<em>Laserpitium pseudomeum</em> is an endemic umbellifer of Greece occurring in the mountains of Sterea Ellas and northern Peloponnese. Molecular data indicate that it is not related to its putative congeners, but instead constitutes an isolated lineage. The nuclear ribosomal DNA ITS tree places it as a weakly supported sister group to <em>Portenschlagiella ramosissima</em>, the sole species in its genus, whereas the tree inferred from three noncoding cpDNA loci does not confirm this relationship. <em>Portenschlagiella ramosissima</em> is sometimes placed in <em>Athamanta</em>, an affinity supported neither by molecular data nor by fruit morphology. <em>Laserpitium pseudomeum</em> notably differs from <em>P. ramosissima</em> in vegetative, flower, and fruit characteristics, and no obvious morphological synapomorphies indicate their close relationship. Therefore, we place <em>L. pseudomeum</em> in the newly described genus <em>Laserocarpum</em> and lectotypify the species with the specimen <em>Orphanides 2019</em> (G00766460) at G-Boiss.

This paper describes the vertical and horizontal distribution, habitat preferences, threats, and conservation status of <em>Trichocolea tomentella</em> in the Polish Carpathians based on the analyses of 138 localities. The species prefers wetland habitats, mostly within forests, such as areas in the vicinity of springs (34% stands), stream banks (32%), wet parts of the forest floor (20%), and mountain bogs (16%). As a consequence of the decrease in the areas of these habitat types, localities of <em>T. tomentella</em> are threatened with extinction. Therefore, according to the IUCN standards, this species should be placed in the near threatened (NT) category in the Polish Carpathians.

In the geobotanical division of Poland, Pomerania was treated as a separate subdivision, divided into “coastal plains” and the “Pomeranian uplands” or, in the newest regionalization, the “Pomeranian division”. The goal of this paper is to determine how well the distinctiveness of Pomerania is floristically justified. A total of 1,467 native species occur within the area of Pomerania, representing 57.5% of the native flora of Poland. Fifty-seven species distinguishing Pomerania were selected and their phytogeographic features were discussed and compared to the Polish vascular flora. The distribution of 32 species (56.1%) is characterized as (sub)Atlantic/oceanic. Of the taxa that characterize Pomerania, 47.45% represent the northern element of the Polish flora and 7.01% the western element; species of the eastern element do not exist in Pomerania. The maximum entropy (MaxEnt) method was used for collective distribution analysis of the 57 selected taxa. The analyzes were performed using 41 environmental variables. All the species analyzed are strictly linked to the western and the North Atlantic part of Europe. Statistical evaluation of the MaxEnt model yielded an AUC value of 0.75 for both training and test. The most important environmental variables are minimum high (min_h), temperature annual range (bio07), and mean temperature of driest quarter (bio09). The results of the MaxEnt analysis allowed us also to verify the boundaries of the region and suggest new criteria for them. The southern limit of Pomerania should run along the northern boundary of the terminal moraine belt. Also, the area east of the Vistula does not contain abundant representatives of the flora characteristic for Pomerania. The results of the present study may be used for a broader discussion on the revision of the geobotanical division of Poland, at least in its northern part.

Floral nectar is one of the key rewards in the mutualistic interactions between plants and pollinators. However, there is a growing amount of evidence that shows that another group of organisms may be involved in the pollination process, namely the microorganisms, which often inhabit floral nectar. However, little is known about the function and taxonomic diversity of microorganisms inhabiting the nectar of plants. Bacterial communities inhabiting nectar of a rare plant species, <em>Polemonium caeruleum</em>, in one artificial and two natural populations in Poland were analyzed using a metagenomic approach. <em>Polemonium caeruleum</em> is a boreal plant species, and requires appropriate pollinator services for seed production. The reproductive system of this plant may vary between individuals and populations (mixed-mating), as well as with insect visitor assemblages. We considered that nectar-dwelling bacteria of <em>P. caeruleum</em> might affect the insects visiting the plant’s flowers, which in turn can result in changes in the plant’s phenotype and its reproductive system. Bacterial diversity in nectar samples was surveyed using culture-independent 16S rRNA gene amplicon sequencing (MiSeq, Illumina). We found that bacterial communities inhabiting the nectar of <em>P. caeruleum</em> differed between populations, although those differences were mostly quantitative. Many of the identified bacterial genera have been found previously in nectar of other plant species, or in the guts of insect visitors, and are described as tolerant of high sugar concentrations and catalase positive (which allows bacteria to survive in the presence of hydrogen peroxide).

Grasslands provide wide range of ecosystem services, however, their area and quality are still diminishing in Europe. Nowadays, they often create isolated patches inside “sea” of other habitats. We have examined basic structural landscape metrics of grasslands in Poland using CORINE land use database. Characteristics for both all individual patches as well as average values for 10 × 10-km grid covering Poland were examined. We also assessed the percentage of grasslands within protected areas and ecological corridors. We found that in Poland rather small patches (0.3–1 km<sup>2</sup>) dominate, usually located 200–500 m away from each other. The grasslands had clumped distribution, thus in Poland exist large areas where grasslands patches are separated kilometers from each other. Almost all indices calculated for 10 × 10-km<sup>2</sup> were correlated, i.e., in regions with high percentage of grasslands, the patches were large, more numerous, placed close to each other, and had more irregular shapes. Our results revealed that the percentage of grasslands within protected areas and ecological corridors did not differ from the average value for Poland. On the other hand, forests were significantly over-represented in protected areas and ecological corridors. These findings suggest that there is no planned scheme for grassland protection at the landscape scale in Poland. Development the scheme is urgent and needs high-quality data regarding distribution of seminatural grasslands patches. In practice, nature conservationists and managers should consider spatial processes in their plans in order to maintain grassland biodiversity.

One of the first steps to successful invasion of plant species that reproduce sexually is seed germination, which may be highly influenced by climatic conditions. We studied <em>Poa annua</em>, a cosmopolitan species found across all climatic zones and the only alien species that has successfully colonized the Antarctic. Our research questions were: (i) if harsh polar conditions restrict seed germination of <em>P. annua</em> and (ii) if the germination capacity of the Antarctic population of the species is due to high germination aptitude in the source population. We compared germination of seeds collected from eight populations around the world (maritime Antarctica, S Chile, W Argentina and E Argentina, NE USA, SW Croatia, C Poland and S Poland). We followed germination of seeds collected in the field and acquired from plants cultivated under unified optimal conditions. We found significant differences between populations in germination characteristics of seeds collected in the field. These could be associated with seed ripening in different locations. Seeds obtained under favorable conditions differed in stratification requirements. The germination potential of the Antarctic population is lowered by unfavorable polar conditions impacting seed maturation. Thus, the species’ invasion in the Antarctic seems highly restricted by the harsh environment. Environmental unsuitability may restrict invasions of other species in the same way potentially. However, this environmental barrier protecting Antarctica from invasions may be broken under a climate warming scenario.

In recent years, several studies have focused on the factors and mechanisms that regulate plant growth and development, as well as the functioning of signaling pathways in plant cells, unraveling the involvement of sugars in the processes regulating such growth and development. Saccharides play an important role in the life of plants: they are structural and storage substances, respiratory substrates, and intermediate metabolites of many biochemical processes. Sucrose is the major transport form of assimilates in plants. Sugars can also play an important role in the defense reactions of plants. However, it has been shown that glucose, sucrose, or trehalose-6-phosphate (Tre6P) can regulate a number of growth and metabolic processes, acting independently of the basal functions; they can also act as signaling molecules. Changes in the concentration, qualitative composition, and transport of sugars occur continuously in plant tissues, during the day and night, as well as during subsequent developmental stages. Plants have developed an efficient system of perception and transmission of signals induced by lower or higher sugar availability. Changes in their concentration affect cell division, germination, vegetative growth, flowering, and aging processes, often independently of the metabolic functions. Currently, the mechanisms of growth regulation in plants, dependent on the access to sugars, are being increasingly recognized. The plant growth stimulating system includes hexokinase (as a glucose sensor), trehalose-6-phosphate, and TOR protein kinase; the lack of Tre6P or TOR kinase inhibits the growth of plants and their transition to the generative phase. It is believed that the plant growth inhibition system consists of SnRK1 protein kinases and C/S1 bZIP transcription factors. The signal transduction routes induced by sugars interact with other pathways in plant tissues (for example, hormonal pathways) creating a complex communication and signaling network in plants that precisely controls plant growth and development.

The sharing of species of ectomycorrhizal fungi (EMF) among different co-occurring host plant species could allow the formation of common mycorrhizal networks, which can alter plant–plant interactions and succession. Such sharing of EMF among woody species is thought to be common in many forests, but very few herbaceous plants form EMF, so they are assumed to be excluded from EMF networks in forests. We studied the EMF on roots of a common coniferous tree, <em>Pinus sylvestris</em>, and a co-occurring rare herbaceous perennial plant, <em>Pulsatilla patens</em> (Ranunculaceae), in northeastern Poland. We examined roots from co-occuring <em>P. sylvestris</em> and <em>P. patens</em>, visually classified EMF into morphotypes, studied tissue sections of mycorrhizal structures using compound microscopy, and used DNA sequencing to identify the fungi. On both host plant species, we observed EMF colonization, with colonized root tips exhibiting a swollen appearance, as well as a variety of colors and textures of fungal mycelium covering and emanating from those swollen tips. Sectioning and microscopic examination of an EMF morphotype common on <em>P. patens</em> confirmed the presence of a mantle and Hartig net, indicating the likely presence of functional ectomycorrhizal structures. The two most frequent EMF were <em>Cenococcum geophilum</em> and <em>Piloderma olivaceum</em>, and the latter was found to associate with both host plant species. Several EMF found here only on <em>P. patens</em>, including <em>C. geophilum</em> and two <em>Russula</em> species, are known from previous studies to also associate with <em>P. sylvestris</em> and other tree species. The observation of shared EMF between a coniferous tree and an understory herb indicates the potential for common mycorrhizal networks to alter interactions between these two species and may also indicate a unique way in which the distribution and abundance of a rare herbaceous plant may be influenced by shared mutualisms with a common co-occurring woody plant.

The macroscopic and microscopic morphologies and indigo and indirubin concentration of the traditional Chinese medicine herbs <em>Isatis indigotica</em> Fort., <em>Polygonum tinctorium</em> Ait., and <em>Baphicacanthus cusia</em> (Nees) Bremek, all commonly known as “daqingye”, were determined and compared. The morphological analyses indicated that <em>I. indigotica</em> has leaves with winged petioles and no glandular hairs or crystals, <em>P. tinctorium</em> has leaves with membranous ocrea and clusters of calcium oxalate, and <em>B. cusia</em> has palisade cells in the mesophyll running over the main vein and single cells containing calcium carbonate crystals. Indigo and indirubin are chemical constituents that have been previously isolated from daqingye and were selected in this study as identification markers for high-performance liquid chromatography analysis due to their pharmacological activities. The chromatographic results showed that indigo and indirubin concentration varied significantly among the three species: high concentration of both indigo and indirubin were observed in <em>I. indigotica</em>, the highest concentration among the three daqingye plants was found in <em>P. tinctorium</em> but with low levels of indirubin, and the concentration of indigo and indirubin was quite low in <em>B. cusia</em>. In summary, three different species commonly known as daqingye were accurately distinguished by morphological observation, internal leaf anatomy analysis, and chromatographic analysis.

We studied the effect of differential phosphorus (P) supply on the development of oat seedlings (<em>Avena sativa</em> L. ‘Arab’) as well as localization and activity of acid phosphatases in tissues and root exudates. Plants were grown for 1–3 weeks on nutrient media with inorganic phosphate (+P, control), reduced Pi (0.1 P), phytic acid (PA) as organic P source, and without P addition (−P), in standard conditions or in a split-root culture system. Phosphate starvation reduced shoot growth but increased root elongation and root/shoot ratio, whereas 0.1 P and PA oat plants had similar growth parameters to +P plants. The growth on −P medium significantly decreased Pi content in all tissues, but only a slight Pi decrease was observed in plants grown on 0.1 P and PA media or various split-root system conditions. Pi starvation led to an increase in acid phosphatase (APase) activity in root exudates when compared to +P, 0.1 P, and PA plant samples. APase activity was especially intensive in root cross sections in rhizodermis and around/in vascular tissues of −P plants. For plants grown on 0.1 P medium and on phytic acid, APase activity did not change when compared to the control. Three major isoforms of APases were detected in plant tissues (similar in all studied conditions, with a higher activity of one isoform under Pi deficit). Generally, lowered Pi content (0.1 P) was not stressful to oat plants for up to 3 weeks of culture. Oat plants grew equally well on nutrient media with Pi and on media with phytate, although phytate was considered not available for other plants. The oat plants activated mainly extracellular APases, but also intracellular enzymes, rather via nonlocal signals, to acquire Pi from external/internal sources under Pi deficiency.