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1.
The effect of rhizosphere dissolved inorganic carbon on gas exchange characteristics and growth rates of tomato seedlings 总被引:2,自引:0,他引:2
The possibility that an enhanced supply of dissolved inorganic carbon
(DIC=CO2+HCO3-) to the root solution could increase
the growth of Lycopersicon esculentum (L.) Mill. cv.
F144 was investigated under both saline and non-saline root medium
conditions. Tomato seedlings were grown in hydroponic culture with and
without NaCl and the root solution was aerated with CO2 concentrations in
the range between 0 and 5000 mol
mol-1. The biomass of both control and
salinity-stressed plants grown at high temperatures (daily maximum of
37C) and an irradiance of 1500 mol m-2
s-1 was increased by up to 200% by enriched
rhizosphere DIC. The growth rates of plants grown with irradiances of less
than 100 mol m-2 s-1
were increased by elevated rhizosphere DIC concentrations only when grown
at high shoot temperatures (35C) or with
salinity 28°C). At high light intensities, the photosynthetic rate,
the CO2 and light-saturated photosynthetic rate (jmax)
and the stomatal conductance of plants grown at high light intensity were
lower in plants supplied with enriched compared to ambient DIC. This was
interpreted as 'down-regulation' of the photosynthetic system in plants
supplied with elevated DIC. Labelled organic carbon in the xylem sap
derived from root DI14C incorporation was found to
be sufficient to deliver carbon to the shoot at rates equivalent to 1% and
10% of the photosynthetic rate of the plants supplied with ambient- and
enriched-DIC, respectively. It was concluded that organic carbon derived
from DIC incorporation and translocated in the xylem from the root to the
shoot may provide a source of carbon for the shoots, especially under
conditions where low stomatal conductance may be advantageous, such as
salinity stress, high shoot temperatures and high light
intensities. 相似文献
2.
Background
Archaea are important to the carbon and nitrogen cycles, but it remains uncertain how rising atmospheric carbon dioxide concentrations ([CO2]) will influence the structure and function of soil archaeal communities.Methodology/Principal Findings
We measured abundances of archaeal and bacterial 16S rRNA and amoA genes, phylogenies of archaeal 16S rRNA and amoA genes, concentrations of KCl-extractable soil ammonium and nitrite, and potential ammonia oxidation rates in rhizosphere soil samples from maize and soybean exposed to ambient (∼385 ppm) and elevated (550 ppm) [CO2] in a replicated and field-based study. There was no influence of elevated [CO2] on copy numbers of archaeal or bacterial 16S rRNA or amoA genes, archaeal community composition, KCl-extractable soil ammonium or nitrite, or potential ammonia oxidation rates for samples from maize, a model C4 plant. Phylogenetic evidence indicated decreased relative abundance of crenarchaeal sequences in the rhizosphere of soybean, a model leguminous-C3 plant, at elevated [CO2], whereas quantitative PCR data indicated no changes in the absolute abundance of archaea. There were no changes in potential ammonia oxidation rates at elevated [CO2] for soybean. Ammonia oxidation rates were lower in the rhizosphere of maize than soybean, likely because of lower soil pH and/or abundance of archaea. KCl-extractable ammonium and nitrite concentrations were lower at elevated than ambient [CO2] for soybean.Conclusion
Plant-driven shifts in soil biogeochemical processes in response to elevated [CO2] affected archaeal community composition, but not copy numbers of archaeal genes, in the rhizosphere of soybean. The lack of a treatment effect for maize is consistent with the fact that the photosynthesis and productivity of maize are not stimulated by elevated [CO2] in the absence of drought. 相似文献3.
4.
5.
Elevated CO2 reduces O3 flux and O3-induced yield losses in soybeans: possible implications for elevated CO2 studies 总被引:2,自引:0,他引:2
Soybeans were grown for three seasons in open-top field chambersto determine (1) whether elevated CO2 (360 versus 700 µmolmol1) alleviates some of the yield loss due to pollutantO3, (2) whether the partial stomatal closure resulting fromchronic O3 exposure (charcoal-filtered air versus 1.5 ambientconcentrations) is a cause or result of decreased photosynthesis,and (3) possible implications of CO2/O3 interactions to climatechange studies using elevated CO2. Leaf conductance was reducedby elevated CO2, regardless of O3 level, or by exposure to O3alone. As.a result of these effects on conductance, high CO2reduced estimated midday O3 flux into the leaf by an averageof 50% in charcoal-filtered air and 35% in the high O3 treatment.However, while exposure to O3 reduced seed yields by 41% atambient CO2 levels, the yield reduction was completely amelioratedby elevated CO2. The threshold midday O3 flux for yield lossappears to be 2030 nmol m2 s1 in this study.Although elevated CO2 increased total biomass production, itdid not increase seed yields. A/Ci curves show a large reductionin the stomatal limitation to photosynthesis due to elevatedCO2 but no effect of O3. These data demonstrate that (1) reducedconductance due to O3 is the result, and not the cause, of reducedphotosynthesis, (2) 700 µmol mol1 CO2 can completelyameliorate yield losses due to O3 within the limits of theseexperiments, and (3) some reports of increased yields underelevated CO2 treatments may, at least in part, reflect the ameliorationof unrecognized suppression of yield by O3 or other stresses. Key words: Stomatal limitation, elevated CO2, O3 flux, Glycine max, yield suppression 相似文献
6.
Time-course of uptake of dissolved inorganic carbon through willow roots in light and in darkness 总被引:1,自引:0,他引:1
Uptake of dissolved inorganic carbon (DIC) from a nutrient solution by willow roots was measured in light and darkness and the distribution in the plant of DIC taken up by the roots was determined. It was also studied whether the transport system could be activated by preincubation with dissolved inorganic carbon.
Willow plants ( Salix cv. Aquatica gigantea) grown in hydroponic culture media were preincubated for 2 days with or without 0.74 mM NaHCO3 . After preincubation, either unlabelled or [14 C]-labelled NaHCO3 was injected into the media and after 1, 5, 10 and 24 h either in light or in darkness the plants were harvested in pieces into liquid nitrogen, lyophilized and burned in a combustion chamber.
14 C was transported through the roots to the shoots and leaves both in light and in darkness, although incorporation of 14 C in darkness was only half of that in light at the end of the 24-h feeding period. Both in light and in darkness the amount of 14 C increased in all parts of willow plants with time. In light the rate of labelling was highest into cuttings and shoots. In darkness more than half of the total label was detected in cuttings of both the non-activated and the activated treatments.
In the shoots the middle part was most strongly labelled after 5 and 10 h, but after 24 h14 C moved towards the base of the shoot. In the leaves at all feeding times most radioactivity was incorporated into the young, fully open leaves on the upper part of the shoots. Preincubation of plants with unlabelled NaHCO3 in growth media had no clear effect on the rate of DIC uptake either in light or in darkness. 相似文献
Willow plants ( Salix cv. Aquatica gigantea) grown in hydroponic culture media were preincubated for 2 days with or without 0.74 mM NaHCO
In the shoots the middle part was most strongly labelled after 5 and 10 h, but after 24 h
7.
Chloroplasts with high rates of photosynthetic O2 evolution (up to 120 mol O2· (mg Chl)-1·h-1 compared with 130 mol O2· (mg Chl)-1·h-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO2 concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O2 uptake could be observed in the dark by high- and low-CO2 adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m-2·s-1 for high- and low-CO2 adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO2 adapted chloroplasts, whereas high-CO2 adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O2 evolution (Km(DIC)) was 31.1 and 156 M DIC for low- and high-CO2 adapted chloroplasts, respectively. These results demonstrate that the CO2 concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl
chlorophyll
- DIC
dissolved inorganic carbon
- Km(DIC)
coneentration of dissolved inorganic carbon required for the rate of half maximal net O2 evolution
- PFR
photon fluence rate
- SPGM
silicasol-PVP-gradient medium 相似文献
8.
Soil carbon dioxide partial pressure and dissolved inorganic carbonate chemistry under elevated carbon dioxide and ozone 总被引:1,自引:0,他引:1
Global emissions of atmospheric CO2 and tropospheric O3 are rising and expected to impact large areas of the Earths forests. While CO2 stimulates net primary production, O3 reduces photosynthesis, altering plant C allocation and reducing ecosystem C storage. The effects of multiple air pollutants can alter belowground C allocation, leading to changes in the partial pressure of CO2 (pCO2) in the soil , chemistry of dissolved inorganic carbonate (DIC) and the rate of mineral weathering. As this system represents a linkage between the long- and short-term C cycles and sequestration of atmospheric CO2, changes in atmospheric chemistry that affect net primary production may alter the fate of C in these ecosystems. To date, little is known about the combined effects of elevated CO2 and O3 on the inorganic C cycle in forest systems. Free air CO2 and O3 enrichment (FACE) technology was used at the Aspen FACE project in Rhinelander, Wisconsin to understand how elevated atmospheric CO2 and O3 interact to alter pCO2 and DIC concentrations in the soil. Ambient and elevated CO2 levels were 360±16 and 542±81 l l–1, respectively; ambient and elevated O3 levels were 33±14 and 49±24 nl l–1, respectively. Measured concentrations of soil CO2 and calculated concentrations of DIC increased over the growing season by 14 and 22%, respectively, under elevated atmospheric CO2 and were unaffected by elevated tropospheric O3. The increased concentration of DIC altered inorganic carbonate chemistry by increasing system total alkalinity by 210%, likely due to enhanced chemical weathering. The study also demonstrated the close coupling between the seasonal 13C of soil pCO2 and DIC, as a mixing model showed that new atmospheric CO2 accounted for approximately 90% of the C leaving the system as DIC. This study illustrates the potential of using stable isotopic techniques and FACE technology to examine long- and short-term ecosystem C sequestration. 相似文献
9.
The influence of elevated CO2 and O3 concentrations on Scots pine needles: changes in starch and secondary metabolites over three exposure years 总被引:1,自引:0,他引:1
Scots pine (Pinus sylvestris L.) trees, aged about 20 years old, growing on a natural pine heath were exposed to two concentrations of CO2 (ambient CO2 and double-ambient CO2) and two O3 regimes (ambient O3 and double-ambient O3) and their combination in open-top chambers during growing seasons 1994, 1995 and 1996. Concentrations of foliar starch and
secondary compounds are reported in this paper. Starch concentrations remained unaffected by elevated CO2 and/or O3 concentrations during the first 2 study years. But in the autumn of the last study year, a significantly higher concentration
of starch was found in current-year needles of trees exposed to elevated CO2 compared with ambient air. There were large differences in concentrations of starch and secondary compounds between individual
trees. Elevated concentrations of CO2 and/or O3 did not have any significant effects on the concentrations of foliar total monoterpenes, total resin acids or total phenolics.
Significantly higher concentrations of monoterpenes and resin acids and mostly lower concentrations of starch were found in
trees growing without chambers than in those growing in open-top chambers, while there were no differences in concentrations
of total phenolics between trees growing without or in chambers. The results suggest that elevated concentrations of CO2 might increase foliar starch concentrations in Scots pine, while secondary metabolites remain unaffected. Realistically elevated
O3 concentrations do not have clear effects on carbon allocation to starch and secondary compounds even after 3 exposure years.
Received: 2 June 1997 / Accepted: 12 December 1997 相似文献
10.
Effect of elevated dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum on D-glucose and L-lactate 总被引:1,自引:0,他引:1
Bäumchen C Knoll A Husemann B Seletzky J Maier B Dietrich C Amoabediny G Büchs J 《Journal of biotechnology》2007,128(4):868-874
The effect of increased dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum was studied with continuous turbidostatic cultures. The carbon sources were either l-lactate or d-glucose. To increase the dissolved carbon dioxide concentration the carbon dioxide partial pressure of the inlet gas stream pCO2,IN was increased stepwise from 0.0003 bar (air) up to 0.79 bar, while the oxygen partial pressure of the inlet gas stream was kept constant at 0.21 bar. For each resulting carbon dioxide partial pressure pCO2 the maximum specific growth rate mu(max) was determined from the feed rate resulting from the turbidostatic control. On d-glucose and pCO2 up to 0.26 bar, mu(max) was mostly constant around 0.58 h(-1). Higher pCO2 led to a slight decrease of mu(max). On l-lactate mu(max) increased gradually with increasing carbon dioxide partial pressures from 0.37 h(-1) under aeration with air to a maximum value of 0.47 h(-1) at a pCO2 of 0.26 bar. At very high pCO2 (0.81 bar) mu(max) decreased down to 0.35 h(-1) independent of the carbon source. 相似文献
11.
Influence of elevated CO2 and nitrogen nutrition on rice plant growth,soil microbial biomass,dissolved organic carbon and dissolved CH4 总被引:1,自引:0,他引:1
Rice (Oryza sativa) was grown in six sunlit, semi-closed growth chambers for two seasons at 350 L L–1 (ambient) and 650 L L–1 (elevated) CO2 and different levels of nitrogen (N) supplement. The objective of this research was to study the influence of CO2 enrichment and N nutrition on rice plant growth, soil microbial biomass, dissolved organic carbon (DOC) and dissolved CH4. Elevated CO2 concentration ([CO2]) demonstrated a wide range of enhancement to both above- and below-ground plant biomass, in particular to stems and roots (for roots when N was not limiting) in the mid-season (80 days after transplanting) and stems/ears at the final harvest, depending on season and the level of N supplement. Elevated [CO2] significantly increased microbial biomass carbon in the surface 5 cm soil when N (90 kg ha–1) was in sufficient supply. Low N supplement (30 kg ha–1) limited the enhancement of root growth by elevated [CO2], leading consequently to diminished response of soil microbial biomass carbon to CO2 enrichment. The concentration of dissolved CH4 (as well as soil DOC, but to a lesser degree) was observed to be positively related to elevated [CO2], especially at high rate of N application (120 kg ha–1) or at 10 cm depth (versus 5 cm depth) in the later half of the growing season (at 80 kg N ha–1). Root senescence in the late season complicated the assessment of the effect of elevated [CO2] on root growth and soil organic carbon turnover and thus caution should be taken when interpreting respective high CO2 results. 相似文献
12.
13.
Soil and ecosystem trace gas fluxes are commonly measured using the dynamic chamber technique. Although the chamber pressure anomalies associated with this method are known to be a source of error, their effects have not been fully characterized. In this study, we use results from soil gas-exchange experiments and a soil CO2 transport model to characterize the effects of chamber pressure on soil CO2 efflux in an annual California grassland. For greater than ambient chamber pressures, experimental data show that soil-surface CO2 flux decreases as a nonlinear function of increasing chamber pressure; this decrease is larger for drier soils. In dry soil, a gauge pressure of 0.5 Pa reduced the measured soil CO2 efflux by roughly 70% relative to the control measurement at ambient pressure. Results from the soil CO2 transport model show that pressurizing the flux chamber above ambient pressure effectively flushes CO2 from the soil by generating a downward flow of air through the soil air-filled pore space. This advective flow of air reduces the CO2 concentration gradient across the soil–atmosphere interface, resulting in a smaller diffusive flux into the chamber head space. Simulations also show that the reduction in diffusive flux is a function of chamber pressure, soil moisture, soil texture, the depth distribution of soil CO2 generation, and chamber diameter. These results highlight the need for caution in the interpretation of dynamic chamber trace gas flux measurements. A portion of the frequently observed increase in net ecosystem carbon uptake under elevated CO2 may be an artifact resulting from the impact of chamber pressurization on soil CO2 efflux. 相似文献
14.
Yolima Carrillo Feike A. Dijkstra Elise Pendall Dan LeCain Colin Tucker 《Biogeochemistry》2014,117(2-3):229-240
Microbial decomposer C metabolism is considered a factor controlling soil C stability, a key regulator of global climate. The plant rhizosphere is now recognized as a crucial driver of soil C dynamics but specific mechanisms by which it can affect C processing are unclear. Climate change could affect microbial C metabolism via impacts on the plant rhizosphere. Using continuous 13C labelling under controlled conditions that allowed us to quantify SOM derived-C in all pools and fluxes, we evaluated the microbial metabolism of soil C in the rhizosphere of a C4 native grass exposed to elevated CO2 and under variation in N concentrations in soil and in plant root C:N stoichiometry. Our results demonstrated that this plant can influence soil C metabolism and further, that elevated CO2 conditions can alter this role by increasing microbial C efficiency as indicated by a reduction in soil-derived C respiration per unit of soil C-derived microbial biomass. Moreover, under elevated CO2 increases in soil N, and notably, root tissue N concentration increased C efficiency, suggesting elevated CO2 shifted the stoichiometric balance so N availability was a more critical factor regulating efficiency than under ambient conditions. The root C:N stoichiometry effect indicates that plant chemical traits such as root N concentration are able to influence the metabolism of soil C and that elevated CO2 conditions can modulate this role. Increased efficiency in soil C use was associated with negative rhizosphere priming and we hypothesize that the widely observed phenomenon of rhizosphere priming may result, at least in part, from changes in the metabolic efficiency of microbial populations. Observed changes in the microbial community support that shifting microbial populations were a contributing factor to the observed metabolic responses. Our case study points at greater efficiency of the SOM-degrading populations in a high CO2, high N world, potentially leading to greater C storage of microbially assimilated C in soil. 相似文献
15.
Dr. Jayne E. Ellis Peter S. Mcintyre Mohammed Saleh Alan G. Williams David Lloyd 《Current microbiology》1991,23(5):245-251
The effects of ruminal concentrations of CO2 and O2 on glucose-stimulated and endogenous fermentation of the rumen ciliateEudiplodinium maggii were investigated. The principal metabolic products were butyrate, acetate, lactate, propionate, H2, and CO2.13C NMR spectroscopy revealed glycerol to be an important, but previously unidentified, fermentation product of this organism. Glucose uptake and metabolite formation rates were influenced by the headspace composition during protozoal incubations. Glucose uptake was most rapid in the presence of low O2 in N2 (1–3 µM O2 dissolved in the protozoal suspension). Pathways located in the hydrogenosomes were O2 sensitive, and low O2 concentrations resulted in lowered acetate, H2, and CO2 formation. The presence of high CO2 (65% gaseous headspace by volume) resulted in elevated acetate and butyrate formation; fumarate and propionate were similarly found to accumulate at higher concentration than previously detected in the supernatants. Results suggest that under conditions similar to those prevailing in the rumen (i.e., high CO2),Eu. maggii produces higher levels of important ruminal volatile fatty acids, and thus its relative contribution to rumen metabolism may have been underestimated. 相似文献
16.
Martin H. Spalding 《Photosynthesis research》1990,24(3):245-252
The effect of photon flux density on inorganic carbon accumulation and photosynthetic CO2 assimilation was determined by CO2 exchange studies at three, limiting CO2 concentrations with a ca-1 mutant of Chlamydomonas reinhardiii. This mutant accumulates a large internal inorganic carbon pool in the light which apparently is unavailable for photosynthetic assimilation. Although steady-state photosynthetic CO2 assimilation did not respond to the varying photon flux densities because of CO2 limitation, components of inorganic-carbon accumulation were not clearly light saturated even at 1100 mol photons m-2 s-1, indicating a substantial energy requirement for inorganic carbon transport and accumulation. Steady-state photosynthetic CO2 assimilation responded to external CO2 concentrations but not to changing internal inorganic carbon concentrations, confirming that diffusion of CO2 into the cells supplies most of the CO2 for photosynthetic assimilation and that the internal inorganic carbon pool is essentially unavailable for photosynthetic assimilation. The estimated concentration of the internal inorganic carbon pool was found to be relatively insensitive to the external CO2 concentration over the small range tested, as would be expected if the concentration of this pool is limited by the internal to external inorganic carbon gradient. An attempt to use this CO2 exchange method to determine whether inorganic carbon accumulation and photosynthetic CO2 assimilation compete for energy at low photon flux densities proved inconclusive. 相似文献
17.
Long-term exposure of native vegetation to elevated atmospheric CO2 concentrations is expected to increase C inputs to the soil and, in ecosystems with seasonally dry periods, to increase soil
moisture. We tested the hypothesis that these indirect effects of elevated CO2 (600 μl l−1 vs 350 μl l−1) would improve conditions for microbial activity and stimulate emissions of nitrous oxide (N2O), a very potent and long-lived greenhouse gas. After two growing seasons, the mean N2O efflux from monoliths of calcareous grassland maintained at elevated CO2 was twice as high as that measured from monoliths maintained at current ambient CO2 (70 ± 9 vs 37 ± 4 μg N2O m−2 h−1 in October, 27 ± 5 vs 13 ± 3 μg N2O m−2 h−1 in November after aboveground harvest). The higher N2O emission rates at elevated CO2 were associated with increases in soil moisture, soil heterotrophic respiration, and plant biomass production, but appear
to be mainly attributable to higher soil moisture. Our results suggest that rising atmospheric CO2 may contribute more to the total greenhouse effect than is currently estimated because of its plant-mediated effects on soil
processes which may ultimately lead to increased N2O emissions from native grasslands.
Received: 11 September 1997 / Accepted: 20 March 1998 相似文献
18.
Mechanisms underlying the amelioration of O3-induced damage by elevated atmospheric concentrations of CO2 总被引:3,自引:0,他引:3
Cardoso-Vilhena J Balaguer L Eamus D Ollerenshaw J Barnes J 《Journal of experimental botany》2004,55(397):771-781
There is growing evidence that rising atmospheric CO2 concentrations will reduce or prevent reductions in the growth and productivity of C3 crops attributable to ozone (O3) pollution. In this study, the role of pollutant exclusion in mediating this response was investigated through growth chamber-based investigations on leaves 4 and 7 of spring wheat (Triticum aestivum cv. Hanno). In the core experiments, plants were raised at two atmospheric CO2 concentrations (ambient [350 micro l l(-1)] or elevated CO2 [700 micro l l(-1)] under two O3 regimes (charcoal/Purafil-filtered air [<5 nl l(-1) O3] or ozone-enriched air [75 nl l(-1) 7 h d(-1)]). A subsequent experiment used an additional O3 treatment where the goal was to achieve equivalent daily O3 uptake over the life-span of leaves 4 and 7 under ambient and CO2-enriched conditions, through daily adjustment of exposures based on measured shifts in stomatal conductance. Plant growth and net CO2 assimilation were stimulated by CO2-enrichment and reduced by exposure to O3. However, the impacts of O3 decreased with plant age (i.e. leaf 7 was more resistant to O3 injury than leaf 4); a finding consistent with ontogenic shifts in the tolerance of plant tissue and/or acclimation to O3-induced oxidative stress. In the combined treatment, elevated CO2 protected against the adverse effects of O3 and reduced cumulative O3 uptake (calculated from measurements of stomatal conductance) by c. 10% and 35% over the life-span of leaves 4 and 7, respectively. Analysis of the relationship between O3 uptake and the decline in the maximum in vivo rate of Rubisco carboxylation (Vcmax) revealed the protection afforded by CO2-enrichment to be due, to a large extent, to the exclusion of the pollutant from the leaf interior (as a consequence of the decline in stomatal conductance triggered by CO2-enrichment), but there was evidence (especially from flux-response relationships constructed for leaf 4) that CO2-enrichment resulted in additional effects that alleviated the impacts of ozone-induced oxidative stress on photosynthesis. 相似文献
19.
Our previous work indicated that salinity caused a shift in the predominant site of nitrate reduction and assimilation from the shoot to the root in tomato plants. In the present work we tested whether an enhanced supply of dissolved inorganic carbon (DIC, CO2+ HCO3) to the root solution could increase anaplerotic provision of carbon compounds for the increased nitrogen assimilation in the root of salinity-stressed Lycopersicon esculentum (L.) Mill. cv. F144. The seedlings were grown in hydroponic culture with 0 or 100mM NaCl and aeration of the root solution with either ambient or CO2-enriched air (5000 μmol mol?1). The salinity-treated plants accumulated more dry weight and higher total N when the roots were supplied with CO2-enriched aeration than when aerated with ambient air. Plants grown with salinity and enriched DIC also had higher rates of NO?3 uptake and translocated more NO?3 and reduced N in the xylem sap than did equivalent plants grown with ambient DIC. Incorporation of DIC was measured by supplying a 1 -h pulse of H14CO?3 to the roots followed by extraction with 80% ethanol. Enriched DIC increased root incorporation of DIC 10-fold in both salinized and non-salinized plants. In salinity-stressed plants, the products of dissolved inorganic 14C were preferentially diverted into amino acid synthesis to a greater extent than in non-salinized plants in which label was accumulated in organic acids. It was concluded that enriched DIC can increase the supply of N and anaplerotic carbon for amino acid synthesis in roots of salinized plants. Thus enriched DIC could relieve the limitation of carbon supply for ammonium assimilation and thus ameliorate the influence of salinity on NO?3 uptake and assimilation as well as on plant growth. 相似文献
20.
The biodegradability of aerial material from a C4 plant, sorghum grown under ambient (345 µmol mol–1) and elevated (700 µmol mol–1) atmospheric CO2 concentrations were compared by measuring soil respiratory activity. Initial daily respiratory activity (measured over 10 h per day) increased four fold from 110 to 440 cm3 CO2 100g dry weight soil–1 in soils amended with sorghum grown under either elevated or ambient CO2. Although soil respiratory activity decreased over the following 30 days, respiration remained significantly higher (t-test;p>0.05) in soils amended with sorghum grown under elevated CO2 concentrations. Analysis of the plant material revealed no significant differences in C:N ratios between sorghum grown under elevated or ambient CO2. The reason for the differences in soil respiratory activity have yet to be elucidated. However if this trend is repeated in natural ecosystems, this may have important implications for C and N cycling. 相似文献