Mise Au Point Des Techniques De Micropropagation Pour Une Multiplication Massive De Gladiolus Segetum Et Gladiolus Dubius

Apical buds of corms of gladiolus (Gladiolus segetum and Gladiolus dubius) were cultivated on Murashige and Skoog (1962) medium supplemented with IBA 0.1 mg.l-1 and BA 2 mg.l-1. The number of newly formed buds was 3,8 and 4,13 buds per explants for respectively Gladiolus segetum and Gladiolus dubius. The in vitro Rooting need a supplement with auxin and sucrose. Rooting is not present in the control medium. The rate of rooting varied from 10 to 36%, depending on the species and the concentration of IBA in the medium. The Important rooting (36%) is observed for Gladiolus segetum in the presence of IBA 1 mg.l -1. Finally, the acclimatization is possible, these shoots rooted have formed many corms after 6 weeks of culture

Two-scale Time Homogenization for Isotropic Viscoelastic- Viscoplastic Homogeneous Solids Under Large Numbers of Cycles

AbstractA two-scale time homogenization approach for coupled viscoelastic-viscoplatic (VE-VP) homogeneous solids and structures subjected to large numbers of cycles, is proposed. The main aim is to give a description of the long time behaviour, by calculating the evolution of internal variables within the structure, while reducing the computational overhead. This method consists in decomposing the original VE-VP initial-boundary problem into coupled micro-chronological (fast time scale) and macro-chronological (slow time-scale) problems. The proposed methodology was implemented and studied for J2 VP coupled with VE using fully implicit time integration and a return-mapping algorithm. An illustration of the time homogenization on a simple case is presented and a good agreement with the reference solution is observed

The impact of Tunisian Capparidaceae species on cytological, physiological and biochemical mechanisms in lettuce

AbstractThe Capparidaceae species had excellent phytotoxic effect on weed growth in Tunisia with, regardless to the several perturbation of physiological and cellular processes in target plants. In this study, we report the allelochemicals stress of aqueous (15g/L) and methanol (6g/L) extracts of leaves Capparis spinosa L. and siliquae of Cleome arabica L. on the cytological, physiological and biochemical processes of lettuce. The results showed that aqueous extracts exhibited the mainly cytotoxic effect on root tip cells, with a morphological modification and necrosis phenomena, which correlated with a drastic reduction of mitotic index. In fact, allelochemicals present in these extracts triggered oxidative damage in lettuce manifested by lipid peroxidation as evidenced by increased content of malondialdehyde. In response to this, the disruption in the membrane permeability was revealed by a strong electrolyte leakage. The increase of the antioxidant secondary metabolites was the result of the lyase activity stimulation. In addition, the photosynthetic pigments, including chlorophyll and carotenoids, were maintained by the functional regulation of proline in the cellular levels. These empirical studies consist in valuable bases for more thorough promising studies will help to decipher the allelochemicals; thus, to enhance new natural herbicides mode of action and to help its application on agricultural fields

MORPHOLOGICAL AND KARYOLOGICAL STUDIES IN TWO WILD IRIS SPECIES (IRIDACEAE) OF TUNISIA

Morphological and cytological variation among two wild iris species (iris juncea (poir) and iris sisyrinchium. (l)) from tunisia was studied. Initially, morphological traits analyzed concern floral and vegetative characters. Analysis of variance showed significant differences. Higher variation coefficient belongs to flower height, flower diameter, filament length, seed diameter, and level number. Pearson coefficients correlations between different characters were positive and highly significant (p< 0.0001) for flower diameter and flower heigth. Factor analysis showed that only two axes define 100% of variance among characters. Secondly, in cytological variation each species had different karyotypic formula such as 2n = 32 = 30sm + 2st for iris juncea with a satellite in pair number 2; 2n= 24 = 18 st + 6 sm for iris sisyrinchium beja‘s population and 2n=26=18 st + 8sm for iris sisyrinchium hammamet population

Variation in phytochemical constituents and allelopathic potential of Nigella sativa with developmental stages

AbstractThis study was conducted to evaluate the phytochemical content and allelopathic potential of two Nigella sativa varieties, having a Tunisian and Indian origin. Aqueous extracts of seeds and aerial parts harvested at three developmental stages (vegetative, flowering and fruiting) were evaluated on lettuce germination and seedling growth. The total phenolics, flavonoids, flavonols and flavones, alkaloids and proanthocyanidins contents in the aqueous extracts were highest in the vegetative stage. For allelopathic activity, all aqueous extracts significantly delayed germination, reduced its rate and affected seedling growth, while seeds aqueous extracts affect only seedling growth. In addition, the analysis using the Whole-range assessment method (WESIA software) showed a stronger inhibition index of the Tunisian variety aqueous extracts of aerial parts harvested at flowering stage compared to the two other stages. While, Indian variety was most phytotoxic at the vegetative stage. Seeds of the two varieties showed similar toxicity for lettuce and they are less toxic than aerial parts. Results showed that it would be advisable to identify the development stage of a plant that has the greatest level of allelochemicals to assist harvest time and to maximize efficiency of the allelopathic potential of a given plant

Determination of precipitate strengthening in Al-Cu alloys through micropillar compression: Experiments and multiscale simulations

Al-Cu alloys are efficiently strengthened by different types of precipitates: Guinier-Preston zones, θ\u27\u27 (Al3Cu) and θ\u27 (Al2Cu). The contribution of each type of precipitate to the strengthening of the alloy was determined by means of a high-throughput strategy based on micropillar compression. To this end, an Al-4 wt.% Cu alloy was manufactured by casting, following by several homogenization heat treatments at high temperature. The alloy was aged at 23ºC and 180ºC for different times to produce different precipitate structures [1]. Micropillars were machined using a focus ion beam in grains oriented for single and multiple slip and compressed at ambient temperature. The critical resolved shear stress was determined as a function of the applied strain for micropillars with different sizes oriented for single slip to assess the size effect. It was found that the properties of the bulk crystals could be obtained by testing square micropillars with cross-section \u3e 5 x 5 µm2. In addition, the precipitate type and spatial distribution as well as the mechanisms of dislocation/precipitate interaction were studied in the transmission electron microscope from lamella extracted from the deformed micropillars. It was found that Guinier-Preston zones and small θ\u27\u27 precipitates (\u3c 50 nm) were sheared by dislocations while dislocations formed Orowan loops around large θ\u27 precipitates. Afterwards, the effect of latent hardening for the different types of precipitates was studied by compression of micropillars oriented for double slip (coplanar and non-coplanar) as well as for multiple slip. In parallel, the critical resolved shear stress in the overaged Al-Cu alloys containing large θ\u27 precipitates was simulated by means of dislocation dynamics simulations using the discrete-continuous method in combination with a fast Fourier transform solver to compute the mechanical fields [2]. Simulations took into account the effect of precipitate shape, orientation and volume fraction as well the elastic mismatch between the matrix and the precipitate, the stress-free transformation strain around the precipitate and the dislocation character as well as dislocation cross-slip. In addition, the results of the micropillar compression tests were used to calibrate the latent hardening parameters of a crystal plasticity model, so they can be used to predict the mechanical behavior of polycrystals by means of computational homogenization. Overall, the results of this investigation show how micropillar compression can be used as a high-throughput technique to obtain the bulk properties of precipitation-strengthened alloys as well as to validate the results of simulation strategies at lower length scales (dislocation dynamics) and to provide input information for simulations at larger length scales (computational homogenization of polycrystals). [1] A. Rodríguez-Veiga, B. Bellón, I. Papadimitriou, G. Esteban-Manzanares, I. Sabirov, J. LLorca. A multidisciplinary approach to study precipitation kinetics and hardening in an Al-4wt.%Cu alloy. Journal of Alloys and Compounds, 757, 504-519, 2018. [2] R. Santos-Güemes, G. Esteban-Manzanares, I. Papadimitriou, J. Segurado, L. Capolungo, J. LLorca. Discrete dislocation dynamics simulations of dislocation- θ’ precipitate interaction in Al-Cu alloys. Journal of the Mechanics and Physics of Solids, 118, 228-244, 2018