The uptake of Se(IV) and its effects on the physiological and biochemical characteristics of duckweed (Lemna minor L.) have been studied. Duckweed plants were cultivated in controlled conditions for 7 weeks in different concentrations of Na selenite: 0.5, 1, 2, 5 (exposed 42 days) and 10 mg Se L⁻¹(survived 7–21 days). The addition of 1 mg Se L⁻¹did not negatively affect photochemical efficiency whilst respiratory potential increased in weeks 2–4 compared to control. The addition of 1 mg Se(IV) L⁻¹increased the amount of chlorophyll a in weeks 3 and 4 and the amount of carotenoids in weeks 1, 3 and 5. Concentrations of 2 and 5 mg Se L⁻¹negatively affected photochemical efficiency in weeks 3 and 4, and increased respiratory potential in comparison to the control in weeks 1–4, whilst beyond week 4, the respiratory potential decreased. Plants exposed to the highest concentration of Se(IV) had to be replaced twice during the experiment because they were dying. That was reflected in photochemical efficiency as well as in respiratory potential, which decreased in time. The content of Se in duckweed increased with the increasing concentration of Se: plants growing in 0.5 mg Se L⁻¹contained 0.9 mg Se g⁻¹DM and plants exposed to 5 mg Se L⁻¹contained 5.8 mg Se g⁻¹DM. The group of plants exposed to 10 mg Se L⁻¹for 21 days contained 19.5 mg Se g⁻¹DM. Our study revealed that duckweed absorbed high amount of Se(IV) from the water.

Nanoparticles (NPs) are an increasingly common contaminant in agro-environments, and their potential effect on genetically modified (GM) crops has been largely unexplored. GM crop exposure to NPs is likely to increase as both technologies develop. To better understand the implications of nanoparticles on GM plants in agriculture, we performed a glasshouse study to quantify the uptake of Fe₂O₃ NPs on transgenic and non-transgenic rice plants. We measured nutrient concentrations, biomass, enzyme activity, and the concentration of two phytohormones, abscisic acid (ABA) and indole-3-acetic acid (IAA), and malondialdehyde (MDA). Root phytohormone inhibition was positively correlated with Fe₂O₃ NP concentrations, indicating that Fe₂O₃ had a significant influence on the production of these hormones. The activities of antioxidant enzymes were significantly higher as a factor of low Fe₂O₃ NP treatment concentration and significantly lower at high NP concentrations, but only among transgenic plants. There was also a positive correlation between the treatment concentration of Fe₂O₃ and iron accumulation, and the magnitude of this effect was greatest among non-transgenic plants. The differences in root phytohormone production and antioxidant enzyme activity between transgenic and non-transgenic rice plants in vivo suggests that GM crops may react to NP exposure differently than conventional crops. It is the first study of NPs that may have an impact on GM crops, and a realistic significance for food security and food safety.

The gametogenic cycle of the Cerastoderma glaucum was analyzed using both qualitative and semi-quantitative methods. The condition index and glycogen concentrations were determined in order to provide information on energy storage. The cockles were collected monthly from a Bayyadha site located 15 km south of Sfax City (Gulf of Gabès) between January 2007 and January 2008. From histological point of view, we applied two approaches: (i) the qualitative method describing the various stages of gamete development for males and females during a cycle of 13 months, and (ii) the semi-quantitative method concerning the estimation of different tissue surfaces. The results showed that there is evidence of three periods of reproduction in this population. A comparison between the surfaces occupied by the three organs showed that the foot and the gonad surfaces are higher than the surface of the adductor muscle. This could suggest that these two organs are more involved in the process of glycogen reserve storage. The results of the glycogen concentrations in the different tissues (gonad, adductor muscle, and “remainders”) show that during the second and third periods of reproduction, glycogen was stored in the adductor muscle and in the remainder during sexual rest, and in the gonad during the gametogenesis phases in order to supply the reproductive effort. On the contrary, in the first period of reproduction, the low concentrations of glycogen recorded in the gonad coincided with its high degree of development. This fact could be related to environmental conditions (low temperature and food) recorded during this period.

Hydroponic experiments were conducted with rice seedlings (Oryza sativa L. cv. XZX45) exposed to gallium nitrate (Ga³⁺) to investigate the accumulation of Ga in plant tissues and phytotoxic responses. Results showed that phyto-transport of Ga was apparent, and roots were the dominant site for Ga accumulation. The total accumulation rates of Ga responded biphasically to Ga treatments by showing increases at low (1.06–8.52 mg Ga/L) and constants at high (8.52–15.63 mg Ga/L) concentrations, suggesting that accumulation kinetics of Ga followed a typical saturation curve. Higher amount of Ga accumulation in plant tissues led to significant inhibition in relative growth rate and water use efficiency in a dose-dependent manner. DNA-protein cross-links (DPCs) analysis revealed that overaccumulation of Ga in plant tissues positively stimulated formation of DPCs in roots. Likewise, the measure of root cell viability evaluated by Evan blue uptake showed a similar trend. These results suggested that Ga can be absorbed, transported, and accumulated in plant materials of rice seedlings. Overaccumulation of Ga in plant tissues provoked the formation of DPCs in roots, which resulted in cell death and growth inhibition of rice seedlings.

Integrons are bacterial genetic elements known to be active vectors of antibiotic resistance among clinical bacteria. They are also found in bacterial communities from natural environments. Although integrons have become especially efficient for bacterial adaptation in the particular context of antibiotic usage, their role in natural environments in other contexts is still unknown. Indeed, most studies have focused on integrons and the spread of antibiotic resistance in freshwater or soil impacted by anthropogenic activities, with only few on marine environments. Notably, integrons show a wider diversity of both gene cassettes and integrase gene in natural environments than in clinical environments, suggesting a general role of integrons in bacterial adaptation. This article reviews the current knowledge on integrons in marine environments. We also present conclusions of our studies on polluted and nonpolluted backgrounds.

Four subsurface horizontal-flow constructed wetlands (CWs) at a pilot scale planted with a polyculture of the tropical plants Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) were evaluated for 7 months. The CW cells with an area of 17.94 m² and 0.60 m (h) each and 0.5 m of gravel were operated at continuous gravity flow (Q = 0.5 m³ day⁻¹) and a theoretical HRT of 7 days each and treating landfill leachate for the removal of filtered chemical oxygen demand (CODf), BOD₅, TKN, NH₄ ⁺, NO₃ ⁻, PO₄ ³⁻–P and Cr(VI). Three CWs were divided into three sections, and each section (5.98 m²) was seeded with 36 cuttings of each species (plant density of six cuttings per square metre). The other unit was planted randomly. The final distributions of plants in the bioreactors were as follows: CW I (He-Ce-Gs), CW II (randomly), CW III (Ce-Gs-He) and CW IV (Gs-He-Ce). The units received effluent from a high-rate anaerobic pond (BLAAT®). The results show a slightly alkaline and anoxic environment in the solid-liquid matrix (pH = 8.0; 0.5–2 mg L⁻¹ dissolved oxygen (DO)). CODf removal was 67 %, BOD₅ 80 %, and TKN and NH₄ ⁺ 50–57 %; NO₃ ⁻ effluents were slightly higher than the influent, PO₄ ³⁻–P (38 %) and Cr(VI) between 50 and 58 %. CW IV gave the best performance, indicating that plant distribution may affect the removal capacity of the bioreactors. He and Gs were the plants exhibiting a translocation factor (TF) of Cr(VI) >1. The evaluated plants demonstrated their suitability for phytoremediation of landfill leachate, and all of them can be categorized as Cr(VI) accumulators. The CWs also showed that they could be a low-cost operation as a secondary system for treatment of intermediated landfill leachate (LL).

When exposed to higher Pb²⁺ concentration, Phanerochaete chrysosporium secreted higher content of oxalate and thiol compounds. An earlier and faster increase in oxalate was observed after short-term exposure, comparing with a gentle increase in the thiol compounds. In the extracellular polymeric substances (EPS) extract, more oxalate and T-SH were detected when the initial Pb²⁺ was higher, and the variations were different from the situation in the culture medium. In EPS solution, the oxalate amount was more closely related with Pb than that of thiol compounds. pH condition in the whole Pb removal process by P. chrysosporium ranged from 4 to 6.5 and was more beneficial for the binding of Pb²⁺ to carboxylic groups in the oxalic acid. More Pb²⁺ induced more EPS amount, and the increase of EPS amount influenced the immobilized oxalate more seriously. The present study can supply more comprehensive information about the metal passivation mechanism in white-rot fungi and provide meaningful references for an enhanced removal of heavy metals.

We investigated the concentration and composition of polychlorinated biphenyls (PCBs) in paddy soils and rice tissues and the associated potential health risks in the urban agricultural areas of the Pearl River Delta (PRD), South China. The results indicated that highly chlorinated PCBs were more prominent in soil when the concentrations of low-molecular-weight PCBs were relatively high in rice plants. There was a trend of decreasing PCB concentrations with soil depth and a significant correlation between PCBs and the total organic carbon or total nitrogen concentration in section soils. The PCB concentrations followed the order of root > leaf > stem > grain. Although the dioxin toxicity equivalency values and estimated daily intake levels (based direct and indirect consumption) were lower than in other seriously contaminated regions, there is still a need to monitor PCB pollution in urban agriculture because of the PCB emissions from capacitor storage following the rapid urbanization experienced in the PRD.

The microbial communities of bulk soil of rice paddy fields under an ancient organic agriculture regimen, consisting on an alfalfa-rice rotation system, were characterized. The drained soil of two adjacent paddies at different stages of the rotation was compared before rice seeding and after harvesting. The relationships among the soil microbial, physicochemical, and biochemical parameters were investigated using multivariate analyses. In the first year of rice cropping, aerobic cultivable heterotrophic populations correlated with lineages of presumably aerobic bacteria (e.g., Sphingobacteriales, Sphingomonadales). In the second year of rice cropping, the total C content correlated with presumable anaerobic bacteria (e.g., Anaerolineae). Independently of the year of rice cropping, before rice seeding, proteolytic activity correlated positively with the cultivable aerobic heterotrophic and ammonifier populations, the soil catabolic profile and with presumable aerobes (e.g., Sphingobacteriales, Rhizobiales) and anaerobes (e.g., Bacteroidales, Anaerolineae). After harvesting, strongest correlations were observed between cultivable diazotrophic populations and bacterial groups described as comprising N₂ fixing members (e.g., Chloroflexi-Ellin6529, Betaproteobacteria, Alphaproteobacteria). It was demonstrated that chemical parameters and microbial functions were correlated with variations on the total bacterial community composition and structure occurring during rice cropping. A better understanding of these correlations and of their implications on soil productivity may be valid contributors for sustainable agriculture practices, based on ancient processes.

Antimony occurs locally at high concentrations in some mineralized soils. Very little is known about behavior of antimony in plants. In this study, we analyzed the soil and vegetation of two mining areas in Iran, Patyar, and Moghanlo. Total Sb concentrations in soil were 358–3482 mg/kg in Moghanlo and 284–886 mg/kg in Patyar. Corresponding Sb concentrations in plant shoots were 0.8–287 and 1.3–49 mg/kg, respectively. In both areas, foliar Sb concentrations increased with acid-extractable soil Sb, although the slope was about 2-fold steeper for Patyar than for Moghanlo. Regressing the foliar concentrations on water-soluble Sb yielded identical slopes for both areas, suggesting that the soluble fraction of Sb rather than total Sb is the direct determinant of foliar Sb accumulation. Both in Patyar and Moghanlo, only a minor part of the total variance of shoot Sb was explained by soluble Sb. The major part was explained by plant species, demonstrating that plant taxonomic identity is the most important determinant of foliar Sb accumulation capacity in both areas. The translocation factor (TF) was highly variable too, with species as the only significant variance component. Only four species were able to accumulate more than 100 mg/kg Sb in their leaves. Among these species, Achillea wilhelmsii and Matthiola farinosa were by far the best Sb accumulators, with, on average, 141 and 132 mg/kg Sb in their leaves. Of these two, only Matthiola farinosa consistently maintained TF values far above unity across the whole range of soluble Sb in Moghanlo.