Effect of the insecticide clothianidin on the photosynthetic electron transport chain in pea.

Clothianidin (CL) is a neonicotinoid insecticide widely used in crop protection against insect pests. However, its effects on photosynthesis remain largely unknown. Here, by investigating the influence of CL at the concentrations of 22 and 110 μg/L on the primary processes of photosynthesis, membrane fluidity and structural changes of pea chloroplasts, we located several primary binding sites of this pesticide.

Nanodiamond Particles Reduce Oxidative Stress Induced by Methyl Viologen and High Light in the Green Alga .

Widely used in biomedical and bioanalytical applications, the detonation nanodiamonds (NDs) are generally considered to be biocompatible and non-toxic to a wide range of eukaryotic cells. Due to their high susceptibility to chemical modifications, surface functionalisation is often used to tune the biocompatibility and antioxidant activity of the NDs. The response of photosynthetic microorganisms to redox-active NDs is still poorly understood and is the focus of the present study.

Acclimation Response of Green Microalgae Chlorella Sorokiniana to 2,3',4,4',6-Pentachlorobiphenyl.

The effect of the toxicant 2,3',4,4',6-pentachlorobiphenyl (PCB-119) on the growth, chlorophyll content, and PSII activity of C. sorokiniana cells was investigated. A strong negative effect of the toxicant was observed at PCB concentration of 0.

Single-walled carbon nanotubes protect photosynthetic reactions in Chlamydomonas reinhardtii against photoinhibition.

Single-walled carbon nanotubes (SWCNTs) are among the most exploited carbon allotropes in nanosensing, bioengineering, and photobiological applications, however, the interactions of nanotubes with the photosynthetic process and structures are still poorly understood. We found that SWCNTs are not toxic to the photosynthetic apparatus of the model unicellular alga Chlamydomonas reinhardtii and demonstrate that this carbon nanomaterial can protect algal photosynthesis against photoinhibition. The results show that the inherent phytotoxicity of the nanotubes may be overcome by an intentional selection of nanomaterial characteristics.

Multiple in vivo Effects of Cadmium on Photosynthetic Electron Transport in Pea Plants.

The inhibitory effects of cadmium (CdSO ) on the primary photosynthetic processes were studied in vivo in Pisum sativum by using Multi-function Plant Efficiency Analyser (M-PEA-2). Photosynthetic parameters related to photosystem (PS) II, PS I and intersystem electron carriers were calculated from the light-induced kinetics of prompt chlorophyll a fluorescence (OJIP transient), delayed chlorophyll a fluorescence (DF), and 820 nm modulated reflection (MR). Low-dose exposure to cadmium (20 μm CdSO for 48 h) reduced probability of electron transfer from plastoquinones to the terminal electron acceptors of PSI (δ ) accompanied by a decrease in the rate of P and PC reduction (V ) and the magnitude of the I step on the DF kinetics.

Immobilized heterocysts as microbial factories for sustainable nitrogen fixation.

A novel thin-layer biocatalyst for photosynthetic N fixation and H photoproduction was assembled using a Ca-alginate matrix and heterocysts isolated from wild-type Anabaena sp. PCC 7120 filaments. Compared to suspension heterocysts, heterocysts entrapped in Ca-alginate films showed improved stability of the nitrogenase system.

Chlorophyll fluorescence induction and relaxation system for the continuous monitoring of photosynthetic capacity in photobioreactors.

The development of high-performance photobioreactors equipped with automatic systems for non-invasive real-time monitoring of cultivation conditions and photosynthetic parameters is a challenge in algae biotechnology. Therefore, we developed a chlorophyll (Chl) fluorescence measuring system for the online recording of the light-induced fluorescence rise and the dark relaxation of the flash-induced fluorescence yield (Qa - re-oxidation kinetics) in photobioreactors. This system provides automatic measurements in a broad range of Chl concentrations at high frequency of gas-tight sampling, and advanced data analysis.

Comparative analyses of H photoproduction in magnesium- and sulfur-starved Chlamydomonas reinhardtii cultures.

Magnesium (Mg)-deprived Chlamydomonas reinhardtii cells are capable to sustain hydrogen (H ) photoproduction at relatively high photosystem II (PSII) activity levels for an extended time period as compared with sulfur (S)-deprived cells. Herein, we present a comparative study of H photoproduction induced by Mg and S shortage to unravel the specific rearrangements of the photosynthetic machinery and cell metabolism occurring under the two deprivation protocols. The exhaustive analysis of photosynthetic activity and regulatory pathways, respiration and starch metabolism revealed the specific rearrangements of the photosynthetic machinery and cellular metabolism, which occur under the two deprivation conditions.

Increased photosystem II stability promotes H2 production in sulfur-deprived Chlamydomonas reinhardtii.

Photobiological H2 production is an attractive option for renewable solar fuels. Sulfur-deprived cells of Chlamydomonas reinhardtii have been shown to produce hydrogen with the highest efficiency among photobiological systems. We have investigated the photosynthetic reactions during sulfur deprivation and H2 production in the wild-type and state transition mutant 6 (Stm6) mutant of Chlamydomonas reinhardtii.

[Performance index as an indicator of the physiological state of trees in urban forest ecosystems].

Based on the measurements of fluorescence of bark chloroplasts by means of PAM and PEA fluorometers, the information capacity of the methods for assessing the physiological state of Tilia cordata L. from the maximum quantum efficiency of PS II photochemistry (Fv/Fm) and the performance index (PI) has been compared. The measurements were performed on annual shoots of linden trees growing in different environment.

[Study of the effect of methylmercury and copper ions on primary photosynthesis processes in the green algae Chlamydomonas moevusii using the parameters of kinetic curves of the variable of chlorophyll fluorescence].

The effect of methylmercury and copper ions on the kinetics of light induction and dark relaxation of the variable of chlorophyll a fluorescence has been studied on cultures of the microalgae Chlamydomonas moevusii. It was shown that the toxicants added at concentrations that induce no decrease in photochemical activity of PS II (F(v)/F(M)) affect the electron transport on the acceptor side of PS II, the nonphotochemical quenching of excitation in the antenna, and the reoxidation of the quinone pool. At low concentrations, methylmercury produced a more toxic effect.

Probing of photosynthetic reactions in four phytoplanktonic algae with a PEA fluorometer.

High-resolution light-induced kinetics of chlorophyll fluorescence (OJIP transients) were recorded and analyzed in cultures of diatoms (Thalassiosira weissflogii, Chaetoceros mulleri) and dinoflagellates (Amphidinium carterae, Prorocentrum minimum). Fluorescence transients showed the rapid exponential initial rise from the point O indicating low connectivity between PS II units and high absorption cross-section of PS II antenna. Dark-adapted dinoflagellates revealed capability to maintain the PS I-mediated re-oxidation of the PQ pool at the exposure to strong actinic light that may lead to the underestimation of F(M) value.

[Effect of dibromothymoquinone on chlorophyll a fluorescence in Chlamydomonas reinhardtii cells incubated in complete or sulfur-depleted medium].

The influence of dibromothymoquinone on chlorophyll fluorescence was studied in Chlamydomonas reinhardtii cells using PAM and PEA fluorometers. The reagent affected differently control cells incubated in complete medium and S-starved cells. Thus, the fluorescence yield in the control essentially increased in the presence of dibromothymoquinone, which can be due to the inactivation of light-harvesting complex II protein kinase, followed by the suppression of membrane transition from high-fluorescence state 1 to low-fluorescence state 2.

Examination of chlorophyll fluorescence decay kinetics in sulfur deprived algae Chlamydomonas reinhardtii.

Chlorophyll fluorescence decay kinetics was measured in sulfur deprived cells of green alga Chlamydomonas reinhardtii with a home made picosecond fluorescence laser spectrometer. The measurements were carried out on samples either shortly adapted to the dark ('Fo conditions') or treated to reduce Qa ('Fm conditions'). Bi-exponential fitting of decay kinetics was applied to distinguish two components one of them related to energy trapping (fast component) and the other to charge stabilization and recombination in PS 2 reaction centers (slow component).

[Examination of chlorophyll fluorescence in sulfur-deprived cells of Chlamydomonas reinhardtii].

Modulated fluorometry (PAM) was applied for probing the photosynthesis in cells of C. reinhardtii during sulfur deprivation. A significant (up to a fourfold) increase in chlorophyll fluorescence yield (parameters F(o) and F(m)) normalized to chlorophyll concentration was shown for deprived cells.