Search

Key message: Through the histological, physiological, and transcriptome-level identification of the abscission zone of Pennisetum alopecuroides ‘Liqiu’, we explored the structure and the genes related to seed shattering, ultimately revealing the regulatory network of seed shattering in P. alopecuroides. Pennisetum alopecuroides is one of the most representative ornamental grass species of Pennisetum genus. It has unique inflorescence, elegant appearance, and strong stress tolerance. However, the shattering of seeds not only reduces the ornamental effect, but also hinders the seed production. In order to understand the potential mechanisms of seed shattering in P. alopecuroides, we conducted morphological, histological, physiological, and transcriptomic analyses on P. alopecuroides cv. ‘Liqiu’. According to histological findings, the seed shattering of ‘Liqiu’ was determined by the abscission zone at the base of the pedicel. Correlation analysis showed that seed shattering was significantly correlated with cellulase, lignin, auxin, gibberellin, cytokinin and jasmonic acid. Through a combination of histological and physiological analyses, we observed the accumulation of cellulase and lignin during ‘Liqiu’ seed abscission. We used PacBio full-length transcriptome sequencing (SMRT) combined with next-generation sequencing (NGS) transcriptome technology to improve the transcriptome data of ‘Liqiu’. Transcriptomics further identified many differential genes involved in cellulase, lignin and plant hormone-related pathways. This study will provide new insights into the research on the shattering mechanism of P. alopecuroides. [ABSTRACT FROM AUTHOR]

Background and aims: The frequent occurrence of extreme rainfall events results in soils experiencing drying–rewetting (DRW) cycles. Such rewetting can lead to a surge in soil CO2 emissions; however, the main regulatory factors involved in this priming effect are unclear. Methods: In this study, we conducted a meta-analysis using data extracted from 43 published papers, to determine the direct regulatory factors involved in the priming effect of soil CO2. Results: The results indicated that the priming effect of rewetting on soil CO2 emissions was influenced by ecosystem type, soil properties, climatic factors, and the number of DRW cycles. The priming effect was the highest in cropland but the lowest in grassland when taking flux values observed before rewetting as the control group. It was also greater in acidic soils (pH < 6.5) and soils with a high clay fraction (clay ≥ 30%) than in other soils. The effect size (lnRR) of soil CO2 emissions was exponentially related to the mean annual precipitation (MAP), and decreased with increases in MAP. In DRW experiments, the priming effect of the first rewetting on soil CO2 emissions was the largest, an effect that gradually decreased with the number of DRW cycles, before disappearing completely. Most importantly, soil moisture influenced the peak time and the pulse time of the priming effect: the greater the change in soil moisture, the longer the peak time duration; the higher the maximum soil moisture content after rewetting, the longer the pulse time duration; and the lower the initial soil moisture content, the bigger the priming effect. Conclusion: Generally, physical mechanisms, especially soil moisture, directly regulate the CO2 priming effect during DRW cycles. Thus, this study provides a theoretical basis for assessing and predicting the impact of future precipitation changes on soil carbon cycling. Future studies should also carefully monitor any changes in soil microorganisms in response to changes in soil moisture during DRW cycles, because these appear to be significantly involved in CO2 release from soils. [ABSTRACT FROM AUTHOR]

Main conclusion: The first complete mitochondrial genome of Carex (C. breviculmis) was sequenced and assembled, and its genomic signature was analyzed and the possible conformations of its mitochondrial genome were validated. Carex breviculmis is a very adaptable grass that is highly resistant to environmental stresses such as drought and low light. It is also admired as a landscape plant with high development prospects and scientific research value. In this study, the mitochondrial genome of C. breviculmis was assembled using Pacbio and Illumina sequencing data. We detected 267 pairs of repeats and found that three pairs of repeats could mediate the recombination of its mitochondrial genome and formed four possible conformations, of which we verified the two conformations mediated by the shortest pair of repeats using PCR amplification and Sanger sequencing. The major conformation of the C. breviculmis mitochondrial genome is a 1,414,795 bp long circular molecule with 33 annotated protein-coding genes, 15 tRNA genes, and three rRNA genes. We detected a total of 25 homologous sequences between the chloroplast and mitochondrial genomes, corresponding to 0.40% of the mitochondrial genome. Combined with the low GC content (41.24%), we conclude that the reduction in RNA editing sites in the C. breviculmis mitochondrial genome may be due to an accumulation of point mutations in C-to-T or retroprocessing events within the genome. The relatively low number of RNA editing sites in its mitochondrial genome could serve as important material for subsequent studies on the selection pressure of RNA editing in angiosperms. A maximum likelihood analysis based on 23 conserved mitochondrial genes from 28 species reflects an accurate evolutionary and taxonomic position of C. breviculmis. This research provided us with a comprehensive understanding of the mitochondrial genome of Carex and also provided important information for its molecular breeding. [ABSTRACT FROM AUTHOR]

Key message: Combination analysis of single-molecule long-read and Illumina sequencing provide full-length transcriptome information and shed new light on the anthocyanin accumulation mechanism of Pennisetum setaceum cv. 'Rubrum'. Pennisetum setaceum cv. 'Rubrum' is an ornamental grass with purple leaves widely used in landscaping. However, the current next-generation sequencing (NGS) transcriptome information of this species is not satisfactory due to the difficulties in obtaining full-length transcripts. Furthermore, the molecular mechanisms of anthocyanin accumulation in P. setaceum have not been thoroughly studied. In this study, we used PacBio full-length transcriptome sequencing (SMRT) combined with NGS technology to build and improve the transcriptomic datasets and reveal the molecular mechanism of anthocyanin accumulation in P. setaceum cv. 'Rubrum'. Therefore, 280,413 full-length non-chimeric reads sequences were obtained using the SMRT technology. We obtained 97,450 high-quality non-redundant transcripts and identified 5352 alternative splicing events. In addition, 93,066 open reading frames (ORFs), including 57,457 full ORFs and 2910 long non-coding RNA (lncRNAs) were screened out. Furthermore, 10,795 differentially expressed genes were identified using NGS. We also explored key genes, synthesis pathways, and detected lncRNA involved in anthocyanin accumulation, providing new insights into anthocyanin accumulation in P. setaceum cv. 'Rubrum'. To our best knowledge, we provided the full-length transcriptome information of P. setaceum cv. 'Rubrum' for the first time. The results of this study will provide baseline information for gene function studies and pave the way for future P. setaceum cv. 'Rubrum' breeding projects. [ABSTRACT FROM AUTHOR]

Pennisetum grasses (P. purpureum Schumach. 'Purple', P. alopecuroides (L.) Spreng. 'Liren' and P. alopecuroides (L.) Spreng. 'Changsui'), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility. [ABSTRACT FROM AUTHOR]

Interactions between weeds and crops often occur by resource competition or allelopathy. However, it is still unknown how local weed species influence artificially introduced switchgrass. In this study, four experiments were conducted to evaluate the inhibitory effects of redroot pigweed (Amaranthus retroflexus) and crabgrass (Digitaria sanguinalis) on germination and growth of the lowland tetraploid switchgrass cultivar 'Alamo' (Panicum virgatum cv. Alamo). Switchgrass germination was significantly inhibited in Petri dishes, with 48.1% and 33.9% inhibitions on germination rate by redroot pigweed and crabgrass root aqueous extracts, respectively, at 0.1 g mL−1 concentration. Significant inhibitory effects on switchgrass seedling biomass were observed at 5:5 ratio with redroot pigweed and crabgrass in glass jars, with 61.6% and 53.4% inhibitions on plant biomass, respectively. Under the same root segregation, redroot pigweed had a stronger inhibitory effect on switchgrass seedling growth than crabgrass. Growth of transplanted switchgrass seedlings was significantly inhibited by local weeds in the field, with 46.2% and 11.7% inhibitions on shoot biomass during the first and second growing seasons, respectively. However, no significant growth reduction in switchgrass was detected in the third growing season. These findings further our understanding of weed–crop interactions and could help develop weeds management strategies with ecological security. [ABSTRACT FROM AUTHOR]

Non-native invasive plant species influence plant community composition and competitively eradicate native species. However, there is doubt regarding how global invasive species increase and explosively interfere with native plants. Invasive plants always have strong allelopathic potential. In this study, allelopathic effects of switchgrass on redroot pigweed and crabgrass growth were investigated by field and laboratory experiments. Within a 0.4-m distance of switchgrass, density and shoot biomass of native species were significantly suppressed in the field, with 95.1% and 93.0% inhibition on density of redroot pigweed and crabgrass and with 99.0% and 97.7% inhibition on shoot biomass, respectively, during the third growing season. Significant inhibitory effects on shoot and root biomass were observed at the 5:5 (switchgrass–native species) proportion in glass bottles, by 41.57% and 51.21% for shoot and root biomass of redroot pigweed and by 33.42% and 56.95% for shoot and root biomass of crabgrass, respectively. Results of a glass bottle experiment showed that shoot and root biomass of redroot pigweed and crabgrass could be significantly inhibited by contact with switchgrass root. Results of a Petri dish experiment showed that aqueous extracts of switchgrass significantly inhibited germination process of both species at high concentrations, with 90.74% and 18.62% inhibition on germination rate and plumule length of redroot pigweed and with 63.59%, 16.38%, and 19.92% inhibition on germination rate, plumule, and radicle lengths of crabgrass, respectively, at the concentration of 0.1 g·mL−1. This report demonstrated that switchgrass had allelopathic effects on redroot pigweed and crabgrass growth. [ABSTRACT FROM AUTHOR]

Pennisetum × advena (purple fountain grass) is an ornamental grass with considerable commercial value. In vitro induction of hexaploids and evaluation of the morphological and anatomical traits in P. × advena were conducted in this study. Nine independent hexaploids were generated from calli, which was initiated from immature inflorescence tissue of triploid P. × advena, treated with 0.1% colchicine for 24 h. Their ploidy levels were first screened by flow cytometry and further identified by chromosome counting. Compared with the triploids, the hexaploids showed a significant delay in flowering, and reduction in plant height, the number of tillers and number of inflorescences per plant, leaf length and width, inflorescence diameter, and the number of florets per inflorescence, but an increase in floret fresh weight, and anther diameter and length. Pollen grains in the hexaploids were well developed, and their fertility was restored. The production of hexaploids of P. × advena by colchicine treatment, and assessment of their growth parameters and pollen fertility, provide important information for future breeding of P. × advena. Key message: Nine independent hexaploids were generated from calli derived from immature inflorescence tissue of triploid Pennisetum × advena by a colchicine treatment, and their morphological and anatomical traits were evaluated. [ABSTRACT FROM AUTHOR]

Paraffin, due to its linear chain and saturated hydrocarbons with low thermal conductivity, is difficult to transfer energy effectively. Using amphiphilicity of graphene oxide (GO), Pickering emulsion of paraffin@GO was obtained and then paraffin@graphene microencapsulated phase change materials (MEPCMs) were achieved by chemical reduction through adding hydrazine hydrate. Thermally conductive PCMs with segregated structure were constructed by hot compression of paraffin@graphene microencapsules. Scanning electronic microscopy, differential scanning calorimetry and thermal conductivity test were used to characterize microstructure and thermal properties of MEPCMs. Meanwhile, the effect of graphene on the phase change latent heat and phase transition temperature was investigated. Results indicated that GO did not react with paraffin during the process of chemical reduction and the obtained MEPCMs were regular spheres. These MEPCMs had paraffin content of 99% or even more. Graphene working as shell materials increased the phase change latent heat of paraffin from 227.6 to 232.4 J/g, without affecting the phase transition temperature. The hot-compress molding makes graphene shell form segregated structure with more thermal pathways, further enhancing thermal conductivity. The segregated-structure PCMs with high latent heat and thermal conductivity can be applied in energy storage field. [ABSTRACT FROM AUTHOR]

Biochar produced from rice straw (RC) and maize stalk (MC) was amended to the heavy metal-contaminated soil to investigate the effects of different biochar feedstock and particle size (fine, moderate, coarse) on the accumulation of Cd, Zn, Pb, and As in Brassica chinensis L. (Chinese cabbage). The concentrations of Cd, Zn, and Pb in shoot were decreased by up to 57, 75, and 63%, respectively, after biochar addition (4%). Only MC decreased As concentration in B. chinensis L. shoots by up to 61%. Biochar treatments significantly decreased NHNO-extractable concentrations of Cd, Zn, and Pb in soil by 47-62, 33-66, and 38-71%, respectively, yet increased that of As by up to 147%. Amendment of RC was more effective on immobilizing Cd, Zn, and Pb, but mobilizing soil As, than MC. A decrease in biochar particle size greatly contributed to the immobilization of Cd, Zn, and Pb in soil and thereby the reduction of their accumulations in B. chinensis L. shoots, especially RC. Increases in soil pH and extractable P induced by biochar addition contributed to the sequestration of Cd, Zn, and Pb and the mobilization of As. Shoot biomass, root biomass, and root system of B. chinensis L. were enhanced with biochar amendments, especially RC. This study indicates that biochar addition could potentially decrease Cd, Zn, Pb, and As accumulations in B. chinensis L., and simultaneously increase its yield. A decrease in biochar particle size is favorable to improve the immobilization of heavy metals (except As). The reduction in Cd, Zn, Pb, and As levels in B. chinensis L. shoots by biochar amendment could be mainly attributed to a function of heavy metal mobility in soil, plant translocation factor, and root uptake. [ABSTRACT FROM AUTHOR]

Pennisetum species are widely used as ornamental grasses and may be a valuable genetic resource for their breeding to broaden its genetic basis. At present, new ornamental Pennisetum cultivars are primarily bred via somaclone, which increases the number of variants. It is difficult to estimate whether the suspected variants are authentic in genetic features by morphological traits because of their many limitations. Moreover, although the phylogenetic classification of the Pennisetum genus has been approved in some morphological and cytological studies, genetic evidence is lacking. In the present study, we developed 15 specific simple sequence repeat (SSR) markers with a large amount of polymorphisms and strong distinguishing abilities for Pennisetum ornamental grasses using magnetic bead enrichment. These markers, together with the other 11 reported polymorphic SSRs, were further used for the identification of a broad collection of 55 Pennisetum samples, including nine original taxa and 46 suspected variants. After comparing the genetic characteristics between each variant and its corresponding original taxon, we verified 20 suspected variants that possess the potential to become new, commercially desirable cultivars. The nine original taxa and the 20 verified variants were identified based on the polymorphisms of six core loci, and unique molecular identities with 15 denary digits for each taxon were further established. The rationality of the traditional phylogenetic classification system of the Pennisetum genus was further verified using 147 polymorphic alleles. The present study promotes the protection, registration, breeding, and international communication of Pennisetum ornamental grasses. [ABSTRACT FROM AUTHOR]

A novel composites based on ethylene-propylene-diene monomer (EPDM) rubber for gamma shielding were prepared by using carbon blacks (CB) and ball milled PbWO (PWO) powder as fillers. The microstructure of ball milled PWO powder which has a uniform morphology in these composites was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD). The mechanical and shielding tests were performed to determine mechanical and radiation attenuation properties, respectively. The results show these materials exhibit excellent mechanical and radiation-resistance properties. [ABSTRACT FROM AUTHOR]

In this study, silica aerogel microspheres were prepared through sol–gel method with tetraethyl orthosilicate as the silicon source. Thermal insulation coatings were prepared by mixing silica aerogel and acrylic emulsion. The relationships between the thermal conductivity and volume fractions, densities, sizes, and interfaces of silica aerogel microspheres were investigated through scanning electron microscopy and thermal conductivity analysis. The thermal insulation mechanism of composite coating was discussed in detail. Results showed that the aggregations prevented the decrease of thermal conductivity in the coating when the volume fraction of silica aerogel microspheres was lower than 30 %. However, the pores in the coating reduced the thermal conductivity when the volume fraction was higher than 30 %. The porosity of silica aerogel increased with the declining density, which improved the thermal insulation performance of silica aerogel and reduced the thermal conductivity of the coating. The thermal conductivity of the coating with large microspheres was lower than that with small microspheres at low volume fractions. However, the thermal conductivity of the coating with small silica aerogel microspheres was low because of their large interfacial thermal resistance at high volume fractions. Wetting agents were beneficial in improving the compatibility of hydrophobic aerogel microspheres and polymer, improving the volume fractions of silica aerogel microspheres in the coating, and reducing the thermal conductivity of the coating. [ABSTRACT FROM AUTHOR]

Background and aims: Many meadows are experiencing severe degradation due to the effects of global climate change and other human-related activity, especially overgrazing. The impact of grazing may however vary in different sites, but the dynamics and mechanisms associated with grazing-related meadow degradation on soil microbial biomass structure and function in different locations are still unclear.To address this we examined three alpine meadows with different grazing sites in northwest China, which included grazing in winter and summer, in each of which there were four degradation gradients, varying from no degradation to severe degradation.At the Maqin site, grazing during the summer resulted in higher concentrations of microbial carbon (MBC), nitrogen (MBN), and phosphorus (MBP) compared to grazing during winter. Undegraded meadows (ND) also had higher MBC concentrations compared to low (LD), medium (MD), or severely degraded (SD) ones at the three sites. However, the homeostasis analysis revealed that the elemental stoichiometries were strictly controlled, despite significant degradation-related effects on the concentrations of MBC, MBN, and MBP, indicating relatively stable coupling relationships among C, N, and P.The random forest and partitioning variation analyses showed that edaphic factors play the more important roles in regulating microbial biomass and elemental composition in the different sites. Overall, these results suggest that the effects of degradation on soil microbial biomass concentrations and the stoichiometries are context dependent, particularly with regard to the impact of background soil properties, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to grazing-related degradation.Methods: Many meadows are experiencing severe degradation due to the effects of global climate change and other human-related activity, especially overgrazing. The impact of grazing may however vary in different sites, but the dynamics and mechanisms associated with grazing-related meadow degradation on soil microbial biomass structure and function in different locations are still unclear.To address this we examined three alpine meadows with different grazing sites in northwest China, which included grazing in winter and summer, in each of which there were four degradation gradients, varying from no degradation to severe degradation.At the Maqin site, grazing during the summer resulted in higher concentrations of microbial carbon (MBC), nitrogen (MBN), and phosphorus (MBP) compared to grazing during winter. Undegraded meadows (ND) also had higher MBC concentrations compared to low (LD), medium (MD), or severely degraded (SD) ones at the three sites. However, the homeostasis analysis revealed that the elemental stoichiometries were strictly controlled, despite significant degradation-related effects on the concentrations of MBC, MBN, and MBP, indicating relatively stable coupling relationships among C, N, and P.The random forest and partitioning variation analyses showed that edaphic factors play the more important roles in regulating microbial biomass and elemental composition in the different sites. Overall, these results suggest that the effects of degradation on soil microbial biomass concentrations and the stoichiometries are context dependent, particularly with regard to the impact of background soil properties, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to grazing-related degradation.Results: Many meadows are experiencing severe degradation due to the effects of global climate change and other human-related activity, especially overgrazing. The impact of grazing may however vary in different sites, but the dynamics and mechanisms associated with grazing-related meadow degradation on soil microbial biomass structure and function in different locations are still unclear.To address this we examined three alpine meadows with different grazing sites in northwest China, which included grazing in winter and summer, in each of which there were four degradation gradients, varying from no degradation to severe degradation.At the Maqin site, grazing during the summer resulted in higher concentrations of microbial carbon (MBC), nitrogen (MBN), and phosphorus (MBP) compared to grazing during winter. Undegraded meadows (ND) also had higher MBC concentrations compared to low (LD), medium (MD), or severely degraded (SD) ones at the three sites. However, the homeostasis analysis revealed that the elemental stoichiometries were strictly controlled, despite significant degradation-related effects on the concentrations of MBC, MBN, and MBP, indicating relatively stable coupling relationships among C, N, and P.The random forest and partitioning variation analyses showed that edaphic factors play the more important roles in regulating microbial biomass and elemental composition in the different sites. Overall, these results suggest that the effects of degradation on soil microbial biomass concentrations and the stoichiometries are context dependent, particularly with regard to the impact of background soil properties, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to grazing-related degradation.Conclusion: Many meadows are experiencing severe degradation due to the effects of global climate change and other human-related activity, especially overgrazing. The impact of grazing may however vary in different sites, but the dynamics and mechanisms associated with grazing-related meadow degradation on soil microbial biomass structure and function in different locations are still unclear.To address this we examined three alpine meadows with different grazing sites in northwest China, which included grazing in winter and summer, in each of which there were four degradation gradients, varying from no degradation to severe degradation.At the Maqin site, grazing during the summer resulted in higher concentrations of microbial carbon (MBC), nitrogen (MBN), and phosphorus (MBP) compared to grazing during winter. Undegraded meadows (ND) also had higher MBC concentrations compared to low (LD), medium (MD), or severely degraded (SD) ones at the three sites. However, the homeostasis analysis revealed that the elemental stoichiometries were strictly controlled, despite significant degradation-related effects on the concentrations of MBC, MBN, and MBP, indicating relatively stable coupling relationships among C, N, and P.The random forest and partitioning variation analyses showed that edaphic factors play the more important roles in regulating microbial biomass and elemental composition in the different sites. Overall, these results suggest that the effects of degradation on soil microbial biomass concentrations and the stoichiometries are context dependent, particularly with regard to the impact of background soil properties, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to grazing-related degradation. [ABSTRACT FROM AUTHOR]