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In this study, plantlets of two tobacco (Nicotiana tabacum L.) varieties that are clomazone-tolerant (cv. Xanthi) and clomazone-sensitive (cv. Virginie vk51) were subjected to low concentration of clomazone herbicide. The oxygen-evolving rate of isolated chloroplasts, chlorophyll a fluorescence transients, JIP-test responses, hydrogen peroxide contents, antioxidant enzyme activities, cytohistological results and photosynthetic pigment contents were recorded. The results indicated that the carotenoid content was 2-fold higher in Virginie, which had greater clomazone sensitivity than Xanthi. Virginie exhibited noticeable decreases in the LHC content (Chl a/b ratio), the maximum photochemical quantum efficiency of PSII (Fv/Fm), the performance index on the absorption basis (PIabs), and the electron flux beyond the first PSII QA evaluated as (1-VJ) with VJ=(FJ-F0)/(Fm-F0) as well as increases in the rate of photon absorption (ABS/RC) and the energy dissipation as heat (DI0/RC). These results suggest that PSII photoinhibition occurred as a consequence of more reduced PQ-pool and accumulated QA(-). The oxygen evolution measurements indicate that PSI electron transport activity was not affected by clomazone. The more significant accumulation of H2O2 in Virginie compared to Xanthi was due to the absence of ROS-scavenging enzymes, and presumably induced programmed cell death (PCD). The symptoms of PCD were observed by cytohistological analysis, which also indicated that the leaf tissues of clomazone-treated Virginie exhibited significant starch accumulation compared to Xanthi. Taken together, these results indicate that the variable tolerance to clomazone observed between Virginie and Xanthi is independent of the carotenoid content and could be related to the state of the LHC, the redox state of the PQ-pool, and the activity of detoxification enzymes., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

This work analyses the effects of alternation of light/dark periods pretreatment (AL) in tobacco plantlets (Nicotiana tabacum L. cv.Virginie vk51) growing in solution with low concentration of the clomazone herbicide. The experimentation has been carried out by exposing the plantlets to successive and regulated periods of light (16min light/8min dark cycles, PAR 50μmolm(-2)s(-1)) for three days. The photosynthesis efficiency was determined by mean of the chlorophyll fluorescence and JIP-test. The AL pretreatment improved the clomazone tolerance; this has been observed by the increase in the leaf area of the plant, the maximal photochemical quantum efficiency of PSII (Fv/Fm), the actual PSII efficiency (ФPSII), the performance index (PIabs), the electron flux beyond Quinone A (1-VJ), and also by the diminution of the energy dissipating into heat (DI0/RC). Furthermore, AL pretreatment led to low accumulation of hydrogen peroxide (H2O2) which proves that the scavenging enzymatic system have been activated before clomazone treatment. In the plantlets pretreated with AL, with regard to the ascorbate content, some of antioxidant enzyme whose function is associated with it have continued to scavenge reactive oxygen species (ROS) induced by clomazone, such as ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). So, the observed photooxidative damages induced by clomazone herbicide were noticeably reduced., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The effects of the herbicide Paraquat were investigated in honey bee larvae with attention focused on oenocytes. Honey bee larvae were exposed to Paraquat at different concentrations in the food: 0, 0.001, 0.01, 0.1 and 1 µg/kg. In controls, between 24 h and 48 h, oenocytes grew from 630.1 to 1643.8 µm(2) while nuclei changed in size from 124.9 to 245.6 µm(2). At 24 h, Paraquat induced a slight decrease in the size of oenocytes and nuclei. N-acetylcysteine (NAC), an antioxidant substance, slightly lowered the effects of Paraquat. At 48 h, Paraquat elicited a strong concentration-dependent decrease in the size of oenocytes, even at the lowest concentration. NAC reversed the effect of Paraquat at a concentration of ≥0.01 µg/kg. This reversion suggested different modes of action of Paraquat, with an oxidant action prevalent at concentrations ≥0.01 µg/kg. This study is the first which reports an effect of a pesticide at the very low concentration of 1 ng/kg, a concentration below the detection limits of the most efficient analytic methods. It shows that chemicals, including pesticides, are likely to have a potential impact at such exposure levels. We also suggest that Paraquat could be used as a suitable tool for investigating the functions of oenocytes.

A family of new uridine phosphocholine amphiphiles that were prepared using a convenient four-step synthetic route is described. Physicochemical studies (differential scanning calorimetry, small-angle X-ray scattering, UV-vis and circular dichroism spectroscopies, light microscopy, transmission electronic microscopy, and scanning electron microscopy) show that these amphiphiles spontaneously assemble into supramolecular structures including vesicles, fibers, hydrogels, and organogels. In aqueous solution, the amphiphiles possessing saturated alkyl chains self-assemble into DNA-like helical fibers in the crystalline state below T(m) and compact bilayers above the melting temperature (T(m)). The transition from bilayers to fibers is thermally reversible. Above a threshold concentration (>6% w/w), a hydrogel is formed due to an entangled network of the fibers. A therapeutic agent such as DNA can be entrapped within the hydrogel structure. In addition to forming bilayer vesicles and hydrogels in aqueous solution, these nucleoside amphiphiles also form organogels in cyclohexane above T(m). Scanning electron microscopy shows a continuous multilamellar phase in the organogels.

Two-dimensional gel electrophoretic analysis and histological studies were performed on somatic embryos in cypress. Embryogenic cultures were obtained from in vitro culture of immature seeds. On a modified Murashige and Skoog (MS) medium they showed an intense and repetitive cleavage polyembryogenesis phenomenon which maintained them in a continuous proliferating status instead of undergoing a complete embryogenic development. Only the addition of bovine serum albumin to the culture allowed somatic embryo development and maturation. Major histological differences were noticed between developing and nondeveloping embryogenic cultures. Attempts to find proteins that could be associated with developmental stages of somatic embryos have been achieved. Proteins were extracted and analyzed by two-dimensional electrophoresis from nondeveloping embryogenic cultures (S0) and from embryogenic cultures at three different stages of somatic embryo development: small size and rounded shape embryos (S1), increased size embryos with a well-developed suspensor (S2) and embryos with two well-separated cotyledons (S3). The results revealed some qualitative and quantitative protein variations between the two cultures. Some could be connected with the induction of pro-embryo differentiation whereas others should be more related to the mechanisms involved in somatic embryo development and maturation. Specific polypeptides associated with the presence of bovine serum albumin (BSA) in the medium have been detected.