共查询到20条相似文献,搜索用时 15 毫秒
1.
P. M. Chalk 《Plant and Soil》1991,132(1):29-39
During the past 10 years estimates of N2 fixation associated with sugar cane, forage grasses, cereals and actinorhizal plants grown in soil with and without addition of inoculum have been obtained using the 15N isotope dilution technique. These experiments are reviewed in this paper with the aim of determining the proportional and absolute contribution of N2 fixation to the N nutrition of non-legumes, and its role as a source of N in agriculture. The review also identifies deficiencies in both the totality of data which are currently available and the experimental approaches used to quantify N2 fixation associated with non-legumes.Field data indicate that associative N2 fixation can potentially contribute agronomically-significant amounts of N (>30–40 kg N ha-1 y-1) to the N nutrition of plants of importance in tropical agriculture, including sugar cane (Saccharum sp.) and forage grasses (Panicum maximum, Brachiaria sp. and Leptochloa fusca) when grown in uninoculated, N-deficient soils. Marked variations in proportions of plant N derived from the atmosphere have been measured between species or cultivars within species.Limited pot-culture data indicate that rice can benefit naturally from associative N2 fixation, and that inoculation responses due to N2 fixation can occur. Wheat can also respond to inoculation but responses do not appear to be due to associative N2 fixation. 15N dilution studies confirm that substantial amounts of N2 can be fixed by actinorhizal plants. 相似文献
2.
Sang H. Lee Terry E. Whitledge 《Journal of experimental marine biology and ecology》2008,367(2):204-212
The primary production of bottom ice algae is an important food source for sympagic, pelagic and benthic organisms in the Arctic Ocean as well as Antarctic Ocean. Using 13C-15N isotope tracers, the recent ice algal production at Barrow during the spring season was lower in 2003 than three decades ago, although the maximum chlorophyll-a concentration for the bottom ice algae was similar to the values from previous studies. Estimated recent new and total production rates of the ice algae were 0.8 g C m- 2 yr- 1 and 2.0 g C m- 2 yr- 1 respectively, while the rates of water column phytoplankton were 0.2 g C m- 2 yr- 1 and 0.7 g C m- 2 yr- 1 for the spring sampling period in 2003. The ice algae contributed 74% of the pelagic primary production under the landfast sea ice at Barrow before the phytoplankton spring bloom. At the end of the season in 2003, a high carbon allocation of lipids in the ice algae was found. Three possible explanations- nutrient depletion, increasing light, and/or changes in species composition- were suggested for the high carbon incorporation into lipids. This high lipid synthesis of the bottom ice algae might be significant to zooplankton and benthic fauna grazers because lipids are the most energy dense biomolecules. 相似文献
3.
W.K. Fitt R.D. Gates J.C. Bythell A.G. Grottoli P. Fisher O. Pantos D.J. Franklin J.M. Torregiani M.P. Lesser 《Journal of experimental marine biology and ecology》2009,373(2):102-1107
The role of both host and dinoflagellate symbionts was investigated in the response of reef-building corals to thermal stress in the light. Replicate coral nubbins of Stylophora pistillata and Porites cylindrica from the GBR were exposed to either 28 °C (control) or 32 °C for 5 days before being returned to an ambient reef temperature (28 °C). S. pistillata was found to contain either Symbiodinium genotype C1 or C8a, while P. cylindrica had type C15 based on ITS genotyping. Analysis of the quantum yield of photosystem (PS) II fluorescence of the symbionts in P. cylindrica showed that light-induced excitation pressure on the C15 Symbiodinium was significantly less, and the steady state quantum yield of PSII fluorescence at noon (ΔF/Fm′) greater, than that measured in C1/C8a Symbiodinium sp. from S. pistillata. Immunoblots of the PS II D1 protein were significantly lower in Symbiodinium from S. pistillata compared to those in P. cylindrica after exposure to thermal stress. The biochemical markers, heat-stress protein (HSP) 70 and superoxide dismutase (SOD), were significantly greater in P. cylindrica before the experiment, and both species of coral increased their biosynthesis of HSP 70 and SOD when exposed to thermal stress. Concentrations of MAAs, glycerol, and lipids were not significantly affected by thermal stress in these experiments, but DNA damage was greater in heat-stressed S. pistillata compared to P. cylindrica. There was minimal coral mucus, which accounts for up to half of the total energy budget of a coral and provides the first layer of defense for invading microbes, produced by S. pistillata after heat stress compared to P. cylindrica. It is concluded that P. cylindrica contains a heat resistant C15 Symbiodinium and critical host proteins are present at higher concentrations than observed for S. pistillata, the combination of which provides greater protection from bleaching conditions of high temperature in the light. 相似文献
4.
Summary Immobilization and mineralization of the tracer nitrogen (K15NO3) applied to the soil together with several organic matters during their decomposition was investigated in incubation experiments.After incubation for three months at 30°C, the decomposition rates of rice straw, hardwood bark, sawdust, softwood bark and peat moss were 41, 15, 7, 5, and 5%, respectively. After incubation for three months at 30°C, 100 and 80% of the fertilizer nitrogen were immobilized in the treatment with 2.0% of rice straw and sawdust carbon, respectively. These resulted in the lowered uptake of the fertilizer nitrogen by plants. In case of peat moss and barks, the amount of fertilizer nitrogen which transformed to the organic nitrogen fractions was quite small and the plant uptake of the nitrogen was hardly affected. Remineralization of the immobilized nitrogen was clearly observed after 2 months' incubation in case where rice straw carbon was added to the extent of 0.5 and 1.0%, but it was not observed in case where other organic matter carbon was added.The data showed that peat moss and barks were highly resistant to the action of microorganisms. As a results the immobilization process of the fertilizer nitrogen incubated with these organic matter was quite slow. 相似文献
5.
Analysis of stable isotope ratios is increasingly used to reconstruct diets in passerine birds, but studies of diet–tissue
isotopic discrimination for this avian group are scarce. We determined 15N and 13C diet–tissue discrimination factors on whole blood in the red-throated ant tanager (Habia fuscicauda), an insectivorous–frugivorous passerine. Birds were fed an isotopically uniform, semi-synthetic diet of dog puppy dry food,
soy protein isolate, wheat germ, and other ingredients, during 92 days. Average (± SD) diet–tissue discrimination was 2.6 ± 0.2‰
for N and 2.2 ± 0.1‰ for C. Nitrogen diet-tissue discrimination was similar to the values found previously in other passerines
fed animal protein and it can probably be used to accurately reconstruct protein dietary origin in passerines feeding on animal
protein (e.g., insects). In the case of C, diet reconstruction might be affected by metabolic routing of dietary nutrients. 相似文献
6.
Voisin Anne-Sophie Salon Christophe Munier-Jolain Nathalie G. Ney Bertrand 《Plant and Soil》2002,243(1):31-42
The influence of soil nitrate availability, crop growth rate and phenology on the activity of symbiotic nitrogen fixation (SNF) during the growth cycle of pea (Pisum sativum cv. Baccara) was investigated in the field under adequate water availability, applying various levels of fertiliser N at the time of sowing. Nitrate availability in the ploughed layer of the soil was shown to inhibit both SNF initiation and activity. Contribution of SNF to total nitrogen uptake (%Ndfa) over the growth cycle could be predicted as a linear function of mineral N content of the ploughed layer at sowing. Nitrate inhibition of SNF was absolute when mineral N at sowing was over 380 kg N ha–1. Symbiotic nitrogen fixation was not initiated unless nitrate availability in the soil dropped below 56 kg N ha–1. However, SNF could no longer be initiated after the beginning of seed filling (BSF). Other linear relationships were established between instantaneous %Ndfa and instantaneous nitrate availability in the ploughed layer of the soil until BSF. Instantaneous %Ndfa decreased linearly with soil nitrate availability and was nil above 48 and 34 kg N ha–1 for the vegetative and reproductive stages, respectively, levels after which no SNF occurred. Moreover, SNF rate was shown to be closely related to the crop growth rate until BSF. The ratio of SNF rate over crop growth rate decreased linearly with thermal time. Maximum SNF rate was about 40 mg N m–2 degree-day–1, equivalent to 7 kg N ha–1, regardless of the N treatment. From BSF to the end of the growth cycle, the high N requirements of the crop were supported by both SNF and nitrate root absorption but, of the two sources, nitrate root absorption seemed to be less affected by the presence of reproductive organs. However, since soil nitrate availability was low at the end of the growth cycle, SNF was the main source of nitrogen acquisition. The onset of SNF decrease at the end of the growth cycle seemed to be first due to nodule age and then associated to the slowing of the crop growth rate. 相似文献
7.
Christine L. Goodale Steven A. Thomas Guinevere Fredriksen Emily M. Elliott Kathryn M. Flinn Thomas J. Butler M. Todd Walter 《Biogeochemistry》2009,93(3):197-218
Atmospheric deposition contributes a large fraction of the annual nitrogen (N) input to the basin of the Susquehanna River,
a river that provides two-thirds of the annual N load to the Chesapeake Bay. Yet, there are few measurements of the retention
of atmospheric N in the Upper Susquehanna’s forested headwaters. We characterized the amount, form (nitrate, ammonium, and
dissolved organic nitrogen), isotopic composition (δ15N- and δ18O-nitrate), and seasonality of stream N over 2 years for 7–13 catchments. We expected high rates of N retention and seasonal
nitrate patterns typical of other seasonally snow-covered catchments: dormant season maxima and growing season minima. Coarse
estimates of N export indicated high rates of inorganic N retention (>95%), yet streams had unexpected seasonal nitrate patterns,
with summer peaks (14–96 μmol L−1), October crashes (<1 μmol L−1), and modest rebounds during the dormant season (<1–20 μmol L−1). Stream δ18O-nitrate values indicated microbial nitrification as the primary source of stream nitrate, although snowmelt or other atmospheric
source contributed up to 47% of stream nitrate in some March samples. The autumn nitrate crash coincided with leaffall, likely
due to in-stream heterotrophic uptake of N. Hypothesized sources of the summer nitrate peaks include: delayed release of nitrate
previously flushed to groundwater, weathering of geologic N, and summer increases in net nitrate production. Measurements
of shale δ15N and soil-, well-, and streamwater nitrate within one catchment point toward a summer increase in soil net nitrification
as the driver of this pattern. Rather than seasonal plant demand, processes governing the seasonal production, retention,
and transport of nitrate in soils may drive nitrate seasonality in this and many other systems. 相似文献
8.
S. Nayar G.J. Collings S. Bryars 《Journal of experimental marine biology and ecology》2009,373(2):87-95
Productivity measurements from carbon uptake have been suggested as good indicators of the physiological health of seagrasses. As seagrasses acquire carbon from the surrounding water, the rate of uptake often provide a good measure of the efficiency at which seagrasses meet their resource demands for growth. This rate is often used to assess the photosynthetic efficiency of the plants, a proxy for the physiological status of seagrass. This has special relevance to the Adelaide region as over 5000 ha of seagrasses have been lost from Adelaide coastal waters over the last 70 years, with much of this loss attributed to nutrient inputs from wastewater, industrial and stormwater discharges. This study used an in-situ inorganic carbon isotope-labelling and spike approach to obtain ecologically relevant estimates of seasonal variability in carbon uptake and its allocation in two species of temperate seagrass common to this coast (Amphibolis antarctica and Posidonia angustifolia). Uptake of carbon by the seagrass complex (leaves, roots, phytoplankton and epiphytes) was affected by both season and species. Carbon uptake rates of phytoplankton were generally higher than other components of the system. Uptake rates ranged from 0.01 mg C g− 1 DW h− 1 (summer) to 0.61 mg C g− 1 DW h− 1 (spring) in Posidonia and 0.02 mg C g− 1 DW h− 1 (summer) to 0.93 mg C g− 1 DW h− 1 (winter) in Amphibolis. Carbon uptake by the Amphibolis complex was higher than in the Posidonia complex. The Amphibolis complex had higher uptake rates in summer whereas the Posidonia complex was higher in spring. Fine sediments probably from a nearby dredging operation, are likely to have resulted in lower carbon uptake and a reduction in the above-ground and below-ground biomass in summer. 相似文献
9.
Sylvie Ferrario-Méry Marie-Christine Thibaud Thomas Betsche Marie-Hélène Valadier Christine H. Foyer 《Planta》1997,202(4):510-521
Transformed plants of Nicotiana plumbaginifolia Viv. constitutively expressing nitrate reductase (35S-NR) or β-glucuronidase (35S-GUS) and untransformed controls were grown
for two weeks in a CO2-enriched atmosphere. Whereas CO2 enrichment (1000 μl · l−1) resulted in an increase in the carbon (C) to nitrogen (N) ratio of both the tobacco lines grown in pots with vermiculite,
the C/N ratio was only slightly modified when plants were grown in hydroponic culture in high CO2 compared to those grown in air. Constitutive nitrate reductase (NR) expression per se did not change the C/N ratio of the
shoots or roots. Biomass accumulation was similar in both types of plant when hydroponic or pot-grown material, grown in air
or high CO2, were compared. Shoot dry matter accumulation was primarily related to the presence of stored carbohydrate (starch and sucrose)
in the leaves. In the pot-grown tobacco, growth at elevated CO2 levels caused a concomitant decrease in the N content of the leaves involving losses in NO−
3 and amino acid levels. In contrast, the N content and composition were similar in all plants grown in hydroponic culture.
The 35S-NR plants grown in air had higher foliar maximum extractable NR activities and increased glutamine levels (on a chlorophyll
or protein basis) than the untransformed controls. These increases were maintained following CO2 enrichment when the plants were grown in hydroponic culture, suggesting that an increased flux through nitrogen assimilation
was possible in the 35S-NR plants. Under CO2 enrichment the NR activation state in the leaves was similar in all plants. When the 35S-NR plants were grown in pots, however,
foliar NR activity and glutamine content fell in the 35S-NR transformants to levels similar to those of the untransformed
controls. The differences in NR activity between untransformed and 35S-NR leaves were much less pronounced in the hydroponic
than in the pot-grown material but the difference in total extractable NR activity was more marked following CO2 enrichment. Foliar NR message levels were decreased by CO2 enrichment in all growth conditions but this was much more pronounced in pot-grown material than in that grown hydroponically.
Since β-glucuronidase (GUS) activity and message levels in 35S-GUS plants grown under the same conditions of CO2 enrichment (to test the effects of CO2 enrichment on the activity of the 35S promoter) were found to be constant, we conclude that NR message turnover was specifically
accelerated in the 35S-NR plants as well as in the untransformed controls as a result of CO2 enrichment. The molecular and metabolic signals involved in increased NR message and protein turnover are not known but possible
effectors include NO3
−, glutamine and asparagine. We conclude that plants grown in hydroponic culture have greater access to N than those grown
in pots. Regardless of the culture method, CO2 enrichment has a direct effect on NR mRNA stability.
Received: 17 October 1996 / Accepted: 11 February 1997 相似文献
10.
Mineralization of organically bound nitrogen in soil as influenced by plant growth and fertilization
L. H. Sørensen 《Plant and Soil》1982,65(1):51-61
Summary A loam soil containing an organic fraction labelled with15N was used for pot experiments with spring barley, rye-grass and clover. The organically bound labelled N was mineralized at a rate corresponding to a half-life of about 9 years. Fertilization with 106 and 424 kgN/ha of unlabelled N in the form of KNO3 significantly increased uptake of labelled N from the soil in barley and the first harvest of rye-grass crops. The fertilized plants removed all the labelled NH4 and NO3 present in the soil, whereas the unfertilized plants removed only about 80%. The second, third and fourth harvests of the unfertilized rye-grass took up more labelled N than the fertilized rye-grass. The total uptake in the four harvests was similar whether the plants were fertilized or not. Application of KCl to barley plants in amounts equivalent to that of KNO3 resulted in a small but insignificant increase in uptake of labelled N. The uptake of labelled N in the first harvest of clover which was not fertilized but inoculated with Rhizobium was similar to that of the fully fertilized rye-grass indicating that the biological fixation of N had the same effect as addition of N-fertilizer. N uptake in the following harvests was lower and the total uptake by four harvests of clover was similar to that of rye-grass. There was no indication that fertilization with KNO3 accelerated the mineralization of the organically bound labelled N. The observed apparent ‘priming effect’ of the fertilizer on the uptake of labelled N was compensated by subsequent crops and harvests, and it seems to arise from a more thorough search of the soil volume by a better developed root system of the fertilized plants. 相似文献
11.
Nitrogen losses in puddled soils as affected by timing of water deficit and nitrogen fertilization 总被引:2,自引:0,他引:2
Erratic rainfall in rainfed lowlands and inadequate water supply in irrigated lowlands can results in alternate soil drying and flooding during a rice (Oryza sativa L.) cropping period. Effects of alternate soil drying and flooding on N loss by nitrification-denitrification have been inconsistent in previous field research. To determine the effects of water deficit and urea timing on soil NO3 and NH4, floodwater NO3, and N loss from added 15N-labeled urea, a field experiment was conducted for 2 yr on an Andaqueptic Haplaquoll in the Philippines. Water regimes were continuously flooded, not irrigated from 15 to 35 d after transplanting (DT), or not irrigated from 41 to 63 DT. The nitrogen treatments in factorial combination with water regimes were no applied N and 80 kg urea-N ha–1, either applied half basally and half at 37 DT or half at 11 DT and half at 65 DT. Water deficit at 15 to 35 DT and 41 to 63 DT, compared with continuous soil flooding, significantly reduced extractable NH4 in the top 30-cm soil layer and resulted in significant but small (<1.0 kg N ha–1) soil NO3 accumulations. Soil NO3, which accumulated during the water deficit, rapidly disappeared after reflooding. Water deficit at 15 to 35 DT, unlike that at 41 to 63 DT, increased the gaseous loss of added urea N as determined from unrecovered 15N in 15N balances. The results indicate that application of urea to young rice in saturated or flooded soil results in large, rapid losses of N (mean = 35% of applied N), presumably by NH3 volatilization. Subsequent soil drying and flooding during the vegetative growth phase can result in additional N loss (mean = 14% of applied N), presumably by nitrification-denitrification. This additional N loss due to soil drying and flooding decreases with increasing crop age, apparently because of increased competition by rice with soil microorganisms for NH4 and NO3. 相似文献
12.
Isotopic composition of nitrate-nitrogen as a marker of riparian and benthic denitrification at the scale of the whole Seine River system 总被引:12,自引:2,他引:12
Nitrogen budgets established for large river systems reveal that up to 60% of the nitrate exported from agricultural soils is eliminated, either when crossing riparian wetlands areas before even reaching surface waters, or within the rivers themselves through benthic denitrification. The study of nitrogen isotope ratios of riverine nitrates could offer an elegant means to assess the extent of denitrification and thus confirm these budgets, as it is known that denitrification results in a natural 15N enrichment of residual nitrates. The results reported here, for the Seine river system (France), demonstrate the feasibility of this isotopic approach at the scale of large watersheds. On the basis of in situ observations carried out in a large storage reservoir in the upstream Seine catchment (Der Lake), where intensive benthic denitrification occurs, as well as on the basis of laboratory experiments of denitrification under controlled conditions, it is shown that the isotopic discrimination associated with benthic denitrification is minimal ( of NO3-N ranging from –1.5 to –3.6), probably because the rate-limiting step of the process consists of nitrate diffusion through the water-sediment interface. Riparian denitrification on the contrary, when it implies nitrate reduction during convective transfer through reducing environements, causes a much more significant isotopic enrichment of 15N of residual nitrate ( about –18). The authors report measurements of nitrogen isotopic composition of nitrate from rivers of various stream orders in the Seine river system under summer conditions. Anomalies in the data with respect to the values expected from the mixture of the various sources of nitrate are here attributed to riparian denitrification. However, the authors show that because of the patchy distribution of actively denitrifying riparian zones within the drainage network, the isotopic signature conferred to residual nitrate in river water intrinsically provides only a minimum estimate of the extent of denitrification. 相似文献
13.
This study was conducted to examine the effects of varying N rates and cropping systems (mixedversus pure stand) on the suitability of oats (Avena sativa L.) for estimating N2 fixed in sequentially harvested vetch (Vicia sativa L.) over two growing seasons (1984–85 and 1985–86). The N rates were, 20 and 100 kg N ha–1 in 1984–85 and 15 and 60 kg N ha–1 in 1985–86. In the 1984–85 season, vetch at maturity derived 76 and 63% N from fixation at the high and low N rates respectively. The corresponding values for the second season were 66 and 42%. Except in the 1985–86 season when some significantly higher values of % N2 fixed were estimated by using the reference crop grown at the higher (A-value approach) than at the lower N rate (isotope-dilution approach), both approaches resulted in similar measurements of N2 fixed. In the 1984–85 season, similar values of N2 fixed were obtained using either the pure or mixed stand oats reference crops. Although in the 1985–86 season, the mixed reference crop occasionally estimated lower % N2 fixed than pure oats, total N2 fixed estimates were always similar (P<0.05). Thus, in general, N fertilization and cropping system of the reference crop did not significantly influence estimates of N2 fixation. 相似文献
14.
Translocation of carbon and nitrogen within a single source-sink unit, comprising a trifoliated leaf, the axillary pod and the subtending internode, and from this unit to the rest of the plant was examined in soybean (Glycine max L. cv. Akishirome) plant by feeding 13CO2 and 15NO3. The plants were grown at two levels of nitrogen in the basal medium, i.e. low-N (2 g N m–2) and high-N (35 g N m–2) and a treatment of depodding was imposed by removing all the pods from the plant, except the pod of the source sink unit, 13 days after flowering. The plants at high-N accumulated more biomass in its organs compared to low-N and pod removal increased the weight of the vegetative organs. When the terminal leaflet of the source-sink unit was fed with 13CO2, almost all of the radioactive materials were retained inside the source-sink unit and translocation to rest of the plants was insignificant under any of the treatments imposed. Out of the13C exported by the terminal leaflet, less than half went into the axillary pod, as the lateral leaflets claimed equal share and very little material was deposited in the petiole. Pod removal decreased 13C export at high-N , but not at low-N. Similar to 13C, the source-sink unit retained all the 15N fed to the terminal leaflet at high-N. At low-N, the major part of 15N partitioning occurred in favour of the rest of the plant outside the source-sink unit, but removal of the competitve sinks from the rest of the plants nullified any partitioning outside the unit. Unlike the situation in 13C, no partitioning of 15N occurred in favour of the lateral leaflets from the terminal leaflet inside the unit. It is concluded that sink demand influences partitioning of both C and N and the translocation of carbon is different from that of nitrogen within a source-sink unit. The translocation of the N is more adjustive to a demand from other sink units compared to the C. 相似文献
15.
The effect of incorporating cattle slurry in soil, either by mixing or by simulated injection into a hollow in soil, on the ryegrass uptake of total N and 15NH4+-N was determined in three soils of different texture. The N accumulation in Italian ryegrass (Lolium multiflorum L.) from slurry N and from an equivalent amount of NH4+-N in (15NH4) SO4 (control) was measured during 6 months of growth in pots. After this period the total recovery of labelled N in the top soil plus herbage was similar in the slurry and the control treatments. This indicated that gaseous losses from slurry NH4+-N were insignificant. Consequently, the availability of slurry N to plants was mainly influenced by the mineralization-immobilization processes. The apparent utilization of slurry NH4+-N mixed into soil was 7%, 14% and 24% lower than the utilization of (NH4)2SO4-N in a sand soil, a sandy loam soil and a loam soil, respectively. Thus, the net immobilization of N due to slurry application increased with increasing soil clay content, whereas the recovery in plants of 15N-labelled NH4+-N from slurry was similar on the three soils. A parallel incubation experiment showed that the immobilization of slurry N occurred within the first week after slurry application. The incorporation of slurry N by simulated injection increased the plant uptake of both total and labelled N compared to mixing the slurry into the soil. The apparent utilization of injected slurry NH4+-N was 7% higher, 8% lower and 4% higher than the utilization of (NH4)2SO4-N in the sand, the sandy loam and the loam soil, respectively. It is concluded that the spatial distribution of slurry in soil influenced the net mineralization of N to the same degree as did the soil type. 相似文献
16.
Ihsan ul Haq Leopold Mayr Jorge Hendrichs Christian Stauffer 《Journal of insect physiology》2010,56(12):1807-1815
The application of methoprene, and providing access to diet including hydrolyzed yeast, are treatments known to enhance mating success in the male melon fly Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), supporting their use in mass rearing protocols for sterile males in the context of sterile insect technique (SIT) programmes. The objective of the present laboratory study was to investigate the effect of methoprene application and diet supplementation with hydrolyzed yeast (protein) on the turnover of body lipids and protein to confirm the feasibility of their application in melon fly SIT mass-rearing programmes. While females had access to a diet that included hydrolyzed yeast (protein), males were exposed to one of the following treatments: (1) topical application of methoprene and access to diet including protein (M+P+); (2) only diet including protein (M−P+); (3) only methoprene (M+P−) and (4) untreated, only sugar-fed, control males (M−P−). Total body carbon (TBC) and total body nitrogen (TBN) of flies were measured at regular intervals from emergence to 35 days of age for each of the different treatments. Nitrogen assimilation and turnover in the flies were measured using stable isotope (15N) dilution techniques. Hydrolyzed yeast incorporation into the diet significantly increased male body weight, TBC and TBN as compared to sugar-fed males. Females had significantly higher body weight, TBC and TBN as compared to all males. TBC and TBN showed age-dependent changes, increasing until the age of sexual maturity and decreasing afterwards in both sexes. Methoprene treatment did not significantly affect TBC or TBN. The progressive increase with age of TBC suggests that lipogenesis occurs in adult male B. cucurbitae, as is the case in other tephritids. Stable isotope dilution was shown to be an effective method for determining N uptake in B. cucurbitae. This technique was used to show that sugar-fed males rely solely on larval N reserves and that the N uptake rate in males with access to diet including hydrolyzed yeast was higher shortly after emergence and then stabilized. The implications of the results for SIT applications are discussed. 相似文献
17.
Summary Heterotrophic nitrogen fixation by rhizosphere soil samples from 20 rice cultivars grown under uniform field conditions was estimated employing15N-tracer technique. Rhizosphere soil samples from different rice cultivars showed striking differences with regard to their ability to incorporate15N2. Rhizosphere samples from rice straw-amended (3 and 6 tons/ha) soil exhibited more pronounced nitrogen-fixing activity than the samples from unamended soil; while the activity of the rhizosphere samples from soils receiving combined nitrogen (40 and 80 kg N/ha) was relatively low. However, the inhibitory effect of combined nitrogen was not expressed in the presence of rice straw at 6 tons/ha. Results suggest that plant variety, application of combined nitrogen and organic matter influence the rhizosphere nitrogen fixation. 相似文献
18.
In situ 15N-labelling was used to provide a quantitative assessment of the total contribution of lupin (Lupinus angustifolius) to below-ground (BG) N accumulation during a growing season under field conditions, and to directly trace the fate of the
lupin BG N in the next season, including quantifying the N benefit from lupin to a following wheat (Triticum aestivum) crop. The experiments were conducted at two sites, both experiencing a semi-arid Mediterranean-type climate in the wheat-growing
region of Western Australia but with differing soil types, a deep sand (Moora) and a sand-over-clay shallow duplex soil (East
Beverley, EB). Lupin shoot and root dry matter and total plant N accumulation, proportional dependence on nitrogen fixation
and grain yield were greater at the deep sand site than the duplex soil site, although there was a similar proportion of shoot
N to estimated total BG N at both sites. The proportion of total plant BG N decreased from the vegetative stage (42–51%) to
peak biomass (25–39%) and maturity (23–34%). From 56–67% of BG N on the deep sand and 74–86% on the duplex soil was not recovered
in coarse roots (>2 mm) or as soluble N, but was present in the insoluble organic N fraction. There was evidence for cycling
of lupin root-derived N into soil microbial biomass and soluble organic N during lupin growth (by the late vegetative stage),
but no evidence for leaching of legume derived BG N during the lupin season. Estimates of fixed N input BG were at least four
times greater if based on total lupin BG N rather than on N recovered in coarse roots (>2 mm). There were no apparent losses
of lupin BG N during the summer fallow period subsequent to lupin harvest at either site. Also, immediately prior to sowing
of wheat there were similar proportions of lupin BG N in the inorganic (20–25%) and microbial biomass (6–9%) pools at both
sites, with the majority of BG N detected in the <2 mm fraction of the soil column. However, the proportion of residual lupin
BG N estimated to benefit the aboveground wheat biomass was relatively low, 10% on the deep sand and only 3% on the shallow
duplex. Some (14%) residual lupin BG N was leached as nitrate to 1 m on the deep sand compared to 8% of residual lupin BG
N leached to the clay layer (0.3 m) on the shallow duplex. About 27% of the residual lupin BG N on the deep sand at Moora
had apparently mineralised by the end of the succeeding wheat season (i.e. recovered either in the wheat shoots, as inorganic
N in the soil profile or as leached nitrate) compared to only 12% at EB. There was an unaccounted for large loss of residual
lupin BG N (50%) from the duplex soil at EB during the wheat season, postulated to be chiefly via denitrification. At both
sites after the wheat season a substantial proportion (32–55%) of legume derived BG N was still present as residual insoluble
organic N, considered to be an important contribution to structural and nutritional long-term sustainability of these soils. 相似文献
19.
Summary Growth and N accumulation were assessed in pure and mixed plantings (2 years old) of hybrid poplar and black alder in southern Québec. Symbiotic dinitrogen fixation was evaluated by natural15N dilution. Growth of hybrid poplar plants and N accumulation in their tissues increased with their decreasing contribution to species ratio whereas no differences among treatments were measured for black alder. Yield and N content per hectare of aboveground components increased with the proportion of black alder in the plantation. Symbiotic dinitrogen fixation was estimated at 68% of alder nitrogen in both pure and mixed treatments. The maximum rate of N-fixation was 53kg ha–1 yr–1 in pure alder plots. The amount of nitrogen accumulated in entire plants of black alder from symbiotic fixation could be sufficient to balance the N export in harvested stems and branches of short-rotation plantations containing at least 33% of alder. 相似文献
20.
Tobias Tamelander Janne E. Søreide Haakon Hop 《Journal of experimental marine biology and ecology》2006,333(2):231-240
Fractionation of δ13C and δ15N between food, consumer, and faecal pellets was studied in the Arctic marine copepod Calanus glacialis Jaschnov, fed with isotopically distinct algal monocultures. Temporal variations in δ13C and δ15N of copepods that were fed ice algae and phytoplankton followed those of a control group consisting of starved animals. There were no significant trends in the δ13C and δ15N values of copepods that were starved for 42 days, suggesting that the isotopic composition of non-lipid body tissues is unaffected by the metabolic processes during prolonged periods of starvation. The stable isotopic composition of starved copepods therefore seems to reflect food consumed during the previous period of feeding and growth. Faecal pellets produced by feeding copepods were depleted in 13C and 15N by 6.3-11.2‰ and 0.7-9.1‰, respectively, relative to the food ingested. These results indicate that faecal pellet production is an important pathway for the trophic fractionation of δ13C, whereas other fractionation pathways, such as excretion of ammonia, may be relatively more important for δ15N. The strong depletion of 13C in faecal pellets compared to the food suggests that grazing by herbivorous copepods on primary production adds to the variability of δ13C in marine particulate organic matter. 相似文献