João Silva

Effects of CO 2 enrichment on photosynthesis, growth, and nitrogen metabolism of the seagrass Zostera noltii

Seagrass ecosystems are expected to benefit from the global increase in CO2 in the ocean because the photosynthetic rate of these plants may be Ci-limited at the current CO2 level. As well, it is expected that lower external pH will facilitate the nitrate uptake of seagrasses if nitrate is cotransported with H+ across the membrane as in terrestrial plants. Here, we investigate the effects of CO2 enrichment on both carbon and nitrogen metabolism of the seagrass Zostera noltii in a mesocosm experiment where plants were exposed for 5 months to two experimental CO2 concentrations (360 and 700 ppm). Both the maximum photosynthetic rate (Pm) and photosynthetic efficiency (α) were higher (1.3- and 4.1-fold, respectively) in plants exposed to CO2-enriched conditions. On the other hand, no significant effects of CO2 enrichment on leaf growth rates were observed, probably due to nitrogen limitation as revealed by the low nitrogen content of leaves. The leaf ammonium uptake rate and glutamine synthetase activity were not significantly affected by increased CO2 concentrations. On the other hand, the leaf nitrate uptake rate of plants exposed to CO2-enriched conditions was fourfold lower than the uptake of plants exposed to current CO2 level, suggesting that in the seagrass Z. noltii nitrate is not cotransported with H+ as in terrestrial plants. In contrast, the activity of nitrate reductase was threefold higher in plant leaves grown at high-CO2 concentrations. Our results suggest that the global effects of CO2 on seagrass production may be spatially heterogeneous and depend on the specific nitrogen availability of each system. Under a CO2 increase scenario, the natural levels of nutrients will probably become limiting for Z. noltii. This potential limitation becomes more relevant because the expected positive effect of CO2 increase on nitrate uptake rate was not confirmed.

Mass-degenerate Higgs bosons at 125 GeV in the two-Higgs-doublet model

The analysis of the Higgs boson data by the ATLAS and CMS Collaborations appears to exhibit an excess of h! events above the Standard Model (SM) expectations; whereas no signicant excess is observed in h! ZZ ! four lepton events, albeit with large statistical uncertainty due to the small data sample. These results (assuming they persist with further data) could be explained by a pair of nearly mass-degenerate scalars, one of which is a SM-like Higgs boson and the other is a scalar with suppressed couplings to W + W and ZZ. In the two Higgs doublet model, the observed and ZZ ! four lepton data can be reproduced by an approximately degenerate CPeven (h) and CP-odd (A) Higgs boson for values of sin( ) near unity and 0:7 < tan < 1. An enhanced signal can also arise in cases where mh’ mH, mH’ mA, or mh’ mH’ mA. Since the ZZ ! four lepton signal derives primarily from a SM-like Higgs boson whereas the signal receives contributions from two (or more) nearly mass-degenerate states, one would expect a slightly dierent invariant mass peak in the ZZ ! four lepton and channels. The phenomenological consequences of such models can be tested with additional Higgs data that will be collected at the LHC in the near future.

Could the LHC two-photon signal correspond to the heavier scalar in two-Higgs-doublet models?

Centro de Fx13x10sica Tex13orica de Partx13x10culas, Instituto Superior Tx13ecnico,Technical University of Lisbon, 1049-001 Lisboa, Portugal(Dated: January 4, 2012)LHC has reported tantalizing hints for a Higgs boson of mass 125 GeV decaying into two photons.We focus on two-Higgs-doublet Models, and study the interesting possibility that the heavier scalarHhas been seen, with the lightest scalar hhaving thus far escaped detection. Non-observation ofhat LEP severely constrains the parameter-space of two-Higgs-doublet models. We analyze caseswhere the decay H!hhis kinematically allowed, and cases where it is not, in the context of typeI, type II, lepton-speci c, and ipped models.

Detecting new physics from CP violating phase measurements in B decays

The standard CKM model can be tested and New Physics detected using only CP-violating phase measurements in B decays. This requires the measurement of a phase factor which is small in the Standard Model, in addition to the usual large phases

Probing the scalar-pseudoscalar mixing in the 125 GeV Higgs particle with current data

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Use of light and inorganic carbon acquisition by two morphotypes of Zostera noltii Hornem

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Physiological responses of Zostera marina and Cymodocea nodosa to light-limitation stress

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Establishing research strategies, methodologies and technologies to link genomics and proteomics to seagrass productivity, community metabolism, and ecosystem carbon fluxes

. We also point out that identifying violations of the unitarity of the CKM matrix is rather difficult, and cannot be done with phase measurements alone.

The use of chlorophyll fluorescence for monitoring photosynthetic condition of two tank-cultivated red macroalgae using fishpond effluents

Centro de Fx13x10sica Tex13orica de Partx13x10culas (CFTP), Instituto Superior Tx13ecnico,Universidade Tx13ecnica de Lisboa, 1049-001 Lisboa, Portugal(Dated: May 22, 2012)LHC has found hints for a Higgs particle of 125 GeV. We investigate the possibility that such aparticle is a mixture of scalar and pseudoscalar states. For de niteness, we concentrate on a twoHiggs doublet model with explicit CP violation and soft Z

Multi-metric index based on the seagrass Zostera noltii (ZoNI) for ecological quality assessment of coastal and estuarine systems in SW Iberian Peninsula

The affinity for dissolved inorganic carbon (DIC) and the mechanisms to use HCO3 as a source of DIC for photosynthesis were investigated in two morphotypes of Zostera noltii Hornem. Both morphotypes were collected at Ria Formosa lagoon (Southern Portugal) at two different levels in the intertidal. Affinity for DIC at saturating photon fluence rate (PFR), estimated as photosynthetic conductance for CO2 (gp(CO2)), was reduced by 75% in the Z. noltii plants adapted to shade conditions (lower intertidal) in comparison to the sun morphotype (45 � 10 � 6 and 182 � 10 � 6 ms � 1 , respectively), indicating that the plants acclimated to sun conditions (higher intertidal) had a higher capacity to use HCO3 as DIC source for photosynthesis. Since external carbonic anhydrase activity was negligible and a large inhibitory effect was produced by Tris buffer addition, this HCO3 use was attributed to the operation of H + ATPases creating low pH zones in periplasmic space. The photosynthetic CO2-flux supported for this mechanism was calculated to be 53 Amol O2 m � 2 s � 1 in sun morphotype, about 80% out of maximum photosynthesis rate. In order to determine the possible photosynthetic energy cost of the HCO3 use, the effect of decreasing light on photosynthetic rates and gp(CO2) was estimated. Photosynthetic conductance decreased in both morphotypes at nonsaturating PFR. This dependence of gp(CO2) on PFR indicated the existence of a positive interactive effect between DIC and PFR which was more pronounced in the shade morphotype since the ascending slope of O2 evolution vs. PFR curves at limiting PFRs was reduced from 7.2 to 2.3 mmol O2 mol photon � 1 at 4 and 0.5 mol m � 3 of DIC, respectively.