Patricia Bulbovas

Leaf antioxidant fluctuations and growth responses in saplings of Caesalpinia echinata Lam. (brazilwood) under an urban stressing environment.

We intended to establish how efficient the leaf antioxidant responses of C. echinata are against oxidative environmental conditions observed in an urban environment and their relations to growth and biomass parameters. Plants were grown for 15 months in four sites: Congonhas and Pinheiros, affected by pollutants from vehicular emissions; Ibirapuera, affected by high O(3) concentrations; and a greenhouse with filtered air. Fifteen plants were quarterly removed from each site for analysis of antioxidants, growth and biomass. Plants growing in polluted sites showed alterations in their antioxidants. They were shorter, had thicker stems and produced less leaf biomass than plants maintained under filtered air. The fluctuations in the levels of antioxidants were significantly influenced by combined effects of climatic and pollution variables. The higher were the antioxidant responses and the concentrations of pollutant markers of air contamination in each site the slower were the growth and biomass production.

Variação sazonal em antioxidantes em folhas de plantas jovens de Caesalpinia echinata Lam. (pau-brasil)

The urban environmental factors generate conditions of oxidative stress in plants. Cellular antioxidants, such as ascorbic acid (AA),thiols (Ti), peroxidases (POD) and superoxide dismutase (SOD) are induced to different levels depending on their capacity to tolerate stressing conditions. In the first part of this study we determined the profile of these defenses in leaves of different ages of young plants of C. echinata. The levels of antioxidants were similar in all leaves analyzed, independently of the age. Secondly, we evaluated the same antioxidants and glutathione (GSH) in 130 young plants kept in a greenhouse with constant monitoring of temperature, relative humidity and irradiance during 18 months, in order to establish the seasonal variations occurring in response to climatic factors. During this period, leaf antioxidants were analyzed every three months. In general, AA concentrations and POD activity in C. echinata were higher than the levels reported for other tropical tree species. Seasonal variations were observed. GSH concentration and POD activity were significantly influenced by temperature and SOD by temperature and humidity.

Photosynthetic Responses of Tropical Trees to Short-Term Exposure to Ozone

Saplings of the tropical trees Tibouchina pulchra (Cham.) Cogn., Caesalpinia echinata Lam., and Psidium guajava L. cv. Paluma were exposed in open-top chambers with charcoal filtered air and measurements of gas exchange and chlorophyll fluorescence were made before (t1) and after exposure to non-filtered air plus O3 (t2), simulating 6-h peaks of O3 similar to those observed in São Paulo city (SE Brazil, reaching an AOT40 of 641 nmol mol−1). After the fumigation, the net photosynthetic rate, stomatal conductance, transpiration rate, and Fv/Fm were reduced (p<0.05) for the three species. C. echinata was the most sensitive species and P. guajava cv. Paluma the most resistant.

Ryegrass cv. Lema and guava cv. Paluma biomonitoring suitability for estimating nutritional contamination risks under seasonal climate in Southeastern Brazil

The risks posed by nutrient deposition due to air pollution on ecosystems and their respective services to human beings can be appropriately estimated by bioindicator plants when they are well acclimated to the study region environmental conditions. This assumption encouraged us to comparatively evaluate the accumulation potential of ryegrass cv. Lema and guava cv. Paluma macro and micronutrients. We also indicated the most appropriate species for biomonitoring nutrient contamination risks in tropical areas of Southeastern Brazil, which are characterized by marked dry and wet seasons and complex mixtures of air pollutants from different sources (industries, vehicle traffic and agriculture). The study was conducted in 14 sites with different neighboring land uses, within the Metropolitan Region of Campinas, central-eastern region of São Paulo State. The exposure experiments with ryegrass and guava were consecutively repeated 40 (28 days each) and 12 (84 days each) times, respectively, from Oct/2010 to Sept/2013. Macro and micronutrients were analyzed and background concentrations and enrichment ratios (ER) were estimated to classify the contamination risk within the study region. Significantly higher ER suggested that ryegrass were the most appropriate accumulator species for N, S, Mg, Fe, Mn, Cu and Zn deposition and guava for K, Ca, P and B deposition. Based on these biomonitoring adjustments, we concluded that the nutrient deposition was spatially homogeneous in the study area, but clear seasonality in the contamination risk by nutritional inputs was evidenced. Significantly higher contamination risk by S, Fe, K and B occurred during the dry season and enhanced contamination risk by Mn, Cu and Zn were highlighted during the wet season. Distinctly high contamination risk was estimated for S, Fe and Mn in several exposure experiments.

Biochemical leaf traits as indicators of tolerance potential in tree species from the Brazilian Atlantic Forest against oxidative environmental stressors

The tolerance potential against the oxidative injury in native plants from forest ecosystems affected by environmental stressors depends on how efficiently they keep their pro-oxidant/antioxidant balance. Great variations in plant tolerance are expected, highlighting the higher relevance of measuring biochemical leaf trait indicators of oxidative injury in species with similar functions in the forest than in single species. The use of this functional approach seems very useful in the Brazilian Atlantic Forest because it still holds high plant diversity and was the focus of this study. We aimed at determining the tolerance potential of tree species from the Atlantic Forest remnants in SE Brazil against multiple oxidative environmental stressors. We assumed that pioneer tree species are more tolerant against oxidative stress than non-pioneer tree species and that their tolerance potential vary spatially in response to distinct combined effects of oxidative environmental stressors. The study was carried out in three Atlantic Forest remnants, which differ in physiognomy, species composition, climatic characteristics and air pollution exposure. Leaves of three pioneer and three non-pioneer species were collected from each forest remnant during wet (January 2015) and dry periods (June 2015), for analyses of non-enzymatic and enzymatic antioxidants and oxidative injury indicators. Both hypotheses were confirmed. The pioneer tree species displayed biochemical leaf traits (e.g. high levels of ascorbic acid, glutathione and carotenoids and lower lipid peroxidation) that indicate their higher potential tolerance against oxidative environmental stressors than non-pioneer species. The biochemical leaf traits of both successional groups of species varied between the forest remnants, in response to a linear combination of oxidative environmental stressors, from natural (relative humidity and temperature) and anthropogenic sources (ozone and nitrogen dioxide).

Avaliação da sensibilidade de plantas jovens de quiabo (Abelmoschus esculentus (L.) Moench. - Malvaceae) ao ozônio

A sensibilidade de Abelmoschus esculentus ao ozonio (O3) foi determinada em plantas expostas por quatro dias, seis horas/dia, ao ar filtrado (AF) e ao AF enriquecido com 80 ppb de O3 (AF+O3), em câmaras de fumigacao, analisando-se sintomas foliares visiveis e alteracoes nas trocas gasosas e em antioxidantes. Avaliaram-se os sintomas foliares diariamente e as trocas gasosas e antioxidantes (acido ascorbico e superoxido dismutase) ao fim do experimento. Todas as plantas em AF+O3 apresentaram sintomas foliares, caracterizados por pontuacoes avermelhadas na superficie adaxial, entre as nervuras. Em media, o indice de injuria foliar foi de 15% e a severidade de 62%. Fotossintese liquida, condutância estomatica, transpiracao, concentracao de acido ascorbico e atividade da superoxido dismutase foram reduzidas significativamente nestas plantas, em comparacao com as mantidas sob ar filtrado. Os resultados sugerem que Abelmoschus esculentus e sensivel ao O3, apresentando baixos niveis de defesas antioxidativas e disturbios fisiologicos.