共查询到20条相似文献,搜索用时 31 毫秒
1.
Photochemical degradation of chromophoric-dissolved organic matter exposed to simulated UV-B and natural solar radiation 总被引:11,自引:0,他引:11
Photochemical degradation of chromophoric-dissolved organic matter (CDOM) by UV-B radiation decreases CDOM absorption in the
UV region and fluorescence intensity, and alters CDOM composition. CDOM absorption, fluorescence, and the spectral slope indicating
the CDOM composition were studied using 0.22-μm-filtered samples of Meiliang Bay water from Lake Taihu that were exposed to
short-term (0–12 h) simulated UV-B radiation and long-term (0–12 days) natural solar radiation in summer. CDOM absorption
coefficient and fluorescence decreased with increasing exposure time, which relates to the amounts of absorbed light energy.
The decreases of CDOM absorption and normalized fluorescence corresponded to first order kinetics reactions. Different decreases
of CDOM absorption and fluorescence at different wavelengths suggested that the composition of CDOM changed when it absorbed
ultraviolet radiation. Photochemical degradation increased the spectral slope during 275–295 nm region (S
275–295) but decreased the spectral slope during 275–295 nm region (S
350–400). The slope ratio S
R (S
275–295:S
350–400) increased in the photochemical process, which could be used as an indicator of photobleaching and composition change of
CDOM. Our results show that photochemical degradation is important in the cycling of CDOM, which indicated change in the composition
of CDOM.
Handling editor: Luigi Naselli-Flores 相似文献
2.
Ignacio G. Galindo 《Bulletin of mathematical biology》1967,29(4):677-690
A physical model that incorporates all the experimental information on the formation of the visual pigment rhodopsin is presented.
The visual pigments consist of a chromophore bound to an appropriate protein. Thus rhodopsin (λm 505 mμ) is formed by a Schiff’s base linkage C19H27CH=NH+-opsin (λm 440 mμ) between 11-cis retinal (λm 380 mμ) and the protein opsin (λm 280 mμ). It is found that there exists a red shift in the spectrum of rhodopsin from the Schiff’s base. The model brings
an explanation for this red shift. It is shown that such a shift may be due to a charge transfer process (R. S. Mulliken,J. Am. Chem. Soc.,74, 811–824, 1952) between an electron at the double bond of carbons C11−C12 and an atomic orbital of the sulphur present in cysteine. This provides an explanation of the presence of SH-groups in the
protein after the absorption of light. A one-electron approximation is used and the dipole momentμ
NV
; hence, the oscillator strengthf of the transitionNV is estimated and compared with the experimentally determined extinction coefficient ∈m by mixing 3.5×10−3 M of 11-cis retinal with 8.3×10−5 M of cysteine at pH ranges 6 through 8. Reasonable agreement is found. Solvent, concentration and temperature dependence
are shown also. 相似文献
3.
Makoto Mizuno 《Journal of plant research》1982,95(4):349-357
Cocconeis scutellum var.ornata Grun. from three localities of Japan was studied. The striation density in 10 μm showed a marked tendency to increase with
the decrease of the valve length in both raphe and rapheless valves, and this tendency did not vary with locality or environmental
condition. The striation densities of rapheless valves were 4–6 in 10 μm for a valve length of 40μm, 4–6.5 for 30 μm, 6–9
for 20μm and 6.5–11 for 15μm. Those of raphe valves were 10–11 in 10μm for a valve length of 40μm, 10–12 for 30μm, 11–14.5
for 20μm and 12.5–17 for 15μm.
According to the range of changing value in striation density obtained by the present study,C. scutellum var.schmidti Frenguelli andC. japonica Schmidt are identical withC. scutellum var.ornata.
Dedicated to Prof. Munenao Kurogi on the occasion of his academic retirement.
Culture experiment in the present study was undertaken at the Institute of Algological Research, Faculty of Science, Hokkaido
University at Muroran. 相似文献
4.
A small blue-light beam (50 μm in diam) was used to examine light-growth response and phototropism inPilobolus crystallinus sporangiophores. Continuous irradiation by microbeam of a region 100–150 μm from the apex promoted the growth of a dark-adapted
sporangiophore for about 15 min after a lag period of 1–2 min. After the promotion, the growth rate fell below that before
the irradiation. Irradiation of the apex of sporangiophore slightly promoted the growth but strongly inhibited the growth
after the promotion. A smaller light beam (10 μm in diam) applied continuously at grazing incidence along one side of the
sporangiophore caused bending toward the shaded side, implying that the irradiated side grew more rapidly than the shaded
side and that the lens effect is involved in the phototropism of young sporangiophores ofP. crystallinus. The involvement of the lens effect was confirmed by the fact that a carotenoid-less mutant was 1.5–2 times more sensitive
to unilateral blue light than the wild type, probably because of a smaller intracellular light attenuation during passage
through the mutant cell. 相似文献
5.
Abiraj K. Prakasha Gowda A. S. Channe Gowda D. 《International journal of peptide research and therapeutics》2002,9(6):283-290
Summary Bactenecin7, a cationic antibacterial peptide, contains a repeating region of Xaa-Pro-Arg-Pro (Xaa=hydrophobic residues).
A series of peptides, Xaa-Pro-Arg-Pro (Xaa=D-Ala, D-Leu, D-Val, D-Phe and D-Lys) were synthesized to investigate the effect
of change ofN-terminal configuration on antimicrobial activity. The conformational preferences of these peptides in water and TFE were
examined by circular dichroism. All the synthetic peptides with D-amino acid substitution atN-terminal showed potent antifungal activity againstAspergillus niger, Aspergillus flavus andFusarium moniliforme at the concentration level of 8–10 μg ml−1. But the same tetrapeptides were unable to kill or suppress the growth of gram-negative and gram-positive bacteria such asEscherichia coli HB101,Pseudomonas aeruginosa, Klebsiella pneumoniae andStaphylococcus aureus even at the concentration level of 400 μg ml−1. The present study reveals that the change of configuration at theN-terminal of tetrapeptide has negative impact on antibacterial activity but enhanced antifungal activity. 相似文献
6.
Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium
pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal
infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated
by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected
almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B1 was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus. 相似文献
7.
Anju Arora Sudhir Saxena Dinesh Kumar Sharma 《World journal of microbiology & biotechnology》2006,22(2):97-100
Azolla, an aquatic fern is ideal candidate for exploitation in constructed wetlands for treating metal-contaminated wastewaters. This study demonstrates the potential of Azolla spp. namely A. microphylla, A. pinnata and A.␣filiculoides to tolerate Cr ions in the growth environment and bioconcentrate them. These species could grow in presence of up to 10 μg ml−1 Cr and showed biomass production 30–70% as compared to controls. Nitrogenase activity was not affected at 1–5 μg ml−1 but at higher concentrations it diminished. There was no growth at higher concentrations of chromium. However, the necrosed biomass harvested from treatments containing higher concentrations of chromium, accumulated Cr to the levels 5000–15,000 μg g−1. At increased levels of Cr, the metal was accumulated in higher amount in dry biomass. Bioconcentration Factor (BCF) ranged between 243 and 4617 for the three species. A. microphylla showed highest bioconcentration potential. Thus, these Azolla spp. can be exploited for treatment of tannery and other Cr contaminated wastewaters. 相似文献
8.
Wester RC Hartway T Maibach HI Schell MJ Northington DJ Culver BD Strong PL 《Biological trace element research》1998,66(1-3):111-120
Literature from the first half of this century reports concern for toxicity from topical use of boric acid, but assessment
of percutaneous absorption has been impaired by lack of analytical sensitivity. Analytical methods in this study included
inductively coupled plasmamass spectrometry which now allows quantitation of percutaneous absorption of10B in10B-enriched boric acid, borax and disodium octaborate tetrahydrate (DOT) in biological matrices.
In vitro human skin percent doses of boric acid absorbed were 1.2 for a 0.05% solution, 0.28 for a 0.5% solution, and 0.70
for a 5.0% solution. These absorption amounts translated into flux values of, respectively, 0.25, 0.58, and 14.58 μg/cm2/h, and permeability constants (K
p
) of 5.0 x 10-4, 1.2 x 10-4, and 2.9 x 10-4 cm/h for the 0.05%, 0.5%, and 5.0% solutions. The above in vitro doses were at infinite, 1000 μL/cm2 volume. At 2 μL/cm2 (the in vivo dosing volume), flux decreased some 200-fold to 0.07 μg/cm2/h andK
p
of 1.4 x 10-6 cm/h, while percent dose absorbed was 1.75%.
Borax dosed at 5.0%/1000 μL/cm2 had 0.41 percent dose absorbed, flux at 8.5 μg/cm2/h, andK
p
was 1.7 x 10-4 cm/h. Disodium octaborate tetrahydrate (DOT) dosed at 10%/1000 μL/cm2 was 0.19 percent dose absorbed, flux at 7.9 μg/cm2/h, andK
p
was 0.8 x ICH cm/h. These in vitro results from infinite doses (1000 μL/cm2) were a 1000-fold greater than those obtained in the companion in vivo study. The results from the finite (2 μL/cm2) dosing were closer (10-fold difference) to the in vivo results. General application of infinite dose percutaneous absorption
values for risk assessment is questioned by these results. 相似文献
9.
Investigation of the life history of corals is hampered by an inability to identify early recruits. In this study, the pattern
of formation and morphology of the juvenile skeletons of three laboratory-reared pocilloporids, Seriatopora hystrix, Stylophora pistillata and Pocillopora damicornis, were compared to determine whether they could be reliably distinguished. The pattern of skeleton formation, including the
origin and structure of the septa, columella and corallite wall was similar in all species. Following the completion of the
primary corallite wall after 4–5 days, these species could be identified by differences in the diameter of the primary corallite.
The mean diameter (±SE) of each species differed markedly: S. hystrix 400 ± 2.7 μm, range 325–450 μm; S. pistillata 505 ± 3.5 μm, range 400–550 μm; P. damicornis 697 ± 7.5 μm, range 492–885 μm. Values for the primary corallite diameter overlapped in only 3% of samples, demonstrating
the potential utility of this feature as a tool for classifying recruits obtained from the field.
Accepted: 4 January 2000 相似文献
10.
Soltani F Mosaffa F Iranshahi M Karimi G Malekaneh M Haghighi F Behravan J 《Cell biology and toxicology》2009,25(3):291-296
The protective properties of a prenylated coumarin, umbelliprenin (UMB), on the human lymphocytes DNA lesions were tested.
Lymphocytes were isolated from blood samples taken from healthy volunteers. DNA breaks and resistance to H2O2-induced damage were measured using a single-cell microgel electrophoresis technique under alkaline conditions (comet assay).
Human lymphocytes were incubated in UMB (10, 25, 50, 100, 200, and 400 μM) alone or a combination of different concentrations
of UMB (10, 25, 50, 100, 200, and 400 μM) and 25 μM H2O2. Untreated cells, ascorbic acid (AA; 25, 50, 100, 200, and 400 μM) and H2O2 (25 μM) were considered as negative control, positive control, and the standard antioxidant agent for our study, respectively.
Single cells were analyzed with “TriTek Cometscore version 1.5” software. The DNA damage was expressed as percent tail DNA.
UMB exhibited a concentration-dependent increase in protection activity against DNA damage induced by 25 μM H2O2 (from 67.28% to 39.17%). The antigenotoxic activity of AA, in the range 0–50 μM, was greater than that of UMB. However, no
significant difference (p > 0.05) in the protective activity was found between UMB and AA at concentrations of approximately higher than 50 μM. 相似文献
11.
Recombinant human progastrin6–80 binds two ferric ions with an apparent dissociation constant of 2.2 ± 0.1 μM [Baldwin (2004) Protein J 23:65–70]. The aims of the present study were to express fragments of recombinant procholecystokinin and to determine whether or not
they bound ferric ions. Recombinant rat and human procholecystokinin57–95 were expressed as glutathione S-transferase fusion proteins in E. coli. The fusion proteins were bound to glutathione-agarose, cleaved with thrombin, and purified by reverse phase HPLC. Recombinant
procholecystokinin57–95 did not bind to either the CCK1 or CCK2 receptor with high affinity. No change in absorption spectrum was observed on addition
of ferric ions, and analysis of the quenching of tryptophan fluorescence observed in the presence of ferric ions indicated
that binding to procholecystokinin57–95 was at least 40–fold weaker than the binding of ferric ions to progastrin6–80. 相似文献
12.
Jian Wu Henk Schat Rifei Sun Maarten Koornneef Xiaowu Wang Mark G. M. Aarts 《Plant and Soil》2007,291(1-2):167-180
Brassica rapa L. is an important vegetable crop in eastern Asia. The objective of this study was to investigate the genetic variation in
leaf Zn, Fe and Mn accumulation, Zn toxicity tolerance and Zn efficiency in B. rapa. In total 188 accessions were screened for their Zn-related characteristics in hydroponic culture. In experiment 1, mineral
assays on 111 accessions grown under sufficient Zn supply (2 μM ZnSO4) revealed a variation range of 23.2–155.9 μg g−1 dry weight (d. wt.) for Zn, 60.3–350.1 μg g−1 d. wt. for Fe and 20.9–53.3 μg g−1 d. wt. for the Mn concentration in shoot. The investigation of tolerance to excessive Zn (800 μM ZnSO4) on 158 accessions, by using visual toxicity symptom parameters (TSPs), identified different levels of tolerance in B. rapa. In experiment 2, a selected sub-set of accessions from experiment 1 was characterized in more detail for their mineral accumulation
and tolerance to excessive Zn supply (100 μM and 300 μM ZnSO4). In this experiment Zn tolerance (ZT) determined by relative root or shoot dry biomass varied about 2-fold. The same six
accessions were also examined for Zn efficiency, determined as relative growth under 0 μM ZnSO4 compared to 2 μM ZnSO4. Zn efficiency varied 1.8-fold based on shoot dry biomass and 2.6-fold variation based on root dry biomass. Zn accumulation
was strongly correlated with Mn and Fe accumulation both under sufficient and deficient Zn supply. In conclusion, there is
substantial variation for Zn accumulation, Zn toxicity tolerance and Zn efficiency in Brassica rapa L., which would allow selective breeding for these traits. 相似文献
13.
A simple and rapid method for multiple shoot formation in vitro from immature embryo axis explants of Carica papaya L. cvs. Honey Dew, Washington and Co2 is described. Multiple shoot regeneration was achieved by culture of the explants on
modified Murashige and Skoog (MS) medium supplemented either with thidiazuron (TDZ; 0.45–22.7 μM) or a combination of benzylaminopurine
(BAP; 0.2 – 8.84 μM) and naphthalene acetic acid (NAA; 0.5 – 2.64 μM). Highest frequency of shoot regeneration occurred on
medium supplemented either with 2.25 μM TDZ or a combination of BAP (4.4 μM) and NAA (0.5 μM). Composition of the basal media
influenced the frequency of multiple shoot initiation. Stunted shoots regenerated at 4.5 μM and higher concentrations of TDZ.
Such shoots could, however, be elongated by transfer to medium containing 5.7 μM GA3. Rooting of the regenerated shoots was achieved in presence of indolebutyric acid (IBA; 4.92 – 19.68 μM), however, least
response was in presence of 14.7 μM IBA. Rooted plants were hardened and transferred to pots.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Hilde Eggermont James M. Russell Georg Schettler Kay Van Damme Ilse Bessems Dirk Verschuren 《Hydrobiologia》2007,592(1):151-173
This study describes the physical and chemical properties of 17 Afroalpine lakes (>2 m deep) and 11 pools (<2 m deep) in the
Rwenzori mountains, Uganda-DR Congo, with the aim to establish the baseline conditions against which to evaluate future environmental
and biological changes in these unique tropical ecosystems, and to provide the foundation for lake-based paleoenvironmental
studies. Most Rwenzori lakes are located above 3,500 m elevation, and dilute (5–52 μS/cm specific conductance at 25°C) open
systems with surface in- and outflow. Multivariate ordination and pairwise correlations between environmental variables mainly
differentiate between (1) lakes located near or above 4,000 m (3,890–4,487 m), with at least some direct input of glacial
meltwater and surrounded by rocky catchments or alpine vegetation; and (2) lakes located mostly below 4,000 m (2,990–4,054
m), remote from glaciers and surrounded by Ericaceous vegetation and/or bogs. The former group are mildly acidic to neutral
clear-water lakes (surface pH: 5.80–7.82; Secchi depth: 120–280 cm) with often above-average dissolved ion concentrations
(18–52 μS/cm). These lakes are (ultra-) oligotrophic to mesotrophic (TP: 3.1–12.4 μg/l; Chl-a: 0.3–10.9 μg/l) and phosphorus-limited (mass TN/TP: 22.9–81.4). The latter group are mildly to strongly acidic (pH: 4.30–6.69)
waters stained by dissolved organic carbon (DOC: 6.8–13.6 mg/l) and more modest transparency (Secchi-disk depth: 60–132 cm).
Ratios of particulate carbon, particulate nitrogen and chlorophyll a in these lakes indicate that organic matter in suspension is primarily derived from the lakes’ catchments rather than aquatic
primary productivity. Since key features in the Rwenzori lakes’ abiotic environment are strongly tied to temperature and catchment
hydrology, these Afroalpine lake ecosystems can be expected to respond sensitively to climate change and glacier melting.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
15.
Photodynamic treatment by the cationic TMPyP photosensitizer was undertaken on the multiple antibiotic-resistant bacteria
Acinetobacter baumannii and Escherichia coli. Total eradication of the bacterial cultures was determined immediately after initiation of illumination when these bacteria
were treated with 5, 10, 15, 20-tetra (4-N methylpyridyl)porphine (TMPyP) at a concentration of 29.4 μmol/L and illuminated
by blue, green, or red light. Total eradication of both bacteria was obtained also after treatment of bacterial cultures with
3.7 μmol/L TMPyP and illumination with blue light (400–450 nm). On the other hand, an 8- or 16- to 20-fold higher light intensity,
respectively, was required for total eradication upon illumination with green (480–550 nm) or red light (600–700 nm). A 407-nm
blue light only 7 and 9 joules/cm2, respectively, was needed for total eradication of both bacteria even at a concentration of 3.7 μmol/L TMPyP. X-ray-linked
microanalysis demonstrated loss of potassium and a flood of sodium and chloride into the cells, indicating serious damage
to the cytoplasmic membrane. Transmission electron microscopy (TEM) revealed structural changes and damage to the membrane
of treated E. coli. In A. baumannii-treated cells, mesosomes and black dots that resemble aggregation of polyphosphate polymers could be seen. DNA breakage appeared
only after a long period of illumination, when the bacterial cell was no longer viable. It can be concluded that cytoplasmic
membrane damage and not DNA breakage is the major cause for bacterial death upon photosensitization.
Received: 13 October 2000 / Accepted: 17 November 2000 相似文献
16.
Inhibition of ribonuclease and protease activities in germinating rice seeds exposed to nickel 总被引:1,自引:0,他引:1
When the seeds of two rice cvs. Malviya-36 and Pant-12 were germinated up to 120 h in the presence of 200 and 400 μM NiSO4, a significant reduction in the germination of seeds occurred. Seeds germinating in the presence of 400 μM NiSO4 showed about 12–20% decline in germination percent, about 20–53% decline in lengths and about 8–34% decline in fresh weights
of roots and shoots at 120 h of germination. Ni2+ exposure of germinating seeds resulted in apparent increased levels of RNA, soluble proteins, and free amino acids in endosperms
as well as embryo axes. A 400 μM Ni2+ treatment led to about 58–101% increase in the level of soluble proteins and about 39–107% increase in the level of free
amino acids in embryo axes at 96 h of germination. Activities of ribonuclease and protease declined significantly with increasing
levels of Ni2+ treatment. Isoenzyme profile of RNase as revealed by activity staining indicated decline in the intensities of 3–4 preexisting
enzyme isoforms in embryo axes of both the rice cultivars and disappearance of one of the two isoforms in endosperms of cv. Pant-12 due to 400 μM Ni2+ treatment. Results suggest that the presence of high level of Ni2+ in the medium of germinating rice seeds serves as a stress factor resulting in decreased hydrolysis as well as delayed mobilization
of endospermic RNA and protein reserves and causing imbalance in the level of biomolecules like RNA, proteins, and amino acids
in growing embryo axes. These events would ultimately contribute to decreased germination of rice seeds in high Ni2+ containing environment. 相似文献
17.
Vishal Gupta Manoj Kumar Puja Kumari C. R. K. Reddy Bhavanath Jha 《Journal of applied phycology》2011,23(2):209-218
This study reports on the optimization of protoplast yield from two important tropical agarophytes Gracilaria dura and Gracilaria verrucosa using different cell-wall-degrading enzymes obtained from commercial sources. The conditions for achieving the highest protoplast
yield was investigated by optimizing key parameters such as enzyme combinations and their concentrations, duration of enzyme
treatment, enzyme pH, mannitol concentration, and temperature. The significance of each key parameter was also further validated
using the statistical central composite design. The enzyme composition with 4% cellulase Onozuka R-10, 2% macerozyme R-10,
0.5% pectolyase, and 100 U agarase, 0.4 M mannitol in seawater (30‰) adjusted to pH 7.5 produced the highest protoplast yields
of 3.7 ± 0.7 × 106 cells g−1 fresh wt for G. dura and 1.2 ± 0.78 × 106 cells g−1 fresh wt for G. verrucosa when incubated at 25°C for 4–6 h duration. The young growing tips maximally released the protoplasts having a size of 7–15 μm
in G. dura and 15–25 μm in G. verrucosa, mostly from epidermal and upper cortical regions. A few large-size protoplasts of 25–35 μm, presumably from cortical region,
were also observed in G. verrucosa. 相似文献
18.
Production of flavour compounds by yogurt starter cultures 总被引:5,自引:0,他引:5
D Beshkova E Simova G Frengova Z Simov 《Journal of industrial microbiology & biotechnology》1998,20(3-4):180-186
The present work studied the production of carbonyl compounds and saturated volatile free fatty acids by pure cultures of
Streptococcus thermophilus and Lactobacillus bulgaricus, and by starter cultures for Bulgarian yogurt during cultivation and cooling. The mixed cultures formed volatile aromatic
compounds more actively than the pure cultures. A guiding factor in the preparation of the starter cultures was the biochemical
activity of Lactobacillus bulgaricus in synthesizing the major carbonyl compounds, acetaldehyde, diacetyl and the volatile fatty acids C2–C10. The activity of the yogurt cultures in synthesizing carbonyl compounds was at its highest during milk coagulation and cooling,
up to 7 h. However, maximum concentration was reached by 22–31 h. In the cooled 22–h starter cultures, acetaldehyde predominated
(1415.0–1734.2 μg per 100 g) followed by diacetyl (165.0–202.0 μg per 100 g), acetoin (170.0–221.0 μg per 100 g), acetone
(66.0–75.5 μg per 100 g), ethanol (58.0 μg per 100 g), and butanone-2 (3.6–3.8 μg per 100 g). The thermophilic streptococcus
and lactobacillus cultures, and the starter cultures contained predominantly acetic, butyric and caproic acids.
Received 19 June 1997/ Accepted in revised form 10 January 1998 相似文献
19.
In this study, we evaluated how cadmium inhibitory effect on photosystem II and I electron transport may affect light energy
conversion into electron transport by photosystem II. To induce cadmium effect on the photosynthetic apparatus, we exposed
Chlamydomonas reinhardtii 24 h to 0–4.62 μM Cd2+. By evaluating the half time of fluorescence transients O–J–I–P at different temperatures (20–30°C), we were able to determine
the photosystem II apparent activation energies for different reduction steps of photosystem II, indicated by the O–J–I–P
fluorescence transients. The decrease of the apparent activation energies for PSII electron transport was found to be strongly
related to the cadmium-induced inhibition of photosynthetic electron transport. We found a strong correlation between the
photosystem II apparent activation energies and photosystem II oxygen evolution rate and photosystem I activity. Different
levels of cadmium inhibition at photosystem II water-splitting system and photosystem I activity showed that photosystem II
apparent activation energies are strongly dependent to photosystem II donor and acceptor sides. Therefore, the oxido-reduction
state of whole photosystem II and I electron transport chain affects the conversion of light energy from antenna complex to
photosystem II electron transport. 相似文献
20.
A. E. Solovchenko I. Khozin-Goldberg Z. Cohen M. N. Merzlyak 《Journal of applied phycology》2009,21(3):361-366
The relationships between pigment (carotenoid and chlorophyll) content with accumulation of total fatty acids (TFA) and arachidonic
acid (AA) were studied in the green microalga Parietochloris incisa (Trebouxiophyceae, Chlorophyta) grown under different PFDs (35, 200, and 400 μmol photons m−2 s−1) and nitrogen availabilities. The growth of P. incisa under higher light and nitrogen deficiency was accompanied by accumulation of FA, an increase in carotenoid and a decline
in chlorophyll content. It was found that the carotenoid-to-chlorophyll ratio (but not the individual pigment content) correlates
closely with the volumetric content of both TFA and AA. Analysis of scattering-compensated absorption spectra of P. incisa suspensions revealed their tight relationship in the blue-green range of the spectrum with the carotenoid-to-chlorophyll
ratio, TFA, and AA content. These findings allowed the development of algorithms for the non-destructive assay of TFA and
AA in cell suspensions in the ranges of 0.09–3.04 and 0.04–1.7 μg mL−1, with accuracy of 0.06 and 0.01 μg mL−1, respectively, via analytically measured carotenoid-to-chlorophyll ratio and using the ratio of absorption coefficients at
510 and 678 nm, with accuracy of 0.07 and 0.02 μg mL−1, respectively. The feasibility of obtaining essential spectral information concerning the physiological condition of P. incisa using a standard spectrophotometer is also shown. 相似文献