Low O2 Partial Pressure Research Articles

Chronic intermittent hypoxia induces hypoxia‐evoked catecholamine efflux in adult rat adrenal medulla via oxidative stress

Chronic intermittent hypoxia (CIH) augments physiological responses to low partial pressures of O2 in the arterial blood. Adrenal medullae from adult rats, however, are insensitive to direct effects of acute hypoxia. In the present study, we examined whether CIH induces hypoxic sensitivity in the adult rat adrenal medulla and, if so, by what mechanism(s). Experiments were performed on adult male rats exposed to CIH (15 s of 5% O2 followed by 5 min of 21% O2; 9 episodes h(-1); 8 h d(-1); for 3 or 10 days) or to comparable, cumulative durations of continuous hypoxia (CH; 4 h of 7% O2 followed by 20 h of 21% O2 for 1 or 10 days). Noradrenaline (NA) and adrenaline (ADR) effluxes were monitored from ex vivo adrenal medullae. In adrenal medullae of rats exposed to CIH, acute hypoxia evoked robust NA and ADR effluxes, whereas these responses were absent in control rats or in those exposed to CH for 1 or 10 days. Hypercapnia (10% CO2; either acidic, pH 6.8, or isohydric, pH 7.4) was ineffective in eliciting catecholamine (CA) efflux from control, CIH or CH rats. Nicotine (100 microM) evoked NA and ADR effluxes in control rats, and this response was abolished in CIH but not in CH rats. Systemic administration of 2-deoxyglucose depleted ADR content in control rats, and CIH attenuated this response, indicating downregulation of neurally regulated CA secretion. Cytosolic and mitochondrial aconitase enzyme activities decreased in CIH adrenal medullae, suggesting increased generation of superoxide anions. Systemic administration of antioxidants reversed the effect of CIH on the adrenal medulla. Rats exposed to CIH exhibited increased blood pressures and elevated plasma CA, and antioxidants abolished these responses. These observations demonstrate that CIH induces hypoxic sensing in the adult rat adrenal medulla via mechanisms involving increased generation of superoxide anions and suggest that hypoxia-evoked CA efflux from the adrenal medulla contributes, in part, to elevated blood pressure and plasma CA.

Au-catalyzed growth processes and luminescence properties of ZnO nanopillars on Si

ZnO nanopillars are often grown on various substrates by catalytic growth processes through a vapor-liquid-solid (VLS) mechanism. However, on silicon substrates, even with the catalyzed growth processes, it is still very difficult to obtain highly oriented ZnO nanopillar arrays. In this work, it was found that in most cases the actual growth process of ZnO on Si catalyzed by Au was not of real VLS character. In the initial growth stage, the substrate surface is partially melted and then oxidized into a very thin layer of SiO2. Zn-rich alloys instead of ZnO are first deposited on the SiO2∕Si substrates and form polycrystalline hillocks in an atmosphere with low O2 partial pressure. The difficulty for ZnO to nucleate on SiO2∕Si is another reason preventing ZnO nanopillars from growing epitaxially on the substrates. Defects, steps, and∕or stress on the substrate surfaces may support the nucleation process and thus may influence the initial growth stage and the control of the growth orientation of the pillars. With the help of scratches on Si substrates and by avoiding the formation of hillocks, well-aligned ZnO nanopillars were obtained both on Si (111) and (100) surfaces. Sharp photoluminescence (PL) peaks of bound exciton emissions and a free exciton emission were detected at low temperature. An unreported PL peak at about 3.367eV and in some cases a donor-acceptor-pair transition at about 3.308eV were also found. At higher temperature, a band-acceptor recombination process together with strong LO-phonon replicas occurred. A donor dopant concentration ND of about 5.7×1018cm−3 and an acceptor ionization energy of 126±2meV were evaluated from the spectra.

Fermentative metabolism in ‘Conference’ pears under various storage conditions

SummaryThe aim of this work was to investigate the fermentative metabolism of ‘Conference’ pears during different storage regimes. Fruits were stored at 0°C in the following controlled atmosphere (CA) conditions: 6 kPa CO2 + 0.5 kPa O2;3 kPa CO2 + 1 kPa O2; or 1 kPa CO2 + 2 kPa O2; and also in regular air (RA) as a control. Pears kept in RA showed low pyruvate decarboxylase (PDC) and alcohol dehydrogensase (ADH) activities, and correspondingly low levels of ethanol and acetaldehyde production as long as the fruits were maintained at low temperatures. During shelf-life at 20°C, RA-fruits released higher amounts of acetaldehyde, while ethanol production remained low. Lactate concentrations in RA-stored pears increased continuously in the second part of the storage period and during shelf-life, while lactate dehydrogenase (LDH) activity remained low. During CA-storage, ‘Conference’ pears showed continuous increases in the activities of PDC and ADH, mainly in fruits stored under high CO2 and/or low O2 partial pressures. The production of ethanol and acetaldehyde was not influenced in fruits stored in 6 kPa CO2 + 0.5 kPa O2. LDH activity in CA-stored pears increased during storage, while lactate concentrations diminished. During shelf-life at 20°C, the concentrations of all measured fermentation products increased, particularly acetaldehyde and lactate. We conclude that PDC, ADH, and LDH activities are not rate-limiting factors in the accumulation of fermentation products in ‘Conference’ pears during storage and shelf-life at 20°C.

A nitric oxide processing defect of red blood cells created by hypoxia: Deficiency of S-nitrosohemoglobin in pulmonary hypertension

The mechanism by which hypoxia [low partial pressure of O(2) (pO(2))] elicits signaling to regulate pulmonary arterial pressure is incompletely understood. We considered the possibility that, in addition to its effects on smooth muscle, hypoxia may influence pulmonary vascular tone through an effect on RBCs. We report that exposure of native RBCs to sustained hypoxia is accompanied by a buildup of heme iron-nitrosyl (FeNO) species that are deficient in pO(2-)governed intramolecular transfer of NO to cysteine thiol, yielding a deficiency in the vasodilator S-nitrosohemoglobin (SNO-Hb). S-nitrosothiol (SNO)-deficient RBCs produce impaired vasodilator responses in vitro and exaggerated pulmonary vasoconstrictor responses in vivo and are defective in oxygenating the blood. RBCs from hypoxemic patients with elevated pulmonary arterial pressure (PAP) exhibit a similar FeNO/SNO imbalance and are thus deficient in pO(2)-coupled vasoregulation. Chemical restoration of SNO-Hb levels in both animals and patients restores the vasodilator activity of RBCs, and this activity is associated with improved oxygenation and lower PAPs.

Heterogeneous Oxidation of Fe(II) on Ferric Oxide at Neutral pH and a Low Partial Pressure of O2

The objective of this study was to identify the rate and mechanism of abiotic oxidation of ferrous iron at the water-ferric oxide interface (heterogeneous oxidation) at neutral pH. Oxidation was conducted at a low partial pressure of O2 to slow the reactions and to represent very low dissolved oxygen (DO) conditions that can occur at oxic/anoxic fronts. Hydrous ferric oxide (HFO) was partially converted to goethite after 24 h of anoxic contact with Fe(II), consistent with previous results. This resulted in a significant decrease in sorption of Fe(II). No conversion to goethite was observed after 25 min of anoxic contact between HFO and Fe(II). O2 was then introduced into the chamber and sparged (transfer half-time of 1.6 min) into the previously anoxic suspension, and the rate of oxidation of Fe(II) and the distribution between sorbed and dissolved Fe(II) were measured with time. The concentration of sorbed Fe(II) remained steady during each experiment, despite removal of all measurable dissolved Fe(II) in some experiments. The rate of oxidation of Fe(II) was proportional to the concentration of DO and both sorbed and dissolved Fe(II) up to a surface density of 0.02 mol Fe(II) per mol Fe(III), i.e., approximately 0.2 Fe(II) per nm2 of ferric oxide surface area. This result differs from previous studies of heterogeneous oxidation, which found that the rate was proportional to sorbed Fe(II) and DO but did not find a dependence on dissolved Fe(II). Most previous experiments were autocatalytic; i.e., the initial concentration of ferric oxide was low or none, and sorbed Fe(II) was not measured. The results were consistentwith an anode/cathode mechanism, with O2 reduced at electron-deficient sites with strongly sorbed Fe(II) and Fe(II) oxidized at electron-rich sites without sorbed Fe(II). The pseudo-first-order rate constants for oxidation of dissolved Fe(II) were about 10 times faster than those previously predicted for heterogeneous oxidation of Fe(II).

Application of boron with calcium affects respiration and ATP/ADP ratio in ‘Conference’ pears during controlled atmosphere storage

SummaryInternal flesh browning and cavities frequently occur in ‘Conference’ pears during controlled atmosphere (CA)-storage, particularly under high CO2 or low O2 partial pressures, or both. Boron (B) appears to alleviate the occurrence of browning injuries. In three consecutive years, the effects of pre-harvest B application, alone or combined with calcium (Ca), were assessed on several physiological parameters of pear fruit stored under high CO2 conditions.‘Conference’ pear trees were sprayed with B up to six-times before harvest, with or without additional Ca and, after harvest, fruits were stored at –0.5°C, 5 kPa CO2 + 2 kPa O2. During the subsequent 5-month storage period, pears were removed from storage and monitored for fruit quality, physiological disorders, respiration, and the ATP/ADP status of fruit tissue. The results showed that, after CA-storage, untreated control fruits were more susceptible to internal browning than those treated with B. The lowest incidence of browning disorders was obtained in fruits sprayed with B and Ca. At harvest, fruits treated with B were also greener, firmer and less acidic than control fruits. B-treated fruits evolved less CO2 and had lower O2 uptake rates at harvest and during the 5-month storage period. The energy status, expressed as the ATP:ADP ratio, was also higher in fruits treated six-times with B. This higher ratio may have been caused by a lower demand for energy, thus allowing a greater net accumulation of ATP for maintenance of cell integrity and function.

Influence of low oxygen and high carbon dioxide on shredded Galega kale quality for development of modified atmosphere packages

Respiration rate, sensory attributes, colour alterations, and water, chlorophyll and ascorbic acid contents were monitored during storage of shredded Galega kale (Brassica oleracea var. acephala DC.) at 20 ◦ C to define an adequate range of O 2 and CO2 partial pressures for product preservation. Different low O 2 and high CO2 atmospheres were tested. First, tolerance to low O2 partial pressures (1, 2, 3 or 21 kPa O2 with balance N2) was tested. Quality retention was improved as O2 partial pressure was reduced and there was no induction of anaerobic respiration. Then, tolerance to high CO2 partial pressures (0, 10, 15 or 20 kPa CO2 plus 21 kPa O2 and balance N2) was tested. The high CO2 partial pressures extended the shelf life of the shredded kale and no symptoms of CO2 injury were detected. Finally, combinations of low O2 and high CO2 (1 or 2 kPa O2 plus 15 or 20 kPa CO2, with balance N2, and an air control) were analysed. No differences were observed among the different gas combinations. An atmosphere of 1–2 kPa O2 plus 15–20 kPa CO2 and balance N2 extends the shelf life of shredded Galega kale to 4–5 days at 20 ◦ C, compared with 2–3 days in air storage. Predictive models of chlorophyll a and b degradation as a function of time and gas composition were developed.

MECHANISMS OF HETEROGENEOUS FE(II) OXIDATION IN ACID MINE DRAINAGE1

Abstract. The objective of the study was to investigate the sorption and abiotic oxidation of ferrous iron at ferric oxide surfaces at pH 6.8 and 7.0, and to identify changes in ferric oxide phase during the sorption and oxidation processes. Our group previously reported on mechanisms for sorption and heterogeneous oxidation at pH less than 6.5 and on the characteristics of ferric oxide sludge. We have also reported on transformations from amorphous to crystalline ferric oxides as a function of pH and solution composition. Sorption experiments were conducted at room temperature in an anaerobic chamber with 97% N2 and 3% H2. An additional oxygen trap was used to ensure an anoxic environment. The Fe(II)/Fe(III) ratio and pH were varied. The rate and extent of sorption of Fe(II) were monitored. Changes in solid phases were monitored using 57Fe-Mössbauer Spectroscopy. Subsequent to sorption, oxidation rate constants and mechanisms were evaluated after exposure to very low partial pressures of O2. The results showed that oxidation processes that occurred with high Fe(III) to Fe(II) ratios were more complicated in the neutral pH range compared to pH < 6.5, due to phase transformations that resulted in short-term sorption anomalies, such as decreased sorption after conversion from amorphous ferric oxide to goethite or precipitation of mixed Fe(II)/Fe(III) phases that slowly became inert to oxidation. These results are important in the context of treatment processes for AMD that depend on the presence of a ferric oxide phase, that is for high-density sludge processes that result in heterogeneous oxidation of Fe(II) and that are conducted at slightly acid to alkaline pH values.

Kinetics Of Charge Generation During Formation Of Hf And Zr Silicate Dielectrics

AbstractUnderstanding charged defects in high dielectric constant insulators is a critical challenge for advanced devices. We have formed thin Zr and Hf silicates by oxidation of thin metal films sputtered on clean Si(100) and studied the effect of oxidation time (15 to 300s) and temperature (600 or 900°C) on the flatband voltage using capacitance vs. voltage measurements. We find that the thermal budget during oxidation and the type of oxidizing agent (slow vs. fast) affect the amount of fixed charge in the film significantly. Oxidation of 0.8nm of Zr metal on Si at 600°C in N2O for 15s results in EOT=1.2nm and a shift in the flatband voltage by ∼-0.2V indicating generation of positive fixed charge. Oxidation of similar films for 300s result in EOT=2.8nm and shift of the flatband voltage by ∼-0.95V. Hf films oxidized in N2O also show increased concentrations of fixed charge for longer oxidation times. By comparison, Si oxidized in the same environment does not show this extent of flatband voltage shift. A significantly reduced charge generation rate is observed for Hf oxidation under low O2 partial pressure. Extended oxidations (up to 1h) result in increased EOT and a slight decrease in the charged defect state density. Forming Gas Anneal (FGA) results in partial neutralization of the charge. FGA after the Al gate deposition also leads to significant decrease of the EOT (from 2.7 to 2.1nm) indicating significant reaction of the film with the gate metal. X-ray photoelectron spectroscopy for thin films indicates formation of Zr and Hf-silicates. However, for thick Hf films the low O2 oxidation process results in less silicon incorporation in the film as compared to films oxidized in N2O. Results suggest that understanding oxidation mechanisms will be important in isolating andcontrollingfixedchargeinhigh-kdielectrics.

Effect of Al-content and Post Deposition Annealing on the Electrical Properties of Ultra-thin HfAlxOy Layers

ABSTRACTScaled HfAlxOy/SiO2 stacks down to 1.5 nm EOT have been achieved. Although the addition of Al to the HfO2 matrix can be beneficial, it is observed that the benefit of using a Hf-aluminate is compromised if the film has a high Al-content. This is observed in terms of a dielectric constant close to that of pure Al2O3 (∼ 9) and a large amount of negative fixed charge in the film (∼ 1012 cm-2). Using oxygen post deposition anneals we have been able to reduce flatband voltage shifts associated with fixed charge as well as CV hysteresis. In terms of scaling, the benefit of using a high-k material is compromised if a SiO2 layer is also present in the gate stack. Therefore, it is necessary to perform an O2 PDA at moderate temperatures or in low O2 partial pressures in order to control the thickness of the interfacial oxide layer.

Direct heteroepitaxy of crystalline Y2O3 on Si (001) for high-k gate dielectric applications

This work focuses on the microstructural characteristics of Y2O3 thin films and interfaces, which is related to their suitability as high-k replacement for SiO2 gate dielectrics in future transistor devices. The films were grown directly on silicon (001) substrates by electron-beam evaporation in a molecular beam epitaxy chamber under ultrahigh vacuum conditions. At an optimum growth temperature, ∼450 °C, high crystalline quality films were obtained, albeit with a heteroepitaxial relationship Y2O3 (110)//Si (001) and Y2O3 [001]//Si 〈110〉, which favors the formation of a potentially harmful complex microstructure. The latter consists of large (submicron-sized) domains containing smaller (10–30 nm) inclusions with perpendicular crystal orientations. Despite predictions for thermodynamic stability and low O2 partial pressure in the chamber, the chemical reaction of Y2O3 with Si could not be avoided. Indeed, a nonuniform interfacial amorphous layer with thickness 5–15 Å was observed, while YSi2 was formed at a moderate growth temperature (610 °C).

How water oxygenation level influences cadmium accumulation pattern in the Asiatic clam Corbicula fluminea: A laboratory and field study

The level of O2 in water is highly variable in the aquatic environment and is a major ventilatory drive in all animals breathing water. Low O2 partial pressure (PO2) strongly stimulates ventilatory activity compared to air-equilibrated or O2-enriched water. We studied the influence of ventilatory activity on the bioaccumulation rate of Cd in the freshwater Asiatic clam Corbicula fluminea for PO2 ranging from 4 to 40 kPa (2-20 mg/L at 15 degrees C) during steady-state exposure to controlled concentrations of Cd of approximately 2 or 0.5 microg/L under both laboratory and field conditions. The concentration of Cd in the expired water and its apparent extraction coefficient (EwCd) from the ventilated water were calculated. Results show that a low PO2 strongly enhanced Cd bioaccumulation rate in the whole soft body and modified the distribution pattern and the relative burden in the organs. Whatever the water PO2, values for the concentration of Cd in the expired water remained close to the Cd concentration in the inspired water and EwCd varied from 2 to 12%. Because the field results conformed to the laboratory analysis, the suggestion is made that the influence of O2 on bioaccumulation patterns of metals in water-breathers should be classified as of primary importance.

Physiological responses of fresh-cut apple slices under high CO2 and low O2 partial pressures

Abstract The physiological responses of ‘Delicious’ apple slices to 0–30 kPa CO2 at 0–10 kPa O2 partial pressures at 5°C have been studied. Increasing CO2 partial pressures from 0 to 30 kPa at 0.5, 1 and 10 kPa O2 reduced respiration rates and ethylene production of the slices. The inhibitory effect of CO2 on respiration rate of slices was best explained by an enzyme kinetics model that combined competitive and uncompetitive types of inhibition. Browning increased during storage and was reduced by CO2 to only a limited extent. CO2 levels of 15–30 kPa resulted in about a 50% reduction in acetaldehyde, ethanol and ethyl acetate concentrations in tissues under both anaerobic and low-O2 atmospheres compared with slices kept in CO2-free atmospheres. Elevated CO2 might provide a mechanism to reduce accumulation of fermentation products but sensory quality of slices needs be studied before recommending its use.

Crystallization of SrBi2Ta2O9 Thin Films in N2 Ambient by Chemical Solution Deposition Method

Structural and electrical properties of SrBi2Ta2O9 (SBT) thin films crystallized upon annealing in an N2 ambient were investigated. These thin films were prepared on Pt/TiO2/SiO2/Si substrates by the chemical solution deposition (CSD) method. The films crystallized in N2 after calcination at a high O2 partial pressure in an N2/O2 mixed ambient showed good ferroelectric properties with remanent polarization 2Pr=13–14 µC/cm2, coercive field 2Ec=70–80 kV/cm, and leakage current density less than 1×10-7 A/cm2 at an applied voltage of 3 V. These ferroelectric properties are the same as those of the SBT crystallized in O2. However, the films crystallized in N2 after calcination at a low O2 partial pressure in an N2/O2 mixed ambient did not form SBT. TDS data showed that the carbon content of the film calcined in poor O2 was higher than that of the film calcined in rich O2. These results showed that the carbon residue within the film might disturb the formation of SBT.

Deep-ultraviolet transparent conductive β-Ga2O3 thin films

Thin films of β-Ga2O3 with an energy band gap of 4.9 eV were prepared on silica glass substrates by a pulsed-laser deposition method. N-type conductivity up to ∼1 S cm−1 was obtained by Sn-ion doping and deposition under low O2 partial pressure (∼10−5 Pa) at substrate temperatures above 800 °C. The resulting internal transmittance at the wavelength (248 nm) of the KrF excimer laser exceeded 50% for the 100-nm-thick film, making this the most ultraviolet-transparent conductive oxide thin film to date and opening up prospects for applications such as ultraviolet transparent antistatic electric films in ultraviolet lithography.

Preparation and Ferroelectric Properties of Ti-Site Substituted BaTiO3 Thin Films

Thin films of BaTi0.91(Hf0.5, Zr0.5)0.09O3 on Pt/SiO2/Si(100), Nb-doped SrTiO3 (100) and (111) substrates were synthesized by a pulsed laser deposition method using fourth harmonic generated light of Nd3+:YAG laser beam under low O2 partial pressure. The in-situ observation of BaTi0.91(Hf0.5, Zr0.5)0.09O3 film deposition on a Nb-doped SrTiO3 (100) substrate was performed using reflection high energy electron beam diffraction. The BaTi0.91(Hf0.5, Zr0.5)0.09O3 films deposited on Nb-doped SrTiO3 (100) and (111) substrates showed preferential [100] and [111] orientations, respectively. The ferroelectric properties of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin films were investigated by electrical measurements. The frequency dependence of the dielectric constant of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film was influenced by low dielectric phase, and it was analyzed by the Debye model. The remanent polarization and coercive field of BaTi0.91(Hf0.5, Zr0.5)0.09O3 thin film were measured at room temperature, and those values were 7.4 µC/cm2 and 123 kV/cm, respectively.

Observation of the vortex-glass and the melting transitions in NdBa2Cu3O7-y single crystals grown by different methods

We present the transport and magnetization properties of NBCO single crystals grown by the travelling solvent floating zone (TSFZ) and the self-flux (SF) methods under low O2 partial pressure. The TSFZ-grown crystal shows a continuous transition exhibiting a vortex-glass behaviour in V-I characteristics for H = 1 T. In contrast, a first-order melting transition was observed in the crystal grown by the SF method under 0.03% O2 partial pressure displaying a kink and hysteresis in resistance. The temperature dependent magnetization curves show a change in slope at the melting transition. The V-I characteristics in field for the SF-grown crystal exhibited a characteristic S-shape behaviour at the melting transition. The different behaviour in transport properties between two set of crystals suggests that the presence of twin planes and the substitutional defects play a major role in the observed vortex dynamics.

Purification of Mullite by Reduction and Volatilization of Impurities

Mullite materials usually contain a residual glassy phase rich in SiO2, which concentrates impurities as Na2O, K2O, Fe2O3, and other minority compounds. A suitable way to minimize this glassy phase is the reduction and volatilization of its components by calcination at high temperatures (1300–1450°C) in atmospheres with a very low partial pressure of O2. Over 95% of the Na2O, K2O, and Fe2O3 in mullite can be removed in this way, leaving concentrations lower than 0.02% by weight. To avoid the degradation of mullite that occurs when the partial pressure of O2 is too low, the material to be purified is covered with TiO2 plates.

Electrical conductivity of copper oxide based cermets: V.V.Ivanov et al. (Krasnoyarsk State University, Krasnoyarsk, Russia.)

Thin films of CuO and Cu2O were deposited from CuI as the copper source and O2 or N2O as the oxygen source. If O2 was used, both CuO and Cu2O were obtained. Cu2O was deposited at low O2 partial pressures (Po2 < 0.2 Torr) in a long isothermal hot wall chemical vapour deposition (CVD) reactor (T=500 °C). The CuO phase was obtained at a certain position in the CVD reactor and a sudden maximum in the deposition rate was then reached. The maximum was attributed to a change in the deposition mechanism upon the formation of CuO. When I2 was added to the reaction gas mixture, the maximum disappeared and the deposition rate increased. The formation of CuO was also investigated thermodynamically. For higher [I2]/[CuI] ratios, the CuO phase was stable, even at a low O2 pressure. Cu2O films were also deposited with N2O as the oxygen source. At 650 °C and with an excess of CuI, the deposition rate was found to be controlled by the decomposition of N2O. Above a linear gas flow velocity of 70 cm s−1, the deposition rate was constant, which indicated a surface-controlled process.

Differential control of xanthophylls and light-induced stress proteins, as opposed to light-harvesting chlorophyll a/b proteins, during photosynthetic acclimation of barley leaves to light irradiance

Barley (Hordeum vulgare L.) plants were grown at different photon flux densities ranging from 100 to 1800 &mgr;mol m-2 s-1 in air and/or in atmospheres with reduced levels of O2 and CO2. Low O2 and CO2 partial pressures allowed plants to grow under high photosystem II (PSII) excitation pressure, estimated in vivo by chlorophyll fluorescence measurements, at moderate photon flux densities. The xanthophyll-cycle pigments, the early light-inducible proteins, and their mRNA accumulated with increasing PSII excitation pressure irrespective of the way high excitation pressure was obtained (high-light irradiance or decreased CO2 and O2 availability). These findings indicate that the reduction state of electron transport chain components could be involved in light sensing for the regulation of nuclear-encoded chloroplast gene expression. In contrast, no correlation was found between the reduction state of PSII and various indicators of the PSII light-harvesting system, such as the chlorophyll a-to-b ratio, the abundance of the major pigment-protein complex of PSII (LHCII), the mRNA level of LHCII, the light-saturation curve of O2 evolution, and the induced chlorophyll-fluorescence rise. We conclude that the chlorophyll antenna size of PSII is not governed by the redox state of PSII in higher plants and, consequently, regulation of early light-inducible protein synthesis is different from that of LHCII.