Institute of Hydrobiology, Chinese Academy Of Sciences
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The pH of the leaf apoplast is critical for the formation of Pseudomonas syringae-induced lesions on leaves of the common bean (Phaseolus vulgaris)
No full textInoculating a virulent strain of Pseudomonas syringae pv. phaseolicola (Pph) into the leaf of common bean (Phaseolus vulgaris) causes the leaf apoplast to alkalinize. Whether or not this apoplastic pH event facilitates virulence of Pph in interaction with common bean is unclear. For elucidating this topic, (i) Pph colonization of the common bean leaf apoplast, (ii) the formation of bacterial lesions, and (iii) apoplastic sucrose concentration were investigated in relation to the apoplastic leaf pH. For this, the Pph-induced leaf apoplastic alkalinization was attenuated by spray application of either a synthetic auxin or an acidic pH buffer. Apoplastic pH was quantified in planta via microscopy-based pH imaging. Apoplastic washing fluids were extracted to quantify both colonization of bacteria in leaf apoplast and the concentration of apoplastic sucrose. Results reveal that the apoplastic alkalinization facilitated bacterial colonization of the apoplast. Number of colony forming units and area of bacterial lesions were reduced when Pph-induced apoplastic alkalinization was attenuated by foliar application of a synthetic auxin or acidic pH buffer. Application of both agents attenuated the Pph-induced increase of sucrose in the leaf apoplast, which is nutrient for bacteria. Data demonstrate that the Pph-mediated leaf apoplastic alkalinisation favours bacterial colonization
Identification and quantification of titanium nanoparticles in surface water: A case study in Lake Taihu, China
No full textThe accurate detection and quanti cation of nanoparticles (NPs) in aquatic environments are essential for toxicological and ecological risk assessment. Herein, we used single particle inductively coupled mass spectroscopy (SP-ICP-MS) to quantify titanium nanoparticles (Ti-NPs) in the extraction fractions of surface waters, and transmission electron microscopy coupled with an energy dispersive X-ray spectrometer (TEM-EDS) to specifically identify the nanoparticles. By using gold-NPs as reference standard, this approach achieved a Ti-NPs size detection limit in water of 25 nm with a particle number concentration limit of 10(2) particles/ml. We measured Ti-NPs concentrations in surface waters from Lake Taihu, China. The results revealed that the particles concentration was 2.78 x 10(5) particles/ml with the mean size of 67 nm in October 2016, and the particles concentration of 2.28 x 10(5) particles/ml with the mean size of 65 nm in April 2018, respectively. Based on TEM-EDS observation, various shapes of Ti-NPs were further identified, including regular cubes, long rods and flaky. We further measured the total organic carbon (TOC), and found that there was a positive correlation between Ti-NPs and TOC. This method enabled accurate detection and quantification of Ti-NPs concentration in environmental surface waters, which could be hugely useful for environmental risk assessment in aquatic systems
Anatomical and histochemical features of Brasenia schreberi (Cabombaceae) shoots
No full textThe present research on Brasenia schreberi, a member of the aquatic, basal angiosperm family, Cabombaceae, investigates the anatomy and histochemistry of this critically endangered plant. The shoots of B. schreberi have vertical rhizomes, horizontal rhizomes, and stolons with peduncles and leaves. Most stems typically have polysteles with bicollateral vascular bundles, each with two groups of primary xylem tracheids and primary phloem sieve tube elements, an endodermis with Casparian bands around each vascular bundle, and epidermis with glandular trichomes or "mucilaginous hairs" and discontinuous cuticle. Most stems have a protoxylem lacuna between the two regions of primary xylem and primary phloem in each bicollateral vascular bundle and extensive aerenchyma in ground tissues. Epidermal glandular trichomes are composed of two disk-like stalk cells and enlarged glandular or hair cells with storage space and mucilage, which covers the cells. The structural features of B. schreberi are generally consistent with those of other aquatic basal angiosperms and with its adaptation to an aquatic environment
Spatial pattern and determinants of global invasion risk of an invasive species, sharpbelly Hemiculter leucisculus (Basilesky, 1855)
No full textInvasive species have imposed huge negative impacts on worldwide aquatic ecosystems and are generally difficult or impossible to be eradicated once established. Consequently, it becomes particularly important to ascertain their invasion risk and its determinants since such information can help us formulate more effective preventive or management actions and direct these measures to those areas where they are truly needed so as to ease regulatory burdens. Here, we examined the global invasion risk and its determinants of sharpbelly (Hemiculter leucisculus), one freshwater fish which has a high invasive potential, by using species distribution models (SDMs) and a layer overlay method. Specifically, first an ensemble species distribution model and its basal models (developed from seven machine learning algorithms) were explored to forecast the global habitat-suitability and variables importance for this species, and then a global invasion risk map was created by combining habitat-suitability with a proxy for introduction likelihood (entailing propagule pressure and dispersal constraints) of exotic sharpbelly. The results revealed that (1) the ensemble model had the highest predictive power in forecasting sharpbelly's global habitat-suitability; (2) areas with high invasion risk by sharpbelly patchily spread over the world except Antarctica; and (3) the Human Influence Index (HII), rather than any of the bioclimatic variables, was the most important factor influencing sharpbelly' future invasion. Based on these results, the present study also attempted to propose a series of prevention and management strategies to eliminate or alleviate the adverse effects caused by this species' further expansion. (C) 2019 Elsevier B.V. All rights reserved
The combined effect of dissolved oxygen and COD/N on nitrogen removal and the corresponding mechanisms in intermittent aeration constructed wetlands
No full textIn this study, the combined effect of dissolved oxygen (DO) and COD/N on nitrogen (N) removal as well as the corresponding mechanisms were investigated in aerated constructed wetlands (CWs). At each investigated COD/N level, the ammonium removal efficiency increased as DO concentration increased. However, the highest total N removal efficiency occurred at different DO concentration at each COD/N level. The results of functional gene analysis and cyclic N profile studies indicated that DO supply and COD/N influence the N removal performance, which is not only exert a direct effect on nitrification-denitrification process, but also change N removal pathway in intermittent aerated CWs. At a relatively high influent COD/N of 20, the simultaneous nitrification and denitrification (SND) via nitrite was almost the exclusive N removal pathway at all investigated DO concentration. With the decrease of COD/N from 20 to 2 at DO of similar to 1.8, similar to 3.5 and similar to 6.0 mg/L, SND efficiency all decreased, however, its decreasing rate was much higher at relatively high DO level of similar to 6.0 mg/L than that at DO levels of similar to 1.8 and similar to 3.5 mg/L. In comparison, a simultaneously partial nitrification, anammox and denitrification was established at DO of similar to 0.8 mg/L along with reducing influent COD/N
Biological soil crust succession in deserts through a 59-year-long case study in China: How induced biological soil crust strategy accelerates desertification reversal from decades to years
No full textThe regeneration of induced biological soil crusts (IBSCs) is regarded as an effective strategy for combating desertification. Three types of BSCs, namely, cyanobacterial, lichen and moss, are well-accepted as the main succession phases and are hypothesized to represent a continuous process. Herein, natural BSCs (NBSCs) and IBSCs with accurate ages from a 59-year-long field study were investigated to understand the entire BSC succession process. Shifts in nutrient levels, microbial composition and ecological functions suggested that cyanobacterial inoculation successfully accelerated BSC succession from decades to years by promoting the microbial multifunctions related to carbon and nitrogen fixation. The four state transitions of the BSC community accompanied by the turn-over of carbon and nitrogen fixators provide clues to the factors restricting the recovery process and climax of arid ecosystems. This study provides the first description of the continuous BSC succession, comprehensively discusses the mechanisms of BSC formation and succession and provides important guides for selection of strategies for the engineering reversals of desertification.</p
The characteristics of glucose homoeostasis in grass carp and Chinese longsnout catfish after oral starch administration: a comparative study between herbivorous and carnivorous species of fish
No full textAn oral starch administration trial was used to evaluate glucose homoeostasis in grass carp (Ctenopharyngodon idella) and Chinese longsnout catfish (Leiocassis longirostris Gunther). Fish were administered with 3 g of a water and starch mixture (with 3:2 ratio) per 100 g body weight after fasting for 48 h. Fish were sampled at 0, 1, 3, 6, 12, 24 and 48 h after oral starch administration. In grass carp, plasma levels of glucose peaked at 3 h but returned to baseline at 6 h. However, in Chinese longsnout catfish, plasma glucose levels peaked at 6 h and returned to baseline at 48 h. The activity of intestinal amylase was increased in grass carp at 1 and 3 h, but no significant change in Chinese longsnout catfish was observed. The activity of hepatic glucose-6-phosphatase fell significantly in grass carp but change was not evident in Chinese longsnout catfish. The expression levels and enzymic activity of hepatic pyruvate kinase increased in grass carp, but no significant changes were observed in the Chinese longsnout catfish. Glycogen synthase (gys) and glycogen phosphorylase (gp) were induced in grass carp. However, there was no significant change in gys and a clear down-regulation of gp in Chinese longsnout catfish. In brief, compared with Chinese longsnout catfish, grass carp exhibited a rapid increase and faster clearance rate of plasma glucose. This effect was closely related to significantly enhanced levels of digestion, glycolysis, glycogen metabolism and glucose-induced lipogenesis in grass carp, as well as the inhibition of gluconeogenesis
Sex-dependent and organ-specific toxicity of silver nanoparticles in livers and intestines of adult zebrafish
No full textSilver nanoparticles (AgNPs) have been increasingly manufactured and thus are increasingly detected in aquatic systems. However, there are still some overlooked factors (e.g., organism sex) in the field of nanotoxicological assessment. In this study, to explore the role of sex in nanotoxicity, adult male and female zebrafish were exposed to 100 mu g/L of two uncoated commercial AgNPs with primary sizes 20 nm and 80 nm for 2 weeks, after which the impacts of AgNPs on intestines and livers of both male and female zebrafish were assessed using a suite of biomarkers. Results demonstrated that the intestinal Na/KATPase activity as well as the superoxide dismutase activity in male zebrafish differed significantly between 20-nm AgNPs and 80-nm AgNPs treatments (p < 0.05), indicating 20-nm AgNPs showing higher toxicity to zebrafish than the 80-nm AgNPs. Also, we noted that the used AgNPs induced sex-dependent effects on growth indices, oxidative/anti-oxidative status, neural signaling and hepatic lipid metabolism, with the male zebrafish being more sensitive to AgNPs than the females. Further, the tested AgNPs impaired the intestine much more seriously than the liver, as evidenced by the disruptions of Na/KATPase and antioxidant system in intestine but not in liver. These findings imply that prolonged exposure to AgNPs might induce size-related, sex-dependent, and organ-specific toxicity to adult zebrafish, thereby may significantly extend our understanding of the toxic effects of AgNPs in aquatic environment. (C) 2020 Elsevier Ltd. All rights reserved
Changes in taxonomic and functional diversity of fish communities after catastrophic habitat alteration caused by construction of Three Gorges Dam
No full textHabitat alterations that result from anthropogenic disturbance impact both the abiotic and biotic conditions of ecosystems, causing changes in biodiversity in many parts of the world. Recently, the use of functional diversity has been suggested as an approach to better evaluate the effects of such disturbance on particular communities. Here, we investigated the temporal changes in species and functional diversities of fish communities in the downstream area of the Three Gorges Dam (TGD) before, during, and after impoundment. We found two regime shifts in the fish community in 2004 and 2013 following impoundment. Although taxonomic diversity declined sharply at the first regime shift, it increased at the second shift. On the other hand, functional diversity declined throughout the same period, indicating the loss of functional diversity despite increased species diversity. Our analysis also showed that the fish communities shifted from under-dispersion to over-dispersion due to both a decrease in the relative abundance of migratory fish and an increase in the number of fish adapted to the new hydrologic conditions. Our results indicated that the impacts of dams on downstream fish communities may change over time. Interactions between species may become more important when the environment is stable
Opposite effects of the earthworm Eisenia fetida on the bioavailability of Zn in soils amended with ZnO and ZnS nanoparticles
No full textThe increasing release of metallic nanoparticles (NPs) or their sulfidized forms into soils have raised concerns about their potential risks to soil ecosystems. Hence, there is a need for novel strategies to remediate metallic NPs pollution in soils. In this study, to explore the feasibility of using earthworm Eisenia fetida to manage soils contaminated with metallic NPs, we simultaneously investigated the chronic soil toxicities of ZnO NPs and ZnS NPs to E. fetida, and the effects of E. fetida on Zn extractability in soils amended with ZnO NPs and ZnS NPs. After a 28 d exposure, survival rate and weight loss of earthworms were not impacted by either ZnO NPs or ZnS NPs at a concentration of 400 mg Zn per kg soil. Further, while ZnO NPs activated earthworm antioxidative system, ZnS NPs resulted in significant alleviation of oxidative damage in earthworm. The presence of earthworms significantly decreased the bioavailability of Zn in ZnO NPs contaminated soil, whereas significantly increased the bioavailability of Zn in ZnS NPs contaminated soil. These findings implied that the earthworm E. fetida could play an important role in altering the mobilization of metals originating from metallic NPs in soils, which may further aid in the development of a method for the treatment of metallic NPs pollution in soils. (C) 2020 Elsevier Ltd. All rights reserved