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1.
Extracellular Matrix in Early Stages of Direct Somatic Embryogenesis in Leaves of Drosera spathulata
The growth and water relations of Paulownia fortunei in photoautotrophic cultures (nutrient medium lacking sucrose and growth regulator) with CO2 enrichment (PWAH) or without CO2 enrichment (PWAL) were compared with those in photomixotrophic shoot (PWC; 30 g dm−3 sucrose and 0.3 mg dm−3 N6-benzyladenine) and root cultures (PWR; 0.3 mg dm−3 indole-3-butyric acid). The photoautotrophic and photomixotrophic cultures were incubated under photosynthetic photon flux
125 and 60 μmol m−2 s−1, respectively. 100 % sprouting and significantly higher number of shoots (1.6) were obtained with PWAH as compared to PWAL
and PWC. PWAH and PWAL stimulated spontaneous rooting from the cut end of axillary shoots. In PWAH, 84 % of shoots rooted
with an average of 5.9 roots per shoot and 4.0 cm of root length in 21 d. Rooting of photomixotrophic shoot cultures were
stimulated by an auxin treatment. In this case, 98.3 % of shoots were rooted with an average of 4.6 roots per shoot and 1.9
cm length. A microscopic observation on leaf abaxial surface prints from photomixotrophic shoot and root cultures showed widely
open (6 – 8 μm) spherical stomata (12 – 14 μm) and from photoautotrophic cultures elliptical stomata (10 – 12 μm) with narrow
openings (3 – 4 μm). Leaves from photomixo-trophic cultures had higher stomatal index as compared to photoautotrophic cultures.
The rate of moisture loss from detached leaves was not varying significantly in different cultures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
N2O, CH4 and CO2 emissions from seasonal tropical rainforests and a rubber plantation in Southwest China 总被引:2,自引:1,他引:1
Christian Werner Xunhua Zheng Janwei Tang Baohua Xie Chunyan Liu Ralf Kiese Klaus Butterbach-Bahl 《Plant and Soil》2006,289(1-2):335-353
The main focus of this study was to evaluate the effects of soil moisture and temperature on temporal variation of N2O, CO2 and CH4 soil-atmosphere exchange at a primary seasonal tropical rainforest (PF) site in Southwest China and to compare these fluxes with fluxes from a secondary forest (SF) and a rubber plantation (RP) site. Agroforestry systems, such as rubber plantations, are increasingly replacing primary and secondary forest systems in tropical Southwest China and thus effect the N2O emission in these regions on a landscape level. The mean N2O emission at site PF was 6.0 ± 0.1 SE μg N m−2 h−1. Fluxes of N2O increased from <5 μg N m−2 h−1 during dry season conditions to up to 24.5 μg N m−2 h−1 with re-wetting of the soil by the onset of first rainfall events. Comparable fluxes of N2O were measured in the SF and RP sites, where mean N2O emissions were 7.3 ± 0.7 SE μg N m−2 h−1 and 4.1 ± 0.5 SE μg N m−2 h−1, respectively. The dependency of N2O fluxes on soil moisture levels was demonstrated in a watering experiment, however, artificial rainfall only influenced the timing of N2O emission peaks, not the total amount of N2O emitted. For all sites, significant positive correlations existed between N2O emissions and both soil moisture and soil temperature. Mean CH4 uptake rates were highest at the PF site (−29.5 ± 0.3 SE μg C m−2 h−1), slightly lower at the SF site (−25.6 ± 1.3 SE μg C m−2 h−1) and lowest for the RP site (−5.7 ± 0.5 SE μg C m−2 h−1). At all sites, CH4 uptake rates were negatively correlated with soil moisture, which was also reflected in the lower uptake rates measured in the watering experiment. In contrast to N2O emissions, CH4 uptake did not significantly correlate with soil temperature at the SF and RP sites, and only weakly correlated at the PF site. Over the 2 month measurement period, CO2 emissions at the PF site increased significantly from 50 mg C m−2 h−1 up to 100 mg C m−2 h−1 (mean value 68.8 ± 0.8 SE mg C m−2 h−1), whereas CO2 emissions at the SF and RP site where quite stable and varied only slightly around mean values of 38.0 ± 1.8 SE mg C m−2 h−1 (SF) and 34.9 ± 1.1 SE mg C m−2 h−1 (RP). A dependency of soil CO2 emissions on changes in soil water content could be demonstrated for all sites, thus, the watering experiment revealed significantly higher CO2 emissions as compared to control chambers. Correlation of CO2 emissions with soil temperature was significant at the PF site, but weak at the SF and not evident at the RP site. Even though we demonstrated that N and C trace gas fluxes significantly varied on subdaily and daily scales, weekly measurements would be sufficient if only the sink/ source strength of non-managed tropical forest sites needs to be identified. 相似文献
3.
Jordi Urmeneta Óscar Alcoba Efrén Razquín Elena Tarroja Antoni Navarrete Ricardo Guerrero 《Current microbiology》1998,37(3):151-155
Photosynthetic and respiratory activities at low light intensities (300 μE m−2 s−1) in the microbial mats of the Ebro Delta were measured by the oxygen exchange method in the laboratory. The response to H2S concentration, a significant factor in the dynamics of that ecosystem, was assessed. Total photosynthesis reached 23.78–28.17
μg O2 cm−2 h−1. Photosynthetic activity was not significantly different at the two temperatures tested. Respiratory activity reached a consumption
of 6.95–8.56 μg O2 cm−2 h−1 at 25°C and 11.42–11.70 μg O2 cm−2 h−1 at 35°C. The Q10 value for respiration was 1.37–1.64. Oxygen production in Microcoleus chthonoplastes, the most abundant cyanobacterium in those microbial mats, was highly resistant to sulfide inhibition. Concentrations less
than 0.02 mM sulfide did not affect the rate of photosynthesis. Concentrations up to 0.1 mM sulfide caused different degrees
of partially reversible inhibition, with a maximum of 67% at 0.78 mM sulfide. Primary production (g C assimilated/m2/year) in those microbial mats was also assessed and compared with data from other ecosystems.
Received: 24 October 1997 / Accepted: 18 December 1997 相似文献
4.
Diel variation in urea decomposing activity in the euphotic zone of brackish Lake Nakaumi 总被引:1,自引:0,他引:1
Diel variations in urea decomposing activity in the euphotic zone of brackish Lake Nakaumi were measured under fixed light
intensity. The decomposition rate of urea was 17 to 44 μ mol urea m−3 h−1 in the light and 10 to 27 μ mol urea m−3 h−1 in the dark. Higher decomposition rates were obtained in the upper euphotic zone. A clear diel periodicity in the urea decomposition
rate was observed, with high rates from 1200 to 1600 and low rates from 0000 to 0400. Chlorophyll a specific decomposing activity ranged from 12 to 21 μg urea C mg chl.a
−1 h−1 in the light and 7 to 13 μg urea C mg chl.a
−1 h−1 in the dark. In the light, high values were obtained from 1600 to 2000 and low values from 0400 to 0800. The diel change
in specific decomposing activity exhibited a similar pattern to that of the photosynthetic assimilation number, following
the diel change in photosynthetic activity.
Received: March 10, 1999 / Accepted: October 22, 1999 相似文献
5.
The effects of elevated [CO2] (700 μl l−1 [CO2]) and temperature increase (+3 °C) on carbon accumulation in a grassland soil were studied at two N-fertiliser supplies (160
and 530 kgN ha−1 year−1) in a long-term experiment (2.5 years) on well established ryegrass swards (Lolium perenne L.,) supplied with the same amounts
of irrigation water. For all experimental treatments, the C:N ratio of the top soil organic matter fractions increased with
their particle size. Elevated CO2 concentration increased the C:N ratios of the below-ground phytomass and of the macro-organic matter. A supplemental fertiliser
N or a 3 °C increase in elevated [CO2] reduced it. At the last sampling date, elevated [CO2] did not affect the C:N ratio of the soil organic matter fractions, but increased significantly the accumulation of roots
and of macro-organic matter above 200 μm (MOM). An increased N-fertiliser supply stimulated the accumulation of the non harvested
plant phytomass and of the OM between 2 and 50 μm, without positive effect on the macro-organic matter >200 μm. Elevated [CO22] increased C accumulation in the OM fractions above 50 μm by +2.1 tC ha−1, on average, whereas increasing the fertiliser N supply led to an average supplemental accumulation of +0.8 tC ha−1. There was no significant effect of a 3 °C temperature increase under elevated [CO2] on C accumulation in the OM fractions above 50 μm.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
The ability of photoautotrophic picoplankton Synechococcus to degrade urea was examined in the euphotic zone of Lake Biwa. Samples were divided into pico (0.2–2.0 μm) and larger (>2.0
μm) size fractions by filtration. The rates of urea degradation (the sum of the rates of incorporation of carbon into phytoplankton
cells and of liberation of CO2 into water) measured by radiocarbon urea were 8 and 17 μmol urea m−3 day−1 in June and July, respectively, for the picophytoplankton in the surface water, and 196 and 96 μmol urea m−3 day−1, respectively for the larger phytoplankton. The rates decreased with depth, somewhat similar to the vertical profiles of
the photosynthetic rate. The urea degradation rates were obviously high under light conditions. In daylight, urea was degraded
into two phases, carbon incorporation and CO2 liberation, whereas in the dark it was degraded only into the CO2 liberation phase. The contribution of picophytoplankton to total phytoplankton in urea degradation was high in the subsurface
to lower euphotic layer. Urea degradation activity was higher in the picophytoplankton fraction than in the larger phytoplankton
fraction. Shorter residence times of urea were obtained in the upper euphotic zone. The contribution of picophytoplankton
to urea cycling was 4% to 35%. The present results suggest that the picophytoplankton Synechococcus is able to degrade urea and effectively makes use of regenerated urea as a nitrogen source in the euphotic layer, and that
picophytoplankton play an important role in the biogeochemical nitrogen cycle in Lake Biwa.
Received: June 25, 1998 / Accepted: February 10, 1999 相似文献
7.
Batch experiments were conducted to evaluate the biodegradation rates of limonene, α-pinene, γ-terpinene, terpinolene and
α-terpineol at 23 °C under aerobic conditions. Biodegradation was demonstrated by the depletion of monoterpene mass, CO2 production and a corresponding increase in biomass. Monoterpene degradation in liquid cultures devoid of soil followed Monod
kinetics. The maximum specific growth rate (μmax) was 0.02 h−1 and 0.06 h−1 and the half-velocity constant (K
s ) varied from 32 mg/l to 3 mg/l for the limonene and α-terpineol respectively. The recovery of monoterpenes by solvent extraction
from autoclaved and azide-amended soil-slurry samples decreased over time and ranged from 69% to 73% for 120 h of incubation
period. Although a significant fraction of monoterpene hydrocarbon could not be extracted, mineralization of these compounds
in the soil-slurry systems took place, as shown by CO2 production. The soil-normalized degradation rates for the hydrocarbon monoterpenes ranged from 0.6 μg g−1 h−1 to 2.1 μg g−1 h−1. A kinetic model – which combined monoterpene biodegradation in the liquid phase and net desorption – was developed and applied
to data obtained from soil-slurry assays.
Received: 10 September 1996 / Received revision: 16 December 1996 / Accepted: 10 January 1997 相似文献
8.
CO2 and N-fertilization effects on fine-root length, production, and mortality: a 4-year ponderosa pine study 总被引:1,自引:0,他引:1
We conducted a 4-year study of juvenile Pinus ponderosa fine root (≤2 mm) responses to atmospheric CO2 and N-fertilization. Seedlings were grown in open-top chambers at three CO2 levels (ambient, ambient+175 μmol/mol, ambient+350 μmol/mol) and three N-fertilization levels (0, 10, 20 g m−2 year−1). Length and width of individual roots were measured from minirhizotron video images bimonthly over 4 years starting when the seedlings were 1.5 years old. Neither CO2 nor N-fertilization treatments affected the seasonal patterns of root production or mortality. Yearly values of fine-root length standing crop (m m−2), production (m m−2 year−1), and mortality (m m−2 year−1) were consistently higher in elevated CO2 treatments throughout the study, except for mortality in the first year; however, the only statistically significant CO2 effects were in the fine-root length standing crop (m m−2) in the second and third years, and production and mortality (m m−2 year−1) in the third year. Higher mortality (m m−2 year−1) in elevated CO2 was due to greater standing crop rather than shorter life span, as fine roots lived longer in elevated CO2. No significant N effects were noted for annual cumulative production, cumulative mortality, or mean standing crop. N availability did not significantly affect responses of fine-root standing crop, production, or mortality to elevated CO2. Multi-year studies at all life stages of trees are important to characterize belowground responses to factors such as atmospheric CO2 and N-fertilization. This study showed the potential for juvenile ponderosa pine to increase fine-root C pools and C fluxes through root mortality in response to elevated CO2. 相似文献
9.
Subsurface CO<Subscript>2</Subscript> Dynamics in Temperate Beech and Spruce Forest Stands 总被引:1,自引:0,他引:1
Rates of soil respiration (CO2 effluxes), subsurface pore gas CO2/O2 concentrations, soil temperature and soil water content were measured for 15 months in two temperate and contrasting Danish
forest ecosystems: beech (Fagus sylvatica L.) and Norway spruce (Picea abies [L.] Karst.). Soil CO2 effluxes showed a distinct seasonal trend in the range of 0.48–3.3 μmol CO2 m−2 s−1 for beech and 0.50–2.92 μmol CO2 m−2 s−1 for spruce and were well-correlated with near-surface soil temperatures. The soil organic C-stock (upper 1 m including the
O-horizon) was higher in the spruce stand (184±23 Mg C ha−1) compared to the beech stand (93±19 Mg C ha−1) and resulted in a faster turnover time as calculated by mass/flux in soil beneath the beech stand (28 years) compared to
spruce stand (60 years). Observed soil CO2 concentrations and effluxes were simulated using a Fickian diffusion-reaction model based on vertical CO2 production rates and soil diffusivity. Temporal trends were simulated on the basis of observed trends in the distribution
of soil water, temperature, and live roots as well as temperature and water content sensitivity functions. These functions
were established based on controlled laboratory incubation experiments. The model was successfully validated against observed
soil CO2 effluxes and concentrations and revealed that temporal trends generally could be linked to variations in subsurface CO2 production rates and diffusion over time and with depths. However, periods with exceptionally high CO2 effluxes (> 20 μmol CO2 m−2 s−1) were noted in March 2000 in relation to drying after heavy rain and after the removal of snow from collars. Both cases were
considered non-steady state and could not be simulated. 相似文献
10.
Automated feeding strategies for high-cell-density fed-batch cultivation of Pseudomonas putida KT2440 总被引:1,自引:0,他引:1
Four automatic substrate feeding strategies were developed and investigated in this study to obtain rapid, repeatable, and reliable high cell densities of Pseudomonas putida KT2440 from glucose. Growth yield data of the key nutrients, Y
X/Glucose, Y
X/NH4, Y
X/PO4, Y
X/Mg, and Y
CO2/Glucose, were determined to be 0.41, 5.44, 13.70, 236, and 0.65 g g−1, respectively. Although standard exponential feeding strategy worked well when the predetermined μ was set at 0.25 h−1, an exponential glucose feeding strategy with online μ
max estimation resulted in a higher average biomass productivity (3.4 vs 2.8 g l−1 h−1). A CO2 production rate based pulse glucose feeding strategy also resulted in good overall productivity (3.0 g l−1 h−1) and can be used as an alternative to pH-stat or DO-stat feeding. A cumulative CO2 production based continuous feed with real-time cumulative glucose consumption estimation resulted in much higher biomass productivity (4.3 g l−1 h−1) and appears to be an excellent and reliable approach to fully automating high-cell-density fed-batch cultivation of P. putida. 相似文献
11.
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
12.
N. T. Thanh H. N. Murthy D. M. Pandey K. W. Yu E. J. Hahn K. Y. Paek 《Biologia Plantarum》2006,50(4):752-754
The effects of carbon dioxide supply within the range of 1–5 % (along with purified air), on cell culture of Panax ginseng were investigated in a balloon type bubble bioreactor containing 4 dm3 of Murashige and Skoog (MS) medium supplemented with 7.0 mg dm−3 indolebutyric acid, 0.5 mg dm−3 kinetin and 30 g dm−3 sucrose. A 1 % CO2 supply was found beneficial for the production of cell mass; however, increasing CO2 concentration to 2.5 and 5 % decreased the biomass accumulation. CO2 enrichment was not beneficial for saponin production and 1, 2.5, and 5 % CO2 supply resulted in decrease in saponin accumulation up to 11.6, 19.5, and 50.6 %, respectively. 相似文献
13.
Soil respiration of Alaskan tundra at elevated atmospheric carbon dioxide concentrations 总被引:3,自引:0,他引:3
Summary CO2 efflux from tussock tundra in Alaska that had been exposed to elevated CO2 for 2.5 growing seasons was measured to assess the effect of long- and short-term CO2 enrichment on soil respiration. Long-term treatments were: 348, 514, and 683 μll−1 CO2 and 680 μll−1 CO2+4°C above ambient. Measurements were made at 5 CO2 concentrations between 87 and 680 μll−1 CO2. Neither long- or short-term CO2 enrichment significantly affected soil CO2 efflux. Tundra developed at elevated temperature and 680 μll−1 CO2 had slightly higher, but not statistically different, mean respiration rates compared to untreated tundra and to tundra under
CO2 control alone. 相似文献
14.
Corynebacterium acetoacidophilum RYU3161 was cultivated in al-histidine-limited fed-batch culture. To investigate the effect of cell growth on thel-proline production, 5l fed-batch culture was performed using an exponential feeding rate to obtain the specific growth rates (μ) of 0.04, 0.06,
0.08, and 0.1 h−1. The results show that the highest production ofl-proline was obtained at μ=0.04 h−1. The specificl-proline production rate (Qp) increased proportionally as a function of the specific growth rate, but decreased after it revealed the maximum value at
μ=0.08 h−1. Thus, the highest productivity ofl-proline was 1.66 g L−1 h−1 at μ=0.08 h−1. The results show that the production of L-proline inC. acetoacidophilum RYU3161 has mixed growth-associated characteristics. 相似文献
15.
The Impact of Nitrogen Placement and Tillage on NO, N2O, CH4 and CO2 Fluxes from a Clay Loam Soil 总被引:4,自引:0,他引:4
Xuejun J. Liu Arvin R. Mosier Ardell D. Halvorson Fusuo S. Zhang 《Plant and Soil》2006,280(1-2):177-188
To evaluate the impact of N placement depth and no-till (NT) practice on the emissions of NO, N2O, CH4 and CO2 from soils, we conducted two N placement experiments in a long-term tillage experiment site in northeastern Colorado in 2004.
Trace gas flux measurements were made 2–3 times per week, in zero-N fertilizer plots that were cropped continuously to corn
(Zea mays L.) under conventional-till (CT) and NT. Three N placement depths, replicated four times (5, 10 and 15 cm in Exp. 1 and 0,
5 and 10 cm in Exp. 2, respectively) were used. Liquid urea–ammonium nitrate (UAN, 224 kg N ha−1) was injected to the desired depth in the CT- or NT-soils in each experiment. Mean flux rates of NO, N2O, CH4 and CO2 ranged from 3.9 to 5.2 μg N m−2 h−1, 60.5 to 92.4 μg N m−2 h−1, −0.8 to 0.5 μg C m−2 h−1, and 42.1 to 81.7 mg C m−2 h−1 in both experiments, respectively. Deep N placement (10 and 15 cm) resulted in lower NO and N2O emissions compared with shallow N placement (0 and 5 cm) while CH4 and CO2 emissions were not affected by N placement in either experiment. Compared with N placement at 5 cm, for instance, averaged
N2O emissions from N placement at 10 cm were reduced by more than 50% in both experiments. Generally, NT decreased NO emission
and CH4 oxidation but increased N2O emissions compared with CT irrespective of N placement depths. Total net global warming potential (GWP) for N2O, CH4 and CO2 was reduced by deep N placement only in Exp. 1 but was increased by NT in both experiments. The study results suggest that
deep N placement (e.g., 10 cm) will be an effective option for reducing N oxide emissions and GWP from both fertilized CT-
and NT-soils. 相似文献
16.
Q. Hu N. Kurano M. Kawachi I. Iwasaki S. Miyachi 《Applied microbiology and biotechnology》1998,49(6):655-662
To test the feasibility of CO2 remediation by microalgal photosynthesis, a modified type of flat-plate photobioreactor [Hu et al. (1996) Biotechnol Bioeng 51:51–60] has been designed for cultivation of a high-CO2-tolerant unicellular green alga Chlorococcum littorale. The modified reactor has a narrow light path in which intensive turbulent flow is provided by streaming compressed air through
perforated tubing into the culture suspension. The length of the reactor light path was optimized for the productivity of
biomass. The interrelationship between cell density and productivity, as affected by incident light intensity, was quantitatively
assessed. Cellular ultrastructural and biochemical changes in response to ultrahigh cell density were investigated. The potential
of biomass production under extremely high CO2 concentrations was also evaluated. By growing C. littorale cells in this reactor, a CO2 fixation rate of 16.7 g CO2 l−1 24 h−1 (or 200.4 g CO2 m−2 24 h−1) could readily be sustained at a light intensity of 2000 μmol m−2 s−1 at 25 °C, and an ultrahigh cell density of well over 80 g l−1 could be maintained by daily replacing the culture medium.
Received: 20 October 1997 / Received revision: 19 December 1997 / Accepted: 24 January 1998 相似文献
17.
Masmoudi Raja Rival Alain Nato Aimé Lavergne Danièle Drira Nourredine Ducreux Georges 《Plant Cell, Tissue and Organ Culture》1999,57(2):139-143
While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm
(Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate
carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic
cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active
isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic
(NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development
of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7
to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased
from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1
TSP
) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against
PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
A transect of ten profiles was laid out in 20 m intervals on a tidal sand flat approximately 100 m from the east shore of
Sylt until the next tideway was reached. Sediment samples were taken from 0–2 cm depth (oxic layer) and 2–4 cm depth (anoxic
layer). The average content of organic carbon (C) was 2.41 mg g−1 in the oxic layer and 1.86 mg g−1 in the anoxic layer. The organic C content correlated positively with non-biomass C, 0.5M K2SO4 extractable C, total nitrogen (N), cation exchange capacity (CEC), and the textural classes <200 μm, and negatively correlated
with the coarse sand fraction. The average total C:N ratio was 7.0 in the oxic layer and 6.7 in the anoxic layer, indicating
that the C input comes entirely from the microflora. CHCl3-labile C was measured by the fumigation-extraction method and was converted to microbial biomass C (values in brackets).
The average content of CHCl3-labile C was 407 μg g−1 (903 μg g−1) in the oxic layer and 214 μg g−1 (476 μg g−1) in the anoxic layer. CHCl3-labile C did not correlate with CEC and the textural classes <200 μm, indicating that conditions other than the physical
environment determine this fraction (C input, grazing). 相似文献
19.
Summary
In vitro banana (Musa spp.) shoots were cultured under photomixotrophic (30 gl−1 sucrose and 0.2 h−1 number of air exchanges of culture vessels) and photoautotrophic (0 gl−1 sucrose and 3.9 h−1 number of air exchanges) conditions for 28 d in 370 cm3 Magenta boxes (GA7-type) containing 70 ml of half-strength Murashige and Skoog (MS) medium with 22.2 μM N6-benzyladenine (BA). The effects of varying CO2 concentration (475 or 1340 μmol mol−1) and light intensity (photosynthetic photon flux (PPF) of 100 or 200 μmol m−2 s−1) were investigated. Fresh and dry weights of banana shoots grown photomixotrophically were significantly greater on day 28
than those grown photoautotrophically. Photoautorophic shoots had a larger number of unfolded leaves and greater leaf area
than photomixotrophic plants by days 14 and 28, regardless of CO2 concentration. The shoot fresh and dry weights on day 14 in photoautotrophic conditions were significantly greater at PPF
of 200 μmol m−2 s−1 than at 100 μmol m−2 s−1. The increase in net photosynthetic rate of photoautotrophic banana shoots was significant compared with photomixotrophic
shoots. The multiplication ratio of in vitro banana shoots grown photoautotrophically in a 28-d culture period was the greatest at 100 μmol m−2 s−1 PPF and 475 μmol mol−1 CO2. 相似文献
20.
The effects of elevated CO2 (ambient, +175, and +350 μl l−1) and nitrogen fertilization (0, 100, and 200 kg N ha−1 yr−1 as ammonium sulfate) on C and N accumulations in biomass and soils planted with ponderosa pine (Pinus ponderosa Laws) over a 6-year study period are reported. Both nitrogen fertilization and elevated CO2 caused increases in C and N contents of vegetation over the study period. The pattern of responses varied over time. Responses
to CO2 decreased in the +175 μl l−1 and increased in the +350 μl l−1 after the first year, whereas responses to N decreased after the first year and became non-significant by year six. Foliar
N concentrations were lower and tree C:N ratios were higher with elevated CO2 in the early years, but this was offset by the increases in biomass, resulting in substantial increases in N uptake with
elevated CO2. Nitrogen budget estimates showed that the major source of the N for unfertilized trees, with or without elevated CO2, was likely the soil organic N pool. There were no effects of elevated CO2 on soil C, but a significant decrease in soil N and an increase in soil C:N ratio in year six. Nitrogen fertilization had
no significant effect on tree C:N ratios, foliar N concentrations, soil C content, soil N content, or soil C:N ratios. There
were no significant interactions between CO2 and N treatments, indicating that N fertilization had no effect on responses to CO2 and that CO2 treatments had no effect on responses to N fertilization. These results illustrate the importance of long-term studies involving
more than one level of treatment to assess the effects of elevated CO2. 相似文献