Cristina Branquinho

High nickel (Ni) levels exert toxic effects on plant growth and plant water content, thus affecting photosynthesis. In a pot experiment, we investigated the effect of the Ni concentration on the physiological characteristics of the Ni hyperaccumulator Alyssoides utriculata when grown on a vermiculite substrate in the presence of different external Ni concentrations (0-500 mg Ni L(-1)). The results showed that the Ni concentration was higher in leaves than in roots, as evidenced by a translocation factor = 3 and a bioconcentration factor = 10. At the highest concentration tested (500 mg Ni L(-1)), A. utriculata accumulated 1100 mg Ni per kilogram in its leaves, without an effects on its biomass. Plant water content increased significantly with Ni accumulation. Ni treatment did not, or only slightly, affected chlorophyll fluorescence parameters. The photosynthetic efficiency (FV/FM) of A. utriculata was stable between Ni treatments (always ≥ 0.8) and the photosynthetic performance of the plant under Ni stress remained high (performance index = 1.5). These findings support that A. utriculata has several mechanisms to avoid severe damage to its photosynthetic apparatus, confirming the tolerance of this species to Ni under hyperaccumulation.

En numerosos estudios se confirma que una limitada capacidad dispersiva representa un importante hándicap para el recluta-miento demográfico y la continuidad de las poblaciones, en par-ticular para las dinámicas que tienen lugar tras los cambios cli-máticos del último siglo. Los riesgos de extinción se magnifican cuando la dimensión de la población es muy pequeña (Thomas et al., 2004). Ésta es el caso de Plantago almogravensis Franco, especie endémica, actualmente reducida a una única pequeña población natural, fraccionada en núcleos dispersos en una área total inferior a 3 hectáreas. Con una población estimada en el censo de 2006 entre 3000-4000 individuos, esta población está marcada por bajas tasas de reclutamiento de juveniles, mientras que la continuidad se basa en la prolongada longevidad de los adultos reproductivos (Pinto et al., 2004). En el final del proyecto "Plano Nacional de Conservação da Flora em Perigo" conducido por la autoridad portuguesa para la conserva...

The physiological ability of plants to cope with Al-toxicity has attracted considerable attention. In this study we used an endemic Al-hyperaccumulator plant, Plantago almogravensis, which is the only known representative of the Plantaginaceae with this trait growing under a field gradient of Al, to understand the root and shoot patterns of Al accumulation and tolerance in its natural environment. We analysed phytoavailable elements in the soil and their accumulation in the plant. For the first time under field conditions, the accumulation pattern of an Al-hyperaccumulator showed a saturation curve with a maximum accumulation capacity being reached (ca. 3.0 mg g− 1). The Al toxicity was not associated with the expected reduction in the Ca and Mg uptake by the plant. Iron was accumulated in a more linear pattern. The magnitude and the proportion of the elements found in the apoplastic fraction of the root, compared to the soil and plant internal fractions, suggested that the control of uptake occurs at the rhizospheric level. Unlike the majority of the Al-hyperaccumulator plants that are found in tropical humid areas, this plant is described from a sub-arid Mediterranean climate, subject to drought conditions which give it a unique status that deserves to be studied further.► Plantago almogravensis is an obligate metallophyte for Al. ► It only grows in sub-arid Mediterranean climate being the only Plantaginaceae described hyperaccumulating Al. ► The plant accumulates Al up to a maximum capacity, showing a saturation curve. ► Al toxicity is not associated with reduction in the Ca and Mg uptake by the plant. ► The control of Al uptake to the plant is suggested to occur at the rhizospheric level.

Anthropogenically derived nitrogen (N) has a
central role in global environmental changes, including
climate change, biodiversity loss, air pollution, greenhouse
gas emission, water pollution, as well as food production
and human health. Current understanding of the biogeochemical
processes that govern the N cycle in coupled
human–ecological systems around the globe is drawn
largely from the long-term ecological monitoring and
experimental studies. Here, we review spatial and temporal
patterns and trends in reactive N emissions, and the
interactions between N and other important elements that
dictate their delivery from terrestrial to aquatic ecosystems,
and the impacts of N on biodiversity and human society.
Integrated international and long-term collaborative studies
covering research gaps will reduce uncertainties and
promote further understanding of the nitrogen cycle in
various ecosystems.

Abstract Background and Aims The aquatic moss Fontinalis antipyretica requires a slow rate of dehydration to survive a desiccation event. The present work examined whether differences in the dehydration rate resulted in corresponding differences in the production of reactive oxygen species (ROS) and therefore in the amount of cell damage.