Ozone-induced foliar injury in saplings of Psidium guajava 'Paluma' in São Paulo, Brazil

Eugenia uniflora L.: potential uses as a bioactive plant

ABSTRACT: Natural products extracted from plants have always played an important role in the discovery of bioactive substances. This work carried out a review of the literature on the bioactive activities of Eugenia uniflora L. (Surinam cherries), as a potential plant in the various uses, be it medicinal, antimicrobial, antioxidant, insecticide and protective. In the literature, studies were found to confirm the antibacterial activity of E. uniflora leaves extract on Streptococcus, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The presence of antioxidant compounds as total phenolics, such as anthocyanins and flavonoids, induction in the protection of plants by phytoalexins, as well as insecticidal and anthelmintic effects by the use of the extract of the E. uniflora tree. Although these different potential biotics of E. uniflora have already been reported, further studies are still needed on the use of natural products extracted from E. uniflora for employment for different purposes.

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.

Responses of a tropical tree species to ozone: visible leaf injury, growth, and lipid peroxidation

The Brazilian native tree species Astronium graveolens was indicated as sensitive to ozone in a fumigation experiment. Thus, the objective of this study was to evaluate how sensitive A. graveolens is to ozone under realistic conditions in the field. Eighteen saplings were exposed to ozone in a contaminated area and in a greenhouse with filtered air during two exposure periods of approximately 63 days each (March-May 2012 and September-October 2012). Leaf injury was analyzed by means of its incidence and severity, the leaf injury index (LII) and the progression of leaf abscission. These variables were monitored weekly, whereas growth and lipid peroxidation were monitored monthly. Plants exposed to ozone showed significant growth decrease and visible leaf injury increase, but lipid peroxidation and leaf abscission remained unchanged. These results indicated that plants subjected to ozone possibly diverted energy from growth to the production of antioxidants necessary to cope with ozone-induced oxidative stress.

DO3SE model applicability and O3 flux performance compared to AOT40 for an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma')

Phytotoxic ozone (O3) levels have been recorded in the Metropolitan Region of São Paulo (MRSP). Flux-based critical levels for O3 through stomata have been adopted for some northern hemisphere species, showing better accuracy than with accumulated ozone exposure above a threshold of 40 ppb (AOT40). In Brazil, critical levels for vegetation protection against O3 adverse effects do not exist. The study aimed to investigate the applicability of O3 deposition model (Deposition of Ozone for Stomatal Exchange (DO3SE)) to an O3-sensitive tropical tree species (Psidium guajava L. 'Paluma') under the MRSP environmental conditions, which are very unstable, and to assess the performance of O3 flux and AOT40 in relation to O3-induced leaf injuries. Stomatal conductance (g s) parameterization for 'Paluma' was carried out and used to calculate different rate thresholds (from 0 to 5 nmol O3 m(-2) projected leaf area (PLA) s(-1)) for the phytotoxic ozone dose (POD). The model performance was assessed through the relationship between the measured and modeled g sto. Leaf injuries were analyzed and associated with POD and AOT40. The model performance was satisfactory and significant (R (2) = 0.56; P < 0.0001; root-mean-square error (RMSE) = 116). As already expected, high AOT40 values did not result in high POD values. Although high POD values do not always account for more injuries, POD0 showed better performance than did AOT40 and other different rate thresholds for POD. Further investigation is necessary to improve our model and also to check if there is a critical level of ozone in which leaf injuries arise. The conclusion is that the DO3SE model for 'Paluma' is applicable in the MRSP as well as in temperate regions and may contribute to future directives.

The guava tree as bioindicator during the process of fuel replacement of an oil refinery

This study was performed to verify whether the exchange of the fuel used in the boilers of a crude oil refinery located in Cubatão (SE Brazil) would result in alterations on gas exchange, growth and leaf injuries in saplings of Psidium guajava 'Paluma'. The purpose of the refinery was to reduce the SO2 emission, but using natural gas as fuel could increase the concentrations of O3 precursors in the atmosphere. Thus a biomonitoring was performed with a native species sensitive to O3. The plants were exposed in five areas (CM1, CM5, CEPEMA, Centro, and RP) at different distances to the refinery, both before and after the fuel exchange. We performed six exposures under environmental conditions, with length of ca. 90 days each. With the utilization of natural gas, the saplings presented reductions in carbon assimilation rate under saturating light conditions (Asat, μmolCO2m(-2)s(-1)) and the stomatal conductance (gs, molH2Om(-2)s(-1)), and increase in height, number of leaves, and dry mass of leaves and shoots. There were also reductions in root dry mass and in the root/shoot ratio. The saplings also presented O3-induced leaf injuries. The responses of P. guajava 'Paluma' were altered after the fuel exchange as a result of a new combination of pollutants in the atmosphere. The fuel exchange has not resulted in environmental benefit to the surrounding forest; it has only altered the contamination profile of the region.

The efficiency of tobacco Bel-W3 and native species for ozone biomonitoring in subtropical climate, as revealed by histo-cytochemical techniques

We aimed to verify whether hydrogen peroxide (H(2)O(2)) accumulation and cell death are detected early in three bioindicators of ozone (O(3)), Nicotiana tabacum 'Bel-W3', Ipomoea nil 'Scarlet O'Hara' and Psidium guajava 'Paluma', and whether environmental factors also affect those microscopic markers. The three species were exposed to chronic levels of O(3) in a subtropical area and a histo-cytochemical technique that combines 3,3'-diaminobenzidine (DAB) with Evans blue staining was used in the assessments. The three species accumulated H(2)O(2), but a positive correlation with O(3) concentration was only observed in N. tabacum. A positive correlation between O(3) and cellular death was also observed in N. tabacum. In I. nil and P. guajava, environmental factors were responsible for symptoms at the microscopic level, especially in P. guajava. We conclude that the most appropriate and least appropriate bioindicator plant for O(3) monitoring in the subtropics are N. tabacum 'Bel-W3' and P. guajava 'Paluma', respectively.

Gas exchange, antioxidants and foliar injuries in saplings of a tropical woody species exposed to ozone

Ozone (O(3)) reaches phytotoxical concentrations in the tropics, but the sensitivity of tropical plant species to O(3) remains unknown. Visible foliar injuries, carbon assimilation (A(sat)), stomatal conductance, superoxide dismutase enzyme (SOD) activity and ascorbic acid concentration (AA) were evaluated in different-aged leaves of Psidium guajava 'Paluma' saplings. We hypothesized that the old leaves are less capable of combating the stress induced by O(3) and hence exhibit more severe leaf injuries. Three O(3) exposure experiments were performed with 'Paluma' saplings in sites with high O(3) concentration and also under filtered air conditions. The exposure experiments corresponding to the seasons spring/2006, summer and autumn/2007. The decrease of A(sat) was greater in old leaves of saplings exposed to O(3), except in the second experiment, when the AA concentrations were more pronounced than in the other experiments. In second experiment, O(3) uptake was similar to that of the first experiment, but the injuries were less severe, probably due to the high AA concentrations. It was not possible to identify a pattern of superoxide dismutase enzyme (SOD) activity due to the high variability in the results from O(3) exposed and reference saplings. O(3) uptake/A(sat) was higher in leaves exhibiting greater injury, suggesting that decrease in A(sat) may have been the main feature associated with the visible foliar symptons.

Psidium guajava as a bioaccumulator of nickel around an oil refinery, southern Brazil

To evaluate the potential of Psidium guajava as a biological accumulator of air pollutants, saplings were exposed at nine sites receiving atmospheric emissions from an oil refinery (five within, four outside the industrial area) and another reference site located at the Federal University of Rio Grande do Sul, 27 km from the refinery. Exposures lasted about 3 months each, coincided with the seasons, and totaled five exposures between 2005 and 2006. The following parameters were evaluated: dry weight of leaves, stems, and roots, leaf area, rate of relative height increase, Ni and S contents, maximum assimilation rate, and carboxylation efficiency invivo. P. guajava was found to be an efficient accumulator of Ni, since highly significant differences were observed (P<0.001) between sites within the industrial area and the reference site for all periods of exposure and a significant negative correlation between distance from emission source and Ni content. The S content showed significant differences (P<0.05) only at sites within the industrial area for two exposures. The dry weight, leaf area, rate of relative height increase, maximum assimilation rate, and carboxylation efficiency did not present significant differences for any period of exposure. In view of the above, we conclude that P. guajava is a good bioaccumulator for Ni.

Anthocyanins and tannins in ozone-fumigated guava trees

Psidium guajava "Paluma", a tropical tree species, is known to be an efficient ozone indicator in tropical countries. When exposed to ozone, this species displays a characteristic leaf injury identified by inter-veinal red stippling on adaxial leaf surfaces. Following 30 days of three ozone treatments consisting of carbon filtered air (CF - AOT40=17 ppb h), ambient non-filtered air (NF - AOT40=542 ppb h) and ambient non-filtered air+40 ppb ozone (NF+O(3) - AOT40=7802 ppb h), the amounts of residual anthocyanins and tannins present in 10 P. guajava ("Paluma") saplings were quantified. Higher amounts of anthocyanins were found in the NF+O(3) treatment (1.6%) when compared to the CF (0.97%) and NF (1.30%) (p<0.05), and of total tannins in the NF+O(3) treatment (0.16%) compared to the CF (0.14%). Condensed tannins showed the same tendency as enhanced amounts. Regression analyses using amounts of tannins and anthocyanins, AOT40 and the leaf injury index (LII), showed a correlation between the leaf injury index and quantities of anthocyanins and total tannins. These results are in accordance with the association between the incidence of red-stippled leaves and ozone polluted environments.