18 research outputs found
Morphological and physiological responses of strawberry to a biostimulant and calcium application
info:eu-repo/semantics/publishedVersio
Controlo da altura de plantas ornamentais: alternativas sustentáveis aos reguladores de crescimento
V Jornadas Ibéricas de Horticultura Ornamental, Faro, 13-15 Outubro, 2011A necessidade de encontrar estratégias sustentáveis eficazes no
controlo da altura da planta é actualmente um grande desafio que se
coloca à horticultura ornamental protegida. Este estudo teve como
objectivo: (1) analisar a informação disponÃvel acerca dos factores que
afectam a altura das plantas; (2) compreender os mecanismos
fisiológicos envolvidos no processo de alongamento do caule; (3)
definir alternativas sustentáveis para produzir plantas compactas,
reduzindo ao mÃnimo a aplicação de ‘reguladores quÃmicos de
crescimento’. Concluiu-se que manter uma temperatura nocturna
superior à temperatura diurna (DIF negativa ou tratamento DROP) ou
a alteração do espectro luminoso (elevado rácio vermelho/vermelholongÃnquo)
apresentam um forte potencial como métodos não
quÃmicos no controlo da altura de várias espécies de plantas
ornamentais. O aumento do rácio vermelho/vermelho-longÃnquo,
poderá ser efectuado de diferentes modos incluindo a utilização de
filmes fotosselectivos e/ou recorrendo a um conjunto de medidas
facilmente aplicáveis tais como: (i) evitar densidades de plantação
muito elevadas; (ii) utilização de luz suplementar com elevado rácio
vermelho/vermelho-longÃnquo (ex. lâmpadas de assimilação em
substituição de lâmpadas incandescentes); (iii) evitar a exposição das
plantas à radiação do crepúsculo (devido à diminuição natural do rácio
vermelho/vermelho-longÃnquo). O stress mecânico é também uma
medida eficaz para a manutenção de plantas compactas em
determinadas espécies. Paralelamente, o recurso ao Melhoramento de
plantas no sentido de seleccionar cultivares ananicantes poderá ser bastante promissor. Porém, na maioria dos casos, não será uma
medida única que permitirá a obtenção de plantas compactas, mas a
combinação de várias estratégiasinfo:eu-repo/semantics/publishedVersio
Genotypic variation in the response to suboptimal temperature at different plant densities in cut chrysanthemum
Energy efficiency of greenhouse cut chrysanthemum (Chrysanthemum morifolium Ramat.) may be
increased by breeding. In addition to breeding for cultivars with a shorter reaction time at suboptimal temperatures,
an alternative approach would be to develop cultivars that are heavier at suboptimal temperatures so that they could
be grown at a higher plant density, enhancing the production per unit area. Therefore, the combined effect of
temperature and plant density on growth and development of four cut chrysanthemum cultivars was investigated in
three greenhouse experiments, carried out in different seasons. For growth-related traits, no interactions between
temperature and cultivar were found, limiting the possibilities for breeding. At suboptimal temperatures, growth rate
early in the cultivation period decreased as a consequence of a lower light interception resulting from a lower specific
leaf area. Thus a higher dry mass production at lower temperature could only be explained by a longer cultivation
time. Temperature also influenced external quality, but these effects were cultivar dependent. For instance,
temperature affected the slope of the positive linear relationship between total dry mass and number of flowers,
reducing number of flowers at low temperature for the same plant dry mass. It is concluded that there are possibilities
for breeding for suboptimal temperature-tolerant cultivars
Time dependent photon and neutrino emission from Mkr 421 in the context of the one-zone leptohadronic model
We apply a recently developed time-dependent one-zone leptohadronic model to study the emission of the blazar Mrk 421. Both processes involving proton-photon interactions, i.e. photopair (Bethe-Heitler) and photopion, have been modeled in great detail using the results of Monte Carlo simulations, like the SOPHIA event generator, in a self-consistent scheme that couples energy losses and secondary injection. We find that TeV gamma-rays can be attributed to synchrotron radiation either from relativistic protons or, alternatively, from secondary leptons produced via photohadronic processes. We also study the variability patterns that each scenario predicts and we find that while the former is more energetically favored, it is the latter that produces, in a more natural way, the usual quadratic behavior between X-rays and TeV gamma-rays. We also use the obtained SEDs to calculate in detail the expected neutron and neutrino fluxes that each model predicts
Iron metabolism in soybean grown in calcareous soil is influenced by plant growth-promoting rhizobacteria: a functional analysis
Iron deficiency results in severe yield losses, particularly in calcareous soils. Recent evidences suggest that biofertilizers with plant growth-promoting rhizobacteria (PGPR) may be an efficient strategy for enhancing iron (Fe) nutrition in legumes. This work aimed at evaluating the capacity of PGPR strains to enhance Fe uptake-related processes in soybean grown in calcareous soil. From the studied 24 PGPR, Sphingobium fuliginis ZR 1–6 and Pseudomonas jessenni ZR 3–8 strains were selected for the inoculation experiment based on their in vitro ability to produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid deaminase, siderophores, and organic acids, to tolerate high pH, and to reduce Fe3+. The effect of bacterial inoculation on improving Fe uptake was tested using each isolate alone or combined and through the evaluation of several morphological, physiological, and molecular parameters. Inoculation with S. fuliginis showed beneficial effects particularly at the root level by the improvement of ferric chelate activity (111%) and FRO2 expression (646%), resulting in increased Fe root content (62%). Inoculation with P. jessenii increased Zn and Mn concentrations in the trifoliates (463% and 51%, respectively), decreased Zn concentration in the roots (88%), and increased the expression of FER4 in the trifoliates (5260%). Combined inoculation of both strains fostered Fe accumulation in the trifoliates and increased the expression of IRT1 and FER4 genes, indicating an improved capacity of Fe translocation to the shoots. These results suggest that inoculation with selected PGPR strains could be effective in improving Fe uptake and accumulation in soybean grown under Fe-deficient conditions.info:eu-repo/semantics/publishedVersio
Young Tomato Plants Respond Differently under Single or Combined Mild Nitrogen and Water Deficit : An Insight into Morphophysiological Responses and Primary Metabolism
This study aimed to understand the morphophysiological responses and primary metabolism of tomato seedlings subjected to mild levels of nitrogen and/or water deficit (50% N and/or 50% W). After 16 days of exposure, plants grown under the combined deficit showed similar behavior to the one found upon exposure to single N deficit. Both N deficit treatments resulted in a significantly lower dry weight, leaf area, chlorophyll content, and N accumulation but in a higher N use efficiency when compared to control (CTR) plants. Moreover, concerning plant metabolism, at the shoot level, these two treatments also responded in a similar way, inducing higher C/N ratio, nitrate reductase (NR) and glutamine synthetase (GS) activity, expression of RuBisCO encoding genes as well as a downregulation of GS2.1 and GS2.2 transcripts. Interestingly, plant metabolic responses at the root level did not follow the same pattern, with plants under combined deficit behaving similarly to W deficit plants, resulting in enhanced nitrate and proline concentrations, NR activity, and an upregulation of GS1 and NR genes than in CTR plants. Overall, our data suggest that the N remobilization and osmoregulation strategies play a relevant role in plant acclimation to these abiotic stresses and highlight the complexity of plant responses under a combined N+W deficit
Impact of soybean-associated plant growth-promoting bacteria on plant growth modulation under alkaline soil conditions
Conventional strategies to manage iron (Fe) deficiency still present drawbacks, and more eco-sustainable solutions are needed. Knowledge on soybean-specific diversity and functional traits of their plant growth-promoting bacteria (PGPB) potentiates their applicability as bioinoculants to foster soybean performance under calcareous soil conditions. This work aimed to assess the efficacy of PGPB, retrieved from soybean tissues/rhizosphere, in enhancing plant growth and development as well as crop yield under alkaline soil conditions.Seventy-six bacterial strains were isolated from shoots (18%), roots (53%), and rhizosphere (29%) of soybean. Twenty-nine genera were identified, with Bacillus and Microbacterium being the most predominant. Based on distinct plant growth-promoting traits, the endophyte Bacillus licheniformis P2.3 and the rhizobacteria Bacillus aerius S2.14 were selected as bioinoculants.In vivo tests showed that soybean photosynthetic parameters, chlorophyll content, total fresh weight, and Fe concentrations were not significantly affected by bioinoculation. However, inoculation with B. licheniformis P2.3 increased pod number (33%) and the expression of Fe-related genes (FRO2, IRT1, F6′H1, bHLH38, and FER4), and decreased FC-R activity (45%). Moreover, bioinoculation significantly affected Mn, Zn, and Ca accumulation in plant tissues.Soybean harbors several bacterial strains in their tissues and in the rhizosphere with capacities related to Fe nutrition and plant growth promotion. The strain B. licheniformis P2.3 showed the best potential to be incorporated in bioinoculant formulations for enhancing soybean performance under alkaline soil conditions
Impaired cross-talk between the thioredoxin and glutathione systems is related to ASK-1 mediated apoptosis in neuronal cells exposed to mercury
Mercury (Hg) compounds target both cysteine (Cys) and selenocysteine (Sec) residues in peptides and proteins. Thus, the components of the two major cellular antioxidant systems – glutathione (GSH) and thioredoxin (Trx) systems – are likely targets for mercurials. Hg exposure results in GSH depletion and Trx and thioredoxin reductase (TrxR) are prime targets for mercury. These systems have a wide-range of common functions and interaction between their components has been reported. However, toxic effects over both systems are normally treated as isolated events.
To study how the interaction between the glutathione and thioredoxin systems is affected by Hg, human neuroblastoma (SH-SY5Y) cells were exposed to 1 and 5 μM of inorganic mercury (Hg2+), methylmercury (MeHg) or ethylmercury (EtHg) and examined for TrxR, GSH and Grx levels and activities, as well as for Trx redox state. Phosphorylation of apoptosis signalling kinase 1 (ASK1), caspase-3 activity and the number of apoptotic cells were evaluated to investigate the induction of Trx-mediated apoptotic cell death. Additionally, primary cerebellar neurons from mice depleted of mitochondrial Grx2 (mGrx2D) were used to examine the link between Grx activity and Trx function.
Results showed that Trx was affected at higher exposure levels than TrxR, especially for EtHg. GSH levels were only significantly affected by exposure to a high concentration of EtHg. Depletion of GSH with buthionine sulfoximine (BSO) severely increased Trx oxidation by Hg. Notably, EtHg-induced oxidation of Trx was significantly enhanced in primary neurons of mGrx2D mice. Our results suggest that GSH/Grx acts as backups for TrxR in neuronal cells to maintain Trx turnover during Hg exposure, thus linking different mechanisms of molecular and cellular toxicity. Finally, Trx oxidation by Hg compounds was associated to apoptotic hallmarks, including increased ASK-1 phosphorylation, caspase-3 activation and increased number of apoptotic cells