1,721,066 research outputs found
Screening Of Salt Tolerance In Chilean Landraces Of Quinoa: Agronomical, Physiological And Nutritional Parameters
No full textQuinoa (Chenopodium quinoa Willd.) is a facultative halophyte and some varieties are able to cope with salinity levels as high as those present in sea water. Due to its traditionally broad cultivation area (from the salt flats of the Andes at 3,800 m above sea level to the seacoast and from Colombia down to southern Chile), there is a very wide range of quinoa cultivars adapted to specific conditions displaying a broad genetic variability in stress tolerance. For this reason, quinoa offers a valuable source of germplasm for breeding new cultivars adapted to stressful environments in diverse geographical conditions and for identifying mechanisms potentially useful in breeding tolerant glycophytes. In Chile, the genetic distance between highland (altiplano) and coastal cultivars of quinoa has been assessed but their responses to salinity are less known. In the present work, the response to salt treatments (0, 100 and 300 mM NaCl) was investigated in one altiplano landrace, R49, and two coastal ones, VI-1 and VR (from central and southern Chile, respectively). Salt treatment caused a significant increase in Na+ concentrations in all plant organs; the Na+ concentration accumulated in leaves under 300 mM salt was highest in VI-1 and was ca. 1.5- to 3-fold higher in leaves and roots of plants grown under 300 mM NaCl than 100 mM NaCl. Growth was significantly inhibited by the lower salt concentration only in R49, whereas 300 mM NaCl reduced growth also in VI-1 and VR, albeit to a lower extent than in R49. The concentrations of photosynthetic pigments, total phenolics and flavonoids were differentially affected by salt in leaves of the three cultivars. Seed production at harvest was unaffected or even enhanced (VR) by 100 mM NaCl relative to controls, while with 300 mM it was reduced in R49 and VI-1 (ca. 80% and 40% inhibition, respectively) but was not affected in VR. The germinability of seeds collected from plants grown in the presence (100 or 300 mM) or absence (0 mM) of NaCl was tested on agar plates containing 0-500 mM NaCl. Results showed that the response varied between landraces with VR exhibiting the highest sensitivity (germination was inhibited even by 100 mM NaCl). Seed protein profiles (SDS-PAGE of total proteins and the amount of the 11S seed storage protein chenopodin) were compared among different cultivars not treated with salt and the effect of salt treatments on protein profile were checked in the frame of the single cultivar; this allow to compare the differences due to the genotype and also the plant response to the salt treatments
High zinc concentrations reduce rooting capacity and alter metallothionein gene expression in white poplar (Populus alba L. cv. Villafranca)
No full textPoplar is a good candidate for phytoremediation purposes because of its rapid growth, extensive root system, and ease of propagation and transformation; however its tolerance to heavy metals has not been fully investigated yet. In the present work, an in vitro model system with shoot cultures was used to investigate the tolerance to high concentrations of zinc (Zn) of a commercial clone (Villafranca) of Populus alba. Based on chlorophyll content (leaf chlorosis) and the rate of adventitious root formation from shoot cuttings as parameters of damage, 0.5-4 mM zinc concentrations were all toxic albeit to different extents. Northern blot and reverse transcriptase (RT)-PCR analyses were used to examine the expression profiles of types 1, 2 and 3 PaMT genes in stems, leaves and roots of plants exposed to Zn treatments. In leaves, MT1 and MT3 mRNA levels were enhanced by Zn, while MT2 transcripts were not affected. The PaMT expression profiles were differentially affected by Zn in an organ-specific manner, and the relationship with Zn concentration and exposure time was rarely linear. The developmental and molecular data reveal that the in vitro model is a sensitive and reliable system to study heavy metal stress responses. © 2006 Elsevier Ltd. All rights reserved
Morphogenesis in Cultured Thin Layers and Pith Explants of Tobacco. II. Early Hormone-modulated Polyamine Biosynthesis
No full textIn order to gain deeper insight into the interrelationships between polyamines and hormones, superficial thin layers and pith explants, excised from the stem of tobacco (Nicotiana tabacum L.) plants in the vegetative stage, were cultured under various hormonal conditions (IAA, IAA + BA, BA) and in a hormone-free medium, in the presence or in the absence of 100 μmol/L putrescine. In thin layers at 24 h, activation of putrescine biosynthesis via both arginine-(ADC) and ornithine decarboxylases (ODC) as well as free putrescine accumulation were detected in the IAA treatment, and via ADe alone in the presence of IAA + BA. BA caused an inhibition of or had no effect on putrescine biosynthesis. In pith explants, although some free putrescine accumulated in IAA treatment, no increase in its biosynthetic activity was detectable. No DAO activity could be detected in any treatment early in culture either in superficial or deep tissues. Exogenous putrescine did not affect this pattern. The modulation of polyamine biosynthesis by the different hormones in superficial and pith explants is discussed in relation to putrescine accumulation and oxidation and to early cytological events occurring in culture and previously described (Altamura et al., 1995). © 1995, Gustav Fischer Verlag, Stuttgart. All rights reserved
Pre-harvest polyamine and aminoethoxyvinylglycine (AVG) applications modulate fruit ripening in Stark Red Gold nectarines (Prunus persica L. Batsch).
No full textPutrescine (5, 10 and 20 mM), spermidine (0.5, 1 and 2 mM) and aminoethoxyvinylglycine (AVG; 0.32, 0.64 and 1.28 mM) were applied to peach trees (Prunus persica L. Batsch cv Stark Red Gold) under open field conditions. Treatments were performed 28 (polyamines; PAs) and 21 or 7 (AVG) days before harvest at 115 dAFB. Both PAs and AVG reduced ethylene production of fruit, delayed loss of firmness, retained titratable acidity, and prevented the increase in dry matter (DM) and soluble solids concentration (SSC). Fruit drop was consistently reduced by AVG at both application times, and by the highest spermidine concentration. Endogenous PA levels in treated fruit were transiently affected (7 d after treatment), but returned to control values at harvest in both mesocarp and epicarp tissues. Northern analysis of ethylene biosynthetic genes, aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO), and of those involved in PA biosynthesis, arginine decarboxylase (ADC), ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (SAMDC), was performed in mesocarp tissue at harvest. AVG and putrescine reduced the accumulation of ACO and SAMDC messages, putrescine also influenced ACS transcript levels, while spermidine did not affect any of these genes. Results are discussed on the basis of the reduction by PA and AVG of ethylene production, and confirm the capacity of these naturally occurring substances to modulate fruit ripening
Comparing salt-induced responses at the transcript level in a salares and coastal-lowlands landrace of quinoa (Chenopodium quinoa Willd)
Full text linkTo further our understanding of the mechanisms governing salt stress responses and adaptation in halophytes, we explored morphological, metabolic, and gene expression responses to high salinity in quinoa (Chenopodium quinoa Willd). The main objective of this study was to analyze selected responsive genes in a time-course experiment to test for expression kinetics and to compare short-term salt-induced effects at the transcript level between two Chilean landraces belonging to different ecotypes. Quinoa genotypes exhibit a large variability in their responses to salinity, but it is not clear whether this is strictly related to the ecotype to which they belong. We tested this hypothesis by comparing the expression levels of genes involved in growth, ion homeostasis, abscisic acid (ABA) biosynthesis, perception, and conjugate cleavage, polyamine (PA) biosynthesis and oxidation, and proline biosynthesis as well as genes encoding ABA-dependent and independent transcription factors. Landraces R49 (salares ecotype) and Villarrica (VR, coastal-lowlands ecotype) were analyzed from 0.5 to 120 h after transfer to saline (300 mM NaC1) or non-saline (control) medium. All the genes, except CqSOS1 and CqNHX, were investigated here for the first time in quinoa under salt stress. Transcript levels were determined by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) analysis. Germination, seedling growth, ABA, and PA contents were evaluated in parallel. Even though on saline medium germination was inhibited in VR but not in R49, seedling growth reduction at 120 h was not substantially different in the two landraces. The ABA biosynthetic enzyme NCED was the most strongly salt-induced gene; ABA content was similarly enhanced (shoots) or unaffected (roots) in both R49 and VR. NaC1 treatment also altered transcript levels of some PA metabolic enzymes and the PA profile leading to an enhanced ratio between the higher PM and putrescine. All other genes also exhibited similar expression profiles in response to salinity in the two landraces especially in roots, while in shoots some differences were observed. Our results provide new information indicating that crucial salt adaptation strategies at the molecular level and in terms of ABA and PA contents are shared by the coastal-lowlands and salares landraces; however, the timing of the onset of transcriptional changes (e.g., NCED, ABF3, and RD22) may reflect genotype-dependent constitutive and/or inducible adaptive strategies.CONICYT (Chile)
University of Bologna (RFO)
FONDECYT (Chile)
3130624
University of Bologna
REP33/2015
REP54/201
Methyl-jasmonate-induced mitotic activity and cell expansion disrupt adventitious shoot formation in cultured tobacco thin layer explants.
No full textGoing 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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