The Air Pollution Tolerance index (APTI) of six plants located within Ikpoba Okha gas flaring site in Oredo Local Government Area of Edo State, Nigeria during wet and dry seasons were assessed. Plant samples for this research work were randomly collected from the vicinity of the flaring site. Six (6) sample of each plant was used for laboratory analysis. The plant parameters assessed include relative water content (RWC), the ascorbic acid content (AAC), total leaf chlorophyll (TLC) and pH extract of the leaves and were used to compute the Air pollution tolerance indices (APTI). Based on the analyzed result, the RWC in Drypetes leonensis, Ficus exasperata Vahl, Chromolaena odorata (Linn) and Gmelina arborea Roxb. ex Smith   species in dry season were higher than those in wet season. Icacina tricantha showed a relatively high level of acidity when compared to others. A. boonei De Wild has the highest ascorbic acid content in the leaves in both seasons. The highest level of chlorophyll contents was recorded in the dry season with Drypetes leonensis having the highest, followed by Icacina trichantha. There was no statistically significant difference in pH and total chlorophyll contents between samples collected in wet and dry season; however, there were significant difference observed in ascorbic acid and RWC in both seasons. APTI in wet and dry season showed a statistically significant difference. This study recommends planting of tolerant species that can acts as bio-indicators especially in gas flaring stations in Nigeria.

Environmental pollution consists of different types of pollutants in air, soil, and water. Due to the fact that plants can respond to environmental pollution, they can be used as bio-indicators for environmental monitoring. Air pollution in areas with oil and gas refineries nearby is an important problem. This study aims to survey the effects of gas refinery air pollutants on Conocarpus erectus so that it can be used for air-pollution monitoring. For this purpose, physiological indicators such as proline, protein, and malondealdehyde content as well as Air Pollution Tolerance Index (APTI value) have been used to evaluate these effects. Based on the obtained results, Conocarpus erectus in polluted area showed increased pH, protein, proline, malondealdehyde, and ascorbic acid contents while carotenoid quantity, total leaf chlorophyll content, and relative water content were decreased in comparison to the control plants. Therefore, it proves that air pollution affects the plant.

Air Pollution Tolerance Index (APTI) is an important tool to screen out plants, based on their tolerance or sensitivity level to different air pollutants. The present study has been conducted to evaluate APTI of four different plant species around polluted and unpolluted industrial site in Sfax, Tunisia. In order to determine the susceptibility level of the selected plant species, it has used four physiological and biochemical parameters like leaf relative water content, ascorbic acid content, chlorophyll content, and leaf pH to compute the APTI values. The results of the study reveal that among the four studied plant species, Olea europaea (APTI = 20.09) and Phoenix dactylifera (APTI = 17.10) are the most tolerant species, whereas Ficus carica (APTI = 8.87) and Morus alba (APTI = 7.49) are the most sensitive ones. The present study suggests that the most tolerant species, i.e., olive and date palm, can be planted in polluted sites for both air pollution abatement and aesthetic improvement. While, the sensitive species, namely common figand white Mulberry, help indicating air pollution and should be utilized as bio-indicators.

The main intent of the current research was to appraise if combined application of hydrogen sulfide (H₂S, 0.2 mM) and silicon (Si 2.0 mM) could improve tolerance of tomato plants to arsenic (As as sodium hydrogen arsenate heptahydrate, 0.2 mM) stress. Plant growth, chlorophylls (Chl), PSII maximum efficiency (Fv/Fm), H₂S concentration and L-cysteine desulfhydrase activity were found to be suppressed, but leaf and root As, leaf proline content, phytochelatins, malondialdehyde (MDA) and H₂O₂ as well as the activity of lipoxygenase (LOX) increased under As stress. H₂S and Si supplied together or alone enhanced the concentrations of key antioxidant biomolecules such as ascorbic acid, and reduced glutathione and the activities of key antioxidant system enzymes including catalase (CAT), superoxide dismutase (SOD), dehydroascorbate reductase (DHAR), glutathione reductase (GR), and glutathione S-transferase (GST). In comparison with individual application of H₂S or Si, the joint supplementation of both had better effect in improving growth and key biochemical processes, and reducing tissue As content, suggesting a putative collaborative role of both molecules in improving tolerance to As-toxicity in tomato plants.

Increasing rates of commercialization and industrialization have led to the comprehensive evaluation of toxic effects of microplastics on crop plants. However, research on the impact of functionalized polystyrene nanoplastics on the toxicity of heavy metals remains limited. This study investigated the effects of polystyrene, carboxy-modified polystyrene, and amino-modified polystyrene on lead (Pb) toxicity in dandelion seedlings. The results showed that carboxy -modified polystyrene with a negative charge absorbed more Pb²⁺ than polystyrene and amino-modified polystyrene, and their maximum adsorption amounts were 5.328, 0.247, and 0.153 μg g⁻¹, respectively. The hydroponic experiment demonstrated that single amino-modified polystyrene was more toxic to dandelion seedlings than polystyrene and carboxy-modified polystyrene. The presence of Pb²⁺ was found to increase antioxidant enzymes (superoxide dismutase and catalase) and non-antioxidant enzymes (glutathione and ascorbic acid) activities in response to excessive reactive oxygen species in dandelion leaves and roots treated with polystyrene and carboxy-modified polystyrene, while it did not change much when amino-modified polystyrene was added. Interestingly, compared with single Pb²⁺, the addition of amino-modified polystyrene with positive charges induced an obvious decrease in the above parameters; however, they declined slightly in the treatments with polystyrene and carboxy-modified polystyrene despite a stronger adsorption capacity for Pb²⁺. Similarly, the bioactive compounds, including flavonoids, polyphenols, and polysaccharides in dandelion, showed a scavenging effect on O₂⁻ and H₂O₂, thereby inhibiting the accumulation and reducing medicinal properties. This study found that the effects of microplastics on the uptake, distribution, and toxicity of heavy metals depended on the nanoparticle surface charge.

Biofumigation is an effective, non-chemical method to control soil-borne pests and diseases and to maximize crop yield. We studied the responses of soil bacterial and fungal communities, the soil’s nutritional state and strawberry yield, when the soil was biofumigated each year for five consecutive years using fresh chicken manure (BioFum). BioFum significantly increased the soil’s NH4+-N, NO3−-N, available P and K and organic matter. Fusarium spp. and Phytophthora spp. which are known to cause plant disease, were significantly decreased after BioFum. In addition, Biofum increased the soil’s temperature, enhanced chlorophyll levels in the leaves of strawberry plants, and the soluble sugar and ascorbic acid content in strawberry fruit. We used high-throughput gene sequencing to monitor changes in the soil’s bacterial and fungal communities. Although BioFum significantly decreased the diversity of these communities, it increased the relative abundance of some biological control agents in the phylum Actinobacteria and the genera Pseudomonas, Bacillus and Chaetomium. An increase in these biological control agents would reduce the incidence of soil-borne pathogens and plant disease. Although strawberry marketable yield using BioFum was higher in the first three years, the decline in the final two years could be due to the accumulation of P and K which may have delayed flowering and fruiting. Methods to overcome yield losses using BioFum need to be developed in the future. Our research, however, showed that BioFum enhanced soil fertility, reduced the presence of soil pathogens, increased the relative abundance of beneficial bacteria and fungi and improved strawberry quality. Unlike chemical soil treatments that can cause pest and disease resistance when used continuously over many years, our multi-year research program on BioFum showed that this treatment provided significant benefits to the soil, plant and strawberry fruit.

Numerous studies have documented the negative effects of ozone (O₃) on tree species in growing season, however, little is done in non-growing season. Three evergreen tree species, Phoebe bournei (Hemsl.) Yang (P. bournei), Machilus pauhoi Kanehira (M. pauhoi) and Taxus chinensis (Pilger) Rehd (T. chinensis), were exposed to non-filtered air, 100 nmol mol⁻¹ O₃ air (E1) and 150 nmol mol⁻¹ O₃ air (E2) in open-top chambers in subtropical China. In the entire period of experiment, O₃ fumigation decreased net photosynthesis rate (Pn) through stomatal limitation during the transition period from growing to non-growing season (TGN), and through non-stomatal limitation during the period of non-growing season (NGS) in all species tested. Meanwhile, O₃ fumigation reduced and delayed the resilience of Pn in all species tested during the transition period from non-growing to growing season (TNG). O₃ fumigation significantly decreased chlorophyll contents during NGS, whereas no obvious injury symptoms were observed till the end of experiment. O₃ fumigation induced increases in levels of malondialdehyde, superoxide dismutase, total phenolics and reduced ascorbic acid, and changes in four plant endogenous hormones as well in all species tested during NGS. During NGS, E1 and E2 reduced Pn by an average of 80.11% in P. bournei, 94.56% in M. pauhoi and 12.57% in T. chinensis, indicating that the O₃ sensitivity was in an order of M. pauhoi > P. bournei > T. chinensis. Overall, O₃ fumigation inhibited carbon fixation in all species tested during NGS. Furthermore, O₃-induced physiological activities also consumed the dry matter. All these suggested that elevated O₃, which is likely to come true during NGS in the future, will adversely affect the accumulation of dry matter and the resilience of Pn during TNG in evergreen tree species, and further inhibit their growth and development in the upcoming growing season.

Particulate air pollution being recognized to be responsible for short and long term health effects, regulations for particulate matter with an aerodynamic diameter less than 2.5 (PM2.5) are more and more restrictive. PM2.5 regulation is based on mass without taking into account PM2.5 composition that drives toxicity. Measurement of the oxidative potential (OP) of PM could be an additional PM indicator that would encompass the PM components involved in oxidative stress, the main mechanism of PM toxicity. We compared different methods to evaluate the intrinsic oxidative potential of PM2.5 sampled in Paris and their ability to reflect the oxidative and inflammatory response in bronchial epithelial cells used as relevant target organ cells. The dithiothreitol depletion assay, the antioxidant (ascorbic acid and glutathione) depletion assay (OPAO), the plasmid scission assay and the dichlorofluorescein (DCFH) oxidation assay used to characterize the OP of PM2.5 (10–100 μg/mL) provided positive results of different magnitude with all the PM2.5 samples used with significant correlation with different metals such as Cu and Zn as well as total polyaromatic hydrocarbons and the soluble organic fraction. The OPAO assay showed the best correlation with the production of intracellular reactive oxygen species by NCI-H292 cell line assessed by DCFH oxidation and with the expression of anti-oxidant genes (superoxide dismutase 2, heme-oxygenase-1) as well as the proinflammatory response (Interleukin 6) when exposed from 1 to 10 μg/cm2. The OPAO assay appears as the most prone to predict the biological effect driven by PM2.5 and related to oxidative stress.

Oxidative potential (OP) of particulate matter (PM) − defined as the capacity of PM to oxidize target molecules generating reactive oxygen species (ROS) − has been proposed as a more health relevant metric than PM mass. In this study two cell-free methods were used to assess the OP of PM filters collected at an urban site and to evaluate correlation with PM mass and PM composition.Among the different assays existing, two inexpensive and user-friendly methods were used both based on spectrophotometric measurements of depletion rate of target reagents oxidized by redox-active species present in PM. One assay measures the consumption of dithiothreitol (OPDTT) and the other the ascorbate (OPAA).Although both assays respond to the same redox-active species, i.e., quinones and transition metals, no correlations were found between OPDTT and OPAA responses to compounds standard solutions as well as to ambient samples. When expressed in relation to air volume, OPDTT m−3 strongly correlates with PM2.5 mass whereas no correlation was found for OPAA m−3 with PM2.5. When expressed on mass basis, both OPDTT μg−1 and OPAA μg−1 show a strong dependence on the sample composition, with higher OP for summer samples. OPDTT m−3 were highly correlated with the determined metals (Cu, Zn, Cr, Fe, Ni, Mn) whereas OPAA m−3 showed only moderate correlation with Cu and Mn.Thus, the two assays could potentially provide complementary information on oxidative potential characteristic of PM. Consequently, the combination of the two approaches can strengthen each other in giving insight into the contribution of chemical composition to oxidative properties of PM, which can subsequently be used to study health effects.

A combination of in vitro and in vivo studies on tomato (Lycopersicon esculentum Mill. cv. Triton) revealed that environmentally-relevant levels of ozone (O3) pollution adversely affected pollen germination, germ tube growth and pollen-stigma interactions – pollen originating from plants raised in charcoal-Purafil® filtered air (CFA) exhibited reduced germ tube development on the stigma of plants exposed to environmentally-relevant levels of O3. The O3-induced decline in in vivo pollen viability was reflected in increased numbers of non-fertilized and fertilized non-viable ovules in immature fruit. Negative effects of O3 on fertilization occurred regardless of the timing of exposure, with reductions in ovule viability evident in O3 × CFA and CFA × O3 crossed plants. This suggests O3-induced reductions in fertilization were associated with reduced pollen viability and/or ovule development. Fruit born on trusses independently exposed to 100 nmol mol−1 O3 (10 h d−1) from flowering exhibited a decline in seed number and this was reflected in a marked decline in the weight and size of individual fruit – a clear demonstration of the direct consequence of the effects of the pollutant on reproductive processes. Ozone exposure also resulted in shifts in the starch and ascorbic acid (Vitamin C) content of fruit that were consistent with accelerated ripening. The findings of this study draw attention to the need for greater consideration of, and possibly the adoption of weightings for the direct impacts of O3, and potentially other gaseous pollutants, on reproductive biology during ‘risk assessment’ exercises.