Differential effect of various endomycorrhizal fungi on nodulating ability of green gram by Bradyrhizobium sp. (Vigna) strain S24

Bradyrhizobium sp. (Vigna) strain S24 interacted differentially with eight vesicular-arbuscular mycorrhizal (VAM) fungi and caused significant variations in nodulation and growth parameters of green gram. Coinoculation with Scutellospora calospora resulted in the highest nitrogenase activity and dry biomass. The nodulation competitiveness of strain S24 was significantly higher (60–63%) in the presence of Glomus mosseae, G. fasciculatum and Scutellospora calospora when compared to treatment with single inoculation of S24 (51%). Percentage VAM colonization was higher in treatments having higher nocule occupancy of introduced strain (S24). Received: 26 June 1995     

Effects of inoculation with N2-fixing cyanobacteria on the nitrogenase activity in soil and rhizosphere of wetland rice (Oryza sativa L.)

Summary A greenhouse experiment was conducted with wetland rice (Oryza sativa cv. IR-50) in a clay-loam soil (Fluventic Eutrochrept) to study the effect of cyanobacterial inoculation a mixed culture of Aulosira fertilissima, Nostoc muscorum, Nostoc spp., and Anabaena spp., applied at the rate of 0.15 g (dry weight pot^-1 or 43 kg ha^-1) on acetylene reduction activity in soil and the root system (excised root), and the grain and straw yield. The effects of applying P (40 kg ha^-1), N (60 kg ha^-1), and P+N to the soil were also evaluated. Cyanbacterial inoculation significantly increased (more than 200% on average) photo-dependent acetylene reduction activity in soils, particularly where the indigenous activity was considerably low, i.e. under unfertilized and N-fertilized conditions. The effect of inoculation was prominent at the maximum tillering and grain formation stages of the crop. This inoculation benefit was, however, marginal in P-applied soils (P and P+N), where the indigenous activity was stimulated more than threefold. The inoculation led to a remarkable increase in root-associative acetylene reduction activity after the maximum tillering stage of the crop, particularly with applied N but for other treatments this inoculation effect was not significant. Cyanobacterial inoculation also increased the grain and straw yield of the crop when N was not applied. The grain and straw yield was significantly correlated with the acetylene reduction activity in flooded soils and in the root system during the tillering and maximum tillering stages of rice growth, respectively.     

钴对大豆共生固态体系影响的研究

通过钴盐拌种和拌土的栽培试验表明,在施用钴的一定浓度范围内,维生素B_(12)随钴浓度提高,大豆根瘤中钴—维生素B_(12)—固氮酶活性同步提高,超过最高浓度后则表现对共生体的严重抑制,但并不降低已成熟瘤的乙炔还原活性。     

植物内生固氮菌的研究进展

植物内生固氮菌是指定殖于植物体内与宿主植物进行联合固氮的一类微生物,不但具有固氮作用,还有生物防治、促进植物生长的作用。对植物内生固氮菌的研究始于上个世纪80年代,至今已从甘蔗、水稻等多种作物中分离到多种内生固氮菌。综述了10多年来内生固氮菌的研究进展,对固氮醋酸杆菌(Acetobaterdiazotrophicus)等几种内生固氮菌的生理、生物学特性及其侵染方式、传播途径和固氮机理进行了较全面的概述,并对应用内生固氮菌的可能性和意义,以及需要注意的问题作了一些探讨。     

硝酸盐对大豆共生固氮的影响

大豆施用硝酸盐的试验结果表明,高浓度硝酸盐对吉林20号和长农4号的共生固氮有明显的抑制作用。低浓度硝酸盐在生育前期对吉林20号根瘤固氮酶活性有促进作用,酰脲含量增加,在生育后期有抑制作用。但生育前期低浓度硝酸盐对长农4号根瘤固氮酶活性有明显的抑制作用,酚脲含量减少。施用硝酸盐对大豆根瘤尿囊素酶活性都有抑制作用,生育前期比后期明显,高浓度比低浓度明显。     

大豆种子蛋白质含量与固氮酶活性和硝酸还原酶活性的关系

大豆种子蛋白质含量与根瘤的固氮酶活性和酰脲含量分别呈显著正相关和正相关,而与叶片硝酸还原酶活性呈显著负相关。     

根瘤促生剂对大豆促生结瘤的影响

研究了不同浓度根瘤促生剂对大豆植株干重、根瘤菌数量、根系活力、固氮酶活性和豆血红蛋白含量的影响.结果表明:适量浓度根瘤促生剂对大豆各项生理指标均有促进作用,浓度较高时显著抑制大豆正常生长发育,结瘤及营养吸收等功能.均表现为处理组T3(根瘤促生剂终浓度为0.143%,v/v)高于其它4组,其中T1和T4对固氮酶活性和豆血...     

磷水平和接根瘤菌对紫花苜蓿根系形态特征和根瘤固氮特性的影响

以‘甘农3号’紫花苜蓿(Medicago sativa ‘Gannong No.3’)为材料,采用营养液沙培法,研究了磷及根瘤菌对紫花苜蓿根系形态和根瘤固氮酶活性的影响,结果表明:接种根瘤菌或在一定范围内(0~2000 μmol·L^-1)提高磷水平,均可显著增加紫花苜蓿的根长、根表面积、根平均直径、根体积和根系活力,并使其根瘤数增多,根瘤重增大,固氮酶活性显著增强,植株全氮含量增加;与不接菌相比,接菌提高了紫花苜蓿对磷的需求;本试验条件下紫花苜蓿所需磷素最佳范围为1000~1500 μmol·L^-1。     

Assessment of the effects of the photosynthesis-inhibiting herbicides Diuron,DCMU, metamitron and metribuzin on growth and nitrogenase activity of Nostoc muscorum and a new cyanobacterial isolate,strain G4

Summary The influence of the photosynthesis-inhibiting herbicides Diuron, DCMU, metamitron, and metribuzin on growth and nitrogenase activity of Nostoc muscorum and a new cyanobacterial isolate, strain G4, was studied. The experiments were performed under N₂-fixing photoautotrophic conditions. Both cyanobacteria showed a high degree of tolerance towards the herbicides tested. In the presence of metamitron (35, 70, and 140 ppm) and metribuzin (7, 14, 35, and 70 ppm) strain G4 proliferated as well as the control culture. Metamitron and metribuzin had no influence on the nitrogenase synthesis of strain G4 and N. muscorum. When treated with 1 M DCMU, strain G4 and N. muscorum showed partial inhibition for the first few days, but entirely recovered during succeeding incubation. In the presence of 10 ppm Diuron, N. muscorum and strain G4, compared to the control, showed 30% and 80% nitrogenase activity, respectively.     

A rhizobial biofilm with nitrogenase activity alters nutrient availability in a soil

This study investigates the role played by a Bradyrhizobium japonicum SEMIA 5019-Penicillium spp. biofilm in terms of soil fertility, when it is free-living in a soil. The biofilm increased N and P mineralizations of the soil and showed a high nitrogenase activity even under a very high NO₃⁻ concentration in the soil, compared to its member microbes. It maintained a low SO₄²⁻ concentration in the soil, which was conducive to the high nitrogenase activity. The application of this microbial association as a biofilmed inoculum is important for sustaining soil fertility as well as survival of such rhizobia in the soil in the absence of their hosts. Further studies are needed to evaluate the performance of the biofilm in terms of soil fertility in the ecosystems.