Mitja Križman

Research on floral nectar quantity and composition is increasingly frequent, yet existing studies predominantly focus on plant species with larger flowers that yield abundant nectar. Consequently, standard collection techniques like the microcapillary method are often optimized only for these morphologically larger structures. This study evaluated the applicability of the flower-washing method for nectar sampling in smaller, shallow flowers, comparing its efficacy against the well-established microcapillary method. Three native species from the Ranunculaceae family with diverse blooming phenologies and floral structures were selected: Caltha palustris, Anemone nemorosa, and Clematis vitalba. Nectar samples obtained through both sampling methodologies were analyzed using high-performance liquid chromatography (HPLC) to determine individual profiles and concentrations of sugars, phenolic compounds, and amino acids. The microcapillary method demonstrated notable physical limitations, failing to yield any nectar from A. nemorosa, while success rates remained low for the other two species. Conversely, chemical analysis revealed highly significant discrepancies between the two sampling approaches. The flower-washing method proved highly unreliable, as the mandatory excision of floral tissues caused cellular damage, possibly leading to the leakage of intracellular substances and artificial contamination of the collected nectar. These findings indicate that while flower-washing is occasionally utilized for low-volume flowers, it introduces severe methodological artifacts that compromise data accuracy, highlighting the critical need for refined microcapillary approaches in comparative nectar analysis.

A rapid and simplified LC–MS method was developed for quantifying vitamins D3 (cholecalciferol) and K2 (menaquinone-4 and menaquinone-7) in high-fat chicken meat products. Sample preparation involves a two-step solvent extraction followed by centrifugation. Efficient separation was achieved on a Gemini C18 column, and electrospray in positive mode was used for detection. Method validation confirmed good performance and reproducibility. The method was successfully applied to both fortified and unfortified chicken pâté samples. Owing to its simplicity, robustness, and sensitivity, this approach provides a practical and reliable means for quantifying fat-soluble vitamins in complex animal-derived matrices and can serve as a foundation for broader applications in high-fat food products.

Slug herbivory is an important but poorly explored driver of plant defence and belowground multitrophic interactions. This study examined how aboveground feeding by Arion vulgaris and Deroceras reticulatum affects oxidative status, photosynthetic pigments, and volatile organic compound (VOC) emissions in cabbage (Brassica oleracea L. var. capitata), and whether these changes influence slug-parasitic nematodes. Slug feeding induced strong oxidative stress in leaves and roots, reflected by depletion of total ascorbate and glutathione contents and increased proportions of their oxidized forms, indicating a systemic redox imbalance. Photosynthetic pigments were also markedly affected, characterized by decreased chlorophylls and carotenoids and activation of the xanthophyll cycle towards more zeaxanthin, particularly in plants attacked by D. reticulatum. Headspace SPME–GC–MS analysis revealed tissue-specific, herbivory-induced shifts in VOC profiles. Based on these changes, three VOCs—3-phenylpropionitrile, allyl isothiocyanate, and 2-hexenal—were selected for chemotaxis assays. Behavioural experiments showed that VOC identity and nematode species markedly influenced motility and chemotactic responses. Phasmarhabditis papillosa exhibited the strongest attraction to 3-phenylpropionitrile, whereas allyl isothiocyanate acted as a weak repellent to P. papillosa, Oscheius myriophilus, and Oscheius onirici. In contrast, 2-hexenal elicited no consistent directional response. These results demonstrate that slug herbivory alters cabbage metabolism and volatile signalling, shaping species-specific nematode behaviour and highlighting its potential for sustainable slug management.

Fragaria vesca L. is a common plant species in Slovenia. It flowers from May to July. Our study was conducted throughout the 2024 season in two locations at which we sampled nectar in F. vesca flowers. To take the nectar samples, we used microcapillaries. We studied Fragaria vesca nectar production and its composition (sugars, amino acids, and phenolic compounds) throughout the day. We had some problems with sampling nectar in the afternoon, which affected our research, since there were times during which we could not obtain any samples. F. vesca on average secreted 0.02 μL nectar per one flower sample. Our data show that nectar production is highest in the morning, nectar is hexose-dominant, and the time of day affects the sugar concentration, which reaches a maximum at noon. The most common amino acid in F. vesca nectar is proline, and the amino acid concentration is highest in the morning. Quercetin and rutin are common phenolic compounds in the nectar of F. vesca, and the concentration of phenolic acids is highest at noon, as bees are the most active in the spring when mornings are colder.

In this study, a new, patented form of a water-soluble cannabidiol (CBD) complex was synthesised and tested. The formation of the complex is based on the interactions, presumably through hydrogen bonding, between cannabidiol and glucosamine, the latter contributing significantly to the increased hydrophilicity. The complex was characterised by chromatography, thermal analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and permeability tests. This complex has a substantially higher water solubility than normal CBD. Permeability tests indicate that it has almost five times lower permeability through lipophilic membranes and less than half the membrane mass retention of conventional CBD. At the same time, its equilibrium concentration is almost four times higher than that of normal CBD. These results suggest that this new form of CBD is a promising candidate for future biological and clinical studies, as it offers improved bioavailability and biodistribution.

Crataegus monogyna Jacq. and Prunus spinosa L. are common spring-flowering species in Slovenia. They occur in large stands and sometimes overgrow in unmanaged meadows. They are known as an excellent source of nectar for bees and other pollinators. Phenolic compounds are known as antioxidant for both pollinators and plants. We were interested in comparing plant species in terms of their phenolic compound content: rutin, quercetin, (iso)quercitrin, chlorogenic acid, and hyperoside. Their nectar was obtained from both plant species in 2024 in Ljubljana and the area surrounding Ljubljana. We took 96 samples of each species. The nectar was sampled with microcapillary tubes and analysed by HPLC. When studying the influence of abiotic factors on the concentration of phenolic compounds, the correlations were weak, so we cannot say with certainty which environmental factors affect which phenolic compounds and in what way. Rutin is predominant in the nectar of P. spinosa and chlorogenic acid is predominant in the nectar of C. monogyna. Hyperoside is found in the lowest concentration in both plant species. We found that although C. monogyna secreted much less nectar at midday, it was more concentrated in phenolic compounds at this time than in the morning. In P. spinosa, nectar secretion was highest in the morning, and the concentration of phenolic compounds was also highest in the morning.

This study of underground multitrophic communication, involving plant roots, insects, and parasitic nematodes, is an emerging field with significant implications for understanding plant–insect–nematode interactions. Our research investigated the impact of wireworm (Agriotes lineatus L. [Coleoptera: Elateridae]) infestations on the ascorbate–glutathione system in sweet pepper (Capsicum annuum L.) plants in order to study the potential role in root-exudate-mediated nematode chemotaxis. We observed that an A. lineatus infestation led to a decrease in leaf ascorbate levels and an increase in root ascorbate, with corresponding increases in the glutathione content in both roots and leaves. Additionally, a pigment analysis revealed increased carotenoid and chlorophyll levels and a shift towards a de-epoxidized state in the xanthophyll cycle. These changes suggest an individual and integrated regulatory function of photosynthetic pigments accompanied with redox modifications of the ascorbate–glutathione system that enhance plant defense. We also noted changes in the root volatile organic compound (VOC). Limonene, methyl salicylate, and benzyl salicylate decreased, whereas hexanal, neoisopulegol, nonanal, phenylethyl alcohol, m-di-tert-butylbenzene, and trans-β-ionone increased in the roots of attacked plants compared to the control group. Most notably, the VOC hexanal and amino acid exudate cysteine were tested for the chemotaxis assay. Nematode responses to chemoattractants were found to be species-specific, influenced by environmental conditions such as temperature. This study highlights the complexity of nematode chemotaxis and suggests that VOC-based biological control strategies must consider nematode foraging strategies and environmental factors. Future research should further explore these dynamics to optimize nematode management in agricultural systems.

Floral nectar is mainly a reward in the form of food for pollinators. In early spring, when snow can still be present, pollinators have trouble finding food. The composition and productivity of nectar in flowers play an important role in a pollinator’s life. It is known that low temperatures and lower humidity cause lower nectar secretion. Some studies have also shown that the quality of nectar can differ because of lower temperatures. In our research, we analysed whether abiotic factors affect nectar secretion, as well as the nectar composition of the early spring plant species Galanthus nivalis L. and Helleborus niger L. in February 2024. The study was conducted in two locations in nature. Nectar from H. niger was sampled in Tomišelj, Slovenia, whereas nectar from G. nivalis was sampled in Ljubljana, Slovenia. On four different days at three different times of day, we sampled nectar from flowers using microcapillaries. In total, we sampled 48 nectar samples from one species. We analysed soil humidity and temperature, air temperature and humidity, and UVB radiation. Our results show that nectar productivity is highest in the morning for both species. H. niger has sucrose-dominant nectar, while G. nivalis has hexose-dominant nectar. Proline, which is an important amino acid for bees, has the highest level in both species, as does the phenolic compound rutin. Environmental factors do affect nectar secretion. Soil and air temperature affect G. nivalis nectar secretion, while soil humidity affects H. niger nectar secretion. Soil and air temperature also have an effect on higher levels of sugars in both researched nectars. UVB, air humidity, and air and soil temperature seem to have an effect on phenolic compounds, but abiotic factors do not affect amino acids.

Background and Purpose: The ligands of the imidazoline and α-adrenergic receptors are mainly imidazoline and guanidine derivatives, known as centrally-acting antihypertensives and compounds with potential use in various neurological disorders. The extent of their ionisation has a major influence on their behaviour in the different analytical systems. The main objective of this work was to compare the mechanism of chromatographic retention and electrophoretic mobility under acidic, neutral and basic conditions. Experimental Approach: Multiple Linear Regression and Partial Least Squares Regression were applied for the QSRR (quantitative structure-retention relationship) and QSMR (quantitative structure-mobility relationship) modelling and to select the most important molecular parameters describing the chromatographic and electrophoretic behaviour of the investigated compounds. Key Results: The most important molecular descriptors, such as the chemical composition of the compounds, lipophilicity, polarizability and molecular branching, in the selected QSRR models showed that an important insight into the retention behaviour can be derived from the 0D-, 1D- and 2D-descriptors. The electrophoretic mobility could be explained by 2D- and 3D-descriptors, which provide information on the molecular mass, size and complexity, as well as on the influence of charge transfer and electronic properties on the migration behaviour. Conclusion: All created QSRR/QSMR models met the stringent validation criteria and showed high potential in describing the chromatographic and electrophoretic behaviour of investigated compounds.