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1.
Net photosynthetic (P
N) and dark respiration (R
D) rate, stomatal (rs′) and internal (ri′) resistances to carbon dioxide were measured by gas exchange methods on leaves of different ages, expressed in leaf plastochron
index units (LPI) for a fast growing poplar cultivar Unal 2. Although the optimal leaf age differs slightly for the different
gas exchange parameters, leaf ontogeny is reflected in the same way in these different parameters. MaximalP
N and minimalrs′ and ri′ values were found at LPI between 6 and 10. Chlorophyll concentrations were lowest at LPI lower than 10 although an
increase in two steps was found, when leaf age increases up to maturity. 相似文献
2.
Growth bands are alternate dark/light bands perpendicular to the feather rachis. Previous studies indicate that pairs of dark/light bands are grown every 24h, with light bands being produced at night, and dark ones during the day. Thus, the dark:light width ratio could reflect the photoperiod under which a feather was grown. We tested this hypothesis by inducing feathers to grow under contrasting photoperiods, using red‐legged partridges Alectoris rufa as a model species. We first validated the assumption that a pair of dark/light band is produced every day. Secondly, we show that dark/light width ratios remain close to 1:1, irrespective of the photoperiod under which feathers were grown. Dark:light width ratios of feathers grown in summer (15 light‐hours: 9 darkness‐hours) and winter solstices (9l: 15d) did not show any consistent pattern of variation within individuals. Thus, the dark/light banding patterns are not simply the product of light regimes and are not indicative of photoperiod. This finding, together with reports of “aberrant” growth band patterns (e.g. two growth bands produced over 24 h instead of one) challenges our current knowledge of growth bands. We propose that the normal circadian periodicity of growth bands is primarily driven by circadian rhythms: band formation starts at a point of critically low physiological activity (e.g. during night resting), and thus every 24 h irrespective of photoperiod. Our experiment emphasises that our knowledge of growth bands is weaker than previously appreciated, and that the study of dark/light band patterns on feathers could shed new light on interesting phenomena such as unusual avian biological rhythms and the functioning of internal clocks. Detecting “aberrant” banding patterns could therefore allow identifying bird species with unusual activity patterns or physiological rhythms. 相似文献
3.
John B. Lewis 《Coral reefs (Online)》1991,9(4):209-214
Prominent bands or lines were present on colonies of Millepora complanata on coral reefs at Barbados, West Indies. These bands appeared as regular, dark and light horizontal zones or stripes on vertically growing plates and blades making up the colonies. Bands are formed by wave-like undulations or currugations of the skeletal surface. The number of bands correlates with colony height and mean band width equals the mean annual vertical growth of measured colonies. Variation in annual growth and differences in growth rates of colonies between different reefs were determined from band width measurements. Bands provide a rapid and non-destructive means for measuring growth and ageing colonies of M. complanata. 相似文献
4.
Curcuma zedoaria (Christm.) Roscoe, a member of the family Zingiberaceae, is one of the most widely distributed Curcuma species in Bangladesh. It is a well-known and important species because of its medicinal and horticultural values. However,
some plant populations are predicted to be depleted due to habitat destruction and due to extensive collection by local inhabitants.
In order to estimate the level of genetic diversity within and between natural populations, RAPD analyses were performed using
individual plants from different populations. We used Shannon’s index to partition genetic diversity which clearly demonstrated
that hilly populations of Srimangal, Chittagong and Sitakundu maintain rather higher genetic diversity than that of plain
land and plateau land populations of Savar and Birganj, respectively. We found a high intrapopulational (H′pop/H′sp) genetic diversity of 0.717 that was higher than the interpopulation diversity G
ST[(H′sp−H′pop)/H′sp] value of 0.283. Principal Coordinates Analysis (PCoA) showed that individuals of the hilly populations were combined in
one group, separated from the plain land and plateau land populations. From a conservation point of view, our results suggest
that special attention should be kept on the small populations of plain and plateau lands that are critically threatened due
to high anthropogenic activities. 相似文献
5.
DUANE R. DIEFENBACH MARY JO CASALENA MICHAEL V. SCHIAVONE DAVID SWANSON MICHAEL REYNOLDS ROBERT C. BOYD ROBERT ERIKSEN BRYAN SWIFT 《The Journal of wildlife management》2009,73(6):996-999
ABSTRACT We estimated loss of butt-end leg bands on male wild turkeys (Meleagris gallapavo) captured in New York, Ohio, and Pennsylvania (USA) during December-March, 2006–2008. We used aluminum rivet leg bands as permanent marks to estimate loss of regular aluminum, enameled aluminum, anodized aluminum, and stainless steel butt-end leg bands placed below the spur. We used band loss information from 887 turkeys recovered between 31 days and 570 days after release (x̄ = 202 days). Band loss was greater for turkeys banded as adults (>1 yr old) than juveniles and was greater for aluminum than stainless steel bands. We estimated band retention was 79–96%, depending on age at banding and type of band, for turkeys recovered 3 months after release. Band retention was <50% for all age classes and band types 15 months after banding. We concluded that use of butt-end leg bands on male wild turkeys is inappropriate for use in mark-recapture studies. 相似文献
6.
Hisashi Imamura 《Ichthyological Research》2007,54(3):303-307
A new platycephalid, Rogadius mcgroutheri, is described on the basis of the specimens collected from eastern Australia and New Caledonia. Rogadius mcgroutheri is distinguished from other congeners by 11 second dorsal fin rays usually, 4 or 6–8 unbranched lower pectoral fin rays,
larger orbital diameter, usually single preocular spine lacking the accessory spines on the anterior base, short antrorse
preopercular spine, tooth band on palatine narrow, with 2 irregular tooth rows, body with indistinct or somewhat distinct
brown blotches, and caudal fin with dark brown spots and bands. 相似文献
7.
In L. pardalinum, narrow bands of quinacrine fluorescence are distributed throughout the chromosomes. These vary in intensity from dull to bright, and their constant pattern allows all chromosomes to be recognized. Bright bands occur at some centromeres, and near all three nucleolar constrictions. In L. longiflorum, similar Q-bands occur along chromosomes, but they are less distinctive and their pattern does not closely match that of L. pardalinum. Also, L. longiflorum does not have bright regions at or near primary and secondary constrictions. Most Q-bands do not coincide with dark Giemsa C-bands, except for the bright nucleolar and centromeric regions in L. pardalinum. All C-banded heterochromatin stains identically after SSC pretreatment, dark with Giemsa and bright with quinacrine.— The many Q-bands of varying intensity, wide distribution and constant pattern, unrelated to C-bands, may be analogous to mammalian Q-bands. Such universality is expected if Q-bands area fundamental component of chromosome architecture. 相似文献
8.
A las-like quorum-sensing system in Pseudomonas sp. M18 was identified, which consisted of lasI and lasR genes encoding LuxI-LuxR type regulator. Several functions of the las system from strain M18 were investigated in this study. The chromosomal inactivation of either lasI or lasR by recombination increased the production of both pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA) by 4-5 fold and 2-3 fold over that of the wild type strain of M18, respectively. Production of both antibiotics was restored to wild-type levels after in trans complementation with the wild-type lasI or lasR gene. Ex-pression of the translational fusions pltA1523;-1523;lacZ and phzA1523;-1523;lacZ further confirmed the negative effect of lasI or lasR on both biosynthetic operons, and it was also demonstrated that the las system was related to the ability of swarming motility and the inhibition of cell growth. 相似文献
9.
This study investigates the nature and components of annual luminescent banding in massive Porites coral skeletons, with a view to refining the technique for using this banding to reconstruct past environmental conditions.
Three-dimensional excitation-emission-matrix spectroscopy and optical fibre beam delivery have been used to investigate the
luminescence properties of the bright and dull bands of solid coral. Six characteristic excitation/emission peaks have been
identified: 280/450–600, 340/450, 370/470, 390/485, 420/505 and 450/530 nm. The first peak corresponds to protein-type fluorescence.
The others are characteristic of humic acid luminescence. The difference in luminescence intensity between bright and dull
bands has been quantified and characterised spectroscopically. The luminescence of the bright bands is up to 25% more intense
than their neighbouring dull bands with the greatest increase in relative intensity in the long wavelength emission region,
between 500 and 600 nm. The contribution of long-lived phosphorescence to the total luminescence intensity has been determined
by time-resolved measurements on the 100 ms timescale. Both bright and dull bands show long-lived phosphorescence with decay
times up to 1.5 s. This phosphorescence accounts for about 10% of the total luminescence intensity of bright bands. The difference
in phosphorescence intensity between bright and dull bands is substantially greater than the difference in total luminescence
intensity: the phosphorescence of bright bands is up to twice as intense as that of dull bands. This suggests that phosphorescence
plays an important role in defining luminescent banding in coral. Furthermore, the large observable difference in phosphorescence
between bright and dull bands indicates that measurement of phosphorescence profiles across growth bands in corals may prove
to be a more sensitive indicator of past environmental conditions than measurements of total luminescence.
Received: 18 March 1999 / Accepted: 20 December 1999 相似文献
10.
The variable number of tandem repeat (VNTR) marker located at the 3′-end of the phenylalanine hydroxylase (PAH) gene, PAHVNTR marker, is commonly used in carrier detection and prenatal diagnosis of the PKU disease. During the molecular
diagnosis of the disease, an artifact band associated with the PAHVTNR marker was frequently observed. Analysis of genotyping
data from nine trios families indicated that in heterozygote individuals, the observed stutter (artifact) bands at PAHVNTR
marker were minor bands with one repeat sequence shorter than the upper main bands. More investigations using sequencing revealed
that the artifact band was associated with VNTRs including seven or higher core repeats. In statistical analysis, 75% of the
studied heterozygote individuals represented PCR artifact band. The presence of the artifact band associated with PAHVNTR
marker highlights a serious alarm risk of possible technical misdiagnosis in the application of the PAHVNTR marker in carrier
detection and prenatal diagnosis of the PKU disease. 相似文献
11.
Arvind Misra Pratibha Dwivedi Mohammad Shahid 《Russian Journal of Bioorganic Chemistry》2009,35(1):62-67
A modified fluorescent probe UFAA AAT CTC CGC CGC was synthesized using the nucleoside analogue 3′-O-(N,N′-diisopropylamino-2-cyanoethoxyphosphinyl)-5′-O-(4,4′-dimethoxytrityl)-2′-O-(dansyl-1-sulfonamidohexylaminocarbonyl)uridine for hybridization studies with perfectly matched (U/A) complementary DNA
and with a DNA strand having similar G-rich telomeric units at their 3′-ends. Data on the thermal stability and decrease in
fluorescence intensity due to the presence of dG units clearly demonstrated the potential application of this approach in
DNA diagnostics in homogeneous hybridization assays.
The text was submitted by the authors in English. 相似文献
12.
Degradation experiment of model polychlorinated biphenyl (PCB) compound 4,4′-dichlorobiphenyl (4,4′-DCB) and its metabolites by the white-rot fungus Phanerochaete chrysosporium and newly isolated 4,4′-DCB-degrading white-rot fungus strain MZ142 was carried out. Although P. chrysosporium showed higher degradation of 4,4′-DCB in low-nitrogen (LN) medium than that in potato dextrose broth (PDB) medium, Phanerochaete sp. MZ142 showed higher degradation of 4,4′-DCB under PDB medium condition than that in LN medium. The metabolic pathway of 4,4′-DCB was elucidated by the identification of metabolites upon addition of 4,4′-DCB and its metabolic intermediates. 4,4′-DCB was initially metabolized to 2-hydroxy-4,4′-DCB and 3-hydroxy-4,4′-DCB by Phanerochaete sp. MZ142. On the other hand, P. chrysosporium transformed 4,4′-DCB to 3-hydroxy-4,4′-DCB and 4-hydroxy-3,4′-DCB produced via a National Institutes of Health shift of 4-chlorine. 3-Hydroxy-4,4′-DCB was transformed to 3-methoxy-4,4′-DCB; 4-chlorobenzoic acid; 4-chlorobenzaldehyde; and 4-chlorobenzyl alcohol in the culture with Phanerochaete sp. MZ142 or P. chrysosporium. LN medium condition was needed to form 4-chlorobenzoic acid, 4-chlorobenzaldehyde, and 4-chlorobenzyl alcohol from 3-hydroxy-4,4′-DCB, indicating the involvement of secondary metabolism. 2-Hydroxy-4,4′-DCB was not methylated. In this paper, we proved for the first time by characterization of intermediate that hydroxylation of PCB was a key step in the PCB degradation process by white-rot fungi. 相似文献
13.
T. C. Tricas J. G. New 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,182(1):89-101
Elasmobranch fishes localize weak electric sources at field intensities of <5 ηV cm−1, but the response dynamics of electrosensory primary afferent neurons to near threshold stimuli in situ are not well characterized.
Electrosensory primary afferents in the round stingray, Urolophus halleri, have a relatively high discharge rate, a regular discharge pattern and entrain to 1-Hz sinusoidal peak electric field gradients
of ≤20 ηV cm−1. Peak neural discharge for units increases as a non-linear function of stimulus intensity, and unit sensitivity (gain) decreases
as stimulus intensity increases. Average peak rate-intensity encoding is commonly lost when peak spike rate approximately
doubles that of resting, and for many units occurs at intensities <1 μV cm−1. Best neural sensitivity for nearly all units is at 1–2 Hz with a low-frequency slope of 8 dB/decade and a high-frequency
slope of −23 dB/decade. The response characteristics of stingray electrosensory primary afferents indicate sensory adaptations
for detection of extremely weak phasic fields near 1–2 Hz. We argue that these properties reflect evolutionary adaptations
in elasmobranch fishes to enhance detection of prey, communication and social interactions, and possibly electric-mediated
geomagnetic orientation.
Accepted: 20 June 1997 相似文献
14.
The GH gene cluster in marmoset, Callithrix jacchus, comprises eight GH-like genes and pseudogenes and appears to have arisen as a consequence of gene duplications occurring
independently of those leading to the human GH gene cluster. We report here the complete sequence of the marmoset GH gene
locus, including the intergenic regions and 5′ and 3′ flanking sequence, and a study of the multiple GH-like genes of an additional
New World monkey (NWM), the white-fronted capuchin, Cebus albifrons. The marmoset sequence includes 945 nucleotides (nt) of 5′ flanking sequence and 1596 nt of 3′ flanking sequence that are
“unique”; between these are eight repeat units, including the eight GH genes/pseudogenes. The breakpoints between these repeats
are very similar, indicating a regular pattern of gene duplication. These breakpoints do not correspond to those found in
the much less regular human GH gene cluster. This and phylogenetic analysis of the repeat units within the marmoset gene cluster
strongly support the independent origin of these gene clusters, and the idea that the episode of rapid evolution that occurred
during GH evolution in primates preceded the gene duplications. The marmoset GH gene cluster also differs from that of human
in having fewer and more evenly distributed Alu sequences (a single pair in each repeat unit) and a “P-element” upstream of every gene/pseudogene. In human there is no P-element
upstream of the gene encoding pituitary GH, and these elements have been implicated in placental expression of the other genes
of the cluster. The GH gene clusters in marmoset and capuchin appear to have arisen as the consequence of a single-gene duplication
event, but in capuchin there was then a remarkable expansion of the GH locus, giving at least 40 GH-like genes and pseudogenes.
Thus even among NWMs the GH gene cluster is very variable.
[Reviewing Editor: Nicolas Galtier] 相似文献
15.
Jack Farineau 《Photosynthesis research》1993,36(1):25-34
Characteristics of thermoluminescence (TL) glow curves were studied in thylakoids (isolated from pea leaves) or in intact pea leaves after an exposure to very high light for 2 min in the TL device. The inhibition of photosynthesis was detected as decreases of oxygen evolution rates and/or of variable fluorescence.In thylakoids exposed to high light, then dark adapted for 5 min, a flash regime induced TL glow curves which can be interpreted as corresponding to special B bands since: 1) they can be fitted by a single B band (leaving a residual band at –5°C) with a lower activation energy and a shift of the peak maximum by –5 to –6°C and, 2) the pattern of oscillation of their amplitudes was normal with a period of 4 and maxima on flashes 2 and 6. During a 1 h dark adaptation, no recovery of PS II activity occurred but the shift of the peak maximum was decreased to –1 to –2°C, while the activation energy of B bands increased. It is supposed that centers which remained active after the photoinhibitory treatment were subjected to reversible and probably conformational changes.Conversely, in intact leaves exposed to high light and kept only some minutes in the dark, TL bands induced by a flash regime were composite and could be deconvoluted into a special B band peaking near 30°C and a complex band with maximum at 2–5°C. In the case of charging bands by one flash, this low temperature band was largely decreased in size after a 10 min dark adaptation period; parallely, an increase of the B band type component appeared. Whatever was the flash number, bands at 2–5°C were suppressed by a short far red illumination given during the dark adaptation period and only remained a main band a 20°C; therefore, the origin of the low temperature band was tentatively ascribed to recombinations in centers blocked in state S2QA
–QB
2–. In vivo, the recovery of a moderately reduced state in the PQ pool, after an illumination, would be slow and under the dependence of a poising mechanism, probably involving an electron transfer between cytosol and chloroplasts or the so-called chlororespiration process.Abbreviations Ea-
activation energy
- FR-
far-red
- MV-
methylviologen
- pBQ-
p-benzoquinone
- PQ-
plastoquinone
- PS II-
Photosystem II
- QA-
primary quinone electron acceptor of PS II
- QB-
secondary quinone electron acceptor of PS II
- TL-
thermoluminescence 相似文献
16.
Jinwook Seo Suk Weon Kim Jonghyun Kim Hyun Wook Cha Jang R. Liu 《Journal of Plant Biology》2007,50(6):626-631
Theflavonoid 3′,5′-hydroxylase (F3′,5′H) gene, derived from petunia, was introduced into chrysanthemum tissues by Agrobacterium-mediated genetic transformation.
Cotyledon expiants were co-cultured withA. tumefaciens LBA 4404 harboring the vector pMBP that carriesF3′,5′H under the control of the CaMV 35S promoter andnptll as a selectable marker gene. After 72 h of co-cultivation, the expiants were placed on an MS medium supplemented with 4 mg
L-1 BA, 0.1 mg L-1 NAA, 400 mg L-1 carbenicillin, and 100 mg L-1; kanamycin. After 4 weeks, kanamycin-resistant adventitious shoots had developed at a frequency of 6.3%. These shoots were
then rooted and acclimatized in potting soil. Integration ofF3′,5′H into the plant genome was confirmed by Southern blot analysis. Flower buds that had red petals did not differ between the
transgenic and the wild-type plants. However, petal color did change from red to bright orange to yellow when the buds developed
into fully opened flowers on the transgenics. Spectrometric analysis revealed that the content of flavonoid compounds was
more rapidly reduced in the transgenic petals as floral development proceeded. RT-PCR analysis showed thatF3′,5′H andflavonoid 3′hydroxylase (F3′H) were expressed simultaneously in the transgenic plants. Therefore, we suggest that this more rapid change in petal color
results from 1) competition between levels of transgenicF3′,5′H and endogenousF3′H, each of which uses the same substrate in the flavonoid biosynthetic pathway and 2) the intrinsic substrate specificity of
chrysanthemumDFR (dihydroflavonol 4-reductase). 相似文献
17.
The cortical medial superior temporal area (MST) is essential for the normal execution of smooth pursuit eye movements. Many
pursuit-related neurons (visual-tracking neurons = VT neurons) in the lateral part of area MST (MSTl) are responsive to retinal
image slip (r) as well as to eye (e) and head velocity (h) with similar preferred directions (isodirectionality). We show, by running a connectionist network with VT neuron-like elements, that an assembly of MSTl-VT neurons is able to
reconstruct target motion in world-centered coordinates (t′). When t′ is fed into a subsequent model stage, converting t′ into gaze velocity (g′) with varying contributions of e and h, the overall model is able to account for many of the salient properties of visually guided pursuit including the consequences
of MSTl lesions. However, the analysis of the MSTl network also clearly indicates that isodirectionality is not a prerequisite
for its performance. The investigation of a second model suggests that isodirectionality indeed does not result from functional
but from developmental constraints. This second model is a connectionist network with hidden units, which similar to MSTl-VT
neurons receive input from modality specific units encoding retinal slip, eye and head velocity. After training this network
to offer t′ as output, two subsets of hidden units emerged, one exhibiting isodirectionality, but not the other. Since only isodirectional
hidden units contributed to the flow of information, the preponderance of isodirectional MSTl-VT neurons might be the result
of developmental pruning, eliminating the second group.
Received: 17 April 1998 / Accepted in revised form: 28 July 1998 相似文献
18.
V. V. Shubin M. Roegner E. El-Mohsnawy I. V. Terekhova E. Schlodder N. V. Karapetyan 《Applied Biochemistry and Microbiology》2010,46(3):274-281
Circular dichroism (CD) spectra of photosystem I (PSI) complexes of the cyanobacteria Thermosynechococcus elongatus, Arthrospira platensis and Synechocystis sp. PCC 6803 were studied. CD spectra of dark-adapted PSI trimers and monomers, measured at 77 K, show common bands at 669–670(+),
673(+), 680(−), 683–685(−), 696–697(−), 702(−) and 711(−) nm. The intensities of these bands are species specific. In addition,
bands at 683–685(−) and 673(+) nm differ in intensity for trimeric and monomeric PSI complexes. CD difference spectra (P700+–P700) of PSI complexes at 283 K exhibit conservative bands at 701(−) and 691(+) nm due to changes in resonance interaction
of chlorophylls in the reaction center upon oxidation of P700. Additional bands are observed at 671(−), 678(+), 685(−), 693(−)
nm and in the region 720–725 nm those intensities correlate with intensities of analogous bands of antenna chlorophylls in
dark-adapted CD spectra. It is suggested that the variability of CD difference spectra of PSI complexes is determined by changes
in resonance interaction of reaction center chlorophylls with closely located antenna chlorophylls. 相似文献
19.
An attempt was made to explore the genotyping of Trichophyton rubrum (T. rubrum) and the relationship between genotype and geographical origin using ribosomal restriction endonuclease polymorphic analysis.
The total DNA was extracted by cetyltrimethyl ammonium bromide (CTAB). The probe was amplified from part of the 18S, ITSI,
5.8S, and ITSII region of T. rubrum standard strain with the universal fungal primers NS5 [5′-AACTT AAAGG AATTG ACGGA AG-3′] and ITS4 [5′-TCCTC CGCTT ATTGA TATGC-3′].
The genomic DNA of 49 clinical T. rubrum isolates digested by EcoR1 were hybridized with this probe, and the hybridization patterns were used as the basis of genotyping. Of the data from
49 strains of T. rubrum studied (21 from Nanjing, 26 from Dalian, and two from Beijing), 20 individual patterns (DNA Type A–T) were identified, among
which Type A–C accounted for 48.98% of all the strains. The DNA patterns of Nanjing strains were represented by three bands,
those of Dalian strains were represented by four bands. The DNA typing of T. rubrum by Southern blotting was highly sensitive and highly distinguishable. The DNA patterns of Nanjing strains were obviously
different from those of Dalian strains. 相似文献
20.
《Luminescence》2002,17(3):135-140
The thermoluminescence (TL) parameters in the intact leaves and the thylakoids isolated from leaves of NaCl treated seedlings showed different patterns of change. NaCl treatment brings about a destabilization of QA and QB, leading to a decrease in Q and B bands in the leaves. However, the Q and B band intensity of isolated thylakoids increased in NaCl‐treated seedlings. The differences in the TL intensities are described as the action of NaCl on the density of quinones per unit leaf area and on chlorophyll units in isolated thylakoids. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献