Size characteristics of mature cones (berries) and seed quality were studied at the individual berry level in three Juniperus taxa indigenous to Slovakia. The globose berries were characteristic of J. communis subsp. communis and J. communis nothovar. intermedia and ovoid berries of J. communis subsp. nana. All three taxa had smaller berries than those of the corresponding species in other countries. In five populations of the studied taxa, three-seeded berries were the most frequent, with one population of J. communis subsp. communis being exceptional, producing predominantly two-seeded berries. The average number of seeds per berry has ranged from 2.06 to 2.94 in J. communis subsp. communis depending on locality. In J. communis nothovar. intermedia it was 2.40 seeds per berry, whereas in J. communis subsp. nana 2.81 seeds per berry. Of these, the fraction ranging between 0.033 and 0.67 represented filled seeds, and the fraction between 1.35 and 1.88 aborted seeds. Cytological study of seed development dynamics revealed an abrupt decline of the viability seed potential at the prezygotic stage of fertilization process in J. communis subsp. communis and a smaller extent of deterioration of morphologically differentiated embryos and encompassing gametophyte of mature seeds. Cytological illustrations of these disturbances in fertilization process are presented and discussed in the paper.

Needle structure was analyzed in three Juniperus communis taxa from different localities in central Slovakia. The main aim was to test the hybrid origin hypothesis of J. communis nothovar. intermedia (Schur) Nyman, defined as a cross between J. communis L. ssp. communis and J. communis ssp. nana (Hook.) Syme. While DNA-based analyses remain the most reliable tool for inferring evolutionary history, comparative needle morphology can provide complementary evidence, including diagnostic traits for taxonomic delimitation. In this study, we evaluated three morphometric and sixteen anatomical needle traits, measured via microscopy in ten shrubs per taxon. The analyses indicated that most traits in nothovar. intermedia matched one of the parents, with only two traits proving strongly diagnostic, separating all three taxa: needle length, which showed an intermediate mean phenotype in nothovar. intermedia (R2 = 0.824, p = 0.011; between parents), and vascular bundle height, which displayed a transgressive pattern (R2 = 0.552, p = 0.031; between parents). Although the diagnostic value of individual traits for hybrid detection was generally weak, a phylogenetic network analysis based on six diagnostic traits that separated individuals of the parental taxa provided evidence for reticulate evolution. These results support the hybrid origin of J. communis nothovar. intermedia and highlight needle traits with potential value for distinguishing ssp. communis and ssp. nana in natural populations, which may assist in taxonomic delimitation and inform future conservation assessments.

Pollen viability in three Juniperus taxa native to Slovakia was investigated using in vitro germination test. The highest germination percentage and longest pollen tubes were surprisingly found in J. communis var. intermedia which is believed to be a putative hybrid between J. communis var. communis and J. sibirica . Germination rate of the hybrid averaged at 78.70% as compared with 64.96% and 60.83% of the pollen germination in the corresponding parental species. The same tendency holds for the pollen tube length reaching 38.68 µm in the putative hybrids, 31.39 µm in J. communis var. communis and 28.08 µm in J. sibirica . At the taxa level, the above given data were statistically highly significant in both pollen viability characteristics. Highest viability of J. communis var. intermedia pollen does not corroborate the widespread notion on reduced fertility of the plant interspecific hybrids. Additional tests are suggested to verify the hybrid nature of the putative hybrid population using DNA based population study and artificial crossing experiments involving the putative parental species J. communis var. communis and J. sibirica .

Common sunflower (Helianthus annuus L.) belongs to the group of crops with high biomass and high capacity for the accumulation of various metals. Previous studies have suggested that remedial potential is strongly determined by genotype. In our study, we evaluated the tolerance of six sunflower hybrids (P64HE118, P64LE136, P62LE122, P64HE133, P64HE144 and P63LP25) to cadmium ions (Cd 100 mg kg−1 soil), and we also evaluated their remediation potential. All tested hybrids showed high tolerance to Cd, no significant changes were noted with regard to growth, content of photosynthetic pigments, leaf area, water content, proline content, or accumulation of superoxide dismutase (SOD) isoforms. We noted an increased rate of membrane lipid peroxidation for P64HE118, P64LE136 and P64HE144 hybrids. The increased content of glutathione in the leaves of P64HE118 and P64LE136 hybrids indicates this molecule's involvement in the Cd detoxification process. All hybrids accumulated Cd preferentially in the roots. The most Cd was accumulated in the roots and shoots of hybrid P64HE118. Values of bioaccumulation factor and translocation factor were hybrid-dependent, being generally higher for standard/control soil (Cd 1.2 mg kg−1 soil). Better phytoremediation potential of these hybrids can hence be expected at lower Cd doses in the soil. The high tolerance of tested hybrids to a higher dose and the non-negligible accumulation of Cd in roots also supports using these hybrids in soil phytostabilisation.

Pollen viability, dispersion ability and longevity during deep-freezer storage were studied in three Juniperus taxa distributed in Slovakia. All these characteristics of pollen are closely related to the pollination and/or fertilization success of the junipers in nature. Pollen viability varied considerably between the three populations of J. communis and one population of each, J. sibirica and J. communis var. intermedia. Pollen germination rate ranged between 40.75% and 75.06%, and pollen tube length between 30.32 and 40.41 µm. A clear tendency indicates a higher germination rate of J. communis pollen from lower altitudes and reduced germination of J. sibirica and J. communis var. intermedia pollen from higher altitudes. The dispersion potential of the J. communis pollen during its shedding seems relatively low. In 2021, pollen cloud density was diluted at 68.1% at the 4 m distance from the test shrub, in 2022 of 52.1% at the 17 m distance from the pollen source. A deep-freezer storage of juniper pollen in a double-walled polyethylene bag with silica gel was not efficient enough, as indicated by the drop of pollen germination rate of 31.2% in J. communis and of 79.4% in J. sibirica during a 1-year storage period at − 81 °C.

Due to the COVID-19 pandemic, there has been a significant shift from traditional, in-person teaching to online education, which has become indispensable. Nowadays, online learning is increasingly popular, encompassing educational programs delivered exclusively through digital platforms like video conferences and virtual classrooms. The flexibility of online education allows students to learn at their own pace and according to their schedule, but it also poses potential disadvantages. In this article, we explore the impact of online teaching on the practical subject of biology and students’ perceptions of education in primary, secondary, and tertiary schools in Slovakia. Our research focuses on evaluating the progress of online biology teaching, examining methods of knowledge testing, and assessing both the positives and negatives.

Although changes in stomatal response to elevated doses of cadmium has already been observed in several plants, few studies have focused on this phenomenon in more detail. The effects of different doses of cadmium Cd2+ (50 and 100 mg.kg(-1) soil) on leaf area and stomatal characteristics (number of stomata, number of epidermal cells, stomatal index and size of stomata) of faba bean (Vicia faba L. cultivar Astar) were studied after 15 days of heavy metal treatment. No visual changes on adaxial or abaxial side of leaves of the tested variety of faba bean were found. The leaf area was higher by 14.15 % at lower and by 12.23 % at the higher doses of Cd. The tested doses of Cd did not lead to a change in the number of stomata. The number of epidermal cells was increased on adaxial side by 4.98 % at dose Cd50. Stomatal index was decreased due to the effect of higher dose of cadmium by 11.38 % on adaxial side of leaves. In stomatal widths, decrease by 2.04 % (adaxial side) and 2.26 % (abaxial side) was observed at higher doses of Cd. In stomatal length decrease by 1.85 % was observed at higher dose of Cd on adaxial and decrease by 3.89 % (Cd50) and 4.63 % (Cd100) on abaxial side of leaves respectively. The variations of response could be signals of tolerance or adaptive mechanisms of the leaves of tested bean cultivar under the used concentrations of cadmium.

Pollen storage belongs among the most important activities associated with pollen handling. It overcomes the differences in pollen shedding and ovule receptivity during controlled pollination experiments. It is especially important for species like common juniper ( Juniperus communis L.) with an extremely low quality of seeds due to pollination failure. Additionally, it is a substantial part of germplasm preservation programmes in pollen banks. In the present paper, the effect of short-term storage of pollen was studied using pollen samples from five shrubs in an in vitro germination test. Two temperature regimes were tested. The pollen viability of freshly collected pollen varied considerably between individual shrubs, exhibiting 67.3–88.6% germination rate and 248.0–367.3 µm of pollen tubes. Storage at + 4 °C for four months was accompanied by a profound decline in pollen viability. The germination percentage was reduced to 49.2–75.2% and the pollen tube length to 32.5–69.0%, depending on individual shrubs. The corresponding decline in pollen viability characteristics during storage at − 20 °C was only negligible in two of the tested shrubs. In the remaining three shrub samples, an increase in germination percentage was observed. Pollen tube growth responded more sensitively to freezing, but, on average, the decrease in length was lower than that at + 4 °C. The rate of reduction in pollen tube length varied between 11.5 and 45.4%. Cytological events accompanying in vitro germination of freezer-stored pollen exhibited some delay in releasing the exine from pollen grains during the early stages of germination as compared with freshly collected pollen. In conclusion, short-term storage of the common juniper pollen in a freezer is better for the preservation of its viability than storage at + 4 °C.

Artificial hybridization experiment with the Pinus sylvestris and Pinus mugo putative hybrid individuals and their parents revealed a selective nature of their crossability conditioned by the identical chloroplast DNA (cpDNA) haplotypes of the crossed individuals. Efficiency of hybridization between hybrid individual H1 of P. sylvestris haplotype and P. sylvestris paternal tree was relatively high, as evidenced by 78.03% of filled seeds. On the contrary, the crossing of H1 individual with P. mugo was unsuccessful. Likewise, the crossability of the H2 individual of P. mugo haplotype with the paternal tree P. mugo resulted in 31.15% of filled seeds. A relatively high crossability was characteristic also for the H1 and H2 hybrid trees of different cpDNA haplotypes. A conclusion has been drawn postulating weakened reproduction barrier between hybrid swarm individuals and the paternal species P. sylvestris and P. mugo. Differentiation of the putatively hybrid individuals from the parental species is accompanied by the variation in cpDNA inheritance.

Pollen storage is the only way how to overcome the differences in phenology of forest trees and geographically determined reproductive barriers between them during controlled pollination. Pollen viability of Scots pine (Pinus sylvestris L.), mountain dwarf pine (P. mugo Turra) and their hybrid swarms was evaluated after 3-years storage at -20 degrees C using in vitro germination test. One population of each P. sylvestris and P. mugo were involved into study along with three hybrid swarms. Germination potential of the stored pollen grains was reduced significantly in comparison with freshly collected pollen. Profound decrease in germination rate was recorded in the two hybrid swarms (4.0-4.7%), less profound in the remaining three populations (0.6-2.4%). Pollen tube length, as the second pollen viability trait was reduced in stored pollen grains in a larger extend ranging between 51.4% and 54.3%. The pollen grains of the species P. mugo was exception in this respect yielding pollen grains whose growth was retarded of 21.9% only. Analysis of variance confirmed significant differences between fresh and stored pollen grains. Statistically significant were also the differences between compared populations and between tested individuals of the respective populations.

Abstract The crossability relationship between Scots pine (Pinus sylvestris L.) and mountain dwarf pine (Pinus mugo Turra) was tested under field conditions using an artificial pollination approach. There was partial compatibility between the parental species, as evidenced by the amount of filled seeds in their reciprocal crossings and in control variants from self-pollination, controlled intraspecific outcrossing and open pollination of mother trees. The crossability degree in P. sylvestris × P. mugo was characterised by the index 0.15, and the reciprocal crossing by the index 0.18. Crossability of P. sylvestris and P. mugo with their putative hybrid individuals was much higher; the number of filled seeds was comparable with that of the control variants. The reciprocal crossings of P. sylvestris and P. mugo species were highlighted by the opposite inheritance of their chloroplast DNA (cpDNA). The paternal cpDNA inheritance in P. sylvestris × P. mugo and maternal cpDNA inheritance in P. mugo × P. sylvestris was repeatedly confirmed using the cpDNA trnV-trnH/HinfI marker as well as the newly developed partial cpDNA trnV-trnH/AseI marker. The nature of the latter is described in terms of the nucleotide sequence.

Specific activity dynamics and isozyme composition of antioxidant enzymes ascorbate peroxidase (APX), catalase (CAT) and superoxide dismutase (SOD) were followed during the vegetation period in the young needles of Pinus mugo Turra, P. sylvestris L. and their putative hybrids. Tested enzymes differed in their dynamics showing the highest APX and CAT activities in the spring and autumn and the highest SOD activity in summer. The outlined course of enzyme activity was characteristic for all the three taxa compared. The level of specific enzyme activities was relatively constant in investigated taxa reaching statistical significance in some months of the scored period only. The same was true of the antioxidant enzyme activities of P. mugo individuals growing at different altitudes. Of the enzymes assayed, catalase was the most active. Hybrid individuals exhibited prevailingly intermediate level of their enzyme activity compared to the parental species. The dynamics of SOD correlated with intensity of UV irradiation during vegetation period. Partial correlation was observed between specific enzyme activities and isozyme composition.

The opposite modes of chloroplast DNA (cpDNA) inheritance were found to operate in the reciprocal crossings of Scots pine (Pinus sylvestris L.) and mountain dwarf pine (Pinus mugo Turra). The crossings were found to be partially compatible. In P. sylvestris × P. mugo crossing, the paternal transmission of cpDNA to the offspring takes place corroborating the generally acknowledged concept of the paternal cpDNA inheritance in gymnosperms. On the contrary, in P. mugo × P. sylvestris crossing the seed progeny exhibited P. mugo haplotype of the mother tree deviating conspicuously from the above concept. In the open pollination offspring of the putatively hybrid individuals of the Scots and mountain dwarf pines, a biparental inheritance of cpDNA was revealed in mother tree with P. mugo haplotype indicating a loosened control of the maternal inheritance of cpDNA in the putative hybrids. Implications and impacts of this finding for further studies are discussed.

Crossability relationships between Scots pine (Pinus sylvestris L.) and mountain dwarf pine (Pinus mugo Turra) was studied, using artificial pollination approach. Partial compatibility of the reciprocal crossings of these species was proved experimentally, validating the idea of a spontaneous formation of their hybrid swarms under natural conditions. The hybrids were validated using organellar DNA markers and nuclear DNA microsatellites. Based on the percentage of filled seeds, the interspecific crossings were less efficient than the intraspecific cross-pollinations of P. sylvestris and P. mugo individuals. Both species were found to intercross readily with individuals of their putative hybrid swarm, P. mugo exhibiting a higher hybridological affinity towards putatively hybrid individuals than P. sylvestris. Validation of the hybrids confirmed the paternal inheritance of chloroplast DNA (cpDNA) in the combination P. sylvestris × P. mugo only. Surprisingly, in the reciprocal crossing P. mugo × P. sylvestris, maternal inheritance of cpDNA was revealed. Obtained results offer a new insight into the direction and intensity of gene flow within the hybrid swarms of Scots pine and mountain dwarf pine.

The height growth dynamics of three interspecific crosses with Greek fir (Abies cephalonica Loud.) acting as mother and a control variant from self-pollination were followed throughout a period of 30 years. The hybrid combination A. cephalonica x A. nordmanniana exhibited enhanced growth relative to the selfed control at stage of 4-year old seedlings already, whereas the hybrid A. cephalonica x A. alba only at stage of 9-year old saplings. At age of 30, the heterotic growth persisted only in the latter, the hybrid A. cephalonica x A. nordmanniana was comparable in height growth parameters with a selfed control. The interspecific cross A. cephalonica x A. numidica was remarkable by its accelerated growth during early stages of the development. At age of 4 years it has surpassed in height growth both A. cephalonica x A. alba and control but has declined profoundly during subsequent stages of its development. A conspicuous feature of the hybrid needle anatomy were abundant resin canals and reduced size of some anatomical traits of its needles. In spite of variable growth potentials, all the three interspecific hybrids are recommended for planting in Slovakia, especially at densely polluted areas where domestic silver fir cannot withstand emission pressure.

KormuťáK, A., ČAmeK, V., BrAnná, m., ČelKoVá, m., VooKoVá, B., mAňKA, P., GAlGóci, m., BoleČeK, P., Gömöry, D. 2013. Introgessive hybridization between Scots pine and mountain dwarf pine at two localities of northern Slovakia. Folia oecol., 40: 201–205. Introgressive hybridization within hybrid swarm populations of Pinus sylvestris and P. mugo was analyzed in the localities Medzi Bormi and Sokolie, northern Slovakia, using species-specific trnV-trnH/Hinf I restriction profiles of chloroplast DNA of needles and zygotic embryos. The presence of trees with both P. sylvestris and P. mugo haplotypes indicates hybrid nature of the swarms. Molecular analysis revealed a relatively high rate of introgressive hybridization between putatively hybrid swarm individuals and the parental trees of the pure species P. sylvestris and P. mugo growing in the same localities. The proportion of hybrid seeds with P. sylvestris pollen donor averaged at 30.3%, whereas those with pollen donor of P. mugo at 19.8%. The results are discussed within context of the established crossability relationship between P. sylvestris and P. mugo.

Gene flow among individual trees of Pinus sylvestris and P. mugo putative hybrid swarms in Slovakia was fol-lowed at four localities using the species-diagnostic cpDNA trnV-trnH/Hinf I restriction profile. Variable proportions of P. sylvestris and P. mugo haplotypes were revealed among the sampled localities. Low between-habitus consistency of the trees and their cpDNA haplotypes indicates the hybrid nature of the swarms. Molecular analy-sis based on mutual comparison of the haplotypes of a given tree and its embryos suggests direct and recipro-cal hybridization between trees of the P. sylvestris and P. mugo haplotypes. Besides conspecific embryos resulting from hybridization of trees with the same haplotype (P. sylvestris × P. sylvestris and P. mugo × P. mugo), hybrid embryos of P. sylvestris × P. mugo (8.03%) and P. mugo × P. sylvestris (11.50%) were also detected in open-pollinated offspring. The results are discussed from the standpoint of primary and introgressive hybridization between the parental species.

Over the last decade, alternative methods of removing toxic metal ions from waste waters have been given increased attention, low costs, high efficiency, broad access and minimalization of chemical or biological sludge have become the main criteria. The methods of biosorption, which are based on binding metals to biomass, meet these criteria in considerable extent. Due to a high content of pectines, sugar beet cossettes show good adsorption properties and have high degree of re-usability in the process of bisorption. Thanks to these features, they become a very promising type of biomass for clearing waste waters contamined with heavy metals, especially lead. However, their broader application requires further research aimed mainly at optimalization of the process of biosorption.

Crossability relationships between six species of the Mediterranean, North American and Asian firs was tested using Abies alba and A. nordmanniana as female parents and A. alba, A. numidica, A. procera, A. grandis, and A. holophylla as pollen parents. An overwhelming majority of the crosses attempted was found to be compatible. In particular, it is true of the A. alba cross with A. numidica and those of A. nordmanniana with A. alba, A. numidica, A. procera, and A. holophylla. The crossing A. nordmanniana × A. grandis was the only exception producing empty seeds. Cytological study revealed the gametophytic incompatibility to be responsible for reproductive isolation of these species. At seedling level, all the interspecific crosses of A. nordmanniana surpassed in height growth self-pollinated control. The cross A. alba × A. numidica was comparable in this respect with control variants from open and self-pollination. Except for height growth, some characteristics of needle stomata are provided for individual crosses. The crosses A. nordmanniana with A. procera and A. holophylla represent unique interspecific combinations whose existence has not been reported yet. Based on needle stomata characteristics, the potential for increased resistance and drought tolerance of the hybrids with A. numidica involved as parental species is discussed.

We used artificial hybridization to study the crossability of the noble fir (Abies procera) with Manchurian fir (A. holophylla) and Caucasian fir (A. nordmanniana), and found compatibility between A. procera of North American origin and the Asian species A. holophylla as evidenced by the 14% fraction of filled seeds obtained in A. procera x A. holophylla crossing. Crossing of A. procera with the Mediterranean species A. nordmanniana failed completely, producing only empty seeds.