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1.
CO2 exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO2 concentration. The species had low CO2 exchange rates (maximum net photosynthesis: c. 0.45 μmol CO2 m−2 s−1; maximum dark respiration: c. 0.3 μmol CO2 m−2 s−1) and a very low light compensation point (7 μmol photons m−2 s−1 at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only
after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under
different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant.
Low photosynthetically active radiation (normally below 40 μmol photons m−2 s−1), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO2 assimilation were often measured in the absence of condensation phenomena.
Received: 22 September 1996 / Accepted: 26 April 1997 相似文献
2.
Chloroplasts or chromoplasts were purified from sweet-pepper (Capsicum annuum L. cv. Yolo Wonder) fruits and analysed with respect to their enzymic equipment, the transport properties across the envelope
membrane, and for the presence of a functional oxidative pentose-phosphate pathway (OPPP). It was demonstrated that both types
of plastid contain enzyme activities that allow glycolysis and OPPP. During the developmental conversion from chloroplasts
to chromoplasts the activities of enzymes catalysing potentially rate-limiting reactions in glycolysis increased considerably.
Most enzyme activities involved in the plastidic OPPP stayed constant or decreased during ripening, but transaldolase activity
increased by more than 500%. To analyse whether pepper fruit chromoplasts are able to use exogenously supplied carbohydrates
for the OPPP we measured the rate of 14CO2 release after application of radioactively labelled precursors. Isolated pepper fruit chromoplasts used exogenously supplied
[U14C]glucose- 6-phosphate (Glc6P) as a precursor for the OPPP. The metabolic flux through this pathway was stimulated by the
presence of additional compounds which require reducing equivalents for further conversion, e.g. nitrite, or 2-oxoglutarate
plus glutamine. The [14C]Glc6P-driven OPPP in isolated chromoplasts exhibited saturation with rising concentrations of Glc6P, reaching highest rates
at an external concentration of about 2 mM. Exogenously given [U14C]glucose 1-phosphate (Glc1P)′ did not lead to a release of 14CO2, indicating that this hexose phosphate is not taken up into the intact plastid. Using a proteoliposome system in which the
envelope membrane proteins from sweet-pepper chromoplasts were functionally reconstituted we demonstrated that Glc6P is transported
in counter-exchange with inorganic phosphate (Pi) or other phosphorylated intermediates. The Glc6P was taken up into proteoliposomes with an apparent K
m of 0.34 mM. Surprisingly, in contrast to tomato fruit plastids, isolated chromoplasts from sweet-pepper fruits do not possess
a phosphate translocator allowing the uptake of Glc1P. Rising exogenous concentrations of dihydroxyacetone phosphate strongly
inhibited the metabolic flux through the OPPP. This observation is discussed with respect to the presence of two phosphate
translocator proteins in the envelope of sweet-pepper chromoplasts and with respect to possible metabolic changes occurring
in heterotrophic tissues during development.
Received: 24 April 1997 / Accepted: 16 June 1997 相似文献
3.
The effects of elevated CO2 concentrations on stomatal movement, anion- and K+-channel activities were examined in guard cells from epidermal strips of Vicia faba. Membrane voltage was measured using intracellular, double-barrelled microelectrodes and ion-channel currents were recorded
under voltage clamp during exposure to media equilibrated with ambient (350 μl · l−1), 1000 μl · l−1 and 10 000 μl · l−1 CO2 in 20% O2 and 80% N2. The addition of 1000 μl · l−1 CO2 to the bathing solution caused stomata to close with a halftime of approx. 40 min, and with 10 000 μl · l−1 CO2 closure occurred with a similar time course. Under voltage clamp, exposure to 1000 μl · l−1 and 10 000 μl · l−1 CO2 resulted in a rapid increase (mean, 1.5 ± 0.2-fold, n = 8; range 1.3- to 2.5-fold) in the magnitude of current carried by outward-rectifying K+ channels (IK,out). The effect of CO2 on IK,out was essentially complete within 30 s and was independent of clamp voltage, but was associated with 25–40% (mean, 30 ± 4%)
decrease in the halftime for current activation. Exposure to CO2 also resulted in a four-fold increase in background current near the free-running membrane voltage, recorded as the instantaneous
current at the start of depolarising and hyperpolarising voltage steps, and a decrease in the magnitude of current carried
by inward-rectifying K+ channels (IK,in). The effect of CO2 on IK,in was generally slower than on IK,out; it was allied with a transient acceleration of its activation kinetics during the first 60–120 s of treatment; and it was
associated with a negative shift in the voltage-sensitivity of gating over a period of 3–5 min. Measurements carried out to
isolate the background currents attributable to anion channels (ICl), using tetraethylammonium chloride and CsCl, showed that CO2 also stimulated ICl and dramatically altered its relaxation kinetics. Within the timeframe of CO2 action at the membrane, no significant effect was observed on cytosolic pH, measured using the fluorescent dye 2′,7′-bis-(2-carboxyethyl)-5,6-carboxyflourescein
(BCECF) and ratio fluorescence microphotometry. These results are broadly consistent with the pattern of guard-cell response
to abscisic acid, and indicate that guard cells control both anion and K+ channels to achieve net solute loss in CO2. By contrast with the effects of abscisic acid, however, the data indicate that CO2 action is not mediated through changes in cytosolic pH and thereby implicate new and, as yet, unidentified pathway(s) for
channel regulation in the guard cells.
Received: 8 January 1997 / Accepted: 28 February 1997 相似文献
4.
Greg J. Wilson Andrew D. Walshe Mark R. Fisher 《European journal of applied physiology and occupational physiology》1997,75(5):455-461
The aims of the present study were: (1) to assess aerobic metabolism in paraplegic (P) athletes (spinal lesion level, T4–L3)
by means of peak oxygen uptake (V˙O2peak) and ventilatory threshold (VT), and (2) to determine the nature of exercise limitation in these athletes by means of cardioventilatory
responses at peak exercise. Eight P athletes underwent conventional spirographic measurements and then performed an incremental
wheelchair exercise on an adapted treadmill. Ventilatory data were collected every minute using an automated metabolic system:
ventilation (l · min−1), oxygen uptake (V˙O2, l · min−1, ml · min−1 · kg−1), carbon dioxide production (V˙CO2, ml · min−1), respiratory exchange ratio, breathing frequency and tidal volume. Heart rate (HR, beats · min−1) was collected with the aid of a standard electrocardiogram. V˙O2peak was determined using conventional criteria. VT was determined by the breakpoint in the V˙CO2−V˙O2 relationship, and is expressed as the absolute VT (V˙O2, ml · min−1 · kg−1) and relative VT (percentage of V˙O2peak). Spirometric values and cardioventilatory responses at rest and at peak exercise allowed the measurement of ventilatory
reserve (VR), heart rate reserve (HRr), heart rate response (HRR), and O2 pulse (O2 P). Results showed a V˙O2peak value of 40.6 (2.5) ml · min−1 · kg−1, an absolute VT detected at 23.1 (1.5) ml · min−1 · kg−1
V˙O2 and a relative VT at 56.4 (2.2)% V˙O2peak. HRr [15.8 (3.2) beats · min−1], HRR [48.6 (4.3) beat · l−1], and O2 P [0.23 (0.02) ml · kg−1 · beat−1] were normal, whereas VR at peak exercise [42.7 (2.4)%] was increased. As wheelchair exercise excluded the use of an able-bodied
(AB) control group, we compared our V˙O2peak and VT results with those for other P subjects and AB controls reported in the literature, and we compared our cardioventilatory
responses with those for respiratory and cardiac patients. The low V˙O2peak values obtained compared with subject values obtained during an arm-crank exercise may be due to a reduced active muscle
mass. Absolute VT was somewhat comparable to that of AB subjects, mainly due to the similar muscle mass involved in wheelchair
and arm-crank exercise by P and AB subjects, respectively. The increased VR, as reported in patients with chronic heart failure,
suggested that P athletes exhibited cardiac limitation at peak exercise, and this contributed to the lower V˙O2peak measured in these subjects.
Accepted: 22 April 1997 相似文献
5.
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
6.
Microclimatic parameters influencing nitrogen fixation in the phyllosphere in a Costa Rican premontane rain forest 总被引:1,自引:0,他引:1
Elke Freiberg 《Oecologia》1998,117(1-2):9-18
The acetylene reduction method was used to measure nitrogen fixation in the phyllosphere of attached leaves of different
phorophytes under natural conditions in a premontane rain forest in Costa Rica. Maximum rates of nitrogen fixation (26 ng N · cm−2 leaf area · h−1) – mainly due to the activity of two species of Scytonema (Cyanobacteria) – were measured in the rainy season in bright sunlight. Rates of nitrogen fixation were correlated with the
leaf area covered by Scytonema. In periods without precipitation the fixation activity decreased to zero within 2–3 days. As long as the epiphylls were sufficiently
supplied with water, other microclimatic factors like temperature and light intensity also influenced nitrogen fixation rates,
but to a lesser extent. Relative humidity and species of phorophyte showed no direct influence. It was concluded that the
most important factor for nitrogen fixation in the phyllosphere was the availability of liquid water. Linking these results
to meteorological data, the input of nitrogen by biological nitrogen fixation in the phyllosphere in the investigation area
was estimated to be as much as 1.6 ± 0.8 kg N · ha−1 · year−1 per unit of leaf area index (LAI). For an LAI of 2 for the understory the nitrogen input would vary between 2 and 5 kg N ·
ha−1 · year−1. This work also demonstrates the importance of detailed knowledge of variation in microclimate throughout the year as a basis
for extrapolation of the annual nitrogen input.
Received: 21 December 1997 / Accepted: 14 June 1998 相似文献
7.
Ronald Heus Alexander H. Wertheim George Havenith 《European journal of applied physiology and occupational physiology》1998,77(4):388-394
The assumption that working on board ship is more strenuous than comparable work ashore was investigated in this study. Various
physiological parameters (V˙O2, V˙CO2, V˙
E and HR) have been measured to determine the energy expenditure of subjects walking slowly on a moving platform (ship motion
simulator). Twelve subjects (eight men and four women) walked either freely on the floor or on a treadmill at a speed of 1 m · s−1. Platform motion was either in a heave, pitch or roll mode. These three conditions were compared with a control condition
in which the platform remained stationary. The results showed that during pitch and roll movements of the platform, the energy
expenditure for the same walking task was about 30% higher than under the stationary control condition (3.6 J · kg−1 · m−1 vs 2.5 J · kg−1 · m−1, P < 0.05) for both walking on a treadmill and free walking. The heart rate data supported the higher energy expenditure results
with an elevation of the heart rate (112 beats · min−1 vs 103 beats · min−1, P < 0.05). The heave condition did not differ significantly from the stationary control condition. Pitch and roll were not
significantly different from each other. During all experimental conditions free walking resulted in a higher energy cost
of walking than treadmill walking (3.5 J · kg−1 · m−1 vs 2.7 J · kg−1 · m−1, P < 0.05) at the same average speed. The results of this experiment were interpreted as indicating that the muscular effort,
needed for maintaining balance when walking on a pitching or rolling platform, resulted in a significantly higher work load
than similar walking on a stable or a heaving floor, independent of the mode of walking. These results explain in part the
increased fatigue observed when a task is performed on a moving platform.
Accepted: 3 October 1997 相似文献
8.
Savvas P. Tokmakidis Luc A. Léger Theophilos C. Pilianidis 《European journal of applied physiology and occupational physiology》1998,77(4):333-342
The purpose of this study was to compare various methods and criteria used to identify the anaerobic threshold (AT), and
to correlate the AT obtained with each other and with running performance. Furthermore, a number of additional points throughout
the entire range of lactate concentrations [La−] were obtained and correlated with performance. A group of 19 runners [mean age 33.7 (SD 9.6) years, height 173 (SD 6.3)
cm, body mass 68.3 (SD 5.4) kg, maximal O2 uptake (V˙O2
max
) 55.2 (SD 5.9) ml · kg−1 · min−1] performed a maximal multistage treadmill test (1 km · h−1 every 3.5 min) with blood sampling at the end of each stage while running. All AT points selected (visual [La−], 4 mmol · l−1 [La−], 1 mmol · l−1 above baseline, log-log breakpoint, and 45° tangent to the exponential regression) were highly correlated one with another
and with performance (r > 0.90) even when there were many differences among the AT (P < 0.05). The additional points (ranging from 3 to 8 mmol · l−1 [La−], 1 to 6 mmol · l−1 [La−] above the baseline, and 30 to 70° tangent to the exponential curve of [La−]) were also highly correlated with performance (r > 0.90). These results failed to demonstrate a distinct AT because many points of the curve provided similar information.
Intercorrelations and correlations between AT and performance were, however, reduced when AT were expressed as the percentage
of maximal treadmill speed obtained at AT or percentage of V˙O2
max
. This would indicate that different attributes of aerobic performance (i.e. maximal aerobic power, running economy and endurance)
are measured when manipulating units. Thus, coaches should be aware of these results when they prescribe an intensity for
training and concentrate more on the physiological consequences of a chosen [La−] rather than on a “threshold”.
Accepted: 22 October 1997 相似文献
9.
Bioenergetics and RNA/DNA ratios in the common carp (Cyprinus carpio ) under hypoxia 总被引:2,自引:0,他引:2
Zhou BS Wu RS Randall DJ Lam PK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2001,171(1):49-57
Hypoxia caused by eutrophication occurs over large areas in aquatic systems worldwide. Common carp (Cyprinus carpio) exposed to hypoxia (1 mg · O2 · l−1 and 2 mg · O2 · l−1) for 1 week showed a significant reduction in feeding rate, respiration rate, faecal production and nitrogenous excretion
compared to those maintained at normoxia (7 mg · O2 · l−1). Fish exposed to hypoxia showed negative scope for growth (SfG), but no significant difference in the specific growth rate
was revealed after 1 week in both hypoxic groups. A significant reduction in RNA/DNA ratio was, however, clearly evident in
the white muscle of the 1 mg · O2 · l−1 treatment group, but not in the 2 mg · O2 · l−1 treatment group. Both specific growth rate and RNA/DNA ratio were significantly reduced when fish were exposed to severe
hypoxia (0.5 mg · O2 · l−1) for 4 weeks. At all levels of hypoxia, growth reduction was accompanied by a significant decrease in RNA/DNA ratio in white
muscle. Covariance analysis showed no significant difference between the slope of RNA/DNA ratio and growth rate under normoxic
conditions and 0.5 mg · O2 · l−1 for 4 weeks (F=1.036, P > 0.326), as well as 1.0 mg · O2 · l−1 and 2.0 mg · O2 · l−1 for 1 week (F = 0.457, P > 0.5), indicating that the RNA/DNA ratio serves as a biomarker of growth under all oxygen levels, at least under controlled
experimental conditions. SfG also appears to be more sensitive than the RNA/DNA ratio in responding to hypoxia in fish.
Accepted: 15 September 2000 相似文献
10.
Jensen FB Koldkjaer P Bach A 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(7):489-495
Nitrite influx into crayfish showed saturation kinetics, supporting a carrier-mediated uptake. Addition of 4,4′-diisothiocyanatostilbene-2,2′-disulfonate
(DIDS: at 10−5, 10−4 and 10−3 M) and bumetanide (at 10−5 M and 10−4 M) to the ambient water did not significantly affect nitrite influx. Rather than suggesting that neither Cl−/HCO3
− exchange nor K+/Na+/2Cl− cotransport were involved in the transport, this may reflect that the gill cuticle has a low permeability to the pharmacological
agents, or that the sensitivity of the transport mechanism to the inhibitors is low. Nitrite accumulation in the haemolymph
was significantly decreased during hypercapnic conditions compared to normocapnic conditions. This supports the idea that
an acid–base regulatory decrease in Cl−(influx)/HCO3
− (efflux) induced by hypercapnia should decrease NO2
− uptake if NO2
− and Cl− share this uptake route. The respiratory acidosis caused by exposure to hypercapnia alone was partially compensated by HCO3
− accumulation in the haemolymph. Combined exposure to hypercapnia and nitrite improved pH recovery, mainly by augmenting the
[HCO3
−] increase, but also by decreasing haemolymph PCO2. Exposure to nitrite in normocapnic water induced an initial increase in haemolymph [HCO3
−] and later also a decrease in PCO2. Thus, the improved acid-base compensation during combined hypercapnia and nitrite exposure was an amplification of this
nitriteinduced response. Haemolymph base excess rose much more than haemolymph [Ca], suggesting that transfer of acid-base
equivalents between animal and water was more important than H+ buffering by exoskeletal CaCO3 in mediating the increase in haemolymph [HCO3
−].
Accepted: 27 June 2000 相似文献
11.
Leaf photosynthesis, plant growth and nitrogen allocation in rice under different irradiances 总被引:6,自引:0,他引:6
The photosynthetic rates and various components of photosynthesis including ribulose-1,5-bisphosphate carboxylase (Rubisco;
EC 4.1.1.39), chlorophyll (Chl), cytochrome (Cyt) f, and coupling factor 1 (CF1) contents, and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity were examined in young, fully expanded leaves of rice
(Oryza sativa L.) grown hydroponically under two irradiances, namely, 1000 and 350 μmol quanta · m−2 · s−1, at three N concentrations. The light-saturated rate of photosynthesis measured at 1800 μmol · m−2 · s−1 was almost the same for a given leaf N content irrespective of growth irradiance. Similarly, Rubisco content and SPS activity
were not different for the same leaf N content between irradiance treatments. In contrast, Chl content was significantly greater
in the plants grown at 350 μmol · m−2 · s−1, whereas Cyt f and CF1 contents tended to be slightly smaller. However, these changes were not substantial, as shown by the fact that the light-limited
rate of photosynthesis measured at 350 μmol · m−2 · s−1 was the same or only a little higher in the plants grown at 350 μmol · m−2 · s−1 and that CO2-saturated photosynthesis did not differ between irradiance treatments. These results indicate that growth-irradiance-dependent
changes in N partitioning in a leaf were far from optimal with respect to N-use efficiency of photosynthesis. In spite of
the difference in growth irradiance, the relative growth rate of the whole plant did not differ between the treatments because
there was an increase in the leaf area ratio in the low-irradiance-grown plants. This increase was associated with the preferential
N-investment in leaf blades and the extremely low accumulation of starch and sucrose in leaf blades and sheaths, allowing
a more efficient use of the fixed carbon. Thus, morphogenic responses at the whole-plant level may be more important for plants
as an adaptation strategy to light environments than a response of N partitioning at the level of a single leaf.
Received: 23 February 1997 / Accepted: 8 May 1997 相似文献
12.
Jerzy A. Zoladz Krzysztof Duda Joanna Majerczak 《European journal of applied physiology and occupational physiology》1998,77(5):445-451
A group of 12 healthy non-smoking men [mean age 22.3 (SD 1.1) years], performed an incremental exercise test. The test started
at 30 W, followed by increases in power output (P) of 30 W every 3 min, until exhaustion. Blood samples were taken from an antecubital vein for determination of plasma concentration
lactate [La−]pl and acid-base balance variables. Below the lactate threshold (LT) defined in this study as the highest P above which a sustained increase in [La−]pl was observed (at least 0.5 mmol · l−1 within 3 min), the pulmonary oxygen uptake (V˙O2) measured breath-by-breath, showed a linear relationship with P. However, at P above LT [in this study 135 (SD 30) W] there was an additional accumulating increase in V˙O2 above that expected from the increase in P alone. The magnitude of this effect was illustrated by the difference in the final P observed at maximal oxygen uptake (V˙O2max) during the incremental exercise test (P
max,obs at V˙O2max) and the expected power output at V˙O2max(P
max,exp at V˙O2max) predicted from the linear V˙O2-P relationship derived from the data collected below LT. The P
max,obs at V˙O2max amounting to 270 (SD 19) W was 65.1 (SD 35) W (19%) lower (P<0.01) than the P
max,exp at V˙O2max
. The mean value of V˙O2max reached at P
max,obs amounted to 3555 (SD 226) ml · min−1 which was 572 (SD 269) ml · min−1 higher (P<0.01) than the V˙O2 expected at this P, calculated from the linear relationship between V˙O2 and P derived from the data collected below LT. This fall in locomotory efficiency expressed by the additional increase in V˙O2, amounting to 572 (SD 269) ml O2 · min−1, was accompanied by a significant increase in [La−]pl amounting to 7.04 (SD 2.2) mmol · l−1, a significant increase in blood hydrogen ion concentration ([H+]b) to 7.4 (SD 3) nmol · l−1 and a significant fall in blood bicarbonate concentration to 5.78 (SD 1.7) mmol · l−1, in relation to the values measured at the P of the LT. We also correlated the individual values of the additional V˙O2 with the increases (Δ) in variables [La−]pl and Δ[H+]b. The Δ values for [La−]pl and Δ[H+]b were expressed as the differences between values reached at the P
max,obs at V˙O2max and the values at LT. No significant correlations between the additional V˙O2 and Δ[La−]pl on [H+]b were found. In conclusion, when performing an incremental exercise test, exceeding P corresponding to LT was accompanied by a significant additional increase in V˙O2 above that expected from the linear relationship between V˙O2 and P occurring at lower P. However, the magnitude of the additional increase in V˙O2 did not correlate with the magnitude of the increases in [La−]pl and [H+]b reached in the final stages of the incremental test.
Accepted: 30 October 1997 相似文献
13.
Solute mobilities in cuticular membranes of six species (Hedera helix, Malus domestica, Populus alba, Pyrus communis, Stephanotis floribunda, Strophantus gratus) were measured using plant hormones, growth regulators and other organic model compounds varying in molar volumes from 99
to 349 mL · mol−1 The dependence of mobilities (k*) on molar volume (V
x
) was exponential and could be described with equations of the type log
k*=log
k*0−′
V
x
. The y-intercepts (log
k*0) represent mobilities of a hypothetical solute of zero molar volume. The parameter β′ is a measure of size selectivity of
cuticular membranes and no differences among the six species were observed. At 25 °C the average β′ was 0.0095 mol · mL−1. Solute mobility decreased by about a factor of 8.9 when molar volume increased by 100 mL · mol−1 and the mobility of a compound with V
x
= 100 mL · mol−1 was about 700-fold higher than the mobility of a compound with V
x
= 400 mL · mol−1. Size selectivity decreased with increasing temperatures and for Strophantusβ′-values of 1.6 × 10−2 to 8.0 × 10-4 mol · mL−1 were obtained for 10 and 30 °C, respectively. The-intercepts (log k*0) differed among plant species by 3 orders of magnitude and since size selectivity was the same for all species, solute mobilities
for solutes having zero molar volumes were the sole cause for differences among species in solute mobilities and permeabilities.
We argue that these differences in k*0 are related to tortuosity of the diffusion path. These results were used to derive an equation which predicts rates of cuticular
penetration on the basis of k*0, the average size selectivity of 9.5 × 10−3 mol · mL−1 and the driving forces of penetration.
Received: 25 November 1997 / Accepted: 9 March 1998 相似文献
14.
Characteristics of net ecosystem carbon dioxide exchange (NEE) from August to October of Alpine meadow on the Tibetan Plateau, China 总被引:3,自引:0,他引:3
Xu Lingling Zhang Xianzhou Shi Peili Yu Guirui Sun Xiaomin 《Frontiers of Biology in China》2006,1(4):418-422
The Alpine meadow is one of the vegetation types widely distributed on the Tibetan Plateau in China with an area of about
1.2 million square kilometers. The Damxung rangeland station, located in the hinterland of the Tibetan Plateau, is covered
with an typical vegetation. The continuous carbon flux data (from August to middle October, 2003) measured with the open-path
eddy covariance system was used to analyze the diurnal variation pattern of net ecosystem carbon dioxide exchange (NEE) and
its relationship with the environmental factors, such as photosynthetically active radiation (PAR), precipitation, and temperature.
Results showed that NEE presented obvious diurnal variation pattern with single-peak of diurnal maximum carbon assimilation
at 11: 00–12: 00 (local time) with an average of −0.268 mg CO2·m−2·s−1, i.e., −6.08 μmol CO2·m−2·s−1. During the daytime, NEE fitted fairly well with PAR in a rectangular hyperbola function with the apparent quantum yield
(0.020 3 μmol CO2 μmol−1 PAR) and maximum ecosystem assimilation (9.741 1 μmol CO2·m−2·s−1). During the night-time, NEE showed a good exponential relation with the soil temperature at 5 cm depth.
__________
Translated from Acta Ecologica Sinica 2005, 25(8): 1948–1952 [译自: 生态学报, 2005, 25(8): 1948–1952] 相似文献
15.
Jerzy A. Zoladz Zbigniew Szkutnik Joanna Majerczak Krzysztof Duda 《European journal of applied physiology and occupational physiology》1998,78(4):369-377
The purpose of this study was to develop a method to determine the power output at which oxygen uptake (V˙O2) during an incremental exercise test begins to rise non-linearly. A group of 26 healthy non-smoking men [mean age 22.1 (SD
1.4) years, body mass 73.6 (SD 7.4) kg, height 179.4 (SD 7.5) cm, maximal oxygen uptake (V˙O2max) 3.726 (SD 0.363) l · min−1], experienced in laboratory tests, were the subjects in this study. They performed an incremental exercise test on a cycle
ergometer at a pedalling rate of 70 rev · min−1. The test started at a power output of 30 W, followed by increases amounting to 30 W every 3 min. At 5 min prior to the first
exercise intensity, at the end of each stage of exercise protocol, blood samples (1 ml each) were taken from an antecubital
vein. The samples were analysed for plasma lactate concentration [La]pl, partial pressure of O2 and CO2 and hydrogen ion concentration [H+]b. The lactate threshold (LT) in this study was defined as the highest power output above which [La−]pl showed a sustained increase of more than 0.5 mmol · l−1 · step−1. The V˙O2 was measured breath-by-breath. In the analysis of the change point (CP) of V˙O2 during the incremental exercise test, a two-phase model was assumed for the 3rd-min-data of each step of the test: X
i
=at
i
+b+ɛ
i
for i=1,2,…,T, and E(X
i
)>at
i
+b for i =T+1,…,n, where X
1, … , X
n
are independent and ɛ
i
∼N(0,σ2). In the first phase, a linear relationship between V˙O2 and power output was assumed, whereas in the second phase an additional increase in V˙O2 above the values expected from the linear model was allowed. The power output at which the first phase ended was called the
change point in oxygen uptake (CP-V˙O2). The identification of the model consisted of two steps: testing for the existence of CP and estimating its location. Both
procedures were based on suitably normalised recursive residuals. We showed that in 25 out of 26 subjects it was possible
to determine the CP-O2 as described in our model. The power output at CP-V˙O2 amounted to 136.8 (SD 31.3) W. It was only 11 W – non significantly – higher than the power output corresponding to LT. The
V˙O2 at CP-V˙O2 amounted to 1.828 (SD 0.356) l · min−1 was [48.9 (SD 7.9)% V˙O2
max
]. The [La−]pl at CP-V˙O2, amounting to 2.57 (SD 0.69) mmol · l−1 was significantly elevated (P<0.01) above the resting level [1.85 (SD 0.46) mmol · l−1], however the [H+]b at CP-V˙O2 amounting to 45.1 (SD 3.0) nmol · l−1, was not significantly different from the values at rest which amounted to 44.14 (SD 2.79) nmol · l−1. An increase of power output of 30 W above CP-V˙O2 was accompanied by a significant increase in [H+]b above the resting level (P=0.03).
Accepted: 25 March 1998 相似文献
16.
H. Arabi H. Vandewalle P. Pitor J. de Lattre H. Monod 《European journal of applied physiology and occupational physiology》1997,76(2):122-127
The present experiment was designed to study the importance of strength and muscle mass as factors limiting maximal oxygen
uptake (V˙O2
max
) in wheelchair subjects. Thirteen paraplegic subjects [mean age 29.8 (8.7) years] were studied during continuous incremental
exercises until exhaustion on an arm-cranking ergometer (AC), a wheelchair ergometer (WE) and motor-driven treadmill (TM).
Lean arm volume (LAV) was estimated using an anthropometric method based upon the measurement of various circumferences of
the arm and forearm. Maximal strength (MVF) was measured while pushing on the rim of the wheelchair for three positions of
the hand on the rim (−30°, 0° and +30°). The results indicate that paraplegic subjects reached a similar V˙O2
max
[1.23 (0.34) l · min−1, 1.25 (0.38) l · min−1, 1.22 (0.18) l · min−1 for AC, TM and WE, respectively] and V˙O2
max
/body mass [19.7 (5.2) ml · min−1 · kg−1, 19.5 (6.14) ml · min−1 · kg−1, 19.18 (4.27) ml · min−1 · kg−1 for AC, TM and WE, respectively on the three ergometers. Maximal heart rate f
c
max
during the last minute of AC (173 (17) beats · min−1], TM [168 (14) beats · min−1], and WE [165 (16) beats · min−1], were correlated, but f
c
max
was significantly higher for AC than for TM (P<0.03). There were significant correlations between MVF and LAV (P<0.001) and between the MVF data obtained at different angles of the hand on the rim [311.9 (90.1) N, 313.2 (81.2) N, 257.1
(71) N, at −30°, 0° and +30°, respectively]. There was no correlation between V˙O2
max
and LAV or MVF. The relatively low values of f
c
max
suggest that V˙O2
max
was, at least in part, limited by local aerobic factors instead of central cardiovascular factors. On the other hand, the
lack of a significant correlation between V˙O2
max
and MVF or muscle mass was not in favour of muscle strength being the main factor limiting V˙O2
max
in our subjects.
Accepted: 31 January 1997 相似文献
17.
Gerald S. Zavorsky David L. Montgomery David J. Pearsall 《European journal of applied physiology and occupational physiology》1998,77(3):224-230
The purposes of this study were to determine whether running economy (RE) is adversely affected following intense interval
bouts of 10 × 400-m running, and whether there is an interaction effect between RE and recovery duration during the workouts.
Twelve highly trained male endurance athletes [maximal oxygen consumption; V˙O2
max
=72.5 (4.3) ml·kg−1·min−1; mean (SD)] performed three interval running workouts of 10 × 400 m with a minimum of 4 days between runs. Recovery duration
between the repetitions was randomly assigned at 60, 120 or 180 s. The velocity for each 400-m run was determined from a treadmill
V˙O2
max
test. The average running velocity was 357.9 (9.0) m · min−1. Following the workout, the rating of perceived exertion (RPE) increased significantly (P < 0.01) as recovery duration between the 400-m repetitions decreased (14.4, 16.1, and 17.7 at 180s, 120s, and 60 s recovery,
respectively). Prior to and following each workout, RE was measured at speeds of 200 and 268 m · min−1. Changes in RE from pre- to post-workout, as well as heart rate (HR) and respiratory exchange ratio (R) were similar for the three recovery conditions. When averaged across conditions, oxygen consumption (V˙O2) increased significantly (P < 0.01) from pre- to post-test (from 38.5 to 40.5 ml · kg−1 · min−1 at 200 m · min−1, and from 53.1 to 54.5 ml · kg−1 · min−1 at 268 m · min−1, respectively). HR increased (from 124 to 138, and from 151 to 157 beats · min−1 respectively) and R decreased (from 0.90 to 0.78, and from 0.93 to 0.89, respectively) at 200 and 268 m · min−1, respectively (P < 0.01). This study showed that RE can be perturbed after a high-intensity interval workout and that the changes in V˙O2, HR and R were independent of the recovery duration between the repetitions.
Accepted: 23 June 1997 相似文献
18.
Castor bean (Ricinus communis L.) plants were grown for 5–7 weeks in a controlled environment at 350 μl l−1 or 700 μl l−1 CO2. Carbon assimilation, assimilate deposition, dark respiration and assimilate mobilization were measured in leaves 2, 3 and
4 (counted from the base of the plant), and a balance sheet of carbon input and export was elaborated for both CO2 concentrations. Carbon dioxide assimilation was nearly constant over the illumination period, with only a slight depression
occurring at the end of the day in mature source leaves, not in young source leaves. Assimilation was ca. 40% higher at 700 μl l−1 than at 350 μl l−1 CO2. The source leaves increased steadily in weight per unit area during the first 3 weeks, more at 700 μl l−1 than at 350 μl l−1 CO2. On top of an irreversible weight increase, there was a large gain in dry weight during the day, which was reversed during
the night. This reversible weight gain was constant over the life time of the leaf and ca. 80% higher at 700 μl l−1 than at 350 μl l−1. Most of it was due to carbohydrates. The carbon content (as a percentage) was not altered by the CO2 treatment. Respiration was 25% higher in high-CO2 plants when based on leaf area, but the same when based on dry weight. The rate of carbon export via the phloem was the same
during the daytime in plants grown at 350 μl l−1 and 700 μl l−1 CO2. During the night the low-CO2 plants had only 50% of the daytime export rate, in contrast to the high-CO2 plants which maintained the high export rate. It was concluded that the phloem loading system is saturated during the daytime
in both CO2 regimes, whereas during the night the assimilate supply is reduced in plants in the normal CO2 concentration. Two-thirds of the carbon exported from the leaves was permanently incorporated as plant dry matter in the
residual plant parts. This “assimilation efficiency” was the same for both CO2 regimes. It is speculated that under 350 μl l−1 CO2 the growing Ricinus plant operates at sink limitation during the day and at source limitation during the night.
Received: 2 February 1999 / Accepted: 19 April 1999 相似文献
19.
J. Hall I. A. Macdonald P. J. Maddison J. P. O''Hare 《European journal of applied physiology and occupational physiology》1998,77(3):278-284
This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise
on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water
temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h−1. Oxygen consumption (V˙O2) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing
speed both in water and on land. At 3.5 km · h−1
V˙O2 was similar across procedures [χ = 0.6 (0.05) l · min−1]. At 4.5 and 5.5 km · h−1
V˙O2 was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm:
0.8 and 0.9 l · min−1, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at
4.5 and 5.5 km · h−1 (P ≤ 0.003). The HR-V˙O2 relationship showed that at a V˙O2 of 0.9 l · min−1, HR was higher in water at 36°C (115 beats · min−1) than either on land (100 beats · min−1) or in water at 28°C (99 beats · min−1). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h−1 was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was
27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data
has implications for therapists working in hydrotherapy pools.
Accepted: 3 September 1997 相似文献
20.
Chaetoceros muelleri (Lemn.) was cultured with nitrite (NO2−) or nitrate (NO3−) as the sole nitrogen source and aerated with air or with CO2-enriched air. Cells of C. muelleri excreted into the medium nitrite produced by reduction of nitrate when grown with 100 μM NaNO3 as nitrogen source. Accordingly, NO2− concentration reached 10.4 μM after 95 h at the low CO2 condition (aerated with air); while the maximum NO2− concentration was only around 2.0 μM at the high CO2 condition (aerated with 5% CO2 in air), furthermore, after 30 h it decreased to no more than 1.0 μM. NO2− was almost assimilated in 80 h when C. muelleri was cultured at the high CO2 condition with 100 μM NaNO2 as sole nitrogen source. At the high CO2 condition, after 3 h the activity of nitrite reductase was as much as 50% higher than that at the low CO2 condition. It was indicated that enriched CO2 concentration could inhibit nitrite excretion and enhance nitrite assimilation by cells. Therefore, aeration with enriched
CO2 might be an effective way to control nitrite content in aquaculture systems. 相似文献