Salinity is a major abiotic stress threatening crop production. Root-derived bacteria (RDB) are hypothesized to play a role in enhancing plant adaptability to various stresses. However, it is still ...unclear whether and how plants build up specific RDB when challenged by salinity. In this study, we measured the composition and variation in the rhizosphere and endophyte bacteria of salt-sensitive (SSs) and salt-resistant (SRs) plants under soil conditions with/without salinity. The salt-induced RDB (both rhizobiomes and endophytes) were isolated to examine their effects on the physiological responses of SSs and SRs to salinity challenge. Moreover, we examined whether functional redundancy exists among salt-induced RDB in enhancing plant adaptability to salt stress. We observed that although SSs and SRs recruited distinct RDB and relevant functions when challenged by salinity, salt-induced recruitment of specific RDB led to a consistent growth promotion in plants regardless of their salinity tolerance capacities. Plants employed a species-specific strategy to recruit beneficial soil bacteria in the rhizosphere rather than in the endosphere. Furthermore, we demonstrated that the consortium, but not individual members of the salt-induced RDB, provided enduring resistance against salt stress. This study confirms the critical role of salt-induced RDB in enhancing plant adaptability to salt stress.
► Antibiotics widely existed in the Baiyangdian Lake. ► Geographical differences of antibiotic levels were greatly due to human activities. ► Salvinia natans exhibited strongest bioaccumulation for ...quinolones. ► Algae and aquatic plants may be at risk of antibiotics in surface water.
This study investigated the presence and distribution of 22 antibiotics, including eight quinolones, nine sulfonamides and five macrolides, in the water, sediments, and biota samples from Baiyangdian Lake, China. A total of 132 samples were collected in 2008 and 2010, and laboratory analyses revealed that antibiotics were widely distributed in the lake. Sulfonamides were the dominant antibiotics in the water (0.86–1563ngL−1), while quinolones were prominent in sediments (65.5–1166μgkg−1) and aquatic plants (8.37–6532μgkg−1). Quinolones (17.8–167μgkg−1) and macrolides from below detection limit (BDL) to 182μgkg−1 were often found in aquatic animals and birds. Salvinia natans exhibited the highest bioaccumulation capability for quinolones among three species of aquatic plants. Geographical differences of antibiotic concentrations were greatly due to anthropogenic activities. Sewage discharged from Baoding City was likely the main source of antibiotics in the lake. Risk assessment of antibiotics on aquatic organisms suggested that algae and aquatic plants might be at risk in surface water, while animals were likely not at risk.
As a major group of plasticizers and flame-retardants, organophosphate esters (OPEs) have attracted particular attention due to their wide occurrence and potential impacts on human health and ...ecosystems. In the present study, the occurrence and distribution of 14 OPEs, including seven Alkyl-OPEs, three Cl-OPEs, and four Aryl-OPEs, were investigated in 65 road dust samples collected from November to December 2014 in Beijing, China. Cl-OPEs were the predominant compounds in the road dust samples, with the median concentration of 646 μg/kg, followed by the Alkyl-OPEs (median 135 μg/kg) and Aryl-OPEs (median 129 μg/kg). Tris(2-chloro-1-methylethyl) phosphate (TCPP) was the most abundant OPE with the median concentration of 384 μg/kg. In addition, OPEs levels showed significant difference (p < 0.05) in the spatial distribution. Markedly higher levels of OPEs were observed in 2nd and 3rd ring road with heavy traffic and high population density, indicating that the traffic and population were important factors for this distribution pattern. It was further supported by the analysis of OPEs in roadside soil and indoor dust in the vicinity of road dust sample sites. Finally, the average daily dose (ADD) for OPEs via inhalation, dermal absorption, and ingestion was calculated to evaluate the carcinogenic and non-carcinogenic risks to residents exposed to OPEs in the road dust. Risk assessment revealed that the risk originating from exposure to OPEs of road dust is currently low in Beijing, China.
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•OPEs are ubiquitous in road dust samples in Beijing, China.•Cl-OPEs were the predominant compounds in the road dust samples.•Traffic and population may be important factors for the distribution of OPEs.•The risks to residents exposed to OPEs in the road dust were assessed.
Excessive fertilization is a common agricultural practice that often negatively influence soil and environmental quality in intensive vegetable production systems in China. To reduce negative effects ...of excessive fertilization, current studies generally focused on fertilizer management but not irrigation. In this study, we investigated the effects of fertilization and irrigation on soil properties, leaching water characteristics, plant growth, cucumber yield, irrigation water use efficiency (IWUE) and partial factor productivity of nitrogen (PFPN) in a double cropping system. The treatments included (i) conventional irrigation with conventional N fertilization (IcNc), (ii) optimal irrigation with conventional N fertilization (IoNc), (iii) conventional irrigation with optimal N fertilization (IcNo), and (iv) optimal irrigation with optimal N fertilization (IoNo). In general, fertilization merely influenced concentrations of nitrate (NO3-), phosphorus (P) and potassium (K), but did not affect most leaching water characteristics. In contrast, irrigation influenced pH, EC and concentrations of P, K, Ca, Mg, Na and Cu. Cumulative leached amounts of NO3-, P, K, Ca, Mg, Na, Fe, Cu and Zn were significantly decreased by optimal irrigation as compared to conventional irrigation under same fertilization conditions, but not by optimal fertilization as compared to conventional fertilization under same irrigation conditions. The leachate volume was strongly positively correlated with cumulative leached amounts of all tested elements, and these relationships were obviously influenced by irrigation but not fertilization. The IoNo treatment significantly increased both IWUE and PFPN as compared to the IcNc treatment. However, the IcNo treatment only enhanced PFPN, while the IoNc treatment improved IWUE, when compared to the IcNc treatment. Our results suggested that irrigation has more influence than fertilization on leaching water quality and that the optimal irrigation combined with optimal fertilization was efficient in reducing the potential environmental risk caused by excessive fertilization in intensive vegetable production systems.
Solar greenhouse is a common facility type used for horticultural crop production in China. However, most solar greenhouse fields have been degraded due to continuous cropping and excessive ...fertilizer use. Therefore, we investigated solar greenhouse soils covering a wide range of cultivation years and environmental conditions in Round-Bohai Bay-Region to test the effects of cultivation year and biogeography on nutrients, heavy metals, and phthalate acid esters (PAEs). In general, soil pH decreased while soil electrical conductivity (EC), organic matter (OM), total nitrogen (TN), NO
3
−
-N, NH
4
+
-N, mineral nitrogen (MN), Olsen-P, and NH
4
OAc-K contents increased as time of cultivation increased. However, this trend was influenced by sampling sites. Among sampling sites, Jiangsu showed a relatively low soil pH and high Olsen-P content, while Hebei showed a relatively high soil EC value, NO
3
−
-N, NH
4
+
-N, MN, and NH
4
OAc-K contents. Liaoning was characterized by relatively high soil OM and TN contents. The nutrient level indexes in evaluation of soil quality on Olsen-P and NH
4
OAc-K exceeded the standard seriously. The maximum values of the heavy metals Cd, Cu, and Zn were 4.87, 2.78, and 1.15 times higher than the threshold values, respectively. There was a rising trend on the heavy metal contents with the increasing cultivation years, and this trend was significantly influenced by sampling sites. Both Cu and Zn had relative high heavy metal indexes in evaluation of soil pollution. The PAEs were not detected in almost all sampling soils. Overall, the excessive fertilizer application was an important cause of nutrient accumulation and heavy metal pollution, resulting in soil degradation in solar greenhouses.
•Blue light exhibited more effective in maintaining chloroplast ultrastructure than red light.•Blue light induced higher photosynthetic capacity than red light.•Red light led to larger increase in ...nutrient accumulation than blue light.
Plant growth and physiology are strongly influenced by blue and red lights. When exposed to prolonged red light, leaf photosynthesis is severely impaired. This ‘red light syndrome’ has been characterized by a low maximum quantum yield of chlorophyll fluorescence (Fv/Fm), a low photosynthetic capacity (Amax) and unresponsive stomatal conductance (gs). When adding blue light to red light, none of these effects occurrs. Previous studies mainly focused on photosynthetic changes, however, little information is available on how blue light alleviates ‘red light syndrome’ through comprehensively regulating photosynthesis in leaves, nutrient uptake by roots and their correlation. Four light quality treatments including white light (W), red monochromatic light (R), blue monochromatic light (B), and a combination of red and blue light (RB) were employed to investigate their effects on chloroplast ultrastructure, photosynthesis and nutrient accumulation in cucumber seedlings. The results showed that compared to W, R treatment significantly decreased RGR, Pn, Fv/Fm and ΦII, numbers and size of chloroplast and starch grain, thickness of grana and largely increased accumulation of P, K, Mn and Zn, indicating that R treatment severely decelerated plant growth, disrupted chloroplast ultrastructure, limited photosynthetic characteristics, and accumulated excess nutrients. However, these suppressions were effectively alleviated by adding blue light to red light (compare RB versus R). The B treatment plants exhibited plant growth, chloroplast ultrastructural and photosynthetic characteristics similar to those of W. It is clearly demonstrated that blue light-dependent alleviation of 'red light syndrome' is accompanied by mediating the enhancement of chloroplast ultrastructure, photosynthetic traits, and removal of red light-induced excessive nutrient accumulation in cucumber plant. We hypothesize that changes in both chloroplast ultrastructure and nutrient accumulation could mediate the alleviation.
► A comprehensive study on the occurrence of antibiotics in eight STPs of Beijing. ► The antibiotics in STPs of Beijing are not eliminated completely. ► The antibiotics levels in sludge were higher ...in winter than other seasons. ► Total fluoroquinolones levels were lower than the PNEC for microorganisms.
The occurrence, removal efficiency and seasonal variation of 22 antibiotics, including eight fluoroquinolones, nine sulfonamides and five macrolides, were investigated in eight sewage treatment plants (STPs) in Beijing, China. A total of 14 antibiotics were detected in wastewater samples, with the maximum concentration being 3.1
μg
L
−1 in the influent samples and 1.2
μg
L
−1 in the effluent samples. The most frequently detected antibiotics were ofloxacin, norfloxacin, sulfadiazine, sulfamethoxazole, erythromycin and roxithromycin; of these, the concentration of ofloxacin was the highest in most of the influent and effluent samples. Eighteen antibiotics were detected in the sludge samples, with concentrations ranging from 1.0
×
10
−1 to 2.1
×
10
4
μg
kg
−1. The dominant antibiotics found in the sludge samples were the fluoroquinolones, with ofloxacin having the highest concentration in all the sludge samples. The antibiotics could not be removed completely by the STPs, and the mean removal efficiency ranged from −34 to 72%. Of all the antibiotics, the fluoroquinolones were removed comparatively more efficiently, probably due to their adsorption to sludge. Seasonal variation of the antibiotics in the sludge samples was also studied. The concentrations of antibiotics in winter were higher than in spring and autumn. Since the total levels of the fluoroquinolones detected in the influent samples were lower than the predicted no-effect concentration (PNEC) of 8.0
μg
L
−1, the residues of these antibiotics would be unlikely to have adverse effects on microorganisms involved in sewage treatment processes.
Rhizosphere microorganisms in soils are important for plant growth. However, the importance of rhizosphere microorganisms is still underestimated since many microorganisms associated with plant roots ...cannot be cultured and since the microbial diversity in the rhizosphere can be influenced by several factors, such as the cropping history, biogeography, and agricultural practice. Here, we characterized the rhizosphere bacterial diversity of cucumber plants grown in soils covering a wide range of cucumber cropping histories and environmental conditions by using pyrosequencing of bacterial 16S rRNA genes. We also tested the effects of compost addition and/or bacterial inoculation on the bacterial diversity in the rhizosphere. We identified an average of approximately 8,883 reads per sample, corresponding to around 4,993 molecular operational taxonomic units per sample. The Proteobacteria was the most abundant phylum in almost all soils. The abundances of the phyla Bacteroidetes, Actinobacteria, Firmicutes, Acidobacteria, and Verrucomicrobia varied among the samples, and together with Proteobacteria, these phyla were the six most abundant phyla in almost all analyzed samples. Analyzing all the sample libraries together, the predominant genera found were Flavobacterium, Ohtaekwangia, Opitutus, Gp6, Steroidobacter, and Acidovorax. Overall, compost and microbial amendments increased shoot biomass when compared to untreated soils. However, compost addition decreased the bacterial α-diversity in most soils (but for three soils compost increased diversity), and no statistical effect of microbial amendment on the bacterial α-diversity was found. Moreover, soil amendments did not significantly influence the bacterial β-diversity. Soil organic content appeared more important than compost and microbial amendments in shaping the structure of bacterial communities in the rhizosphere of cucumber.
Paraquat is a quaternary ammonium herbicide, which can be distributed in lung, liver, kidney, heart, brain and other organs through blood circulation, leading to multiple organ failure, especially ...lung injury. Due to the lack of effective treatment methods and specific antidotes, the prognosis of most patients with paraquat poisoning is very poor. The treatment of paraquat poisoning was a big problem for emergency doctors. Previous studies have found that pulmonary fibrosis caused by paraquat poisoning is closely related to a variety of pathological processes, such as oxidative stress, inflammatory reaction, mitochondrial damage, imbalance of extracellular matrixproduction (ECM) and degradation, which involve the activation or inhibition of various signaling pathways. In recent years, many researchers focused on clarifying the mechanism of paraquat induced pulmonary fibrosis, and some signaling pathways related to paraquat poisoning leading to pulmonary fibrosis have been found. A large number of studies have
•Gene co-expression networks during graft formation are stage-specific.•The asymmetric response phase (3−72 hours after grafting) is the critical period for graft formation.•Auxin and cytokinin ...respond to grafting, above and below the graft junction, respectively, to promote the graft formation.•The accumulation of auxin above the graft junction prepares cells for mitosis, which promotes cell division to form callus.•Exogenous application of certain concentrations of IAA and 6-BA will promote graft formation.
Grafting is widely used worldwide because of its obvious advantages, especially in solanaceous vegetable crops. However, the molecular mechanisms underlying graft formation are unknown. In this study, internode tissues from above and below the graft junction were harvested, and we performed weighted gene co-expression network analysis (WGCNA) to describe the temporal and spatial transcriptional dynamics that occur during graft formation in tomato. The wounding stress response involved in JA, ETH, and oxylipins mainly occurred at 1 h after grafting (HAG). From 3 to 12 HAG, the biological processes of snRNA and snoRNA modification and the gibberellin-mediated signaling pathway functioned both above and below the graft junction. However, auxin transport and signaling, DNA replication, and xylem and phloem pattern formation were restricted to the scion, whereas the cytokinin-activated signaling pathway and the cellular response to sucrose starvation was restricted to the rootstock. At 24−72 HAG, cell division occurred above the graft junction, and photosynthesis-related pathways were activated below the graft junction. The levels of auxin and cytokinin reached their maxima above and below the graft junction at 12 HAG, respectively. Exogenous application of certain concentrations of IAA and 6-BA will promote xylem and phloem transport capacity. The current work has analyzed the stage-specific events and hub genes during the developmental progression of tomato grafting. We found that auxin and cytokinin levels respond to grafting, above and below the graft junction, respectively, to promote the formation of xylem and phloem patterning. In addition, the accumulation of auxin above the graft junction induced cells to prepare for mitosis and promoted the formation of callus. In short, our work provides an important reference for theoretical research and production application of tomato grafting in the future.
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