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- Yttrium and rare earth elements fractionation in salt marsh halophyte plantsPublication . Brito, Pedro; Malvar, Margarida; Galinha, Catarina; Caçador, Isabel; Canário, João; Araújo, M. Fátima; Raimundo, JoanaSalt marshes act as natural deposits of different metals (e.g. heavy-metals), while halophyte plants are known to retain and accumulate them in the different tissues. Scarce data exists on accumulation, partition and fractionation of YREE in these plants. To study the relationship between halophyte plants and YREE, contents of these metals were determined by ICP-MS in sediment, and in the different plants organs, from Rosário's salt marsh, in Tagus estuary (SW Europe). Results show significant differences (p < 0.001) in YREE contents between sediments. In non-colonised sediment Y was lower (5.0-18 mg·kg-1) compared to the Sarcocornia fruticosa and Spartina maritima sediment cores (19-26 and 20-26 mg·kg-1, respectively). The same was observed for ΣREE, with lower values in non-colonised sediment (32-138 mg·kg-1), while colonised ones presented higher contents (146-174 and 151-190 mg·kg-1, for S. fruticosa and S. maritima, respectively). These significant differences (p < 0.05) are explained by the sediments' nature. Yttrium and ΣREE Al-normalised ratios in non-colonised sediment ranged from 1.5 to 2.3 and 11 to 13, respectively. The colonised sediments revealed significant higher ratios (particularly for ΣREE/Al ratios; p < 0.001), varying from Y/Al: 1.8-2.3 and ΣREE: 13-16 for S. fruticosa, and Y/Al: 1.4-2.3 and ΣREE: 12-18, for S. maritima. Results suggest that these plants may promote YREE enrichment in the sediments. No differences in fractionation patterns among sediments and in both species roots were found, but fractionation was different from those in the sediment, with similar middle-REE (MREE) enrichment and no light-REE (LREE) and heavy-REE (HREE) fractionation. No evidence of YREE transfer to aboveground organs was observed. Different fractionation patterns in stems and leaves were registered, with clear enrichment of LREE relative to HREE and an increase in the MREE enrichment. Therefore, these plants showed low ability to accumulate and translocate YREE but may promote its enrichment in the sediments.
- Impact of heat and cold events on the energetic metabolism of the C3 halophyte Halimione portulacoidesPublication . Duarte, Bernardo; Santos, D.; Marques, J. C.; Caçador, IsabelAccording to the newest predictions, it is expected that the Mediterranean systems experience more frequent and longer heat and cold treatments events. Salt marshes will be no exception. Halimione portulacoides is a widely distributed halophyte highly adapted to harsh environments. Plants exposed to heat stress showed a reduction in the maximum electron transport rates and increase in the rate of RC closure, as indicated by the increase in M0. Alongside there was also a reduction in the quinone pool size while compared to the plants maintained in the control condition. In contrast plants exposed to low temperatures didn't show any signs of damage on the ETC. Heat-exposed individuals experienced a reduction of connectivity between the PS II antennae with simultaneous inhibition of the electron transport. This was more evident in the donor side of the PS II, Being this a consequence of the damages in the oxygen-evolving complex. Also if both PS I and PS II energy fluxes are observed, there are evident differences in the thermal tolerance of both photosystems. While compared to the control group, cold exposed plants showed an increased PS I efficiency (δR0) indicating a tolerance of this photosystem to low temperatures. Nevertheless, the excessive redox potential generated by light harvesting and inefficient processing was not dissipated correctly and consequently causing a oxidative stress situation. In the present study only heat exposed plants showed a significant activation of the xanthophyll cycle. Alongside with this mechanism and similarly to what was observed for cold treated plants, it could be observed an increase in auroxanthin content, an efficient energy quencher under stress conditions. The coupled activation of the xanthophyll cycle along with a higher auroxanthin synthesis suggests that heat-treated individuals had higher needs to dissipate excessive energy than the cells exposed to cold treatment. In both cases appears to exist an efficient ROS scavenging mechanism. According to our data, heat and cold treatment events can have serious impacts on H. portulacoides photobiology reducing its primary productivity. At the ecosystem level, these climatic events could pose a serious threat to the survival of this species in the new climatic reality that our planet is facing.
- Halophyte fatty acids as biomarkers of anthropogenic-driven contamination in Mediterranean marshes: Sentinel species survey and development of an integrated biomarker response (IBR) indexPublication . Duarte, Bernardo; Carreiras, João; Pérez-Romero, Jesús Alberto; Mateos-Naranjo, Enrique; Redondo-Gómez, Susana; Matos, Ana Rita; Marques, J. C.; Caçador, IsabelEstuarine environments are extremely affected by anthropogenic-driven contamination, namely heavy metals. In the recent years, several organisms have been studied to be used as sentinel species providing a wide range of biomarkers for estuarine contamination. Only recently non-traditional biomarkers, such as fatty acids, were included in animal ecotoxicology and impact assessment studies. Nevertheless, there is a wide lack of knowledge regarding to its application in estuarine plants. Considering this the present work aimed to evaluate the application of fatty acid profiling in Mediterranean halophytic species chronically exposed to different degrees of metal contamination, while incorporating these fatty acid biomarkers into an unifying index. From the fatty acids analysis two different types of sentinel halophytes could be identified: the contamination sensitive Halimione portulacoides (sea purslane), Sarcocornia fruticosa (glasswort) and Spartina patens (saltmeadow cordgrass), and the contamination-tolerant Spartina maritima (small cordgrass). In sensitive species the most evident changes in the fatty acid profiles were the decrease in the 18:3 and the increase in the 16:0 fatty acid relative concentrations, while the inverse trend was recorded in the tolerant S. maritima under chronic contamination. Beyond the evident physiological importance, these shifts in the halophyte fatty acid profiles provide some understanding on their use as biomarkers of metal contamination. After application of an integrated biomarker response (IBR) index it was possible to conclude that in sensitive halophytes (H. portulacoides, S. fruticosa and S. patens) the samples collected from the contaminated site produce had higher IBR values than the tolerant species S. maritima being these lower values linked with an adaptation mechanism towards contamination. Furthermore, the fatty acid-based IBR index was intrinsically connected with the bioavailable metals concentrations in the rhizosediments, which make that it could be used in future impact assessment and/or ecotoxicology studies. In summary, the data showed that two of the most abundant halophytes in the Mediterranean eco-region (S. fruticose and H. portulacoides) are potential sentinel species of metal contamination, whereas its fatty acid profile is an efficient biomarker of the degree of environmental contamination.
- Biophysical and Biochemical Markers of Metal/Metalloid-Impacts in Salt Marsh Halophytes and Their ImplicationsPublication . Anjum, Naser A.; Duarte, Bernardo; Caçador, Isabel; Sleimi, Noomene; Duarte, Armando C.; Pereira, EduardaAs a major sink, estuarine/salt marsh ecosystem can receive discharges laden with myriads of contaminants including metals/metalloids from man-made activities. Two among the major consequences of metal/metalloid-exposure in estuarine/salt marsh ecosystem flora such as halophytic plants are: (a) the excessive accumulation of light energy that in turn leads to severe impairments in the photosystem II (PS II), and (b) metal/metalloids-accrued elevation in the cellular reactive oxygen species (ROS) that causes imbalance in the cellular redox homeostasis. On one hand, plants adopt several strategies to dissipate excessive energy hence eventually to avoid damage in the PS II and maintain optimum photosynthesis. On the other hand, components of the cellular redox system quickly respond to metal/metalloid-exposure, where plants try to maintain a fine-tuning among these components, and tightly control the level of ROS and its potential consequences. Herein, major insights into, and the significance and implications of important biophysical and biochemical markers in metal/metalloid-exposed halophytes are overviewed and also highlighted main aspects so far least explored in the present context. Discussion advocates to regularly monitor and integrate studies on the highlighted herein biophysical and biochemical markers taking into account the missing aspects such as essential and non-essential metal/metalloid-speciation, -availability, and -methylation, role of the obvious microbial activities, and a comparative account of the outcomes of the studies on mixture of metal/metalloid performed in laboratory and field conditions. Thus, consideration of these missing aspects in future studies on the subject can help us to: (a) unveil the status of the metal/metalloid-contamination and -impact; (b) understand adaptive responses of salt marsh halophyte to metals/metalloids, and also (c) to devise sustainable strategies for the environmental or ecosystem management and safety.
- Ecophysiological constraints of Aster tripolium under extreme thermal events impacts: Merging biophysical, biochemical and genetic insightsPublication . Duarte, Bernardo; Goessling, J.W.; Marques, J. C.; Caçador, IsabelCold and heat waves are phenomenon that occurs in higher frequency and intensity due to global climate changes. Commonly cultivated crop species are crucially affected by extreme weather events, and therefore alternative crops - such as halophytes - gain in agricultural interest. While halophytes are potentially able to cope with temperature extremes on the long term exposure, effects of temporary events such as cold and heat waves are not yet described. In order to unveil the effects of these altered thermal environments, Aster tripolium plants were subjected to cold (9/5 °C) and heat (42/38 °C) waves regimes during 3 days and its photochemical and biochemical traits evaluated. In the potential cash crop A. tripolium cold waves induced the gene expression of dehydrins in order to counteract desiccation and thus to prevent oxidative stress. Regulatory proteins on the RNA maturation level (Maturase K) were highly expressed. Heat stress induced the gene expression of the cystein protease gene; most likely to degrade misfolded proteins temporary. Both thermal treatments decreased the photosynthetic efficiency and capacity, driven by a loss in the connectivity between PSII antennae. Nevertheless the light absorption capacity was unaffected due to an increased RC closure net rate. Cold wave-treated individuals showed a decrease in the carotenoid pigmentation, except auroxanthin. In cold wave treated individuals the overall peroxidase activity was significantly increased. Data suggest that exposure to both, cold and heat wave treatment decreased the ecophysiological capacity of A. tripolium.