RESUMO
Water deficit is a major environmental constraint on crop productivity and performance and nitric oxide (NO) is an important signaling molecule associated with many biochemical and physiological processes in plants under stressful conditions. This study aims to test the hypothesis that leaf spraying of S-nitrosoglutathione (GSNO), an NO donor, improves the antioxidant defense in both roots and leaves of sugarcane plants under water deficit, with positive consequences for photosynthesis. In addition, the roles of key photosynthetic enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) in maintaining CO2 assimilation of GSNO-sprayed plants under water deficit were evaluated. Sugarcane plants were sprayed with water or GSNO 100 µM and subjected to water deficit, by adding polyethylene glycol (PEG-8000) to the nutrient solution. Sugarcane plants supplied with GSNO presented increases in the activity of antioxidant enzymes such as superoxide dismutase in leaves and catalase in roots, indicating higher antioxidant capacity under water deficit. Such adjustments induced by GSNO were sufficient to prevent oxidative damage in both organs and were associated with better leaf water status. As a consequence, GSNO spraying alleviated the negative impact of water deficit on stomatal conductance and photosynthetic rates, with plants also showing increases in Rubisco activity under water deficit.
Assuntos
Doadores de Óxido Nítrico/farmacologia , Fosfoenolpiruvato Carboxilase/efeitos dos fármacos , Ribulose-Bifosfato Carboxilase/efeitos dos fármacos , S-Nitrosoglutationa/farmacologia , Saccharum/efeitos dos fármacos , Antioxidantes/metabolismo , Catalase/metabolismo , Desidratação , Oxirredução , Fosfoenolpiruvato Carboxilase/metabolismo , Fotossíntese/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/enzimologia , Folhas de Planta/fisiologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/enzimologia , Raízes de Plantas/fisiologia , Estômatos de Plantas/efeitos dos fármacos , Estômatos de Plantas/enzimologia , Estômatos de Plantas/fisiologia , Transpiração Vegetal/efeitos dos fármacos , Ribulose-Bifosfato Carboxilase/metabolismo , Saccharum/enzimologia , Saccharum/fisiologia , Superóxido Dismutase/metabolismo , Água/fisiologiaRESUMO
The current levels of surface ozone (O3) are high enough to negatively affect trees in large regions of São Paulo State, southeastern Brazil, where standards for the protection of vegetation against the adverse effects of O3 do not exist. We evaluated three O3 metrics - phytotoxic ozone dose (POD), accumulated ozone exposure over the threshold of 40 ppb h (AOT40), and the sum of all hourly average concentrations (SUM00) - for the Brazilian native tropical tree species Astronium graveolens Jacq. We used the DO3SE (Deposition of Ozone for Stomatal Exchange) model and calculated PODY for different thresholds (from 0 to 6 mmol O3 m(-2) PLA s(-1)), evaluating the model's performance through the relationship between measured and modelled conductance. The response parameters were: visible foliar injury, considered as incidence (% injured plants), severity (% injured leaves in relation to the number of leaves on injured plants), and leaf abscission. The model performance was suitable and significant (R(2) = 0.58; p < 0.001). POD0 was better correlated to incidence and leaf abscission, and SUM00 was better correlated to severity. The highest values of O3 concentration-based metrics (AOT40 and SUM00) did not coincide with those of POD0. Further investigation may improve the model and contribute to the proposition of a national standard for the protection of native species.
Assuntos
Poluentes Atmosféricos/análise , Anacardiaceae/efeitos dos fármacos , Monitoramento Ambiental/métodos , Florestas , Ozônio/análise , Folhas de Planta/efeitos dos fármacos , Árvores/efeitos dos fármacos , Poluentes Atmosféricos/efeitos adversos , Anacardiaceae/crescimento & desenvolvimento , Brasil , Relação Dose-Resposta a Droga , Modelos Biológicos , Ozônio/efeitos adversos , Doenças das Plantas/induzido quimicamente , Folhas de Planta/crescimento & desenvolvimento , Estômatos de Plantas , Árvores/crescimento & desenvolvimentoRESUMO
This study summarizes the first effort to search for bioindicator tree species and respective potential biomarkers for future assessment of potential mixed pollution effects on the highly diverse Atlantic Forest in SE-Brazil. Leaves of the three most abundant species inventoried in a phytosociological survey (Croton floribundus, Piptadenia gonoacantha and Astronium graveolens) were collected in four forest remnants during winter and summer (2012). Their potential bioindicator attributes were highlighted using a screening of morphological, chemical and biochemical markers. The leaf surface structure and/or epicuticular wax composition pointed the accumulator properties of C. floribundus and P. gonoacantha. C. floribundus is a candidate for assessing potential accumulation of Cu, Cd, Mn, Ni, S and Zn. P. gonoacantha is a candidate to monitor polycyclic aromatic hydrocarbons. Increased levels of secondary metabolites and decreased antioxidant capacity in leaves of A. graveolens may support its value as a bioindicator for oxidative pollutants by visible dark stipplings.
Assuntos
Poluentes Atmosféricos/análise , Antioxidantes/análise , Monitoramento Ambiental/métodos , Árvores/química , Árvores/crescimento & desenvolvimento , Poluentes Atmosféricos/efeitos adversos , Antioxidantes/metabolismo , Biodiversidade , Biomarcadores/análise , Biomarcadores/metabolismo , Brasil , Folhas de Planta/química , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Floresta Úmida , Estações do Ano , Especificidade da Espécie , Árvores/metabolismoRESUMO
In the Metropolitan Region of Campinas (MRC), Brazil, high levels of primary pollutants contribute to ozone (O3) formation. However, little is known regarding the O3 effects in the tropics. Objectives in this study were to characterize the present levels of O3 pollution and to evaluate the relevance of current concentration-based indices for assessing the phytotoxic potential of O3. Changes in O3 concentrations and precursors at 5 monitoring stations within towns of MRC were analyzed. The daily O3 profile was typical for urban sites and showed little yearly variation. Given the permanently foliated forest canopy, yearly rather than seasonal O3 indices were thus more appropriate for estimating the effective ozone dose. With yearly SUM00, SUM60 and AOT40 of 156, 16 and 14 ppm h and confirmed by evidence of O3 injury in foliage, oxidative stress in the MRC has reached levels high enough to affect trees from the Atlantic Semi-deciduous Forest.
Assuntos
Poluentes Atmosféricos/toxicidade , Ozônio/toxicidade , Árvores/efeitos dos fármacos , Poluentes Atmosféricos/análise , Brasil , Monitoramento Ambiental , Ozônio/análise , Árvores/fisiologiaRESUMO
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.