珠芽蓼内生固氮菌鉴定及其固氮基因分析

从东祁连山高寒草地采集优势植物珠芽蓼(Polygonum viviparum)并对其内生固氮细菌进行分离、筛选和鉴定。结果表明:从珠芽蓼内分离到14株内生细菌,其中Z22、Z24、Z25、Z27、Z28、Z211、Z214共7株内生细菌具有固氮能力,对菌株Z22的固氮基因(nifH)进行了PCR扩增、测序和系统发育分析,并在GenBank中登录(登录号为EU693342);Z22菌体球形,革兰氏阳性,产芽孢,结合生理生化特征及16SrDNA基因序列测定和同源性分析,鉴定其为球形芽孢杆菌(Bacillus sphaericus),该菌株的16SrDNA序列在GenBank中登录(登录号为EU236749)。本文首次获得了球形芽孢杆菌编码铁蛋白的nifH基因序列。     

兴安岭落叶松生长过程中的固碳模型研究

通过研究兴安岭落叶松树高、胸径与树龄的关系、生物量与D2H的关系及树种含碳率,建立了评估该树种固碳能力的模型。     

花生根瘤菌固氮机理研究进展

综述了根瘤菌分类,影响根瘤固氮机制的因素、根瘤菌及其宿主基因型的遗传改良与筛选,提出了花生根瘤菌应用存在问题及研究对策。     

Estimation and Partitioning of Nitrogen Fixed by Soybean in Mediterranean Climates

A field study was conducted to estimate the nitrogen fixation by soybean [ Glycine max (L.) Merr.], using the A-value and the N-difference methods, and to examine the N partitioning within the plant. The cultivar Clark and its non-nodulating isoline (as reference crop) were grown in a silty clay (Typic Xerothent) soil, in 1991 and 1992. ₁₅N-Labelled fertilizer was surface applied in solution, at rates of 20 and 100 kg N ha⁻¹ to the nodulating and non-nodulating soybean, respectively. Plant samples were taken at full bloom (R2), beginning of seed growth (R5) and physiological maturity (R7). There was little nitrogen fixation at the early growth stages but it increased rapidly during the seed filling period. At R7 nitrogen fixed was estimated by the A-value method as 155 kg N ha_-1 in 1991 and as 240 kg N ha⁻¹ in 1992. The corresponding estimates by the N-difference method were significantly smaller. The seeds had a higher, and the vegetative parts smaller, proportion of fixed nitrogen compared to the whole plant. During the seed filling period, the translocation efficiency for fixed nitrogen was greater (93 % in 1991 and 85 % in 1992) compared to the N derived from soil (75 and 56 %, respectively). It was estimated that, after the harvest of pods, the soil was depleted by a net amount of 121 kg N ha⁻¹ in 1991 and 90 kg N ha⁻¹ in 1992.     

诱导固氮菌与稻苗结瘤共生的研究

以植物生长激素２,４－Ｄ处理非豆科植物稻苗并接种固氮菌,诱导固氮菌与幼苗结瘤（类瘤）共生．多次重复实验结果如下：不同稻品种的始瘤日期、结瘤率及固氮酶活性有所差异．在１２个供试品种中,始瘤期需３～１２ｄ;结瘤率为２０．５％～１００％;固氮酶活性（乙炔还原法）最高的达７７．６ｎｍｏｌ株－１ｄ－１．稻苗经２,４－Ｄ处理后接种弗兰克氏菌,取得与根瘤菌相似结果．这是弗兰克氏菌应用于农作物的首次报道．固氮菌与稻苗共生固氮有促进生长、延缓衰老的作用．本研究揭示了根瘤菌与禾本科作物之间的一种新的共生关系,对研究非豆科作物结瘤固氮将是很有意义的．     

弗兰克氏菌的研究进展与前景

弗兰克氏菌（Ｆｒａｎｋｉａ）与植物共生结瘤固氮的意义不亚于豆科植物的根瘤菌,并有更广阔的研究开发前景．本文简要介绍了弗兰克氏菌的研究历史;着重评述了弗兰克氏菌的宿主种类、菌种分类、固氮数量、适应范围、固氮特性、新共生体系和侵染作物等的研究进展;并对弗兰克氏菌的进一步研究开发提出思路和展望     

Identification and characterization of salt- and thermo-tolerant Leucaena-nodulating Rhizobium strains

 Rhizobium-legume symbioses are important for their nitrogen input, but salinity and elevated temperature in arid and semi-arid areas limit their effectiveness, and therefore plant growth and productivity. Sixteen Rhizobium strains isolated from root nodules of Leucaena trees grown in different geographical areas of Egypt varied in their degree of tolerance to salinity and in their symbiotic effectiveness with Leucaena leucocephala under saline conditions. Three strains were tolerant to >3% NaCl. L. leucocephala grown in the greenhouse at concentrations of NaCl up to 1.0% and inoculated either with strain DS 78 or strain DS 158 displayed significantly better growth than those plants grown at the same levels of salinity and inoculated with reference strain TAL 583. Although nine of the Rhizobium strains grew at 42  °C, their mean generation times were lengthened two- to fourfold. When daylight growth temperatures were elevated from 30  °C to 42  °C, nodule number and mass, nitrogenase activities and shoot top dry weight of plants inoculated with strains DS 78, DS 157 and DS 158 significantly increased, whereas these parameters decreased in plants inoculated with strain TAL 583. Rhizobium strains that effectively nodulate Leucaena under adverse saline conditions and at high temperatures were thus isolated, identified and characterized. Received: 12 September 1997     

Nodulation pattern and acetylene reduction (nitrogen fixation) activity of some highland and lowland Acacia species of Ethiopia

 Endosymbionts from the Ethiopian highland acacia species Acacia abyssinica, A. negrii and A. etbaica, and the lowland species A. nilotica, A. prasinata, A.senegal, A. seyal, A. tortilis and Faidherbia (Acacia) albida were isolated and characterized. Seven tree species were found to be nodulated by species of both Rhizobium and Bradyrhizobium. F. (Acacia) albida and A. senegal were nodulated by only Bradyrhizobium or Rhizobium, respectively. In A. abyssinica, both genera were isolated from the same nodule, whereas in A. nilotica and A. tortilis, both strains were isolated from different nodules of the same plant. The nitrogen fixation (acetylene reduction) activities varied considerably and showed no correlation with the nitrogen content of the plant. Highland species were as effective as lowland plants, thus demonstrating good potential for soil reclamation. The endosymbionts isolated proved rather promiscuous, efficiently nodulating other Acacia spp. and some tropical grain legumes, but did not nodulate temperate legumes. Received: 7 August 1997     

Soybean Cultivation on Desert Sand Using Drip Irrigation with Mulch

Abstract

The growth and yield potential of soybean and the effects of mulching on desert sand were evaluated in relation to N accumulation in nodules. The experiment was conducted in concrete framed plots filled with sand obtained from the Dzungar desert or the normal field soil in Shihezi, Xinjiang, China. Drip irrigation with or without mulch was adopted for the experimental plots. The mean soil temperature in the sand plot with mulch was the highest among the plots during the early growth stages. The relative ureide-N content in the soil plots varied from 23.2% at the full flowering stage (R2) to 37.6% at the beginning of the maturity stage (R7). The sand plots showed higher values than the soil plots ranging from 48.7% at R2 to 80.5% at R7, indicating active N₂ fixation by nodules. Seed yield did not show a significant difference between the soil and the sand plots. It ranged from 394 g m^?2 in the soil plot without mulch to 472 g m^?2 in the sand plots with mulch. The results suggested the possibility of extending soybean cultivation into marginal areas of deserts, provided that adequate water was available for drip irrigation and there was active nodulation.     

Characterization of Drought‐Tolerance Traits in Nodulated Soya Beans: The Importance of Maintaining Photosynthesis and Shoot Biomass Under Drought‐Induced Limitations on Nitrogen Metabolism

Drought is the single most important factor limiting soya bean (Glycine max L. Merr.) yields in the field. The following study was therefore undertaken to identify phenotypic markers for enhanced drought tolerance in nodulated soya beans. Leaf and nodule parameters were compared in three genotypes: Prima 2000, glyphosate‐resistant A5409RG and Jackson, which had similar shoot biomass and photosynthesis rates at the third trifoliate leaf stage under water‐replete conditions. When water was withheld at the third trifoliate leaf stage, photosynthesis, nodule numbers, nodule biomass and symbiotic nitrogen fixation (SNF) were greatly decreased. Significant cultivar–drought interactions were observed with respect to photosynthesis, which also showed a strong positive correlation with nodule SNF, particularly under drought conditions. Prima leaves had high water‐use efficiencies, and they also maintained high photosynthetic electron transport efficiencies under long‐term drought. Moreover, Prima had the highest shoot biomass under both water‐replete and drought conditions. A‐5409RG was the most drought‐sensitive genotype showing early closure of stomata and rapid inhibition of photosynthesis in response to drought. In addition to classifying the genotypes in relation to drought tolerance, the results demonstrate that the ability to sustain shoot biomass under nitrogen limitation is an important parameter, which can be easily applied in germplasm screening for drought tolerance in soya bean.