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1.
Effects of the current (38 Pa) and an elevated (74 Pa) CO2 partial pressure on root and shoot areas, biomass accumulation and daily net CO2 exchange were determined for Opuntia ficus-indica (L.) Miller, a highly productive Crassulacean acid metabolism species cultivated worldwide. Plants were grown in environmentally controlled rooms for 18 weeks in pots of three soil volumes (2 600, 6 500 and 26 000 cm3), the smallest of which was intended to restrict root growth. For plants in the medium-sized soil volume, basal cladodes tended to be thicker and areas of main and lateral roots tended to be greater as the CO2 level was doubled. Daughter cladodes tended to be initiated sooner at the current compared with the elevated CO2 level but total areas were similar by 10 weeks. At 10 weeks, daily net CO2 uptake for the three soil volumes averaged 24% higher for plants growing under elevated compared with current CO2 levels, but at 18 weeks only 3% enhancement in uptake occurred. Dry weight gain was enhanced 24% by elevated CO2 during the first 10 weeks but only 8% over 18 weeks. Increasing the soil volume 10-fold led to a greater stimulation of daily net CO2 uptake and biomass production than did doubling the CO2 level. At 18 weeks, root biomass doubled and shoot biomass nearly doubled as the soil volume was increased 10-fold; the effects of soil volume tended to be greater for elevated CO2. The amount of cladode nitrogen per unit dry weight decreased as the CO2 level was raised and increased as soil volume increased, the latter suggesting that the effects of soil volume could be due to nitrogen limitations.  相似文献   

2.
In situ responses to elevated CO2 in tropical forest understorey plants   总被引:3,自引:1,他引:2  
1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO2. We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula ) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius ) of elevated CO2 treatment ( c. 700 μl litre–1) under mean QFD of less than 11 μmol m–2 s–1, all species produced more biomass (25–76%) under elevated CO2.
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m–2 s–1) but the relative stimulation by elevated CO2 was higher at low QFD except in Pharus .
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO2. An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO2 continues to rise.  相似文献   

3.
The long-term response of Arabidopsis thaliana to increasing CO2 was evaluated in plants grown in 800 μl l−1 CO2 from sowing and maintained, in hydroponics, on three nitrogen supplies: "low,""medium" and "high." The global response to high CO2 and N-supply was evaluated by measuring growth parameters in parallel with photosynthetic activity, leaf carbohydrates, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) messenger RNA and protein, stomatal conductance (gs) and density. CO2 enrichment was found to stimulate biomass production, whatever the N-supply. This stimulation was transient on low N-supply and persisted throughout the whole vegetative growth only in high N-supply. Acclimation on low N–high CO2 was not associated with carbohydrate accumulation or with a strong reduction in Rubisco amount or activity. At high N-supply, growth stimulation by high CO2 was mainly because of the acceleration of leaf production and expansion while other parameters such as specific leaf area, root/shoot ratio and gs appeared to be correlated with total leaf area. Our results thus suggest that, in strictly controlled and stable growing conditions, acclimation of A. thaliana to long-term CO2 enrichment is mostly controlled by growth rate adjustment.  相似文献   

4.
Abstract A denitrifying Cytophaga was isolated from soil enriched by anaerobic incubation with glucose, sulfide (S2−), nitrous oxide (N2O), and acetylene (C2H2). Such soil enrichments and pure cultures of the isolated Cytophaga reduced N2O rapidly even in the presence of a normally inhibitory concentration of C2H2 (4 kPa) providing S2− was present (8 μmol/g soil or 0.4 μmol/ml culture). Since C2H2 inhibition of the reduction of N2O is used as a tool in the assay of denitrification, the presence in large numbers of such a Cytophaga may influence the effectiveness of this assay especially in sulfidic environments.  相似文献   

5.
Dry weight (DW) and nitrogen (N) accumulation and allocation were measured in isolated plants of Danthonia richardsonii (Wallaby Grass) for 37 d following seed imbibition. Plants were grown at ≈ 365 or 735 μ L L–1 CO2 with N supply of 0·05, 0·2 or 0·5 mg N plant–1 d–1. Elevated CO2 increased DW accumulation by 28% (low-N) to 103% (high-N), following an initial stimulation of relative growth rate. Net assimilation rate and leaf nitrogen productivity were increased by elevated CO2, while N concentration was reduced. N uptake per unit root surface area was unaffected by CO2 enrichment. The ratio of leaf area to root surface area was decreased by CO2 enrichment. Allometric analysis revealed a decrease in the shoot-N to root-N ratio at elevated CO2, while the shoot-DW to root-DW ratio was unchanged. Allometric analysis showed leaf area was reduced, while root surface area was unchanged by elevated CO2, indicating a down-regulation of total plant capacity for carbon gain rather than a stimulation of mineral nutrient acquisition capacity. Overall, growth in elevated CO2 resulted in changes in plant morphology and nitrogen use, other than those associated simply with changing plant size and non-structural carbohydrate content.  相似文献   

6.
Vibeke Holter 《Ecography》1984,7(2):165-170
Nitrogen fixation activity was determined for Lotus tenuis. Medicago lupulina and Trifolium pratense . The three species grew in clones in grassland in an area reclaimed from brackish water in the 1940s. The N2[C2H2]-fixation was measured in soil cores throughout 1974 and 1975. From cores taken in dense and uniform stands of the species, the yearly N2[C2H2]-fixation at maximum cover was estimated. L. tenuis fixed about 4 g N m−2 yr−1 (area with max. cover 130%), i.e. 30–56% of its requirement. Both M. lupulina and T. pratense fixed about 7 g N m−2 yr−1 (maximum cover 37% and 80%) i.e. 67% of their N-requirement. Average N2[C2H2]-fixation for the whole area was 0.4 g N m−2 yr−1, considerably less than the N-addition through rainfall.  相似文献   

7.
Seedlings of three species native to central North America, a C3 tree, Populus tremuloides Michx., a C3 grass, Agropyron smithii Rybd., and a C4 grass, Bouteloua curtipendula Michx., were grown in all eight combinations of two levels each of CO2, O3 and nitrogen (N) for 58 days in a controlled environment. Treatment levels consisted of 360 or 674 μmol mol-1 CO2, 3 or 92 nmol mol-1 O3, and 0.5 or 6.0 m M N. In situ photosynthesis and relative growth rate (RGR) and its determinants were obtained at each of three sequential harvests, and leaf dark respiration was measured at the second and third harvests. In all three species, plants grown in high N had significantly greater whole-plant mass, RGR and photosynthesis than plants grown in low N. Within a N treatment, elevated CO2 did not significantly enhance any of these parameters nor did it affect leaf respiration. However, plants of all three species grown in elevated CO2 had lower stomatal conductance compared to ambient CO2-exposed plants. Seedlings of P. tremuloides (in both N treatments) and B. curtipendula (in high N) had significant ozone-induced reductions in whole-plant mass and RGR in ambient but not under elevated CO2. This negative O3 impact on RGR in ambient CO2 was related to increased leaf dark respiration, decreased photosynthesis and/or decreased leaf area ratio, none of which were noted in high O3 treatments in the elevated CO2 environment. In contrast, A. smithii was marginally negatively affected by high O3.  相似文献   

8.
Abstract. Gas exchange measurements were made on single leaves of three C3 and one C4 species at air speeds of 0.4 and 4.0 m s−1 to determine if boundary layer conductance substantially affected the substomatal pressure of carbon dioxide. Boundary layer conductances to water vapour were 0.4 to 0.5 mol m−2 s−1 at the lower air speed, and 1.2 to 1.5 mol m−2 s−1 at the higher air speed. Substomatal carbon dioxide pressures were about 5 Pa lower at low boundary layer conductance in the C3 species, and about 3 Pa lower in the C4 species when measurements were made at high and moderate photosynthetic photon flux densities. No evidence of stomatal adjustment to altered boundary layer conductance was found. Photosynthetic rates at high photon flux densities were reduced by about 20% at the low air speed in the C3 species. The commonly reported values of substomatal carbon dioxide pressure for C3 and C4 species were found to occur only when measurements were made at the higher air speed.  相似文献   

9.
Abstract. A field study was conducted to determine the relationship of solar-excited chlorophyll a fluorescence to net CO2 assimilation rate in attached leaves. The Fraunhofer line-depth principle was used to measure fluorescence at 656.3 nm wavelength while leaves remained exposed to full sunlight and normal atmospheric pressures of CO2 and O2. Fluorescence induction kinetics were observed when leaves were exposed to sunlight after 10 min in darkness. Subsequently, fluorescence varied inversely with assimilation rate. In the C4 Zea mays , fluorescence decreased from 2.5 to 0.8 mW m-2 nm-1 as CO2 assimilation rate increased from 1 to 8 μmol m-2 s-1 (r2= 0.520). In the C3 Liquidambar styraciflua and Pinus taeda , fluorescence decreased from 6 to 2 mW m-2 nm-1 as assimilation rate increased from 2 to 5 or 0 to 2 μmol m-2 s-1 (r2= 0.44 and 0.45. respectively). The Fraunhofer line-depth principle enables the simultaneous measurement of solar-excited fluorescence and CO2 assimilation rate in individual leaves, but also at larger scales. Thus, it may contribute significantly to field studies of the relationship of fluorescence to photosynthesis.  相似文献   

10.
The physiological characteristics of holm oak ( Quercus ilex L.) resprouts originated from plants grown under current CO2 concentration (350 μl l−1) (A-resprouts) were compared with those of resprouts originated from plants grown under elevated CO2 (750 μl l−1) (E-resprouts). At their respective CO2 growth concentration, no differences were observed in photosynthesis and chlorophyll fluorescence parameters between the two kinds of resprout. E-resprouts appeared earlier and showed lower stomatal conductance, higher water-use efficiency and increased growth (higher leaf, stem and root biomass and increased height). Analyses of leaf chemical composition showed the effect of elevated [CO2] on structural polysaccharide (higher cellulose content), but no accumulation of total non-structural carbohydrate on area or dry weight basis was seen. Four months after appearance, downregulation of photosynthesis and electron transport components was observed in E-resprouts: lower photosynthetic capacity, photosystem II quantum efficiency, photochemical quenching of fluorescence and relative electron transport rate. Reduction in ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) activity, deduced from the maximum carboxylation velocity of RuBisCo, accounts for the observed acclimation. Increased susceptibility of photosynthetic apparatus to increasing irradiance was detected in E-resprouts.  相似文献   

11.
Abstract. The objective of this study was to investigate the effects of water stress in sweet potato ( Ipomoea batatas L. [Lam] 'Georgia Jet') on biomass production and plant-water relationships in an enriched CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first 12 d of water stress, leaf xylem potentials were higher in plants grown in a CO2 concentration of 438 and 666 μmol mol−1 than in plants grown at 364 μmol mol−1. The 364 μmol mol−1 CO2 grown plants had to be rewatered 2 d earlier than the high CO2-grown plants in response to water stress. For plants grown under water stress, the yield of storage roots and root: shoot ratio were greater at high CO2 than at 364 μmol mol−1; the increase, however, was not linear with increasing CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at elevated CO2, and these were greater as compared to water-stressed plants grown at the same CO2 concentration.  相似文献   

12.
Eragrostis pilosa (Linn.) P Beauv., a C4 grass native to east Africa, was grown at both ambient (350 μmol mol−1 and elevated (700 μmol mol−1) CO2 in either the presence or absence of the obligate, root hemi-parasite Striga hermonthica (Del.) Benth. Biomass of infected grasses was only 50% that of uninfected grasses at both CO2 concentrations, with stems and reproductive tissues of infected plants being most severely affected. By contrast, CO2 concentration had no effect on growth of E. pilosa , although rates of photosynthesis were enhanced by 30–40% at elevated CO2. Infection with S. hermonthica did not affect either rates of photosynthesis or leaf areas of E. pilosa , but did bring about an increase in root:shoot ratio, leaf nitrogen and phosphorus concentration and a decline in leaf starch concentration at both ambient and elevated CO2. Striga hermonthica had higher rates of photosynthesis and shoot concentrations of soluble sugars at elevated CO2, but there was no difference in biomass relative to ambient grown plants. Both infection and growth at elevated CO2 resulted in an increase in the Δ13C value of leaf tissue of E. pilosa , with the CO2 effect being greater. The proportion of host-derived carbon in parasite tissue, as determined from δ13C values, was 27% and 39% in ambient and elevated CO2 grown plants, respectively. In conclusion, infection with S. hermonthica limited growth of E. pilosa , and this limitation was not removed or alleviated by growing the association at elevated CO2.  相似文献   

13.
The effects of photon flux density and temperature on net photosynthesis and transpiration rates of mature and immature leaves of three-year-old Japanese larch Larix kaempferi (Lamb.) Sarg. trees were determined with an infrared, differential open gas analysis system. Net photosynthetic response to increasing photon flux densities was similar for different foliage positions and stage of maturity. Light compensation was between 25 and 50 μmol m−2 s−1. Rates of photosynthesis increased rapidly at photon flux densities above the compensation level and became saturated between 800 and 1000 μmol m−2 s−1. Transpiration rates at constant temperature likewise increased with increasing photon flux density, and leveled off between 800 and 1000 μmol m−2 s−1. Photosynthetic response to temperature was determined in saturating light and was similar for all foliage positions; it increased steadily from low temperatures to an optimum range betweeen 15 and 21°C and then decreased rapidly above 21°C. Transpiration rate, however, increased continuously with rising temperature up to the experimental maximum. CO2 compensation concentrations for mature foliage varied between 58 and 59 μl l−1; however, foliage borne at the apex of the terminal leader compensated at 75 μl l−1. None of these data support the claim that Japanese larch possesses C4 photosynthetic characteristics.  相似文献   

14.
Rice ( Oryza sativa L. cv. IR72) was grown at three different CO2 concentrations (ambient, ambient + 200 μmol mol−1, ambient + 300 μmol mol−1) at two different growth temperatures (ambient, ambient + 4°C) from sowing to maturity to determine longterm photosynthetic acclimation to elevated CO2 with and without increasing temperature. Single leaves of rice showed a cooperative enhancement of photosynthetic rate with elevated CO2 and temperature during tillering, relative to the elevated CO2 condition alone. However, after flowering, the degree of photosynthetic stimulation by elevated CO2 was reduced for the ambient + 4°C treatment. This increasing insensitivity to CO2 appeared to be accompanied by a reduction in ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco) activity and/or concentration as evidenced by the reduction in the assimilation (A) to internal CO2 (C1) response curve. The reproductive response (e.g. percent filled grains, panicle weight) was reduced at the higher growth temperature and presumably reflects a greater increase in floral sterility. Results indicate that while CO2 and temperature could act synergistically at the biochemical level, the direct effect of temperature on floral development with a subsequent reduction in carbon utilization may change sink strength so as to limit photosynthetic stimulation by elevated CO2 concentration.  相似文献   

15.
An open flow-through gas system was used to investigate the effect of plant age on nitrogenase activity in relation to root respiration (measured as CO2 release) and supra-ambient O2 levels in 24- to 51-day-old, nodulated Pisum sativum L. cv. Bodil. The effect of assaying plants repeatedly was also studied. The respiratory efficiency of nitrogenase [mol CO2 (mol C2H4)−1] and the relative decline in nitrogenase (EC 1.7.99.2) activity in response to introduction of C2H2 in the gas stream were unaffected by plant age. In contrast, the nitrogenase-linked respiration as a proportion of total root respiration increased with time. Accordingly, the specific respiration linked-to growth and maintenace of the noduled root system decreased with time. C2H2 reduction and root respiration were increased by supra-ambient O2 levels, but the tolerance to high O2 concentrations seemed to decrease with plant age. Repeated C2H2 assays on the same plants decreased their rate of growth and N accumulation: in addition, nitrogenase activity and root respiration were somewhat negatively affected. The results indicate that results from experiments with plants of different ages cannot always be directly compared, and that repeated C2H2 assays on the same plants should be applied with caution in physiological work.  相似文献   

16.
Soybean ( Glycine max cv. Clark) was grown at both ambient (ca 350 μmol mol−1) and elevated (ca 700 μmol mol−1) CO2 concentration at 5 growth temperatures (constant day/night temperatures of 20, 25, 30, 35 and 40°C) for 17–22 days after sowing to determine the interaction between temperature and CO2 concentration on photosynthesis (measured as A, the rate of CO2 assimilation per unit leaf area) at both the single leaf and whole plant level. Single leaves of soybean demonstrated increasingly greater stimulation of A at elevated CO2 as temperature increased from 25 to 35°C (i.e. optimal growth rates). At 40°C, primary leaves failed to develop and plants eventually died. In contrast, for both whole plant A and total biomass production, increasing temperature resulted in less stimulation by elevated CO2 concentration. For whole plants, increased CO2 stimulated leaf area more as growth temperature increased. Differences between the response of A to elevated CO2 for single leaves and whole plants may be related to increased self-shading experienced by whole plants at elevated CO2 as temperature increased. Results from the present study suggest that self-shading could limit the response of CO2 assimilation rate and the growth response of soybean plants if temperature and CO2 increase concurrently, and illustrate that light may be an important consideration in predicting the relative stimulation of photosynthesis by elevated CO2 at the whole plant level.  相似文献   

17.
Abstract: A continuous dual 13CO2 and 15NH415NO3 labelling experiment was undertaken to determine the effects of ambient (350μmol mol-1) or elevated (700μmol mol-1) atmospheric CO2 concentrations on C and N uptake and allocation within 3-year-old beech ( Fagus sylvatica L.) during leafing. After six weeks of growth, total carbon uptake was increased by 63 % (calculated on total C content) under elevated CO2 but the carbon partitioning was not altered. 56 % of the new carbon was found in the leaves. On a dry weight basis was the content of structural biomass in leaves 10 % lower and the lignin content remained unaffected under elevated as compared to ambient [CO2]. Under ambient [CO2] 37 %, and under elevated [CO2] 51 %, of the lignin C of the leaves derived from new assimilates. For both treatments, internal N pools provided more than 90 % of the nitrogen used for leaf-growth and the partitioning of nitrogen was not altered under elevated [CO2]. The C/N ratio was unaffected by elevated [CO2] at the whole plant level, but the C/N ratio of the new C and N uptake was increased by 32 % under elevated [CO2].  相似文献   

18.
Winter wheat (Triticum aestivum L. cv. Hereward) plants were grown for 35 d either at 350 μ mol mol–1 CO2 or at 650 μ mol mol–1 CO2. Lipid synthesis was studied in these plants by incubating the 5th leaf on the main stem with [1–14C]acetate. Increased CO2 concentrations did not significantly affect the total incorporation of radiolabel into lipids of whole leaf tissue, but altered the distribution for individual lipid classes. Most noticeable amongst acyl lipids was the reduction in labelling of diacylglycerol and a corresponding increase in the proportion of phosphatidylcholine labelling. In the basal regions, there were similar changes and, in addition, phosphatidylglycerol labelling was particularly increased following growth in an enriched CO2 atmosphere. The stimulation of labelling of the mitochondrial-specific lipid, diphosphatidylglycerol, prompted an examination of the mitochondrial population in wheat plants. Mitochondria were localized in intact wheat sections by immunolabelling for the mitochondrial-specific chaperonin probe. Growth in elevated CO2 doubled the number of mitochondria compared to growth in ambient CO2. Fatty acid labelling was also significantly influenced following growth at elevated CO2 concentrations. Most noticeable were the changes in 16C:18C ratios for the membrane lipids, phosphatidylcholine, phosphatidylglycerol and monogalactosyldiacylglycerol. These data imply a change in the apportioning of newly synthesized fatty acids between the 'eukaryotic' and 'prokaryotic' pathways of metabolism under elevated CO2.  相似文献   

19.
Abstract. Herbaceous C3 plants grown in elevated CO2 show increases in carbon assimilation and carbohydrate accumulation (particularly starch) within source leaves. Although changes in the partitioning of biomass between root and shoot occur, the proportion of this extra assimilate made available for sink growth is not known. Root:shoot ratios tend to increase for CO2-enriched herbaceous plants and decrease for CO2-enriched trees. Root:shoot ratios for cereals tend to remain constant. In contrast, elevated temperatures decrease carbohydrate accumulation within source and sink regions of a plant and decrease root:shoot ratios. Allometric analysis of at least two species showing changes in root: shoot ratios due to elevated CO2 show no alteration in the whole-plant partitioning of biomass. Little information is available for interactions between temperature and CO2. Cold-adapted plants show little response to elevated levels of CO2, with some species showing a decline in biomass accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and utilization for CO2-enriched plants and decrease carbohydrate accumulation within the leaf. Literature reports are discussed in relation to the hypothesis that sucrose is a major factor in the control of plant carbon partitioning. A model is presented in support.  相似文献   

20.
The limitation of symbiotic nitrogen fixation due to P deficiency restricts the development of a sustainable agriculture, particularly in Mediterrancan and tropical soils. Common bean genotypes, APN18, BAT271, PVA846, POT51, G2633 and G12168, were grown in an aerated N-free nutrient solution at low (72 μmol plant-1 week-1) and control P supplies (360 μmol plant-1 week-1). Nitrogenase activity was estimated by in situ measurements of acetylene reduction activity (ARA) in a flow-through system. During the assays, maximum values of ARA (peak ARA) were reached between 20 and 30 min after exposure to C2H2, depending on P treatment and growth stage. Thereafter, a decline in C2H4 evolution was observed. This decline was most pronounced in low-P plants and there was a significant genotypic effect. ARA per plant was decreased by P deficiency, mostly because nodulation was delayed and the number and mass of nodules were reduced. The ARA decrease during pod filling was also activated by P deficiency. ARA per g dry weight nodule was increased by P deficiency in G2633 and G12168, unchanged in APN18, BAT271 and POT51 and decreased in PVA846. Except for the climbing type IV G2633, total N at harvest for all P treatments was correlated with the cumulative value of peak ARA and with peak ARA at early pod-filling which was the highest peak ARA throughout the growth cycle of type III bushy genotypes. We conclude that if phenology and growth habit are carefully considered, peak ARA is a reliable screen of genotypes for N2 fixation tolerance to P deficiency. Selection of lines with early nodulation under P deficiency is also advisable, and the effect of P deficiency on the nodule functioning needs to be considered.  相似文献   

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