The genus Rosa is very extensive and variable, so it remains very unpredictable and uninvestigated. This also holds true for values of secondary metabolites in rose hips, which are important for several purposes (human diet, protection of plants against pests, etc.). The aim of our study was to determine the content of phenolic compounds in the hips of R. × R. glauca, R. corymbifera, R. gallica and R. subcanina, which grow wild in nature in southwestern Slovenia. We examined the content of phenolic compounds in different parts of rose hips, in the flesh with skin and in the seeds, depending on the individual species, over a period of two years, 2020 and 2021. We also considered the influence of environmental conditions on the content of the mentioned compounds. In both years, the content of phenolic compounds was higher in the flesh with skin than in the seeds. Considering the total content of phenolic compounds in the flesh with skin, R. gallica stands out (15,767.21 mg/kg FW), but the hips of this species accumulated the lowest number of different phenolic compounds. The lowest content of total phenolic compounds (TPC) was found in R. corymbifera, in the year 2021 (3501.38 mg/kg FW). The content of TPC (in both observed years) in the seeds varied between 1263.08 mg/kg FW (R. subcanina) and 3247.89 mg/kg FW (R. × R. glauca). Among the anthocyanins, cyanidin-3-glucoside was determined, which was predominant in R. gallica (28.78 mg/kg FW), and at least was determined in R. subcanina (1.13 mg/kg FW). When comparing the two years of the period (2020–2021), we found that 2021 was more favorable for the formation of phenolic compounds in the seeds, but 2020 in the flesh with skin.

The influence of mycorrhizal inoculum in combination with different phosphorus treatments on growth and flowering parameters of Ajania (Ajania pacifica (Nakai) Bremer et Humphries) plants was investigated in two growing seasons (2015 and 2016). Plants of the cultivar ‘Silver and Gold’ were transplanted into pots either with added mycorrhizal inoculum or without inoculum and assigned to four phosphorus treatments. Mycorrhizal colonization was assessed by evaluating the frequency of colonization, intensity of colonization and density of fungal structures (arbuscules, vesicles, coils and microsclerotia) in the roots. During the growing season, the content of plant available phosphorus in the soil was analyzed, and shoot length, number of shoots, number of inflorescences, number of flowers and flowering time were evaluated. Inoculated Ajania plants were successfully colonized with arbuscular mycorrhizal fungi and dark septate endophytic fungi. In the root segments, hyphae were mainly observed, as well as vesicles, coils, arbuscules and microsclerotia, but in lower density. The density of fungal structures did not differ among phosphorus treatments, but did differ between years, with a higher density of fungal structures in 2016. Mycorrhizal plants developed higher number of shoots in 2016, higher number of inflorescences, higher number of flowers, and they flowered longer compared to uninoculated plants.

The involvement of different quercetins [quercetin-3-O-rhamnoside (quercitrin), quercetin-3-D-galactoside (hyperoside) and rutin] and catechins (catechin, catechol) in the rooting process of leafy cuttings was studied in two hybrid chestnut (Castanea crenata × Castanea sativa) clones, Maraval and Marsol. Both clones differed strongly in rooting results. The Maraval clone cuttings, which had a high rooting rate, contained, on average, higher amounts of all quercetins in different plant parts (leaves and basal cuttings) than the Marsol clone, which had a low rooting rate. There was a highly significant correlation between the quercetin contents of the cutting leaves and the rooting process (number of main roots). The catecechin contents of the cutting leaves did not show any correlation with the rooting process.