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1.
The reactions of trees to wind, rockfall, and snow and debris flow depend largely on how strong and deformable their anchorage
in the soil is. Here, the resistive turning moment M of the root–soil system as a function of the rotation ϕ at the stem base plays the major role. M(ϕ) describes the behavior of the root–soil system when subject to rotational moment, with the maximum M(ϕ) indicating the anchorage strength M
a of the tree. We assessed M(ϕ) of 66 Norway spruce (Picea abies L. Karst) by pulling them over with a winch. These 45- to 170-year-old trees grew at sites of low and high elevation, with
a diameter at breast height DBH = 14–69 cm and a height H = 9–42 m. M(ϕ) displayed a strong nonlinear behavior. M
a was reached at a lower ϕ for large trees than for small trees. Thus overhanging tree weight contributed less to M
a for the large trees. Overturning also occurred at a lower ϕ for the large trees. These observations show that the rotational ductility of the root–soil system is higher for small trees.
M
a could be described by four monovariate linear regression equations of tree weight, stem weight, stem volume and DBH
2
·H (0.80 < R
2 < 0.95), and ϕ at M
a, ϕ
a, by a power law of DBH2·H (R
2 = 0.85). We found significantly higher M
a for the low-elevation spruces than for the high-elevation spruces, which were more shallowly anchored, but no significant
difference in ϕ
a. The 66 curves of M(ϕ), normalized (n) by M
a in M-direction and by ϕ
a in ϕ-direction, yielded one characteristic average curve: . Using and the predictions of M
a and ϕ
a, it is shown that M(ϕ) and the curves associated with M(ϕ) can be predicted with a relative standard error ≤25%. The parameterization of M(ϕ) by tree size and weight is novel and provides useful information for predicting with finite-element computer models how
trees will react to natural hazards. 相似文献
2.
G. J. Grobben W. H. M. van Casteren H. A. Schols A. Oosterveld G. Sala M. R. Smith J. Sikkema J. A. M. de Bont 《Applied microbiology and biotechnology》1997,48(4):516-521
The exopolysaccharides produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 grown in defined medium were investigated. At equal cell densities, the strain produced 95 mg l−1 exopolysaccharides with glucose and 30 mg l−1 with fructose as the carbohydrate source. High-performance size-exclusion chromatography of the exopolysaccharides produced
on glucose showed the presence of two fractions with relative molecular masses (M
r) of 1.7 × 106 and 4 × 104 in almost equal amounts. The exopolysaccharides produced on fructose contained mainly a fraction of low M
r of 4 × 104. The high-M
r fraction of the purified exopolysaccharides produced on glucose appeared to have a sugar composition of galactose, glucose
and rhamnose in the molar ratio of 5:1:1, whereas the low-M
r weight fraction contained galactose, glucose and rhamnose in the molar ratio of approximately 11:1:0.4. The purified exopolysaccharide
fractions produced on fructose showed comparable ratios. The high-molecular-mass fractions contained terminally linked galactose,
1,2,3-linked galactose, 1,3,4-linked galactose, 1,3-linked glucose and terminally linked rhamnose. The low-molecular-mass
fractions contained mainly 1,3-linked galactose and 1,6-linked galactose and lower amounts of other sugar linkages. The production
of the high-M
r fractions appeared to be dependent on the carbohydrate source, whereas the low-M
r fractions were produced more continuously.
Received: 30 April 1997 / Received revision: 11 June 1997 / Accepted: 14 June 1997 相似文献
3.
Excessive Zn but normal Cu and Mg in the staple food consumed by the people of Chandigarh (Union territory and capital of
Punjab and Haryana States of India) has been considered to be the major risk factor for the prevalence of obesity (33.15%)
and obesity-related diseases in this region. Therefore, in the present investigations, in obesity-related diseases, the status
of these minerals was estimated in their tissues, including hair, nails, and blood serum and urine, and compared with those
of normal subjects. They were grouped as: normal subjects in control Group A, middle-aged diabetics in Group DM, older diabetics in Group DO, and diabetics with osteoarthritis in Group D+ OA, osteoarthritis in Group OA and rheumatoid arthritis in Group RA, respectively.
The results evaluated in the order as: hair Zn, group D+OA>DM>OA>A (control)>RA>DO (p < 0.001); hair Cu, group A (control)>DM>OA>D+OA>DO>RA (p < 0.001); hair Mg, group A (control)>DM>OA>D+OA>RA>DO (p < 0.001, 0.01); hair Mn, group A (control)>RA>OA>D-OA>DM>DO (p < 0.001); nail Zn, group DM>D+OA>OA>A (control)>RA>DO (p < 0.001, 0.05); nail Cu, group A (control)>OA>DM>D+OA>RA>DO (p < 0.001); nail Mg, group A (control)>OA>DM>DO>D+OA >RA (p < 0.001); nail Mn, group A (control) >RA>OA>D+OA>DM>DO (p < 0.01); urine Zn, group DO>DM>D+OA>A (control)>RA>OA (p < 0.01); urine Cu, group RA>D+OA>DO>OA> DM>A (control) (p<0.001); urine Mg, group RA>OA>D+OA>DO>DM>A (control; p < 0.001); urine Mn, group DO>DM>OA>D+OA>RA>A (control; p < 0.001), respectively. The analysis of the mineral status in serum of diabetics further showed their highly significant
rise from lower mean age subgroup to higher mean age subgroup than their control counter parts (p < 0.001, 0.01, and 0.05) with coincident deficiencies of Cu, Mg, and Mn in their tissues. This study would be helpful considering
the status of minerals in these obesity-related diseases depending on the choice of the food consumed to improve the quality
of life and prognosis for the diseases. 相似文献
4.
Ribitsch D Karl W Wehrschütz-Sigl E Tutz S Remler P Weber HJ Gruber K Stehr R Bessler C Hoven N Sauter K Maurer KH Schwab H 《Applied microbiology and biotechnology》2009,81(5):875-886
In the course of a microbial screening of soil samples for new oxidases, different enrichment strategies were carried out.
With choline as the only carbon source, a microorganism was isolated and identified as Arthrobacter nicotianae. From this strain, a gene coding for a choline oxidase was isolated from chromosomal DNA. This gene named codA was cloned in Escherichia coli BL21-Gold and the protein (An_CodA) heterologously overexpressed as a soluble intracellular protein of 59.1 kDa. Basic biochemical characterization of
purified protein revealed a pH optimum of 7.4 and activity over a broad temperature range (15–70 °C). Specific activities
were determined toward choline chloride (4.70 ± 0.12 U/mg) and the synthetic analogs bis(2-hydroxyethyl)-dimethylammonium
chloride (0.05 ± 0.45 × 10–2 U/mg) and tris-(2-hydroxyethyl)-methylammonium methylsulfate (0.01 ± 0.12 × 10–2 U/mg). With increasing number of oxidizable groups, a significant decrease in activity was noted. Determination of kinetic
parameters in atmorspheric oxygen resulted in K
M = 1.51 ± 0.09 mM and V
max = 42.73 ± 0.42 mU/min for choline chloride and K
M = 4.77 ± 0.76 mM and V
max = 48.40 ± 2.88 mU/min for the reaction intermediate betaine aldehyde respectively. Nuclear magnetic resonance spectroscopic
analysis of the products formed during the enzyme reaction with choline chloride showed that in vitro the intermediate betaine
aldehyde exists also free in solution. 相似文献
5.
The proportion of mated females (M f) of the osmund sawfly, Strongylogaster osmundae, and the sex ratio of the eggs they deposited (r, proportion of males) were estimated in the wild by collecting egg masses. The proportion of mated females at oviposition varied from 0 to 1.0. M f was high (often 1.0) among the females that emerged after hibernation, and lower in the subsequent generations. Mated females of the hibernated generation deposited equal numbers of eggs of both sexes. Mated females of the first and subsequent generations produced more female than male eggs. These results qualitatively agreed with the prediction provided by an evolutionarily stable strategy (ESS) model (if M f < 1 then r < 0.5). However, the quantitative prediction provided by the model [M f (1 − r) = 0.5] was not always observed in the wild, especially where the population density and M f were high. The value of r was often lower than the predicted one. The following simple hypothesis was tested by experimentation: “Females that encounter males frequently estimate the proportion of mated females to be high and deposit eggs with a 1:1 sex ratio.” However, results did not support this hypothesis. Females that copulated soon after emergence and were courted by males two or more times did not show a higher offspring sex ratio than those which mated 1 or 2 days after emergence and experienced no other sexual encounter. Another mechanism for determination of r is suggested, and the reason why the population sex ratio of sawflies is often female-biased (r < 0.5) is discussed. 相似文献
6.
This article reports rate constants for thiol–thioester exchange (k
ex), and for acid-mediated (k
a), base-mediated (k
b), and pH-independent (k
w) hydrolysis of S-methyl thioacetate and S-phenyl 5-dimethylamino-5-oxo-thiopentanoate—model alkyl and aryl thioalkanoates, respectively—in water. Reactions such as
thiol–thioester exchange or aminolysis could have generated molecular complexity on early Earth, but for thioesters to have
played important roles in the origin of life, constructive reactions would have needed to compete effectively with hydrolysis
under prebiotic conditions. Knowledge of the kinetics of competition between exchange and hydrolysis is also useful in the
optimization of systems where exchange is used in applications such as self-assembly or reversible binding. For the alkyl
thioester S-methyl thioacetate, which has been synthesized in simulated prebiotic hydrothermal vents, k
a = 1.5 × 10−5 M−1 s−1, k
b = 1.6 × 10−1 M−1 s−1, and k
w = 3.6 × 10−8 s−1. At pH 7 and 23°C, the half-life for hydrolysis is 155 days. The second-order rate constant for thiol–thioester exchange
between S-methyl thioacetate and 2-sulfonatoethanethiolate is k
ex = 1.7 M−1 s−1. At pH 7 and 23°C, with [R″S(H)] = 1 mM, the half-life of the exchange reaction is 38 h. These results confirm that conditions
(pH, temperature, pK
a of the thiol) exist where prebiotically relevant thioesters can survive hydrolysis in water for long periods of time and
rates of thiol–thioester exchange exceed those of hydrolysis by several orders of magnitude. 相似文献
7.
Nicola D’Amelio Luca Fontanive Fulvio Uggeri Furio Suggi-Liverani Luciano Navarini 《Food biophysics》2009,4(4):321-330
Caffeine complexation by chlorogenic acid (3-caffeoylquinic acid, CAS Number [327-97-9]) in aqueous solution as well as caffeine–chlorogenate
complex in freshly prepared coffee brews have been investigated by high-resolution 1H-NMR. Caffeine and chlorogenic acid self-associations have also been studied and self-association constants have been determined
resorting to both classical isodesmic model and a recently introduced method of data analysis able to provide also the critical
aggregation concentration (cac). Furthermore, caffeine–chlorogenate association constant was measured. For the caffeine, the
average value of the self-association constant determined by isodesmic model (K
i = 7.6 ± 0.5 M−1) is in good agreement with the average value (K
a = 10 ± 1.8 M−1) determined with the method which permits the determination of the cac (8.43 ± 0.05 mM). Chlorogenic acid shows a slight
decreased tendency to aggregation with a lower average value of association constants (K
i = 2.8 ± 0.6 M−1; K
a = 3.4 ± 0.6 M−1) and a critical concentration equal to 24 ± 1 mM. The value of the association constant of the caffeine–chlorogenate complex
(30 ± 4 M−1) is compatible with previous studies and within the typical range of reported association constants for other caffeine–polyphenol
complexes. Structural features of the complex have also been investigated, and the complex conformation has been rediscussed.
Caffeine chemical shifts comparison (monomeric, complexed, coffee brews) clearly indicates a significant amount of caffeine
is complexed in beverage real system, being chlorogenate ions the main complexing agents. 相似文献
8.
Recently Haas et al. (J Neurophysiol 96: 3305–3313, 2006), observed a novel form of spike timing dependent plasticity (iSTDP) in GABAergic synaptic couplings in layer II of the entorhinal
cortex. Depending on the relative timings of the presynaptic input at time t
pre and the postsynaptic excitation at time t
post, the synapse is strengthened (Δt = t
post − t
pre > 0) or weakened (Δt < 0). The temporal dynamic range of the observed STDP rule was found to lie in the higher gamma frequency band (≥40 Hz),
a frequency range important for several vital neuronal tasks. In this paper we study the function of this novel form of iSTDP
in the synchronization of the inhibitory neuronal network. In particular we consider a network of two unidirectionally coupled
interneurons (UCI) and two mutually coupled interneurons (MCI), in the presence of heterogeneity in the intrinsic firing rates
of each coupled neuron. Using the method of spike time response curve (STRC), we show how iSTDP influences the dynamics of
the coupled neurons, such that the pair synchronizes under moderately large heterogeneity in the firing rates. Using the general
properties of the STRC for a Type-1 neuron model (Ermentrout, Neural Comput 8:979–1001, 1996) and the observed iSTDP we determine conditions on the initial configuration of the UCI network that would result in 1:1
in-phase synchrony between the two coupled neurons. We then demonstrate a similar enhancement of synchrony in the MCI with
dynamic synaptic modulation. For the MCI we also consider heterogeneity introduced in the network through the synaptic parameters:
the synaptic decay time of mutual inhibition and the self inhibition synaptic strength. We show that the MCI exhibits enhanced
synchrony in the presence of all the above mentioned sources of heterogeneity and the mechanism for this enhanced synchrony
is similar to the case of the UCI. 相似文献
9.
Tiecheng Qiao Robert Witkowski Robin Henderson G. McLendon 《Journal of biological inorganic chemistry》1996,1(5):432-438
The kinetics of methemoglobin reduction by cytochrome b
5 has been studied by stopped-flow and saturation transfer NMR. A forward rate constant k
f = 2.44×104 M–1 s–1 and a reverse rate constant k
b = 540 M–1s–1 have been observed at 10 mm, pH 6.20, 25 °C. The ratio k
f/k
b = k
eq = 43.6 is in good agreement with the equilibrium constant calculated from the electrochemical potential between cyt b
5 and methemoglobin. A bimolecular collisional mechanism is proposed for the electron transfer from cyt b
5 to methemoglobin based on the kinetic data analysis. The dependence of the rate constants on ionic strengths supports such
collisional mechanism. It is also found that the reaction rate strongly depends on the conformations of methemoglobin.
Received: 20 February 1996 / Accepted: 4 June 1996 相似文献
10.
Juozas Kulys Kastis Krikstopaitis Arturas Ziemys 《Journal of biological inorganic chemistry》2000,5(3):333-340
N -substituted phenothiazines (PTs) and phenoxazines (POs) catalyzed by fungal Coprinus cinereus peroxidase and Polyporus pinsitus laccase were investigated at pH 4–10. In the case of peroxidase, an apparent bimolecular rate constant (expressed as k
cat/K
m) varied from 1 ×107 M−1 s−1to 2.6×108 M−1 s−1 at pH 7.0. The constants for PO oxidation were higher in comparison to PT. pH dependence revealed two or three ionizable
groups with pK
a values of 4.9–5.7 and 7.7–9.7 that significantly affected the activity of peroxidase. Single-turnover experiments showed
that the limiting step of PT oxidation was reduction of compound II and second-order rate constants were obtained which were
consistent with the constants at steady-state conditions. Laccase-catalyzed PT and PO oxidation rates were lower; apparent
bimolecular rate constants varied from 1.8×105 M−1 s−1 to 2.0×107 M−1 s−1 at pH 5.3. PO constants were higher in comparison to PT, as was the case with peroxidase. The dependence of the apparent
bimolecular constants of compound II or copper type 1 reduction, in the case of peroxidase or laccase, respectively, was analyzed
in the framework of the Marcus outer-sphere electron-transfer theory. Peroxidase-catalyzed reactions with PT, as well as PO,
fitted the same hyperbolic dependence with a maximal oxidation rate of 1.6×108 M−1 s−1 and a reorganization energy of 0.30 eV. The respective parameters for laccase were 5.0×107 M−1 s−1 and 0.29 eV.
Received: 20 September 1999 / Accepted: 24 February 2000 相似文献
11.
The magnetic surface polaritons (MSPs) mode rarely exists in natural materials, mainly due to their limited magnetic response.
In order to understand the relationship between the MSPs mode and the limited magnetic response, we theoretically derive a
general dispersion equation of the MSPs mode for two kinds of biaxial anisotropic media. The dispersion equation suggests
the requirements of μ
x
< 0 < ε
z
, μ
x
μ
y
> 1, and momentum conservation need to be satisfied, which guides us to design a planar biaxial magnetic metamaterials (PBMM)
with two orthogonal negative permeabilities (i.e., μ
x
< 0 and μ
y
< 0). In addition, the results of the retrieval magnetic permeability and electric permittivity indeed point out that our
PBMM satisfies the aforementioned requirements. Meanwhile, we investigate the mechanism of the magnetic field by a consideration
of an induced current loop, and subsequently we demonstrate the artificial MSPs mode under transverse electric excitation
by numerical simulation. After a numerical fit of simulation results, we find that the field of the MSPs mode is in good agreement
with the analytical calculation of Maxwell’s equations. Moreover, we also simulate three unsatisfied aforementioned requirements
as control conditions to verify the general dispersion equation of the MSPs mode. 相似文献
12.
The genus Culter, found only in East Asia (China, Vietnam, Korea and Russia), is a primary group of freshwater fishes in the subfamily Cultrinae
(Cyprinidae). Of a total of 517 specimens studied, 235 were Culter alburnus from different localities and were used for morphometric analysis in this study. 17 landmarks were used in geometric morphometrics
(GM) analysis of shapes. 13 traditional morphometrics (TM) and 21 truss-based morphometrics (TBM) characteristics were measured.
The results of discriminant analysis and cluster analysis showed that four species-groups could be divided into separate groups.
They were (1) C. alburnus + C. recurviceps, (2) C. dabryi dabryi + C. oxycephalus + C. dabryi shinkainensis, (3) C. oxycephaloides, (4) C. mongolicus mongolicus + C. mongolicus elongates + C. mongolicus qionghaiensis. The six populations of C. alburnus (Basilewsky, Nouv Mém Soc Imp Nat Moscou, 10:215–263, 1855), from Lake Poyanghu, River Songhuajiang, River Liaohe, River Jialingjiang, River Lijiang and Lake Taihu, should be classified
as different geographical populations, but not subspecies. C. mongolicus elongates (He and Liu, Zool Res, 1(4):483–485, 1980) from Lake Chenghaihu and C. mongolicus qionghaiensis (Ding, Acta Zootaxon Sin, 15(2):246–250, 1990) from Lake Qionghaihu should be classified as subspecies. C. dabryi shinkainensis differed greatly from C. dabryi dabryi in body forms, and we suggest that C. dabryi shinkainensis should be changed to species, instead of subspecies, namely Culter shinkainensis (Yih and Chu, Acta Hydrobiol Sin, 2:170–199, 1959). 相似文献
13.
Changes in broadline proton nuclear magnetic resonance parameters of cell walls during growth of etiolated hypocotyls of bean (Phaseolus vulgaris L.) indicate that cell wall structure becomes more rigid during development. Most of the changes are completed in the first 6 cm below cotyledon insertion and are correlated with increased restriction of proton movements in regions of dense polymer packing.Abbreviations FID
free induction decay
- M2
second moment
- M2interpair
interpair second moment
- NMR
nuclear magnetic resonance
- T1D
dipolar relaxation time
- T2
spin-spin relaxation time
This work was supported by grants from Natural Sciences and Engineering Research Council of Canada to A.L.M., I.E.P.T. and M. Bloom. 相似文献
14.
Lammer H Kislyakova KG Odert P Leitzinger M Schwarz R Pilat-Lohinger E Kulikov YN Khodachenko ML Güdel M Hanslmeier M 《Origins of life and evolution of the biosphere》2011,41(6):503-522
We discuss the evolution of the atmosphere of early Earth and of terrestrial exoplanets which may be capable of sustaining
liquid water oceans and continents where life may originate. The formation age of a terrestrial planet, its mass and size,
as well as the lifetime in the EUV-saturated early phase of its host star play a significant role in its atmosphere evolution.
We show that planets even in orbits within the habitable zone of their host stars might not lose nebular- or catastrophically
outgassed initial protoatmospheres completely and could end up as water worlds with CO2 and hydrogen- or oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet evolves to an N2-rich atmosphere too early in its lifetime, the atmosphere may be lost. We show that the initial conditions set up by the
formation of a terrestrial planet and by the evolution of the host star’s EUV and plasma environment are very important factors
owing to which a planet may evolve to a habitable world. Finally we present a method for studying the discussed atmosphere
evolution hypotheses by future UV transit observations of terrestrial exoplanets. 相似文献
15.
Emmanuel Collec Yves Colin Florence Carbonnet Claude Hattab Olivier Bertrand Jean Pierre Cartron C. Le Van Kim 《Immunogenetics》1999,50(1-2):16-21
The human Kx blood group antigen is carried by a 37 000 M
r apparent molecular mass membrane polypeptide which is deficient in rare individuals with the McLeod syndrome. The X-linked
human XK gene is transcribed in many tissues including adult skeletal muscle and brain, sieges of disorders observed in McLeod syndrome.
We report here the cloning of the orthologous mouse XK mRNA. Comparison of XK from human and mouse revealed 80% sequence similarity at the amino acid level. The mouse XK gene is organized in two exons and is expressed in many tissues, but its expression pattern is slightly different from that
of the human gene. The presence in mouse erythrocyte membrane of a 43 000 M
r Kx-related protein was demonstrated by immunoblotting with a rabbit antiserum directed against the human protein. With non-reduced
samples, a 140 000 M
r species was detected instead of the 43 000 M
r protein, suggesting that, as demonstrated in the Kx polypeptide might be complexed with another protein in mouse red cells,
presumably the homologue of the human Kell protein of 93 000 M
r.
Received: 22 February 1999 / Revised: 8 June 1999 相似文献
16.
Under intracellular recording, we studied the effect of ATP on nerve cells of the rat intact nodose ganglion. The resting
membrane potential of the examined neurons was, on average, –60.3 ± 1.4 mV (n = 84); among such units, 88% were classified as C cells. Local application of 2 mM ATP to the surface of the ganglion using
a modified laminar flow system led to depolarization of neurons by 7.1 ± 0.9 mV, on average (n = 19). A blocker of P2X receptors, PPADS (100 μM), suppressed these depolarization responses, decreasing their amplitude,
on average, to 16 ± 3% (n = 3) of the initial value. The obtained data indicate that an overwhelming majority of neurons of the intact nodose ganglion
possess functional P2X receptors on their membranes. The absence of the corresponding responses in a considerable part of
neurons of intact spinal ganglia [13-15] was, apparently, determined by the fact that P2X receptors in the course of the described experiments had enough time to
desensitize before ATP reached the effective concentration. 相似文献
17.
Regeneration of garlic callus as affected by clonal variation, plant growth regulators and culture conditions over time 总被引:3,自引:0,他引:3
A long-term regeneration system for garlic (Allium sativum L.) clones of diverse origin was developed. Callus was initiated on a modified Gamborg's B-5 medium supplemented with 4.5 μM 2,4-D and maintained on the same basal medium with 4.7 μM picloram+0.49 μM 2iP. Regeneration potential of callus after 5, 12 and 16 months on maintenance medium was measured using several plant growth
regulator treatments. The 1.4 μM picloram+13.3 μM BA treatment stimulated the highest rate of shoot production. Regeneration rate decreased as callus age increased, but healthy
plantlets from callus cultures up to 16-months-old were produced for all clones. Regeneration of long-term garlic callus cultures
could be useful for clonal propagation and transformation.
Received: 24 September 1998 / Revision received: 27 January 1999 / Accepted: 26 February 1999 相似文献
18.
Wang Xi-Ling Zhou Jin-Xing Yu Mao-De Li Zhen-Gang Jin Xiao-Yun Li Qi-You 《In vitro cellular & developmental biology. Plant》2011,47(3):434-440
Efficient plant regeneration is essential for successful transformation and in vitro polyploidy induction in mulberry. A high frequency (80%) of plant regeneration from hypocotyls occurred under in vitro conditions in mulberry (Morus multicaulis Poir.). We identified three key factors for enhancing successful regeneration based on earlier work: (1) hypocotyl position,
(2) the combination and concentration of growth regulators, and (3) the addition of AgNO3. The highest frequency of shoot regeneration was achieved using hypocotyl segments, which are proximal to apical meristems,
and the optimal culture conditions were Murashige and Skoog’s (MS) (Murashige and Skoog, 1962) basal medium supplemented with 3.0 mg l−1 6-benzylamino purine, 0.3 mg l−1 indole-3-acetic acid, 0.1% polyvinypyrrolidone, and 1.0 mg/l silver nitrate (AgNO3) under subdued light at 25 ± 2°C. Treating the shoots with 0.2% colchicine (dipping for 72 h) resulted in a 14% tetraploid
frequency, whereas a 20% tetraploid frequency resulted from using a 0.25% colchicine (dripping for 5 d) treatment, as determined
by chromosome number counts. The diploid plant chromosome number was 28 (2n = 2x = 28) and that of tetraploid plants was 56 (2n = 4x = 56). Regenerated shoots rooted easily in 8–10 d using half-strength basal MS medium with 0.5 mg l−1 indole-3-butyric acid and were successfully established in the soil. 相似文献
19.
R. Candau A. Belli G. Y. Millet D. Georges B. Barbier J. D. Rouillon 《European journal of applied physiology and occupational physiology》1998,77(6):479-485
The aim of the present study was to examine the physiological and mechanical factors which may be concerned in the increase
in energy cost during running in a fatigued state. A group of 15 trained triathletes ran on a treadmill at velocities corresponding
to their personal records over 3000m [mean 4.53 (SD 0.28) m · s−1] until they felt exhausted. The energy cost of running (C
R) was quantified from the net O2 uptake and the elevation of blood lactate concentration. Gas exchange was measured over 1 min firstly during the 3rd–4th min
and secondly during the last minute of the run. Blood samples were collected before and after the completion of the run. Mechanical
changes of the centre of mass were quantified using a kinematic arm. A significant mean increase [6.9 (SD 3.5)%, P < 0.001] in C
R from a mean of 4.4 (SD 0.4) J · kg−1 · m−1 to a mean of 4.7 (SD 0.4) J · kg−1 · m−1 was observed. The increase in the O2 demand of the respiratory muscles estimated from the increase in ventilation accounted for a considerable proportion [mean
25.2 (SD 10.4)%] of the increase in CR. A mean increase [17.0 (SD 26.0)%, P < 0.05] in the mechanical cost (C
M) from a mean of 2.36 (SD 0.23) J · kg−1 · m−1 to a mean of 2.74 (SD 0.55) J · kg−1 · m−1 was also noted. A significant correlation was found between C
R and C
M in the non-fatigued state (r = 0.68, P < 0.01), but not in the fatigued state (r = 0.25, NS). Furthermore, no correlations were found between the changes (from non-fatigued to fatigued state) in C
R and the changes in C
M suggesting that the increase in C
R is not solely dependent on the external work done per unit of distance. Since step frequency decreased slightly in the fatigued
state, the internal work would have tended to decrease slightly which would not be compatible with an increase in C
R. A stepwise regressions showed that the changes in C
R were linked (r = 0.77, P < 0.01) to the changes in the variability of step frequency and in the variability of potential cost suggesting that a large
proportion of the increase in C
R was due to an increase in the step variability. The underlying mechanisms of the relationship between C
R and step variability remains unclear.
Accepted: 15 September 1997 相似文献
20.
Xiaodong Li Myong Jong Yi Yowhan Son Pil Sun Park Kyeong Hak Lee Yeong Mo Son Rae Hyun Kim Mi Jeong Jeong 《Journal of Plant Biology》2010,53(6):381-386
Biomass expansion factors, which convert the timber volume (or dry weight) to biomass, are used to estimate the forest biomass
and account for the carbon budget at the national or regional level. This study estimated the biomass conversion and expansion
factors (BCEF), root to shoot ratio (R), biomass expansion factors (BEF) of natural Japanese Red Pine (Pinus densiflora Sieb. et Zucc.) forests based on direct field measurements and publications in Korea. This study attempted to fit the non-linear
relationships between the biomass expansion factors (BCEF and BEF) and main stand factors [stand age, tree height, and diameter
at breast height (DBH)]. The relationship between BEF and each main stand factor was expressed as a simple logarithmical equation.
The BCEF was also expressed as a logarithmical equation of the tree height, DBH, and stand volume, whereas there was no significant
relationship between BCEF and stand age. The mean value for BCEF, BEF, and R was 0.5821 Mg m−3 (n = 22, SD = 0.1196), 1.4465 (n = 22, SD = 0.2905), and 0.2220 (n = 17, SD = 0.0687), respectively. The values of the biomass expansion factors in this study may indicate much representativeness
to estimate forest biomass in natural Japanese Red Pine forests of Korea than the default values given by the IPCC (2003, 2006). 相似文献