Cross-talk between high light stress and plant defence to the two-spotted spider mite in Arabidopsis thaliana

Little is known about how plants deal with arthropod herbivores under the fluctuating light intensity and spectra which occur in natural environments. Moreover, the role of simultaneous stress such as excess light (EL) in the regulation of plant responses to herbivores is poorly characterized. In the current study, we focused on a mite-herbivore, specifically, the two-spotted spider mite (TSSM), which is one of the major agricultural pests worldwide. Our results showed that TSSM-induced leaf damage (visualized by trypan blue staining) and oviposition rate (measured as daily female fecundity) decreased after EL pre-treatment in wild-type Arabidopsis plants, but the observed responses were not wavelength specific. Thus, we established that EL pre-treatment reduced Arabidopsis susceptibility to TSSM infestation. Due to the fact that a portion of EL energy is dissipated by plants as heat in the mechanism known as non-photochemical quenching (NPQ) of chlorophyll fluorescence, we tested an Arabidopsis npq4-1 mutant impaired in NPQ. We showed that npq4-1 plants are significantly less susceptible to TSSM feeding activity, and this result was not dependent on light pre-treatment. Therefore, our findings strongly support the role of light in plant defence against TSSM, pointing to a key role for a photo-protective mechanism such as NPQ in this regulation. We hypothesize that plants impaired in NPQ are constantly primed to mite attack, as this seems to be a universal evolutionarily conserved mechanism for herbivores

Rapport IV.10 Modèle de transport et d'étalement des nappes d'hydrocarbures et comparaison avec les observations

Model of oil spills'transport and spreading and comparaison with observations. A mathematical model of oil spills' transport and spreading is presented. The model differs from previous ones by its capability of taking simultaneously gravity, friction and surface tension into account -allowing the simulation of small experimental spills as well as large accidental spills -and by a new parameterization of surface tension and interface stresses, better adapted to real field conditions. The model is tested by the simulation of in situ experiments where the position and the thickness of the spill are measured by remote sensing. An excellent agreement is found between the model's predictions and the observations .On présente un modèle mathématique du transport et de l'étalement des nappes d'hydrocarbures à la surface de la mer. Le modèle se distingue des modèles antérieurs par sa capacité à prendre en compte simultanément les effets de gravité, friction, et de tension superficielle, -permettant ainsi la modélisation des nappes expérimentales de petites dimensions comme des grandes nappes accidentelles -, et par une nouvelle paramétrisation de la tension superficielle et du frottement interfacial, mieux adaptée aux conditions réelles en mer. La performance du modèle est évaluée par la modélisation d'expériences in situ où la position et l'épaisseur de la nappe sont mesurées par télédétection. Un excellent accord est trouvé entre les prévisions du modèle et les observations.Nihoul Jacques C. J. Rapport IV.10 Modèle de transport et d'étalement des nappes d'hydrocarbures et comparaison avec les observations. In: L'hydraulique et la maitrise du littoral. Problèmes côtiers posés par le mouvement des sédiments et la pollution. Dix-huitièmes journées de l'hydraulique. Marseille, 11-13 septembre 1984. Tome 4, 1984