The effect of salinity on the growth, morphology and physiology of Echium amoenum Fisch. & Mey.

The salinity of water and soil decreases the growth and yield of agricultural products. Salinity affects many physiological and morphological processes of plant by influencing soil solution osmotic potential and ion absorption and accumulation of minerals. To evaluate the effect of salinity on some physiological and morphological characteristics of the medicinal plant of Echium amoenum, an experiment was carried out with completely random design in four replications. In this study, the effect of different levels of salinity, including control (non-saline water), 3, 6, 9 and 12 dS m-1 from natural saline water was examined on root length, leaf area, dry weight of roots and shoots, also on the amount of absorption of salts Na+, K+, Cl-, Ca2+, Mg2+ and the ratio of Na+/K+ and Ca2+/Na+ in root and shoot of plants and proline and total soluble sugars of leaf in the vegetative growth stage in the greenhouses. Results indicated that the application of saline water reduces significantly all morphological traits under study. Also, as the salinity increased, the density of K+, Ca2+ and Mg2+ and the ratio of Na+/K+ and Ca2+/Na+ in root and shoot of E. amoenum declined. In contrast, by increasing salinity, Na+ and Cl- concentration in roots and shoots significantly increased. As the salinity increased, proline concentration and leaf total soluble sugars also increased significantly compared with the control. The results showed that the accumulation of proline and soluble sugars are good indicators of salinity tolerance. Results also suggest that the plant resists against salinity through osmotic adjustment and ion absorption and sharing within its cells. This process is essential for the survival of plants in saline conditions.Key words: Salinity, Echium amoenum, vegetative growth, ion composition, proline, soluble sugars

Identification and estimation of a large factor model with structural instability

This paper tackles the identification and estimation of a high dimensional factor model with unknown number of latent factors and a single break in the number of factors and/or factor loadings occurring at unknown common date. First, we propose a least squares estimator of the change point based on the second moments of estimated pseudo factors and show that the estimation error of the proposed estimator is Op (1). We also show that the proposed estimator has some degree of robustness to misspecification of the number of pseudo factors. With the estimated change point plugged in, consistency of the estimated number of pre and post-break factors and convergence rate of the estimated pre and post-break factor space are then established under fairly general assumptions. The finite sample performance of our estimators is investigated using Monte Carlo experiments

The DSF family of quorum sensing signals: diversity, biosynthesis, and turnover

The diffusible signaling factor (DSF)-based quorum sensing (QS) system has emerged as a widely conserved cell–cell communication mechanism in Gram-negative bacteria. Typically, signals from the DSF family are cis-2-unsaturated fatty acids which regulate diverse biological functions. Recently, substantial progress has been made on the characterization of new members of this family of signals. There have also been new developments in the understanding of the biosynthesis of these molecules where dual enzymatic activities of the DSF synthase and the use of various substrates have been described. The recent discovery of a naturally occurring DSF turnover mechanism and its regulation provides a new dimension in our understanding of how DSF-dependent microorganisms modulate virulence gene expression in response to changes in the surrounding environment

Chemical Sensors Based on New Polyamides Biobased on (Z) Octadec-9-Enedioic Acid and β-Cyclodextrin

International audienceThe synthesis of new biobased polyamides from different β-cyclodextrin monomers and the (Z) octadec-9-enedioic acid is investigated. The aim of this study is to design different sensors, having different sensibilities and selectivities to a set of various volatile organic compounds (VOC) relevant in the early detection of lung cancer. The sensors are obtained from the synthesized polyamides, using multiwalled carbon nanotubes as conductive nanofillers and a layer by layer process. The conductive polymer nanocomposites (CPC) designed from the heptakis-6-amino β-cyclodextrin and 6A,6D diamino β-cyclodextrin have a high affinity for polar protic solvents, while the CPC having a matrix based on 6A,6D diamino 2A-G,3A-G,6B,6C,6E,6F,6G nonadeca-O-benzyl-β-cyclodextrin develops hydrophobic interactions with nonpolar solvents. Due to a higher accessibility of cyclodextrin, the chemoresistive response of the hydrophilic linear polyamide CPC is larger than one of the hydrophilic branched polyamide CPC. As required, the VOC diffusion/desorption phenomenon is reversible for all the sensors