a b s t r a c tAlthough essential for plants, copper can be toxic when present in supra-optimal concentrations. Metal polluted sites, due to their extreme conditions, can harbour tolerant species and/or ecotypes. In this work we aimed to compare the physiological responses to copper exposure and the uptake capacities of two species of duckweed, Lemna minor (Lm(EC1)) and Spirodela polyrrhiza (SP), from an abandoned uranium mine with an ecotype of L. minor (Lm(EC2)) from a non-contaminated pond. From the lowest Cu concentration exposure (25 M) to the highest (100 M), Lm(EC2) accumulated higher amounts of copper than Lm(EC1) and SP. Dose-response curves showed that Cu content accumulated by Lm(EC2) increases linearly with Cu treatment concentrations (r 2 = 0.998) whereas quadratic models were more suitable for Lm(EC1) and SP (r 2 = 0.999 and r 2 = 0.998 for Lm(EC1) and SP, respectively). A significant concentrationdependent decline of chlorophyll a (chl a) and carotenoid occurred as a consequence of Cu exposure. These declines were significant for Lm(EC2) exposed to the lowest Cu concentration (25 M) whereas for Lm(EC1) and SP a significant decrease in chl a and carotenoids was observed only at 50 and 100 M-Cu. Electric conductivity (EC) and malondialdehyde (MDA) content increased after Cu exposure, indicating oxidative stress. Significant increase of EC was observed in Lm(EC2) for all Cu concentrations whereas the increase for Lm(EC1) and SP became significant only after an exposure to 50 M-Cu. On the contrary, for Lm(EC1), SP, and Lm(EC2), MDA content significantly increased even at the lowest concentration. Protein content and catalase (CAT) activity showed a decrease with an increase in Cu concentration. For the species Lm(EC1) and SP, a significant effect of copper on CAT activity was observed only at the highest concentration (100 M-Cu) whereas, for Lm(EC2), this effect started to be significant after an exposure to 50 M-Cu. Superoxide dismutase (SOD) activity increased with increasing concentrations of Cu, with a very similar trend between the three populations of duckweed. However, due to the facts that enzyme activity is expressed as units of activity per gram of protein and that protein content decreased with Cu exposure, the increase in SOD activity might partly result from a relative increase of this enzyme inside the pool of proteins. Consequently, the results obtained in our experimental conditions strongly suggest that duckweed species from the uranium-polluted area have developed mechanisms to cope with metal toxicity and that this tolerance is based on the existence of protective mechanism to limit the metal uptake rather than on an enhancement of the antioxidative metabolism.

Since the early 1990s, an emerging disease induced by the highly aggressive oomycete Phytophthora 9alni has caused widespread alder decline across Europe. In parallel, P. lacustris, a recently described species associated with riparian habitats, has been subject of increasing interest. A field survey conducted in 2014 showed high mortality rates in alder stands located in the riparian gallery along two rivers in Central Portugal. The pathogens isolated from necrotic alder stem base during this study were identified as P. 9alni and P. lacustris. This paper is the first to report the occurrence of P. lacustris in Portugal and presents the first finding of P. 9alni affecting mature trees in natural ecosystems located in Central Portugal.

The exine morphology, with emphasis on the ultrastructure, of six genera and species of Ecliptinae was studied with transmission electron microscopy and scanning electron microscopy. A caveate exine with a single layer of columellae and predominantly circular to subcircular internal foramina (Helianthoid pattern of structure) is present in all the studied taxa and most probably in all the Ecliptinae. The morphologies of the internal foramina and foot layer are consistent within the Ecliptinae, and their potential taxonomic and phylogenetic relevance was discussed. The existence, for almost all the investigated characters and ratios, of a continuous gradient among the taxa, exists in the wedelioid group and constitutes a quite well defined parallelism between the exine data and those of the major clade of Ecliptinae (wedelioid group). The exine sculpture of the worldwide weed Eclipta prostrata (L.) L. presents some variation, which is, most probably, correlated to the existence of geographical clines and/or variations in its chromosome number. A mesoaperture concerning the foot layer and the upper part of the endexine exists in all the taxa studied and, presumably, in all the Ecliptinae, probably constituting a synapomorphy for all the Asteroideae and possibly for all the Asteraceae.