Marcos Nopper Alves

Chromosomal and morphological studies of diploid and polyploid cytotypes of Stevia rebaudiana (Bertoni) Bertoni (Eupatorieae, Asteraceae)

In this study, we examined the chromosome number and some morphological features of strains of Stevia rebaudiana. The chromosomes were analyzed during mitosis and diakinesis, and the tetrad normality and pollen viability were also assessed. In addition, stomata and pollen were measured and some plant features were studied morphometrically. All of the strains had 2n = 22, except for two, which had 2n = 33 and 2n = 44. Pairing at diakinesis was n = 11II for all of the diploid strains, whereas the triploid and tetraploid strains had n = 11III and n = 11IV, respectively. Triploid and tetraploid plants had a lower tetrad normality rate than the diploids. All of the strains had inviable pollen. Thus, the higher the ploidy number, the greater the size of the pollen and the stomata, and the lower their number per unit area. The triploid strain produced the shortest plants and the lowest number of inflorescences, whereas the tetraploid strain had the largest leaves. Analysis of variance revealed highly significant differences among the strains, with a positive correlation between the level of ploidy and all of the morphological features examined.

Unravelling remote sensing signatures of plants contaminated with gasoline and diesel: An approach using the red edge spectral feature

Pipeline systems used to transport petroleum products represent a potential source of soil pollution worldwide. The design of new techniques that may improve current monitoring of pipeline leakage is imperative. This paper assesses the remote detection of small leakages of liquid hydrocarbons indirectly, through the analysis of spectral features of contaminated plants. Leaf and canopy spectra of healthy plants were compared to spectra of plants contaminated with diesel and gasoline, at increasing rates of soil contamination. Contamination effects were observed both visually in the field and thorough changes in the spectral reflectance patterns of vegetation. Results indicate that the remote detection of small volumes of gasoline and diesel contaminations is feasible based on the red edge analysis of leaf and canopy spectra of plants. Brachiaria grass ranks as a favourable choice to be used as an indicator of HCs leakages along pipelines.

Chemical composition and antimicrobial activity of the essential oil from the leaves and flowers of Aloysia gratissima

Volatile oils from leaves and flowers of Aloysia gratissima were investigated for their chemical composition and antimicrobial activity against the bacteria Bacilus subtilis, Staphylococcus aureus, Salmonella choleraesuis, Pseudomonas aeruginosa, Streptococcus pneumoniae and the Candida albicans yeast. The minimum inhibitory concentrations (MIC) of the oils were determined by the micro-dilution method, while the chemical composition was determined by GC-MS (gas chromatography mass spectrometry). The fresh leaves and inflorescence were subjected to hydrodistillation for 120 min using a Clevenger-type apparatus, and the essential oil was tested against microorganisms. High concentrations of sesquiterpenes were observed for the inflorescence, and monoterpenes were observed for the leaves. The main compounds of the inflorescence essential oil were E-caryophyllene, germacrene B, guaiol and bulnesol, while in the leaves the main compounds were trans-pinocamphone, trans-pinocarveyl acetate, and guaiol. The essential oil from the leaves showed an effect against P. aeruginosa and S. pneumonia, and the essential oil of the inflorescence showed an effect against P. aeruginosa, S. pneumonia, and Candida albicans.

Correlation between the variations of clay content in soils and sediments and the spectral behavior of superjacent vegetation using spectir hyperspectral images

This work approaches geobotany in southeastern Brazil within terrains comprising Forested Savannas, Gallery and Riparian Atlantic forests developed over fluvial-lacustrine sediments and rocks. The notion was to test the ability of SpecTIR V-S hyperspectral imagery (357 VNIR-SWIR channels; spatial resolution of 1m) to identify the variation of clay content in soils/sediments based on spectral patters yielded by the overlying vegetation. Samples were collected for granulometric analysis in the center of 30 plots with 20x20m each. Vegetation was grouped by floristic similarity. Tailored spectral indices were applied to the SpecTIR V-S data. Different indices were needed to extract parameters of the physical environment from varying vegetation. Results indicate that the physiognomies investigated are influenced differently by clay content in soils and that the vegetation also responds distinctly due to subtle textural variations in the subjacent terrains.