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1.
Summary Field experiments were carried out to determine the effects of single and mixed inoculations with Rhizobium and vesicular-arbuscular mycorrhiza (VAM) on nodulation, symbiotic N2 fixation and yield of soybeans in six Taiwan subtropical-tropical sites. Inoculation with Rhizobium alone significantly increased nodulation, nodule weight and nitrogenase activity of nodules in three out of six experimental fields, and affected soybean yields in the range –13% to + 134%. Inoculation with VAM fungi alone did not have a significant effect on nodulation and nitrogenase activity. Mycorrhiza inoculation affected soybean yields in the range –13% to + 65%, but only the yield increases at one out of six sites with N application were statistically significant. Mixed inoculation with Rhizobium and mycorrhiza affected yields in the range –8% to + 145% A synergistic effect from mixed inoculation of Rhizobium-mycorrhiza on soybean yields was found in one out of six experimental fields. The yield response to N application (40 kg N ha–1) in these six paddy-field trials was not significant. These results suggest that single or mixed inoculation of rhizobia can greatly assist soybean grain yields and can replace N fertilizers. 相似文献
2.
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
3.
Raman Rai 《Biology and Fertility of Soils》1992,14(4):293-299
Summary Following screening, selection, characterization, and symbiotic N2 fixation with 12,5, 25.0, and 40.0 mg N kg–1 in normal and saline-sodic soils, only two Phaseolus vulgaris genotypes (HUR 137 and VL 63) and two Rhizobium spp. strains (ND 1 and ND 2) produced maximum nodulation, nitrogenase activity, plant N contents, and grain yields in saline-sodic soil, with 12.5 mg N kg–1, compared with the other strains. However, interactions between strains (USDA 2689, USDA 2674, and ND 5) and genotypes (PDR 14, HUR 15, and HUR 138) were significant and resulted in more nodulation, and greater plant N contents, nitrogenase activity, and grain yields in normal soils with 12.5 mg N kg–1 compared with salt-tolerant strains. Higher levels of N inhibited nodulation and nitrogenase activity without affecting grain yields. To achieve high crop yields from saline-sodic and normal soils in the plains area, simultaneous selection of favourably interacting symbionts is necessary for N economy, so that bean yields can be increased by the application of an active symbiotic system. 相似文献
4.
Summary In three field trials conducted during the summer season of 1986, 1987 and 1989 in an alkaline soil, 17 accessions of annual Sesbania spp. were evaluated for nodulation, N2 fixation (acetylene reduction assay), dry weight of roots and shoots, woody biomass production, and nutrient uptake. At 50 days after sowing all the accessions were effectively nodulated (average 36.4 root nodules plant-1) with a high nodule score (3.4). There was a lot of variation in nodule volume and mass and in acetylene reduction activity but not in N content (5.2%). N uptake in shoots, roots and nodules averaged 639, 31, and 13 mg plant-1, respectively, and much of the fixed N remained in shoots. Accessions of S. cannabina complex performed better than others. S. rostrata had poor root nodulation but exhibited excellent stem nodulation (300 nodules plant-1) even though not inoculated with Azorhizobium sp. Average concentrations of N, P, K, S, Ca, and Mg in the shoots were high, at 3.2, 0.28, 1.5, 0.28, 1.5, and 0.4% respectively, and Na was low (0.15%), reflecting the usefulness of Sesbania spp. as an integrated biofertilizer source. Green matter production was 26.0 Mg ha-1 (5.9 Mg dry matter) and N uptake was 158 kg ha-1, 54 days after sowing. Average woody biomass of six accessions at maturity, 200 days after sowing, was high (19.9 Mg ha-1), showing its potential for shortterm firewood production. Total nutrient uptake for production of woody biomass (200 days of growth) was no more demanding than growing the plant to the green-manuring stage of 50–60 days' growth. 相似文献
5.
Summary
Aeschynomene afraspera is a wild annual legume growing in periodically waterlogged soils in western Africa. This legume is characterized by a profuse stem nodulation. Nodules are formed on the stem at the emergence of lateral root primordia, called nodulation sites. These sites are irregularly distributed on vertical rows all along the stem and branches. Stem nodules are hemispherically shaped. Their outside is dark green and they contain a red-pigmented central zone. Stem nodules exhibit a high nitrogen-fixing potential. Acetylene reduction assays result in stem nodule activity of 309 mol C2H4 g–1 dry nodule h–1. Field-grown stem nodulated Aeschynomene accumulated more N (51 g N m–2 in 10 weeks) than the root nodulated one. Because of this nitrogenfixing potential and its ability to grow in waterlogged conditions, A. afraspera could probably be introduced into tropical rice cropping systems. 相似文献
6.
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
7.
Summary Wheat seedlings were inoculated with rhizosphere nitrogen-fixing bacteria and grown gnotobiotically for 15 days. The growth medium consisted of semisolid agar with or without plant nutrients. The bacteria, isolated from roots of field-grown wheat, were three unidentified Gram-negative rods (A1, A2, E1), one Enterobacter agglomerans (C1) and two Bacillus polymyxa (B1, B2). A strain of Azospirillum brasilense (USA 10) was included for comparison.Nitrogenase activity (acetylene reduction activity, ARA) was tested on intact plants after 8 and 15 days of growth. In semisolid agar without plant nutrients, five isolates showed ARA of 0.01–0.9 nmol C2H4 plant–1 h–1, while the two strains of B. polymyxa had higher ARA of 3.3–10.6 nmol C2H4 plant–1 h–1.Plant development was not affected by inoculation with bacteria, except that inoculation with B. polymyxa resulted in shorter shoots and lower root weight.Transmission electronmicroscopy of roots revealed different degrees of infection. A. brasilense, A1 and A2, occurred mainly in the mucilage on the root surface and between outer epidermal cells (low infectivity). B. polymyxa strains and E1 were found in and between epidermal cells (intermediate infectivity) while E. agglomerans invaded the cortex and was occasionally found within the stele (high infectivity). 相似文献
8.
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
9.
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
10.
Responses of proton release to phosphorus (P) availability by nodulated roots of common bean (Phaseolus vulgaris L.) were investigated for lines BAT 477 and CocoT, inoculated with Rhizobium tropici CIAT 899 in hydroaeroponic culture under glasshouse conditions. Phosphorus was supplied as KH2PO4 at 15 and 60 μmol plant–1 week–1 (15P and 60P). Proton release was higher for BAT 477 than for CocoT under both P supplies. However, it was higher for 60P than 15P, whatever the line. The ratio of proton release per unit biomass of nodulated root was higher for BAT 477 than for CocoT, independent of P deficiency. Proton release was correlated with the nodulated‐root respiration for both genotypes and with the nodule respiration linked with nitrogen fixation for CocoT. Thus, the nodulation was more limited by 15P than root and shoot growth and more in CocoT than in BAT 477. It is concluded that independent of symbiotic N2 fixation, proton release was higher in BAT 477 than in CocoT and that the nodulated legume releases a substantial amount of protons into its rhizosphere that is correlated with its nitrogen fixation that eventually depends upon the nodule permeability to O2 diffusion. 相似文献
11.
Summary The earthworms Lumbricus rubellus (Hoffmeister) and Dendrobaena octaedra (Savigny) were studied in the laboratory to determine their effects on decomposition and nutrient cycling in coniferous forest soil. CO2 evolution was monitored, and pH, PO
4
3–
–P, NH
4
+
–N, NO
3
–
–N, total N, and total C in the leaching waters were measured. After three destructive samplings, numbers of animals, mass loss, pH, and KCl-extractable nutrients were analysed.The earthworms clearly enhanced the mass loss of the substrate, especially that of litter. L. rubellus stimulated microbial respiration by 15–18%, whereas D. octaedra stimulated it only slightly. The worms significantly raised the pH of the leaching waters and the humus; L. rubellus raised the value by 0.2–0.6 pH units and D. octaedra by 0.1–0.4 units. Both worms increased N mineralization. Although the biomass of both worms decreased during the experiment, the N released from decomposing tissues did not explain the increase in N leached in the presence of earthworms. The worms influenced the level of PO
4
3–
–P only slightly. 相似文献
12.
A. M. N. Omar C. Richard P. Weinhard J. Balandreau 《Biology and Fertility of Soils》1989,7(2):158-163
Summary This study is an attempt to describe the dominant N2-fixing microflora associated with the roots of wetland rice. Rice cultivar Giza 171 was grown in a phytotron on two alluvial Egyptian soils for 8 days, a stage when the nitrogenase activity of undisturbed plants reached a level of 245 × 10–6 mol C2H4 h–1 g–1 dry weight of leaf. The roots and rhizosphere soils were then used for counting and isolating dominant diazotrophs. Counts and initial enrichment steps were carried out on a selective medium made of an axenic rice plantlet, the spermosphere model, incubated under 1 % acetylene. The counts were very high, exceeding 108 bacteria g–1 dry weight of rhizosphere soil. Enterobacteriaceae were dominant; most isolates were Enterobacter cloacae belonging to different biotypes in the two soils. Enterobacter agglomerans, Citrobacter freundii and Klebsiella planticola were also present as members of the dominant microflora. Azospirillum brasilense and Azospirillum lipoferum were present as well, but less abundant. 相似文献
13.
M.?V.?Angoa?Pérez J.?Gonzalez?Casta?eda J.?T.?Frías-Hernández O.?Franco-Hernández O.?Van?Cleemput L.?Dendooven
In the central highlands of Mexico, mesquite (Prosopis laevigata) and huisache (Acacia schaffneri), N2-fixing trees or shrubs, dominate the vegetation and are currently used in a reforestation program to prevent erosion. We investigated how natural vegetation or cultivation of soil affected oxidation of CH4, and production of N2O. Soil was sampled under the canopy of mesquite (MES treatment) and huisache trees (HUI treatment), outside their canopy (OUT treatment) and from fields cultivated with maize (ARA treatment) at three different sites while production of CO2, and dynamics of CH4, N2O and inorganic N (NH4+, and NO3–) were monitored in an aerobic incubation. The production of CO2 was 2.3 times higher and significantly greater in the OUT treatment, 3.0 times higher in the MES treatment and 4.0 times higher in the HUI treatment compared to the ARA treatment. There was no significant difference in oxidation of CH4 between the treatments, which ranged from 0.019 g CH4–C kg–1 day–1 for the HUI treatment to 0.033 CH4–C kg–1 day–1 for the MES treatment. The production of N2O was 30 g N2O–N kg–1 day–1 in the MES treatment and >8 times higher compared to the other treatments. The average concentration of NO3– was 2 times higher and significantly greater in the MES treatment than in the HUI treatment, 3 times greater than in the OUT treatment and 10 times greater than in the ARA treatment. It was found that cultivation of soil decreased soil organic matter content, C and N mineralization, but not oxidation of CH4 or production of N2O. 相似文献
14.
A field experiment was conducted to study the N2 fixation efficiency of Sesbania rostrata and S. cannabina as affected by agronomic practices in semi-arid subtropical climate, Sowing seeds resulted in smaller numbers of nodules, lower dry weight, lower total biomass, less N uptake, and less N2 fixation for S. rostrata than S. cannabina, while cut-stem planting improved the symbiotic efficiency. Flooding the soil increased the relative humidity of the crop micro-environment by 4–11% and induced early appearance of stem nodules in S. rostrata. Only 67 kg N ha-1 was fixed by S. rostrata compared to 160 kg N ha-1 by S. cannabina when normal agronomic practices (sowing and non-flooding) were followed. In contrast, planting stem cuttings and flooding resulted in greater biological N2 fixation, 307 and 209 kg N ha-1 by S. rostrata and S. cannabina, respectively. Therefore, S. rostrata can be successfully exploited as a green manure when stem cuttings are planted under flooded conditions. 相似文献
15.
Litterfall, decomposition, and N release in 5-year-old and 8-year-old plantations of Casuarina equisetifolia (Forst.) in the dry tropical region of the Vindhyan plateau were studied during 1989–1990. Maximum litterfall occurred in May. The total litterfall ranged from 7.2 to 9.9t ha-1 year-1 in the 5-year-old stand and from 11.3 to 12.7t ha-1 year-1 in the 8-year-old stand over the 2-year period. Photosynthetic branchlets contributed 87–95% to the total litter. The relative decomposition rates of litter components of the ash-free mass were highest in the rainy months (4.7 to 9.9mg g-1 day-1) followed by winter (2.8 to 3.6 mg g-1 day-1) and lowest in the summer months (1.7 to 3.0 mg g-1 day-1). Similar patterns were observed for N release. The annual decay constant was highest for cone litter and lowest for photosynthetic branchlets. During decomposition, the photosynthetic branchlets showed N immobilization in November and April, the twig litter in March, and the roots in January and February. N release per unit area (g m-2) was maximum from the photosynthetic branchlets (5.3–6.3) followed by cones (4.4) > roots (3.4) > twigs (2.6–3.2). The combination of the litter C:N ratio, moisture, and temperature with the relative decomposition rate in a multiple regression analysis explained 66–84% of the variability in mass loss and 58–66% of the variability in N release. 相似文献
16.
Nguyen Van Phi Hung Shiori Watanabe Shinji Ishikawa Norikuni Ohtake Kuni Sueyoshi Takashi Sato 《Soil Science and Plant Nutrition》2013,59(6):888-895
The quantitative analysis of the initial transport of fixed isotope 15-nitrogen (15N) in intact nodulated soybean plants (Glycine max [L.] Merr. cv. Williams) was investigated at the vegetative stage (36 days after planting, DAP) and pod-filling stage (91 DAP) by the 15N pulse-chase experiment. The nodulated roots were exposed to N2 gas labeled with a stable isotope 15N for 1 h, followed by 0, 1, 3 and 7 h of exposure with normal air. Plant roots and shoots were separated into three sections (basal, middle and distal parts) with the same length of the main stem or primary root. Approximately 80 and 92% of fixed N was distributed in the basal part of the nodulated roots at the vegetative and pod-filling stages by the end of 1 h of 15N2 exposure, respectively. In addition, about 90% of fixed 15N was retained in the nodules and 10% was exported to root and shoot after 1 h of 15N2 exposure at 91 DAP. The percentage distribution of 15N in the nodules at the pod-filling stage decreased from 90% to 7% during the 7 h of the chase period, and increased in the roots (14%), stems (54%), leaves (12%), pods (10%) and seeds (4%). The 15N distribution was negligible in the distal root segment, suggesting that N fixation activity was negligible and recycling fixed N from the shoot to the roots was very low in the initially short time of the experiment. 相似文献
17.
Summary Sensitive methods for measuring cyanide and cyanogenic glucosides in soil and sand culture have been developed. A microdiffusion technique is described which depends on the enzymic conversion of linamarin and lotaustralin to HCN, its release following acidification and incubation, and its detection in NaOH. Conditions for hydrolysis and HCN recovery have been optimised. The cyanide content of a silt loam soil (under non-cyanogenic wheat) was 5.47 nmol cyanide g–1 air-dried soil whilst that in an organic soil under the cyanogenic bracken, Pteridium aqgilinum, was 12.2 nmol g–1. Exudation of cyanogenic glucosides by linseed, Linum usitatissimum, was measured in plant growth tubes containing sand and a nutrient medium. Sterile plants exuded an average of 6.88 nmol glucosides plant–1 week–1 whilst, in contaminated tubes, the level fell to 4.72 nmol. Analysis of plant roots on each sampling occasion showed that 6.88 nmol was, on average, equivalent to 16.15% of the total root content of cyanogenic glucosides. There was a low but positive correlation between fresh weight of plant roots and the level of exuded glucosides. There was no evidence that plant roots produced free HCN. 相似文献
18.
Feeding and casting activity of Amynthas alexandri fed on corn, wheat leaves, and mixed grasses were monitored in laboratory cultures. Casts were produced on the surface and sides of the containers. Food consumption varied from 36.5 to 69 mg g–1 live worm day–1. Cast production ranged from 3.95 to 5.9 mg g–1 live worm day–1. The C:N ratio in casts in laboratory cultures (11.17) and in field samples (8.84) was consistently lower than the corresponding ratio in the parent soil (13.19 and 10.54, respectively). This was probably due to mineralization of plant-derived organic material during passage through earthworms with consequent low C:N ratios. 相似文献
19.
Summary Variation in nodulation and N2 fixation by the Gliricidia sepium/Rhizobium spp. symbiosis was studied in two greenhouse experiments. The first included 25 provenances of G. sepium inoculated with a mixture of three strains of Rhizobium spp. N2 fixation was measured using the 15N isotope dilution method 12 weeks after planting. On average, G. sepium derived 45% of its total N from atmospheric N2. Significant differences in fixation were observed between provenances. The percentage of N derived from atmospheric N2 ranged from 26 to 68% (equivalent to 18–62 mg N plant-1) and was correlated with total N in the plant (r=0.70; P=0.05). The second experiment included six strains of Rhizobium spp. and two methods of inoculation and the plants were harvested 14,35 and 53 weeks after planting. In the first harvest significant differences were found between the number of nodules and the percentage and amount of N2 fixed. There was also a significant correlation between the number of nodules and the amount of N2 fixed (r=0.92; P=0.05). In the final harvest no correlation was observed, although there were significant differences between the number of nodules and the percentage of N derived from the atmosphere. The amount of N2 fixed increased with time (from an average of 27% at the first harvest to 58% at the final harvest) and was influenced by the Rhizobium spp. strain and the method of inoculation. It ranged from 36% for Rhizobium sp. strain SP 14 to 71% for Rhizobium SP 44 at the last harvest. Values for the percentage of atmosphere derived N2 obtained by soil inoculation were slightly higher than those obtained by seed inoculation. 相似文献
20.
Diversity of diazotroph populations in the rhizosphere of maize (Zea mays L.) growing on different French soils 总被引：1，自引：0，他引：1
Summary We studied the dominant diazotrophs associated with maize roots and rhizosphere soil originating from three different locations in France. An aseptically grown maize plantlet, the spermosphere model, was used to isolate N2-fixing (acetylene-reducing) bacteria. Bacillus circulans was the dominant N2-fixing bacterium in the rhizosphere of maize-growing soils from Ramonville and Trogny, but was not found in maize-growing sandy soil from Pissos. In the latter soil, Enterobacter cloacae, Klebsiella terrigena, and Pseudomonas sp. were the most abundant diazotrophs. Azospirillum sp., which has been frequently reported as an important diazotroph accociated with the maize rhizosphere, was not isolated from any of these soils. The strains were compared for their acetylene-reducing activity in the spermosphere model. The Bacillus circulans strains, which were more frequently isolated, also exhibited significantly greater acetylene-reducing activity (3100 nmol ethylene day-1 plant-1) than the Enterobacteriaceae strains (180 nmol ethylene day-1 plant-1). This work indicates for the first time that Bacillus circulans is an important maizerhizosphere-associated bacterium and a potential plant growth-promoting rhizobacterium. 相似文献