Rapid recovery of photosynthesis and water relations following soil drying and re-watering is related to the adaptation of desert shrub Ephedra alata subsp. alenda (Ephedraceae) to arid environments

Ephedra alata subsp. alenda is the most important pioneer plant of the moving and semi-stable sand dunes in the deserts and steppes of south Tunisia and occurs naturally in the Grand Erg Oriental, one of the most extreme habitats for plant growth on the planet. A new analysis of physiological performance of this medically important and internationally threatened xerophytic shrub was conducted to assess possible mechanisms of drought tolerance and how these relate to its ecological success. Five-month old plants, grown under controlled climatic conditions, were subjected to a well-watered control treatment or progressive drought by withholding water for 14d with subsequent recovery for 7d. Soil water depletion significantly reduced stem relative water content (RWC) water potential (Ψw) and osmotic potential (Ψπ). Ephedra displayed more negative Ψw and Ψπ values of ca. -3.5 and -4.1MPa, respectively, at the end of the drought treatment, and were associated with turgor loss. Low stem Ψw reduced stomatal conductance (gs), photosynthetic CO2 assimilation rates (ACO2), transpiration (E) and internal CO2 concentration (Ci). However, instantaneous (WUE; ACO2 E-1) and intrinsic (WUEi; ACO2 gs-1) water use efficiency (WUE) increased gradually as water deficit was intensified. Stomatal closure therefore only exerted limited control against dehydration and could not compensate for decreases in soil water status, typical of anisohydric behavior. Drought-stressed stems accumulated high levels of proline up to 480% of control values, highlighting a pivotal role in osmotic adjustment during intense water deficit. In contrast, the osmotic adaptation to soluble sugars was limited. Drought-stressed plants increased ACO2, E, gs and Ci and decreased WUE and WUEi during the first 48h after re-watering, such that they reached similar values to those of control plants by the end of the experiment. Stem proline levels of drought-stressed plants returned to near control values with re-watering. Overall, rapid recovery of photosynthesis following drought-breaking moisture appears to be a critical mechanism allowing E. alata to withstand and survive dry environments

Las poáceas perennes: una alternativa para la rehabilitación y la restauración de pastos degradados en el Túnez presahariano

La magnitud de la presión humana sobre los pastos de la zona árida norteafricana se ha saldado con una rarefacción de las gramíneas perennes y la degradación de los suelos. Al ser la regeneración natural muy lenta es necesario plantearse el recurso de la reintroducción de especies locales rarificadas. El presente artículo examina la complementariedad de necesidades y comportamientos de dos gramíneas perennes de gran interés pastoral. Cenchrus ciliaris L., de origen tropical con fotosíntesis C4, de producción eminentemente en la estación cálida es interesante en años de pluviosidad favorable. Stipa lagascae Roem. & Shultes, especie C3 utiliza mejor el agua en períodos fríos. La mezcla de semillas de ambas especies complementarias en la utilización del agua, permite rehabilitar un pasto en el que el banco de semillas se haya agotado. La degradación de las propiedades físico-químicas del suelo, así como el acortamiento del periodo en que el agua del suelo está disponible para la vegetación, durante el verano, explican en parte la rarefacción de individuos de especies de origen tropical (caso de C. ciliaris) en beneficio de especies de origen mediterráneo ( caso de S. lagascae) en la flora de los pastos de la zona árida al norte del Sahara.Human pressure on North African ad pastures is causing soil degradation and rarefaction of perennial grasses. Artificial reintroduction of rarefied species can be an alternative in these areas, where spontaneous regeneration may be too slow. We have evaluated the ecological needs and performance of two perennial grasses with high grazing interest. Tropical Cenchrus ciliaris L. is a C4 that concentrates production during the warmest periods, and may be of particular interest in relatively wet years. Stipa lagascae Roem. & Shultes, is a C3 grass that may thrive under relatively cold conditions. Seeding mixes of these complementary species may contribute to rehabilitate grazing areas where the seed bank has been depleted. Soil degradation, and the reduction in the period when water is available during the summer, partly explain rarefaction of tropical species (as C. ciliaris) and gradual dominance of Mediterranean species (as S. lagascae) in northern Sahara arid pastures.L'ampleur de la pression humaine sur les parcours en zone aride Nord africaine s'est soldée par une raréfaction des graminées pérennes et une dégradation des sols. La régénération naturelle devenue très lente, il est nécessaire d'envisager le recours à la réintroduction d'espèces locales raréfiées. Le présent article examine la complémentarité des besoins et des comportements de deux graminées pérennes de grand intérêt pastoral. Cenchrus ciliaris L., d'origine tropicale, de type biochimique de photosynthèse en C4, et produisant surtout en saison chaude est intéressante en année à pluviosité favorable. Stipa lagascae Roem. & Shultes, espèce de type en C3 utilise mieux l'eau en période froide. Le semis en mélange de ces deux espèces complémentaires dans l'utilisation de l'eau, permet de réhabiliter un parcours, si les semenciers ont disparu. La dégradation des propriétés physico-chimiques du sol, ainsi que le raccourcissement de la durée des disponibilités en eau du sol pour la végétation, durant la période estivale, expliquent en partie la raréfaction des individus des espèces d'origine tropicale (cas de C. ciliaris) au profit des espèces d'origine méditerranéenne (cas de S. lagascae) dans la flore des parcours de la zone aride au Nord du Sahara

An 868 MHz 7.5 µW wake-up receiver with −60 dBm sensitivity

In wireless sensor networks (WSNs), batteries are unlikely to be replaced or recharged once they get depleted, because of costs and feasibility. In a typical application, sensor nodes should be accessible and able to respond within a defined period of time, especially in real-time applications. However, the idle listening of the radio wastes most of the energy since the radio transceiver is constantly active. On the other hand, putting it into sleep state disconnects the node from the network. To cope with such a challenge, an ultra-low-power radio receiver referred to as a wake-up receiver (WuRx) handles the idle listening while keeping the main radio completely off. A WuRx consumes much less power than the main transceiver and triggers an interrupt only when a packet with a user-defined address is received. Embedding such a device enables better event-triggered applications where real-time behavior is required and a longer lifetime is mandatory. The proposed WuRx features practical sensitivity and includes the minimum number of active components in order to remain within the power budget. In this paper, an ultra-low-power WuRx with a power of 7.5 µW and a sensitivity of −60 dBm is developed. The decoding process of 16 bit of a wake-up packet (WuPt) takes less than 15 ms

Germination responses of a Saharan species Henophyton deserti Coss. & Durieu to temperature and water stress

Henophyton deserti Coss. & Durieu, is an endemic Saharan plant of the Brassicaceae family. Experiments were conducted to assess the effects of temperature and water stress on seed germination. The germination responses of the seeds of H. deserti in complete darkness were determined over a wide range of temperatures (10°C, 15°C, 20°C, 25°C, 30°C, 35°C) and different water potentials (−0.2, −0.6, −0.8, −1.0, −1.2, −1.4, −1.6, −2.0 MPa) induced by polyethylene glycol (PEG-6000) in order to verify their resistance to drought conditions. Germination was inhibited by either an increase or decrease in temperature from the optimal temperature (20°C) and decreased with a decrease in water potential at all temperatures. An interaction between water potential and temperature yielded no germination at −2 MPa. An understanding of these factors is crucial for successful regeneration and recruitment of these long lived Saharan plant species

Utilisation de la technique cheminée après couverture accidentelle de l’artère carotide commune gauche lors de la pose d’une endoprothèse aortique=use of chimney graft after accidental coverage of the left common carotid artery in TEVAR procedure

Thoracic endovascular aneurysm repair (TEVAR) is currently the therapy of first choice for most thoracic aortic disease. Because aortic stent grafts are placed in the vicinity of aortic side branches, unintentional coverage of these arteries may occur.Pr\ue9requis : Le traitement endovasculaire est actuellement le traitement de choix dans le traitement des pathologies de l\u2019aorte thoracique. Les endoproth\ue8ses aortiques sont plac\ue9es \ue0 proximit\ue9 des art\ue8res des troncs supra\u2010aortiques et une couverture accidentelle de ses art\ue8res peut se produire. Observation : Nous rapportons le cas d\u2019un homme \ue2g\ue9 de 69 ans pr\ue9sentant un ulc\ue8re p\ue9n\ue9trant de la crosse aortique asymptomatique, \ue0 proximit\ue9 de l\u2019origine de l\u2019art\ue8re sous clavi\ue8re gauche. En raison des ant\ue9c\ue9dents m\ue9dicaux, nous d\ue9cidons de r\ue9aliser un traitement endovasculaire avec mise en place d\u2019une endoproth\ue8se au niveau de l\u2019h\ue9mi crosse aortique gauche, apr\ue8s avoir r\ue9alis\ue9 un pontage carotido\u2010sous clavier. Lors du d\ue9ploiement, le segment proximal de l\u2019endoproth\ue8se aortique couvre accidentellement l\u2019origine de la carotide commune gauche. Comme proc\ue9dure de sauvetage, nous avons r\ue9aliser avec succ\ue8s la revascularisation de l\u2019art\ue8re carotide commune gauche en utilisant la technique chemin\ue9e. Conclusion : Le traitement endovasculaire des pathologies aortiques a connu un regain de popularit\ue9 lors de la derni\ue8re d\ue9cennie. Malgr\ue9 les \ue9volutions r\ue9alis\ue9es, cette proc\ue9dure reste un challenge technique. La couverture accidentelle d\u2019une branche principale de la crosse aortique durant les proc\ue9dures endovasculaire est une complication s\ue9rieuse n\ue9cessitant une intervention imm\ue9diate. La technique chemin\ue9e est une solution peu invasive dans ce genre d\u2019accident, avec des r\ue9sultats promettant