Helena Cristina Serrano

How does an Al-hyperaccumulator plant respond to a natural field gradient of soil phytoavailable Al?

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.

Nickel phytoremediation potential of the Mediterranean Alyssoides utriculata (L.) Medik.

This study investigated the accumulation and distribution of nickel in the leaves and roots of the Mediterranean shrub Alyssoides utriculata to assess its potential use in phytoremediation of Ni contaminated soils. Total (AAS and ICP-MS) Ni, Ca and Mg contents were analyzed in the plants and related to their bioavailability (in EDTA) in serpentine and non-serpentine soils. To find the relationships between the soil available Ni and the Ni content of this species, we also evaluated possible interactions with Ca and Mg. The bioaccumulation factor (BF) and the translocation factor (TF) were determined to assess the tolerance strategies developed by A. utriculata and to evaluate its potential for phytoextraction or phytostabilization. The leaf Ni is higher than 1000 μg g(-1) which categorizes the species as a Ni-hyperaccumulator and a great candidate for Ni-phytoextraction purposes. In addition to the accumulation of Ni, the leaf Mg is also correlated with soil bioavailable concentrations. The Ca uptake and translocation were significantly lower in serpentine plants (higher Ni), as such, the leaf Ca is probably greatly influenced either by the soils Ni or the soil Ca/Mg ratio. The BFs and TFs are strongly higher than 1 and generally did not significantly differed between plants from serpentine (higher Ni) and non-serpentine soils (lower Ni). The present study highlights for the first time that A. utriculata could be suitable for cleaning Ni-contaminated areas and provides a contribution to the very small volume of data available on the potential use of native Mediterranean plant species from contaminated sites in phytoremediation technologies.

Mapping Exposure to Multi-Pollutants Using Environmental Biomonitors—A Multi-Exposure Index

ABSTRACT Atmosphere is a major pathway for transport and deposition of pollutants in the environment. In industrial areas, organic compounds are released or formed as by-products, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F’s). Inorganic chemical elements, including lead and arsenic, are also part of the pollutants mixture, and even in low concentrations may potentially be toxic and carcinogenic. However, assessing the spatial pattern of their deposition is difficult due to high spatial and temporal heterogeneity. Lichens have been used as biomonitors of atmospheric deposition, because these organisms encompass greater spatial detail than air monitoring stations and provide an integration of overall pollution. Based upon the ability of lichens to concentrate pollutants such as PCDD/F and chemical elements, the main objectives of this study were to develop a new semi-quantitative multi-pollutant toxicity exposure index (TEQ-like), derived from risk estimates, in an attempt to correlate several atmospheric pollutants to human exposure levels. The actual pollutant concentrations were measured in the environment, from biomonitors (organisms that integrate multi-pollutants), enabling interpolation and mapping of contaminant deposition within the region. Thus, the TEQ-like index provides a spatial representation not from absolute accumulation of the different pollutants, but from the accumulation weighted by their relative risk. The assessment of environmental human exposure to multi-pollutants through atmospheric deposition may be applied to industries to improve mitigation processes or to health stakeholders to target populations for a comprehensive risk assessment, epidemiological studies, and health recommendations.

Metal hyperaccumulation patterns within Plantago phylogeny (Plantaginaceae)

AimsWe aimed to evaluate the presence of the metal hyperaccumulation trait in the phylogeny of Plantago with emphasis on P. subgen. Coronopus. Considering that P. almogravensis is an Al-hyperaccumulator and that phylogenetic links have been described for other Al-hyperaccumulators, we hypothesized that we would find more Plantago taxa with this accumulation trait. We also enquired if other metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn), follow a similar accumulation pattern as Al.MethodsWe analysed metal accumulation data from direct (analyses) and indirect sources (bibliographic) combined with phylogenetic analysis.ResultsRegarding metal accumulation, our results indicate a high probability of hyperaccumulation in Plantago species (nine out of 15 species), namely for the metals Al (6–8), Cu (1), Zn (2–3) and Pb (1). There are also records of Fe (5) considered abnormally high. For P. subgen. Coronopus, hyperaccumulation was perceived in six out of seven species. In particular for Al-hyperaccumulation, a high frequency and dispersion among Plantago sub-ranks is compatible with a phylogenetic relation.ConclusionsOur work suggests that the Al-hyperaccumulation trait is common in Plantago, especially in P. subgen. Coronopus, and contributes to the scarce knowledge of that uncommon trait, namely in Mediterranean plants.

Measuring and mapping the effectiveness of the European Air Quality Directive in reducing N and S deposition at the ecosystem level

To protect human health and the environment (namely ecosystems), international air quality protocols and guidelines, like the Gothenburg protocol (1999) and the 2001 EU Air Quality Directive (NECD), conveyed national emission ceilings for atmospheric pollutants (Directive 2001/81/EC), including the reduction of sulfur (S) and nitrogen (N) emissions by 2010. However, to what degree this expected reduction in emissions had reflections at the ecosystem level (i.e. pollutant levels reaching and impacting ecosystems and their organisms) remains unknown. Here, we used lichens as ecological indicators, together with reported air and precipitation pollutant concentrations, to determine and map the consequences of the S and N atmospheric emissions reduction, during the implementation of the 2001 Directive (in 2002 and 2011), due primarily to the industrial-sector. The study area is a mixed-land-use industrialized Mediterranean agroforest ecosystem, in southwest Europe. The reduction of S emissions (2002-2011) was reflected at the ecosystem level, as the same S-declining trend was observed in atmospheric measurement stations and lichens alike (-70%), indicating that most S deposited to the ecosystem had an industrial origin. However, this was not the case for N with a slight N-reduction near industrial facilities, but mostly N-deposition in lichens increased in areas dominated by agricultural land-uses. Taken together, these results highlight the importance of going beyond emissions estimation and modeling, to assess the success of the implementation of the NECD in lowering pollutant accumulation in living organisms and their environment. This can only be achieved by measuring pollutant deposition at the ecosystem level (e.g. living organisms). By doing so, we were able to show that the 2001 NECD was successful in reducing S concentrations from Industry, whereas N remains a challenge. Despite the small reduction in N-emissions, deposition into ecosystems did not reflect these changes as agriculture and transport sectors must reduce NH3 and NOx emissions.

Effect of cadmium accumulation on the performance of plants and of herbivores that cope differently with organic defences

Some plants can accumulate in their shoots metals that are toxic to most other organisms. This ability may serve as a defence against herbivores. Although both metal accumulation and the production of organic defences may be costly to the plant, the two mechanisms may interact on their effect on herbivores. However, this interplay between metal-based and ‘classical’ organic defences remains overlooked. To fill this gap, we studied the interactions between tomato (Solanum lycopersicum), a plant that accumulates cadmium, and two spider-mites, Tetranychus urticae and T. evansi that respectively induce and suppress organic plant defences, measurable via the activity of trypsin inhibitors. We exposed plants to different concentrations of cadmium and measured their effect on mites and plants. The oviposition of both spider-mite species was higher on plants exposed to low concentrations of Cd than on control plants but decreased at concentrations above 0.5 mM. Therefore, herbivores with contrasting responses to organic defences responded similarly to metal accumulation by the plants. On the plant, despite clear evidence for Cd accumulation, we did not detect any effect of Cd on traits that reflect the general response of the plant, such as biomass, water content and carbon/nitrogen ratio. Still, we found an effect of Cd supply upon the quantity of soluble sugars and leaf reflectance changes that may reflect structural modifications in the cells. In turn, these changes in plant traits interfered with the performance of spider mites feeding on those plants. Additionally, we show that the induction and suppression of plant defences by spider mites was not affected by Cd supply to the plants. Furthermore, the effect of metal supply on spider-mite performance was not affected by previous infestation. Together, our results suggest no interaction between metal-based and organic plant defences, on our system. This may be useful for plants living in heterogeneous environments, as they may use one or the other defence mechanism, depending on their relative performance in each environment. This may be relevant to studies on the interactions between herbivores and plants, from physiology to ecology.