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1.
We assessed the effect of growth at either 400 μmol mol?1 (ambient) or 1000 μmol mol?1 (elevated) CO2 and 0 g L?1 (deprivation) or 30 g L?1 (supplementation) sugar on morphological traits, photosynthetic attributes and intrinsic elements of the CAM pathway using the CAM orchid Phalaenopsis ‘Amaglade’. The growth of shoot (retarded) and root (induced) was differently affected by CO2 enrichment and mixotrophic regime (+sugar). The Fv/Fm ratio was 14% more in CO2-enriched treatment than at ambient level during in vitro growth. At elevated level of CO2 and sugar treatment, the content of Chl(a + b), Chl a/b and Chl/Car was enhanced while carotenoid content remained unaltered. During in vitro growth, gas-exchange analysis indicated that increased uptake of CO2 accorded with the increased rate of transpiration and unchanged stomatal conductance at elevated level of CO2 under both photo- and mixotrophic growth condition. At elevated level of CO2 and sugar deprivation, activities of Rubisco (26.4%) and PEPC (74.5%) was up-regulated. Among metabolites, the content of sucrose and starch was always higher under CO2 enrichment during both in vitro and ex vitro growth. Our results indicate that plantlets grown under CO2 enrichment developed completely viable photosynthetic apparatus ready to be efficiently transferred to ex vitro condition that has far-reaching implications in micropropagation of Phalaenopsis.  相似文献   

2.
Recent research on the photosynthetic mechanisms of plant species in the Chenopodiaceae family revealed that three species, including Bienertia sinuspersici, can carry out C4 photosynthesis within individual photosynthetic cells, through the development of two cytoplasmic domains having dimorphic chloroplasts. These unusual single-cell C4 species grow in semi-arid saline conditions and have semi-terete succulent leaves. The effects of salinity on growth and photosynthesis of B. sinuspersici were studied. The results show that NaCl is not required for development of the single-cell C4 system. There is a large enhancement of growth in culture with 50–200 mM NaCl, while there is severe inhibition at 400 mM NaCl. With increasing salinity, the carbon isotope values (δ13C) of leaves increased from −17.3o/oo (C4-like) without NaCl to −14.6o/oo (C4) with 200 mM NaCl, possibly due to increased capture of CO2 from the C4 cycle by Rubisco and reduced leakiness. Compared to growth without NaCl, leaves of plants grown under saline conditions were much larger (~2 fold) and more succulent, and the leaf solute levels increased up to ~2000 mmol kg solvent−1. Photosynthesis on an incident leaf area basis (CO2 saturated rates, and carboxylation efficiency under limiting CO2) and stomatal conductance declined with increasing salinity. On a leaf area basis, there was some decline in Rubisco content with increasing salinity up to 200 mM NaCl, but there was a marked increase in the levels of pyruvate, Pi dikinase, and phosphoenolpyruvate carboxylase (possibly in response to sensitivity of these enzymes and C4 cycle function to increasing salinity). The decline in photosynthesis on a leaf area basis was compensated for on a per leaf basis, up to 200 mM NaCl, by the increase in leaf size. The influence of salinity on plant development and the C4 system in Bienertia is discussed.  相似文献   

3.
4.
This study investigated the effects of a gradual versus step increases in carbon dioxide (CO2) on plant photosynthesis and growth at two nitrogen (N) levels. Plantago lanceolata were grown for 80 days and then treated with the ambient CO2 (as the control), gradual CO2 increase and step CO2 increase as well as low and high N additions for 70 days. While [CO2] were kept at constant 350 and 700 μmol mol−1 for the ambient and step CO2 treatments, respectively, [CO2] in the gradual CO2 treatment was raised by 5 μmol mol−1 day−1, beginning at 350 μmol mol−1 and reaching 700 μmol mol−1 by the end of experiment. The step CO2 treatment immediately resulted in an approximate 50% increase in leaf photosynthetic carbon fixation at both the low and high N additions, leading to a 20–24% decrease in leaf N concentration. The CO2-induced nitrogen stress, in return, resulted in partial photosynthetic downregulation since the third week at the low N level and the fourth week at the high N level after treatments. In comparison, the gradual CO2 treatment induced a gradual increase in photosynthetic carbon fixation, leading to less reduction in leaf N concentration. In comparison to the ambient CO2, both the gradual and step CO2 increases resulted in decreases in specific leaf area, leaf N concentration but an increase in plant biomass. Responses of plant shoot:root ratio to CO2 treatments varied with N supply. It decreased with low N supply and increased with high N supply under the gradual and step CO2 treatments relative to that under the ambient CO2. Degrees of those changes in physiological and growth parameters were usually larger under the step than the gradual CO2 treatments, largely due to different photosynthetic C influxes under the two CO2 treatments.  相似文献   

5.
To investigate the water-air diffusive greenhouse gases (GHGs) fluxes from the Three Gorges Reservoir (TGR), a field experiment on carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes from water surface was carried out from March 2011 to August 2012 by floating static chamber method. The results showed that CO2 was released to the atmosphere all the time and was less in autumn than in other seasons (P < 0.05). CH4 was also released to the atmosphere throughout the year but more in summer than other three seasons (P < 0.05). N2O flux was higher in autumn than other seasons (P < 0.05), and N2O was absorbed from the atmosphere mainly in summer. Moreover, correlation analysis illustrated that CO2 flux had significantly negative correlation with wind velocity (P < 0.05), whereas positive correlation with pH (P < 0.01) had been found. There was no significant correlation between CH4 (or N2O) flux and the measured environmental variables respectively (P > 0.05). Additionally, the annual fluxes of CO2, CH4 and N2O were 140.45 ± 12.57 mg CO2·m?2 h?1, 1.35 ± 0.14 mg CH4·m?2 h?1 and 34.34 ± 11.64 μg N2O·m?2 h?1, respectively. When compared to other reservoirs worldwide, the CO2 and N2O fluxes from TGR were higher than those from boreal and temperate reservoirs, but much lower than those from tropical reservoirs. CH4 flux was lower than those from boreal, temperate and most tropical reservoirs. In our study, the surface area of the TGR emitted 1.42 × 106 t CO2, 1.19 × 104 t CH4 and 589.93 t N2O in a year. The total GWP was 17.68 t CO2-eq ha?1 yr?1, of which CO2 flux was dominant (74.38%). Therefore, CO2 was the main contributor of GHGs fluxes in our study and thus future researches should focus on how to reduce CO2 fluxes from the surface of the TGR. TGR has a considerable contribution to regional GHG emissions.  相似文献   

6.
Cotton (Gossypium hirsutum L. cv Acala SJ2) plants were exposed to three levels of osmotic or matric potentials. The first was obtained by salt and the latter by withholding irrigation water. Plants were acclimated to the two stress types by reducing the rate of stress development by a factor of 4 to 7. CO2 assimilation was then determined on acclimated and nonacclimated plants. The decrease of CO2 assimilation in salinity-exposed plants was significantly less in acclimated as compared with nonacclimated plants. Such a difference was not found under water stress at ambient CO2 partial pressure. The slopes of net CO2 assimilation versus intercellular CO2 partial pressure, for the initial linear portion of this relationship, were increased in plants acclimated to salinity of −0.3 and −0.6 megapascal but not in nonacclimated plants. In plants acclimated to water stress, this change in slopes was not significant. Leaf osmotic potential was reduced much more in acclimated than in nonacclimated plants, resulting in turgor maintenance even at −0.9 megapascal. In nonacclimated plants, turgor pressure reached zero at approximately −0.5 megapascal. The accumulation of Cl and Na+ in the salinity-acclimated plants fully accounted for the decrease in leaf osmotic potential. The rise in concentration of organic solutes comprised only 5% of the total increase in solutes in salinity-acclimated and 10 to 20% in water-stress-acclimated plants. This acclimation was interpreted in light of the higher protein content per unit leaf area and the enhanced ribulose bisphosphate carboxylase activity. At saturating CO2 partial pressure, the declined inhibition in CO2 assimilation of stress-acclimated plants was found for both salinity and water stress.  相似文献   

7.
《Fungal biology》2022,126(4):300-307
The effects of water stress and temperature on in vitro growth and enzymatic activity of Purpureocillium lilacinum (Sordariomycetes, Hypocreales, Ophiocordycipitaceae) isolates with demonstrated capacity to control Nacobbus aberrans (Secernentea, Tylenchida, Pratylenchidae) were evaluated in this study. Also, saprophytic and endophytic colonization in tomato plants were determined. P. lilacinum was able to grow under the evaluated levels of osmotic and matric stress, but the increase in water stress caused reductions in radial growth rates. Moreover, the fungal isolates produced chitinases, proteases, and leucinostatins under inductive conditions. The nematophagous fungi were able to develop saprophytically (104 CFU g?1 of soil). Meanwhile, only P. lilacinum SR38 demonstrated endophytic capacity. The results suggest that P. lilacinum can be effectively applied as biocontrol agents of phytoparasitic nematodes in tomatoes under variable agroecological conditions.  相似文献   

8.

Suaeda fruticosa and S. monoica are important halophytes for ecological rehabilitation of saline lands. We report differential physio-chemical, photosynthetic, and chlorophyll fluorescence responses in these halophytes under 100 mM sodium chloride (NaCl), 50% strength (16.25 ppt) of seawater (SW)-imposed salinity, and 10% polyethylene glycol 6000 imposed osmotic stress at 380 (ambient) and 1200 (elevated) µmol mol–1 CO2 concentrations. SW salinity enhanced the growth in both species; however, compared with S. fruticosa, the S. monoica exhibited comparatively better growth and biomass accumulation under saline conditions at elevated CO2. Results demonstrated better photosynthetic performances of S. monoica under stress conditions at both levels of CO2, and this resulted in higher accumulation of carbon, nitrogen, sugar, and starch contents. S. monoica exhibited improved antenna size, electron transfer at PSII donor side, and efficient working of photosynthetic machinery at elevated CO2, which might be due to efficient upstream utilization of reducing power to fix the CO2. The δ13C results supported the operation of C4 CO2 fixation in S. monoica and C3 or intermediate pathway of CO2 fixation in S. fruticosa. Lower accumulation of reactive oxygen species, reduced membrane damage, lowered solute potential, and higher accumulation of proline and polyphenol contents indicated elevated CO2-induced abiotic stress tolerance in Suaeda. Higher activity of antioxidant enzymes in both species at both levels of CO2 help plants to combat the oxidative stress. Upregulation of NADP-dependent malic enzyme and NADP-dependent malate dehydrogenase genes indicated their role in abiotic stress tolerance as well as photosynthetic carbon (C) sequestration. Operation of C4 type CO2 fixation in S. monoica and an intermediate CO2 fixation in S. fruticosa could be the possible reason for the superior photosynthetic efficiency of S. monoica under stress conditions at elevated CO2.

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9.
Atmospheric CO2 enrichment may impact arbuscular mycorrhizae (AM) development and function, which could have subsequent effects on host plant species interactions by differentially affecting plant nutrient acquisition. However, direct evidence illustrating this scenario is limited. We examined how elevated CO2 affects plant growth and whether mycorrhizae mediate interactions between C4 barnyard grass (Echinochloa crusgalli (L.) Beauv.) and C3 upland rice (Oryza sativa L.) in a low nutrient soil. The monocultures and combinations with or without mycorrhizal inoculation were grown at ambient (400 ± 20 μmol mol?1) and elevated CO2 (700 ± 20 μmol mol?1) levels. The 15N isotope tracer was introduced to quantify the mycorrhizally mediated N acquisition of plants. Elevated CO2 stimulated the growth of C3 upland rice but not that of C4 barnyard grass under monoculture. Elevated CO2 also increased mycorrhizal colonization of C4 barnyard grass but did not affect mycorrhizal colonization of C3 upland rice. Mycorrhizal inoculation increased the shoot biomass ratio of C4 barnyard grass to C3 upland rice under both CO2 concentrations but had a greater impact under the elevated than ambient CO2 level. Mycorrhizae decreased relative interaction index (RII) of C3 plants under both ambient and elevated CO2, but mycorrhizae increased RII of C4 plants only under elevated CO2. Elevated CO2 and mycorrhizal inoculation enhanced 15N and total N and P uptake of C4 barnyard grass in mixture but had no effects on N and P acquisition of C3 upland rice, thus altering the distribution of N and P between the species in mixture. These results implied that CO2 stimulation of mycorrhizae and their nutrient acquisition may impact competitive interaction of C4 barnyard grass and C3 upland rice under future CO2 scenarios.  相似文献   

10.
In response to an osmotic stress, Dunaliella tertiolecta osmoregulates by metabolizing intracellular glycerol as compatible solute. Upon the application of a salt stress to 0.17 M or 0.7 M NaCl grown D. tertiolecta cells, rates of total glycerol synthesis were substantially higher than that arising from photosynthetic 14CO2 fixation into glycerol. The source of this extra carbon is the reserve starch pool. The contribution of carbon from the starch breakdown to glycerol synthesis was estimated from the difference between the total glycerol synthesized and that arising from 14CO2 fixation. The maximum observed flux of carbon from 14CO2 to glycerol from photosynthesis was of the order of 15–20 μmol 14C-glycerol mg−1 Chl h−1, whereas the total glycerol synthesis reached about 70 μmol glycerol mg−1 Chl h−1. The contribution of products of starch breakdown to glycerol synthesis increased progressively with increasing salt stress. In light, contrary to prevailing assumptions, both the photosynthesis and the starch breakdown contribute carbon to glycerol biosynthesis. The relative contributions of these two processes in the light, while cells were actively photosynthesizing, depended on the magnitude of the salt stress. On application of dilution stress, the flux of carbon from newly photosynthetically fixed 14CO2 into glycerol was reduced progressively with increasing dilution stress that was also accompanied by a decline in total glycerol contents of the cell. The maximum observed rate of glycerol dissimilation was about 135 μmol glycerol mg−1 Chl h−1.  相似文献   

11.
《Fungal Ecology》2008,1(2-3):102-106
The effect of temperature and different solute (Ψs) and matric potentials (Ψm) on growth and sporulation of three aflatoxigenic strains of Aspergillus flavus isolated from contaminated maize in northern Italy was determined. The Ψs of maize-based media were modified ionically (NaCl) and non-ionically (glycerol) and the Ψm with PEG 8000 in the range −1.4 to −21.0 MPa at 25 and 30 °C. Both temperature and Ψs/Ψm stress had statistically significant effects on growth rates of the three strains. Faster growth occurred at 30 °C and −1.4 and −2.8 MPa. A. flavus strains were more sensitive to Ψm than Ψs stress with limits of −9.8 MPa and −14 to−18 MPa, respectively. Sporulation was significantly influenced by Ψs potential, solute type and temperature. This suggests that these aflatoxigenic strains of A. flavus isolated from aflatoxin-contaminated maize are probably able to colonise crop debris rapidly at prevailing temperatures and water stress conditions. This type of information on the ecology of aflatoxin producing A. flavus strains isolated in Italy will contribute to the development of a systems model to predict their activity in crop residue and colonisation of maize grain.  相似文献   

12.
《Biological Control》2013,64(3):310-319
The biocontrol potential of Pochonia chlamydosporia, a fungus with parasitic activity against economically important plant-parasitic nematodes, can be influenced by abiotic factors such as water availability. The objective of this study was to evaluate the effects of different water stress regimes on in vitro growth, sporulation, germination and parasitism of P. chlamydosporia isolates. The osmotic water potential of 1.7% corn meal agar (CMA) was modified by addition of potassium chloride (KCl) or glycerol, and the matric water potential was modified using polyethylene glycol (PEG 8000). The fungus was able to grow over a range of potentials but radial growth rates decreased with the increase of osmotic and matric stress. No growth was observed at −10 MPa on 1.7% CMA amended with glycerol and at −7.1 MPa on medium with PEG 8000 but all isolates were able to resume growth when transferred onto unmodified 1.7% CMA. The production of chlamydospores was repressed in both osmotic and matric modified media. Although the production of conidia increased in medium modified with KCl, the germination rate was lower. Spores/hyphal fragments remained viable in all isolates that were previously inoculated onto media with growth-limiting water potential (−10 MPa on 1.7% CMA amended with glycerol and −10 MPa on medium with PEG 8000). The percentage of viable conidia produced on 1.7% CMA, after inoculation under osmotic or matric stress conditions for 25 days, was over 74.5% in all isolates (osmotic stress) and ranged from 1% (Pc1) to 65.8% (Pc280) (matric stress). The in vitro infection of potato cyst nematodes, Globodera rostochiensis eggs by P. chlamydosporia isolates, grown under these limiting conditions, was studied using a standard bioassay. The percentage of parasitized eggs was significantly higher under osmotic stress except for isolates Pc2 and Pc3. P. chlamydosporia spores/hyphal fragments can remain viable at water potentials limiting for growth, for prolonged periods of time, suggesting that the osmoregulation mechanisms, used to compensate water stress, affect in vitro sporulation and increased pathogenicity. Knowledge on water requirements of P. chlamydosporia enables a better understanding of its survival and growth strategies in the soil environment and could aid the development of effective strategies to increase the production and quality of inoculum, thus contributing to the implementation of biosafe, sustainable management strategies against plant-parasitic nematodes.  相似文献   

13.
In recent decades, the frequency and intensity of harmful algal blooms (HABs), as well as a profusion of toxic phytoplankton species, have significantly increased in coastal regions of China. Researchers attribute this to environmental changes such as rising atmospheric CO2 levels. Such addition of carbon into the ocean ecosystem can lead to increased growth, enhanced metabolism, and altered toxicity of toxic phytoplankton communities resulting in serious human health concerns. In this study, the effects of elevated partial pressure of CO2 (pCO2) on the growth and toxicity of a strain of Alexandrium tamarense (ATDH) widespread in the East and South China Seas were investigated. Results of these studies showed a higher specific growth rate (0.31 ± 0.05 day−1) when exposed to 1000 μatm CO2, (experimental), with a corresponding density of (2.02 ± 0.19) × 107 cells L−1, that was significantly larger than cells under 395 μatm CO2(control). These data also revealed that elevated pCO2 primarily affected the photosynthetic properties of cells in the exponential growth phase. Interestingly, measurement of the total toxin content per cell was reduced by half under elevated CO2 conditions. The following individual toxins were measured in this study: C1, C2, GTX1, GTX2, GTX3, GTX4, GTX5, STX, dcGTX2, dcGTX3, and dcSTX. Cells grown in 1000 μatm CO2 showed an overall decrease in the cellular concentrations of C1, C2, GTX2, GTX3, GTX5, STX, dcGTX2, dcGTX3, and dcSTX, but an increase in GTX1 and GTX4. Total cellular toxicity per cell was measured revealing an increase of nearly 60% toxicity in the presence of elevated CO2 compared to controls. This unusual result was attributed to a significant increase in the cellular concentrations of the more toxic derivatives, GTX1 and GTX4.Taken together; these findings indicate that the A. tamarense strain ATDH isolated from the East China Sea significantly increased in growth and cellular toxicity under elevated pCO2 levels. These data may provide vital information regarding future HABs and the corresponding harmful effects as a result of increasing atmospheric CO2.  相似文献   

14.
Studies of selected morphological needle parameters were carried out on young (17–19 year old) Norway spruce trees cultivated inside glass domes at ambient (A, 370 μmol (CO2) mol−1) and elevated (E, 700 μmol (CO2) mol−1) atmospheric CO2 concentrations [CO2] beginning in 1997. Annual analyses performed from 2002 to 2004 revealed higher values for needle length (especially for current needles, up to 18%) and projected needle area (up to 13%) accompanied by lower values for specific needle area (up to 15% lower, as quantified by needle mass to projected area ratio) in the E treatment compared to the A treatment. Statistically significant differences for most of the investigated morphological parameters were found in young needles in the well irradiated sun-adapted crown parts, particularly under water-limiting soil conditions in 2003. This was likely a result of different water relations in E compared to A trees as investigated under temperate water stress (Kuper et al. in Biol Plantarum 50:603–609, 2006). Furthermore, E trees had much higher absorbing root area, which modified and enhanced root:shoot as well as root:conductive stem area proportions. These hydraulic properties and early seasonal stimulation of photosynthesis forced advanced needle development in E trees, particularly under limited soil water conditions. The number of needles per unit shoot length was found to be unaffected by elevated [CO2].  相似文献   

15.
Some plants accumulate some compatible solutes and exude various organic acids when exposed to environmental stress. These compatible solutes including proline have been suggested to be involved in stress tolerance by maintaining sufficient cell turgor for growth, thereby improving plant growth, protecting enzymes, and membranes. However, less evidence exists regarding the protective roles of organic acids under stress conditions. Here, we investigate the effects of citric acid as a component of the response to stress on plant growth and antioxidant enzyme activities in two genotypes of halophyte Leymus chinensis (Trin.) genotypes, LcWT07 and LcJS0107. Data showed that both saline stress (200 mM NaCl) and alkaline stress (100 mM Na2CO3) reduced plant growth on the relative growth rate and CO2 assimilation rate, but increased the citric acid concentrations in 6-week-old plants over the 72 h experimental period. When 50 mg l−1 citric acid was exogenously applied under stress conditions, it significantly improved the plant growth and internal citric acid concentration, and also induced defense mechanisms by increasing the activities of antioxidant enzymes. To compare with the mitigative effects of exogenous citric acid on stress, exogenous application of proline was also performed under same conditions, and similar effects on the improvement of growth were observed. Based on these results, we suggested that citric acid is an important component of the stress response in L. chinensis, and exogenous application of 50 mg l−1 citric acid might play a positive role on stress tolerance.  相似文献   

16.
Tomato plants expressing the maize sucrose-phosphate synthase (SPS) cDNA under the control of the promoterof the small subunit of ribulose-1,5-bisphosphate carboxylase oxygenase (rbcS) promoter were grown 5 weeks in air (450 μmol.m–2.s–1 irradiance, 350 ppm CO2) and then either maintained in air or exposed to CO2 enrichment (1 000 ppm CO2) for 8 d. A linear relationship between the foliar sucrose to starch ratio and maximal extractable SPS activity was found both in air and high CO2. Starch accumulation was dramatically increased in all plants subjected to CO2 enrichment but the CO2-dependent increase in foliar starch accumulation was much lower in the leaves of the SPS transformants than in those of the untransformed controls in the same conditions. Maximal extractable ribulose-1,5-bisphosphate carboxylase/oxygenase activity was reduced by growth at high CO2 to a similar extent in both plant types. The carbon/nitrogen ratios were similar in both plant lines in both growth conditions after 20 d exposure to high CO2. A small (5 %) increase in carbon export capacity was observed at high CO2 in the leaves of transformed plants compared to leaves from untransformed controls. Increased foliar SPS activity did not, however, prevent acclimation of photosynthesis in plants grown with long-term CO2 enrichment.  相似文献   

17.
The impact of microphytobenthos and different abundances of macrofauna (Nereis diversicolor) on temporal variation of benthic metabolism was investigated in laboratory microcosms. Measurements primarily included diurnal fluxes of O2 and CO2 as well as sediment profiles of Chlorophyll a and extracellular polymeric substances (EPS). Net and gross primary production (2-5 and 4-7 mmol CO2 m− 2 h− 1, respectively) were relatively stable in both defaunated and faunated sediment throughout a 12 h light period. The CO2 release from sediments immediately after onset of darkness ranged from 1.5 to 3.5 mmol CO2 m− 2 h− 1 followed by a consistent decrease during the next 12 h in the dark. The decrease was more conspicuous in faunated (about 50%) than defaunated (9%) sediment. Total carbon oxidation was in both cases fuelled primarily by microphytobenthic biomass, while EPS only contributed by 1-4%. Diurnal measurements of Nereis diversicolor ventilation activity showed a significant decrease in the dark that corresponds well to the observed decrease in total metabolic activity. It is concluded that changes in solute exchange associated with animals and burrows (e.g. microbial respiration) is a major controlling factor for total sediment metabolism. In general, the faunal impact was evident as about 50% enhanced CO2 release in the dark, while net primary production was reduced by 30-50%. The turnover time of produced organic carbon is therefore considerably shorter in the presence than absence of macrofauna. Thus, the daily average exchange of CO2 was almost balanced in bioturbated sediment with a 43% share of carbon oxidation mediated by direct faunal respiration. Defaunated sediment was net autotrophic with daily primary production exceeding microbial carbon oxidation by 40%. The present study clearly demonstrates that knowledge on interactions between microphytobenthos and macrofauna is essential for understanding carbon dynamics in shallow sediments.  相似文献   

18.
Animal experiments and preliminary clinical results showed that the N2S2-complex 99mTc CO2-DADS-A, which was claimed to be a potential replacement for o-I-hippurate as a renal function agent, had a lower affinity for the tubular transport system than o-1-hippurate.In order to evaluate if this finding offered the possibility of detecting decreases in tubular function with more sensitivity, or at earlier times, 6 patients in the early post-transplantation period were subjected to 53 simultaneous scintigraphic investigations with 131I o-I-hippurate and 99mTc CO2-DADS-A. The comparison of the renograms obtained with the respective agents showed that in almost all cases of acute graft rejection only o-I-hippurate yielded the typical, diagnostically useful accumulation curve which results from its high retention in the kidney parenchyma. 99mTc CO2-DADS-A did not reveal this effect.Additionally the plasma clearance of each agent was measured simultaneously under steady state conditions in nine patients. Although it was reported that relative to o-I-hippurate the analog images obtained with 99mTc CO2-DADS-A gave higher kidney-to-background ratios and the amount excreted in the urine at 30 min was slightly less, the clearance values obtained for 99mTc CO2-DADS-A were on average only 36% of those for o-I-hippurate.It is concluded that 99mTc CO2-DADS-A is not suitable as a substitute for o-I-hippurate.  相似文献   

19.
《Aquatic Botany》2005,83(1):71-81
The aquatic plant Elodea nuttallii (Planch.) St. John has been shown to express plasticity in the source of inorganic carbon it uses for photosynthesis. An investigation was undertaken to determine what effect the switch from CO2 to HCO3 use had on the growth of E. nuttallii. Plants were grown under reduced CO2 availability that favoured the switch, together with control plants (CO2 at equilibrium with air) that continued to use CO2 only. The extent to which both sets of plants could utilise HCO3 was determined (as the ratio of oxygen evolution at pH 9 and 6.5), and several measures of growth were made. Although reduced CO2 availability produced an increase in HCO3 utilisation, no differences were found in the measured growth of the plants. Therefore, it was possible to estimate, from the difference between the estimated rate of photosynthesis of the plants utilising HCO3 and those using CO2 only, the approximate cost of constructing, maintaining and running the bicarbonate utilisation mechanism in this species as 69 μmol photons m−2 s−1. This value can be used to estimate an irradiance of circa 80 μmol m−2 s−1 below which HCO3 use would not be expected in this species, an irradiance commonly experienced by submerged macrophytes in the field.  相似文献   

20.
Jiangsu Province has become one of the most developed regions in China. Economic growth in Jiangsu has occurred along with rising energy-related CO2 emission levels. Thus, the link between economic activity and environmental pressure represents a risk to the global efforts toward CO2 emission reductions. This paper examines the occurrence of a decoupling between the growth rates in economic activity and CO2 emission from energy consumption in Jiangsu from 1995 to 2009. The results indicate that: (1) Along with the rapid economic development, CO2 emission in Jiangsu rose from 18,781.46 × 104 t in 1995 to 52,029.24 × 104 t in 2009, with an average annual growth rate of 7.54%. Our results also show that CO2 emission in Jiangsu Province is dominated by the secondary, which accounts for about 80% of total CO2 emission. (2) During the study period, the whole Jiangsu economy experienced weak decoupling and strong decoupling except 2003–2005. However the decoupling states for the secondary and tertiary industries are similar to that of the whole economy.  相似文献   

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