Potential of the Trad-MCN assay applied with inflorescences of Tradescantia pallida 'Purpurea' for evaluating air contamination by naphthalene.

The aims of this study were to determine clastogenic responses of Tradescantia pallida cv. Purpurea to naphthalene (NAPH) by means of the bioassay Trad-MCN with inflorescences of T. pallida cv. Purpurea and to verify if this assay might be an indicator of the potential risk imposed in a workplace, where solid insecticide containing NAPH is usually applied. The clastogenic potential of NAPH was assessed by using static and dynamic experimental systems. In both systems, increased micronucleus frequencies were observed in inflorescences submitted to increasing concentrations of solid or gaseous NAPH. The evident clastogenicity verified in inflorescences exposed experimentally to 25-50 mg m(-3) of NAPH during 6h points to a narrow threshold of plant sensitivity, indicating risks under lower NAPH levels than the standards established by OSHA and therefore revealing its suitability for biomonitoring purposes. However, the clastogenic risk should be carefully investigated by other monitoring methods if human health is taken into consideration.

Efficiency of biomonitoring methods applying tropical bioindicator plants for assessing the phytoxicity of the air pollutants in SE, Brazil.

In the tropical region, the greatest challenge of the biomonitoring approach is to establish linear relationships between biomarkers measured in plants and pollutant concentrations, since the bioindicator responses can be intensified or restricted by climatic variations. In southeastern Brazil, there are two regions affected by air pollution, where the Atlantic Forest remains and should be preserved. Consequently, both areas have been monitored by biomonitoring procedures using standardized and tropical plants. The industrial complex settled in Cubatão is one of the world's most famous examples of environmental pollution and degradation, with consequent decline of the Atlantic Forest. An oil refinery is among the most polluting industries in the Cubatão region. The other region is located in the Metropolitan Region of Campinas (MRC). The MRC has been affected by high levels of air pollutants originated from road traffic and is responsible for over 80% of CO, NOx, and hydrocarbon emissions and develops industrial activities that emit about 70% of the particulate matter present in the region. Both regions are distinguished by the climate, despite the fact that they are only about 130 km far from each other. Several studies carried out by our group in these regions aimed to establish the best native tree species and respective potential biomarkers for future assessment of pollution effects on tropical Forests. We present a critical review about the efficiency of native species compared to standardized bioindicator plants considering antioxidant defense system, nutrient accumulation, and microscopic aspects when exposed to atmospheric pollutants and climate.

Oxidant-antioxidant balance and tolerance against oxidative stress in pioneer and non-pioneer tree species from the remaining Atlantic Forest.

The extensive land occupation in Southeast Brazil has resulted in climatic disturbances and environmental contamination by air pollutants, threatening the Atlantic forest remnants that still exist in that region. Based on previous results, we assumed that pioneer tree species are potentially more tolerant against environmental oxidative stress than non-pioneer tree species from that Brazilian biome. We also assumed that reactive oxygen species (ROS) are accumulated in higher proportions in leaves of non-pioneer trees, resulting in changes in the oxidant-antioxidant balance and in more severe oxidative damage at the cellular level than in the leaves of pioneer trees. We tested these hypotheses by establishing the relationship between oxidants (ROS), changes in key antioxidants (among enzymatic and non-enzymatic compounds) and in a lipid peroxidation derivative in their leaves, as well as between ROS accumulation and oscillations in environmental stressors, thus permitting to discuss comparatively for the first time the oxidant-antioxidant balance and the tolerance capacity of tree species of the Atlantic Forest in SE Brazil. We confirmed that the non-pioneer tree species accumulated higher amounts of superoxide and hydrogen peroxide in palisade parenchyma and epidermis, showing a less effective antioxidant metabolism than the pioneer species. However, the non-pioneer species showed differing capacities to compensate the oxidative stress in both years of study, which appeared to be associated with the level of ROS accumulation, which was evidently higher in 2015 than in 2016. We also applied exploratory multivariate statistics, which revealed that the oscillations in these biochemical leaf responses in both functional groups coincided with the oscillations in both climatic conditions and air pollutants, seemingly showing that they had acclimated to the stressful oxidative environment observed and may perpetuate in the disturbed forest remnants located in SE Brazil.

Assessing redox potential of a native tree from the Brazilian Atlantic Rainforest: a successful evaluation of oxidative stress associated to a new power generation source of an oil refinery.

The antioxidant responses in saplings of Tibouchina pulchra (a native tree from the Brazilian Atlantic Rainforest) exposed around an oil refinery in the city of Cubatão (SE Brazil), varied during the exchange of its power generation source, from boilers fueled with oil to a thermoelectric fueled with natural gas. The redox potential changed in response to an interaction of air pollution and meteorological parameters, indicating that the pro-oxidant/antioxidant balance was not reached after the exchange of the power generation system. The gain in environmental quality in the region was not achieved as expected due the technological modernization, at least relative to oxidative stressors. These conclusions were based on results of analyses of enzymatic antioxidants: superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR); non-enzymatic antioxidants: reduced, oxidized and total ascorbic acid (AsA, DHA, totAA) and glutathione (GSH, GSSG, totG), their redox state (AsA/totAA and GSH/totG) and an indicator of lipid peroxidation (MDA). We also applied exploratory multivariate statistics in order to verify if the temporal sequence of changes in the plant redox capacity coincided with changes in the profile of air pollution, climatic conditions or with their interactions and if the environmental benefits that would supposedly be promoted by the mentioned exchange of power generation system were achieved in the region.

Temporal dynamics of the cellular events in tobacco leaves exposed in São Paulo, Brazil, indicate oxidative stress by ozone.

Nicotiana tabacum 'Bel-W3' is widely used as an ozone bioindicator species, showing typical necrosis preceded by microscopic markers of oxidative stress. This study aimed to follow the development of symptoms in tobacco exposed in São Paulo highlighting the temporal dynamics of the cellular events. Leaves with and without necrosis were processed according to standard techniques for anatomical analyses. Leaves from the site with higher SUM00 presented thinner palisade parenchyma, fewer layers of spongy parenchyma, higher stomatal density, clusters of vessel elements in the midrib, erosion of cuticular waxes and stomatal damage. The sequence of microscopic events from the third day of exposure were condensation of the cytoplasm in parenchyma tissue, sinuosity of anticlinal walls, pectinaceous cell wall protrusions, chromatin condensation and changes in chlorophyll autofluorescence. On the 14th day of exposure, these events finally led to cell death in the palisade parenchyma and necrosis on the leaf. The markers observed indicated oxidative stress caused by ozone.