Presence of leaves and use of IBA in adventitious rooting, chlorophyll fluorescence, and root ontogeny of 'Fepagro C 13' and 'Trifoliata' cuttings / Presença de folhas e uso de AIB no enraizamento adventício, fluorescência da clorofila e ontogenia radicular em estacas de 'Fepagro C 13' e 'Trifoliata'

Cutting is proposed as an alternative method for the propagation of citrus rootstocks to obtain clonal material especially in varieties with a low rate of polyembryony and possibly reduce the seedling formation period. The aim of this study was to examine the influence of leaves and the application of indolebutyric acid (IBA) on adventitious rooting and chlorophyll fluorescence as well as to characterize root ontogeny in 'Fepagro C 13' and 'Trifoliata' citrus rootstock cuttings. Semi-hardwood cuttings were collected in December 2018 and subjected to the following treatments: presence or absence of leaves, with or without application of IBA (4000 mg L-1). Over 92 days in a greenhouse environment, leaf abscission percentage, cutting mortality, rooting percentage, and number of roots per cutting were evaluated. Additionally, initial (Fo), maximum (Fm), and variable (Fv) chlorophyll fluorescence, photochemical efficiency (Fv/Fm), and Fv/Fo ratio were analyzed. Tissue samples from the base of the cutting were collected for the anatomical study. The presence of leaves on 'Fepagro C 13' and 'Trifoliata' cuttings is essential for adventitious rooting. The use of auxin influences the photochemical efficiency of leaves on the cuttings. In 'Trifoliata' cuttings, adventitious roots originate from the vascular cambium.(AU)

A estaquia é proposta como método alternativo para a propagação de porta-enxertos de citros, visando a garantia de obtenção de material clonal, especialmente em variedades com baixa taxa poliembriônica, e uma possível redução no período para a obtenção das mudas. O objetivo deste estudo foi avaliar a influência das folhas e da aplicação de ácido indolbutírico (AIB) sobre o enraizamento adventício, fluorescência da clorofila e caracterizar a ontogenia radicular em estacas dos porta-enxertos citrangeiro 'Fepagro C 13', e 'Trifoliata'. Estacas semilenhosas foram coletadas em dezembro de 2018 e submetidas aos tratamentos: presença ou ausência de folhas com aplicação ou não de AIB (4000 mg L-1). Ao longo de 92 dias em casa de vegetação foram avaliados os percentuais de abscisão foliar, mortalidade de estacas, percentual de enraizamento e número de raízes por estaca. Também os dados da fluorescência inicial (Fo), máxima (Fm) e variável (Fv) da clorofila, a eficiência fotoquímica (Fv/Fm) e a razão Fv/Fo foram avaliados. Amostras de tecido da base da estaca foram coletadas para a realização do estudo anatômico. A presença das folhas nas estacas de 'Fepagro C 13' e 'Trifoliata' é essencial para o enraizamento adventício. O uso de auxina influencia a eficiência fotoquímica nas folhas das estacas. Em estacas de 'Trifoliata' as raízes adventícias originam-se a partir do câmbio vascular.(AU)

Nitrogen source and pH interact and modulate lipase secretion in a non-clinical strain of Candida parapsilosis

Lipases (E.C. 3.1.1.3) are serine-hydrolases, and act on long chain fatty acid ester bonds. They exhibit specific and enantioselective activities, which are desirable for many industrial applications. This study aimed at screening and optimizing the production of lipases by wild yeast strains from a variety of substrates, as well as characterizing the enzyme. An initial selection was made in oxygenated oil-supplemented minimum medium, and the enzymatic activity of the supernatant was tested over p-nitrophenyl palmitate. One-hundred and twenty-four yeast strains from different substrates were tested, and twenty-three showed significantly higher lipolytic activity (p<0.01). One yeast in particular, QU110, showed best lipase production and therefore was selected for the optimization and characterization processes. This yeast exhibits enzyme secretion in initial pH 6.0, with olive oil and tryptone as carbon and nitrogen sources, respectively. There was a strong interaction between nitrogen source and initial pH, and pH 9.0seems to inhibit enzyme secretion. The crude enzyme (cell-free supernatant) shows stability in surfactants and n-hexane, but not in ethanol or methanol. A Response Surface Model was created and optimal enzyme activity conditions were observed at 36°C and pH 8.0. The lipase is appropriate for transesterification reactions, as the enzyme is more stable in strong apolar solvents than moderately apolar ones. Also, secretion by pH was not reported elsewhere, which should be further investigated and contribute for other yeast bioprocesses as well.