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Microplastics can be colonized by microorganisms and form plastisphere. However, knowledge of bacterial community succession and the enrichment of antibiotic resistance genes (ARGs) and pathogens on microplastics in aquaculture environments is limited. Here, we conducted a 30-day continuous exposure experiment at an oyster farm. Results showed that the alpha-diversity of communities on most microplastics continuously increased and was higher than in planktonic communities after 14 days. Microplastics could selectively enrich certain bacteria from water which can live a sessile lifestyle and promote colonization by other bacteria. The composition and function of plastisphere communities were distinct from those in the surrounding water and influenced by polymer type and exposure time. Microplastics can enrich ARGs (sul 1, qnr S and bla TEM) and harbor potential pathogens (e.g., Pseudomonas aeruginosa). Therefore, microplastic pollution may pose a critical threat to aquaculture ecosystems and human health. Our study provides further insight into the ecological risks of microplastics. [Display omitted] • Bacterial communities on MPs are significantly different from those in water. • Bacterial communities on MPs are influenced by polymer type and exposure time. • Some biomarker genera selectively enriched on their preferred polymer types. • MPs can enrich ARGs and harbor some pathogens in the oyster farming environment. [ABSTRACT FROM AUTHOR]

Abstract: 5-Ethylidene-2-norbornene (ENB) polymerization and copolymerization with ethylene (E) catalyzed by constrained geometry catalyst 2-tetramethylcyclopentadienyl-4,6-di-tert-butylphenoxytitanium dichloride (1) were studied in the presence of Al i Bu3 and Ph3CB(C6F5)4 (TIBA/B). The catalyst system shows moderate activity on the homopolymerization of ENB, and higher activity on the copolymerization of E/ENB under atmospheric pressure of ethylene. 1H NMR analysis indicates that ENB was regioselectively incorporated into the copolymer backbone through the endocyclic double bond, leaving the ethylidene double bond unreacted. The ethylidene group contained in the poly(E-co-ENB) was quantitatively converted to the epoxy group with m-chloroperbenzoic acid, producing functionalized poly(E-co-ENB)s. The parent and functionalized copolymers have been characterized using IR, NMR, DSC, and GPC techniques. [Copyright &y& Elsevier]

The practice of straw retention often causes seedling issues, including slow seedling establishment and weak seedling. Irrigation shortly after sowing (namely ‘sowing irrigation’, abbreviated as SI) may help to accelerate the seedling establishment under straw retention, and appropriate split nitrogen (SN) management may further boost crop growth and grain yield. Here, we conducted a 2-year field trial to assess the impacts of SI and SN on crop growth, grain yield and water and nitrogen use efficiencies of a maize hybrid i.e. Zhengdan 958 grown under straw retention. The treatments consisted of two irrigation conditions and three splitting nitrogen regimes, with three replications. SI treatment was composed of 0 mm irrigation (denoted as W0) and 60 mm irrigation (denoted as W1) shortly after sowing. SN management contained a similar total nitrogen rate (300 kg ha −1 ) but was split in three proportions between sowing and big flare stage, i.e. 10:0 (denoted as N1), 5:5 (denoted as N2) and 3:7 (denoted as N3). Our results indicated that sowing irrigation accelerated seedling emergence by 2–7 days, and increased grain yield by 4.73% (2014) and 5.90% (2015), and water use efficiency by 1.69% (2014) and 3.80% (2015) compared to the treatment without sowing irrigation. N2 and N3 treatments increased grain yield by 9.00–10.12% via greater kernel number, and increased nitrogen partial factor productivity by 9.35–10.20% in both years. The improved grain yield by sowing irrigation or splitting nitrogen was due to greater canopy photosynthetic capacity with higher leaf area index, leaf chlorophyll content and net photosynthesis rate. It was found that the optimal ratio of basal: topdressing nitrogen depended on whether sowing irrigation was used. Without sowing irrigation, W0N2 produced the highest grain yield; while with irrigation, both W1N2 and W1N3 produced a greater production than W1N1. In conclusion, the combination of sowing irrigation and splitting nitrogen to the big flare stage could increase not only maize grain yield, but also resource-use efficiency under straw retention in lime concretion black soil of Huaibei Plain, Anhui Province, China. [ABSTRACT FROM AUTHOR]

Burley tobacco ( Nicotiana tabacum L.) is an important raw material in the production of Chinese-style blended cigarettes. However, the high levels of tobacco-specific nitrosamines (TSNA) have devalued the industrial use of burley tobacco and limited its sustainable use. The objective of this paper was to investigate the effects of acetylsalicylic acid (ASA) application on accumulation of TSNA, its precursors and quality of air-cured burley tobacco ( Nicotiana tabacum L. cv. DaBai 1). Field experiments were conducted to determine the contents of TSNA and the precursors and the sensory quality of burley tobacco under 0, 0.1, 0.3 mM of ASA in 2014 and 2015 at Dazhou, Sichuan Province, China. The results showed that TSNA, nitrate, nitrite and alkaloids levels were significantly reduced by the application of ASA, of which the total TSNA were significantly lower by 10.40–24.75%, and two of the strong animal carcinogens in tobacco products, i.e. N -nitrosonornicotine (NNN) and 4-(methylnitrosamino) -1- (3- pyridyl) -1- butanone (NNK) were reduced by 9.01–24.23% and 11.43–26.86%, respectively. Year had significant effects on TSNA and the TSNA contents in 2014 were higher than in 2015. Interestingly, the sensory quality of burley tobacco remained or was even better after application of ASA. In conclusion, this study revealed that ASA application was able to reduce the levels of TSNA and its precursors in sustaining burley tobacco industry potentially. [ABSTRACT FROM AUTHOR]

Abstract: To gain a physiological understanding of the effects of high temperatures on cucumber (Cucumis sativus L.), we subjected seedlings to heat treatment at daytime temperatures of 28°C, 32°C, and 36°C for 7h a day for 30 days. The amount of active oxygen species, indicators of senescence, and photosynthetic properties in the second and third leaves were determined at the start of temperature treatment and on the 15th and 30th days of treatment. The amount of active oxygen species superoxide in leaves was greatest in the high temperature zones on the 15th day of treatment, and the amount of hydrogen peroxide was greatest in the high temperature zones on both the 15th and 30th days of treatment. The reduction in the amount of protein and the increase in the amount of malondialdehyde, both indicators of senescence, were greatest in the high temperature zones on both the 15th and 30th days of treatment, and the amount of chlorophyll was lowest in the 36°C zone on the 15th day, and lower in the high temperature zones on the 30th day. It is clear from these results that a large amount of active oxygen species is generated and accumulated in the leaves at high temperatures, and senescence is significantly accelerated. The photosynthetic properties of stomatal conductance, sub-stomatal CO2 concentration, and transpiration rate were at the same level on both the 15th and 30th days of treatment in all three temperature treatment zones. No significant difference was seen in the net photosynthesis rate between the 28°C and 32°C zones, was lower in the 36°C zone than the 32°C zone on the 15th day, and lowest in the 36°C zone on the 30th day. CO2 intake and water absorption are only mildly affected by high temperatures, and the reduction in net photosynthesis rate due to the 36°C high temperature stress suggests that the large amount of active oxygen species induces inhibition of photosynthesis and damage to the mechanism of photosynthesis. [Copyright &y& Elsevier]

Abstract: A comparative analysis of electronic structure and stability of endohedral metallofullerenes TM@C24 and TM@C24H12 (TM=Ti, Zr and Hf) is systematically performed with the aid of quantum chemical DFT-B3PW91 approach. Our calculated results show that TM@C24H12 display higher symmetry compared with TM@C24, and all of endohedral metallofullerenes are in a singlet spin state. Thermodynamic data reflect that endohedral metallofullerenes TM@C24 are more stable than TM@C24H12 and the Ti atom is energetically favorable to be encapsulated. However, these TM@C24H12 have higher kinetic stability. The analyses of the vertical electron affinities (VEAs) and vertical ionization potentials (VIPs) indicate the possibilities of accepting electrons of TM@C24H12 become weaker and the possibilities of denoting electrons become stronger. Additionally, natural population analysis presents that the natural charge on TM atoms dramatically increases along with increasing atomic number, and the 5d orbitals of Zr atom and 6d orbitals of Hf atom are significantly involved in their chemical bonding. [Copyright &y& Elsevier]