to investigate the effects of the interactions between the microbial symbionts, Rhizobium and arbuscular mycorrhizal fungi (AMF) on N and P accumulation by broad bean (Vicia faba) and how increased N and P content influence biomass production, leaf area and net photosynthetic rate. METHODS: A multi-factorial experiment consisting of four different legume-microbial symbiotic associations and two nitrogen treatments was used to investigate the influence of the different microbial symbiotic associations on P accumulation, total N accumulation, biomass, leaf area and net photosynthesis in broad bean grown under low P conditions. KEY RESULTS: AMF promoted biomass production and photosynthetic rates by increasing the ratio of P to N accumulation. An increase in P was consistently associated with an increase in N accumulation and N productivity, expressed in terms of biomass and leaf area. Photosynthetic N use efficiency, irrespective of the inorganic source of N (e.g. NO3- or N2), was enhanced by increased P supply due to AMF. The presence of Rhizobium resulted in a significant decline in AMF colonization levels irrespective of N supply. Without Rhizobium, AMF colonization levels were higher in low N treatments. Presence or absence of AMF did not have a significant effect on nodule mass but high N with or without AMF led to a significant decline in nodule biomass. Plants with the Rhizobium and AMF symbiotic associations had higher photosynthetic rates per unit leaf area. CONCLUSIONS: The results indicated that the synergistic or additive interactions among the components of the tripartite symbiotic association (Rhizobium-AMF-broad bean) increased plant productivity.     

Reactive oxygen species and nitric oxide are involved in ABA inhibition of stomatal opening

Although nitric oxide (NO) and reactive oxygen species (ROS) are essential signalling molecules required for mediation of abscisic acid (ABA)-induced stomatal closure, it is not known whether these molecules also mediate the ABA inhibition of stomatal opening. In this study, we investigated the role of NO and ROS in the ABA inhibition of stomatal opening in Vicia faba. ABA induced both NO and ROS synthesis, and the NO scavenger reduced the ABA inhibition of stomatal opening. Exogenous NO and hydrogen peroxide (H2O2) also inhibited stomatal opening, indicating that NO and ROS are involved in the inhibition signalling process. An inhibitor of nitric oxide synthase (NOS) reversed the ABA inhibition of stomatal opening. Either the NO scavenger or the NOS inhibitor also reversed the process in the H2O2 inhibition of stomatal opening. We found that in the ABA inhibition of stomatal opening, NO is downstream of ROS in the signalling process, and NO is synthesized by a NOS-like enzyme.     

The influence of nitrate supply on nitrogen fixation during growth of the field bean Vicia faba in sand

Field bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station and grown in sand culture supplied with ¹⁵N-labelled nitrate at two concentrations. Plants were sampled at intervals throughout their growth for ¹⁵N and total N analysis. The rate of nitrate uptake was almost uniform up to pod-fill and was proportional to the nitrate concentration. Nodule weight was slightly depressed by the larger nitrate concentration at all samplings, and there was a corresponding reduction in the amount of atmospheric nitrogen fixed. However, at harvest the bean seeds from plants given most nitrate contained slightly more total N, as the enhanced nitrate uptake outweighed the reduction in fixation.     

Comparison of acetylene-reduction and nitrogen-15 techniques for the determination of nitrogen fixation by field bean (Vicia faba) nodules

Field bean (Vicia faba L.) cv. Maris Bead seeds were inoculated with Rhizobium Catalogue No. 1001, supplied by Rothamsted Experimental Station, and grown in sand culture supplied with a complete nutrient solution which included nitrate at either 1.5 or 6.0 mM. Nodules were detached from the roots at intervals during plant development and their rates of nitrogen fixation estimated by both acetylene reduction and ¹⁵N gas technique. There was a constant relationship, independent of nitrate supply, between the results obtained by these two methods at all samplings. The amounts of acetylene reduced divided by a factor of 5.75 gave the amount of true nitrogen fixation; this factor is about twice the theoretical value. It is suggested that this discrepancy arose because, with acetylene, all the electrons available to the nitrogenase were used to form ethylene, whereas during normal fixation only about half the electron supply was used to fix nitrogen, the remainder having been consumed in the production of hydrogen gas.     

Biocontrol of broomrape (Orobanche crenata Forsk. and Orobanche foetida Poir. ) by Pseudomonas fluorescens isolate Bf7-9 from the faba bean rhizosphere

Bacteria of the faba bean (Vicia faba L.)/Orobanche spp. root environment were evaluated for their potential use as biocontrol agents for the parasitic weed. Bacteria were isolated mainly from the rhizosphere of faba bean as well as from diseased Orobanche underground structures and an Orobanche-suppressive soil from three districts of northern Tunisia. Out of 351 bacterial isolates, 337 were tested for pathogenicity in an inverted pyramidal-shape screening programme including a Lactuca sativa L. seedlings bioassay, root-chamber and pot experiments. In pre-selection screening on L. sativa seedlings, 37 isolates (11%) showed a strong growth inhibitory effect, of which 70 and 84% also had a significant suppressive activity on the pre-emergence structures of O. foetida and O. crenata, respectively, in root-chamber experiments. Among five bacterial isolates selected for pot trials, strain Bf7-9 of Pseudomonas fluorescens showed high biocontrol activity against both species of Orobanche and positively influenced faba bean growth. The bacterium reduced shoot emergence of O. crenata and O. foetida by 64 and 76% and their dry weight by 39 and 63%, respectively, compared with non-inoculated controls. Pseudomonas marginalis strain Nc1-2 exhibited also a tendency to reduce incidence of O. crenata and to improve faba bean performance. Results of the present study suggest that application of naturally occurring rhizosphere bacteria offers an additional approach for biocontrol of Orobanche spp. that can supplement current methods of control in an integrated weed management strategy.     

Calcium-Based Interactions of Symbiotic Partners in Legumes: Role of Peribacteroid Membrane

Based on experimental evidence, a concept is formulated that mutualistic relationships between pro- and eukaryotic cells during nitrogen-fixing legume–rhizobia symbiosis rely both on selective transfer of metabolites and ion transport, Ca²⁺ in particular, across the peribacteroid membrane (PBM). PBM in the nitrogen-fixing cells of yellow lupine (Lupinus luteus L.) and broad bean (Vicia faba L.) is endowed with a calcium-translocating ATPase that pumps Ca²⁺ into the symbiosome. This pumping ensures, on the one hand, calcium homeostasis in the cytosol of infected plant cells and, on the other hand, it optimizes Ca²⁺ level in symbiosomes, first of all in the bacteroids, because Ca²⁺ is one of the main factors controlling their nitrogenase activity. The balance between the symbiotic partners and the maintenance of optimal Ca²⁺ level in the bacteroids also depends on passive Ca²⁺ efflux from symbiosomes to the plant cell cytosol via calcium channels. The Ca²⁺-transporting mechanisms residing at PBM are characterized.     

About a rare case of intolerance toVicia faba in a non G-6-PD deficient subject

Summary The history of a non G-6-PD deficient woman, who developed a hard intolerance reaction to theVicia fiba ingestion is described.     

Interaction between Orobanche crenata and its host legumes: unsuccessful haustorial penetration and necrosis of the developing parasite

BACKGROUND AND AIMS: Orobanche species represent major constraints to crop production in many parts of the world as they reduce yield and alter root/shoot allometry. Although much is known about the histology and effect of Orobanche spp. on susceptible hosts, less is known about the basis of host resistance to these parasites. In this work, histological aspects related to the resistance of some legumes to Orobanche crenata have been investigated in order to determine which types of resistance responses are involved in the unsuccessful penetration of O. crenata. METHODS: Samples of resistance reactions against O. crenata on different genotypes of resistant legumes were collected. The samples were fixed, sectioned and stained using different procedures. Sections were observed using a transmission light microscope and by epi-fluorescence. KEY RESULTS: Lignification of endodermal and pericycle host cells seems to prevent parasite intrusion into the root vascular cylinder at early infection stages. But in other cases, established tubercles became necrotic and died. Contrary to some previous studies, it was found that darkening at the infection site in these latter cases does not correspond to death of host tissues, but to the secretion of substances that fill the apoplast in the host-parasite interface and in much of the infected host tissues. The secretions block neighbouring host vessels. This may interfere with the nutrient flux between host and parasite, and may lead to necrosis and death of the developing parasite. CONCLUSIONS: The unsuccessful penetration of O. crenata seedlings into legume roots cannot be attributed to cell death in the host. It seems to be associated with lignification of host endodermis and pericycle cells at the penetration site. The accumulation of secretions at the infection site, may lead to the activation of xylem occlusion, another defence mechanism, which may cause further necrosis of established tubercles.     

SO2对蚕豆根尖细胞微核的诱导作用

应用蚕豆根尖微核试验,对SO2的遗传毒性效应进行了研究。结果表明：一定浓度范围内（0.108-14.00mg/m^3）,蚕豆根尖微核细胞数与SO2浓度间呈正相关,太原市大气污染严重的冬季采暖期根尖细胞微核率明显高于非采暖期;SO2浓度0.604mg/m^3处理24h和48h或2.80-28.00mg/m^3熏气处理4h可使蚕豆根尖中具有微核的细胞数明显增加,结果表明,低浓度SO2较长时间接触或高浓度短期接触均可引起蚕豆根尖细胞遗传物质的损伤,应用蚕豆根尖细胞微核实验可对大气SO2污染进行生物监测。SO2（2.80-28.00mg/m^3）熏气实验中,接触时间延长能导致根尖细胞微核率下降,2.80mg/m^3熏气组下降较快,14.00mg/m^3熏气组下降较慢,研究结果提示,在运用蚕豆根尖微核实验监测环境SO2污染时要考虑蚕豆的染毒方式,避免假阴性结果的出现。     

蚕豆染色体的复制带显带技术

本文采用作者首创的双周期BrdU二次标记法研究了蚕豆根尖细胞染色体的复制带,得到了分布在整条染色体上的清晰稳定的多条带纹.这是复制带首次在植物染色体上取得的具有实用意义的带型.为进一步制定植物染色体的标准带型和研究植物染色体的复制方式提供了一条途径.     

在非光合条件下外源蔗糖能促进蚕豆的气孔开放

蚕豆植株经暗饥饿处理40h后,取其下表皮,再用超声波“原位分离”下表皮上的保卫细胞对,然后在无菌、非光合条件下,用外源蔗糖处理蚕豆下表皮上的保卫细胞对,考察其对气孔开放的效应。结果发现,在1d的无菌培养过程中,蔗糖显著促进了气孔的开放。100mmol/L的蔗糖在10mmol/L的MES-NaOH/KOH(pH6.1)缓冲液中,开度分别增加2.0/2.6μm;在1μmol/L的气孔开放促进剂fusicoccin(FC)的存在下,100mmol/L的蔗糖在MES-NaOH/KOH(pH6.1)缓冲液中分别增加开度5.0/5.5μm。不同浓度（5～200mmol/L）的蔗糖处理结果表明气孔开度的增加与蔗糖浓度呈一定的正相关,浓度为100mmol/L的蔗糖处理表现出最大促进作用。同时还初步观察到,蔗糖可维持保卫细胞存活率和叶绿体的完整性。     

MAD2蛋白在蚕豆细胞周期中的同源定位

细胞周期是一个高度有序的过程,其运行过程受到多个检验点(checkpoint)的严格监控.MAD2是动物细胞纺锤体检验点(spindle checkpoint)中一种重要的蛋白。我们利用免疫印记法从蚕豆组织中检测到一种MAD2的同源蛋白,该蛋白的分子量在26KD左右,其亚细胞分布方式与动物细胞大致相同,都随细胞周期的进行而变化:在间期细胞中,MAD2分布于整个细胞中,并且在核膜外侧有优先聚集;在有丝分裂前期细胞中,MAD2在核膜破裂后开始在动粒处聚集;到早中期(prometaphase),MAD2定位于动粒;随着微管的延伸,MAD2逐渐减少直至消失,在中期,晚中期及后期细胞中,动粒处已无MAD2的分布。     

遮光对蚕豆花荚形成和脱落的影响

本文旨在研究蚕豆开花前后不同时期光照强度对花荚形成和脱落的影响。产量补偿能力以及花荚形成和脱落的生理生态原因。蚕豆花前遮光,开花总数和结荚数降低,但花荚脱落率下降,粒重增加。花期和花后遮光,对开花总数没有明显影响,但花荚脱落严重,减产最多。任何时期遮光均使比叶重、遮光后期叶绿素含量、光合生产量、生殖器官干物质分配率,可溶性糖和含N量下降,但成熟期可溶性糖和含N量,营养元素吸收量不受影响。遮光导致花荚形 成和产量减少的主要原因是C／N比值下降,而不是改变营养元素的丰度所致。     

星型孢菌素(STS)对蚕豆气孔运动的调控效应

用激光扫描共聚焦显微技术,初步研究广谱性蛋白激酶抑制剂星型孢菌素(STS)对蚕豆气孔运动的调控效应.结果表明:(1)光下STS对气孔开度无影响但暗中显著促进气孔开放,表明蛋白激酶参与光/暗对气孔运动的调控,光下蛋白激酶活性低而暗中高;(2)与H2O2清除剂抗坏血酸(ASA)和NO清除剂羧基-2-苯-4,4,5,5-四甲基咪唑-1-氧-3-氧化物(cPTIO)一样,STS既降低暗处理和光下外源H2O2、硝普钠(SNP)处理保卫细胞H2O2、NO水平,也促进气孔开放,表明暗中蛋白激酶通过抑制H2O2、NO清除机制提高保卫细胞内源H2O2、NO水平并促进气孔关闭.     

蚕豆监测大气SO2污染的指标筛选研究

熏气和暴露试验表明,蚕豆叶片可见伤害症状不宜作为监测指标,超氧化物歧化酶(SOD)活性、抗坏血酸(ASA)含量和游离氨基酸(AA)含量作为监测指标,其指示效果优于过氧化物酶(POD)活性和叶绿素含量,其中又以SOD活性为最好,而根据以上5个指标综合评价的效果又要优于任何单个指标。     

The influence of exogenous proline on the stomatal resistance in Vicia faba

Both the upper and lower stomata of Vicia faba responded to different concentrations of proline supplied either to the 'detached' leaves or sprayed to 'intact' leaves. The stomatal resistance of abaxial surfaces was increased more than that of the adaxial surfaces. A 1-h treatment with 5 m M proline had greater influence than a prolonged treatment. The 'young' leaves responded more than the 'mature' ones to the exogenous proline. A relationship could be demonstrated between endogenous proline, which increased markedly due to exogenous supply, and stomatal resistance.     

A combination of thidiazuron and benzyladenine promotes multiple shoot production from cotyledonary node explants of faba bean (Vicia faba L.)

A procedure for multiple shoot formation from cotyledonary node explants of faba bean (Vicia faba L.cv.S.Ghdar) cultured on MS medium containing benzyladenine (BA) and thidiazuron (TDZ) was developed. Explants on medium with TDZ in combination with BA produced a higher number of shoots than with either cytokinin alone. The highest number of shoots was obtained when explants from 7-day-old seedlings were cultured on MS medium supplemented with TDZ and BA (2 mgl–1 each) for 31 days before transfer to hormone-free MS medium for elongation. Shoots produced in vitro were rooted on half-strength agar-solidified MS basal medium or with 0.25 or 0.5 mgl–1 naphthalenacetic acid (NAA) prior to transfer to green house conditions. This procedure was found to be applicable to seven other cultivars of faba bean from widely diverse provenances. Thus, it can be advantageously applied to the production of transgenic faba bean plants.