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Effectiveness of four free-floating macrophytes, Lemna minor, Lemna trisulca, Salvinia natans, and Azolla filiculoides, at accumulation of elements from polluted water and their usefulness in phytoremediation was determined. Concentrations of 14 elements were analyzed in plants and water from river affected by smelting industry. Under the same environmental conditions bioaccumulation ability of closely related species differed. The duckweed species contained more K, Mg, and Na than ferns; L. trisulca had higher concentrations of Co, Ni, and Zn (18.4, 13.0, 158 mg kg−1, respectively) than L. minor. S. natans characterized with the highest As, Cr, and Fe contents (27.1, 10.4, 15,475 mgkg−1, respectively). The overall bioaccumulation capability (metal accumulation index [MAI]) was ordered as follows: L. trisulca (2.33) > S. natans (1.91) > L. minor (1.50). All species studied were found to be accumulators of several metal(loid)s but L. trisulca distinguished by the highest bioaccumulation for Cd, Co, Cu, Mg, Na, Pb, and Zn, S. natans for As, Cr, Fe, Mn, and Ni, while L. minor for alkali cations. S. natans and both Lemna species may find application in phytoextraction, with L. trisulca as the best choice. A. filiculoides showed lower concentrations of trace metal(loid) than S. natans and L. trisulca.

The paper reports the finding of a new locality of Ophrys apifera – the first locality of this species in the Sudeten range and the second in Poland. A new population was found in the Kaczawskie Mts. (Western Sudetes). It consists of 23 flowering plants and occurs in an operating limestone quarry. The detailed data on this population and its habitat are included.

In climbing plants, fruits can be formed at different heights, depending on the height of external support. However, the effect of height on fruit and seed traits in invasive vines of Cucurbitaceae has not been intensively studied so far. In Europe, Echinocystis lobata, a North American member of Cucurbitaceae, is considered one of the most abundant invasive alien plants spreading in natural riparian forests, thickets, and tall herbs, whereas it is a rare species in urban woodlands. In this study, we tested the variability of selected fruit and seed traits of E. lobata in connection with habitat origin (natural, semi-natural, and anthropogenic), habitat type (using the EUNIS habitat classification), height (the distance between the fruit and the ground), and geographical position. The study was conducted in 2018 in 65 sites located in Latvia, Lithuania, Poland, and Slovakia. In each study site, a random sample of 10 fresh mature fruits of E. lobata was collected from subsequent 0.50 m intervals of height. The length, the width, and the weight of the fresh fruits, as well as the total number of seeds and number of undeveloped seeds per fruit, were examined. Moreover, the well-developed seeds from selected study sites were weighed. The statistical analysis showed the significant effect of habitat origin, habitat type, and height on most of the studied fruit and seed traits. The largest range of height (from 0.00 to 4.00 m) was observed in two types of habitats (F—heathland, scrub, and tundra; and G—woodland, forest, and other wooded land). The total number of seeds per fruit was positively correlated with the length, width, and weight of the fresh fruits. The fruits were a little heavier and bigger in natural habitats located in the northeast of the study area. The distribution of fruits at different heights may contribute to better dispersal of seeds by animals and wind, and may also better protect the seeds from being eaten by granivorous animals. The defence against seed-eating animals is expected to be stronger in semi-natural habitats, as well as on banks and shores of inland surface waters, where the seed production is the highest. The influence of seed traits on seed germination and seedling survival in various habitats and their importance in the invasiveness of E. lobata require further study.

International audience; Aim. Revisits of non‐permanent, relocatable plots first surveyed several decades ago offer a direct way to observe vegetation change and form a unique and increasingly used source of information for global change research. Despite the important insights that can be obtained from resurveying these quasi‐permanent vegetation plots, their use is prone to both observer and relocation errors. Studying the combined effects of both error types is important since they will play out together in practice and it is yet unknown to what extent observed vegetation changes are influenced by these errors. Methods. We designed a study that mimicked all steps in a resurvey study and that allowed determination of the magnitude of observer errors only vs the joint observer and relocation errors. Communities of vascular plants growing in the understorey of temperate forests were selected as study system. Ten regions in Europe were covered to explore generality across contexts and 50 observers were involved, which deliberately differed in their experience in making vegetation records. Results. The mean geographic distance between plots in the observer+relocation error data set was 24 m. The mean relative difference in species richness in the observer error and the observer+relocation data set was 15% and 21%, respectively. The mean “pseudo‐turnover” between the five records at a quasi‐permanent plot location was on average 0.21 and 0.35 for the observer error and observer+relocation error data sets, respectively. More detailed analyses of the compositional variation showed that the nestedness and turnover components were of equal importance in the observer data set, whereas turnover was much more important than nestedness in the observer+relocation data set. Interestingly, the differences between the observer and the observer+relocation data sets largely disappeared when looking at temporal change: both the changes in species richness and species composition over time were very similar in these data sets. Conclusions. Our results demonstrate that observer and relocation errors are non‐negligible when resurveying quasi‐permanent plots. A careful interpretation of the results of resurvey studies is warranted, especially when changes are assessed based on a low number of plots. We conclude by listing measures that should be taken to maximally increase the precision and the strength of the inferences drawn from vegetation resurveys.

Detailed analyses of micro- and macromorphological features of 247 specimens representing the Polypodium vulgare complex, combined with DNA content measurements, revealed the presence of tetraploid P. vulgare s.str., hexaploid P. interjectum and the pentaploid hybrid P. × mantoniae in the Polish Sudetes. For species identification, sporangium structure (number of indurated and basal annulus cells) was found to be the most stable and thus the most valuable and taxonomically significant character. The size of spores and stomata was related to taxon ploidy level, and helped to differentiate the examined taxa. Polypodium interjectum was identified from only one locality in the Pogórze Kaczawskie foothills; P. × mantoniae was more widely distributed, suggesting that it is rather common in the Polish Sudetes. Both newly reported taxa occur mainly on basic or neutral rock in sheltered, shaded or semi-shaded habitats.

Plant epiparasitism (hyperparasitism, secondary parasitism) is a known phenomenon in hemiparasitic mistletoe-like species of the Santalales (families Viscaceae, rarely Santalaceae and Eremolepiaceae), and vines of the genus Cassytha (Calvin and Wilson 2009). Dodder epiparasitism was recently reported when Cuscuta epithymoides was described parasitizing six hemiparasite plant species (Piwowarczyk et al. 2018). Our field surveys of the flora of the Widawa river valley (51°07′47″N, 17°07′45″E, Lower Silesia, southwest Poland), conducted in 2018, revealed the presence of two coexisting dodder populations, C. europaea and C. lupuliformis, covering the area of 900 m². Both analyzed dodder species are holoparasites devoid of roots and leaves and are characterized by following morphological traits. C. europaea is characterized by (i) stems 0.7 to 1 mm thick, up to 1 (1.4) m long, yellowish, reddish to purple, (ii) inflorescences lateral, compact, spherical, 7 to 10 mm long, with (3) 7 to 10 (18) flowers, (iii) flowers sessile, white to pinkish, 2.5 to 3 mm long, tetra (31%) or pentamerous, with two styles, stigma divergent, anthers hidden inside corolla, (iv) capsule globose, 1.4 to 2.4 mm long, with two to four seeds. C. lupuliformis is characterized by (i) stems 1.5 to 3.4 mm thick, up to 1.4 (1.8) m long, rust-green, yellowish to reddish, with protruding groups of purple-colored cells around stomata, (ii) inflorescences lateral, loose, racemose-spicate, up to 10 (12) cm long, with (5) 10 to 15 (22) small spikes composed of two to six flowers, (iii) flowers sessile to short pedicellate, white to pink, 3.5 to 5 mm long, pentamerous, with one style, stigma oval, anthers sessile, hidden, (iv) capsule conical, 4 to 7.4 mm long, with two seeds. The total genomic DNA of both species was extracted, and the internal transcribed spacer region was amplified and sequenced, using the ITS7A (Aguilar et al. 1999) and ITS4 (White et al. 1990) primers. The obtained sequences showed the highest similarity to C. europaea (99 to 100%, nearest: AY554401) and C. lupuliformis (96 to 99%, KU707914). The 614- and 604-bp sequences were deposited in GenBank (accession nos. MH973641 and MH973642, respectively). Anatomical analysis, utilizing a standard protocol for paraffin sectioning, confirmed the parasitic relationship between both holoparasites. Haustoria of C. europaea, penetrating stems of C. lupuliformis and connecting to its vascular tissues, were typically developed (Yoshida et al. 2016). We also observed autoparasitism in both taxa. Dodders are multihost obligate holoparasites, which suggests that their infesting mechanism is universal and adjustable to a particular host. As shown by our study, Cuscuta spp. can be also the host for other dodder species. This points to the lack of cellular and behavioral defense mechanisms protecting against attack of other dodders. To the best of our knowledge, this is the first report on dodder-dodder epiparasitism. Dodder species have dissimilar host and habitat requirements, accounting for their spatial isolation and the rarity of interactions. Habitats of the populations studied here partially overlap in river valleys, enabling occasional epiparasitism. In general, the parasites are more strongly affected by epiparasites than the autotrophs (Heide-Jorgensen 2008). Accordingly, C. lupuliformis is more severely affected than autotrophic hosts, and its stems dry out when parasitized by C. europaea. The dodder-dodder epiparasitism seems to be unprofitable for both species, the host and the parasite.

Pilularia globulifera is a subatlantic European fern threatened with extinction. In Poland, it reaches the eastern border of its continuous range. Up to the end of the 20th century, it was observed here in 21 stands; only 2 of them existed by the second half of the century, so the species was categorized as critically endangered. Five new locations have been found in western and northwestern Poland during the last 10 years. Abundant and permanent populations grow in 3 locations, while 2 stands were ephemeral. All the current stands are situated in anthropogenic habitats with spontaneous vegetation, in oligotrophic to eutrophic waters. One of the new localities is about 280 km distant from the eastern range of the limit known previously. Pilularia forms its own plant community Pilularietum globuliferae, enters plots of Ranunculo-Juncetum bulbosi and occurs in mesotrophic to eutrophic rushes of Eleocharis palustris, Phragmites australis, Typha angustifolia and Equisetum fluviatile. Specimens are vigorous and regularly produce sporocarps.