Mycorrhiza-like structures in rooted microshoots of Pinus pinea L.

Pinus pinea L. (stone pine) is one of the major plantation species in Iberian Peninsula, being Portugal the largest edible seed producer in the world. The induction and improvement of in vitro rhizogenesis of microshoots of Pinus pinea was developed in our laboratory using a co-culture system with ECM fungi. In the acclimation phase in mixed substrates, or in rhizotrons, anatomical and morphological studies were done to observe the evolution of the root system in microshoots from the co-culture system vs. control plants. Extensive dichotomous and coralloid branching of lateral roots occurred spontaneously in inoculated and control plants as well. Moreover, similar branching occurred in liquid culture of excised seedling roots without the presence of ECM fungi. The striking similarity of these organs with pine ectomycorrhizas prompted their anatomical analysis; however the presence of Hartig net was not confirmed. These results suggested that the development of ECM-like structures might have occurred spontaneously.info:eu-repo/semantics/publishedVersio

O-coumaric acid ester, a potential early signaling molecule in Pinus pinea and Pisolithus arhizus symbiosis established in vitro

During ectomycorrhizal (ECM) establishment, biochemical signals lead to the development of complex structures in both the plant and the fungus that ultimately result in the formation of an ectomycorrhiza. The cross-talk between partners begins before physical contact. Our objective was to investigate the chemical nature of the signals during the first stages of in vitro mycorrhization of Pinus pinea with Pisolithus arhizus. For this purpose a double-phase solid liquid medium was expressly developed for the co-culture in order to simplify the extraction and further molecules analysis. O-coumaric acid ester was identified using HPLC UV and LC DAD MS on the second day of co-culture and its presence was detected for up to 10 days. These results contribute to the characterization of biochemical signals during pre-colonization involving conifer species and an ECM fungus, and demonstrate the suitability of the double-phase medium developed for the growth of both organisms and for the analysis of released chemical mediators.info:eu-repo/semantics/publishedVersio

Daucus carota L. – An old model for cell reprogramming gains new importance through a novel expansion pattern of alternative oxidase (AOX) genes

The paper highlights Daucus carota L. as an ideal model to complement plant stress research on Arabidopsis thaliana L. Recently, alternative oxidase (AOX) is discussed as functional marker candidate for cell reprogramming upon stress. Carrot is the most studied species for cell reprogramming and our current research reveals that it is the only one that has expanded both AOX sub-family genes. We point to recently published, but not discussed results on conserved differences in the vicinity of the most active functional site of AOX1 and AOX2, which indicate the importance of studying AOX sequence polymorphism, structure and functionality. Thus, stress-inducible experimental systems of D. carota are especially appropriate to bring research on stress tolerance a significant step forward

Assessing the diversity of sea beet (Beta vulgaris L. ssp. maritima) populations

Beta vulgaris L. subsp. maritima (L.) Arcang., sea beet, is a morphologically and genetically variable species, belonging to beet primary gene -pool. This crop wild relative is a valuable genetic resource for resistance improvement in beets and could play an important role in crop yield sustainability. Eleven Madeiran sea beet populations were characterized using morphological descriptors and genetic markers. Our goal was to evaluate these populations as a potential source of valuable genetic material. Morphological characterization showed a high quantitative variation among populations. Plant height and inflorescence height parameters had the highest influence in the separation of populations. Molecular analysis was performed with polymorphic SSRs to determine genetic variability between populations. Both PCA and PCoA revealed three clusters that separated the populations according to morphological and genetic traits, respectively. This study contributes to the knowledge of sea beet diversity in Madeira’s archipelago and to the perception that the islands' specific environmental conditions influence its genetic variability, making these populations a possible gene source for sugar beet breeding programsinfo:eu-repo/semantics/publishedVersio

Molecular approach to characterize ectomycorrhizae fungi from Mediterranean pine stands in Portugal

Stone pine (Pinus pinea L.), like other conifers, forms ectomycorrhizas (ECM), which have benefi cial impact on plant growth in natural environments and forest ecosystems. An in vitro co-culture of stone pine microshoots with pure mycelia of isolated ECM sporocarps was used to overcome the root growth cessation not only in vitro but also to improve root development during acclimation phase. Pisolithus arhizus (Scop.) Rauschert and Lactarius deliciosus (L. ex Fr.) S.F. Gray fungi, were col lected, pure cultured and used in in vitro co-culture with stone pine microshoots. Samples of P. arhizus and L. deliciosus for the in vitro co-cultures were collected from the pine stands southwest Portugal. The in situ characterization was based on their morphotypes. To confirm the identity of the collected material, ITS amplification was applied using the pure cultures derived from the sporo carps. Additionally, a molecular profile using PCR based genomic fingerprinting comparison was executed with other genera of Basidiomycetes and Ascomycetes. Our results showed the effective ness of the techniques used to amplify DNA polymorphic sequences, which enhances the characte rization of the genetic profile of ECM fungi and also provides an option to verify the fungus identity at any stage of plant mycorrhization.info:eu-repo/semantics/publishedVersio

Los depósitos continentales triásicos

Las sedimentitas triásicas se encuentran representadas principalmente en dos regiones geográficas: la Región Patagónica, en donde se incluyen los afloramientos de El Tranquilo en el norte de la provincia de Santa Cruz y una serie de localidades ubicadas en el área del Macizo Nordpatagónico; y la Región Centro-oeste del país, donde se ubican los afloramientos de las provincias de Mendoza, San Luis, San Juan y La Rioja (Figuras 1 y 2). Además de estos grupos principales de afloramientos triásicos, se han identificado sedimentitas asignables a este período en el subsuelo de la cuenca Chacoparanense.Facultad de Ciencias Naturales y Muse

Two-dimensional finite element simulation of fracture and fatigue behaviours of alumina microstructures for hip prosthesis

This paper describes a two-dimensional (2D) finite element simulation for fracture and fatigue behaviours of pure alumina microstructures such as those found at hip prostheses. Finite element models are developed using actual Al2O3 microstructures and a bilinear cohesive zone law. Simulation conditions are similar to those found at a slip zone in a dry contact between a femoral head and an acetabular cup of hip prosthesis. Contact stresses are imposed to generate cracks in the models. Magnitudes of imposed stresses are higher than those found at the microscopic scale. Effects of microstructures and contact stresses are investigated in terms of crack formation. In addition, fatigue behaviour of the microstructure is determined by performing simulations under cyclic loading conditions. It is shown that crack density observed in a microstructure increases with increasing magnitude of applied contact stress. Moreover, crack density increases linearly with respect to the number of fatigue cycles within a given contact stress range. Meanwhile, as applied contact stress increases, number of cycles to failure decreases gradually. Finally, this proposed finite element simulation offers an effective method for identifying fracture and fatigue behaviours of a microstructure provided that microstructure images are available

Biochemical study of zygotic embryogenesis in stone pine (Pinus pinea L.) and its potential contribution to the development of somatic embryogenesis protocols

In this work we followed the biochemical events that take place during developmental stages of zygotic embryogenesis in stone pine. It’s a totally new approach, since until now; the research was focused only on the biochemistry of the mature pine nuts (nutritional aspect). To study the biochemical changes that take place in zygotic embryogenesis, the female cone collections were made from June to September, 2007. The female cones collected over this period were from just a few weeks after fertilization through to complete embryo maturation. The morphological stages of the seed development were characterized and photographed at each date for further use in correlations between biochemical variation and embryo development. The increase in the fresh weight of the pine seeds from consecutive collections was approximately 1 mg per day. During this period, the water content decreased and an increase in organic matter was observed, indicating changes in the constituent components during the maturation process. In mature seeds, oil content was 33.26% and proteins represented 24.31%. The soluble and insoluble proteins were extracted acording to Brownfield et al. (2007) and analysed by SDS-PAGE. Results showed that soluble and insoluble proteins profiles varied in different phases of embryo maturation. Inorganic composition was also monitored at each collection date. A complete description of mineral elements variation includes Ca, Mg, K, P, Mn, Fe, Na, Zn and Cu. Ca, Mg and K were the predominat elements present in the mature seeds. A better understanding of biochemistry of zygotic embryogenesis in Pinus pinea L. could be relevant, and lead to complete plant propagation through SE. It is anticipated, for example, that the results of this work could contribute to the development of new culture medium formulation that might enhance the efficiency of stages of stone pine SE