CHANGES IN ABSCISIC ACID, STOMATAL CONDUCTANCE, AND ANTIOXIDANTS DURING LOW TEMPERATURE PRECONDITIONING AGAINST SO_2 INJURY IN CONTRASTING CULTIVARS OF COLEUS

The influence of 5 days of low temperature preconditioning (13℃) on SO_2 sensitivity in relationship to abscisic acid (ABA) concentration, stomatal conductance, transpiration rate, and SO_2 injury was examined in two cultivars of coleus found previously to differ in stress tolerance: SO_2-sensitive \u27Buckley Supreme\u27 (\u27BS\u27) and SO_2-insensitive \u27Marty\u27 (\u27M\u27). \u27BS\u27 plants grown at 20℃ for 5 days and then fumigated with SO_2 for 2hr had 75% overall injury; those grown at 13℃ for 5 days had only 13% SO_2 injury. Corresponding \u27M\u27 plants given 20 and 13℃ pretreatment had 17 and 0% injury, respectively. This decrease in SO_2 sensitivity following preconditioning at 13℃ was associated with an increase in ABA concentration and a decrease in stomatal conductance and transpiration (Tn) rate, which presumably decreased the penetration of SO_2 into the leaf. Changes in the levels of several antioxidants and associated enzyme systems were also determined. Stress-insensitive \u27M\u27 contained 47% more ascorbate (AsA) and 17% greater ascorbate peroxidase (AP) activity than stress-sensitive \u27BS.\u27 Temperature preconditioning increased AP activity in \u27BS\u27 by 11% which was comparable to that found in \u27M\u27 at 20℃. Thus, the phytoprotection afforded against SO_2 by temperature preconditioning appears to involve both avoidance and detoxification mechanisms

Particle-yield modification in jetlike azimuthal dihadron correlations in Pb-Pb collisions at √sNN=2.76TeV

The yield of charged particles associated with high-pt trigger particles (8<pt<15GeV/c) is measured with the ALICE detector in Pb-Pb collisions at √sNN=2.76TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta pt>3GeV/c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found. © 2012 American Physical Society

Harmonic decomposition of two particle angular correlations in Pb-Pb collisions at sNN=2.76TeV

Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at sNN=2.76TeV for transverse momenta 0.25<pTt,a<15GeV/c, where pTt>pTa. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η|<1.0. Distributions in relative azimuth δφ≡φt-φa are analyzed for |δη|≡|ηt-ηa|>0.8, and are referred to as "long-range correlations". Fourier components Vnδ≡〈cos(nδφ)〉 are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy Vnδ(pTt,pTa) is fully described in terms of single-particle anisotropies vn(pT) as Vnδ(pTt,pTa)=vn(pTt)vn(pTa). This expectation is tested for 1≤n≤5 by applying a global fit of all Vnδ(pTt,pTa) to obtain the best values vn{GF}(pT). It is found that for 2≤n≤5, the fit agrees well with data up to pTa~3-4GeV/c, with a trend of increasing deviation as pTt and pTa are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25<pT<15GeV/c range using a single vn(pT) curve; such a description is however approximately possible for 2≤n≤5 when pTa<4GeV/c. For the n=1 harmonic, however, a single v1(pT) curve is not obtained even within the reduced range pTa<4GeV/c. © 2012 CERN