pheophytin-a and anthracene

A decrease in photosynthetic efficiency may indicate the toxic effects of environmental pollutants on higher plants. Measurement of chlorophyll (Chl) a fluorescence to assess the performance of photosystem II (PSII) was used as an bioindicator of toxicity of the polycyclic aromatic hydrocarbon (PAH) anthracene (ANT) in soybean plants. The results revealed that ANT treatment caused a reduction in quantum yield of PSII, damage to the oxygen evolving complex, as well as a significant reduction in performance index of PSII. However, change in performance index was more prominent, and it seems that the performance index is a more sensitive parameter to environmental contaminants. Moreover, a change in heterogeneity of PSII was also observed. The number of active reaction centres decreased with increasing concentration of ANT, as secondary plastoquinone reducing centres were converted into non-reducing centres, and PSIIα centres were converted into PSIIβ and PSIIγ centres. The influence of ANT on PSII heterogeneity could be an important reason for reductions in the PSII performance.

Topics: Anthracenes; Chlorophyll; Chlorophyll A; Fluorescence; Glycine max; Photosynthesis; Photosystem II Protein Complex; Plant Leaves

Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) are present in the freshwater environment at concentrations that can be hazardous to the biota. Among HMs and PAHs, cadmium (Cd) and anthracene (ANT) are the most prevalent and toxic ones. The response of Chlamydomonas cells to Cd and ANT at concentrations that markedly reduced the growth of algal population was investigated in this study. At such concentrations, both cadmium and anthracene were recognized as oxidative stress inducers, since high concentration of H2O2 in treated cultures was observed. Therefore, as a part of the "molecular phase" of the cell response to this stress, we examined the time-dependent expression of genes encoding the main antioxidative enzymes: superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), as well as the activity of these enzymes in cells, with special attention paid to chloroplastic and mitochondrial isoforms of SOD. To characterize the cell response at the "physiological level", we examined the photosynthetic activity of stressed cells via analysis of chlorophyll a fluorescence in vivo. In contrast to standard ecotoxicity studies in which the growth end-points are usually determined, herein we present time-dependent changes in algal cell response to Cd- and ANT-induced stress. The most significant effect(s) of the toxicants on photosynthetic activity was observed in the 6th hour, when strong depression of PI parameter value, an over 50 percent reduction of the active reaction center fraction (RC0) and a 3-fold increase in non-photochemical energy dissipation (DI0/RC) were noted. At the same time, the increase (up to 2.5-fold) in mRNA transcript of SOD and CAT genes, followed by the enhancement in the enzyme activity was observed. The high expression of the Msd 3 gene in treated Chlamydomonas cells probably complements the partial loss of chloroplast Fe-SOD and APX activity, while catalase and Mn-SOD 5 seem to be the major enzymes responsible for mitochondrion protection. The progressive increase in SOD and CAT activities seems to be involved in the recovery of photosynthesis within 12-24h after the application of the toxicants.

Topics: Anthracenes; Antioxidants; Ascorbate Peroxidases; Cadmium; Catalase; Chlamydomonas reinhardtii; Chlorophyll; Chlorophyll A; Environmental Pollutants; Gene Expression; Hydrogen Peroxide; Photosynthesis; Superoxide Dismutase; Time Factors

Cells of Desmodesmus subspicatus 86.81 were used to examine the toxicity of cadmium chloride (CdCl(2)) and anthracene (ANT) applied individually and in combination. The experiments were performed according to standardized ISO (International Organization for Standardization) 8692 protocol (2004). Parameters measured were the number of cells and chlorophyll a fluorescence parameters. E(r)C(10) and E(r)C(50) values (growth rate [r] inhibition by 10% and 50%, respectively) for single toxicants were determined separately. The effect of mixtures of the substances (Cd + ANT) at concentrations corresponding to E(r)C(10) (E(r)C(10) + E(r)C(10)) and E(r)C(50) (E(r)C(50) + E(r)C(50)) values was characterized. The toxicity of individual chemicals after a 72-h exposure was as follows: ANT (E(r)C(10) = 0.06; E(r)C(50) = 0.26 mg l(-1)) and CdCl(2) (E(r)C(10) = 0.12; E(r)C(50) = 0.30 mg l(-1)). The combination Cd + ANT decreased the population growth rate more strongly than the substances applied individually. Cadmium at a concentration corresponding to E(r)C(10) slightly influenced the parameters of chlorophyll a fluorescence as measured by the OJIP test (O, J, I, and P are the different steps of fluorescence induction curve), whereas the influence of ANT was not statistically significant. In Cd + ANT-treated samples, the photosynthetic "vitality" (PI), the maximum quantum yield of primary photochemistry (φ(Po)), and the fraction of active PS II reaction centre (RC) decreased, but the values of ABS/RC, TR(0)/RC, and DI(0)/RC increased. The type of interaction between Cd and ANT depended on the concentration of chemicals used. When the substances were applied at concentrations of E(r)C(10), synergistic effects were observed, whereas the mixture of chemicals used at an E(r)C(50) concentration showed an antagonistic interaction.

Topics: Anthracenes; Cadmium; Chlorophyll; Chlorophyll A; Chlorophyta; Dose-Response Relationship, Drug; Environmental Monitoring; Fluorescence; Toxicity Tests; Water Pollutants, Chemical

Individual toxicity of heavy metals (HM) and polycyclic aromatic hydrocarbons (PAH) to plants living in water bodies is well-documented. In view of frequent joint occurrence of these compounds in the environment, plants are subjected to damage from their combined action. Cadmium and anthracene can generate production of reactive oxygen species (ROS). We have recently detected elevated activity of Fe- and Mn-SOD isoforms, indicating chloroplast and mitochondrion as the main sites of combined toxicity of HM and PAH. In the present paper, short-term (1-24 h) experiments on the mechanism of combined toxicity of anthracene and cadmium to the photosynthesis of three Desmodesmus species are reported. Inhibition, stimulation or no effect on the oxygen evolution was observed following the treatment with the contaminants when applied either separately or jointly. The response pattern was both strongly species- and time-dependent. In contrast, the photosynthetic activity of cells, expressed by chlorophyll fluorescence parameters, was substantially unaffected, since no effect or, in several cases, a slight stimulation of PS II quantum efficiency (Phi PS II) were noted. A characteristic relationship between the SOD activity and the qN values was observed. The treatment of Desmodesmus cells with anthracene or cadmium had either no effect or slightly enhanced either the SOD activity or the qN value, whereas the mixture of the contaminants resulted in a multifold increase in both the SOD activity and the qN values. The results suggest that chloroplasts of algae are well protected against the combined action of the two contaminants the toxicity of which should be attributed to nucleocytoplasmic compartments and reproductive processes of the cell cycle.

Topics: Anthracenes; Cadmium; Chlorophyll; Chlorophyll A; Chlorophyta; Chloroplasts; Drug Synergism; Photosynthesis; Species Specificity; Superoxide Dismutase; Time Factors; Water Pollutants, Chemical

Short-term (24h) experiments were performed to examine the effect of anthracene (ANT) on Chlamydomonas reinhardtii cw92 grown in a batch culture system aerated with 2.5% CO(2). At concentrations ranging from 0.7 to 5.6 microM, ANT inhibited the growth of population in a concentration-dependent manner and EC(50) calculated amounted to 1.6 microM. At concentrations from 0.7 to 4.2 microM ANT stimulated respiration and inhibited the intensity of photosynthesis but did not affect chlorophyll content in the cells. ANT influenced chlorophyll a fluorescence parameters, measured by OJIP test (O, J, I and P are the different steps of fluorescence induction curve). ANT diminished the performance index (PI), the yield of primary photochemistry (phi(Po)), the yield of electron transport (phi(Epsilonomicron), the efficiency of moving the electron beyond Qa(-) (Psi(0)) and the fraction of active oxygen evolving complexes (OEC). The fraction of active PS II reaction centres in the treated samples dramatically dropped. The most pronounced changes in ANT-treated cells were observed in the stimulation of energy dissipation parameter (DI(0)/RC). The only OJIP parameter that was not influenced by ANT was energy absorption by photosynthetic antennae (ABS). The results lead to a conclusion that the inhibition of photosynthesis may be a consequence of unspecific ANT-membrane interaction, resulting from hydrophobic character of this hydrocarbon.

Topics: Animals; Anthracenes; Chlamydomonas reinhardtii; Chlorophyll; Chlorophyll A; Electron Transport; Fluorescence; Photosynthesis

Two species of marine microalgae, Isochrysis galbana 8701 and Skeletonema costatum, were exposed to low concentration of anthracene, and their cell density, contents of chlorophyll a, carotinoid and protein, and superoxide dismutase (SOD) activity were examined. It was showed that low concentration of anthracene (1.5-6.0 micrograms.L) could obviously stimulate the growth of these microalgae, and their protein, chlorophyll a, and carotinoid contents increased with increasing cell density. SOD of treated groups remained high activity, compared with the controlled group during the whole experiment.

Topics: Anthracenes; beta Carotene; Cell Division; Chlorophyll; Chlorophyll A; Dose-Response Relationship, Drug; Eukaryota; Marine Biology; Proteins; Superoxide Dismutase; Water Pollutants