Does the Reaction of Inflorescences and Flowers of the Invasive Prunus serotina Ehrh. to Various Herbicides Give Hope for Elimination of This Species from Polish Forests?

The North American Prunus serotina Ehrh. is an invasive neophyte widespread in Polish forests. Due to the negative impact of this species on native vegetation, the most effective methods of its removal from the stands have been searched for. Our research aimed to determine whether herbicides that were applied in spring 2020 influenced morphological features of inflorescences and flowers of P. serotina in the next year of vegetation (i.e., 2021). So far, the effects of herbicides used were analysed in the same year, no later than a few weeks after their application. The experiment was carried out on the research area of 2.7 ha located in the Zielonka Forest near Poznań in Poland (N 52.5330, E 17.1015). The response of 39 P. serotina trees to six different herbicides, containing sulfonylurea derivatives, glyphosate and phenoxy herbicides was investigated. The chemicals were applied directly to the tree, to the holes made in the trunk axis. The plant material included inflorescences from 10 control trees and 29 trees treated with different herbicides. Nine morphological inflorescence and flower features and three ratios were analysed. In total 200 inflorescences and 1000 flowers were measured. Statistically significant differences between inflorescence and flower features collected from trees treated with different herbicides were demonstrated. The largest ranges of values of the studied features were found in inflorescences and flowers collected from the control trees (C-WI, C-DWH). The greatest variability of the studied features was found for C-DWH. Compared to the control trees the reduction in inflorescence size, as well as the smaller number of flowers, were recorded in the trees treated with different herbicides, irrespective of an active substance content. The use of six different herbicides—with different active substance contents to control P. serotina proves to be effective.

First Results of Monitoring the New Invasive Species Prunus serotina Ehrh. Population inside the Regeneration Area of Common Oak-Hornbeam Forest in Western Croatia

Black cherry ( Prunus serotina Ehrh., Rosaceae) is a widespread invader of the European temperate forests and a significant component of the human-caused part of the global environmental changes. Its successful invasion results from a complex interaction between the species life traits and the recipient ecosystem attributes. While it has been recorded to develop spontaneously in numerous European countries, in Croatia information details on its population distribution, as well as its current status, are still missing. The individuals of P. serotina were found in the pedunculate oak (Quercus robur L.) forest regeneration area of Jastrebarsko forest management unit in 2018. This alerted us to start to monitor its spreading area, status and impact on the native plant species in a four-year period (2018-2021). In order to investigate the habitat characteristics, phytosociological approach was applied. In addition, the area was surveyed using an unmanned aerial vehicle (UAV) DJI Mavic 2 Pro and DJI Ground Station Pro. The results showed that P. serotina spread considerably in the regeneration area, which indicates its invasive character. It also caused alteration in current vegetation. Fast initial expansion of P. serotina in 2019 was slowed down in the next 2 years due to performed tending activities, suggesting mechanical measures could help to control its invasive spreading at an early stage of development. This research brought up the first record of the Prunus serotina species in pedunculate oak forest regeneration area of western Croatia with a recommendation to continue the monitoring survey in order to help prevent its spread in the future.

Analysis of Phenolic Compounds for the Determination of Grafts (in) Compatibility Using In Vitro Callus Cultures of Sato-Zakura Cherries

The aim of this study was to prove that under in vitro conditions, the adhesiveness of the callus between rootstock and scion, the development of callus cells at the points of fusion, and the presence of phenolic components are closely related to the level of (in) compatibility of the grafting combinations between Sato-zakura cherry cultivars (‘Amanogawa’, ‘Kanzan’, and ‘Kiku-shidare-zakura’) and commercial rootstocks. Prunus avium, Prunus ‘Colt’, Prunus mahaleb and Prunus serrulata were used as compatible and Prunus serotina and Pyrus communis ‘Pyrodwarf’ were used as two potentially incompatible rootstocks. The results indicated the significant manifestations of the early signs of the incompatibility on the callus junction. Phenols, as well as tissue senescence, were very precisely localized by toluidine blue and alcian blue as well as safranin staining, which can indicate the early signs of the callus incompatibility in some grafting unions. In the callus unions of Prunus avium with ‘Amanogawa’ and ‘Kiku-shidare-zakura’ the results of chemical analyses indicated that the existence of several flavonols, flavones and phenol acids could be involved in the incompatibility process in grafted combination. The detection of flavonol astragalin in the unions can be a biomarker of compatibility between scion and the rootstock, while some polyphenols, such as neochlorogenic acid, sinapic acid, ellagic acid, caffeic acid, baicalein, naringenin, apigenin and luteolin can be used as the indicators of graft incompatibility. p-coumaric acid and ferulic acid could be used for detection of delayed incompatibility.

Characterization of the Insect Assemblage and Associated Floral Volatiles of Black Cherry (Prunus serotina)

Black cherry is an ecologically important high-value wood. A decline of its regeneration has been reported in the USA, which could be associated with a lack of pollination. This study was conducted to identify insects visiting black cherry flowers, to determine whether insects captured on the flowers carry black cherry pollen and to identify the volatile organic compounds (VOCs) emitted by flowers of black cherry. A two-year insect survey was conducted before, during and after the black cherry bloom. A total of 9533 insects were captured in traps and Diptera was the most abundant (64.1%). Significantly more insects in Diptera, Lepidoptera and Thysanoptera were captured in the traps installed in the canopy than those on the ground, and Anthalia bulbosa (Diptera: Hybotidae) was the dominant species. Electron microscopy analyses demonstrated that insects captured in the canopy indeed carried black cherry pollen. Black cherry flowers emitted a VOC blend that is composed of 34 compounds and dominated by β-ocimene and several phenylpropanoids/benzenoids. This floral VOC profile is similar to that of other pollinator-dependent Prunus species. This study reports pollinator insects and associated VOCs, for the first time, that could play a significant role in the pollination and regeneration of black cherry.

Phenolic composition of leaf and flower extracts of black cherry (Prunus serotina Ehrh.)

Key Message The best yields in the extraction of hydroxycinnamic acids, flavanols and total phenolics from black cherry flowers were obtained with 40% ethanol and the poorest with water. A 30% higher content of total phenolics was obtained from leaves by using methanol rather than water. Context Black cherry (Prunus serotina Erhr.) is widespread in Europe. Because it is an invasive species, most research has been aimed at trying to find a method to remove this shrub from forests. The incentive for the development of the research was that we were trying to find a possible folk use of black cherry leaves and flowers. Aims The aim of this work was to study the detailed phenolic profile of extracts of P. serotina leaves and flowers. Methods Three types of extracts of P. serotina were made. The extracts were analysed for differences in phenolics content based on different extraction methods. HPLC-MSn was used to identify the phenolic compounds, and HPLC–DAD was used for their quantification. Results The results show that different extraction methods result in differences in the amount of extractables. Flavanols are the main group of identified compounds in both leaves and flowers. A larger extraction efficiency leads to a higher amount of phenolics in the flowers compared to leaves (49.8 vs. 36.5 g/kg dry weight). No difference was detected in the amount of phenolics between water extracts of leaves and flowers. Each extract can be considered rich in phenolics. Conclusion This work shows that leaves and flowers of P. serotina are a rich source of phenolic compounds. We provide interesting results that might be of interest in the industrial valuation of several compounds.

Effect of Prunus serotina Ehrh. Volatile Compounds on Germination and Seedling Growth of Pinus sylvestris L.

In temperate European forests invaded by Prunus serotina Ehrh. (black cherry), a reduction in the spontaneous regeneration capacity of Pinus sylvestris L. (Scots pine) is observed. It could be caused by various factors, including allelopathic properties of this invasive plant. In this study the phytotoxic effect of P. serotina volatile compounds on P. sylvestris and the seasonal variation in this effect were assessed. Simple assays showed that volatiles emitted from P. serotina leaves significantly inhibited root growth of P. sylvestris seedlings. Their negative effect on stem growth was much weaker. The strongest phytotoxic effect on Scots pine seedlings was caused by the volatiles emitted from the youngest black cherry leaves. In fresh foliage of P. serotina, nineteen volatile organic compounds were identified by gas chromatography–mass spectrometry (GC–MS). The dominant compound was benzaldehyde. On the basis of tests of linalool alone, it was found that this monoterpene present in the volatile fraction has a strong allelopathic potential and inhibits germination, root elongation and shoot elongation of pine seedlings. The results of our research suggest that volatile compounds from P. serotina leaves could limited survival of P. sylvestris individuals in the seedling phase.

Composition of Phenolic Compounds, Cyanogenic Glycosides, Organic Acids and Sugars in Fruits of Black Cherry (Prunus serotina Ehrh.)

The forest understory is rich in fruit-bearing trees and shrubs. They include both native species and invasive alien plant species (IAPS). One of the most spreading IAPS is black cherry (Prunus serotina E.). Problems with the invasiveness of P. serotina is well known in many European countries. However, there are very few studies related to this IAPS. This article aims to fill the gap in research on the bioactive compounds of black cherry fruits and thus to start a discussion on the potential use of this species on an industrial or semi-industrial scale, which may lead to the reduction of this species presence in forests. Fruits were collected in a forest of Northern Poland. Contents of sugars, phenolic compounds as well as cyanogenic glycosides were determined. Pphenolic compounds and cyanogenic glycoside were assayed using HPLC-DAD coupled with MSn. Sugars and organic acids were determined with the use of HPLC-DAD. Fruits of P. serotina can be considered as rich in anthocyanins, even at a lower level of total phenolics than in their plantation-grown couterparts, fruits of black cherry are still a good source of dietary phenolics of natural, forest-grown origin. When stones are not crushed during processing the level of GCC is within a safe, admissible range.