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The plant antifungal isoflavone genistein is metabolized by Armillaria mellea Vahl to give non-fungitoxic products
No full textEVIDENCE FOR A FORMA SPECIALIS SPECIFIC EFFECT OF ANTIFUNGAL FLAVONOLS IN FUSARIUM OXYSPORUM
No full textMetabolic changes associated to the unblocking of adventitious root formation in aged, rooting-recalcitrant cuttings of Eucalyptus gunnii Hook. f. (Myrtaceae)
No full textIn many tree species, the ability to produce adventitious roots is limited by specific changes related to the physiology of
reproduction and ageing. In spite of its ecological significance, little is known about the physiological mechanisms determining
the irreversibility of these non-rooting states in some species. In this study, we performed natural and hormone-induced
rooting of stem cuttings from mature individuals of rooting-recalcitrant Eucalyptus gunnii in order to characterize the poorly
known metabolic changes associated to the formation of adventitious roots in a rooting-recalcitrant tree species. Stem cuttings,
either with or without an apical meristem, were put in a rooting greenhouse after having been treated with two different
synthetic auxins, indole-3-butyric acid and 1-naphthaleneacetic acid. During the rooting processes changes in the secondary
metabolism of the cutting stem tissue were observed and analyzed through different chromatographic techniques. Rooting of
cuttings in E. gunnii proved to be hastened by the accumulation in tissues of methyl gallate. Its natural metabolization and
disappearance during the long period of cutting stay in the rooting benches restored the adventive rooting ability. In the same
period, a concomitant accumulation in cutting tissues of quercetin-like flavonoids was observed. Rooting was enhanced by
the addition of indole-3-butyric acid and 1-naphthaleneacetic acid, although rooting of cuttings with apical meristem was not
influenced by hormonal treatments. Seasonal conditions had no effect on the percentage of rooted cuttings, although rooting
took 1 month longer in the autumn/winter trial. In general, auxinic treatments did not affect the production of cutting new
leaves but did favor the initial differentiation of new root tissue. Rooting was blocked by the presence in the tissues of the
inhibitor methyl gallate, the degradation of which allowed the rooting processes to take place. Metabolization and disappearance
of this rooting inhibitor was associated with the production and further glycosylation of flavonols. Our results suggest
that the switch between the metabolic pathways of gallic acid and shikimic acid and other flavonoid precursors is a crucial
step in the process leading to the formation of adventitious roots in aged E. gunnii cuttings
Fungitoxic phenols from carnation (Dianthus caryophyllus) effective against Fusarium oxysporum f. sp. dianthi
No full textThe phenol compositions of two cultivars of carnation (Dianthus caryophyllus) namely "Gloriana" and "Roland", which are partially and highly resistant, respectively, to Fusarium oxysporum f. sp. dianthi have been investigated with the aim of determining if endogenous phenols could have an anti-fungal effect against the pathogen. Analyses were performed on healthy and F. oxysporum-inoculated in vitro tissues, and on in vivo plants. Two benzoic acid derivatives, protocatechuic acid (3,4-dihydroxybenzoic acid) and vanillic acid (4-hydroxy-3-methoxybenzoic acid), were found within healthy and inoculated tissues of both cultivars, together with the flavonol glycoside peltatoside (3-[6-O-(alpha-L-arabinopyranosyl)-beta-D-glucopyranosyl] quercetin). These molecules proved to be only slightly inhibitory towards the pathogen. 2,6-Dimethoxybenzoic acid was detected in small amounts only in the inoculated cultivar "Gloriana", while the highly resistant cultivar "Roland" showed the presence of the flavone datiscetin (3,5,7,2'-tetrahydroxyflavone). The latter compound exhibited an appreciable fungitoxic activity towards F. oxysporum f. sp. dianthi
Does catechin make the mediterranean palm tree chamaerops humilis l. An unsuitable host for rhynchophorus ferrugineus?
No full textThe Red Palm Weevil (RPW), Rhynchophorus ferrugineus (Coleoptera: Curculionidae), is an insect pest native to Southeast Asia, which has become the major threat to palms in the Mediterranean Basin, mainly due to the movement of infested planting material. In case of infestation, the exotic weevil is difficult to control effectively and host plants often die. Chamaerops humilis (Arecales: Arecaceae) palms are reported as resistant to RPW, but little is known about the chemical basis of this resistance and about the identity of the endogenous metabolites that may be involved. In the present study, we focused on the potential toxic effect of catechin against RPW larvae. In laboratory bioassays, purified catechin from C. humilis leaves was provided to two-and five-week old RPW larvae at three different concentrations. We found that catechin can impair the survival of RPW, causing toxicity at concentrations as low as 0.03 mg g-1. Larval mortality was concentra-tion-dependent, and furthermore larval age influenced the effect of catechin, older larvae being more susceptible than younger ones. The observed toxicity of catechin on RPW larvae agrees with the hypothesis that this compound contributes to C. humilis being an unsuitable host for this insect pest
Purification and properties of a new S-adenosyl-L-methionine:flavonoid 4′-O-methyltransferase from carnation (Dianthus caryophyllus L.)
No full textA new enzyme, S-adenosyl-l-methionine:flavonoid 4'-O-methyltransferase (EC 2.1.1.-) (F 4'-OMT), has been purified 1 399-fold from the tissues of carnation (Dianthus caryophyllus L). The enzyme, with a molecular mass of 43-45 kDa and a pI of 4.15, specifically methylates the hydroxy substituent in 4'-position of the flavones, flavanones and isoflavones in the presence of S-adenosyl-l-methionine. A high affinity for the flavone kaempferol was observed (Km = 1.7 micro m; Vmax = 95.2 micro mol.min-1.mg-1), while other 4'-hydroxylated flavonoids proved likewise to be suitable substrates. Enzyme activity had no apparent Mg++ requirement but was inhibited by SH-group reagents. The optimum pH value for F 4'-OMT activity was found to be around neutrality. Kinetic analysis of the enzyme bi-substrate reaction indicates a Ping-Pong mechanism and excludes the formation of a ternary complex. The F 4'-OMT activity was increased, in both in vitro and in vivo carnation tissues, by the inoculation with Fusarium oxysporum f. sp. dianthi. The enzyme did not display activity towards hydroxycinnamic acid derivatives, some of which are involved, as methylated monolignols, in lignin biosynthesis; the role of this enzyme could be therefore mainly defensive, rather than structural, although its precise function still needs to be ascertained
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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