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Impatiens huangyanensis Jin and Ding 2002 is a plant species with very small populations, and it distributes only in Huangyan, Zhejiang Province, China. In this study, the complete chloroplast genome of I. huangyanensis was assembled by using high-throughput Illumina paired-end sequences. Its genomic feature was determined, and comparative genomic analysis of the genus Impatiens was performed. The results revealed that the full-length chloroplast genome of I. huangyanensis was 152,156 bp with a GC content of 36.8%. The chloroplast genome contains a typical quadripartite structure, comprising two copies of inverted repeats (IRs), a small single-copy (SSC) region, and a large single-copy (LSC) region. The sequence lengths of IR, SSC, and LSC were 25,756 bp, 17,662 bp, and 82,982 bp, respectively. The chloroplast genome consisted of 134 genes, including 84 protein-coding genes, 37 transfer RNA genes, eight ribosomal RNA genes, and five pseudogenes. Phylogenic results indicated I. huangyanensis shared a clade with I. davidii Franchet 1883, I. macrovexilla Chen 2000, I. fanjingshanica Chen 1999, and I. piufanensis Hook 1908, with a support rate of 100%. Our study provided insight into further studies on the conservation genetics of I. huangyanensis. [ABSTRACT FROM AUTHOR]

Secondary organic aerosol (SOA) produced by atmospheric oxidation of primary emitted precursors is a major contributor to fine particulate matter (PM2.5) air pollution worldwide. Observations during winter haze pollution episodes in urban China show that most of this SOA originates from fossil-fuel combustion but the chemical mechanisms involved are unclear. Here we report field observations in a Beijing winter haze event that reveal fast aqueousphase conversion of fossil-fuel primary organic aerosol (POA) to SOA at high relative humidity. Analyses of aerosol mass spectra and elemental ratios indicate that ring-breaking oxidation of POA aromatic species, leading to functionalization as carbonyls and carboxylic acids, may serve as the dominant mechanism for this SOA formation. A POA origin for SOA could explain why SOA has been decreasing over the 2013-2018 period in response to POA emission controls even as emissions of volatile organic compounds (VOCs) have remained flat. [ABSTRACT FROM AUTHOR]

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CH4 and CO2 fluxes from a high-cold swamp meadow and an alpine meadow on the Qinghai-Tibetan Plateau, subject to different degrees of degradation, were measured over a 12-month period. Air temperature, soil temperature and moisture, and the depths of the water table and thawing-freezing layer were determined. For swamp meadows, the greater the degradation, the lesser the carbon efflux. CH4 emissions at the nondegraded swamp meadow site were 1.09–3.5 and 2.5–11.27 times greater, and CO2 emissions 1.08–1.69 and 1.41–4.43 times greater, respectively, than those from moderately and severely degraded sites. For alpine meadows, the greater the degradation, the greater the CH4 consumption and CO2 emissions. CH4 consumption at the severely degraded alpine meadow site was 6.6–21 and 1.1–5.25 times greater, and CO2 emissions 1.05–78.5 and 1.04–6.28 times greater, respectively, than those from the nondegraded and moderately degraded sites. The CH4 and CO2 fluxes at both sites were significantly correlated ( R2 > 0.59, P < 0.05) with air temperature, soil temperature, and topsoil (0–5 cm depth) moisture, indicating these to be the main environmental factors affecting such fluxes. [ABSTRACT FROM AUTHOR]

Bacterial biodiversity is tightly correlated with ecological functions of natural systems, and bacterial rare and abundant subcommunities make distinct contributions to ecosystem functioning. However, the biogeographic pattern and elevational differentiation of sedimentary bacterial diversity have rarely been studied in cross-river systems at a continental scale. This study analyzed the biogeographic patterns and elevational differentiations of the entire, abundant, and rare bacterial (sub) communities as well as the underlying mechanisms across nine rivers that span distinct geographic regions and large elevational gradients in China. We found that bacterial rare and abundant subcommunities shared similar biogeographic patterns and both demonstrated strong distance-decay relationships, despite their distinct community compositions. However, both null model and variation partitioning analysis results showed that while environmental selection governed rare subcommunity assemblies (contribution: 51.9%), dispersal limitation (62.7%) controlled the assembly of abundant subcommunities. The disparity was associated with the broader threshold width of abundant taxa to water temperature and pH variations than rare taxa. Elevation-induced bacterial composition variations were more evident than latitudeinduced ones. Some specific operational taxonomic units (OTUs), representing 16.4% of the total sequences, much preferentially and even exclusively lived in high-elevation or low-elevation habitats and demonstrated some adaptations to local conditions. Greater positive: negative link ratios in bacterial co-occurrence networks of low elevations than high elevations (P < 0.05) partly resulted from their harboring higher organic carbon: nitrogen ratios. Together, this study draws a biogeographic picture of sedimentary bacterial communities in a continental-scale riverine system and highlights the importance of incorporating elevation-associated patterns of microbial diversity into riverine microbial ecology studies. [ABSTRACT FROM AUTHOR]

Cherry leaf spot (CLS), caused by Passalora circumscissa, is a fungal disease that can cause decreased fruit quality and yield via inconsistent ripening or premature defoliation. Germplasm resource screening is the most reliable approach to disease control for economically important crops. However, information is limited in China about the resistance of cherry cultivars to leaf spot caused by P. circumscissa. The aim of this study was to identify the resistance levels of cherry cultivars. Fifty-two cherry cultivars, including 40 Prunus avium, four Prunus pseudocerasus, and eight Prunus cerasus cultivars were collected for resistance level characterization. These specimens were then used to screen for P. circumscissa resistance through both detached leaf assays and natural field infection. Significant differences in the disease index (DI) value among test cultivars, ranging from 5.7 (resistant) to 53.7 (highly susceptible) and 6.5 (resistant) to 53.2 (highly susceptible), were observed under the controlled and field conditions respectively. Correlation coefficients between DI in pairs of years were highly significant (0.77-0.86). Although resistance rankings for cherry cultivars between screening methods were variable, the resistance levels of 52 cultivars evaluated under controlled and field condition were comparable with a correlation coefficient of 0.70 (P < 0.01). The results indicated that, across cherry cultivars, responses to CLS in the detached leaf assay corresponded well to responses under field conditions. A detached leaf assay was developed as a complementary method to facilitate the screening of cherry cultivars for resistance to leaf spot caused by P. circumscissa. Our study provides a theoretical basis for cherry disease resistance breeding and rational cultivar utilization. [ABSTRACT FROM AUTHOR]