Responses of tropical tree species to urban air pollutants: ROS/RNS formation and scavenging

A Modified Polydopamine Nanoparticle Loaded with Melatonin for Synergistic ROS Scavenging and Anti-Inflammatory Effects in the Treatment of Dry Eye Disease

Dry eye disease (DED) is a multifaceted ocular surface disorder that significantly impacts patients' daily lives and imposes a substantial economic burden on society. Oxidative stress, induced by the overproduction of reactive oxygen species (ROS), is a critical factor perpetuating the inflammatory cycle in DED. Effectively scavenging ROS is essential to impede the progression of DED. In this study, boronophenylalanine- containing polydopamine (PDA-PBA) nanoparticles are developed loaded with melatonin (MT), which are blended with poly(vinyl alcohol) (PVA) to create eye drops PVA/ PDA-PBA@MT (PPP@MT). In vitro and in vivo studies demonstrate that PPP@MT exhibits dual functionalities in reducing ROS production and downregulating inflammatory pathways, thereby preserving mitochondrial integrity and further inhibiting programmed cell death. Following PPP@MT treatment, tear secretion, corneal structure, and the number of goblet cells are markedly restored in a mouse model of dry eye, indicating the therapeutic efficacy of this agent. Collectively, PPP@MT, characterized by minimal side effects and favorable bioavailability, offers promising therapeutic insights for the management of DED and other ROS-mediated disorders.

Biogenic volatile organic compounds (BVOCs) emissions and physiological changes in Pinus densiflora and Quercus acutissima seedlings under elevated particulate matter (PM)

Urban trees effectively reduce air pollution, including particulate matter (PM), which is a major concern in East Asia. While acting as biofilters, urban trees can be affected by PM exposure, which hinders their growth and physiological functions, thereby reducing their pollution mitigation ability. Trees absorb pollutants but also emit biogenic volatile organic compounds (BVOCs), which can act as precursors to other forms of air pollution. To better understand the effects of PM on urban trees, this study examined how two tree species, Pinus densiflora and Quercus acutissima, respond to elevated PM levels under controlled conditions at a concentration of 300 μg m-3. The aim was to investigate how increased PM levels affect BVOCs emissions and physiological responses in seedlings, and how these physiological changes influence BVOCs emission pattern. The results revealed species-specific responses in BVOCs emissions under PM stress with being especially oxygenated monoterpenes more than non‑oxygenated monoterpenes. Increased PM adsorption was found to reduce photosynthetic abilities, including photosynthesis (Anet), carboxylation capacity (Vcmax), and electron transport rate (J). This reduction in photosynthetic efficiency was further evidenced by decreased chlorophyll content and light absorption, which were assessed through chlorophyll fluorescence measurements. Additionally, the study evaluated oxidative stress indicators, such as lipid peroxidation and the accumulation of reactive oxygen species (ROS), to provide a comprehensive understanding of the species' responses to elevated PM conditions. The study found that elevated PM conditions were closely linked to an increase in oxygenated monoterpenes, which was associated with both oxidative stress and impaired physiological function. These observations emphasize the need for strategic urban tree selection to enhance air quality and suggest that understanding species-specific BVOCs emissions in response to PM is crucial for optimizing urban green spaces for health and environmental benefits.

Sustainable Remediation of Soil and Water Utilizing Arbuscular Mycorrhizal Fungi: A Review

Phytoremediation is recognized as an environmentally friendly technique. However, the low biomass production, high time consumption, and exposure to combined toxic stress from contaminated media weaken the potential of phytoremediation. As a class of plant-beneficial microorganisms, arbuscular mycorrhizal fungi (AMF) can promote plant nutrient uptake, improve plant habitats, and regulate abiotic stresses, and the utilization of AMF to enhance phytoremediation is considered to be an effective way to enhance the remediation efficiency. In this paper, we searched 520 papers published during the period 2000-2023 on the topic of AMF-assisted phytoremediation from the Web of Science core collection database. We analyzed the author co-authorship, country, and keyword co-occurrence clustering by VOSviewer. We summarized the advances in research and proposed prospective studies on AMF-assisted phytoremediation. The bibliometric analyses showed that heavy metal, soil, stress tolerance, and growth promotion were the research hotspots. AMF-plant symbiosis has been used in water and soil in different scenarios for the remediation of heavy metal pollution and organic pollution, among others. The potential mechanisms of pollutant removal in which AMF are directly involved through hyphal exudate binding and stabilization, accumulation in their structures, and nutrient exchange with the host plant are highlighted. In addition, the tolerance strategies of AMF through influencing the subcellular distribution of contaminants as well as chemical form shifts, activation of plant defenses, and induction of differential gene expression in plants are presented. We proposed that future research should screen anaerobic-tolerant AMF strains, examine bacterial interactions with AMF, and utilize AMF for combined pollutant removal to accelerate practical applications.

Greenery planning for urban air pollution control based on biomonitoring potential: Explicit emphasis on foliar accumulation of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs)

In this study, efficiencies of eight indigenous plants of Baishnabghata Patuli Township (BPT), southeast Kolkata, India, were explored as green barrier species and potentials of plant leaves were exploited for biomonitoring of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs). The present work focused on studying PM capturing abilities (539.32-2766.27 μg cm-2) of plants (T. divaricata, N. oleander and B. acuminata being the most efficient species in retaining PM) along with the estimation of foliar contents of PM adhered to leaf surfaces (total sPM (large + coarse): 526.59-2731.76 μg cm-2) and embedded within waxes (total wPM (large + coarse): 8.73-34.51 μg cm-2). SEM imaging used to analyse leaf surfaces affirmed the presence of innate corrugated microstructures as main drivers for particle capture. Accumulation capacities of PAHs of vehicular origin (total index, TI > 4) were compared among the species based on measured concentrations (159.92-393.01 μg g-1) which indicated T. divaricata, P. alba and N. cadamba as highest PAHs accumulators. Specific leaf area (SLA) of plants (71.01-376.79 cm2 g-1), a measure of canopy-atmosphere interface, had great relevance in PAHs diffusion. Relative contribution (>90%) of 4-6 ring PAHs to total carcinogenic equivalent and potential as well as 5-6 ring PAHs to total mutagenic equivalent and potential had also been viewed with respect to benzo[a]pyrene. In-depth analysis of foliar traits and adoption of plant-based ranking strategies (air pollution tolerance index (APTI) and anticipated performance index (API)) provided a rationale for green belting. Each of the naturally selected plant species showed evidences of adaptations during abiotic stress to maximize survival and filtering effects for reductive elimination of ambient PM and PAHs, allowing holistic management of green spaces.

Altitude governs the air pollution tolerance and heavy metal accumulation in plants

Plant response to changing air pollution is a function of various factors including meteorology, type of pollutants, plant species, soil chemistry, and geography. However, the impact of altitude on plant behavior has received little attention to date. A study was therefore conducted to evaluate the impact of altitude on the air pollution tolerance index (APTI), heavy metal accumulation, and deposition in plant species. The results favor the hypothesis of a definite impact of altitude on biochemical and heavy metal accumulation in plants. While a significant decline (p < 0.05) in the relative water content (RWC), APTI, and heavy metal accumulation with increasing altitude was evident in the studied plant species, the behavior of ascorbic acid, leaf extract pH, chlorophyll content, and the particle heavy metal deposition was erratic and did not display any statistically significant differences. The metal accumulation index was in the following order: Ni > Zn > Cu > Pb > Cd > Co. Similarly, the particle heavy metal deposition on the leaf surface (µg/cm2) displayed significant species variability (p < 0.05) and was in the order: Cu (0.303) > Pb (0.301) > Ni (0.269) > Zn (0.241) > Cd (0.044) > Co (0.025). The accumulated heavy metal and RWC showcased a significant positive correlation with the APTI, suggesting the dominant role of RWC in the plant's tolerance against air pollution in an altitudinal gradient. Future studies on the role of micrometeorological conditions in altering APTI may be fruitful in ascertaining these postulations.

Evaluation of air pollution (dust) tolerance index of three desert species Seidlitzia rosmarinus, Haloxylon aphyllum, and Nitraria schoberi under salinity stress

Dust causes adverse effects on the physiological and biochemical properties of plants, and under soil salinity conditions, these effects seem to be intensified, which limits their use in the development of the green belt around or within cities. In the research, the effect of salt (0, 30, and 60 dS m^-1) on air pollution (dust, 0 and 1.5 g m^-2 30 days^-1) tolerance index (APTI), peroxidase activity, and protein content of three desert species Seidlitzia rosmarinus, Haloxylon aphyllum, and Nitraria schoberi was investigated. The results indicated that the use of dust alone did not change the concentration of total chlorophyll in H. aphyllum, while it decreased the concentration of total chlorophyll by 18% in N. schoberi and 21% in S. rosmarinus. Under salt stress conditions, before and after applying dust, the concentration of total chlorophyll decreased in S. rosmarinus and N. schoberi plants, but there was no change in H. aphyllum. The amount of ascorbic acid, peroxide activity, and pH increased significantly with increasing salinity level before and after applying dust. Applying dust alone increased pH value only in N. schoberi and the amount of ascorbic acid and peroxidase in all three plants. Applying dust alone reduced relative water content and APTI only in N. schoberi plant and the amount of protein in all three plants. At salinity level of 60 dS m^-1 and with application of dust treatment, APTI was decreased by 10, 15, and 9% compared to its control before application of dust, respectively, in H. aphyllum, N. schoberi, and S. rosmarinus plants. Therefore, it was found that N. schoberi, which may be used as a bioindicator of air quality, has a lower APTI than S. rosmarinus and H. aphyllum, which may be served as suitable sinks to survive the air pollution (the development of a design on green belt around or within the city), under conditions of simultaneous application of dust and salt.

Protective Effect of Lonicera japonica on PM2.5-Induced Pulmonary Damage in BALB/c Mice via the TGF-β and NF-κB Pathway

This study aimed to assess the protective effect of an extract of Lonicera japonica against particulate-matter (PM)_2.5-induced pulmonary inflammation and fibrosis. The compounds with physiological activity were identified as shanzhiside, secologanoside, loganic acid, chlorogenic acid, secologanic acid, secoxyloganin, quercetin pentoside, and dicaffeoyl quinic acids (DCQA), including 3,4-DCQA, 3,5-DCQA, 4,5-DCQA, and 1,4-DCQA using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS^E). The extract of Lonicera japonica reduced cell death, reactive oxygen species (ROS) production, and inflammation in A549 cells. The extract of Lonicera japonica decreased serum T cells, including CD4⁺ T cells, CD8⁺ T cells, and total T helper 2 (Th2) cells, and immunoglobulins, including immunoglobulin G (IgG) and immunoglobulin E (IgE), in PM_2.5-induced BALB/c mice. The extract of Lonicera japonica protected the pulmonary antioxidant system by regulating superoxide dismutase (SOD) activity, reduced glutathione (GSH) contents, and malondialdehyde (MDA) levels. In addition, it ameliorated mitochondrial function by regulating the production of ROS, mitochondrial membrane potential (MMP), and ATP contents. Moreover, the extract of Lonicera japonica exhibited a protective activity of apoptosis, fibrosis, and matrix metalloproteinases (MMPs) via TGF-β and NF-κB signaling pathways in lung tissues. This study suggests that the extract of Lonicera japonica might be a potential material to improve PM_2.5-induced pulmonary inflammation, apoptosis, and fibrosis.

Bioaccumulation of industrial heavy metals and interactive biochemical effects on two tropical medicinal plant species

Concentrations of heavy metals (Cr, Cu, Fe, Mn, Ni, Pb, and Zn) accumulation were studied in the leaves of two medicinal plant species, namely Holarrhena pubescens and Wrightia tinctoria, from two industrial areas and a control area. Our comparison study revealed that industrialization significantly increased the accumulation of heavy metals in both plant species. A comparison study in control and industrial areas exhibited that heavy metal accumulation was higher in the industrially affected area than in the control area. Heavy metal concentration exceeded the permissible limit recommended by the WHO in both species of two industrial areas. However, both species accumulated the least heavy metal concentration in the control area. Biochemical investigation specifies that in response to heavy metal accumulation, both species increased the activity of hydrogen peroxide (H₂O₂), malondialdehyde content, the activity of enzymatic (superoxide dismutase and peroxidase) and nonenzymatic (ascorbic acid) antioxidant, but decreased the primary (soluble carbohydrate and total protein), secondary metabolites (phenol and flavonoid) content and free radical scavenging (DPPH) activity. This study indicates that industrialization potentially harms medicinal plants by reducing the efficacy of their medicinal property.

Acute effects of ambient nitrogen dioxide exposure on serum biomarkers of nervous system damage in healthy older adults

Ambient nitrogen dioxide (NO₂)-induced adverse health effects have been studied, but documented evidence on neural systems is limited. This study aimed to determine the acute effect of NO₂ exposure on nervous system damage biomarker levels in healthy older adults. Five rounds of follow-up among 34 healthy retired people were scheduled from December 2018 to April 2019 in Xinxiang, China. The real-time NO₂ concentrations were measured using a fixed site monitor. Serum samples were acquired during each round to measure nervous system damage biomarker levels: brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), and S100 calcium-binding protein B (S100B). A linear mixed-effect model was incorporated to analyze the association between short-term NO₂ exposure and serum concentrations of the above-mentioned biomarkers. Stratification analysis based on sex, educational attainment, glutathione S-transferase theta 1 gene (GSTT1) polymorphism, and physical activity intensity was conducted to explore their potential modification effect. The NO₂ concentration ranged from 34.7 to 59.0 µg/m³ during the study period. Acute exposure to ambient NO₂ was significantly associated with elevated serum levels of NfL, PGP9.5, and BDNF. In response to a 10 µg/m³ increase in NO₂ concentration, NfL and PGP9.5 levels increased by 76 % (95 % confidence interval [CI]: 12-140 %) and 54 % (95 % CI: 1-107 %) on the lag0 day, respectively, while BDNF levels increased by 49 % (95 % CI: 2-96 %) at lag4 day. The estimated effect of NO₂ on NSE levels in GSTT1-sufficient participants was significantly higher than that in GSTT1-null participants. Intriguingly, the estimation of NO₂ on PGP9.5 levels in females was significantly higher than that in males. Most two-pollutant models showed robust results, except for O₃, which might have had confounding effects on NO₂-induced BDNF stimulation. In summary, acute exposure to NO₂ was associated with increased levels of serum nervous system damage biomarker levels including NFL, PGP9.5, and BDNF. The present study provided insights into NO₂ exposure-induced adverse neural effects.

Screening of Plant Species Response and Performance for Green Belt Development: Implications for Semi-Urban Ecosystem Restoration

Screened plant species with potential for green belt development can act as eco-sustainable tools for restoring the polluted ecosystem. Eight plant species from two study locations in Ado-Odo, Ota, Ogun State, Nigeria, were examined to identify their air pollution response and performance by deploying two air pollution indices, namely air pollution tolerance index (APTI) and anticipated performance index (API). APTI results identified all screened plants as sensitive species suitable as bio-indicators of air pollution, with Ficus auriculata (2.42) common to the non-industrial location being the most sensitive. API scores categorized Ficus auriculata (56.25%) as a moderate performer, while Syzygium malaccense (75%) and Mangifera indica (75%) were identified as very good performers, suitable for green belt development. The relationship between each biochemical parameter with APTI was investigated using regression analysis and two-way analysis of variance. The model result showed a significant relationship between each biochemical parameter with APTI, and relative water content had the highest influence on APTI (R2 = 0.99436). Both indices (APTI and API) are suitable for screening and recommending native plant species for cultivation in the polluted environment, thus promoting ecological restoration. Hence, Syzygium malaccense, Mangifera indica and Ficus auriculata, respectively, were recommended for green belts design. Further intensive screening to identify tolerant species and best to excellent performer’s trees suitable for restoring the ecosystem is advised.

Variation in Brant's oak (Quercus brantii Lindl.) leaf traits in response to pollution from a gas refinery in semiarid forests of western Iran

Air pollution around refineries and factories is one of the major environmental challenges affecting forest ecosystems' health. Although there have been many studies on Iran's forest ecosystems, the physiological and morphological responses of Brant's oak (Quercus brantii Lindl.) leaves to the pollution of the gas refineries in the semiarid forests have not received much attention. We sampled healthy and mature leaves from four oak stands in different seasons (spring, summer, and autumn of 2019) and at various distances from the gas refinery (1,000, 1,500, 2,000, 2,500, and 10,000 m). The results showed that oak trees in different seasons and at different distances from the refinery had different physiological and morphological leaf trait responses to the pollution source. Oak trees with an air pollution tolerance index value of less than 11 were in a sensitive range to air pollution and can be used to biomonitor air pollution around the gas refinery in Zagros forests. Physiological traits in different seasons and at various distances in comparison with morphological traits (persistent reaction responses) were well distinguished from one another and were more affected by pollution. Oak trees in summer and autumn and at distances up to 2,500 m had rapid reaction responses, including oxidative stress indicators such as electrolyte leakage (EL), hydrogen peroxide, and different enzymatic and nonenzymatic antioxidants such as phenol, flavonoids, catalase, and proline. Because of their high sensitivity to atmospheric pollutant stresses, we recommend that these traits be used for rapid and low-cost environmental monitoring of pollution in different seasons and distances from pollution sources in semiarid ecosystems.

Comprehensive Transcriptome Analysis of Rare Carpinus putoensis Plants under NO2 stress

We evaluated a transcriptome using high-throughput Illumina HiSeq sequencing and related it to the morphology, leaf anatomy, and physiological parameters of Carpinus putoensis putoensis under NO₂ stress. The molecular mechanism of the C. putoensis NO₂ stress response was evaluated using sequencing data. NO₂ stress adversely affected the morphology, leaf anatomy, and total peroxidase (POD) activity. Through RNA-seq analysis, we used NCBI to compare the transcripts with nine databases and obtained their functional annotations. We annotated up to 2255 million clean Illumina paired-end RNA-seq reads, and 250,200 unigene sequences were assembled based on the resulting transcriptome data. More than 89% of the C. putoensis transcripts were functionally annotated. Under NO₂ stress, 1119 genes were upregulated and 1240 were downregulated. According to the KEGG pathway and GO analyses, photosynthesis, chloroplasts, plastids, and the stimulus response are related to NO₂ stress. Additionally, NO₂ stress changed the expression of POD families, and the HPL2, HPL1, and POD genes exhibited high expression. The transcriptome analysis of C. putoensis leaves under NO₂ stress supplies a reference for studying the molecular mechanism of C. putoensis resistance to NO₂ stress. The given transcriptome data represent a valuable resource for studies on plant genes, which will contribute towards genome annotations during future genome projects.

Ozone Response of Leaf Physiological and Stomatal Characteristics in Brassica juncea L. at Supraoptimal Temperatures

Plants are affected by the features of their surrounding environment, such as climate change and air pollution caused by anthropogenic activities. In particular, agricultural production is highly sensitive to environmental characteristics. Since no environmental factor is independent, the interactive effects of these factors on plants are essential for agricultural production. In this context, the interactive effects of ozone (O3) and supraoptimal temperatures remain unclear. Here, we investigated the physiological and stomatal characteristics of leaf mustard (Brassica juncea L.) in the presence of charcoal-filtered (target concentration, 10 ppb) and elevated (target concentration, 120 ppb) O3 concentrations and/or optimal (22/20 °C day/night) and supraoptimal temperatures (27/25 °C). Regarding physiological characteristics, the maximum rate of electron transport and triose phosphate use significantly decreased in the presence of elevated O3 at a supraoptimal temperature (OT conditions) compared with those in the presence of elevated O3 at an optimal temperature (O conditions). Total chlorophyll content was also significantly affected by supraoptimal temperature and elevated O3. The chlorophyll a/b ratio significantly reduced under OT conditions compared to C condition at 7 days after the beginning of exposure (DAE). Regarding stomatal characteristics, there was no significant difference in stomatal pore area between O and OT conditions, but stomatal density under OT conditions was significantly increased compared with that under O conditions. At 14 DAE, the levels of superoxide (O2-), which is a reactive oxygen species, were significantly increased under OT conditions compared with those under O conditions. Furthermore, leaf weight was significantly reduced under OT conditions compared with that under O conditions. Collectively, these results indicate that temperature is a key driver of the O3 response of B. juncea via changes in leaf physiological and stomatal characteristics.

Evaluation of the Importance of Some East Asian Tree Species for Refinement of Air Quality by Estimating Air Pollution Tolerance Index, Anticipated Performance Index, and Air Pollutant Uptake

Potentials of tree species as biofilters depend on appropriate selection based on their tolerance to air pollution, which is usually evaluated by the air pollution tolerance index (APTI) and anticipated performance index (API). Thus, these index values need as a means of scientific understanding to assess the role of urban trees for better greenspace planning/management to mitigate impacts of gaseous air pollution such as ozone (O3) and sulfur dioxide (SO2). O3 exposure to Chionanthus retusus, Pinus densiflora, and Ginkgo biloba showed higher stomatal O3 flux than the others, finally resulting in both favoring stomatal movement and maintaining carbon fixation. In contrast, despite the whole tree enhanced SO2 uptake under excess SO2 exposure, the carbon assimilation capacity was only found in Taxus cuspidata and Zelkova serrata as a consequence of no stomatal sluggishness. On the basis of API, P. densiflora and Prunus × yedoensis were good performers for developing greenspace, while Z. serrata and G. biloba were moderate performers; however, C. retusus and T. cuspidata were estimated to be poor and very poor performers, respectively, for reducing the air quality injury caused by air pollutants. The present study suggests that an integration of both APTI and API based on stomatal absorption flux is needed for selecting sound tree-species in greenspace planning/construction to control gaseous air pollutions.