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1.
Appropriate 15N-labeling methods are crucial for estimating N2-fixation in trees used in agroforestry systems. A 4-year field experiment was conducted on an Alfisol in Southwestern Nigeria to compare the estimates of N2 fixed in Leucaena leucocephala, using two non-N2-fixing leguminous trees, Senna siamea and S. spectabilis, as reference plants and three different methods of introducing 15N into soil. The atom % 15N uptake pattern (as reflected in the leaves) was identical in both N2- and non-N2-fixing tree species irrespective of the 15N-application method. There was a significant decline in atom % 15N excess in the leaves of L. leucocephala (from 0.266 to 0.039), S. siamea (0.625 to 0.121), and S. spectabilis (from 0.683 to 0.118) from the first sampling 12 months after planting and the second sampling 18 months after sampling. From the second harvest in 1991 until the end of the experiment (fifth) harvest in 1993, however, the atom 15N % excess decline in leaves of the three species was less pronounced and depended on the method of 15N application. In those plants to which the tracer was applied once at planting, the 15N decline was steady between the second and the last prunings. In the split-application treatment, the atom 15N % excess increased slightly at the third pruning and decreased during the subsequent two prunings. The reference tree and the method of 15N application influenced the estimated proportion of N derived from atmospheric N2 by L. leucocephala, calculated as 73 and 64%, corresponding to 119 and 98 kg N ha-1 of N2 fixed per 6 months, when S. spectabilis and S. siamea were used as reference trees, respectively. The approach by which 15N-labeled fertilizer was applied to the soil in three splits gave slightly higher estimates of N derived from the atmosphere but this was of little agronomic significance because total N2 fixed was similar for all methods.  相似文献   

2.
Summary We examined the suitability of four reference crops, i.e., two non-fixing trees,Cassia siamea andEucalyptus grandis, and two uninoculated fixing trees,Leucaena leucocephala andAcacia albida, for measuring fixed N2 fixed in inoculatedL. leucocephala andA. albida grown for 36 weeks in pots. The15N isotope-dilution (involving the addition of equal amounts of labelled N fertilizer to the non-fixing and the fixing plants) and theA-value (with different amounts of labelled N fertilizer added to the fixing and the non-fixing crops) methods were used. The isotope dilution approach gave several large negative estimates of fixed N2 inA. albida. Positive and similar values of fixed N2 were measured in all four reference crops using theA-value approach. ForL. leucocephala the isotope-dilution approach gave different estimates of fixed N2, with the different reference crops; the uninoculated N2-fixing crops indicated significantly less fixed N2 than the non-fixing reference crops. Similar values for N2 fixed inL. leucocephala were obtained using the two non-fixing trees, either by the isotope-dilution or theA-value method. On average,A. albida derived about twice as much N from fertilizer asL. leucocephala. In both species, the atom %15N excess declined by about 50% in successive harvests.  相似文献   

3.
Summary A field experiment in concrete-based plots was conducted to estimate the contribution of N derived from air (Ndfa) or biological N2 fixation in Sesbania rostrata and S. cannabina (syn. S. aculeata), using various references, by the 15N dilution method. The two Sesbania species as N2-fixing reference plants and four aquatic weed species as non-N2-fixing references were grown for 65 days after sowing in two consecutive crops, in the dry and the wet seasons, under flooded conditions. Soil previously labeled with 15N at 0.26 atom % 15N excess in mineralizable N was further labeled by ammonium sulfate with 3 and 6 atom % 15N excess. The results showed that 15N enrichment of soil NH 4 + -N dropped exponentially in the first crop to half the original level in 50 days while in the second crop, it declined gradually to half the level in 130 days. The decline in 15N enrichment, in both N2-fixing and non-fixing species, was also steeper in the first crop than in the second crop. Variations in 15N enrichment among non-fixing species were smaller in the second crop. The ratio of the uptake of soil N to that of fertilizer N in N2-fixing and non-fixing species was estimated by the technique of varying the 15N level. In the second crop, this ratio in non-fixing species was higher than that in N2-fixing species. Comparable estimates of % Ndfa were obtained by using 15N enrichment of various non-fixing species. There was also good agreement between the estimates obtained by using 15N enrichment of non-fixing species and those by using soil NH 4 + -N, particularly in the second crop. By 25 days after sowing, the first crop of both Sesbania spp. had obtained 50% of total N from the atmosphere and the second crop had obtained 75%. The contribution from air increased with the age of the plant and ranged from 70% to 95% in 45–55 days. S. rostrata fixed substantially higher amounts of N2 due to its higher biomass production compared with S. cannabina. Mathematical considerations in applying the 15N dilution method are discussed with reference to these results.  相似文献   

4.
Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N2 fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha-1 of 15N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the 15N fertilizer. N2 fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N2 fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N2 fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N2-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.  相似文献   

5.
Effect of different 15N labeled sources on the estimation of N2 fixation was investigated. The combination of 15N labeled ammonium sulfate, 15N labeled plant material, and 15N labeled ammonium sulfate with unlabeled plant material, was examined in pot experiments. Two cultivars of soybean (Glycine max) and one of mungbean (Vigna radiata) were used. No significant difference was observed among the treatments for the estimation of N2 fixation. This was due to the homogeneity and stability of the 15N abundance in soil which resulted in a similar N uptake from the soil by the N2 fixing and reference crops. The plant yield, total N uptake and amount of N2 fixed were higher in the Yellow Soil than in the Andosol. The amount of N2 fixed was strongly influenced by the plant growth and consequently it affected the plant yield. The slow decomposition of plant material in the Andosol resulted in a low yield in both the N2 fixing and reference crops. Thus, the artificial decrease of the available N content in soil, by application of plant material, did not stimulate N, fixation but suppressed plant growth and N2 fixation.  相似文献   

6.
Summary Identification of legume genotypes with high N-supplying ability is important in improving and sustaining the productivity of low-input cropping systems. Hence, 15N-aided studies were made to ascertain the relative N-supplying ability of some cultivars of groundnut, a widely grown tropical legume. The study was conducted outdoors in 1991 at Kamburupitiya, Sri Lanka, in tanks filled with 64 kg soil which had been tagged by incorporating 15N-labelled plant material. Maize cv. Badra was grown as a monocrop and as an intercrop with five genotypes of groundnut, X-14, MI-1, Red Spanish, ICGV 87127, and a non-nodulating line. All the nodulating genotypes derived over 90% of their N from the atmosphere. Significant genotypic differences in N2 fixation were observed. X-14 fixed the highest amount (1.95 g plant-1), while Red Spanish the lowest (0.88 g plant-1). Intercropping of maize with nodulating groundnut significantly decreased the 15N atom excess of maize, depending on the genotype. However, this decrease did not appear to be related to the amount of N2 fixed, based on aboveground material. The per cent N derived by maize from the intercropped groundnuts varied from 17% (X-14) to 39% (Red Spanish), indicating a marked genotypic variability in N-suppling ability. X-14, which fixed the largest amounts of N2, grew most vigorously compared to other genotypes, causing a growth depression in the maize. The genotype that fixes the most N2 may therefore not necessarily have the greatest N-supplying ability. The transfer of N from the legume and the consequent improvement of N nutrition in the associated cereal in low-fertility situations is therefore expected to be high when the growth of the legume is intermediate and does not suppress the growth of the cereal.  相似文献   

7.
Summary N accumulation, nodulation, and acetylene reduction activity were measured at frequent intervals during the growth of two chickpea genotypes, and N2 fixation was estimated by an isotope-dilution method, using safflower as a non-N2-fixing reference. Safflower was more efficient at N uptake than both the chickpea genotypes for at least the first 50 days and thus could not be used as an accurate reference control. We recommend that further work should employ non-nodulatiog genotypes of chickpea as reference plants and use slow-release forms of 15N fertilizer. Direct genotype comparison by isotope dilution estimated that genotype K 850 fixed 16–18 kg ha–1 more N than G 130, and this difference was supported by the greater nodule mass and acetylene reduction activity in the K 850 cultivar. Inoculation with an ineffective chickpea Rhizobium sp. led to 69% nodulation on cultivar K 850 but only 33% on G 130. While nodule weight, N uptake, and acetylene reduction activity decreased with inoculation in K 850, the isotope dilutions were similar for both inoculation treatments. The lack of a significant effect on N2 fixation was ascribed to the partial success of inoculant establishment.Published as Journal Article No. JA 692 of the International Crops Research Institute for the Semi Arid Tropics, Patancheru, A.P. 502324, India  相似文献   

8.
The dynamics of nodulation, N2-fixation and N use in Leucaena leucocephala cv. K28 over time was investigated in a screenhouse at 4, 8, 12 and 16 months after planting (MAP) using the 15N-labelling method. Leucaena had a consistently increasing pattern of nodulation, dry biomass and nitrogen yield. A sharp rise in nodulation was observed between 12 and 16 MAP, whereas for biomass, N accumulation and N2-fixation, and N2-fixation, an upward surge occurred between 4 and 12 months. Nodulation, N accumulation, N2-fixation and biomass yield all peaked at 16 MAP. Along with the steady increase in N2-fixation throughout the 16-month growth period, the % N derived from the atmosphere rose from 17.9% to 61.5%, 70.1% and 74%, equivalent to 191, 1623, 2395 and 3385 mg N2 fixed plant-1 at 4, 8, 12 and 16 MAP, respectively. Nitrogen assimilation from soil and fertilizer decreased inversely to the increase in symbiotic nitrogen fixation with time.  相似文献   

9.
Summary It is commonly assumed that a large fraction of fertilizer N applied to a rice (Oryza sativa L.) field is lost from the soil-water-plant system as a result of denitrification. Direct evidence to support this view, however, is limited. The few direct field, denitrification gas measurements that have been made indicate less N loss than that determined by 15N balance after the growing season. One explanation for this discrepancy is that the N2 produced during denitrification in a flooded soil remains trapped in the soil system and does not evolve to the atmosphere until the soil dries or is otherwise disturbed. It seems likely, however, that N2 produced in the soil uses the rice plants as a conduit to the atmosphere, as does methane. Methane evolution from a rice field has been demonstrated to occur almost exclusively through the rice plants themselves. A field study in Cuttack, India, and a greenhouse study in Fort Collins, Colorado, were conducted to determine the influence of rice plants on the transport of N2 and N2O from the soil to the atmosphere. In these studies, plots were fertilized with 75 or 99 atom % 15N-urea and 15N techniques were used to monitor the daily evolution of N2 and N2O. At weekly intervals the amount of N2+N2O trapped in the flooded soil and the total-N and fertilized-N content of the soil and plants were measured in the greenhouse plots. Direct measurement of N2+N2O emission from field and greenhouse plots indicated that the young rice plant facilitates the efflux of N2 and N2O from the soil to the atmosphere. Little N gas was trapped in the rice-planted soils while large quantities were trapped in the unplanted soils. N losses due to denitrification accounted for only up to 10% of the loss of added N in planted soils in the field or greenhouse. The major losses of fertilizer N from both the field and greenhouse soils appear to have been the result of NH3 volatilization.  相似文献   

10.
Abstract

A study was carried out to compare the difference or N-yield method with the 15N natural abundance method for the estimation of the fractional contribution of biological N2 fixation in the different plant parts of nodulating and non-nodulating isolines of soybeans. The results indicated that the δ15N values of most plant parts of soybeans were significantly lower (p<0.05) in the nodulating than in the non-nodulating isoline. However, in the case of the root+nodule component, the δ15N value was higher in the nodulating than in the non-nodulating isoline possibly due to isotopic discrimination of 15N over 14N which may have occurred in the nodules. Inoculation of soybeans with the Bradyrhizobium japonicum strain CB 1809 increased significantly (p<0.05) the δ15N value of the root+nodule component implying that the effectiveness of the soybean-rhizobium symbiosis had increased by inoculation.

Percentage of plant N derived from atmospheric N2 fixation (%Ndfa) estimated by the 15N natural abundance method was highly correlated (r=0.762, p<0.01) with that by the difference or N-yield method and the differences between the two methods were not statistically significant. The agreement between the two methods was closer at maturity than at the early reproductive stage.

The %Ndfa obtained by the difference method ranged from 48.4 to 92.6% whereas the %Ndfa obtained by the 15N natural abundance method ranged from 43.2 to 92.4% in the different plant parts. Based on the 15N natural abundance method, approximately 15% of the N in pod, shoot, grain, and shell was derived from the soil but in the case of stover, this fraction was about 55%.  相似文献   

11.
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   

12.
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   

13.
Summary The proportion of N derived from N2 fixation for 99 strains ofAzolla spp. (comprising all known species) in the presence of ammonium (40 mg/1) was assessed using a15N-dilution technique. The percentage of N derived from air varied from 29.5% to 79.9%. Although the N concentration ofAzolla spp. was not correlated with fertilizer N, it correlated fairly well with N2 fixation. Regression analysis suggests that the N yield ofAzolla spp. is more dependent on N2 fixation than on ammonium assimilation. The high correlation between N yield and isotopically determined, fixed N2 indicates that the N yield could be used as a parameter in the selection ofAzolla spp. strains that are capable of maintaining high N2 fixation in the presence of a high level of ammonium.  相似文献   

14.
Pot experiments were conducted with two soils, from Rottenhaus and Seibersdorf in Austria, to ascertain whether the rate of fertilizer N application and the test crop would influence the amount of N available in the soil as assessed by the A-value method. 15N-labelled fertilizer was applied at rates of 10, 25, 40, 60, and 100 mg N kg-1 soil, corresponding approximately to 20, 50, 80, 120 and 200 kg N ha-1 respectively, and two crop species, barley (Hordeum vulgareL.) and non-nodulating soybean (Glycine max L.) were used to determine the soil A N value under the various fertilizer regimes. The results showed that the Rottenhaus soil had a higher A N value than the Seibersdorf soil, suggesting that the former was more fertile than the latter. The A N values of both soils were significantly affected by the level of N application. When grown in the same soil, the two test crops showed significantly different fertilizer use efficiency and per cent N derived from fertilizer when the rate of N application exceeded 20 kg ha-1. Thus, the A N value as determined by the two test crops differed significantly for the same soil when the rate of N application was greater than 20 kg/ha. The difference was greater when the soil fertility level was high. The dependence of the A N value on the level of N application and the species of crop seriously compromises the suitability of this method for determining plant-associated N2 fixation. Hence, considerable caution is required when using this method to estimate plant-associated N2 fixation.  相似文献   

15.
Summary Leptochloa fusca (L.) Kunth (kallar grass) has previously been found to exhibit high rates of nitrogen fixation. A series of experiments to determine the level of biological nitrogen fixation using 15N isotopic dilution were carried out in nutrient solution and saline soil. In the nutrient solution, E. coli inoculated plants were taken as non-nitrogen-fixing control. It was observed that nearly 60%–80% of the plant N was derived from atmospheric fixation. Estimations based on the N difference method gave much lower values (18%–35%). In experiments with saline soil which was initially sterilized with chloroform fumigation, a mixed culture of N2-fixing rhizospheric isolates from kallar grass roots was inoculated and planted to kallar grass. Uninoculated treatments were regarded as controls. The soil was previously labelled with 15N by adding cellulose and (15NH4)2SO4. The results of these studies showed fixation values of 6%–32% when estimated by 15N dilution, whereas by the N difference method 54% of the plant N was estimated to be derived from fixation. This discrepancy is due to the increase in root proliferation due to inoculation, which results in greater uptake of soil N. The distribution of 15N in different fractions of the soil-N indicted isotopic dilution due to bacterial fixation of atmospheric N2.  相似文献   

16.
Summary Three15N isotopic dilution methods (15N natural abundance, labelled mineral fertilizer, and organic matter) were used to determine the proportion of N derived from different available sources in seedlines ofAlnus glutinosa andPopulus nigra planted together or in monoculture under natural climatic conditions. The proportion of N derived from N2 fixation in associated alders was appreciably higher than that determined in monoculture. The reduction of soil N uptake by associated alders contributed to an increase in total plant N and biomass production in associated poplars. When slightly N-labelled organic matter (alder leaf litter) was incorporated into the soil, 10–15% of its initial N content was recovered in poplar tissues, showing that this N source makes an important contribution to the N yield of associated non-fixing plants. There were no significant differences between the results obtained by15N natural abundance and those obtained by labelled fertilizer methods, suggesting that the 15N method could be used to evaluate annual N budgets in natural ecosystems.  相似文献   

17.
Summary Biological N2 fixation was estimated in a field experiment following the addition of NH4Cl or KNO3 to unconfined microplots (1.5 m2) at 2.5 g N m-2 (10 atom% 15N). A model of total N and 15N accumulation in lupins and decreasing 15N enrichment in the KCl-extractable soil-N pool (0–0.15 m depth) was used to estimate the proportion of N in lupins derived from biological N2 fixation. Estimates of N2 fixation derived from the model were compared with 15N isotope-dilution estimates obtained using canola, annual ryegrass, and wheat as nonfixing reference plants. Biomass, total N accumulation, or 15N enrichment in the lupin and reference crops did not differ whether NH inf4 sup+ or NO inf3 sup- was added as the labelled inorganic-N source. The decrease in soil 15N enrichment was described by first-order kinetics, whereas total N and 15N accumulation in the lupins were described by logistical equations. Using these equations, the uptake of soil N by lupins was estimated and was then used to calculate fixed N2. Estimates of N2 fixation derived from the model increased from 0 at 50 days after sowing to a maximum of 0.79 at 190 days after sowing. Those based on the 15N enrichment of the NO inf3 sup- pool were 10% higher than those based on the mineral-N pool. 15N isotope-dilution estimates of N2 fixation ranged from 0.37 to 0.55 at 68 days after sowing and from 0.71 to 0.77 at 190 days after sowing. Reference plant-derived values of N2 fixation were all higher than modelled estimates during the early states of growth, but were similar to modelled estimates at physiological maturity. The use of the model to estimate N2 derived from the atmosphere has the intrinsic advantage that the need for a non-fixing reference plant is avoided.  相似文献   

18.
The variation in P uptake and use efficiency and N accumulation by Gliricidia sepium (N2-fixing tree), Senna siamea and S. spectabilis (leguminous non-N2-fixing trees) were examined in the field at Fashola (savanna zone), southwestern Nigeria, using four P rates, 0, 20, 40 and 80 kg P ha-1. Growth of G. sepium and S. spectabilis responded to P application at 24 weeks after planting (WAP) and average yield increases of 58% and 145% were observed by the application of 40 kg P ha-1 for the two species, respectively. Such a P response was not found in S. siamea at 24 WAP and for any of the species at 48 WAP. G. sepium accumulated more P (on average 162%) than S. siamea and S. spectabilis at 24 WAP and had greater root length and a higher percentage of mycorrhizal infection. However, at 48 WAP S. siamea had 2.5 times more P than G. sepium. Differences in the physiological P use efficiency (PPUE) between G. sepium and the non-N2-fixing trees were significant at the 0 P level, being higher for S. siamea (average, 0.61 g shoot mg-1 P) than for G. sepium (0.27 g shoot mg-1 P). G. sepium had a consistently lower atom % 15N than S. spectabilis, while that of S. siamea for most of the time did not differ from that of G. sepium. The reference plant affected N2 fixation extimates, with negative values and a higher variability (CV 60%) associated with S. siamea than with S. spectabilis (CV<20%). Consequently, S. spectabilis was selected as a better reference plant for measuring N2 fixation in G. sepium. G. sepium fixed on average 35% and 54% of its N at 24 and 48 WAP, respectively. Except at the lowest P rate, percentage and amount of N fixed were not generally enhanced by P application.  相似文献   

19.
Dual natural abundance analysis of 15Nitrogen (N) and 13Carbon (C) isotopes in lentil plants subjected to different soil moisture levels and rates of potassium (K) fertilizer were determined to assess crop performance variability in terms of growth and N2-fixation (Ndfa). The δ15N values in lentils ranged from +0.67 to +1.36‰; whereas, those of the N2-fixed and reference plant were ?0.45 and +2.94‰, respectively. Consequently, the Ndfa% ranged from 45 and 65% of total plant N uptake. Water stress reduced Δ13C values. However, K fertilization enhanced whole plant Δ13C along with dry matter yield and N2-fixation. The water stressed plants amended with K fertilizer seemed to be the best treatment because of its highest pod yield, high N balance, and N2-fixation with low consumption of irrigation water. This illustrates the ecological and economical importance of K fertilizer in alleviating water stress occurring during the post-flowering period of lentil.  相似文献   

20.
Summary In a series of short-term experiments root systems of young sorghum and millet plants inoculated with N2-fixing bacteria were exposed to 15N2-enriched atmospheres for 72 h. The plants were grown in a normal atmosphere for up to 22 days after the end of the exposure to allow them to take up the fixed N2. Environmental conditions and genotypes of sorghum and millet were selected to maximise N2-fixation in the rhizosphere. Detectable amounts of fixed N (> 16 g/plant) were rapidly incorporated into sorghum plants grown in a sand/farmyard manure medium, but measurable fixation was found on only one occasion in plants grown in soil. N2 fixation was detectable in some experiments with soil-grown millet plants but the amounts were small (2–4 g/plant) and represented less than 1 % of plant N accumulated over the same period. In many cases there was no detectable 15N2 incorporation despite measurable increases in ethylene concentration found during an acetylene reduction assay.Published as ICRISAT Journal Article No. JA 740  相似文献   

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