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- Investigating the physiological mechanisms underlying Salicornia ramosissima response to atmospheric CO2 enrichment under coexistence of prolonged soil flooding and saline excessPublication . Pérez-Romero, Jesús Alberto; Duarte, Bernardo; Barcia-Piedras, Jose-Maria; Matos, Ana Rita; Redondo-Gómez, Susana; Caçador, Isabel; Mateos-Naranjo, EnriqueA 45-days long climatic chamber experiment was design to evaluate the effect of 400 and 700 ppm atmospheric CO2 treatments with and without soil water logging in combination with 171 and 510 mM NaCl in the halophyte Salicornia ramosissima. In order to ascertain the possible synergetic impact of these factors associate to climatic change in this plant species physiological and growth responses. Our results indicated that elevated atmospheric CO2 concentration improved plant physiological performance under suboptimal root-flooding and saline conditions plants. Thus, this positive impact was mainly ascribed to an enhancement of energy transport efficiency, as indicated the greater PG, N and Sm values, and the maintaining of carbon assimilation capacity due to the higher net photosynthetic rate (AN) and water use efficiency (iWUE). This could contribute to reduce the risk of oxidative stress owing to the accumulation of reactive oxygen species (ROS). Moreover, plants grown at 700 ppm had a greater capacity to cope with flooding and salinity synergistic impact by a greater efficiency in the modulation in enzyme antioxidant machinery and by the accumulation of osmoprotective compounds and saturated fatty acids in its tissues. These responses indicate that atmospheric CO2 enrichment would contribute to preserve the development of Salicornia ramosissima against the ongoing process of increment of soil stressful conditions linked with climatic change.
- Heat wave impacts on the model diatom Phaeodactylum tricornutum: Searching for photochemical and fatty acid biomarkers of thermal stressPublication . Feijão, Eduardo; Gameiro, C.; Franzitta, Marco; Duarte, Bernardo; Caçador, Isabel; Cabrita, Maria Teresa; Matos, Ana RitaGlobal warming is increasing the frequency and intensity of extreme thermal events, with inevitable consequences for marine ecosystems and organisms. Phytoplankton is at the base of marine food webs and diatoms are major contributors to global primary production. Therefore, environmental changes, such as heat, influencing growth, physiology and biochemical composition of diatoms, impact other organisms at higher trophic levels. The model diatom Phaeodactylum tricornutum, particularly rich in the long chain omega-3 eicosapentaenoic acid (EPA), and able to accumulate substantial amounts of storage lipids, has recently been the object of numerous works, regarding fundamental aspects of lipid metabolism and exploring its biotechnological potential for biodiesel and aquaculture purposes. The aim of this study was to use P. tricornutum, growing under controlled conditions, to examine the effects of a heat wave, in order to identify heat stress biomarkers. The photosynthetic and respiratory metabolism was investigated by Chlorophyll a fluorescence and by O2 evolution and discussed in connection with changes observed in the composition of photosynthetic pigments and fatty acids. Phaeodactylum tricornutum cells exposed to 26 °C displayed lower photosynthetic O2 production, but similar respiratory rate, comparing to cells at control temperature (18 °C), which is likely related to the biomass decrease observed under heat stress. Heat wave exposed cells also showed a less efficient PSII, higher energy dissipation and higher chlorophyll a and fucoxanthin concentrations, suggesting a heat-induced amplification of the light energy absorption capacity. Heat wave exposed cells showed lower relative EPA contents and double bond indexes, whereas the parameter inversely related to nutritional value, omega 6/omega 3 ratio, increased. Moreover, the analysis of the fatty acid profiles also suggested that heat exposure negatively impacted thylakoid lipids, in agreement with the decrease observed in photosynthesis. Results obtained highlight the negative impact of heat waves on diatom photosynthesis and nutritional value, as well as on their capacity to oxygenate ocean water. Furthermore, physiological parameters as well as fatty acids and photosynthetic pigments signatures, were identified, that could represent expedite biomarkers of thermal stress in future studies.