辽宁省豆科结瘤植物及其根瘤菌资源调查

豆科植物作为一种共生固氮植物 ,能与根瘤菌共生结瘤固定大气中的氮素 ,因此受到科学家的广泛关注 ,并对其开展了多方面的研究工作。在固氮机理 ,共生代谢及固氮菌遗传学方面都取得了重要的进展。但是 ,已经被研究的与根瘤菌具有共生关系的豆科植物还不足自然界中已知豆科植物种类的 0 5% [1 ] ,因此 ,豆科结瘤植物及其根瘤菌资源的调查研究工作更显得尤为重要。辽宁省是我国豆科植物种类较为丰富地区之一[2～6] ,而且均为我国主要的经济作物 ,如大豆、菜豆、豇豆、落花生等。多年来人们在不断地利用这些豆科植物资源造福于人类。但是 ,对…     

新疆地区结瘤固氮的豆科植物调查

世界上有豆科植物748属19700种,据报告在研究过的365属3108种豆科植物中,实际结瘤的豆科植物为2839种。新疆为典型的内陆干旱地区,分布着47属400种豆科植物,是新疆植被中主要类群之一,为干旱区生态体系中有效氮的主要     

固氮植物的菌根研究

综述了固氮植物菌根研究的概况,并对固氮植物形成菌根的普遍性,固氮植物联合共生的增效作用及逆境条件下菌根技术在固氮植物上的应用前景进行了总结和评述,初步探讨了联合共生体中菌根菌促进固氮植物结瘤固氮的机理。     

豆科茎瘤植物的结瘤,固氮和应用（综述）

本文概述了豆科茎瘤植物的某些特性,其结瘤数量殉,固氮能力强,抗涝,耐酸碱,耐铵,可用于改土培肥,文中学论述了毛萼田菁等绿肥植物在水稻田中的应用。     

几种豆科树木结瘤固氮的初步研究

 作者通过野外调查和盆栽试验,探讨了几种豆科树种的结瘤固氮特征,土壤条件的影响和植株生长。木豆、山毛豆、刺槐在南亚热带褐红土种植,山合欢、刺槐在中亚热带紫色土种植,对绿化荒山荒地、改良土壤和促进生态平衡具有重要意义。     

豆科茎瘤植物的结瘤、固氮和应用(综述)

本文概述了豆科茎瘤植物的某些特性,其结瘤数量多,固氮能力强,抗涝,耐酸碱,耐铵,可用于改土培肥。文中还论述了毛萼田菁等绿肥植物在水稻田中的应用。     

河西走廊豆科植物结瘤固氮特性初步研究

对甘肃河西走产野生豆科植物结瘤及固氮状况进行了调查。栽培豆科植物均能自然结瘤,野生豆科植物结瘤率仅５０％。该地区豆科植物根瘤大多数圆形、棒状或指状,形状较为规则。栽培植物根瘤多为粉红色,而野生揿为白色、黄色或棕色。ＡＲＡ测定表明,２５．６％根瘤为无效根瘤。不同种不同地区根瘤固氮活性相差较大,一般活力都较低,乙炔还原活性小１μｍｏｌＣ２Ｈ４／ｇＦＷ．ｈ的占检测样品数的２９．９％,最高者信为２８．１９     

豆科黄华族植物地理学的初步研究

在系统学业伦和地理分布及古植物学资源的基础上,利用形态－地理学的原理和方法,对豆科Papilionaceae黄华族和Tribe Thermopsideae进行了植物地理学的初步研究。结果表明,（１）黄华族可能是古地中海起源的,它的起源地在古北大陆的南岸,大约相当于现在的中纬度地区;（２）起源时间能早于第三纪,大约处白垩纪末和始新世之间。当时有一个所谓的“北热带植物群”Ｂoreotropical Flora发生;（３）本族６个属基本上构成一个比较自然的单元。它们是由原始槐族类祖先演化而来的;（４）木本类是本族原始的,早出的类群,它们基本上处于遗状态;草本类是本族进化的、晚出的类群,们种类多,分布区有扩大的趋势;（５）Ｔhermopsis间断分布于亚洲（包括中亚和东亚）、北美（包括北美东部和北美西部。东亚太平洋沿岸和北美大西洋沿岩最有可能是它的原始保存地,而不是起源地,它们主要是通过古地中海海道而发生联系的,造成原始类群星散分布的格局不是由一次,而是多次地史和气候变化的结果;（６）晚第三纪亚洲腹地造山运动引起的喜马拉雅山的降起和青藏高原的抬升,以及北美落基山山体抬升引起的水温条件的急剧变化是某些类群（包括Piptanthus和Thermopsis)物种局部分化的主要动力。     

Analysis of the legume-rhizobia symbiosis in shrubs from central western Spain

AIMS: This work analyses the diversity of rhizobia associated with some of the predominant shrubby legumes in central-western Spain. Symbiotic promiscuity and effectiveness were studied using cross-inoculation experiments with shrubby species. MATERIAL AND RESULTS: Six new bradyrhizobia strains were isolated from nodules collected from wild plants of six leguminous species, Cytisus balansae, C. multiflorus, C. scoparius, C. striatus, Genista hystrix and Retama sphaerocarpa. These isolates were genetically characterized by 16S rDNA partial sequencing and random amplification of polymorphic DNA-PCR fingerprinting. The phylogenetic analysis revealed that these isolates could represent three new Bradyrhizobium species. Shrubby legumes and bradyrhizobia displayed a high symbiotic promiscuity both for infectivity and effectiveness. Symbioses were effective in more than 70% of the associations established by four of the six plant species. CONCLUSIONS: Native woody legumes in western Spain are nodulated by Bradyrhizobium strains. The high degree of symbiotic promiscuity and effectiveness highlights the complex dynamics of these communities in wild ecosystems under a Mediterranean-type climate. Furthermore, the results from this study suggest a potential importance of inoculation for these legume species in soil-restoration projects. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study, to our knowledge, that combines both molecular analysis and pot trials to study the rhizobia-legume symbiosis for wild legumes.     

Large Loss of Dissolved Organic Nitrogen from Nitrogen-Saturated Forests in Subtropical China

Dissolved organic nitrogen (DON) has recently been recognized as an important component of terrestrial N cycling, especially under N-limited conditions; however, the effect of increased atmospheric N deposition on DON production and loss from forest soils remains controversial. Here we report DON and dissolved organic carbon (DOC) losses from forest soils receiving very high long-term ambient atmospheric N deposition with or without additional experimental N inputs, to investigate DON biogeochemistry under N-saturated conditions. We studied an old-growth forest, a young pine forest, and a young mixed pine/broadleaf forest in subtropical southern China. All three forests have previously been shown to have high nitrate (NO₃⁻) leaching losses, with the highest loss found in the old-growth forest. We hypothesized that DON leaching loss would be forest specific and that the strongest response to experimental N input would be in the N-saturated old-growth forest. Our results showed that under ambient deposition (35–50 kg N ha⁻¹ y⁻¹ as throughfall input), DON leaching below the major rooting zone in all three forests was high (6.5–16.9 kg N ha⁻¹ y⁻¹). DON leaching increased 35–162% following 2.5 years of experimental input of 50–150 kg N ha⁻¹ y⁻¹. The fertilizer-driven increase of DON leaching comprised 4–17% of the added N. A concurrent increase in DOC loss was observed only in the pine forest, even though DOC:DON ratios declined in all three forests. Our data showed that DON accounted for 23–38% of total dissolved N in leaching, highlighting that DON could be a significant pathway of N loss from forests moving toward N saturation. The most pronounced N treatment effect on DON fluxes was not found in the old-growth forest that had the highest DON loss under ambient conditions. DON leaching was highly correlated with NO₃⁻ leaching in all three forests. We hypothesize that abiotic incorporation of excess NO₃⁻ (through chemically reactive NO₂⁻) into soil organic matter and the consequent production of N-enriched dissolved organic matter is a major mechanism for the consistent and large DON loss in the N-saturated subtropical forests of southern China. Dr. YT Fang performed research, analyzed data, and wrote the paper; Prof. WX Zhu participated in the initial experimental design, analyzed data, and took part in writing the paper; Prof. P Gundersen conceived the study and took part in writing; Prof. JM Mo and Prof. GY Zhou conceived study; Prof. M Yoh analyzed part of the data and contributed to the development of DON model.     

南亚热带森林演替过程中土壤线虫群落结构变化

森林演替会通过改变植物群落组成和土壤环境影响土壤生物群落, 反过来, 土壤生物群落的变化也会对生态系统的演替产生反馈作用, 但迄今南亚热带森林演替过程中土壤生物群落的变化特征尚不清晰。本研究以广东省鼎湖山的南亚热带森林演替序列(马尾松(Pinus massoniana)林-针阔叶混交林-季风常绿阔叶林)为对象, 研究了森林演替过程中土壤线虫多样性和群落结构的动态变化及其影响因素。通过采集不同演替阶段的土壤样品, 分析和比对了不同演替阶段土壤线虫的多度、多样性、群落组成、土壤线虫生态指数以及土壤理化性质的差异。结果表明: (1)在南亚热带森林演替过程中, 针阔叶混交林和季风常绿阔叶林土壤线虫的α多样性显著高于马尾松林, 但土壤线虫总数和各营养类群多度及其相对丰度并无显著变化; (2)针阔叶混交林中土壤线虫富集指数显著高于马尾松林, 表明其土壤养分状况要好于马尾松林, 而季风常绿阔叶林土壤线虫结构指数较高, 表明其受干扰程度较低; (3)针阔叶混交林的土壤含水量和土壤理化性质(除土壤总磷含量)已达到季风常绿阔叶林的水平, 但两者的土壤pH值均显著低于马尾松林, 而土壤pH值和土壤含水量是影响土壤线虫群落动态变化的主要因素。综上所述, 南亚热带森林中土壤线虫多度、多样性和群落结构对森林演替的响应略有不同, 演替过程中土壤环境因素的趋同是导致针阔叶混交林和季风常绿阔叶林中土壤线虫多样性和群落特征相似的主要原因。     

Legume species identity and soil nitrogen supply determine symbiotic nitrogen-fixation responses to elevated atmospheric [CO2

In nitrogen (N)-limited systems, the response of symbiotic N fixation to elevated atmospheric [CO2] may be an important determinant of ecosystem responses to this global change. Experimental tests of the effects of elevated [CO2] have not been consistent. Although rarely tested, differences among legume species and N supply may be important. In a field free-air CO2 enrichment (FACE) experiment, we determined, for four legume species, whether the effects of elevated atmospheric [CO2] on symbiotic N fixation depended on soil N availability or species identity. Natural abundance and pool-dilution 15N methods were used to estimate N fixation. Although N addition did, in general, decrease N fixation, contrary to theoretical predictions, elevated [CO2] did not universally increase N fixation. Rather, the effect of elevated [CO2] on N fixation was positive, neutral or negative, depending on the species and N addition. Our results suggest that legume species identity and N supply are critical factors in determining symbiotic N-fixation responses to increased atmospheric [CO2].     

Mutation breeding of grain legumes

Genetic variation among existing cultivars and in germplasm collections is the outcome of selection during evolution and plant breeding. Mutagenesis offers the plant breeder a chance to tackle unconventional objectives, particularly those that were at a selection disadvantage in the past. Effective mutagens are available, but the bottleneck is the effective selection of rare desired variants from large mutagenized populations. Selection methods must be non-destructive. Grain legume mutation breeding has already led to improved cultivars with higher yield, better grain quality, or stronger resistance to pathogenens. Many mutations affecting nitrogen fixation related traits have also been reported. Some could be useful in breeding better cultivars, but the majority are being used to study the factors interacting in the complex process of symbiotic nitrogen fixation and to improve the strategy for producing cultivars with better fixation capacity.     

Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems

An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry. Published as Paper No. 9950, Journal Series, Nebraska Agricultural Research Division, University of Nebraska, Lincoln, NE, USA.     

Evolving ideas of legume evolution and diversity: a taxonomic perspective on the occurrence of nodulation

Legumes evolved about 60 million years ago (Ma), and nodulation 58 Ma. Nonnodulation remains common in Caesalpinioideae, with smaller numbers in Mimosoideae and Papilionoideae. The first type of infection by bacteria may have been at junctions where lateral roots emerged, followed by formation of infection threads to confine bacteria and convey them to some cells in the developing nodule, where they were generally released into symbiosomes. Infection threads were a prerequisite for root-hair infection, a process better controlled by the host, leading to a higher degree of specificity between symbionts. An alternative process, dating from the same time and persisting in about 25% of legumes, did not involve infection threads, bacteria entering a few host cells, surrounded by an undefined matrix. These cells divided repeatedly to give uniform infected tissue, with bacteria released into symbiosomes. Such legumes may have less stringent control of nodulation processes, and are found mainly in tropical and warm temperate areas. In each type of nodule, meristems may or may not be retained, leading to indeterminate or determinate forms. Nodule morphology and structure are host-determined, but the effectiveness of nitrogen fixation is largely controlled by the bacterial symbionts, which vary greatly in genotypic and phenotypic characters.     

Factors regulating the contributions of fixed nitrogen by pasture and crop legumes to different farming systems of eastern Australia

On-farm and experimental measures of the proportion (%Ndfa) and amounts of N₂ fixed were undertaken for 158 pastures either based on annual legume species (annual medics, clovers or vetch), or lucerne (alfalfa), and 170 winter pulse crops (chickpea, faba bean, field pea, lentil, lupin) over a 1200 km north-south transect of eastern Australia. The average annual amounts of N₂ fixed ranged from 30 to 160 kg shoot N fixed ha^–1 yr^–1 for annual pasture species, 37–128 kg N ha^–1 yr^–1 for lucerne, and 14 to 160 kg N ha^–1 yr^–1 by pulses. These data have provided new insights into differences in factors controlling N₂ fixation in the main agricultural systems. Mean levels of %Ndfa were uniformly high (65–94%) for legumes growing at different locations under dryland (rainfed) conditions in the winter-dominant rainfall areas of the cereal-livestock belt of Victoria and southern New South Wales, and under irrigation in the main cotton-growing areas of northern New South Wales. Consequently N₂ fixation was primarily regulated by biomass production in these areas and both pasture and crop legumes fixed between 20 and 25 kg shoot N for every tonne of shoot dry matter (DM) produced. Nitrogen fixation by legumes in the dryland systems of the summer-dominant rainfall regions of central and northern New South Wales on the other hand was greatly influenced by large variations in %Ndfa (0–81%) caused by yearly fluctuations in growing season (April–October) rainfall and common farmer practice which resulted in a build up of soil mineral-N prior to sowing. The net result was a lower average reliance of legumes upon N₂ fixation for growth (19–74%) and more variable relationships between N₂ fixation and DM accumulation (9–16 kg shoot N fixed/t legume DM). Although pulses often fixed more N than pastures, legume-dominant pastures provided greater net inputs of fixed N, since a much larger fraction of the total plant N was removed when pulses were harvested for grain than was estimated to be removed or lost from grazed pastures. Conclusions about the relative size of the contributions of fixed N to the N-economies of the different farming systems depended upon the inclusion or omission of an estimate of fixed N associated with the nodulated roots. The net amounts of fixed N remaining after each year of either legume-based pasture or pulse crop were calculated to be sufficient to balance the N removed by at least one subsequent non-legume crop only when below-ground N components were included. This has important implications for the interpretation of the results of previous N₂ fixation studies undertaken in Australia and elsewhere in the world, which have either ignored or underestimated the N present in the nodulated root when evaluating the contributions of fixed N to rotations.     

Investigations on decomposition of foliage of woody species using a perfusion method

The time for half of the total oxidizable carbon to be converted into CO₂ and other gaseous products (t_1/2) was studied for five tree species used in agroforestry. The study was conducted in a perfusion system with continuous aeration, and moisture content maintained at field capacity. This method was found to be suitable for studies of the initial stages of tree foliage decomposition. The overall rate was in the decreasing order: Leucaena>Calliandra>Gliricidia>Prosopis>Cassia. Decomposition started rapidly and then decreased rapidly for 2 to 3 weeks followed by a gradual decrease which continued for the remainder of the time.The time for 50 per cent of total oxidizable carbon to decompose was about 19 days for Leucaena, 30 days for Calliandra and Gliricidia, while Prosopis and Cassia took more than 30 days. Leucaena released the largest quantity of total N into the perfusing solution while Cassia gave the lowest amount.