Interaction between water and nutrient deficiencies in helianthus annuus

The physiological response of plants to water deficits are known to vary according to the conditions of application of drought stress and the rate of development of leaf water deficits. At the whole plant level the effect of the water shess is usually perceived as a decrease in photosynthesis and growth, and is associated with alterations in C and N metabolism (McDonald and Davies, 1996). The decrease in water potential affects transpiration and hence xylem transport of nitrate or reduced N into growing regions. The response of the photo-synthetic apparatus either to water stress or rehydration seems to be dependent "on leaf age (O'Neill, 1983; Wolfe et al., 1988). Degradation of both thylakoid and stromal N-containing compounds can occur in response to water stress, recovery from which may pequire more than a week (Chaves, 1991).

Antioxidant activities of eight Algerian plant extracts and two essential oils

Total phenol, hydroxycinnamic acid derivatives, flavone/flavonol and flavanones/dihydroflavonol contents of hydro-alcoholic extracts, obtained by sonication, from the aerial parts of Artemisia campestris L., Anthemis arvensis L., Haloxylon scoparium Pomel, Juniperus phoenicea L., Arbutus unedo L., Cytisus monspessulanus L., Thymus algeriensis Boiss et Reut, Zizyphus lotus L (Desf.) collected in Djebel Amour (Sahara Atlas, Algeria) were quantified by spectrophotometric methods. The chemical composition of the essential oils obtained by hydrodistillation from Artemisia campestris L. and Juniperus phoenicea I aerial parts were also evaluated by gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). The antioxidant activity of the extracts and essential oils was assessed measuring the capacity for preventing lipid peroxidation using two lipidic substrates (egg yolk and liposomes), the capacity for scavenging DPPH, ABTS, superoxide anion radicals, hydroxyl radicals and peroxyl radicals. Anti-inflammatory activity was assessed by measuring the capacity for inhibiting lipoxygenase. Reducing power and chelating capacity were also assayed. The results showed different amounts of total phenols depending on the method used: A. campestris extract had the highest levels of total phenols when the measurement was made at lambda = 280 nm, whereas H. scoparium and A. unedo extracts showed the highest levels of total phenols with Folin-Ciocalteau. C. monspessulanus had the highest levels of flavones/flavonols and flavanones/dihydroflavonols. The essential oils of A. campestris and J. phoenicea were mainly constituted by alpha-pinene, beta-pinene and sabinene; and a-pinene, respectively. The methods used for assaying the capacity for preventing lipid peroxidation revealed to be inadequate for extracts due to the great interferences detected. The essential oils were more active than the generality of extracts for scavenging peroxyl radicals and for inhibiting lipoxygenase, whereas A. unedo extract was the most active for scavenging ABTS, DPPH, superoxide anion radicals and it also had the best reducing capacity. In a general way, the great majority of the antioxidant activities correlated well with the phenol content although such correlation was not so clear with the flavonoid content. (c) 2013 Elsevier B.V. All rights reserved.

An autonomous system for ocean acoustic tomography

Vertical line arrays (VLA) are a widely used apparatus in underwater acoustics with applications in sonar prediction, underwater communications and acoustic tomography, among others. Recent developments in digital electronics and communications allow for off-the-shelf development of VLA systems, with a large number of embedded acoustic and non-acoustic sensors able to fulfill application requirements, as opposed to single or few receiver configurations available until only a few years ago. Very often, the flexibility in water column sampling is achieved by splitting the VLA into modules that can be assembled according to the application. Such systems can be deployed and recovered from small vessels with a shorthanded crew, and make it possible for research labs with reduced budgets and operational means (ships and manpower) to gain control over the whole development process, from data acquisition to post-processing.