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1.
To enhance the use of cellobiose by a recombinant Sachharomyces cerevisiae, the expressed -glucosidase that hydrolyzes cellobiose was stabilized using a surface-display system. The C-terminal half of -agglutinin was used as surface-display motif for the expression of -glucosidase in the cell wall. The surface-displayed -glucosidase had a half-life time (t
1/2) of 100 h in acidic culture broth conditions, while secreted -glucosidase had a t
1/2 of 60 h. With such stabilization of -glucosidase, the surface-engineered S. cerevisiae utilized 7.5 g cellobiose l–1 over 60 h, while S. cerevisiae secreting -glucosidase into culture broth used 5.8 g cellobiose l–1 over the same period. 相似文献
2.
Thermotolerance of photosystem II (PSII) in leaves of salt-adapted Artemisia anethifolia L. plants (100–400 mM NaCl) was evaluated after exposure to heat stress (30–45°C) for 30 min. After exposure to 30°C, salt adaptation had no effects on the maximal efficiency of PSII photochemistry (Fv/Fm), the efficiency of excitation capture by open PSII centers (Fv/Fm), or the actual PSII efficiency (PSII). After pretreatment at 40°C, there was a striking difference in the responses of Fv/Fm, Fv/Fm and PSII to heat stress in non-salt-adapted and salt-adapted leaves. Leaves from salt-adapted plants maintained significantly higher values of Fv/Fm, Fv/Fm and PSII than those from non-salt-adapted leaves. The differences in Fv/Fm, Fv/Fm and PSII between non-salt-adapted and salt-adapted plants persisted for at least 12 h following heat stress. These results clearly show that thermotolerance of PSII was enhanced in salt-adapted plants. This enhanced thermotolerance was associated with an improvement in thermotolerance of the PSII reaction centers, the oxygen-evolving complexes and the light-harvesting complex. In addition, we observed that after exposure to 42.5°C for 30 min, non-salt-adapted plants showed a significant decrease in CO2 assimilation rate while in salt-adapted plants CO2 assimilation rate was either maintained or even increased to some extent. Given that photosynthesis is considered to be the physiological process most sensitive to high-temperature damage and that PSII appears to be the most heat-sensitive part of the photosynthetic apparatus, enhanced thermotolerance of PSII may be of significance for A. anethifolia, a halophyte plant, which grows in the high-salinity regions in the north of China, where the air temperature in the summer is often as high as 45°C. 相似文献
3.
The Effects of Hypoxia on Three Sympatric Shark Species: Physiological and Behavioral Responses 总被引:1,自引:0,他引:1
Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4mg l–1), shark routine swimming speed averaged 25.5 and 31.0cm s–1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0cm s–1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O2kg–1h–1 for S. tiburo, 437.2mg O2kg–1h–1 for C. acronotus, and 161.4mg O2 kg–1 h–1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged 1.0cm whereas M. norrisi gillbeats averaged 56.0 beats min–1. Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39cm s–1, 2.5–3.0cm and 496 and 599mg O2 kg–1 h–1 under hypoxic conditions (2.5–3.4mg l–1), respectively. M. norrisi decreased swimming speeds to 16cm s–1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity. 相似文献
4.
K. Shimizu 《Biochemical genetics》1987,25(3-4):197-203
DNA polymorphism patterns linked to the A-globin gene were analyzed in healthy Japanese using four different restriction endonucleases. The chromosomes with the A-globin gene were mapped through an evaluation of the presence of seven different restriction sites (HincII 5 to ; HindIII in G and A; HincII in, and 3 to, 1; AvaII in ; Bam-HI 3 to ). Among 36 chromosomes analyzed, 20 chromosomes had a haplotype of [+–––––+]. Among 55 individuals examined, 7 possessed a homozygous haplotye of [+–––––+]. All Japanese with the AT-globin gene had a subhaplotype of [–++–+] 5 to the -globin gene. Their major haplotypes were [–++–+–+] and [–++–++–]. It was expected that the presence of the AT-globin gene in Japanese may be deduced from subhaplotypes 5 to the -globin gene. 相似文献
5.
The solid-state conformation of the first N-protected ornithine derivative has been established by X-ray analysis. The hydrochloride of N-(9-fluorenyl)methoxycarbonyl-L-ornithine crystallises as diethyl ether solvate. The backbone (0, , , 1) torsion angles are (174.9°, –84.0°, 145.9°, –171.0°). The conformation of the urethane amide bond is trans. The ornithine aliphatic side chain adopts preferred fully extended conformation which is stabilised by the hydrogen bonding of the –NH3
+ group to the diethyl ether molecule, carboxyl group and Cl- anions. 相似文献
6.
Zyakun A. M. Kosheleva I. A. Zakharchenko V. N. Kudryavtseva A. I. Peshenko V. A. Filonov A. E. Boronin A. M. 《Microbiology》2003,72(5):592-596
The study deals with a comparative analysis of the relative abundances of the carbon isotopes 12C and 13C in the metabolites and biomass of the Burkholderia sp. BS3702 and Pseudomonas putida BS202-p strains capable of utilizing aliphatic (n-hexadecane) and aromatic (naphthalene) hydrocarbons as sources of carbon and energy. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of Burkholderia sp. BS3702 on n-hexadecane (13C = –44.6 ± 0.2) were characterized by the values of 13CCO
2 = –50.2 ± 0.4, 13Cbiom = –46.6 ± 0.4, and 13Cexo = –41.5 ± 0.4, respectively. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of the same bacterial strain on naphthalene (13C = –21 ± 0.4) were characterized by the isotope effects 13CCO
2 = –24.1 ± 0.4, 13Cbiom = –19.2 ± 0.4, and 13Cexo = –19.1 ± 0.4, respectively. The possibility of using the isotope composition of metabolic carbon dioxide for the rapid monitoring of the microbial degradation of petroleum hydrocarbons in the environment is discussed. 相似文献
7.
J. Sybenga 《Genetica》1965,36(1):243-252
Whilst reliable estimates of chiasma frequencies can usually not be obtained, the probability (b) of a chromosome arm to be bound by at least one chiasma can often be determined. In the absence of interference this probability equals (1–e
–2), where 2 is the average chiasma frequency of the chromosome arm and the average crossover frequency or map length. In the presence of interference is shown to retain its genetic meaning as an additive metric that may describe the chromosome arm or other distinctive chromosome segment in terms of genetic recombination. It is a form of potential map length, comparable to, but numerically different from the regular map length. It is termed provisionally crossing-over potential.A chromosome with armsm andn with crossing-over potentials and will form ring bivalents with a frequency (1–e
–2).(1–e
–2); open bivalents with a frequency (1–e
–2).e
–2+(1–e
–2).e
–2; univalent pairs with a frequencye
–2.e
–2. Estimates of these frequencies yield equations from which and may be solved. In rye (Secale cereale) their ratio (q) is approximately two and differs from the mitotic arm length ratio of 1.4, indicating localization of chiasmata in the long arms.Graphs are given to show how, with constantq, the relation between the probabilitiesb
m
andb
n
of the two arms being bound changes with changing averageb.Data are presented on chiasma frequencies in M I, and compared with the frequencies expected in the absence of interference to give an impression of the degree of interference. Apparent fusion of chiasmata simulates interference. 相似文献
8.
Stepanenko I. Yu. Strakhovskaya M. G. Belenikina N. S. Nikolaev Yu. A. Mulyukin A. L. Kozlova A. N. Revina A. A. El'-Registan G. I. 《Microbiology》2004,73(2):163-169
The effects of C7-alkylhydroxybenzene (7-AHB) and p-hydroxyethylphenol (tyrosol), chemical analogs of microbial anabiosis autoregulators, on the viability of yeast cells under oxidative stress were investigated. The stress was caused by reactive oxygen species (ROS) produced under irradiation of cell suspensions using doses of 10–150 krad at an intensity of 194 rad/s or by singlet oxygen generated in cells photosensitized with chlorin e
6 (10 g/l). C7-AHB was found to exert a protective effect. The addition of 0.05–0.16 vol % of C7-AHB to cell suspensions 30 min before irradiation protected yeast cells from radiation (50 krad). The protective effect of C7-AHB manifested itself both in the preservation of cell viability during irradiation and in the recovery of their capacity to proliferate after irradiation. In our studies on photodynamic cell inactivation, the fact that the phenolic antioxidant C7-AHB protects cells from intracellular singlet oxygen was revealed for the first time. The analysis of difference absorption spectra of oxidized derivatives of C7-AHB demonstrated that the protective mechanism of 7-AHB involves the scavenging of ROS resulting from oxidative stress. The fact that tyrosol failed to perform a photoprotective function suggests that the antioxidant properties of microbial 7-AHB are not related to its chaperon functions. The results obtained make an important addition to the spectrum of known antioxidant and antistress effects of phenolic compounds. 相似文献
9.
The extracellular surface of the-chain ofTorpedo california acetylcholine receptor (AChR) was mapped for regions that are accessible to binding with antibodies against a panel of synthetic overlapping peptides which encompassed the entire extracellular parts of the chain. The binding of the antipeptide antibodies to membrane-bound AChR (mbAChR) and to isolated, soluble AChR. was determined. The specificity of each antiserum was narrowed down by determining the extent of its cross-reaction with the two adjacent peptides that overlap the immunizing peptide. With mbAChR, high antibody reactivity was obtained with antisera against peptides1–16,89–104,158–174,262–276, and388–408. Lower, but significant, levels of reactivity were obtained with antibodies against peptides67–82,78–93,100–115, and111–126. On the other hand, free AChR bound high levels of antibodies against peptides34–49,78–93,134–150,170–186, and194–210. It also bound moderate levels of antibodies against peptides262–276 and388–408. Low, yet significant, levels of binding were exhibited by antibodies against peptides45–60,111–126, and122–138. These binding studies, which enabled a comparison of the accessible regions in mbAChR and free AChR, revealed that the receptor undergoes considerable changes in conformation upon removal from the cell membrane. The exposed regions found here are discussed in relation to the functional sites of AChR (i.e., the acetylcholine binding site, the regions that are recognized by anti-AChR antibodies, T-cells and autoimmune responses and the regions that bind short and long neurotoxins).Abbreviations used AChR
acetylcholine receptor
-
mbAChR
membrane-bound AChR
- BSA
bovine serum albumin
- BTX
-bungarotoxin
- EAMG
experimental autoimmune myasthenia gravis
- MG
myasthenia gravis
- PBS
0.15 MNaCl in 0.01 M sodium phosphate buffer, pH 7.2. 相似文献
10.
Methods of intrinsic viscosity () and beam flow birefringence were used to study the effects of some single-charged ions (F–, Cl–, Br–, I–, NO–
2, NO–
3, ClO–
4, SCN–, CH3COO–) on the size and thermodynamic rigidity of a DNA molecule in aqueous solutions of sodium salts in a broad interval of ionic strength when temperature T is changed. It has been shown that the close interactions in a macromolecule and the resulting DNA persistent length a are independent of the type of the salt anion over the whole interval of . On the contrary, the specific volume of the DNA molecule in solution, proportional to the value, is quite sensitive to the anionic composition of the solvent, which is due to the effect of anions and their hydration on the long-range interactions in the macromolecule. The presence of polyatomic and halide anions is manifested differently in the value of DNA. Possible factors responsible for the observed effect and the role of structural alterations of water upon anion hydration are discussed. 相似文献
11.
Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3M of ammonium and between 0.77 and 6.21M of nitrate+nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: Vmax = 591.2molg–1h–1,
K
s=262.3M, nitrate+nitrite: V
max=12.9molg–1h–1, K
s=3.5M). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source. 相似文献
12.
Timothy S. Burcham Ida Sim Laurel M. Bolin Eric M. Shooter 《Neurochemical research》1991,16(6):603-612
The 7S NGF complex from the male mouse submaxillary gland consists of the , and subunits in the ratio 22. The (NGF) subunit contains all the known biolocial activity of 7S NGF. The and subunits are both members of glandular kallikrein gene family, yet only subunit has protease activity. The subunit plays a role in the processing of preproNGF to its mature form, while the role of the subunit is not yet understood. Despite the fact that 7S NGF has been extensively characterized, no other NGF complex has been characterized, nor have the or subunits been observed in tissues which express NGF. We have therefore purified and characterized the NGF complex from the submaxillary glands of the ratMastomys natalensis in order to more fully understand the roles of the and subunits. The NGF complex from M. natalensis contains subunits similar to those found in mouse 7S NGF. Although similar, there are significant differences between mouse and M. natalensis NGF complexes, especially in the degree of post-translational modification of the and NGF subunits, the expression of esterase activity and the ease with which the complexes dissociate. Evidence is presented that suggests that the NGF complex from M. natalensis may consist of subunits in the ratio 2. The amino acid sequence of the M. natalensis NGF suggests some, but not all, ways in which these differences arise.Special issue dedicated to Dr. Lawrence Austin 相似文献
13.
Summary The surface tension and foaminess of (a) unlimited, (b) substrate limited, and (c) oxygen transfer limited growth media of Hansenula polymorpha were measured using methanol, ethanol or glucose as a substrate.The time dependence of can be described by the Avrami-Überreiter relationship: log (2.3 log V)=n log t+log b, where V = (O – eq/(t – eq, and O, t and eq are at tM=0, tM=t and tM (equilibrium value).The constants n and b are functions of the fermentation time tF as long as the growth is unlimited but they are constant in the state of limited growth. With glucose substrate, the foaminess can be presented as a definite function of the time, tDG, which is necessary to attain eq. With alcohol as a substrate no definite (tDG) function was found.Symbols b
constant in Eq. (1)
- n
constant in Eq. (1)
- S
substrate concentration
- T
temperature
- tM
time h (measured from the beginning of the determination of the surface tension )
- tF
cultivation time h (measured from the time of inoculation)
- tDG
time (min) necessary to attain the equilibrium surface tension )
- X
dry biomass concentration (gl–1)
- V
(O – eq)/(t – eq)
- VS
equilibrium volume of the foam (cm3)
- VG
volumetric gas flow rate during the estimation of (cm3 s–1)
- vvm
volumetric gas flow rate with regard to the volume of the medium (min–1)
- wSG
superficial gas velocity (cm s–1)
- m
maximum specific growth rate (h–1)
-
VS/VG foaminess (s)
-
surface tension, mMm–1 (milli Newton m–1)
- O
at tM=0
- eq
equilibrium surface tension ( at tM)
- t
at tM=t
- HP
probes from Hansenula polymorpha cultivation
- NLG
non limited growth
- OTLG
oxygen transfer limited growth
- SLG
substrate limited growth 相似文献
14.
Rajkhowa R.C. Goswami Pranab Singh H.D. 《World journal of microbiology & biotechnology》2000,16(1):63-68
The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter
simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M
r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10–3g l–1h–1) could not adequately account for the rate of sterol uptake (72×10–3g l–1h–1) and the specific growth rate (56×10–3 h–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm–1), the sterol-grown cells had strong surface activity (40mNm–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells. 相似文献
15.
Effect of temperature and additional carbon sources on phenol degradation by an indigenous soil <Emphasis Type="Italic">Pseudomonad</Emphasis> 总被引:3,自引:0,他引:3
A new indigenous soil bacterium Pseudomonas sp. growing on phenol and on a mixture of phenol, toluene, o-cresol, naphthalene and 1,2,3-trimethylbenzene (1,2,3-TMB) was isolated and characterized. Phylogenetic analysis suggested its classification to Pseudomonadaceae family and showed 99.8% DNA sequence identity to Pseudomonas pseudoalcaligenes species. The isolate was psychrotroph, with growth temperatures ranging from ca. 0 to 40 °C. The GC–MS structural analysis of metabolic products of phenol degradation by this microorganism indicated a possible ortho cleavage pathway for high concentrations (over 200 mg L–1) of phenol. Biodegradation rates by this species were found to be three times more effective than those previously reported by other Pseudomonas strains. The effect of temperature on phenol degradation was studied in batch cultures at temperatures ranging from 10 to 40°C and different initial phenol concentrations (up to 500mgL–1). Above 300mgL–1 of initial phenol concentration no considerable depletion was recorded at both 10 and 40°C. Maximum degradation rates for phenol were recorded at 30°C. The biodegradation rate of phenol was studied also in the presence of additional carbon sources (o-cresol, toluene, naphthalene, 1,2,3-TMB) at the optimum growth temperature and was found significantly lower by a factor of eight in respect to the strong competitive inhibition between the substrates and the more available sources of carbon and energy. The Haldane equation =m S/(KS+S+S2/KI) was found to best fit the experimental data at the optimum temperature of 30°C than the Monod equation with kinetic constants m=0.27h–1, KS=56.70mgL–1, KI=249.08mgL–1. 相似文献
16.
Leaf gas exchange rates, predawn wp and daily minimum wm leaf water potentials were measured during a wet-to-dry season transition in pioneer (Jacaranda copaia, Goupia glabra andCarapa guianensis) and late stage rainforest tree species (Dicorynia guianensis andEperua falcata) growing in common conditions in artificial stands in French Guiana. Carbon isotope discrimination () was assessed by measuring the stable carbon isotope composition of the cellulose fraction of wood cores. The values were 2.7 higher in the pioneer species than in the late stage species. The calculated time integratedC
i values derived from the values averaged 281 mol mol–1 in the pioneers and 240 mol mol–1 in the late stage species. The corresponding time-integrated values of intrinsinc water-use efficiency [ratio CO2 assimilation rate (A)/leaf conductance (g)] ranged from 37 to 47 mmol mol–1 in the pioneers and the values were 64 and 74 mmol mol–1 for the two late stage species. The high values were associated—at least inJ. copaia—with high maximumg values and with high plant intrinsinc specific hydraulic conductance [Cg/(wm–wp], which could reflect a high competitive ability for water and nutrient uptake in the absence of soil drought in the pioneers. A further clear discriminating trait of the pioneer species was the very sensitive stomatal response to drought in the soil, which might be associated with a high vulnerability to cavitation in these species. From a methodological point of view, the results show the relevance of for distinguishing ecophysiological functional types among rainforest trees. 相似文献
17.
The production of erythritol and the erythritol yield from glucose by Torula sp. were improved, in increasing order, by supplementing with 10 mg MnSO44H2O l–1, 2 mg CuSO45H2O l–1, and both 10 mg MnSO44H2O l–1 and 2 mg CuSO45H2O l–1. Mn2+ decreased the intracellular concentration of erythritol, whereas Cu2+ increased the activity of erythrose reductase in cells. These results suggest that Mn2+ altered the permeability of cells, whereas Cu2+ increased the activity of erythrose reductase in cells. 相似文献
18.
The eddy correlation technique was employed to measure net ecosystem carbon dioxide (CO2) (NEE) and water vapor exchange (LE) over a C3/C4 co-occurring wet temperate Miscanthus-type grassland in the Kanto plain of Japan in the 1999 growing season. The maximal mean canopy height and maximal leaf area index were 1.0m and 5.5, respectively. The daily maximal LE was approximately 540Wm–2. The maximum value of daily accumulative LE was 16.3MJday–1. Daily variation of the decoupling factor () suggests that in the morning LE decoupled with the atmosphere, and the available energy was the major driving force for LE, whereas in the afternoon LE coupled strongly with the atmosphere, and the atmospheric evaporative demand played a critical role in LE. The decline in (from 0.8 to 0.5) with the growing season demonstrates that LE decoupled from the atmosphere in the later growth season. The peak NEE value was 57.4µmolCO2m–2s–1 (the positive value signifies the canopy carbon gain was from the air). The maximal daily integrated NEE was 1.06molCO2m–2day–1 observed during the peak growth stage. A rectangular hyperbolic model was used to describe the relation between daytime NEE and incident photosynthetic photon flux density (PPFD). The net ecosystem CO2 was not light-saturated up to a PPFD level of 2000µmol m–2s–1. The initial slope estimated with the NEE–PPFD response model was approximately 0.042molCO2mol–1photon on average. The canopy light compensation point ranged from 210 to 430µmolm–2s–1 with an average of approximately 310µmolm–2s–1. Both the initial slope and the canopy light compensation point decreased as the canopy senesced. The switch in dominance from C3 to C4 plants played an important role in the canopy fluxes. 相似文献
19.
Zhang W Liu CP Inan M Meagher MM 《Journal of industrial microbiology & biotechnology》2004,31(7):330-334
This paper provides an approach for optimizing the cell density (Xc) and dilution rate (D) in a chemostat for a Pichia pastoris continuous fermentation for the extracellular production of a recombinant protein, interferon (INF-). The objective was to maximize the volumetric productivity (Q, mg INF- l–1 h–1), which was accomplished using response surface methodology (RSM) to model the response of Q as a function of Xc and D within the ranges 150 Xc 450 g cells (wet weight) l–1 and 0.1 mD0.9 m (m=0.0678 h–1, the maximum specific growth rate obtained from a fed-batch phase controlled with a methanol sensor). The methanol and medium feed rates that resulted in the desired Xc and D were determined based on the mass balance. From the RSM model, the optimal Xc and D were 328.9 g l–1 and 0.0333 h–1 for a maximum Q of 2.73 mg l–1 h–1. The model of specific production rate (, mg INF- g–1 cells h–1) was also established and showed the optimal Xc=287.7 g l–1 and D=0.0361 h–1 for the maximum (predicted to be 8.92×10–3 mg–1 g–1 h–1). The methanol specific consumption rate (, g methanol g–1 cells h–1) was calculated and shown to be independent of the cell density. The relationship between and (specific growth rate) was the same as that discovered from fed-batch fermentations of the same strain. The approach developed in this study is expected to be applicable to the optimization of continuous fermentations by other microorganisms. 相似文献
20.
Dual Role of Superoxide Radicals in the Chilling-Induced photoinhibition in Maize Seedlings 总被引:1,自引:0,他引:1
Maize (Zea mays) seedlings were exposed for 6 h to strong irradiance (1 000 mol m–1 s–1 of PPFD) at 5, 12, 17, or 25 °C, followed by an exposure to the darkness for 6 h at 22 °C. Leaf chlorophyll fluorescence, net photosynthetic rate (P
N), and the amount of superoxide radicals (O2
–) in relation to chilling-induced photoinhibition were investigated. During the photophase, a good correlation (r=–0.879) was observed between PS2 (relative quantum efficiency of PS2 electron transport) and the amount of O2
–. Treatment with exogenous O2
– reduced the P
N and PS2 as the chilling stress did, that was inhibited by specific scavenger of O2
–. Hence chilling-induced photoinhibition might be due to the production of O2
–. In contrast, in the dark period, P
N and PS2 of the seedlings treated with the exogenous O2
– were enhanced, but they were inhibited by the specific scavenger of O2
–, showing the photoprotective role of O2
– in the recovery phase. Furthermore, in terms of the effect of exogenous O2
– on the xanthophyll cycle, the O2
– production suggested a promotion effect for the de-epoxidation of violaxanthin during the photophase, the epoxidation of zeaxanthin at the dark stage, and the increase of the xanthophyll pool both in the photophase and dark phase, resulting in an enhancement of the ability of non-photochemical quenching to avoid or alleviate the damage to photosynthetic apparatus. 相似文献