Mesomorphism Modulation of Perfluorinated Janus Triphenylenes by Inhomogeneous Chain Substitution Patterns.

Two isomeric series of compounds with "inverted" chains' substitution patterns, 7,10-dialkoxy-1,2,3,4-tetrafluoro-6,11-dimethoxytriphenylene and 6,11-dialkoxy-1,2,3,4-tetrafluoro-7,10-dimethoxytriphenylene, labelled respectively p-TPFn and m-TPFn, and two non-fluorinated homologous isomers, 3,6-dibutoxy-2,7-dimethoxytriphenylene and 2,7-dibutoxy-3,6-dimethoxytriphenylene, p-TP4 and m-TP4, respectively, were synthesized in three steps and obtained in good yields by the efficient transition-metal-free, fluoroarene nucleophilic substitution via the reaction of appropriate 2,2'-dilithium biphenylenes with either perfluorobenzene, C6 F6 , to yield p-TPFn and m-TPFn, or o-difluorobenzene, C6 H4 F2 , for p-TP4 and m-TP4, respectively. The single-crystal structures of p-TPF4, m-TPF4 and p-TP4, unequivocally confirmed that the cyclization reactions occurred at the expected positions, and that the fluorinated molecules stack up into columns with short separation, a propitious situation for the emergence of columnar mesophases. The mesomorphous properties were found to be greatly affected by both chains' length and positional isomerism: a Colhex phase is found for p-TPF4 and m-TPF4, but mesomorphism vanishes in p-TPF6, and changes for the isomeric homologs m-TPFn, with the induction for n≥6 of a lamello-columnar phase, LamColrec . As expected, both non-fluorinated compounds are deprived of mesomorphism. These compounds emit blue-violet colour in solution, independently of the chains' substitution pattern, and the absolute fluorescence quantum yields can reach up to 46 %. In thin films, fluorescence is slightly redshifted.

Xylem formation of Populus euphratica and its response to water-heat factors in the lower reaches of Tarim River, China.

To deeply understand the effects of water and temperature factors on the xylem formation of Populus euphratica, taking the Yingsu section in the lower reaches of Tarim River as an example, we selected micro-coring samples of P. euphratica around monitoring wells F2 and F10 in the 100 and 1500 m distance from the channel of Tarim River. We used wood anatomy method to analyze the xylem anatomy of P. euphratica and its response to water and temperature factors. The results showed that the changes of the total anatomical vessel area and the vessel number of P. euphratica in the two plots were basically consistent during the whole growing season. The vessel number of xylem conduits of P. euphratica increased slowly with the increases of groundwater depth, while the total conduit area increased firstly and then decreased. The total vessel area, minimum vessel area, average vessel area, and maximum vessel area of P. euphratica xylem increased significantly with the increases of temperature in the growing season. The contribution of groundwater depth and air temperature to P. euphratica xylem varied among different growth stages. In the early growing season, air temperature had the largest contribution to the number and total area of xylem conduits of P. euphratica. During the middle growing season, air temperature and groundwater depth jointly affected the parameters of each conduit. During the later growing season, groundwater depth had the largest contribution to the number and total area of conduits. Results of the sensitivity analysis indicated that the groundwater depth sensitive to xylem vessel number change of P. euphratica was 5.2 m and that to the change in the total conduit area was 5.9 m. The temperature sensitive to total vessel area of P. euphratica xylem was 22.0 ℃, and that to average vessel area was 18.5 ℃. Therefore, the sensitive groundwater depth affecting xylem growth was at the range of 5.2-5.9 m, and the sensitive temperature was at the range of 18.5-22 ℃. This study could provide scientific basis for the restoration and protection of P. euphratica forest in the lower reaches of Tarim River.

The incidence of vasovagal reactions during earlobe piercing.

Background: Vasovagal reactions are common amongst patients with a fear of needles receiving injections or during venipuncture, but they are rarely studied in healthy people undergoing earlobe piercing. The purpose of this prospective study was to evaluate the incidence and the features of vasovagal reactions observed during earlobe piercing. Methods: Thousand eight hundred and sixty six participants aged older than 13 years had their earlobes pierced in our department from January 2020 to January 2022. When vasovagal reactions occurred during the procedure (e.g., dizziness, pallor, diaphoresis, and faintness, etc.), they were recorded and more detailed demographic information was collected. Results: A total of 196 cases of vasovagal reactions were reported in females amongst 1,866 participants, including 58 who actually lost consciousness during earlobe piercing. The incidence of vasovagal reactions and vasovagal syncope was 10.5 and 3.11% respectively. All syncopal reactions occurred in persons younger than 30 years. Conclusion: Vasovagal syncope is often very sudden and occurs without warning. Practitioners need to be familiar with these reactions, and prevent people from an unpredictable fall and subsequent injury during ear piercing.

Functional identification of the different regions in B-class floral homeotic MADS-box proteins IiAP3 and IiPI from Isatis indigotica.

APETALA3 (AP3) and PISTILLATA (PI) are B-class MADS-box floral homeotic genes of Arabidopsis and are involved in specifying the identity of petals and stamens. In the present work, IiAP3 and IiPI, the respective orthologous genes of AP3 and PI, were cloned from Isatis indigotica. By expressing in ap3-6 and pi-1 homozygous mutant and in wild-type Arabidopsis under the control of AP3 promoter or CaMV 35S promoter, we demonstrated that IiAP3 and IiPI were functionally equivalent to AP3 and PI of Arabidopsis. Referring to previous reports and the research results in the present work, expression patterns of AP3 and PI homologs are not the same in different angiosperms possessing diverse floral structures. It suggests that the alterations in expression may contribute to the changing morphology of flowers. To further determine the relationship between IiAP3 and IiPI, the coding sequences of the different structural regions in these two proteins were swapped with each other, and the data collected from transgenic Arabidopsis plants of the chimeric constructs suggested that MADS domain was irreplaceable for the function of IiAP3, K domain of IiAP3 was involved in specifying the identity of stamens, K domain of IiPI was mainly related to the formation of petals, and C-terminal region of IiPI was involved in characterization of stamens. In addition, a complete KC region of these two proteins was more effective in phenotypic complementation of the mutants.

SEPALLATA--like genes of Isatis indigotica can affect the architecture of the inflorescences and the development of the floral organs.

BACKGROUND: The architecture of inflorescence and the development of floral organs can influence the yield of seeds and have a significant impact on plant propagation. E-class floral homeotic MADS-box genes exhibit important roles in regulation of floral transition and differentiation of floral organs. Woad (Isatis indigotica) possesses unique inflorescence, floral organs and fruit. However, very little research has been carried out to determine the function of MADS-box genes in this medicinal cruciferous plant species. RESULTS: SEPALLATA orthologs in I. indigotica were cloned by degenerate PCR. The sequence possessing the highest identity with SEP2 and SEP4 of Arabidopsis were named as IiSEP2 and IiSEP4, respectively. Constitutive expression of IiSEP2 in Columbia (Col-0) ecotype of Arabidopsis led to early flowering, and the number of the flowers and the lateral branches was reduced, indicating an alteration in architecture of the inflorescences. Moreover, the number of the floral organs was declined, the sepals were turned into carpelloid tissues bearing stigmatic papillae and ovules, and secondary flower could be produced in apetalous terminal flowers. In 35S::IiSEP4-GFP transgenic Arabidopsis plants in Landsberg erecta (Ler) genetic background, the number of the floral organs was decreased, sepals were converted into curly carpelloid structures, accompanied by generation of ovules. Simultaneously, the size of petals, stamens and siliques was diminished. In 35S::IiSEP4-GFP transgenic plants of apetalous ap1 cal double mutant in Ler genetic background, the cauliflower phenotype was attenuated significantly, and the petal formation could be rescued. Occasionally, chimeric organs composed of petaloid and sepaloid tissues, or petaloid and stamineous tissues, were produced in IiSEP4 transgenic plants of apl cal double mutant. It suggested that overexpression of IiSEP4 could restore the capacity in petal differentiation. Silencing of IiSEP4 by Virus-Induced Gene Silencing (VIGS) can delay the flowering time, and reduce the number and size of the floral organs in woad flowers. CONCLUSION: All the results showed that SEPALLATA-like genes could influence the architecture of the inflorescence and the determinacy of the floral meristems, and was also related to development of the floral organs.

Organ-specific cholesterol metabolic aberration fuels liver metastasis of colorectal cancer.

Rationale: Metastasis, the development of secondary malignant growth at a distance from a primary tumor, is the main cause of cancer-associated death. However, little is known about how metastatic cancer cells adapt to and colonize in the new organ environment. Here we sought to investigate the functional mechanism of cholesterol metabolic aberration in colorectal carcinoma (CRC) liver metastasis. Methods: The expression of cholesterol metabolism-related genes in primary colorectal tumors (PT) and paired liver metastases (LM) were examined by RT-PCR. The role of SREBP2-dependent cholesterol biosynthesis pathway in cell growth and CRC liver metastasis were determined by SREBP2 silencing in CRC cell lines and experimental metastasis models including, intra-splenic injection models and liver orthotropic injection model. Growth factors treatment and co-culture experiment were performed to reveal the mechanism underlying the up-regulation of SREBP2 in CRC liver metastases. The in vivo efficacy of inhibition of cholesterol biosynthesis pathway by betulin or simvastatin were evaluated in experimental metastasis models. Results: In the present study, we identify a colorectal cancer (CRC) liver metastasis-specific cholesterol metabolic pathway involving the activation of SREBP2-dependent cholesterol biosynthesis, which is required for the colonization and growth of metastatic CRC cells in the liver. Inhibiting this cholesterol biosynthesis pathway suppresses CRC liver metastasis. Mechanically, hepatocyte growth factor (HGF) from liver environment activates SREBP2-dependent cholesterol biosynthesis pathway by activating c-Met/PI3K/AKT/mTOR axis in CRC cells. Conclusion: Our findings support the notion that CRC liver metastases show a specific cholesterol metabolic aberration. Targeting this cholesterol biosynthesis pathway could be a promising treatment for CRC liver metastasis.

Tobacco NtabSPL6-2 can enhance local and systemic resistances of Arabidopsis thaliana to bacterial and fungal pathogens.

NtabSPL6-2 of Nicotiana tabacum was introduced into Arabidopsis by Agrobacterium-mediated floral-dip method. Compared to wild-type Col-0 plants, the arrangement of cauline leaves in NtabSPL6-2 transgenic plants was converted into opposite from simple and alternate, and the margin of rosette leaves was serrated. NtabSPL6-2 transgenic plants possessed a significantly greater fresh weight. Subcellular localization by fusion with GFP confirmed that the encoded product of NtabSPL6-2 existed in the nucleus. The leaves of NtabSPL6-2 transgenic plants exhibited an enhanced capacity to restrain the bacterial reproduction after infection by Pseudomonas syringae, accompanied by higher expression of the pathogenesis-related gene PR1 in the infiltrated leaves, indicating NtabSPL6-2 could improve the defense response of Arabidopsis to P. syringae at the local sites. Similarly, it was confirmed that NtabSPL6-2 could enhance the systemic acquired resistance of Arabidopsis in response to P. syringae. In addition, the area of necrotic plaque appearing on the transgenic leaves inoculated with Botrytis cinerea was smaller and accompanied by an upregulation of PR1 and PR5, indicating NtabSPL6-2 transgenic leaves were less susceptible to the fungal pathogen. Moreover, there was less accumulation of reactive oxygen species (H2O2 and O2-) and malondialdehyde in the local infected sites of transgenic plants, whereas the wild-type Col-0 plants were more oxidatively injured after infestation by B. cinerea.

Author Correction: AZD9291 inactivates the PRC2 complex to mediate tumor growth inhibition.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Herbivore-induced rice resistance against rice blast mediated by salicylic acid.

In agro-ecosystems, plants are important mediators of interactions between their associated herbivorous insects and microbes, and any change in plants induced by one species may lead to cascading effects on interactions with other species. Often, such effects are regulated by phytohormones such as jasmonic acid (JA) and salicylic acid (SA). Here, we investigated the tripartite interactions among rice plants, three insect herbivores (Chilo suppressalis, Cnaphalocrocis medinalis or Nilaparvata lugens), and the causal agent of rice blast disease, the fungus Magnaporthe oryzae. We found that pre-infestation of rice by C. suppressalis or N. lugens but not by C. medinalis conferred resistance to M. oryzae. For C. suppressalis and N. lugens, insect infestation without fungal inoculation induced the accumulation of both JA and SA in rice leaves. In contrast, infestation by C. medinalis increased JA levels but reduced SA levels. The exogenous application of SA but not of JA conferred resistance against M. oryzae. These results suggest that pre-infestation by C. suppressalis or N. lugens conferred resistance against M. oryzae by increasing SA accumulation. These findings enhance our understanding of the interactions among rice plant, insects and pathogens, and provide valuable information for developing an ecologically sound strategy for controlling rice blast.

Resveratrol Reverses Retinoic Acid Resistance of Anaplastic Thyroid Cancer Cells via Demethylating CRABP2 Gene.

Background: Cellular retinoic acid binding protein 2 (CRABP2) mediates retinoic acid/RA anti-cancer pathways. Resveratrol effectively reverses RA tolerance and upregulates CRABP2 expression of anaplastic thyroid cancer cell line THJ-11T. As DNA methylation is responsible for CRABP2 silencing, the CRABP2 methylation status of THJ-11T cells and the demethylating effect of resveratrol on this gene are elucidated. Materials and methods: The statuses of CRABP2 expression and methylation and the levels of DNA methyltransferases (DNMTs) DNMT1, DNMT3A, and DNMT3B of THJ-11T cells were examined before and after resveratrol treatment via multiple experimental methods. The human medulloblastoma UW228-2 cell line was cited as the control of CRABP2 methylation and gemcitabine as the demethylator control. Results: RT-PCR, immunocytochemical staining and Western blotting showed that resveratrol significantly increased the CRABP2 expression and RA sensitivity of THJ-11T and UW228-2 cells. Bisulfite sequencing showed five CpG methylation sites at the CRABP2 promoter region of both cell lines, which were partially (3/5) demethylated by resveratrol and totally (5/5) by gemcitabine. DNMT1, DNMT3A, and DNMT3B were reduced in UW228-2 cells and DNMT1 and DNMT3A were reduced in THJ-11T cells after resveratrol treatment in a time-related fashion. Conclusion: Resveratrol is able to erase CRABP2 methylation and can thereby increase the RA sensitivity of THJ-11T and UW228-2 cells. This study demonstrates the additional value of the natural polyphenolic compound resveratrol as a demethylator in cancer treatments.

[Modified tunnel technique applied in the treatment of gingival recessions with non-carious cervical lesion].

OBJECTIVE: This study aimed to investigate the clinical effect of modified tunnel technique (MTUN) in the treatment of gingival recession with non-carious cervical lesion (NCCL). METHODS: Forty-two teeth with Miller I degree gingival recession were divided into the NCCL group or control group depending on whether NCCL was present. Both groups were treated with MTUN plus subepithelial connective tissue. The periodontal probing depth (PD), gingival recession height (GRH), gingival recession width (GRW), attached gingival width (AGW), and clinical attachment loss (CAL) were recorded before and at 3 and 6 months after operation. The mean root coverage (MRC) at 6 months after operation was calculated and analyzed. A root coverage esthetic scoring system was used to record aesthetic scores. RESULTS: GRH, GRW, and CAL of the two groups after surgery were significantly lower than those before surgery, and no significant changes in PD and AGW were observed. The MRC in the NCCL group was 63.40%±28.02%, whereas that in the control group was 67.00%±21.72%; no significant difference between the two groups was found. In terms of aesthetic outcomes, no significant difference between groups was reported. CONCLUSIONS: MTUN can effectively improve gingival recession, and the presence of shallow NCCL (≤1 mm) will not affect the surgical effect of MTUN.

Synthesis of Graphene Oxide Modified Magnetic Chitosan Having Skin-Like Morphology for Methylene Blue Adsorption.

In this work, a novel magnetic biomass adsorbent was synthesized by a simple method. The adsorbent prepared from chitosan, graphene oxide and CoFe2O4 with a 'skin-like' morphology had a strong adsorption capacity for methylene blue adsorption and was easily separated from the liquid. The synthesized samples were characterized by scanning electron microscope, energy dispersive spectroscopy, fourier transform infrared spectroscopy and X-ray diffractomer. The adsorption capacity of the adsorbent was evaluated. The various factors affecting the adsorption performance were explored. Meanwhile, the adsorption process was simulated by five kinetic models and four isotherm models. The adsorption process was well described by the Pseudo-second-order kinetic model and the Freundlich isotherm model. ΔG < 0, ΔH < 0 and ΔS < 0 indicate that the adsorption process was a spontaneous, exothermic and randomness decrease process. The adsorbents loaded with methylene blue could be desorbed by soaking in dilute hydrochloric acid. The adsorption-desorption cycle experimental results showed that the adsorbent had good reusability performance.

AZD9291 inactivates the PRC2 complex to mediate tumor growth inhibition.

Deregulated Polycomb repressive complex 2 (PRC2) is intimately involved in tumorigenesis and progression, making it an invaluable target for epigenetic cancer therapy. Disrupting the EZH2-EED interaction, which is required for PRC2 enzymatic activity, is a promising strategy for cancer treatment. However, this kind of inhibitors are still limited. The in-cell protein-protein interaction screening was conducted for approximately 1300 compounds by NanoBRET technology. Co-immunoprecipitation (Co-IP), protein thermal shift assay (PTSA), and cellular thermal shift assay (CETSA) were performed to investigate the regulation of PRC2 by AZD9291. The anti-tumor effects of AZD9291 on breast cancer (BC) cells and diffuse large B-cell lymphoma (DLBCL) cells were detected. MicroRNA array assay, luciferase reporter assay, and qRT-PCR were conducted to identify the interaction and regulation among AZD9291, EZH2, and miR-34a. We discovered that, AZD9291, a potent and selective EGFR inhibitor, disrupted the interaction of EZH2-EED, leading to impairment of PRC2 activity and downregulation of EZH2 protein. In addition, AZD9291 declined EZH2 mRNA expression via upregulating the expression of a tumor suppressor, miR-34a. Our results suggest that AZD9291 can serve as a lead compound for further development of antagonist of PRC2 protein-protein interactions and EZH2 mRNA may be a direct target of miR-34a through non-canonical base pairing.

ACOT12-Dependent Alteration of Acetyl-CoA Drives Hepatocellular Carcinoma Metastasis by Epigenetic Induction of Epithelial-Mesenchymal Transition.

Metabolic reprogramming plays an important role in supporting tumor growth. However, little is known about the metabolic alterations that promote cancer metastasis. In this study, we identify acyl-CoA thioesterase 12 (ACOT12) as a key player in hepatocellular carcinoma (HCC) metastasis. The expression of ACOT12 is significantly down-regulated in HCC tissues and is closely associated with HCC metastasis and poor survival of HCC patients. Gain- and loss-of-function studies demonstrate that ACOT12 suppresses HCC metastasis both in vitro and in vivo. Further mechanistic studies reveal that ACOT12 regulates the cellular acetyl-CoA levels and histone acetylation in HCC cells and that down-regulation of ACOT12 promotes HCC metastasis by epigenetically inducing TWIST2 expression and the promotion of epithelial-mesenchymal transition. Taken together, our findings link the alteration of acetyl-CoA with HCC metastasis and imply that ACOT12 could be a prognostic marker and a potential therapeutic target for combating HCC metastasis.

Older adults show less interference from task-irrelevant social categories: evidence from the garner paradigm.

Though age-related difference in most cognitive performance has been found, there was no previous research examining age difference in multiple social categorizations. Using faces as stimuli and Garner Selective Attention Paradigm, this study explored the different characteristics of implicit and explicit social categorization between young and older adults. The results showed that young perceivers explicitly categorized gender and age of the faces faster and more readily than older perceivers did. When young adults judged specific category (gender category in Experiment 1; age category in Experiment 2), they were interfered from the completing irrelative category; however, irrelative category could not capture older adults' attention. These results first suggest perceivers' age indeed plays an important role in multiple social categorizations.

FOXQ1/NDRG1 axis exacerbates hepatocellular carcinoma initiation via enhancing crosstalk between fibroblasts and tumor cells.

Cancer associated fibroblast (CAF) is a well-known microenvironment contributor for the development of hepatocellular carcinoma (HCC), while forkhead box (FOX) proteins are also critical to exacerbate HCC malignancy. However, whether FOX proteins are involved in the crosstalk between CAFs and HCC cells remains unclear. In the present study, we reveal that CAFs induce forkhead box Q1 (FOXQ1) expression, and N-myc downstream-regulated gene 1 (NDRG1) is therefore trans-activated to enhance HCC initiation. Intriguingly, pSTAT6/C-C motif chemokine ligand 26 (CCL26) signaling is induced by FOXQ1/NDRG1 axis, thus recruiting hepatic stellate cells (HSCs), the main cellular source of CAFs, to the tumor microenvironment. Thereby, tumor initiating properties are enhanced at least partly through a positive feedback loop between CAFs and HCC cells. Importantly, leflunomide, a pSTAT6 inhibitor that has been approved for the treatment of rheumatoid arthritis, significantly blocks the loop and HCC progression. High expression of CAF marker, ACTA2, and induced FOXQ1/NDRG1 axis in HCC tissues predict unfavorable prognosis. Collectively, our findings uncover a positive feedback loop between CAFs and FOXQ1/NDRG1 axis in neoplastic cells to drive HCC initiation, thus providing new potential therapeutic targets for HCC.

Effect of iron on cholesterol 7α-hydroxylase expression in alcohol-induced hepatic steatosis in mice.

Both iron and lipids are involved in the progression of alcoholic fatty liver disease (AFLD), but the interaction between iron and lipids in AFLD is unclear. Here, we tested the hypothesis that iron regulates the expression of genes involved in lipid metabolism through iron regulatory proteins (IRPs), which interact with the iron-responsive elements (IREs) in the untranslated regions (UTRs) of genes, resulting in lipid accumulation. Using "RNA structure software", we predicted the mRNA secondary structures of more than 100 genes involved in lipid metabolism to investigate whether the IRE structure exists in novel mRNAs. Cholesterol 7α-hydroxylase (Cyp7a1) has an IRE-like stem-loop, a noncanonical IRE structure, in its 3'-UTR. Cyp7a1 expression can be regulated by in vivo and in vitro iron treatment. In addition, the noncanonical IRE motif can efficiently bind both to IRP1 and IRP2. The results indicate that hepatic iron overloading in AFLD mice decreased Cyp7a1 expression and resulted in cholesterol accumulation, providing a new mechanism of iron-regulated gene transcription and translation through the interaction between iron and a noncanonical IRE structure in Cyp7a1 mRNA. This finding has significant implications in studying a proposed mechanism for the regulation of cholesterol homeostasis by an Fe/IRP/noncanonical IRE axis.

[Effect of Plastic Film Mulching on Methane Emission from a Vegetable Field].

Using the static opaque chamber method and choosing a chili-radish cropping system, a field experiment, located in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University in Chongqing, was conducted in situ for one year. Mulching and non-mulching treatments were set in the field, and the seasonal variation of CH4 flux and CH4 concentrations in the soil profile and the seasonal changes in soil moisture and temperature were observed for different treatments to explore the effect of plastic film mulching on soil moisture and temperature. The results showed that plastic film mulching can significantly improve the surface soil temperature during the pepper growing season in spring and summer (P<0.01), but no significant difference was seen during the radish growing season in autumn and winter (P>0.05). The soil moisture of the plastic film mulching treatment was significantly higher than that of no mulching in the radish growing season (P<0.05), but no significant difference was observed for the pepper growing season (P>0.05). During the whole observation period and under the condition of plastic film mulching and conventional planting, the CH4 flux from soil had no significant seasonal variation under all treatments, and the mean CH4 fluxes were -7.64 µg·(m2·h)-1 and -9.00 µg·(m2·h)-1, respectively. The cumulative CH4 emissions for plastic film mulching and conventional planting were -0.54 kg·hm-2 and -0.64 kg·hm-2, respectively, in the whole observation period, and all the treatments showed a net absorption of CH4 for the whole observation period. The results showed that the plastic film mulching could weaken the ability of CH4 as a sink of the CH4 for the whole observation period. The CH4 concentrations in different soil profiles were in the order 10 cm>20 cm>30 cm, and the concentrations of CH4 change patterns in different soil layers were almost identical during the whole observation period. The CH4 concentrations at the depths of 20 cm and 30 cm under the plastic film mulching soil were significantly lower than those under no mulching soil (P<0.05), but no significant difference was observed for the depth of 10 cm (P>0.05). Correlation analysis showed that, under the plastic film mulching conditions, CH4 flux and the 5 cm geothermal showed significant positive correlation (P<0.05), but CH4 flux and soil moisture showed significant negative correlation (P<0.05). However, under the conventional cultivation conditions, there were no correlations between CH4 flux and the 5 cm geothermal or soil moisture. There was also significant positive correlation between CH4 concentration in the 10 cm and 20 cm depth soil layers with the CH4 concentration in surface soil (P<0.01), and the CH4 concentration in the 30 cm depth soil layer had significant positive correlation with the surface soil temperatures and the 5 cm geothermal. There was no significant correlation between soil CH4 concentration and soil water content.

[Effects of Plastic Film Mulching on Nitrous Oxide Emissions from a Vegetable Field].

Considering the common cropping system (chili-radish rotation) in Southwest China, the objective of this study is to explore the effect of plastic film mulching on N2O flux, N2O concentrations in the soil profile, soil temperature, and humidity from a vegetable field. The method of the static opaque chamber was used and the experimental period lasted for one year. The results showed that the average flux of N2O was 1000.0 µg·(m2·h)-1 in the conventional treatment and 400.6 µg·(m2·h)-1 in the film mulching treatment during the chili growing period. The N2O flux of the film mulching treatment was significantly lower than that of conventional treatment (P<0.05). However, in the radish growing season, the N2O flux of the film mulching treatment was higher than that of conventional treatment, but the difference between the two treatments was not significant (P>0.05). N2O concentrations in the soil profile of the two treatments both increased with the increase in soil depth. The N2O concentrations showed significant correlations among the different soil profiles of each treatment; meanwhile, there was also a significant correlation between soil N2O concentrations at the same soil depth in different treatments. There was a significant positive correlation between the N2O concentration in different profiles and N2O fluxes in surface soils in the conventional treatment, but the N2O flux under the plastic mulching film treatment was only positively correlated with the N2O concentrations of 30 cm deep soil. The soil moisture and temperature observations showed that the effect of plastic film mulching on soil temperature was more significant in summer and the soil moisture was more prominent in autumn and winter. However, the results of the correlation analysis and principal component analysis showed that N2O emissions were mainly determined by the distribution of nitrogen in the soil and were affected by the change in soil total nitrogen content in the conventional treatment but N2O emissions were more sensitive to the variation in soil inorganic nitrogen in the film mulching treatment.

[Effects of Plastic Film Mulching on Methane and Nitrous Oxide Emissions from a Rice-Rapeseed Crop Rotation].

A field experiment was conducted in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University in Chongqing. Static opaque chamber and gas chromatography methods were used to study the effect of plastic film mulching on CH4 and N2O emissions characteristics from a rice-rapeseed crop rotation in situ for one year. The results showed that CH4 and N2O emissions are mainly concentrated in the early stages of the growth of each crop and there is a clear seasonal variation of CH4 emissions during the rice growing period and N2O in the rapeseed growing period. The CH4 flux changed from -0.45 to 1.90 mg·(m2·h)-1 and the N2O flux varied between -46.1 and 2040.7 µg·(m2·h)-1 over the entire year. Plastic film mulching was found to increase the total emissions of CH4 and N2 O, with the total CH4 emission of(27.22±4.48) kg·hm-2 over the entire year, which is 26.22% higher than that of the non-mulching treatment(19.93±0.56) kg·hm-2. The total amount of N2O emissions under film mulching treatment increased 16.6% from (11.27±2.77) kg·hm-2 under no mulching treatment to (13.14±0.82) kg·hm-2. The results analyzed for soil moisture and soil temperature showed that mulching significantly increased the soil moisture during the rapeseed season, while there was no obvious correlation with soil temperature (at depths of 5 cm and for the surface temperature) for each crop season. During the rapeseed growing season, CH4 and N2O emissions negatively correlated with soil moisture and has a significant negative correlation during the seedling period with film mulching treatment. Moreover, under the two treatments, the correlation between CH4 and N2O emissions and soil temperature was negligible. This study indicates that plastic film mulching impacts CH4 and N2O emissions at different growth stages of the crops, which changes the proportion of the emission of the two gases over the whole growth period, and promotes the emission of CH4 and N2O in the rice-rapeseed system. In the time scale of 100 years, the integrated global warming potentials (GWP) of CH4 and N2O emission under plastic film was a CO2 equivalent of 4213.00 kg·hm-2 compared with that under conventional treatment of 3454.17 kg·hm-2. Conventional emits 22.0% less CO2, indicating that plastic film mulching is not an effective measure for carbon sequestration.