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1.
The (C2 H4 + H2(C2 H2 ) )/15 N2 ratios of 15 clover- Rhizobium symbionts. soybean, and black medick symbionts were measured. Relative efficiency based on the C2H4 production and on 15 N2 incorporation were compared, and in most symbionts there was little difference between the two measures of relative efficiency. Total measurable electron flux through nitrogenase during acetylene reduction and 15 N2 incorporation were nearly equal for most symbionts studied. The relative efficiency and the (C2 H4 + H2(C2 H2 ) )/15 N2 ratio showed an inverse correlation. Use of this ratio appears preferable to use of the ratio of C2H2 reduction/N2 reduction. Some evolution of H2 was observed in the presence of C2 H2 . 相似文献
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Kees-Jan Van Groenigen Johan Six David Harris‡ Herbert Blum§ Chris Van Kessel 《Global Change Biology》2003,9(12):1751-1762
Reduced soil N availability under elevated CO2 may limit the plant's capacity to increase photosynthesis and thus the potential for increased soil C input. Plant productivity and soil C input should be less constrained by available soil N in an N2‐fixing system. We studied the effects of Trifolium repens (an N2‐fixing legume) and Lolium perenne on soil N and C sequestration in response to 9 years of elevated CO2 under FACE conditions. 15N‐labeled fertilizer was applied at a rate of 140 and 560 kg N ha?1 yr?1 and the CO2 concentration was increased to 60 Pa pCO2 using 13C‐depleted CO2. The total soil C content was unaffected by elevated CO2, species and rate of 15N fertilization. However, under elevated CO2, the total amount of newly sequestered soil C was significantly higher under T. repens than under L. perenne. The fraction of fertilizer‐N (fN) of the total soil N pool was significantly lower under T. repens than under L. perenne. The rate of N fertilization, but not elevated CO2, had a significant effect on fN values of the total soil N pool. The fractions of newly sequestered C (fC) differed strongly among intra‐aggregate soil organic matter fractions, but were unaffected by plant species and the rate of N fertilization. Under elevated CO2, the ratio of fertilizer‐N per unit of new C decreased under T. repens compared with L. perenne. The L. perenne system sequestered more 15N fertilizer than T. repens: 179 vs. 101 kg N ha?1 for the low rate of N fertilization and 393 vs. 319 kg N ha?1 for the high N‐fertilization rate. As the loss of fertilizer‐15N contributed to the 15N‐isotope dilution under T. repens, the input of fixed N into the soil could not be estimated. Although N2 fixation was an important source of N in the T. repens system, there was no significant increase in total soil C compared with a non‐N2‐fixing L. perenne system. This suggests that N2 fixation and the availability of N are not the main factors controlling soil C sequestration in a T. repens system. 相似文献
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Abstract A 16-channel fully automated microcomputer-based system was designed to measure the disappearance of NO?3 NO?2 and NH+4 simultaneously from uptake solutions. The analyses were done using high-performance liquid chromatography. Statistical procedures were used to generate transport kinetics and interactions amongst NO?3, NO?2 and NH+4 by intact wheat seedlings. The simultaneous analysis of NO?3, NO?2 and NH+4 at real-time; the accommodation of varying sampling intervals; the capability to study up to 16 experimental units in synchrony; and the analysis of the data with a microcomputer, make this a powerful system for studying transport kinetics and interactions. 相似文献
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Effects of elevated CO2 , temperature and N fertilization on nitrogen fluxes in a temperate grassland ecosystem 总被引:2,自引:0,他引:2
The soil nitrogen cycle was investigated in a pre‐established Lolium perenne sward on a loamy soil and exposed to ambient and elevated atmospheric CO2 concentrations (350 and 700 μL L?1) and, at elevated [CO2], to a 3 °C temperature increase. At two levels of mineral nitrogen supply, N– (150 kgN ha?1 y?1) and N+ (533 kgN ha?1 y?1), 15N‐labelled ammonium nitrate was supplied in split applications over a 2.5‐y period. The recovery of the labelled fertilizer N was measured in the harvests, in the stubble and roots, in the macro‐organic matter fractions above 200 μm in size (MOM) and in the aggregated organic matter below 200 μM (AOM). Elevated [CO2] reduced the total amount of N harvested in the clipped parts of the sward. The harvested N derived from soil was reduced to a greater extent than that derived from fertilizer. At both N supplies, elevated [CO2] modified the allocation of the fertilizer N in the sward, in favour of the stubble and roots and significantly increased the recovery of fertilizer N in the soil macro‐organic matter fractions. The increase of fertilizer N immobilization in the MOM was associated with a decline of fertilizer N uptake by the grass sward, which supported the hypothesis of a negative feedback of elevated [CO2] on the sward N yield and uptake. Similar and even more pronounced effects were observed for the native N mineralized in the soil. At N–, a greater part of the fertilizer N organized in the root phytomass resulted in an underestimation of N immobilized in dead roots and, in turn, an underestimation of N immobilization in the MOM. The 3 °C temperature increase alleviated the [CO2] effect throughout much of the N cycle, increasing soil N mineralization, N derived from soil in the harvests, and the partitioning of the assimilated fertilizer N to shoots. In conclusion, at ambient temperature, the N cycle was slowed down under elevated [CO2], which restricted the increase in the aboveground production of the grass sward, and apparently contributed to the sequestration of carbon belowground. In contrast, a temperature increase under elevated [CO2] stimulated the soil nitrogen cycle, improved the N nutrition of the sward and restricted the magnitude of the soil C sequestration. 相似文献
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Abstract The Het+ Nif+ and Het− Nif− strains of Nostoc muscorum sensitive to growth inhibition by methylamine (MA), overcame the MA inhibition as a result of their mutation to l -methionine- dl -sulfoximide (MSX)-resistant phenotype, which enabled them to assimilate MA like an ammonium nitrogen source. The MSX-resistant Het+ Nif+ strain synthesized the inhibitor-resistant transferase-defective glutamine synthetase (GS), which unlike parental GS underwent MA-dependent in vivo activation. These results suggest the involvement of GS enzyme in control of MA assimilation in cyanobacteria. 相似文献
8.
Leif Skøt 《Physiologia plantarum》1983,59(4):581-584
The quantitative relationship between C2 H2 reduction, H2 evolution and 15 N2 fixation was investigated in excised root nodules from pea plants ( Pisum sativum L. cv. Bodil) grown under controlled conditions. The C2 H2 /N2 conversion factor varied from 3.31 to 5.12 between the 32nd and the 67th day after planting. After correction for H2 evolution in air, the factor (C2 H2 -H2 )/N2 decreased to values near the theoretical value 3, or in one case to a value significantly ( P < 0.05) below 3. The proportion of the total electron flow through nitrogenase, which is not wasted in H2 production but used for N2 reduction, is often stated as the relative efficiency (1-H2 /C2 H2 ). This factor varied significantly ( P < 0.05) during the growth period. The actual allocation of electrons to H2 and N2 , expressed as the H2 /N2 ratio, was independent of plant age, however. This discrepancy and the observation that the (C2 H2 -H2 )/N2 conversion factor tended to be lower than 3, suggests that the C2 H2 reduction assay underestimates the total electron flow through nitrogenase. 相似文献
9.
In this study, the response of N2 fixation to elevated CO2 was measured in Scirpus olneyi, a C3 sedge, and Spartina patens, a C4 grass, using acetylene reduction assay and 15N2 gas feeding. Field plants grown in PVC tubes (25 cm long, 10 cm internal diameter) were used. Exposure to elevated CO2 significantly (P < 0·05) caused a 35% increase in nitrogenase activity and 73% increase in 15N incorporated by Scirpus olneyi. In Spartina patens, elevated CO2 (660 ± 1 μ mol mol − 1) increased nitrogenase activity and 15N incorporation by 13 and 23%, respectively. Estimates showed that the rate of N2 fixation in Scirpus olneyi under elevated CO2 was 611 ± 75 ng 15N fixed plant − 1 h − 1 compared with 367 ± 46 ng 15N fixed plant − 1 h − 1 in ambient CO2 plants. In Spartina patens, however, the rate of N2 fixation was 12·5 ± 1·1 versus 9·8 ± 1·3 ng 15N fixed plant − 1 h − 1 for elevated and ambient CO2, respectively. Heterotrophic non-symbiotic N2 fixation in plant-free marsh sediment also increased significantly (P < 0·05) with elevated CO2. The proportional increase in 15N2 fixation correlated with the relative stimulation of photosynthesis, in that N2 fixation was high in the C3 plant in which photosynthesis was also high, and lower in the C4 plant in which photosynthesis was relatively less stimulated by growth in elevated CO2. These results are consistent with the hypothesis that carbon fixation in C3 species, stimulated by rising CO2, is likely to provide additional carbon to endophytic and below-ground microbial processes. 相似文献
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Sanna Saarnio T.I.M.O. Saarinen † Harri Vasander‡ Jouko Silvola 《Global Change Biology》2000,6(2):137-144
Natural wetlands release about 20% of global emissions of CH4, an effective greenhouse gas contributing to the total radiative forcing. Thus, changes in the carbon cycle in wetlands could have significant impacts on climate. The effect of raised supply of CO2 or NH4NO3 on the annual CH4 efflux from the lawn of a boreal oligotrophic mire was investigated over two years. Ten study plots were enclosed with mini‐FACE rings, five vented with CO2‐enriched air and the other five with ambient air. In addition, five plots were sprayed with NH4NO3 so that the cumulative addition of N was 3 g m?2 y?1; and five plots were controls. The CO2 enrichment (target concentration 560 ppmv) increased CH4 efflux about 30–40%, but half of this increase seemed to be caused by the air‐blowing system. The increasing atmospheric concentration of CO2 would promote CH4 release in boreal mires, but the increase in CH4 efflux would be clearly smaller than that reported in studies made in temperate or subtropical temperature conditions. Addition of N enhanced the annual release of CH4 only slightly. At least over the short‐term, the increase in N deposition would have little effect on CH4 effluxes. The increase in CH4 release would probably increase radiative forcing and thus accelerate climate change. However, CH4 effluxes are only a small part in the whole matter balance in mires and thus further studies are needed to define the net effects of raised supply of CO2 or N for carbon accumulation, trace gas fluxes and radiative forcing. 相似文献
11.
Matthew B. Tobin Stephen C.J. Cole Steven Kovacevic James R. Miller Jack E. Baldwin John D. Sutherland 《FEMS microbiology letters》1994,121(1):39-46
Abstract Using a high level Escherichia coli expression system for the Penicillium chrysogenum penDE gene, we have produced acyl-coenzyme A: isopenicillin N acyltransferase (AT) enzymes containing amino acid substitutions at three conserved Ser residues. Chosen for study based on amino acid sequence homologies to other proteins, Ser227 , Ser230 and Ser309 were changed to Cys or Ala to assess amino acid side chain involvement in proenzyme cleavage and AT enzyme mechanism. Substitutions at Ser230 had no effect on proenzyme cleavage, acyl-coenzyme A: IPN acyltransferase (IAT) or acyl-coenzyme A: 6-aminopenicillanic acid acyltransferase (AAT) activities. While Ser227 →Cys had no effect, Ser227 →Ala produced uncleaved proenzyme lacking both AAT and IAT activities, suggesting that the presence of a nucleophilic side chain at this residue is required for proenzyme cleavage and AT activity. Substitution of Ser309 →Cys did not appreciably prevent proenzyme cleavage, IAT or AAT activity. Recombinant AT (recAT) proenzyme containing Ser309 →Ala was cleaved; however, IAT and AAT activities were not observed. This separation of proenzyme cleavage from IAT and AAT activities has not been previously observed, and suggests that Ser309 is involved in substrate acylation. 相似文献
12.
Shuijin Hu Jiansheng Wu Kent O. Burkey† Mary K. Firestone‡ 《Global Change Biology》2005,11(2):213-223
The impact of elevated CO2 on terrestrial ecosystem C balance, both in sign or magnitude, is not clear because the resulting alterations in C input, plant nutrient demand and water use efficiency often have contrasting impacts on microbial decomposition processes. One major source of uncertainty stems from the impact of elevated CO2 on N availability to plants and microbes. We examined the effects of atmospheric CO2 enrichment (ambient+370 μmol mol?1) on plant and microbial N acquisition in two different mesocosm experiments, using model plant species of annual grasses of Avena barbata and A. fatua, respectively. The A. barbata experiment was conducted in a N‐poor sandy loam and the A. fatua experiment was on a N‐rich clayey loam. Plant–microbial N partitioning was examined through determining the distribution of a 15N tracer. In the A. barbata experiment, 15N tracer was introduced to a field labeling experiment in the previous year so that 15N predominantly existed in nonextractable soil pools. In the A. fatua experiment, 15N was introduced in a mineral solution [(15NH4)2SO4 solution] during the growing season of A. fatua. Results of both N budget and 15N tracer analyses indicated that elevated CO2 increased plant N acquisition from the soil. In the A. barbata experiment, elevated CO2 increased plant biomass N by ca. 10% but there was no corresponding decrease in soil extractable N, suggesting that plants might have obtained N from the nonextractable organic N pool because of enhanced microbial activity. In the A. fatua experiment, however, the CO2‐led increase in plant biomass N was statistically equal to the reduction in soil extractable N. Although atmospheric CO2 enrichment enhanced microbial biomass C under A. barbata or microbial activity (respiration) under A. fatua, it had no significant effect on microbial biomass N in either experiment. Elevated CO2 increased the colonization of A. fatua roots by arbuscular mycorrhizal fungi, which coincided with the enhancement of plant competitiveness for soluble soil N. Together, these results suggest that elevated CO2 may tighten N cycling through facilitating plant N acquisition. However, it is unknown to what degree results from these short‐term microcosm experiments can be extrapolated to field conditions. Long‐term studies in less‐disturbed soils are needed to determine whether CO2‐enhancement of plant N acquisition can significantly relieve N limitation over plant growth in an elevated CO2 environment. 相似文献
13.
A method based on simultaneous short-term exposure to 14 CO2 and 15 N2 is described for studying nitrogen fixation and distribution in legumes relative to carbon assimilation and use. Equipment designed to accomodate experiments under natural conditions with very little disturbance of the N2 fixing association is used. It permits continuous measurement and regulation of variables such as air temperature, humidity and CO2 concentration as well as soil aeration. Measurements of distribution and use of assimilates, respiration of nodulated roots, quantitative N2 fixation and the distribution and fate of fixed N as a function of time lead to a precise estimation of C and N budgets for each labelling period. When experiments are done at several phenological stages they give a new insight into the complex C and N interrelations in legume symbiosis.
A series of trials throughout the growth period of Glycine max (L.) Merr. cv. Hodgson demonstrated the sensitivity of the method. The development of the plants from vegetative to reproductive stages was accompanied by a complete change in the distribution patterns of current assimilates and products of nitrogen fixation. Maximum sink strength moved from the leaves to the pods and seeds which ended up receiving 70% of the incoming C and 35% of the fixed N. The fact that up to 85% of fixed N in the plants was in the reproductive organs at maturity can be accounted for by remobilisation from vegetative parts.
The respiration of nodulated roots utilized 33% of carbon translocated to below-ground plant parts before nitrogen fixation started, but as much as 50% during the period of optimal fixation. The advantages and limitations of the isotopic method described are critically discussed as a prelude to future investigations. 相似文献
A series of trials throughout the growth period of Glycine max (L.) Merr. cv. Hodgson demonstrated the sensitivity of the method. The development of the plants from vegetative to reproductive stages was accompanied by a complete change in the distribution patterns of current assimilates and products of nitrogen fixation. Maximum sink strength moved from the leaves to the pods and seeds which ended up receiving 70% of the incoming C and 35% of the fixed N. The fact that up to 85% of fixed N in the plants was in the reproductive organs at maturity can be accounted for by remobilisation from vegetative parts.
The respiration of nodulated roots utilized 33% of carbon translocated to below-ground plant parts before nitrogen fixation started, but as much as 50% during the period of optimal fixation. The advantages and limitations of the isotopic method described are critically discussed as a prelude to future investigations. 相似文献
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Fu-Cang Zhang Shao-Zhong Kang Fu-Sheng Li Jian-Hua Zhang 《植物学报(英文版)》2007,49(4):455-462
In the present study, we investigated whether growth and main nutrient ion concentrations of cabbage (Brassica campestris L.) could be increased when plants were subjected to different NH4^+/NO3- ratios. Cabbage seedlings were grown in a greenhouse in nutrient solutions with five NH4^+/NO3- ratios (1:0; 0.75:0.25; 0.5:0.5; 0.25:0.75; and 0:1). The results showed that cabbage growth was reduced by 87% when the proportion of NH4^+-N in the nutrient solution was more than 75% compared with a ratio NH4^+/NO3- of 0.5:0.5 35 d after transplanting, suggesting a possible toxicity due to the accumulation of a large amount of free ammonia in the leaves. When the NH4+/NO3- ratio was 0.5:0.5, fresh seedling weight, root length, and H2PO4- (P), K^+, Ca^2+, and Mg^2+ concentrations were all higher than those in plants grown under other NH4^+/NO3- ratios. The nitrate concentration in the leaves was the lowest in plants grown at 0.5: 0.5 NH4^+/NO3-. The present results indicate that an appropriate NH4^+/NO3- ratio improves the absorption of other nutrients and maintains a suitable proportion of N assimilation and storage that should benefit plant growth and the quality of cabbage as a vegetable. 相似文献
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A. P. Simoes P. C. Oliveira A. M. Sebastião J. A. Ribeiro 《Journal of neurochemistry》1988,50(3):899-903
The effect of the stable adenosine analogue, N6-cyclohexyladenosine, on 22Na uptake by rat brain synaptosomes stimulated by veratridine was investigated. In the presence of N6-cyclohexyladenosine, both the initial rate and the maximum sodium uptake were decreased. The inhibitory effect of N6-cyclohexyladenosine on sodium uptake by synaptosomes after 5 s of incubation with 22Na was concentration-dependent, antagonized by 1,3-dipropyl-8-p-sulfophenylxanthine, and attenuated by increasing the concentration of veratridine. The possibility that the adenosine analogue, by activating a xanthine-sensitive adenosine receptor, can operate inhibition of the voltage-dependent sodium channels is discussed. 相似文献
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Frank Hagedorn Stefan Maurer† Jürg B. Bucher Rolf T.W. Siegwolf† 《Global Change Biology》2005,11(10):1816-1827
The fate of immobilized N in soils is one of the great uncertainties in predicting C sequestration at increased CO2 and N deposition. In a dual isotope tracer experiment (13C, 15N) within a 4‐year CO2 enrichment (+200 ppmv) study with forest model ecosystems, we (i) quantified the effects of elevated CO2 on the partitioning of N; (ii) traced immobilized N into physically separated pools of soil organic matter (SOM) with turnover rates known from their 13C signals; and (iii) estimated the remobilization and thus, the bio‐availability of newly sequestered C and N. (1) CO2 enrichment significantly decreased NO3? concentrations in soil waters and export from 1.5 m deep lysimeters by 30–80%. Consequently, elevated CO2 increased the overall retention of N in the model ecosystems. (2) About 60–80% of added 15NH415NO3 were retained in soils. The clay fraction was the greatest sink for the immobilized 15N sequestering 50–60% of the total new soil N. SOM associated with clay contained only 25% of the total new soil C pool and had small C/N ratios (<13), indicating that it consists of humified organic matter with a relatively slow turn over rate. This implies that added 15N was mainly immobilized in stable mineral‐bound SOM pools. (3) Incubation of soils for 1 year showed that the remobilization of newly sequestered N was three to nine times smaller than that of newly sequestered C. Thus, inorganic inputs of N were stabilized more effectively in soils than C. Significantly less newly sequestered N was remobilized from soils previously exposed to elevated CO2. In summary, our results show firstly that a large fraction of inorganic N inputs becomes effectively immobilized in relative stable SOM pools and secondly that elevated CO2 can increase N retention in soils and hence it may tighten N cycling and diminish the risk of nitrate leaching to groundwater. 相似文献
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J. S. Pate M. J. Unkovich P. D. Erskine & G. R. Stewart 《Plant, cell & environment》1998,21(12):1231-1242
Samples of recently produced shoot material collected in winter/spring from common plant species of mulga vegetation in eastern and Western Australia were assayed for 13C and 15N natural abundance. 13C analyses showed only three of the 88 test species to exhibit C4 metabolism and only one of seven succulent species to be in CAM mode. Non-succulent winter ephemeral C3 species showed significantly lower mean δ13C values (– 28·0‰) than corresponding C3-type herbaceous perennials, woody shrubs or trees (– 26·9, – 25·7 and – 26·2‰, respectively), suggesting lower water stress and poorer water use efficiency in carbon acquisition by the former than latter groups of taxa. Corresponding values for δ15N of the above growth and life forms lay within the range 7·5–15·5‰. δ15N of soil NH4+ (mean 19·6‰) at a soft mulga site in Western Australia was considerably higher than that of NO3– (4·3‰). Shoot dry matter of Acacia spp. exhibited mean δ15N values (9·10 ± 0·6‰) identical to those of 37 companion non-N2-fixing woody shrubs and trees (9·06 ± 0·5‰). These data, with no evidence of nodulation, suggested little or no input of fixed N2 by the legumes in question. However, two acacias and two papilionoid legumes from a dune of wind-blown, heavily leached sand bordering a lake in mulga in Western Australia recorded δ15N values in the range 2·0–3·0‰ versus 6·4–10·7‰ for associated non-N2-fixing taxa. These differences in δ15N, and prolific nodulation of the legumes, indicated symbiotic inputs of fixed N in this unusual situation. δ15N signals of lichens, termites, ants and grasshoppers from mulga of Western Australia provided evidence of N2 fixation in certain termite colonies and by a cyanobacteria-containing species of lichen. Data are discussed in relation to earlier evidence of nitrophily and water availability constraints on nitrate utilization by mulga vegetation. 相似文献
18.
Vincent Allard Paul C. D. Newton Mark Lieffering Harry Clark Cory Matthew† Jean-François Soussana‡ Yvonne S. Gray 《Global Change Biology》2003,9(12):1731-1742
In pastures grazed by large herbivores, nutrients cycle both through litter and animal excreta. We compared nitrogen (N) returns from sheep grazing a temperate pasture exposed to ambient or elevated CO2 (475 μmol mol?1) in a FACE (Free Air CO2 Enrichment) experiment established in the spring of 1997. In the spring of 2000 and 2001, we measured the chemical composition of the diet, sheep faeces and of individual plant species before grazing to characterize feed intake and to compare the intake of N to the N produced in faeces. In both years under elevated CO2, leaves of the individual species exhibited lower N concentrations and higher water‐soluble carbohydrate (WSC) concentrations. There was a significantly greater proportion of legume in the diet at elevated CO2 but, together with the changes in chemical composition of individual species, this resulted in diets that had similar N but higher WSC and digestibility for both ambient and elevated CO2. We found that a greater proportion of dietary N was partitioned to urine at elevated CO2, probably because of the higher proportion of legume N in the diet, with possible differences in protein quality. A potentially significant consequence of this change in partitioning is greater N loss through volatilization at higher CO2 levels. 相似文献
19.
Delayed NH3 and N2 O uptake by maize leaves 总被引:1,自引:1,他引:0
20.
We assessed the effects of doubling atmospheric CO2 concentration, [CO2], on C and N allocation within pedunculate oak plants (Quercus robur L.) grown in containers under optimal water supply. A short-term dual 13CO2 and 15NO3? labelling experiment was carried out when the plants had formed their third growing flush. The 22-week exposure to 700 μl l?1 [CO2] stimulated plant growth and biomass accumulation (+53% as compared with the 350 μl l?1 [CO2] treatment) but decreased the root/shoot biomass ratio (-23%) and specific leaf area (-18%). Moreover, there was an increase in net CO2 assimilation rate (+37% on a leaf dry weight basis; +71% on a leaf area basis), and a decrease in both above- and below-ground CO2 respiration rates (-32 and -26%, respectively, on a dry mass basis) under elevated [CO2]. 13C acquisition, expressed on a plant mass basis or on a plant leaf area basis, was also markedly stimulated under elevated [CO2] both after the 12-h 13CO2 pulse phase and after the 60-h chase phase. Plant N content was increased under elevated CO2 (+36%), but not enough to compensate for the increase in plant C content (+53%). Thus, the plant C/N ratio was increased (+13%) and plant N concentration was decreased (-11%). There was no effect of elevated [CO2] on fine root-specific 15N uptake (amount of recently assimilated 15N per unit fine root dry mass), suggesting that modifications of plant N pools were merely linked to root size and not to root function. N concentration was decreased in the leaves of the first and second growing flushes and in the coarse roots, whereas it was unaffected by [CO2] in the stem and in the actively growing organs (fine roots and leaves of the third growth flush). Furthermore, leaf N content per unit area was unaffected by [CO2]. These results are consistent with the short-term optimization of N distribution within the plants with respect to growth and photosynthesis. Such an optimization might be achieved at the expense of the N pools in storage compartments (coarse roots, leaves of the first and second growth flushes). After the 60-h 13C chase phase, leaves of the first and second growth flushes were almost completely depleted in recent 13C under ambient [CO2], whereas these leaves retained important amounts of recently assimilated 13C (carbohydrate reserves?) under elevated [CO2]. 相似文献