Ecotoxicity of selected nano-materials to aquatic organisms.

Present knowledge concerning the ecotoxic effects of nano-materials is very limited and merits to be documented more fully. For this purpose, we appraised the toxicity of nine metallic nano-powders (copper zinc iron oxide, nickel zinc iron oxide, yttrium iron oxide, titanium dioxide, strontium ferrite, indium tin oxide, samarium oxide, erbium oxide, and holmium oxide) and of two organic nano- powders (fullerene-C60 and single-walled carbon nanotube or SWCNT). After a simple process where nano-powders (NPs) were prepared in aqueous solution and filtered, they were then bioassayed across several taxonomic groups including decomposers (bacteria), primary producers (micro-algae), as well as primary and secondary consumers (micro-invertebrates and fish). Toxicity data generated on the 11 NPs reflected a wide spectrum of sensitivity that was biological level-, test-, and endpoint-specific. With all acute and chronic tests confounded for these 11 NPs, toxicity responses spanned over three orders of magnitude: >463 mg/L (24 h LC50 of the invertebrate Thamnoplatyurus platyurus for fullerene-C60) / 0.3 mg/L (96 h EC50 of the invertebrate Hydra attenuata for indium tin oxide), that is a ratio of 1543. On the basis of the MARA (Microbial Array for Risk Assessment) assay toxic fingerprint concept, it is intimated that NPs may have different modes of toxic action. When mixed in a 1:1 ratio with a certified reference material (CRM) sediment, two solid phase assays and an elutriate assay, respectively, showed that five NPs (copper zinc iron oxide, samarium oxide, erbium oxide, holmium oxide, and SWCNT) were able to increase both CRM sediment toxicity and its elutriate toxicity. This initial investigation suggests that chemicals emerging from nanotechnology may pose a risk to aquatic life in water column and sediment compartments and that further studies on their adverse effects are to be encouraged.

Rapid chlorophyll a fluorescence transients of Lemna minor leaves as indication of light and exogenous electron carriers effect on photosystem II activity.

By using saturating flash, we investigated the change in the rapid fluorescence rise when Lemna minor leaf was exposed to different light conditions and treated with exogenous electron acceptors (methyl viologen and duroquinone) and electron donor (hydroxylamine). Investigation was carried out by using combined pulse amplitude modulated fluorometer and plant efficiency analyzer system, which were employed simultaneously to provide different light conditions and to induce rapid fluorescence rise respectively. We have shown that when leaf of L. minor was exposed to different conditions of illumination, rapid fluorescence rise was greatly influenced by the electron transport functions beyond quinone A-plastoquinone reduction. This was indicated by the change in both fluorescence yield and appearance time of the different transients. When exogenous electron donor (hydroxylamine) and acceptors (methyl viologen and duroquinone) were applied in in vivo condition, we showed that rapid fluorescence rise represented a reliable indicator of PSII-PSI electron transport state and energy dissipation process.

Chitosan improves development, and protects Vitis vinifera L. against Botrytis cinerea.

We evaluated the potential of chitosan both to stimulate plant development and to induce protection from Botrytis cinerea in Vitis vinifera L. plantlets. The presence of 1.75% (v/v) chitogel in the culture medium was the optimal concentration for in vitro grapevine plantlet growth, as determined by measurements on enhancement of root and shoot biomass. Photosynthesis and related parameters were also stimulated in chitogel-treated plantlets. Chitogel reduced the development of Botrytis cinerea and induced cytological alterations to the pathogen. When challenged with the fungus, a significant decrease in disease incidence was observed in plants growing on medium supplemented with chitogel. Furthermore, exogenous foliar applications of chitogel to plantlets growing on chitogel-free medium sensitized them so as to be protected against Botrytis cinerea attack. Our results indicate that chitogel can be used in the vineyard as a means to attain protection against Botrytis cinerea and that its application may counteract the wide use of chemical pesticides.

Photosynthetic responses of Lemna minor exposed to xenobiotics, copper, and their combinations.

The effects on the photosynthetic process of copper and pesticides, used in vineyards, and their combinations, were investigated by measuring different chlorophyll fluorescence parameters in Lemna minor. Cu and flumioxazin had a severe impact on duckweed since a decrease in their photosynthetic capacity was detected after 24h of exposure to 200 and 1 microg.L(-1), respectively. However, fungicides used to control Botrytis cinerea (procymidone, pyrimethanil, and fludioxonil) seem to have no marked effects on duckweed even at very high concentrations (50 mg.L(-1)). Analysis of the combinations between copper (200 microg.L(-1)) and pesticides revealed different patterns of response: a synergistic effect was observed when Cu(2+) was added to flumioxazin (1 microg.L(-1)). In contrast, an antagonism was detected when duckweed was exposed to a mixture of Cu(2+) and fludioxonil or procymidone. However, these interactions always tended toward additivity when pesticide concentrations increased. Additivity was also observed for the Cu(2+)-pyrimethanil mixture at each fungicide concentration.

Evidence of chlorophyll synthesis pathway alteration in desiccated barley leaves.

In etiolated leaves, saturating flash of 200 ms induces phototransformation of protochlorophyllide (Pchlide) F655 into chlorophyllide (Chlide), then into Chl through reactions which do not need light sensibilisation. The synthesis of Chl is known to be slowed down in etiolated leaves exposed to desiccation stress. In order to analyse the intensity and time-course of Chlide transformation into Chl, we used the fluorescence emission of etiolated leaves previously exposed to a 200 ms saturating flash. We used low-temperature fluorescence spectroscopy to reveal the inhibition site of Chl synthesis in etiolated barley leaves exposed to water stress. Shibata shift appears as the main target point of the water deficit. It was found that water deficit inhibits partially active Pchlide F655 regeneration. Also, esterification of Chlide into Chl is impaired. It appears that these inhibitory effects alter the appearance of PSII active reaction centres.