1,720,974 research outputs found
Morphological changes induced by heavy metals in dandelion (Taraxacum officinale Web.) growing on mine soils.
No full textPurpose Heavy metal accumulation produces significant
physiological and biochemical responses in vascular plants.
Plants growing on abandoned mine sites are of particular
interest, since they are genetically tolerant to high metal
concentrations. In this work, we examined the effect of heavy metals (HMs) on the morphology of T. officinale growing in pots with mine soils, with the following objectives: (1) to determine the evolution of HM concentration in leaves and roots over 3 years of cultivation; (2) to highlight possible
damage at anatomical and cytological level.
Materials and methods Wild specimens of Taraxacum
officinale Web., with their soil clod, were gathered from three
sites with different contamination levels by heavy metals (Cd,
Cr, Cu, Fe, Pb, Zn) in the abandoned Imperina Valley mine
(Northeast Italy). A control plant was also gathered from a
non-contaminated site nearby. Plants were cultivated in pots at the botanical garden of the University of Florence (HBF), and appeared macroscopically not affected by toxic signals (reduced growth, leaf necrosis) possibly induced by soil HM
concentration. Leaves and roots taken at the same growing
season were observed by light microscopy and transmission
electron microscopy. Results and discussion Light microscopy observations show a clear difference in the cellular organisation of noncontaminated and contaminated samples. The unpolluted samples present a well-organised palisade tissue and spongy photosynthetic parenchyma. Samples from contaminated sites, instead, present a palisade parenchyma less organised, and a reduction of leaf thickness proportional to HM concentration.
The poor structural organisations, and the reduced
foliar thickness of the contaminated plants, are related to soil
contamination. Differences in root micromorphology concern
the cortical parenchyma. Moreover, all the samples examined
present mycorrhiza. Ultrastructure observations of the parenchyma cells show mitochondrial structure alteration, with
lacking or reduced cristae of the internal membrane at increasing metal content. Instead, chloroplast organisation does not present significant differences, particularly in number and compartmentalization of thylakoids.
Conclusions Although macromorphology does not present
evidence of phytotoxicity, the recorded observations of the
micromorphological characteristics of leaves and roots, show
a suffering state of the plants, strictly related to HM content.
Leaching reduced partly the HM content of the soil, therefore
decreasing their phytotoxic effect. A gradual restoration of
leaf organisation suggests that somewhat resilience occurred
in plants. Moreover, the presence of stress-tolerant mycorrhizal fungi could contribute to reduce metal toxicity
The role of secreting structures position on the leaf volatile organic compounds of Hypericum androsaemum.
No full textUltrastructural evaluation of the glandular indumentum in selected Lamiaceae species
No full textThis work is part of a two-year research project (IRIS identification - project 2014-PDF-0363) focused on the plant heritage preserved at the Ghirardi Botanic Garden of Toscolano Maderno (Bs), which have a long tradition in the study and conservation of medicinal species.
We presented the results of an extensive ultrastructural investigation on the glandular indumentum of both the vegetative and reproductive organs in selected target-species belonging to the Lamiaceae family: Ballota acetabulosa Benth., Ballota rupestris Vis., Lavandula angustifolia Mill., Lavandula dentata L., Salvia greggii Grey, Salvia uliginosa Benth., Salvia verticillata Benth., Scutellaria sieberi Benth., Scutellaria altissima L. and Scutellaria caucasica A.Ham.
The investigation showed the occurrence of different types of glandular trichomes:
(i) peltate trichome, present on leaves and inflorescences of all of the species. It is constituted by a basal epidermal cell, a neck-cell and by a multicellular glandular head surrounded by a large subcuticular space in which the secretion is stored. The histochemical tests proved the production of terpenoidic, polysaccharidic and flavonoidic compounds. The presence of both lipophilic and hydrophilic components appears as osmiophilic droplets immersed in an abundant granular matrix. The secreted material is released after cuticle rupture.
(ii) short capitate hair widespread on both the vegetative and the reproductive organs of all the examined species. It is constituted by a basal epidermal cell, a neck-stalk cell and by a glandular head of 2-4 cells surrounded by a thin subcuticular space. The secreted material exhibits a strong positive response only to the hydrophilic dyes. The most striking ultrastructural feature is the presence of abundant Golgi bodies, sites of the synthesis and storage of polysaccharides.
(iii) long capitate trichomes observed only on Salvia species. It is composed by 1-2 epidermal cells, 2 stalk cells, 1 neck cell and by a globose head of 1-2 secretory cells surrounded by a storing chamber. The secretion is exclusively constituted by terpenes. The cytoplasm of the secreting cells is rich in plastids containing starch granules and a well-developed smooth endoplasmic reticulum, cellular compartments typical of a terpenoidic secretion.
(iv) long capitate trichomes observed only on the inflorescences of Scutellaria species. It is composed by 2 epidermal cells, 2-4 stalk cells, 1 neck cell and by 8 up to 18-20 secretory cells. Each secretory cells presents a small subcuticular space at the apex. The secretion is characterized by a complex composition, positive to lipophilic and hydrophilic dyes. Therefore, the secretory products are constituted of polysaccharides, terpenes and polyphenols. On the apex of each secreting cell a small portion of the cuticle layer raises, originating a small chamber in which electrondense fibrillar or granular material is stored. Occasionally some prearranged openings for the release of the secretion were observed, but most part of the secreting material seems to be extruded through the outer periclinal wall.
These highly-specialized secretory structures are characterized by a wide morphological and chemical polymorphism and by different mode of release of the secretory products. This extensive range of variability is probably crucial in determining different ecological rules
Response of dandelion (Taraxacum officinaleWeb) to heavy metals from mine sites: micromorphology of leaves and roots.
Get PDF
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
The Ghirardi Botanical Garden : a “natural laboratory” for studying the morphological and phytochemical diversity of selected medicinal plants in an integrated ecological framework
No full textThe Botanical Garden “G.E. Ghirardi” (BGG, Toscolano Maderno - Brescia) of the Department of Pharmaceutical Sciences of the Milan University has a long tradition in the cultivation, study and preservation of the genetic resources of officinal species, in accordance with the priority tasks of the Convention on Biodiversity.
Recently a dedicated research project started, integrating multidisciplinary analyses on target officinal species preserved at BGG, with the principal aim of characterizing these “plants” as interacting components of their own ecosystem. Indeed, the project was planned combining a dual perception: phytocentric, through the study of the biotic mutualistic interactions, mediated by the emission of secondary metabolites, and anthropocentric, referring to the potential importance to humans in the therapeutic, food and cosmetic sectors.
The work program includes: (i) the census of the plant heritage preserved at BGG; (ii) the selection of target-species for the morphological characterization of the secretory tissues and for the analysis of phytochemical profiles; (iii) the analysis of the biological activities of the secondary metabolites; (iv) case-studies on their ecological and functional roles.
In this perspective, BGG will represent a “natural laboratory” for studying the morphological and phytochemical diversity of officinal plants in an integrated ecological framework, aiming at assessing their importance for potential future exploitation by humans.
As preliminary activities of the project, we addressed our interest towards a better understanding of the micro-morphology and anatomy of the secreting structures, and on the characterization of VOC and essential oil profile of target-species belonging to the Lamiaceae family: Ballota acetabulosa Benth., Ballota rupestris Vis., Lavandula angustifolia Mill., Lavandula dentata L., Salvia greggii Grey, Scutellaria sieberi Benth., Scutellaria altissima L. and Scutellaria brevibracteata Stapf.
We report the results of the preliminary micromorphological observations on a) the structure and distribution of glandular tissues, b) the histochemical nature of the secreted substances, c) the mode of production and release of the secretory products. In addition, the VOC fingerprint and the characterization of essential oil produced in the glandular tissues are presented
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
