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.
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.
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•We assessed changes in pro-oxidant/oxidant balance in trees from Atlantic Forest.•Pioneer trees are more tolerant against the oxidative stress than non-pioneer trees.•Non-pioneer trees presented higher levels of ROS and a less effective antioxidant metabolism.•Both functional groups maintained similar pro-oxidant/oxidant balance despite the ROS and antioxidant levels.
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.
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.
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•The exchange of power generation system would reduce oxidative stress to vegetation.•Tibouchina pulchra would be a promising biosensor plant by changing its redox ability.•The antioxidant level during the experimental period varied in response to pollutants.•The gain in environmental quality was not achieved.
•The effects of ozone can be detected through a group of cellular makers.•Structural changes caused by oxidative stress occur prior to the visible symptoms.•Specific cellular markers of ozone might ...indicate distinct physiological processes.•Ozone stress prompts accelerated cell senescence and HR-like reactions.
Ozone (O3) is an oxidative pollutant that causes visible foliar symptoms in sensitive plants. Importantly, cellular markers induced by physiological alterations, including oxidative burst (OB), hypersensitive response-like (HR-like) reactions, and accelerated cell senescence (ACS), precede these symptoms. Because little is known about the effects of ozone in tropical environments, we aimed to identify these cellular markers in Nicotiana tabacum, Ipomoea nil and Psidium guajava growing in an urban area of tropical Sao Paulo, Brazil, and describe the specific physiological alterations that trigger the development of visible symptoms. Cell wall wart-like protrusions, an OB cellular marker, and swelling of thylakoids and mitochondrial membranes, as well as accumulation of plastoglobuli, all markers of ACS, were cell markers common to all species studied. Cellular markers indicating HR-like reaction, as observed in the asymptomatic leaves of N. tabacum and I. nil, are precursors of future development of necrotic areas, featuring the visible symptoms. On the other hand, the main cause of visible symptoms in P. guajava appeared to be the accumulation of phenolic compounds in the mesophyll tissue, an ACS marker. Based on this line of evidence, these bioindicator plants growing in a tropical environment show the damaging effects of O3 pollution, even before visible symptoms develop. Moreover, this damage can be detected through a distinct group of cellular markers.
•Tibouchina pulchra is a Brazilian tree species tolerant to air pollution.•The plants did not show any visible injury.•Microscopic changes associated with oxidative stress were found in leaf ...tissues.•The microscopic response intensity was different during dry and wet seasons.•Air pollution and climatic oscillations were possible inducers of microscopic changes.
Tibouchina pulchra (Cham.) Cogn., a pioneer tree species commonly found in the Atlantic Rain Forest in southeast Brazil, proved to be a promising biosensor species for indicating the potential effects of air pollution on this type of forest. This study aimed to investigate whether the present levels of nitrogen oxides, sulfur oxides, ozone and particulate matter in industrial and urban areas in the Cubatão region induce structural and ultrastructural changes in this species, to explore the synergy between air pollutants and the effects of other environmental stressors as contributors to microscopic symptoms and to verify whether these changes are seasonally dependent. The field study consisted of exposing potted saplings of T. pulchra in three sites around the petrochemical industry (industrial area), in downtown Cubatão (urban area) and in a site far from the industrial emissions (reference area). An experimental study using open top chambers (OTC) with filtered air and non-filtered air was also carried out to confirm the field results. Four exposure periods of 12 weeks were conducted during the field and the OTC experiments, covering wet and dry periods. The effects were more pronounced in plants exposed in the industrial areas during the dry period, which were confirmed by OTC experiments. Crystal density variations were linearly explained by decreases in NO2, SO2 and the sum of all hourly concentrations of ozone (SUM00), as well as increases in PM10, relative humidity and rainfall. Variations in lipid peroxidation correlated positively with air temperature and SUM00. Tannins and starch grains decreased. Collapsed and sinuous cell walls, dense cytoplasm, invagination of plasma membranes and vacuome were the main effects observed at the structural level. Occurrence of pectic warts, alterations in chloroplasts and numerous vesicles close to the cell walls were the main ultrastructural effects detected. These results confirmed that pollutants and environmental variables acted synergistically to induce oxidative stress in this species, enhancing our understanding of the bioindicator potential of T. pulchra for monitoring complex mixtures of air pollutants in the tropics.
Native plants from the Brazilian savanna (the Cerrado) are exposed to agrochemicals widely used in the crops around them. However, there are few studies on the toxicity of herbicides on the ...vegetation of this biome. Thus, the objective of this study was to identify and establish morphological and physiological indicators of glyphosate effects on two native Cerrado plants. Independent experiments were carried out for the species
Pouteria torta
and
Alibertia edulis
, exposing them to four glyphosate doses (0, 200, 400, and 800 g a.e. ha
−1
). The photosynthetic process and the morphoanatomy in developing leaf (F1) and full-expanded leaf (F3), at different days after herbicide application (DAA) were evaluated. Physiological indicators of glyphosate toxicity in
P. torta
, such as decreases in photosynthetic rate, in chlorophylls, and in the efficiency of photosystem II were identified. Increments of carotenoids and heat dissipation (NPQ) were common responses to glyphosate in both plants. Reduction in photochemical efficiency in
A. edulis
was more pronounced in older leaves. Multivariate analysis confirmed the physiological data and the contrasting response of plants to the herbicide. The damages on the foliar surface in
P. torta
are anatomical indicators of glyphosate toxicity. The susceptibility of
P. torta
makes it a phyto-indicator for the passive biomonitoring of the glyphosate effects on Cerrado vegetation. There were no changes in the micromorphology of the leaf surface in
A. edulis
. This plant showed tolerance to the glyphosate through morphological barriers in leaves, which reduced the absorption of the herbicide.
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 6
h 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.
O ozônio troposférico causa necroses foliares em Nicotiana tabacum. Cultivares de tabaco são muito utilizadas como bioindicadoras de ozônio, em programas de biomonitoramento da qualidade do ar. ...Dentre elas destacam-se as cultivares Bel-W3 (sensível) e Bel-B (tolerante). Este estudo teve como objetivo verificar se as duas cultivares apresentam variações na estrutura foliar que possam ajudar a explicar a diferença na sensibilidade ao ozônio que ambas apresentam. Em plantas que cresceram em ambiente isento de poluentes aéreos foram coletadas folhas do terceiro nó e que foram processadas segundo técnicas usuais empregadas em anatomia vegetal. Realizaram-se análises quantitativas e qualitativas dos tecidos foliares. A cultivar Bel-W3, quando comparada à Bel-B, apresentou menor densidade estomática na superfície abaxial e maior espessura do mesofilo. Qualitativamente as células de ambas cultivares mostraram aspecto sadio, com os vacúolos ocupando praticamente todo o volume celular. A cultivar sensível apresentou visivelmente mais espaços intercelulares, câmaras estomáticas maiores e estômatos ligeiramente salientes em ambas superfícies foliares. Tais características, que facilitam a entrada e a difusão dos poluentes na folha, podem explicar, do ponto de vista estrutural, a maior sensibilidade da cultivar Bel-W3.
Tropospheric ozone produces symptoms such as leaf injury in Nicotiana tabacum. Tobacco cultivars are often used as ozone indicators in air-quality biomonitoring programs. Bel-W3 (sensitive) and Bel-B (tolerant) cultivars are better known. The aim of this study was to verify if the two cultivars show variation in leaf structure that may help to explain differences in ozone sensitivity. Expanded leaves from plants growing in pollutant-free air were collected, processed according to the usual techniques of plant anatomy, and analyzed quantitatively and qualitatively. The sensitive cultivar showed lower stomatal density on the abaxial leaf surface and thicker mesophyll cells when compared to the tolerant cultivar. Qualitatively speaking, both cultivars had healthy cells with unaltered vacuoles. In the sensitive cultivar, we could see more intercellular spaces, larger substomatal chambers and slightly prominent stomata on both leaf surfaces. From a structural view point, these features explain why cultivar Bel-W3 is more sensitive.
O ozônio troposférico causa necroses foliares em Nicotiana tabacum. Cultivares de tabaco são muito utilizadas como bioindicadoras de ozônio, em programas de biomonitoramento da qualidade do ar. ...Dentre elas destacam-se as cultivares Bel-W3 (sensível) e Bel-B (tolerante). Este estudo teve como objetivo verificar se as duas cultivares apresentam variações na estrutura foliar que possam ajudar a explicar a diferença na sensibilidade ao ozônio que ambas apresentam. Em plantas que cresceram em ambiente isento de poluentes aéreos foram coletadas folhas do terceiro nó e que foram processadas segundo técnicas usuais empregadas em anatomia vegetal. Realizaram-se análises quantitativas e qualitativas dos tecidos foliares. A cultivar Bel-W3, quando comparada à Bel-B, apresentou menor densidade estomática na superfície abaxial e maior espessura do mesofilo. Qualitativamente as células de ambas cultivares mostraram aspecto sadio, com os vacúolos ocupando praticamente todo o volume celular. A cultivar sensível apresentou visivelmente mais espaços intercelulares, câmaras estomáticas maiores e estômatos ligeiramente salientes em ambas superfícies foliares. Tais características, que facilitam a entrada e a difusão dos poluentes na folha, podem explicar, do ponto de vista estrutural, a maior sensibilidade da cultivar Bel-W3.
Tropospheric ozone produces symptoms such as leaf injury in Nicotiana tabacum. Tobacco cultivars are often used as ozone indicators in air-quality biomonitoring programs. Bel-W3 (sensitive) and Bel-B (tolerant) cultivars are better known. The aim of this study was to verify if the two cultivars show variation in leaf structure that may help to explain differences in ozone sensitivity. Expanded leaves from plants growing in pollutant-free air were collected, processed according to the usual techniques of plant anatomy, and analyzed quantitatively and qualitatively. The sensitive cultivar showed lower stomatal density on the abaxial leaf surface and thicker mesophyll cells when compared to the tolerant cultivar. Qualitatively speaking, both cultivars had healthy cells with unaltered vacuoles. In the sensitive cultivar, we could see more intercellular spaces, larger substomatal chambers and slightly prominent stomata on both leaf surfaces. From a structural view point, these features explain why cultivar Bel-W3 is more sensitive.
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