Genome-wide transcriptional analysis of salinity stressed japonica and indica rice genotypes during panicle initiation stage

Rice yield is most sensitive to salinity stress imposed during the panicle initiation (PI) stage. In this study, we have focused on physiological and transcriptional responses of four rice genotypes exposed to salinity stress during PI. The genotypes selected included a pair of indicas (IR63731 and IR29) and a pair of japonica (Agami and M103) rice subspecies with contrasting salt tolerance. Physiological characterization showed that tolerant genotypes maintained a much lower shoot Na(+) concentration relative to sensitive genotypes under salinity stress. Global gene expression analysis revealed a strikingly large number of genes which are induced by salinity stress in sensitive genotypes, IR29 and M103 relative to tolerant lines. We found 19 probe sets to be commonly induced in all four genotypes. We found several salinity modulated, ion homeostasis related genes from our analysis. We also studied the expression of SKC1, a cation transporter reported by others as a major source of variation in salt tolerance in rice. The transcript abundance of SKC1 did not change in response to salinity stress at PI stage in the shoot tissue of all four genotypes. However, we found the transcript abundance of SKC1 to be significantly higher in tolerant japonica Agami relative to sensitive japonica M103 under control and stressed conditions during PI stage. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s11103-006-9112-0 and is accessible for authorized users

Ion homeostasis in the Chloroplast

peer reviewedThe chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis

A new formulation of a spray dispersion model for particle/droplet-laden flows subjected to shock waves

International audienceA new analytical model is derived based on physical concepts and conservation laws, in order to evaluate the post-shock gas velocity, the gas density and the spray dispersion topology during the interaction of a shock wave and a water spray in a one-dimensional configuration. The model is validated against numerical simulations over a wide range of incident Mach numbers $M_s$ and particle volume fractions $\tau_{v,0}$ . Two regimes of shock reflection have been identified depending on $M_s$ , where the reflected pressure expansion propagates either opposite to the incident shock-wave direction for weak incident Mach numbers or along with it for strong Mach numbers. The numerical simulations reveal the presence of a particle number-density peak for $M_s > 2$ and with particle diameters of the order of ${O}(10)\ \mathrm {\mu } \textrm {m}$ . The formation of the number-density peak is discussed and a necessary condition for its existence is proposed for the first time

Direct Numerical Simulation of polydisperse evaporating sprays in 3D jet configuration using Euler-Euler and Euler-Lagrange formalisms

International audienceThe use of robust and accurate Eulerian/Eulerian formulations in the modeling of reactive two-phase flow would be a major step forward in the framework of turbulent combustion modeling with massively parallel supercomputers. In the present contribution we rely on the recent developments conducted in the framework of homogeneous isotropic turbulence (Fréret et al. 2010; Fréret et al. 2012) using the Eulerian multi-fluid model (MF) in the context of Direct Numerical Simulation (DNS) to capture all stages of turbulent spray combustion for polydisperse sprays, and set up a 3D free jet configuration, thus reaching the next step of turbulent shear flows. The robustness and accuracy of the model and related numerical methods are evaluated and assessed on two configurations with non-evaporating and evaporating spray injection. With MF, we obtain the same level of accuracy as a baseline solution obtained with Lagrangian droplet tracking for rather similar computational time on a few hundred processors. This study yields a solid premise for the future 3D reacting configurations

Turbulent combustion of polydisperse evaporating sprays with droplet crossing: Eulerian modeling of collisions at finite Knudsen and validation

International audienceThe accurate simulation of the dynamics of polydisperse sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. In a companion paper, we have shown the capability of the Eulerian multi-fluid model to capture the dynamics and evaporation of such sprays and extended it in order to handle finite Stokes number crossing droplet trajectories, by using quadrature method of moments in velocity phase space conditioned on droplet size. Such a study was conducted in the limit of infinite Knudsen numbers. In this paper, we investigate a potential extension of such an approach in order to capture the dynamics of polydisperse spray collisions modeled by a Boltzmann operator at the mesoscopic level of description for finite Knudsen numbers. After deriving the model and presenting the dedicated numerical methods needed to preserve the moment space, we validate this approach and its capability of describing collisional crossing jets by comparing the results for both monodisperse and polydisperse clouds of particles with Lagrangian discrete particle simulations