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1.
Exceptional symbiotic nitrogen fixation with Sesbania has provided high soil fertility for many past centuries of paddy rice production. Unique stem nodulation results in high nitrogenase activity levels of S. rostrata, Brem, during rapid growth in continuously flooded rice fields that greatly disfavor legume root nodulation and this functional development. The objective of this study was to determine plant nutrient interactions that influence contrasting root and aerial stem nodule histology governing effective nitrogenase activity levels and nitrogen fixation. Top growth, nodulation, and nitrogenase activity levels were significantly increased with increased available soil P. Response to K levels and Ca additions resulted only when soil P was adequate in all treatment combinations. However, there was no significant correlation between fresh nodule weight, nitrogenase activity, and nodules plant‐1 for both root nodules and aerial stem nodules. Nodule histology was highly contrastive with nodule type and Rhizobium morphology, cytosol composition, and governing enzyme activity levels. Distinctive nonpleomorphic cocci bacteroids of functional aerial stem nodules have tentative designation as Azorhizobium caulinodans gen. nov. sp. nov.  相似文献   

2.
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   

3.
Sulphur (S) has become a major limiting factor for plant production in industrial as well as in remote industrial rural areas. Limitation of S can reduce legume N2 fixation by affecting nodule development and function. In pot experiments with pea (Pisum sativum L.) and alfalfa (Medicago sativa L.), we investigated the influence of S on growth, ferredoxin, ATP and leghemoglobin concentrations. Addition of 200 mg S pot−1 increased yield of shoots, roots and nodules of both plant species significantly. However, the influence of S on nodule yield formation was most pronounced. Pea and alfalfa roots were found to have higher S concentrations than shoots and being up to 2.9 times the S concentration in the shoots of peas under S-sufficient conditions. Sulphur addition also increased N2 fixation significantly. The ferredoxin concentration in bacteroids of root nodules of pea was increased significantly by S only 10 weeks after planting and in bacteroids of root nodules of alfalfa 10 and 17 weeks after planting, while on per pot base the amounts of ferredoxin were higher throughout the experimental period of time. The ATP concentration of bacteroids of root nodules of both plant species as well as of mitochondria of root nodules of pea were significantly higher with optimum S supply. The effects of S deficiency on N2 fixation are likely to be caused by the shortage of ferredoxin and ATP. The amount of leghemoglobin was reduced in comparison to nodules of the S-sufficient plants.  相似文献   

4.
ABSTRACT

The specific mechanism by which nitrogen application affects nodulation and nitrogen fixation in legume crops remains uncertain. To further study the effects of nitrogen application on soybean nodulation and nitrogen accumulation, three consecutive tests were performed during the VC-V4, V4-R1 (10 days), and R1-R2 (10 days) growth periods of soybean. In a dual-root soybean system, seedlings on one side were watered with a nutrient solution containing NH4+ or NO3? as the N source (N+ side), and those on the other side were watered with a nitrogen-free nutrient solution (N- side). During the VC-R2 period, on the N+ side, high nitrogen treatment inhibited nodule growth and nitrogenase activity (EC 1.18.6.1), and the inhibition was significantly increased with increasing high nitrogen supply time (10 days, 20 days). When the high nitrogen treatment time reached 20 days, the specific nitrogenase activity (C2H4 μmol?1 g?1 nodule dry mass h?1) was similar to that in the low nitrogen treatment, indicating that the nitrogen fixation capacity per gram of dry mass nodules was almost the same. Therefore, it is assumed that long-term high nitrogen treatment mainly reduces nitrogen fixation by reducing the nodule number. The effect of nitrogen concentration on the roots on the N+ side was greater than that on the N- side. Taken together, these results indicate that nitrogen application affects a contact-dependent local inhibition of root nodule growth, nitrogenase activity, and nitrogen accumulation. The whole plant systematically regulates specific nitrogenase activity, and high nitrogen inhibition is recoverable.  相似文献   

5.
ABSTRACT

Common bean (Phaseolus vulgaris L.) has been shown to be a poor di-nitrogen (N2) fixer and nitrogen (N) fertilizers are usually recommended in bean production. Recent research results suggest that the success of the bean/Rhizobium symbiosis may depend, in part, on the specific bean genotype. Twelve dry bean genotypes differing in growth habit, commercial class, and maturity were evaluated for N2 fixation in field experiments. Response to inoculant application was highly influenced by environmental conditions. Genotypes differed in nodule dry mass, seed yield, seed N yield, and in amount of N2 fixed. Growth habit alone was not adequate in classifying bean genotypes for N2 fixation. The actual amount of N2 fixed was low ranging from 16 kg ha?1 to 27 kg ha?1, suggesting that the symbiotic process alone may not provide adequate N for optimum seed yield in dry environments.  相似文献   

6.
Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH2PO4 solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N2 fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.  相似文献   

7.
Abstract

Methyl jasmonate (MeJA) has recently been shown to act as a plant-to-bacteria signal. We tested the hypothesis that pre-induction of Rhizobium leguminosarum bv. phaseoli cells with genistein and/or MeJA would at least partially overcome the negative effects of low root zone temperature (RZT) on bean nodulation, nitrogen fixation and plant growth. Otebo bean plants were grown at constant air temperature (25oC) and two RZT regimes (25 and 17oC) and inoculated with R. leguminosarum bv. phaseoli pre-induced with MeJA and/or genistein. Our results indicate that low RZT inhibited nodulation, nitrogen fixation and plant growth. The plants growing at low RZT began fixing nitrogen seven days later compared to those at higher RZT. The low RZT plants had fewer nodules, lower nodule weight, less N fixation, slower plant growth, fewer leaves, smaller leaf area, and less dry matter accumulation comared to plants at a higher RZT. Rhzobium leguminosarum bv. phaseoli cells induced with genistein and/or MeJA enhanced bean nodulation, nitrogen fixation and growth at both optimum and suboptimum RZTs. The results of this study indicate that MeJA improves bean nitrogen fixation and growth at both optimum and suboptimum RZTs, and can be used alone or in combination with genistein to partially overcome the low RZT induced inhibitory effects on nodulation and nitrogen fixation.  相似文献   

8.
Abstract

High nitrogen (N2)‐fixing potential is a desirable characteristic for any candidate hedgerow tree. Thus a study was conducted to evaluate Albizia lebbeck as a N2‐fixing tree in comparison to Gliricidia sepium and Leucaena leucocephala currently used in alley cropping. Nitrogen fixation and utilization were assessed in a screenhouse at four months after planting by the 15N dilution technique using Senna siamea as the non N2‐fixing reference. A. lebbeck accumulated significantly more N than L. leucocephala, but G. sepium was intermediate. This superiority in N yield was mainly due to its abundant nodule dry weight production which accounted for up to 10.8% of its total N. This was equivalent to 2.5 and 6 fold that of Gliricidia and Leucaena nodules, respectively. A. lebbeck had bigger but significantly (P<0.05) lower number of nodules per plant than G. sepium, but it did not differ from Leucaena. Albizia was the best N2 fixer with 44% Ndfa equivalent to 533 mg N per plant. G. sepium followed with 28% Ndfa and L. leucocephala with 18% Ndfa corresponding to 321 and 191 mg N fixed, respectively. However, the relatively higher N2 fixation in Albizia was not translated into higher N or dry matter yields. As A. lebbeck fixed more N, it depended less on soil N (49.8%) than did Leucaena (72.5% Ndfs) and Gliricidia (63.9% Ndfs) and less on fertilizer N as well. Thus A. lebbeck appears to be a potential hedgerow species for alley cropping purpose.  相似文献   

9.
The influence of three sulphur application rates in combination with two nitrogen application rates on N2 fixation and growth of different legumes was investigated. N was applied as N-labelled 15NH4 15NO3. The 15N isotope dilution technique was used to estimate N2 fixation. At both N increments dry matter yield was highest with high S supply. Independently of the N supply, the high S application rate resulted in a significantly higher N accumulation, which was mainly caused by a higher N2 fixation rate. With the grain legumes the weight of nodules was increased by the high S application rate. The higher number of nodules per pot with optimum S supply was the result of a better root growth. Rates of acetylene reduction correlated significantly with S supply.  相似文献   

10.
Abstract

Nitrogen fixation was simulated for a leafless variety (Delta) of pea (Pisum sativum L.) in central Sweden. It is assumed that N2 fixation is basically proportional to root biomass, but limited by high root N or low substrate carbon concentrations. Input data on root carbon and nitrogen were estimated from observations of above-ground biomass and nitrogen. The simulated N2 fixation was compared with estimated values from observations using the 15N labelling technique. Test data were taken from pea monocultures and pea-oat mixtures with varying pea biomass levels during 1999. Simulated within-season accumulated N2 fixation correlated to the estimated N2 fixation with a correlation coefficient (R 2) of 0.74. For seasonal simulations, the predictability was higher (R 2=0.93). Two alternative non-dynamic models, estimating seasonal N2 fixation as proportional to above-ground biomass and above-ground N, respectively, gave lower predictability (R 2=0.83 and 0.80, respectively). The models were also applied to a second year (1998) and two other sites by comparison with accumulated N2 fixation estimated by the Difference method. A halved specific N2 fixation rate (expressed per unit of root biomass) in 1999, compared with 1998, corresponded to essentially dryer and warmer soil conditions during 1999. It was indicated that the variations in soil moisture were more important than soil temperature. It was concluded that the abiotic responses might be of great importance for modelling N2 fixation rate under different soil conditions.  相似文献   

11.
Abstract

It is well known that stem nodules are formed on the aerial parts of Aeschynomene spp. and Sesbania rostrata grown in the field (Yatazawa and Yoshida 1979; Dreyfus and Dommergues 1981; Yoshida et al. 1985). We have reported that stem nodules were successfully formed by inoculation of Rhizobium isolates derived from both stem and root nodules of A. indica (Yoshida et al. 1985; Sasakawa et al. 1986). The specific activity of nitrogen fixation in stem nodules is comparable to that of root nodules (Sasakawa et al. 1986; Sasakawa 1990). A red pigment, which suggests the presence of leghemoglobin, was detected in stem nodules as well as in root nodules (Yatazawa and Yoshida 1979; Yatazawa and Susilo 1980; Sasakawa et al. 1986).  相似文献   

12.
The effect of prior soil amendment with different N sources at 50 mg N (kg soil)—1 on nodulation and N2 fixation of faba bean (Vicia faba L. cv. Troy) using wheat (Triticum aestivum L. cv. Star) as reference crop was assessed in a pot experiment. Four treatments viz legume manure (LEGM) as clover shoots, cereal manure (CEREM) as barley straw, N fertilizer (FERT‐N) as Ca(NO3)2, and no‐manure control (NOMAN) were investigated consecutively at 45, 70, and 90 days after sowing (DAS). Faba bean nodulated profusely, with an increase on average from 629 nodules per pot at 45 DAS to nearly 2.3‐ and 3.3‐fold at 70 and 90 DAS, respectively. Low nodule numbers and nodule dry matter occurred under FERT‐N and CEREM, whereas high values were found for NOMAN and LEGM. Soil amendment affected percent N2 fixation in relation to N source and plant age. Highest percent N2 fixation (≥ 90 %) was found under the lowest N‐supplying amendments, no‐manure, and cereal manure, respectively. FERT‐N depressed N2 fixation particularly at 45 DAS when N2 fixation was reduced to as low as 23 %. The rise in N2 fixation thereafter suggests that faba bean adjusted after depletion of mineral N in the soil. N2 fixation was also decreased after cereal straw application, even though N concentration in faba bean plants was high. The results indicate that plant residues, both with high and low N concentration, applied to soil to raise its fertility may interfere with N2 fixation of faba bean.  相似文献   

13.
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   

14.
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   

15.

Red clover (Trifolium pratense L.) is one of the most important plants in forage production, especially in northern areas. Fertilisation practices are focused on high yield and forage quality but effects of nutrients on nodulation and N2 fixation are poorly understood. The aim of this work was to study how nitrogen (N) and phosphorus (P) separately as well as in combination affected nodulation. Red clover plants were grown in pots with gravel in a greenhouse for 11 weeks. To resemble field conditions the root temperature was kept lower than the shoot temperature. Plants were given five different combinations of N and P concentrations during growth. The result showed that at high N concentrations P had a counteracting effect on the N inhibition. The N2-fixation parameters, nodule number, nodule dry matter and specific nitrogenase activity, were six times higher in plants grown with high N and high P than in plants with high N and low P. When the N2-fixation parameters and the dry matter of roots and shoots were related to total plant dry matter, there was a stronger effect of P on nodulation parameters than on roots and shoots. This indicates that P has a direct effect on the N2-fixation parameters, rather than an indirect effect via increased plant growth. These results demonstrate the importance to studying the effects of more than one nutrient at a time.  相似文献   

16.
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   

17.
Abstract

Combined nitrogen [nitrate (NO3‐), ammonium (NH4+), and urea] will inhibit all components of symbiotic nitrogen (N2) fixation if present in sufficient concentrations. It is generally accepted that nitrate is particularly inhibitory to nodule growth and nitrogenase activity, and somewhat less inhibitory to the infection process. This project examined whether providing low (0.1 ‐ 0.5 mM) static concentrations of NO3‐ to pea (Pisum sativum L. cv. Express), seedlings could avoid the period of N hunger experienced prior to the establishment of N2 fixation, without delaying or reducing the symbiotic N2 fixation. All concentrations of NO3 ? tested significantly inhibited all measured components of N2 fixation. The nodulation process as measured by nodule number was inhibited to a similar degree as the other parameters. A concentration dependent response was evident, with 0.1 mM NO3 ? causing less inhibition than the 0.2 or 0.5 mM concentrations. Our results indicate the within the concentrations of 0.1 mM and 0.5 mM NO3 ?, it is not possible to stimulate the growth of pea plants without inhibiting nodulation and N2 fixation.  相似文献   

18.
The efficiency of symbiotic dinitrogen (N2) fixation in Vicia faba L. in combination with 3 different Rhizobium leguminosarum strains was studied in a pot experiment during vegetative and reproductive growth. The objective of the experiments was to assess variability among Rhizobium strains inoculated on single legume species and determine possible reasons for observed variations. Dry matter formation, N2 fixation and the carbon (C) costs of N2 fixation were determined in comparison with nodule free plants grown with urea. Nodule number and the capacity of different respiratory chains in the nodules were also measured. The plants inoculated with the Rhizobium strain A 37 formed less dry matter and fixed less N compared to the other two Rhizobium strains (Vic 1 and A 150). This coincided with a lower number of nodules and higher C costs of N2 fixation. The C costs for N2 fixation were in all cases significantly lower during reproductive growth compared to vegetative growth. Neither the latter nor the differences in C expenditure for N2 fixation between the Rhizobium strains could be explained in terms of differences or shifts in the capacity of different respiratory chains in the nodules.  相似文献   

19.
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   

20.
Abstract

A pot experiment was conducted under natural climatic conditions to study the effect of low doses of gamma irradiation (0, 5, 10, and 20 Gy) on the performance of winter chickpea (Cicer arietinum L.) in the presence of increased supply of 15N labeled ammonium sulfate (0, 20, 50, and 100 kg N ha‐1). Presowing seed irradiation produced a significant increase in dry matter production (up to 3 6%) and total nitrogen yield (up to 45%). The stimulative effect of irradiation was more pronounced with the application of NH4 +‐N fertilizer. Seed irradiation increased the amount of N2‐fixation by 8–61% depending on the dose and level of NH4 +‐N fertilizer rate. A 10 Gy was found to be the optimal irradiation dose for enhancing N2‐fixation. High levels of NH4 +‐N decreased the percentage and the amount of N2‐fixation, but did not affect nodule formation. However, the presowing 10 Gy irradiation dose reduced the negative effect of ammonia‐N fertilizer on N2‐fixation. Therefore, we recommend irradiating chickpea seeds with a 10 Gy dose before planting in soil containing high levels of mineral nitrogen to reduce its negative effect on N2‐fixation.  相似文献   

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