Genetic specificity of nitrogen nutrition in leguminous plants

Summary Mineral nitrogen did not increase grain yield and seed protein levels ofVicia faba L. andLupinus luteus L. in field trials and pot experiments. Fixed N₂ was substituted by mineral nitrogen in these cases because of inhibition of N₂ fixation by mineral nitrogen. Contrary to these results mineral nitrogen increased grain yields and seed protein amounts ofLupinus albus L.,Pisum sativum L., andGlycine max. (L.) Merr. The nitrogen effect was caused at an early stage by saving energy due to inhibition of N₂ fixation (measurement of gas exchange by means of IRGA). In case of the N application after flowering grain, yields and seed protein levels increased because the mineral N was an additional nitrogen source for plants. At this stage the plants had ceased fixing atmospheric nitrogen. The high sink activity of growing fruits induced a lack of assimilates in nodules (determined by means of¹⁴CO₂ application). The N effect was therefore the consequence of the lower assimilate pool for supplying root nodules in these plants in comparison withVicia faba L. andLupinus luteus L. Hence it follows that response to mineral nitrogen can be a criterion for discovering more effective Rhizobium-host combinations.     

影响菜豆普通花叶病毒种子传毒的因素

研究了影响菜豆普通花叶病毒(BCMV)种子传毒的一些因素,不同品种,不同感染时期种子的传毒率有显著差异,苗期感病的植株,不同荚位的种子传毒率是:下部>中部>上部,花期感病者则是:中部>上部>下部,感病植株的斑驳荚种子传毒率,依品种的不同,比无斑驳荚者高3.2～9.3倍。     

Cross-inoculation specificity ofPsophocarpus tetragonolobus (L.) DC

Summary Only legumes of the cowpea cross-inoculation group, including the winged bean (Psophocarpus tetragonolobus) were found to form nodules in a temperate zone soil with no previous history of legume cropping. Isolates from root nodules from uninoculated winged beans grown in the field only nodulated legumes in the cowpea cross-inoculation group.Rhizobium japonicum formed ineffective nodules with the winged bean. Contribution No.5852, Scientific Article No.A2802 of the Maryland Agricultural Experiment Station, Department of Botany.     

Brazilian species of Calliandra Benth. (tribe Ingeae) are nodulated by diverse strains of Paraburkholderia

The Chapada Diamantina in NE of Brazil is a biodiversity hotspot and a center of radiation for many Neotropical legume genera, such as Calliandra and Mimosa. The present study aimed to evaluate nodulation in Calliandra species endemic to various environments, and to characterize the diversity of their symbiotic rhizobia using housekeeping (16S rRNA, recA) and plasmid-borne, symbiosis-related (nifH and nodC) genes. The nodulation ability of selected isolates was assessed. All of the 126 bacterial isolates from 18 Calliandra species collected in six different vegetation types were identified as Paraburkholderia according to their housekeeping and symbiosis gene phylogenies. They were grouped in seven clades in relation to the dominant vegetation type in their native environments. The majority, particularly those from highland “campo rupestre” vegetation, were similar to Paraburkholderia nodosa, but had nodC genes identical to the Mimosa symbiont Paraburkholderia tuberum sv. mimosae. The other smaller groups were related to Paraburkholderia diazotrophica and Paraburkholderia sabiae, and some single strains were not close to any known species. The symbionts of Calliandra spp. in NE Brazil are Paraburkholderia strains closely-related to Mimosa symbionts from the same region. NE Brazil is a reservoir of symbiotic Paraburkholderia that have an affinity for genera in the Mimosoid clade.     

厚荚相思根瘤菌对盆栽苗木生长及土壤肥力的影响

从不同立地条件采集到的厚荚相思根瘤分离出9株根瘤菌株,接种于厚荚相思幼茁,6个月后测定苗木生长量及土壤N、P、K含量。试验结果表明：接菌桃株的高生长量、生物量都比对照(未接种根瘤菌)增加,其巾高生长量除R2外,增加幅度为0．89～40．18％,生物量增加52．33～147．67％,接种结瘤率、瘤的生物量也比对照高,结瘤率可达100％,根瘤生物量比对照高163．6～520％。土壤N、P、K元素分析结果表明,接种根瘤菌后土壤的营养元素发生了很大的变化,改善了土壤肥力。通过对接种不同菌株的厚荚相思苗木的茁高、生物量、土壤的全氮、速效磷、速效钾等元素的含量比较分析后筛选出R6和R7菌株为优良菌株。     

Effect of some carbamate pesticides on nodulation,plant yield and nitrogen fixation byPisum sativum andVigna sinensis in the presence of their respective rhizobia

Summary Six carbamate pesticides namely 1-naphthol, sevin, dimetilan, trematan, NaDDC and dymid were studied to see their effect on nodulation and nitrogen fixation inPisum sativum andVigna sinensis. Low concentrations of the pesticides have little effect on nodulation and nitrogen fixation, whereas higher concentrations adversely effect these processes. The results also indicate that then sensitivity depends upon the species of the Rhizobium and also the type of the pesticide. Pesticides belonging to the carbamate group differ in their capacity to affect nodulation and nitroge fixation.     

根瘤菌共生固氮能力的进化模式

根瘤菌-豆科植物共生固氮体系对农业的可持续性发展至关重要,也是研究原核与真核生物互利共生的模式体系之一。长期以来,根瘤菌共生固氮相关研究主要集中在结瘤因子与固氮酶合成及调控等少数关键基因,但仅获得这些关键基因却不能保证细菌获得结瘤固氮能力。随着比较和功能基因组学的快速发展和应用,越来越多的研究发现根瘤菌使用了很多系统发育分支特异的遗传机制与豆科植物建立有效的共生关系,进一步揭示了双方互利共生的复杂性。本综述总结了近年来比较基因组学、遗传学以及实验进化等方面的相关研究进展,在此基础上讨论根瘤菌共生固氮能力的进化模式。     

Variation of the electron population by four units in the cluster series [(η-Cp′)3Mo3S4Co(L)] (L = I, CO, PPh3, NO; n = 0, 1)

The versatility of cuboidal Mo₃S₄Co clusters for the preparation of complexes with different numbers of valence shell electrons (VSE) in the cluster is described. The reaction of the geometrically incomplete cuboidal cluster salt [(η⁵-Cp′)₃Mo₃S₄][pts] (pts = p-toluenesulfonate) with one molar equivalent of [Co₂(CO)₈] afforded almost quantitatively the electroneutral 60 VSE cluster [(η⁵-Cp′)₃Mo₃S₄Co(CO)] (1), which previously has been prepared in low yield by Curtis et al. in autoclave syntheses [M.D. Curtis, U. Riaz, O.J. Curnow, J.W. Kampf, Organometallics 14 (1995) 5337]. Cluster 1 was also obtained in high yield by reaction of [(η⁵-Cp′)₃Mo₃S₄][pts] with [(η⁵-Cp^∗)Co(CO)₂]. Reaction of [(η⁵-Cp′)₃Mo₃S₄][pts] with two molar equivalents of [Co(I)(CO)₃(PPh₃)] led to a complex mixture of products, of which the electron deficient 58 VSE cluster salt [(η⁵-Cp′)₃Mo₃S₄Co(I)][Co(I)₃(thf)] ([2][Co(I)₃(thf)]) was isolated as single crystals. In the crystal structures of 1 and [2][Co(I)₃(thf)], the Co-Mo bond lengths are almost identical, indicating a delocalization of the electron deficiency in [2]⁺. The reduced form of [2]⁺, [(η⁵-Cp′)₃Mo₃S₄Co(I)] (2), was prepared by oxidative substitution of the carbonyl ligand in 1 by I₂. Further reactions of 1 with PPh₃ and NO leading to the 60 and 61 VSE cluster complexes [(η⁵-Cp′)₃Mo₃S₄Co(PPh₃)] (3) and [(η⁵-Cp′)₃Mo₃S₄Co(NO)] (4), respectively, enabled the preparation of Mo₃S₄Co clusters in altogether four different oxidation states.     

豆科树种回接根瘤菌的研究

 作者对八种豆科树种的根瘤菌回接进行了研究,不回接根瘤菌的对照植株不结瘤或有少且小的根瘤,而接菌植株的根瘤数量多且个体大;接菌植株的株高、干重及总氮量分别比不接菌的对照植株高出0.7～3.2、1.3～15.8和11.3～14.8倍。根瘤固定的氮量占幼苗生长所需氮的一半以上,固定的氮绝大部分运输到植株其它部位,分配到地上部分的氮素多于根部。固氮量与幼苗生物量显著相关。固氮作用增加了植物对磷、钾元素的吸收和积累。速生树种南洋楹(Albizia falcata)和非速生树种格木(Erythrophloeum fordii)幼苗的结瘤、固氮及生长状况较好,表现出较高的结瘤固氮潜能。     

生态条件对马占相思结瘤固氮的影响

本文研究了马占相思（Ａｃａｃｉａｍａｎｇｉｕｍ）结瘤固氮和生态条件的关系．结果显示．马占相思根瘤固氮活性的昼夜变化与固氮能源的供给有关,它受光、温影响较大,固氮活性昼夜变化的范围为１—５μｍｏｌＣ２Ｈ４·ｇ－１ｆｒｅｓｈｎｏｄｕｌｅｈ－１。固氮活性的季节性差异也很明显,且与温、湿度的变化关系密切,在温、湿度较好的５月—１０月．固氮活性较高．为３—１０μｍｏｌＣ２Ｈ４·ｇ－１ｆｒｅｓｈｎｏｄｕｌｅｈ－１．冬春的干旱和低温会影响根瘤的生长和存活．造成固氮活性降低甚至失去活性．不同年份和林地的根瘤生物量为１０４—６２５ｋｇ·ｈａ－１,以幼林期根瘤生物量较高．多数样地的根瘤生物量在３００ｈｇ·ｈａ－１以上．随着森林生态系统的发展．根系往土层深处生长以及林下草本和灌木层的增长等原因,根瘤生物量会受影响而有所下降。施肥松土能提高根瘤生物量５７—３４４ｋｇ·ｈａ－１,对增加固氮量有重大意义。     

A study of nodulation and nitrogen fixation of alder on the purplish soils in China

Summary The alder has a perennial nodule cluster. The nodule amount on the roots increases with tree age. The N₂-fixing activity of nodules decreases with nodule age. Purple coloured soils with various soil pHs and CaCO₃ contents are, in the main, the ones which influence nodulation and N₂-fixing. Higher N₂-fixing capacity existed in the neutral and low calcium soils. High calcium soils and acid soils can restrain nodulation and the N₂-fixing rate significantly. On the slope, where calcarous light loams are found, the annual nitrogen fixation capacity of alder and cypress mixed plantations, less than 10 years old, is 16 or 17 kg/ha yr, but in the valley, a pure alder plantation can reach 40 kg/ha yr.     

Does nitrogen uptake affect nitrogen uptake efficiency,or vice versa?

The aim of the paper is to enter into a discussion concerning the title question. In our opinion it is N uptake efficiency that affects N uptake, but not vice versa, mainly because the former is a genotypic characteristic, and as such is not influenced by N uptake. To support the conclusions we also show a similarity between the model used for the problem in question and a yield component model.     

Effect of two granular nematicides on growth and nodulation ofArachis hypogea L.

Summary The effect of two granular nematicidesviz. oxamyl and fenamiphos, on the nodulation and growth of Rhizobium inoculatedArachis hypogaea L. was studied in glasshouse and field trials. In the glasshouse trial at the suggested rates of application shoot fresh weight was significantly reduced by oxamyl whilst root fresh weight was similarly affected by fenamiphos. In the field trial vegetative growth and plant emergence were significantly reduced by both nematicides. Nodulation at the higher rates of application was increased by both oxamyl and fenamiphos whilst oxamyl caused a significant increase in pod number at the highest rate of application.     

The role of seed reserves in arbuscular mycorrhizal formation and growth of Leucaena leucocephala (Lam.) de Wit. and Zea mays L.

We show here that seed reserves in Leucaena leucocephala (Lam.) de Wit. and Zea mays L. (maize) are important for mycorrhizal formation and seedling growth. Seed reserve removal reduced mycorrhizal formation markedly in Leucaena but not in maize, except at 15 and 45 days after seed reserve removal. Partial or total removal of seed reserves decreased plant growth and tissue nutrient concentrations in both hosts. Nodule number in Leucaena, which was related positively to plant biomass and mycorrhizal infection levels, was reduced when one or both cotyledons were severed. Leucaena seedlings without or with partial seed reserves had higher nutrient use efficiencies throughout seedling growth. But such an effect was observed only initially in maize. Seed reserve removal increased the specific absorption rates of nutrients in both hosts. Phosphorus absorption rate was significantly and positively related to root infection levels in both Leuceana and maize. Though the growth rates of plants without seed reserves were low initially, these plants had higher growth rates during later stages. We conclude that seed reserves are not only important for seedling growth, but also for mycorrhizal formation and nodulation. Received: 15 July 1999 / Accepted: 6 December 1999     

Micro-morphology of common bean (<Emphasis Type=Italic>Phaseolus vulgaris</Emphasis> L.) nodules undergoing senescence

We studied morphological changes over time by nodules formed on the root system of the common bean (Phaseolus vulgaris L.). Two cultivars, Bayomex and Cacahuate 72 with growth habit Type I and the Rhizobium etli strain CE-3 were used. The results showed the collapse of the infected zone, degradation of the cell walls and membranes, changes in the number and distribution of the starch granules, appearance of protein granules, and disintegration of the central tissue of the nodule with ageing. Additionally, we describe the influence of time on the progress of the nodular senescence.     

大明绿系选后代遗传多样性与高产特征分析

以内蒙古中东部地区61份绿豆品种大明绿系选后代为研究材料,通过对农艺性状的多样性及通径分析,明确了后代品系遗传类型及高产群体性状特征。结果表明,大明绿后代品系间性状差异显著,单株荚数变异系数最大为31.61%,其次为单株粒重28.05%,遗传多样性较丰富,多样性指数为单株荚数2.02,每荚粒数2.01,百粒重1.89,单株粒重1.96。后代品系主要有6种类型,各性状对单株粒重影响大小依次为:单株荚数>每荚粒数>百粒重>节数>株高。高产类型品系主要特征指标为单株粒重超过15 g,单株荚数超过30荚,每荚粒数8~10粒,株高48~60 cm,节数9~10节,百粒重可根据不同需求制定标准。