Relationship between negative air ion and PM2.5 in Quercus variabilis under natural conditions.

In recent years, PM2.5 pollution has become a most important source of air pollution. Prolonged exposure to high PM2.5 concentrations can give rise to severe health issues. Negative air ion (NAI) is an important indicator for measuring air quality, which is collectively known as the 'air vitamin'. However, the intricate and fluctuating meteorological conditions and vegetation types result in numerous uncertainties in the correlation between PM2.5 and NAI. In this study, we collected data on NAI, PM2.5, and meteorological elements through positioning observation during the period of June to September in 2019 and 2020 under the condition of relatively constant leaf area in Quercus variabilis forest, a typical forest in warm temperate zones. We investigated the spatiotemporal variation of PM2.5 and NAI under consistent meteorological conditions, established the correlation between PM2.5 and NAI, and explicated the impact mechanism of PM2.5 on NAI in natural conditions. The results showed that NAI decreased exponentially with the increases in natural PM2.5, with a significant negative correlation (y=1148.79x-0.123). The decrease rates of NAI in PM2.5 concentrations of 0-20, 20-40, 40-80, 80-100 and 100-120 µg·m-3 were 40.1%, 36.2%, 9.4%, 2.4%, 5.1% and 6.8%, respectively. Results of the sensitivity analysis showed that the PM2.5 concentration range of 0-40 µg·m-3 was the sensitive range that affected NAI. Our findings could provide a scientific basis for better understanding the response mechanisms of NAI to environmental factors.

Soil microbial community characteristics and the influencing factors at different elevations on the eastern slope of Helan Mountain, Northwest China.

As an important bridge connecting aboveground communities and belowground biological processes, soil microorganisms play an important role in regulating belowground ecological processes. The altitudinal changes and driving factors of soil microbial community in mountain ecosystem in arid region are still unclear. We measured soil physicochemical properties at seven altitudes in the range of 1300-2800 m in Helan Mountains, and investigated the understory community composition, soil physicochemical properties, and soil microbial community. The driving factor for soil microbial community was explored by variance partitioning analysis and redundancy analysis. The results showed that the total amount of soil microorganisms and bacterial biomass first increased and then decreased with the increases of altitude, fungi, actinomyces, arbuscular mycorrhizal fungi, Gram-positive bacteria, and Gram-negative bacteria groups showed a gradual increase. The variation of fungal-to-bacterial ratio (F/B) along the altitude showed that the cumulative ability of soil bacteria was stronger than that of fungi at low altitudes, while the pattern is opposite at high altitudes. The ratio of Gram-positive bacteria to Gram-negative bacteria (GP/GN) showed an overall decreasing trend with the increases of altitude, indicating that soil bacteria and organic carbon availability changed from "oligotrophic" to "eutrophication" and from "low" to "high" transition as the altitude increased. Vegetation properties, soil physical and chemical properties jointly accounted for 95.7% of the variation in soil microbial community. Soil organic carbon (SOC), soil water content (SWC), and total nitrogen (TN) were significantly correlated with soil microbial community composition. Our results revealed the distribution pattern and driving factors of soil microbial communities at different elevations on the eastern slope of Helan Mountain, which would provide theoretical basis and data support for further understanding the interaction between plant-soil-microorganisms in arid areas.

Effect of light intensity on negative air ion under phytotron control.

Negative air ion (NAI) is an important index for measuring air quality and has been widely recognized to be influenced by photosynthesis processes. However, vegetation type and light intensity are also known to impact NAI, contributing to significant uncertainties in the relationship between light and NAI. In this paper, we selected Pinus bungeana, Platycladus orientalis and Buxus sinica as research subjects and obtained their NAI, light intensity, and meteorological data through synchronous observation under the relatively stable condition of the phytotron. We analyzed the change characteristics of NAI and the difference of NAI production ability in needle and broadleaf vegetation under different light intensities. Finally, we determined the relationship and underlying mechanism governing light intensity and NAI using diverse tree species. The results showed that the influence of light on NAI was significant. In the environment without vegetation, the influence of different light intensities on NAI was not significant, and the mean NAI concentration was 310 ions·cm-3. Conversely, in the presence of vegetation, NAI showed a "single-peak" trend with increasing light intensity. The NAI concentration of the three tree species was significantly higher than under different light intensities when vegetation was not present. The NAI promoting ability of P. bungeana was the highest (675 ions·cm-3), followed by P. orientalis (478 ions·cm-3) and B. sinica (430 ions·cm-3), which increased by 117.5%, 53.9% and 38.6% compared to the environment without vegetation. The NAI growth rate was significantly different between needle and broadleaf vegetation based on the specific tridimensional green biomass. Additionally, the NAI growth rates of P. bungeana and P. orientalis were 647 and 295 ions·cm-3·m-3, respectively, which were 3.06 and 1.39 times that of B. sinica (211 ions·cm-3·m-3). The piecewise equation fitting effect of NAI and light intensity was better for different tree species, the determination coefficients (R2) of P. bungeana, P. orientalis and B. sinica were 0.926, 0.916 and 0.880, and the root mean square errors (RMSE) were 7.157, 6.008 and 5.389 ion·cm-3, respectively. Altogether, our study provides a theoretical basis as well as technical support for the construction of healthy vegetation stands, the selection of preferred tree species, and the optimization of vegetation models, and promotes air quality and the provision of ecosystem functions and services.

[Risk Assessment and Sources of Heavy Metals in Farmland Soils of Yellow River Irrigation Area of Ningxia].

The farmland environment is directly related to the quality and safety of agricultural products. In order to understand the characteristics and main influencing factors of heavy metals in farmland soil in the Yellow River irrigation area of Ningxia, sampling and monitoring were conducted for five consecutive years from 2017 to 2021, and the distribution characteristics and correlation of heavy metals were analyzed. The pollution status and potential ecological risks of heavy metals were evaluated, and the main sources of heavy metals in farmland were analyzed. The results showed that the average values of Pb, As, Zn, Ni, Cu, Hg, Cr, and Cd in the soil of the Ningxia Yellow River irrigation area were 19.74, 11.67, 66.88, 29.09, 22.55, 0.03, 62.27, and 0.19 mg·kg-1, respectively, which were enriched to some extent compared with the background values of the soil environment in Ningxia. Among them, Hg and Cd had middle- and high-grade ecological risk points; however, none of them exceeded the control value of agricultural land soil pollution risk, and all sampling sites had no high-risk or extremely high-risk levels. The results of source analysis based on positive matrix factorization (PMF) and correlation analysis showed that there were five main sources of heavy metals in farmland soil in the study area: natural sources, mixed sources of industrial and mining activities and the production and life of residents, transportation sources, agricultural production activities sources, and industrial sources, with contribution rates of 26.54%, 25.59%, 22.52%, 15.63%, and 9.72%, respectively. On the whole, the heavy metals in farmland soil in the Ningxia Yellow River irrigation area did not exceed the standard, and there was no high-level ecological risk. The production environment of the farmland soil was good, but the contribution rate of human activities to soil heavy metals was large.

Caspase 3-like protease is involved in ethylene-induced programmed cell death during aerenchyma formation in Helianthus annuus stem.

Previous research has reported that hypoxic conditions and ethylene treatments greatly trigger programmed cell death (PCD) occurrence and induce the formation of aerenchyma to adapt stress environment in Helianthus annuus stem. Caspase 3-like protease (CLP) as regulatory signals, also be involved in the process of PCD to adapt the low oxygen environment. However, the relationships between ethylene and CLP have seldom been reported. Herein, To understand the regulatory role of ethylene and CLP signaling molecules in aerenchyma formation, we investigated the effects of exogenous ethephon (ET), ethylene perception inhibitor 1-methylcyclopropene (1-MCP), and the treatment of 1-MCP + ET on morphological, physiological characteristics and aerenchyma formation in H. annuus stem. The results showed that lysigenous aerenchyma formation in H. annuus stem is induced by ET, and immunohistochemistry assay indicate CLP activity is raised at the formation stage of aerenchyma formation, and decreased at the expanding phase of aerenchyma formation. Western blotting illustrate the expression of CLP is also increased within 8 h after ethylene signaling inducing aerenchyma formation, and the activities of CLP are higher in ET treated seedlings than the control and 1-MCP treated seedlings. The same phenomenon was also observed by caspase-3 activity assay. These results revealed there is a causal and interdependent relationship between ET and CLP signaling during the process of aerenchyma formation, which regulating PCD initiation in H. annuus stem.

[Spatial-temporal differentiation and driving factors of vegetation coverage in Ningxia Helan Mountain based on geodetector]. / åŸºäºŽåœ°ç†æŽ¢æµ‹å™¨çš„å®å¤è´ºå °å±±æ¤è¢«è¦†ç›–åº¦æ—¶ç©ºåˆ†å¼‚åŠé©±åŠ¨å› å­.

Monitoring the regional changes in vegetation coverage and analyzing its driving factors are beneficial to realizing the sustainable development of ecological environment. Based on Landsat 5/8 remote sensing images from 1989 to 2021, vegetation coverage of Helan Mountain in Ningxia was estimated by pixel dichotomy model. In addition, the influence of 10 factors, including environmental factors and human factors, on the spatial-temporal variations of vegetation coverage was quantified by geodetector. The results showed that average vegetation coverage was 35.8% in the study area from 1989 to 2021. On the temporal scale, it showed an increasing trend, with an average increasing rate of 0.043·(10 a)-1. On the spatial scale, vegetation coverage presented a distribution characteristic of decreasing from southwest to northeast. 58.1% of vegetation coverage in the study area would continue to improve in the future, but 30.7% of vegetation would have the potential risk of degradation. Precipitation was the dominant environmental factor driving the distribution of vegetation. Compared with single factor, the interaction between environmental factors and human factors had a stronger impact on vegetation coverage, while the interaction between precipitation and other factors played a leading role.

De novo transcriptomic analysis to identify differentially expressed genes during the process of aerenchyma formation in Typha angustifolia leaves.

Lysigenous aerenchyma is formed through programmed cell death (PCD) in Typha angustifolia leaves. However, the genome and transcriptome data for this species are unknown. To further elucidate the molecular basis of PCD during aerenchyma formation in T. angustifolia leaves, transcriptomic analysis of T. angustifolia leaves was performed using Illumina sequencing technology, revealing 73,821 unigenes that were produced by assembly of the reads in T1, T2 and T3 samples. The important pathways, such as programmed cell death (PCD), aerenchyma formation, and ethylene responsiveness were regulated by these unigenes. 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) were highly up-regulated as key enzymes for ethylene synthesis, along with respiratory burst oxidase homolog (RBOH), metallothionein, calmodulin-like protein (CML), and polygalacturonase (PG), may collectively explain the PCD involved in T. angustifolia aerenchyma formation. We hypothesize that fermentation, metabolism and glycolysis generate ATP for PCD. We searched the 73,821 unigenes against protein databases, and 24,712 were annotated. Based on sequence homology, 16,012 of the 73,821 annotated unigenes were assigned to one or more Gene Ontology (GO) terms. Meanwhile, a total of 9537 unigenes were assigned to 126 pathways in the KEGG database. In summary, this investigation provides important guidelines for exploring the molecular mechanisms of aerenchyma formation in aquatic plants.

Programmed Cell Death and Aerenchyma Formation in Water-Logged Sunflower Stems and Its Promotion by Ethylene and ROS.

Previous studies have shown that waterlogging/ hypoxic conditions induce aerenchyma formation to facilitate gas exchange. Ethylene (ET) and reactive oxygen species (ROS), as regulatory signals, might also be involved in these adaptive responses. However, the interrelationships between these signals have seldom been reported. Herein, we showed that programmed cell death (PCD) was involved in aerenchyma formation in the stem of Helianthus annuus. Lysigenous aerenchyma formation in the stem was induced through waterlogging (WA), ethylene and ROS. Pre-treatment with the NADPH oxidase inhibitor diphenyleneiodonium (DPI) partially suppressed aerenchyma formation in the seedlings after treatment with WA, ET and 3-amino-1, 2, 4-triazole (AT, catalase inhibitor). In addition, pre-treatment with the ethylene perception inhibitor 1-methylcyclopropene (1-MCP) partially suppressed aerenchyma formation induced through WA and ET in the seedlings, but barely inhibited aerenchyma formation induced through ROS. These results revealed that ethylene-mediated ROS signaling plays a role in aerenchyma formation, and there is a causal and interdependent relationship during WA, ET and ROS in PCD, which regulates signal networks in the stem of H. annuus.

The involvement of programmed cell death in inflated leaf petiole morphogenesis in Trapa pseudoincisa.

Trapa plants (Trapaceae) have an inflated leaf petiole called a spongy airbag. The aims of this study were to assess the involvement of programmed cell death (PCD) in the process of inflated leaf petiole morphogenesis. In this paper, light and transmission electron microscopy (TEM) were used to investigate cytological events and the development of inflated leaf petiole. During this process, the inflated leaf petiole of Trapa pseudoincisa L. undergoes a developmental process, changing from solid to hollow phase. Debris from the degraded cells was seldom observed in the transverse sections of leaf petioles, but some degraded cells with an abnormal morphology were observed in longitudinal sections. Cytoplasmic changes, such as disrupted vacuoles, degraded plastids, and the emergence of secondary vacuoles were observed during leaf petiole morphogenesis. In addition, gel electrophoresis and TUNEL assays were used to evaluate DNA cleavage during petiole morphogenesis. DNA internucleosomal cleavage and TUNEL-positive nuclei indicate that the typical PCD features of DNA cleavage occurred early in the process. These results revealed that PCD plays a critical role in inflated leaf petiole morphogenesis. Additionally, a trans-disciplinary systems approach is required that recognises the necessity for integration of cytological and molecular characteristics for identification of aerenchyma type.

The complete chloroplast genome sequence of Fargesia qinlingensis (Poaceae): an endemic to China.

The complete chloroplast genome of Fargesia qinlingensis (Poaceae) has been reconstructed from the whole-genome Illumina sequencing data. The complete chloroplast genome sequence of F. qinlingensis obtained in this study was 139,640 bp in length, with a large single copy (LSC) region of 83,220 bp, a small single copy (SSC) region of 12,826 bp, separated by two inverted repeat (IR) regions of 21,797 bp each. The GC content was 38.9%, and in the LSC, SSC, and IR regions were 37.0%, 33.2%, and 44.2%, respectively. A total of 130 genes were annotated, including 83 protein-coding genes (PCGs), 39 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. The result of the phylogenetic analysis showed that F. qinlingensis was more closely related to the species of F. denudata.

Leaf-shape remodeling: programmed cell death in fistular leaves of Allium fistulosum.

Some species of Allium in Liliaceae have fistular leaves. The fistular lamina of Allium fistulosum undergoes a process from solid to hollow during development. The aims were to reveal the process of fistular leaf formation involved in programmed cell death (PCD) and to compare the cytological events in the execution of cell death to those in the unusual leaf perforations or plant aerenchyma formation. In this study, light and transmission electron microscopy were used to characterize the development of fistular leaves and cytological events. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assays and gel electrophoresis were used to determine nuclear DNA cleavage during the PCD. The cavity arises in the leaf blade by degradation of specialized cells, the designated pre-cavity cells, in the center of the leaves. Nuclei of cells within the pre-cavity site become TUNEL-positive, indicating that DNA cleavage is an early event. Gel electrophoresis revealed that DNA internucleosomal cleavage occurred resulting in a characteristic DNA ladder. Ultrastructural analysis of cells at the different stages showed disrupted vacuoles, misshapen nuclei with condensed chromatin, degraded cytoplasm and organelles and emergence of secondary vacuoles. The cell walls degraded last, and residue of degraded cell walls aggregated together. These results revealed that PCD plays a critical role in the development of A. fistulosum fistular leaves. The continuous cavity in A. fistulosum leaves resemble the aerenchyma in the pith of some gramineous plants to improve gas exchange.

Programmed cell death: a mechanism for the lysigenous formation of secretory cavities in leaves of Dictamnus dasycarpus.

The formation of secretory cavities in Rutaceae has been the subject of great interest. In this study, cytological events that are involved in the lysigenous formation of the secretory cavities in the leaves of Dictamnus dasycarpus are characterized by an interesting pattern of programmed cell death (PCD). During the developmental process, clusters of cells from a single protoepidermal cell embark on different trajectories and undergo different cell death fates: the cell walls of the secretory cells have characteristics of thinning or complete breakdown, while the sheath cells present a predominantly thick-walled feature. A DAPI assay shows deformed nuclei that are further confirmed to be TUNEL-positive. Gel electrophoresis indicates that DNA cleavage is random and does not result in ladder-like DNA fragmentation. Ultrastructurally, several remarkable features of PCD have been determined, such as misshapen nuclei with condensed chromatin and a significantly diffused membrane, degenerated mitochondria and plastids with disturbed membrane systems, multivesicular bodies, plastolysomes, vacuole disruption and lysis of the center secretory cell. Cytological evidence and Nile red stains exhibit abundant essential oils accumulated in degenerated outer secretory cells after the dissolution of the center secretory cell. In addition, explanations of taxonomic importance and the relationship between PCD and oil droplet accumulation in the secretory cavities are also discussed.

[Evaluation of urban human settlement quality in Ningxia based on AHP and the entropy method].

As one of the key indicators of the urbanization and the sustainable development of cities, urban human settlement quality has been a hot issue. In this paper, an evaluation system containing indicators related to four aspects (ecological, social, humanities and economic environments) was established to assess the urban human settlement quality in five main cities in Ningxia Hui Autonomous Region, Northwest China. After calculating each indicator' s weight in the evaluation system through AHP and the entropy method, the quality of urban human settlement was analyzed. Results showed that Yinchuan had a score of 0. 85 for the quality of human settlement, Shizuishan 0.62, Wuzhong 0.43, Zhongwei 0.33, and Guyuan 0.32, respectively. Shizuishan got the highest score in the eco-environment aspect, and Yinchuan had the highest scores for social, humanities and economic environments. Zhongwei and Guyuan had relatively low scores in all the four urban human settlement aspects. Coordination analysis showed that internal coordination was moderate for Yinchuan (0.79) and Shizuishan (0.72), and relatively good for the other cities. However, coordination was relatively poor among the five cities, especially in social environment (0.48). These results suggested that an unsatisfied situation existed in terms of the urban human settlement quality in Ningxia, and that corresponding measures should be taken to accelerate the development of vulnerable indicators, so as to coordinate all the urban human settlement aspects within and among cities.

Localization and dynamic change of saikosaponin in root of Bupleurum chinense.

Anatomical, histochemical and phytochemical methods were used to investigate the structure, the localization and content changes of total saikosaponin and saikosaponin-a of the roots of Bupleurum chinense DC. at different developmental stages. Results showed that saikosaponin was mainly distributed in pericycle and primary phloem in the young root; but in the mature root, it was mainly distributed in vascular cambium and secondary phloem. During the whole growth period from the pre-blossom, blossom, fruit, and fruit mature periods until the pre-withering period, it was in the fruit mature period that both the total saikosaponin content and the saikosaponin-a content reached the highest level. So the last 20 d of October was considered as the right collecting season for the drug of B. chinense. In addition, the quality of 1-year-old drug was better than that of 2-year-old drug due to its higher saikosaponin content. On the other hand, judging from the external characteristics of the drug, the one with an acerose taproot and more lateral roots was of better quality. The results offered theoretical bases for selecting medicinal material of high quality and determining the most appropriate harvesting stage and part of B. chinense.