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1.
Summary The rate of H2 release from broad beans (Vicia faba) infected with Rhizobium leguminosarum Hup- was much faster than from beans infected with the Hup+ strain. Acetylene reduction and H2 release were abolished by cutting the plants down, by incubation in darkness, or after the addition of ammonium, indicating that the H2 was released by N2-fixing bacterial symbionts. In laboratory cultures using non-sterile soil, the bean plants released H2 until an equilibrium between H2 production and H2 oxidation was reached. The H2 equilibrium concentration was higher in Hup--infected bean cultures (about 3 ppm H2 in the gas phase) than in Hup+-infected cultures (0.3 ppm H2) because of the higher H2 production. The H2 release from Hup--infected bean cultures in sterile soil did not reach equilibrium. An equilibrium occurred, if Knallgas bacteria were added. However, the equilibrium value was higher (13 ppm H2) than in non-sterile soil, which seemed to be more efficient at H2 oxidation. The Knallgas bacteria exhibited a relatively high K m for H2 (> 1300 ppmv H2); this activity was observed in unplanted non-sterile soil, and in nonsterile soil planted with Hup+-infected beans or planted with Hup--infected beans which had been cut down before being assayed. All these soils also showed a second, low-K m (<50 ppm) level of H2 oxidation activity, which was presumably due to abiontic soil enzymes. In contrast, only one level of activity, which had an intermediate K m (about 200 ppm H2), was observed when the soil was planted with Hup--infected beans. The origin of this activity, which was only observed in the presence of intact, H2-producing beans, is still unknown.  相似文献   

2.
Summary The response of the cotton plant to inoculation with six strains of Azospirillum brasilense was investigated under subtropical conditions in Egypt. Azospirilla populations and activities were increased as a result of root inoculation with liquid inoculum of Azospirillum sp. Highest C2H2 — reduction activities on roots were obtained with strains S631 and Sp Br 14 (means of 216.85 and 209.50 nmol C2H4g–1 root h–1 respectively) while strain M4 gave the lowest activity (mean of 100.8 nmol C2H4g–1 root h–1). Statistical analysis showed that Azospirillum strains 5631, Sp Br 14, E15 and SC22 significantly increased the plant dry weight and nitrogen uptake while inoculation with strains M4 and SE had no significant effect in that respect.  相似文献   

3.
Strains of Rhizobium tropici IIB, CIAT899 and F98.5, both showing good N2 fixation, and a R. etli strain W16.3SB were introduced into a field which had no history of bean culture. Plant dilution estimates showed that in the presence of its host (Phaseolus vulgaris cv. Carioca) during the cropping seasons and the subsequent fallow summer periods, the bean rhizobial populations increased from less than 30 to 103 g–1 dry soil after 1 year and to 104 g–1 dry soil after 2 years. In the 1st year crop, the inoculated strains occupied most of the nodules, which resulted in a higher nodulation and C2H2 reduction activity. Without reinoculation for the second and third crops, however, little R. tropici IIB was recovered from the nodules and the bean population consisted mainly of R. etli, R. leguminosarum bv. phaseoli, and R. tropici IIA. Reinoculation with our superior R. tropici IIB strains before the second crop resulted in R. tropici IIB occupying the main part of the nodules and a positive effect on nodulation and C2H2 reduction activity, but reintroduction of the inoculant strain in the third season did not have any effect.  相似文献   

4.
Rhizobitoxine (2-amino-4-(2-amino-3-hydropropoxy)-trans-but-3-erioic acid) is a phytotoxin produced by some strains of Bradyrhizobium species. Rhizobitoxine-producing strains often induce chlorosis in new leaves of soybean as a result of the synthesis of the toxin in nodules (Owens and Wright 1964; Owens et al. 1972). Some of the B. japonicum bacteroids possessing the hydrogen uptake (Hup) system are capable of ATP production by recycling H2 evolved from nitrogenase (Evans et al. 1987). Adequate uptake hydrogenase activity in soybean bacteroids often enhances plant growth, as well as the efficiency of energy utilization during nitrogen fixation (Evans et al. 1987).  相似文献   

5.
Summary Bradyrhizobial strain BTAi 1 nodulates both stems and roots of Aeschynomene spp. Previous work has shown that it contains bacteriochlorophyll a and forms photosynthetic reaction centers, and has provided indirect evidence of photosynthesis by bacteroids within stem nodules. Here we report physiological and biochemical characteristics of BTAi 1 ex planta, which also suggest the presence of photosynthetic activity. Light-stimulated uptake of 14CO2 by BTAi 1 was detected at all stages of growth. Inhibitors of photosynthesis, 1,10-orthophenanthroline and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and the uncoupler NH4Cl, immediately suppressed light-driven 14CO2 uptake and increased O2 uptake. BTAi 1 is strictly aerobic and was unable to grow without organic C even in the light; also, it was unable to grow chemoautotrophically in an atmosphere enriched with H2 and CO2. In micro-aerobic conditions, strain BTAi 1 expressed acetylene reducing activity ex planta in an N-free medium. The highest rates of light-stimulated 14CO2 uptake and acetylene-reducing activity occurred during the exponential and early stationary phases of growth. Acetylene-reducing rates at a low glucose concentration were increased following a light-dark cycle in comparison with continuous dark conditions.  相似文献   

6.
Summary The nitrogen metabolism of wheat plants inoculated with various Azospirillum brasilense strains and nitrate reductase negative (NR–) mutants was studied in two monoxenic test tube experiments. The spontaneous mutants selected with chlorate under anaerobic conditions with nitrite as terminal electron acceptor fixed N2 in the presence of 10 mM NO3 – and were stable after the plant passage. One strain (Sp 245) isolated from surface-sterilized wheat roots produced significant increases in plant weight at both NO3 levels (1 and 10 mM) which were not observed with the NR– mutants or with the two other strains. Similar effects were observed in a pot experiment with soil on dry weight and total N incorporation but only at the higher N fertilizer level. In the monoxenic test tube experiments plants inoculated with the mutants showed lower nitrogenase activities than NR+ strains at the low NO3 – level (1 = mM) but maintained the same level of activity with 10 mM NO3 – where the activity of all NR+ strains was completely repressed. The nitrate reductase activity of roots increased with the inoculation of the homologous strains and with the mutants at both NO3 – levels. At the low NO3 – level this also resulted in increased activity in the shoots, but at the high NO3 – level the two homologous strains produced significantly lower nitrate reductase activity in shoots while the mutants more than doubled it. The possible role of the bacterial nitrate reductase in NO3 – assimilation by the wheat plant is discussed.  相似文献   

7.
Seventeen strains of Rhizobium leguminosarum biovar viceae specific to the lentil (Lens culinaris L.) were screened, using the high-yielding lentil cultivar L 4076, for their tolerance to three levels of NO inf3 sup- : 0, 4, and 8 mM NO inf3 sup- . Preliminary screening of this symbiosis for nodulation and N fixation in the presence of NO inf3 sup- showed significant variations among the strains. The number of nodules decreased and nitrogenase activity was depressed in all strains in the presence of NO inf3 sup- . Strains L-1-87, L-27-89, L-33-89, and L-40-89 tolerated 8 mM NO inf3 sup- . Four strains, three tolerant of NO inf3 sup- (L-1-87, L-27-89, and L-33-89), and one sensitive (L-11-89) to NO inf3 sup- , were selected from preliminary screening and used in a pot experiment to assess the symbiosis in the presence of 6 mM NO inf3 sup- at three stages of plant growth, viz., 40 days, 60 days, and at the final harvest. In general, the weight of nodules and C2H2 reduction activity was significantly higher after 60 days than after 40 days. Inoculation with strain L-1-87 produced the maximum number of nodules, and root and shoot biomass both in the presence and the absence of NO inf3 sup- . Nitrate reductase activity in the tops and nodules was assayed only after 60 days and did not show significant variations among strains and NO inf3 sup- treatments. The grain yields for all strains except L-11-89 were significantly higher in the presence of NO inf3 sup- than in the absence of NO inf3 sup- , indicating that tolerant strains contributed symbiotically fixed N to the plant's N pool, resulting in an additive effect on yield. Inoculation with strain L-1-87 produced the maximum grain yield and this strain appears to have potential use as an inoculant in the presence of high levels of soil N.  相似文献   

8.
Summary Differences between isogenic uptake hydrogenase (HUP) mutants of Bradyrhizobium japonicum in terms of nodule efficiency, N2 fixation and N incorporation into various plant parts were studied in a monoxenic greenhouse experiment in order to confirm previous results with soybeans and beans inoculated with various HUP+ and HUP– strains. The HUP+ revertant PJ17-1 of a HUP– mutant (PJ17) of strain USDA DES 122 showed a completely restored relative efficiency (100% versus 78±2% for the HUP– mutant), higher nodule efficiency (N2 fixed per g nodules), higher ureide-N transport rates, higher N contents in pods and higher N harvest indices. All these observations confirm previous experiments with HUP+ and HUP– strains.  相似文献   

9.
Summary In an experiment performed under greenhouse conditions, four cultivars of Phaseolus vulgaris L. (Venezuela-350; Aroana; Moruna; Carioca) were inoculated with three Rhizobium leguminosarum biovar phaseoli strains (C-05; C-40 = CIAT 255; C-89 = CIAT 55) and were fertilized with an N-free mineral nutrient solution. The plants were harvested 25, 40, and 55 days after emergence and the following paramenters were evaluated: Nitrogenase activity of nodulated roots, H2 evolution by the nodules; relative efficiency of nitrogenase; respiration rates of nodulated roots and detached nodules; dry weight and total N of stems, leaves, pods, roots, and nodules. Generally the bean cultivar, Rhizobium strain, had an effect and there was an interaction effect with both symbiotic partners, on all parameters. On average, nodules represented 23% of total root respiration but the best symbiotic combinations showed lower ratios of C respired to N fixed. The maximum N-assimilation rate (between 40 and 55 days after emergence) of 11.93 mg N plant–1 day–1 occurred with the symbiotic combination of Carioca × C-05, while the poorest rate of 0.55 mg N plant–1 day–1 was recorded with Venezuela-350 × C-89. The best symbiotic combinations always showed the highest relative nitrogenase efficiency, but the differences in N2-fixation rates cannot be explained solely in terms of conservation of energy by recycling of H2. This requires further investigation.  相似文献   

10.
Summary Hydrogenase activities and N2-fixing capacities of soybean nodules (Glycine max. cv. Hodgson), inoculated with strains ofBradyrhizobium japonicum andRhizobium fredii from different geographical regions, were measured after 35 days of culture under controlled conditions. Of the strains tested, 47% induced nodules with bacteroids which recycled H2. The data obtained suggest that H2-recycling ability is not a major factor influencing early N2-fixation which depends essentially on the precocity and intensity of the initial nodulation.  相似文献   

11.
Ammonium（NH＋4） is the main nitrogen（N） form for rice crops, while NH＋4near the root surface can be oxidized to nitrate（NO-3）by NH＋4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice（Oryza sativa L.） cultivars, Yangdao 6（YD6, indica）with a high N use efficiency（NUE） and Wuyujing 3（WYJ3, japonica） with a low NUE and measured the uptake of NO-3, expression of nitrate reductase（NR）, NO-3transporter genes（NRTs）, and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake（maximum uptake velocity, Vmax） than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity（NRAmax） and actual NR activity（NRAact） as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.  相似文献   

12.
A large quantity of an unidentified compound was detected by a fluorogenic method in the soybean nodules formed with H2-uptake negative Rhizobium japonicum strains. The unidentified compound (compound X) reacted with o-phthalaldehyde in the presence of 2-mercaptoethanol giving rise to a fluorescent compound, and was not hydrolyzed in strong acid and strong base. Therefore, the compound X was considered to be one of amines and amino acids. The content of the compound X in the nodules formed with H2-uptake positive strains was remarkably lower than that in the nodules formed with H2-uptake negative strains. It was suggested that the compound X may be involved in the process of hydrogen metabolism in soybean nodules. The compound X was not detected in leaves, stems, petioles, and roots of soybean plants, but detected in H2-uptake negative strains of free-living R. japonicum. In nodules, a great portion of the compound X was distributed into cytosol fraction.  相似文献   

13.
NaCl对真盐生植物囊果碱蓬硝态氮吸收亲和力系统的影响   总被引：1，自引：0，他引：1  
采用营养液培养方法,研究了真盐生植物囊果碱蓬(Suaeda physophora Pall.) 在不同盐度和氮水平中预处理21 d后硝态氮的吸收动力学特征。结果表明,氮饥饿后,囊果碱蓬对NO-3吸收符合离子吸收动力学模型,其吸收动力学参数表现为NO-3预处理浓度增加后,高亲和力系统中Vmax增大,Km值增加,但增加的幅度不一致。经过低氮高盐预处理的囊果碱蓬高亲和力系统增加的幅度比经过高氮高盐预处理的囊果碱蓬高亲和力系统增加的幅度大; 对于低亲和力系统,NaCl长期胁迫对高氮预培养的囊果碱蓬的低亲和力系统吸收速率有抑制作用,而对低氮预培养的囊果碱蓬的低亲和力系统吸收速率有促进作用。结果说明,真盐生植物囊果碱蓬长期生长在低氮高盐条件下,为了适应特殊的环境条件,形成了耐盐的硝态氮吸收系统。  相似文献   

14.
Summary Root and stem nodulation, nitrogen fixation (acetylene-reducing activity), growth and N accumulation bySesbania rostrata as affected by season and inoculation were studied in a pot experiment. The effects ofS. rostrata as a green manure on succeeding wet-season and dry-season rice yields and total N balance were also studied.S. rostrata grown during the wet season showed better growth, nodulation, and greater acetylene-reducing activity than that grown during the dry season. Inoculation withAzorhizobium caulinodans ORS 571 StrSpc® (resistant to streptomycin and spectinomycin) on the stem alone or on both root and stem significantly increased N2 fixation by the plants. Soil and seed inoculation yielded active root nodules under flooded conditions. Plants that were not inoculated on the stem did not develop stem nodules. The nitrogenase activity of the root nodules was greater than that of the stem nodules in about 50-day-oldS. rostrata. S. rostrata incorporation, irrespective of inoculation, significantly increased the grain yield and N uptake of the succeeding wet season and dry season rice crops. The inoculated treatments produced a significantly greater N gain (873 mg N pot–1) than the noinoculation (712 mg N pot–1) treatment. About 80% of the N gained was transferred to the succeeding rice crops and about 20% remained in the soil. The soil N in the flooded fallow-rice treatment significantly declined (–140 mg N pot–1) but significantly increased in bothS. rostrata-rice treatments (159 and 151 mg N pot–1 in uninoculated and inoculated treatments respectively). The N-balance data gave extrapolated values of N2 fixed per hectare at about 303 kg N ha–1 per two crops forS. rostrata (uninoculated)-rice and 383 forS. rostrata (inoculated)-rice.  相似文献   

15.
Summary Five bacterial strains capable of Mn reduction were isolated from the rhizosphere of plants growing in different South Australian soils. They differed in their Mn-reducing capacity. The antagonism of these strains compared to the imported strain 2–79 (from the United States) against Gaeumannomyces graminis var. tritici was tested in agar and in a soil sandwich experiment at different Mn2+ concentrations in the soil. In addition, wheat seeds were coated with the different strains and with MnSO4 or with MnSO4 only in order to investigate their effect on plant growth and Mn uptake. With one exception, all strains inhibited the growth of G. graminis in agar, but to different degrees. In contrast, only two strains significantly inhibited the growth of the fungus in the soil. The hyphal density was decreased more than the hyphal length. The Mn2+ concentration in the soil also had a marked effect on fungal growth; low Mn concentrations slightly increased while high Mn concentrations strongly decreased the fungal growth. Seed treatment with MnSO4 only (+Mn) increased Mn uptake above that of the control (no seed treatment). Only the weakest Mn reducer on agar significantly increased plant growth and Mn uptake from soil in comparison with the Mn treatment. One strain was tested as seed coating without adding MnSO4; it increased the plant growth to an extent similar to the Mn treatment. Increasing the Mn uptake by plants may be one of the growth-promoting effects exerted by rhizosphere bacteria.  相似文献   

16.
Summary Nitrogenase activity was measured in young grey alder plantations in a peat bog in central Sweden. The stands were treated in three ways: (1) daily irrigation during the growing season with a complete nutrient solution, including N; (2) application of bark ash or wood ash before planting; and (3) fertilization every second year with solid PK fertilizers. Acetylene reduction assays were performed on (1) detached nodules and attached nodules, either on (2) whole enclosed plants or (3) enclosed nodules. The acetylene reduction rate for the enclosed plants showed a maximum in July when mean values of nearly 80 mol C2H4 (g nodule dry matter)-1 h-1 were reached. No diurnal patterns were observed. The irrigated stands, with an N supply, showed overall nitrogenase activities that corresponded well with those of the other treatments. Only in the case of temporarily increased soil nutrient concentrations in the irrigated stands did the nitrogenase activity fall considerably. In 6-to 7-year-old intensively managed irrigated stands N2-fixation was estimated as 85–115 kg N ha-1 year-1 which was about 55% of the total N uptake of the trees.  相似文献   

17.
果胶细菌处理油菜幼根（2天苗龄、根长3cm），同时接种紫云英根瘤菌突变菌株（Rhizobiumhuakuii），诱发类根瘤的结瘤率为96.80％。从这些类根瘤中分离的菌株能回接到原寄主。类根瘤的电镜观察可以明显地见到细胞内充满了细菌。乙炔还原法测定的固氨酶活性（C2H4）为76.80nmol／（planth）。  相似文献   

18.
Summary There were significant differences among pigeonpea [Cajanus cajan (L.) Millsp] Rhizobium sp. strains (IC 3506, IC 3484, IC 3195, and IC 3087) in their ability to nodulate and fix N2 under saline conditions. Pigeonpea plants inoculated with IC 3087 and IC 3506 were less affected in growth by salinity levels of 6 and 8 dS m-1 than plants inoculated with the other strains. For IC 3506, IC 3484, and IC 3195, there was a decrease in the number of nodules with increasing salinity, while the average nodule dry weight and the specific nitrogenase activity remained unaffected. However, in IC 3087, the number of nodules increased slightly with increasing salinity. Leaf-P concentrations increased with salinity in the inoculated plants irrespective of the Rhizobium sp. strain, and leaf-N concentrations decreased with increasing salinity in IC 3484 and IC 3195 only. Shoot-Na and-Cl levels were further increased in these salt-sensitive strains only at 8 dS m-1. Therefore there may be scope for selecting pigeonpea Rhizobium sp. symbioses better adapted to saline conditions. The Rhizobium sp. strains best able to form effective symbioses at high salinity levels are not necessarily derived from saline soils.Submitted as JA No. 919 by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)  相似文献   

19.
In order to study the establishment of a spermosphere, the C2H2 reduction activity of N2-fixing bacteria isolated from river sand was examined in a simulated spermosphere in the river sand which contained sucrose, an amino acid mixture, and CN- released from plant seeds. The sand incubated with 10-10 to 10-9 mol CN- 30 g sand-1 exhibited higher C2H2 reduction activity than that without CN-. The change in the most probable number of N2 fixers with increasing quantities of CN- roughly corresponded to that in C2H2 reduction activity. However, the most probable number of non-N2-fixing bacteria decreased except for CN--tolerant ones. Both C2H2 reduction activity and proliferation of the N2 fixers isolated on a modified Burk's medium were almost similar to those in the bacteria in the sand. In contrast, the proliferation of some nonfixers decreased with an increasing CN- concentration. C2H2 reduction activity of N2 fixers cultured in combination with non-fixers exhibited a clear peak at 10-7 M CN- as for C2H2 reduction activity in the sand. We therefore speculate that cyanide evolved from seeds during a pregermination period may suppress the growth of general bacteria, but may promote the proliferation of N2 fixers, thus contributing to the establishment of a spermosphere.  相似文献   

20.
Summary The competitive ability of inoculated and indigenous Rhizobium/Bradyrhizobium spp. to nodulate and fix N2 in grain legumes (Glycine max, Vigna unguiculata, Phaseolus vulgaris) and fodder legumes (Vicia sativa, Medicago sativa, and Trifolium subterraneum) was studied in pots with two local soils collected from two different fields on the basis of cropping history. The native population was estimated by a most-probable-number plant infectivity test in growth pouches and culture tubes. The indigenous rhizobial/bradyrhizobial population ranged from 3 to 2×104 and 0 to 4.4×103 cells g-1 in the two soils (the first with, the second without a history of legume cropping). Inoculated G. max, P. vulgaris, and T. subterraneum plants had significantly more nodules with a greater nodule mass than uninoculated plants, but N2 fixation was increased only in G. max and P. vulgaris. A significant response to inoculation was observed in the grain legume P. vulgaris in the soil not previously used to grow legumes, even in the presence of higher indigenous population (>103 cells g-1 soil of Rhizobium leguminosarum bv phaseoli). No difference in yield was observed with the fodder legumes in response to inoculation, even with the indigenous Rhizobium sp. as low as <14 cells g-1 soil and although the number and weight of nodules were significantly increased by the inoculation in T. subterraneum. Overall recovery of the inoculated strains was 38–100%, as determined by a fluorescent antibody technique. In general, the inoculation increased N2 fixation only in 3 out of 12 legume species-soil combinations in the presence of an indigenous population of rhizobial/bradyrhizobial strains.  相似文献   

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