The chloroplast genome has been widely addressed to describe genetic diversity in tree species with regard to phylogeographic studies. In contrast, there is little information on the pattern of genetic differentiation in tolerant and sensitive tree populations, responding to different types of environmental stress. The results demonstrate that chloroplast microsatellites markers are useful tools for elucidating and for testing the pattern of genetic differentiation in stress-exposed populations of Norway spruce, offering to prove the feasibility of marker-aided selection in future

Polybrominated diphenyl ethers (PBDEs) are a series of highly persistent organic pollutants (POPs) ubiquitously distributed in marine environments. As key primary producers, microalgae are the start of PBDEs bioaccumulations and vulnerable to their toxicities. In order to deeply investigate the toxic mechanism of PBDEs on microalgal cells, the occurrence of programmed cell death (PCD) in a model diatom Thalassiosira pseudonana and its possible mediating mechanism were studied. The results indicated: cell death of T. pseudonana happened under the stress of BDE-47, which was proved to be PCD based on the correlations with three biochemical markers (DNA fragmentation, phosphatidylserine externalization and caspase activity) and three molecular markers [Metacaspase 2 gene (TpMC2), Death-associated protein gene (DAP3) and Death-specific protein 1 gene (TpDSP1)]; Furthermore, the changes of cellular ROS levels were correlated with the PCD markers and the dead cell rates, and the cell membrane and the chloroplast were identified as the major ROS production sites. Therefore, we concluded that PCD might be an important toxic mechanism of PBDEs on microalgal cells, and that chloroplast- and cell membrane-produced ROS was an important signaling molecule to mediate the PCD activation process. Our research firstly indicated microalgal PCD could be induced by PBDEs, and increased our knowledge of the toxic mechanisms by which POPs affect microalgal cells.

Despite growing concern about the occurrence of microplastics in aquatic ecosystems there is only rudimentary understanding of the pathways through which any adverse effects might occur. Here, we assess the effects of polystyrene microplastics (PS-MPs; <70 μm) on a common and widespread algal species, Chlorella sorokiniana. We used laboratory exposure to test the hypothesis that the lipids and fatty acids (FAs) are important molecules in the response reactions of algae to this pollutant. Cultivation with PS-MPs systematically reduced the concentration of essential linoleic acid (ALA, C18:3n-3) in C. sorokiniana, concomitantly increasing oleic acid (C18:1n-9). Among the storage triacylglycerols, palmitoleic and oleic acids increased at the expenses of two essential fatty acids, linoleic (LIN, C18:2n-6) and ALA, while PS-MPs had even more pronounced effects on the fatty acid and hydrocarbon composition of waxes and steryl esters. The FA composition of two major chloroplast galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), were affected implying changes in the conformational structure of photosynthetic complexes in ways that can impair the photosynthesis. These data reveal how exposure to polystyrene microplastics can modify the concentrations of lipid molecules that are important intrinsically in cell membranes, and hence the lipid bilayers that could form an important barrier between algal cellular compartments and plastics in the aquatic environment. Changes in lipid synthesis and fatty acid composition in algae could also have repercussions for food quality, growth and stressor resistance in primary consumers. We advocate further studies of microplastics effects on the lipid composition of primary producers, and of their potential propagation through aquatic food webs.

Pharmacologically active compounds found in reclaimed wastewater irrigation or animal manure fertilizers pose potential risks for agriculture. The mechanism underlying the effects of ketoprofen on rice (Oryza sativa L.) seedlings was investigated. The results showed that low concentrations (0.5 mg L⁻¹) of ketoprofen slightly stimulate growth of rice seedlings, while high concentrations can significantly inhibit growth by reducing biomass and causing damage to roots. Ketoprofen affects photosynthetic pigment content (Chla, Chlb, and carotenoids) and chlorophyll synthesis gene (HEMA, HEMG, CHLD, CHLG, CHLM, and CAO) expression. Fluorescence parameters such as minimum fluorescence (F₀), maximum fluorescence (Fₘ), variable fluorescence (Fᵥ), potential photosynthetic capacity (Fᵥ/F₀), maximum quantum efficiency of PSII photochemistry (Fᵥ/Fₘ), electron transfer rate (ETR), and Y(II), Y(NPQ), Y(NO) values were affected, showing photosynthetic electron transfer was blocked. Active oxygen radical (O₂•−and H₂O₂), malondialdehyde and proline content increased. Superoxide dismutase, catalase and ascorbate peroxidase activities, glutathione content and antioxidant-related gene (FSD1, MSD1, CSD1, CSD2, CAT1, CAT2, CAT3, APX1, APX2) expression were induced. Higher integrated biomarker response values of eight oxidative stress response indexes were obtained at higher ketoprofen concentrations. Ultrastructure observation showed that ketoprofen causes cell structure damage, chloroplast swelling, increase in starch granules, and reduction in organelles. This study provides some suggested toxicological mechanisms and biological response indicators in rice due to stress from pharmacologically active compounds.

CuO engineered nanoparticles (NPs) are of increasing concern due to their extensive use in daily life and adverse effect on aquatic organisms. The investigations on the toxicity of CuO NPs to aquatic plants through uptake from roots versus fronds are limited. This paper discusses the interactions of CuO NPs with Lemna minor, a floating plant. After CuO NPs (150 μg L⁻¹) exposure for 7 days, the frond number, frond surface area and dry weights of whole plants significantly decreased by 32%, 47% and 33%; the responses were dose-dependent. Microscopy imaging showed that the epidermis was severely damaged in fronds, edges were severely sloughed off and cell integrity was damaged in roots. Shrinkage of both chloroplast and starch grains were observed in the frond cells. Internalization of CuO NPs in root and frond cells during CuO NPs (1 mg L⁻¹) exposure was confirmed with the root Cu levels of Lemna minor being three times higher than the fronds by using transmission electron microscopy and flame atomic absorption spectrophotometry. Reactive oxygen species, mainly H₂O₂ (increased by 56%) and ·OH (increased by 57%), accumulated in Lemna minor tissues in response to CuO NPs exposure. Moreover, chloroplasts were confirmed as a site of ROS production. These findings are helpful for better understanding the biological responses of aquatic plants upon NPs exposure.

To increase understanding on the mechanisms of cultivar difference in contaminant accumulation in crops, this study was designed to compare the physiological responses to di-n-butyl phthalate (DBP) exposure between low (Lvbao70) and high (Huaguan) DBP cultivars of Chinese flowering cabbage (Brassica parachinensis L.). Under high DBP exposure, significant differences in various physiological responses were observed between the two cultivars, which might account for the variation in DBP accumulation. Ultrastructure observation also showed different alterations or damages in the mesophyll cell structures between both cultivars, especially for the chloroplast disintegration, starch grain quantity, and plastoglobuli accumulation. Compared with Huaguan, Lvbao70 suffered greater decreases in biomass, chlorophyll content, carbon assimilation, gas exchange parameters, photosynthetic electron transport capacity, and antioxidase activities, which would have resulted in a great reduction of photosynthetic capacity. Although Lvbao70 enhanced energy dissipation and activities of some antioxidant enzymes, they did not provide sufficient protection against oxidative damage caused by DBP. The result suggested that the lower DBP tolerance of Lvbao70 might be associated with its poor physiological performances, which was responsible for its lower DBP accumulation to protect itself from toxicity. Additionally, Lvbao70 had a significantly lower transpiration rate and stomatal conductance than Huaguan, which might be the factors regulating DBP-accumulation variation.

Photosynthesis, the basal manufacturing process in the earth is habitually restricted by airborne micropollutants such as phenanthrene (PHE). Here, we show that 24-epibrassinolide (EBR), a bioactive plant steroid is able to keep higher photosynthetic capacity consistently for a long period under a shoot-imposed PHE stress in tomato. EBR-promoted photosynthetic capacity and efficiency eventually resulted in a 37.5% increase of biomass under PHE stress. As primary response, transcripts of antioxidant genes were remarkably induced by EBR in PHE-treated plants. Activities of antioxidant and detoxification enzymes were also enhanced by EBR. Notably, EBR-induced higher antioxidant potential was associated with reduced levels of H2O2 and O2—, resulting in a 32.7% decrease of content of malondialdehyde in the end of experiment and relatively healthy chloroplast ultrastructure in EBR + PHE treatment compared with PHE alone. These results indicate that EBR alleviates shoot-imposed PHE phytotoxicity by maintaining a consistently higher photosynthetic capacity and antioxidant potential in tomato.

The effects of the ionic liquid 1-octyl-3-methylimidazolium chloride ([OMIM]Cl) was studied in hydroponically grown rice seedlings. Observed effects included increased root length and weight at concentrations of 0.1 mg/L [OMIM]Cl, however, as concentrations increased a reversed response was observed where roots and stems grew shorter and the weight decreased. The inhibitory concentration 50 (IC50,5d) values for root length and stem length were 0.59 mg/L and 0.70 mg/L, respectively. The Hill reaction activity and root system activity in [OMIM]Cl-treated rice seedlings were observed to be lower than the controls, however, root membrane permeability increased. The antioxidant enzyme activity in roots decreased, while in leaves there was an initial stimulation followed by a decrease. Malondialdehyde (MDA) content was found to be greater in seedlings subjected to [OMIM]Cl treatment. The cellular structures, such as chloroplasts, mitochondria and rough endoplasmic reticulum in rice root and leaf cells were affected at concentrations of 0.6 mg/L [OMIM]Cl.

Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis, it was found that the ultrastructure of chloroplasts were changed, the shape of the chloroplasts altered and the numbers of grana that were asymmetrical increased; the numbers of grana and thylakoids decreased under the stress of Cd and Zn. The results indicated that the complex pollution involving Cd and Zn resulted in the membrane system of chloroplasts being damaged. When external phosphorus was applied, the numbers of damaged chloroplasts were significantly reduced and the nucleoli were better formed than those that did not receive phosphorus treatment. Moreover, many phosphate deposits were found in the vacuoles and on the surface of the roots, which were formed by phosphorus complexing with Cd (Ksp = 2.53 x 10-33) and Zn (Ksp = 9.00 x 10-33), respectively. Treatment with phosphorus conduced an increased chlorophyll content in plants compared with those that did not receive external phosphorus. External P could decrease the bioavailability of Cd and Zn.

Butyl Xanthate (BX) is a typical flotation reagent used to extract non-ferrous nickel ores, discharged into the surrounding environment of mining areas in large quantities. However, few studies have focused on the toxicity of combined pollution of BX and nickel (Ni) on aquatic plants, especially phytoplankton, the main producer of aquatic ecosystems. The toxicity and potential mechanism of single and combined pollution of BX and Ni at different concentrations (0–20 mg L⁻¹) on typical freshwater algae (Chlorella pyrenoidosa) were studied. BX slightly stimulated the growth of C. pyrenoidosa on the first day, but Ni and Ni/BX mixture significantly inhibited it during incubation. Results showed that the inhibition rate (I) of the pollutants on the growth of C. pyrenoidosa followed the order: Ni/BX mixture > Ni > BX. The 96-h 20% effective inhibitory concentrations (96h-EC₂₀) of Ni and BX on C. pyrenoidosa growth were 3.86 mg L⁻¹ and 19.25 mg L⁻¹, respectively, indicating C. pyrenoidosa was sensitive to pollutants. The content of total soluble protein (TSP) and chlorophyll a (Chl-a) changed significantly, which may be caused by the damage of pollutants to cell structures (cell membranes and chloroplasts). In addition, the I of pollutants on C. pyrenoidosa growth was related to dose, superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA). The increasement of reactive oxygen species (ROS), antioxidant enzymes (SOD and CAT), and MDA content, suggested C. pyrenoidosa suffered from oxidative stress, leading to lipid oxidation. These results will help to understand the toxicity mechanism of pollutants in typical mining areas and assess the environmental risks of pollutants to primary producers in aquatic ecosystems.