Study of photosynthesis process in the presence of low concentrations of clomazone herbicide in tobacco (Nicotiana tabacum)

The effect of chemical residues of clomazone on photosynthetic processes has been studiedby using several low concentrations of the herbicide (0, 1, 0.1, 0.01, 0.001, 0.0001 and 0.00001) µM and seedlings of two varieties of tobacco (Nicotiana tabacum L. cv. Virginie vk51, Nicotiana tabacum, L. cv. Xanthi). The content of photosynthetic pigments, the parameters of the chlorophyll-a fluorescence and the JIP-test were performed on an adult leaf (AL) and a young leaf (YL), that gave a complementary designto know the action's mode of clomazone on the plant physiological processes. Clomazone reducedthe total chlorophyll (a+b), carotenoids pigments (reduction in size antenna pigments judged by an increase in the chlorophyll a/b ratio) in young leaves more than adults leaves. The maximal photochemical efficiency (Fv/Fm) of photosystem II (PSII) decreased significantly in youngleavescompared to adult leaves and in (Virginie) variety than (Xanthi) variety. Among the parameters calculated of the JIP-test most affected by the treatment, PIabs, 1-VJ, ABS/RC, DI0/RC, TR0/RC, ET0/RC, ET0/ABS, which indicated acomparable effects of clomazone(1μM, 0.1µM, 0.01µM) between the two types of leaves and the varieties used. More, the results showed that the concentration ( 1μM) was the most effective amongthe other low concentrations used and the (Virginie) variety ismore sensitive than the (Xanthi)variety. We conclude that clomazone has probably two combined functions (physiological, toxic) judged by the different behavior of both types of leaves in the presence of the herbicide

Modélisation des conditions d’environnement des bocaux de culture in vitro : bocaux avec agar et vitroplants

La présente étude traite de la modélisation des conditions des plantes en culture in vitro. Lorsque des vitroplants sont introduits dans les bocaux,l'humidité de l'air intérieur varie en fonction de leur stade de développementet ce en accord avec les courbes expérimentales. Les variations diurnes du déficit de pression de vapeur (DPV) présentent un maximum pendant laphotopériode et un minimum pendant la nyctipériode. Par ailleurs, grâce à la prise en compte des réservoirs de la plante, le modèle permet de décrire la déshydratation et la réhydratation des tissus, ce qui est potentiellement d'un intérêt pratique. Au cours du cycle diurne, la teneur en eau relative varie entre 75 et 90 %. Les flux d'eau dans la plante concordent bien avec les variations de la teneur en eau du réservoir plante et caractérisent bien les deux types de régimes de circulation de l'eau dans la plante : le régime de flux conservatif et le régime de flux non conservatif.Mots-clés : Modélisation, culture in vitro, humidité de l'air intérieur, réservoir-plante, déshydratation, réhydratatio

The waking brain: an update

Wakefulness and consciousness depend on perturbation of the cortical soliloquy. Ascending activation of the cerebral cortex is characteristic for both waking and paradoxical (REM) sleep. These evolutionary conserved activating systems build a network in the brainstem, midbrain, and diencephalon that contains the neurotransmitters and neuromodulators glutamate, histamine, acetylcholine, the catecholamines, serotonin, and some neuropeptides orchestrating the different behavioral states. Inhibition of these waking systems by GABAergic neurons allows sleep. Over the past decades, a prominent role became evident for the histaminergic and the orexinergic neurons as a hypothalamic waking center

Enhanced prefrontal serotonin 5-HT1A currents in a mouse model of Williams-Beuren syndrome with low innate anxiety

Williams-Beuren syndrome (WBS) is a neurodevelopmental disorder caused by the hemizygous deletion of 28 genes on chromosome 7, including the general transcription factor GTF2IRD1. Mice either hemizygously (Gtf2ird1+/−) or homozygously (Gtf2ird1−/−) deleted for this transcription factor exhibit low innate anxiety, low aggression and increased social interaction, a phenotype that shares similarities to the high sociability and disinhibition seen in individuals with WBS. Here, we investigated the inhibitory effects of serotonin (5-HT) on the major output neurons of the prefrontal cortex in Gtf2ird1−/− mice and their wildtype (WT) siblings. Prefrontal 5-HT receptors are known to modulate anxiety-like behaviors, and the Gtf2ird1−/− mice have altered 5-HT metabolism in prefrontal cortex. Using whole cell recording from layer V neurons in acute brain slices of prefrontal cortex, we found that 5-HT elicited significantly larger inhibitory, outward currents in Gtf2ird1−/− mice than in WT controls. In both genotypes, these currents were resistant to action potential blockade with TTX and were suppressed by the selective 5-HT1A receptor antagonist WAY-100635, suggesting that they are mediated directly by 5-HT1A receptors on the recorded neurons. Control experiments suggest a degree of layer and receptor specificity in this enhancement since 5-HT1A receptor-mediated responses in layer II/III pyramidal neurons were unchanged as were responses mediated by two other inhibitory receptors in layer V pyramidal neurons. Furthermore, we demonstrate GTF2IRD1 protein expression by neurons in layer V of the prefrontal cortex. Our finding that 5-HT1A-mediated responses are selectively enhanced in layer V pyramidal neurons of Gtf2ird1−/− mice gives insight into the cellular mechanisms that underlie reduced innate anxiety and increased sociability in these mice, and may be relevant to the low social anxiety and disinhibition in patients with WBS and their sensitivity to serotonergic medicines

Growth and gas exchange responses of Hevea brasiliensis seedlings to inoculation with Glomus mosseae

International audienc

Effect of Water Deficit and Salt Stress on Oxidative Parameters and Antioxidant Systems in Tomato (Solanum lycopersicum L.) Fruits

International audienceIn this study, the differential behaviour of antioxidant systems between water stress and salt stress, considering two stages of development of the fruit was investigated. The activities of superoxide dismutase (SOD) and catalase (CAT), as well as the activities and the relative transcript levels of the enzymes of ascorbate-glutathione cycle: ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), the levels of ascorbate pool and hydrogen peroxide (H 2 O 2) and malonyldialdehyde (MDA) contents were studied in fruits of tomato plants (Solanum lycopersicum L. cv. 'Micro-Tom') subjected to water and salt stresses. Water deficit was induced by holding off the irrigation for 3 and 6 days. To apply salt stress, plants were treated with 100 mM of NaCl for 3 and 6 days. H 2 O 2 content was generally increased with both water and salt stresses, however, MDA content was increased only with salt stress. Changes in ascorbate pool were noted in plants subjected to salt stress more than in plants subjected to water stress. Moreover, changes in SOD and CAT activities and in DHAR, MDHAR, APX and GR activities and relative transcript levels were depending on the type and period of stress and the fruit development stage. Moreover, the changes in enzyme activities in response to stress were not directly related to changes in the corresponding gene expressions. These results suggest that water and salt stress lead to oxidative stress and modulates the antioxidative responses of tomato fruits