A natural hybrid between the native Solidago virgaurea and the alien invasive S. gigantea, recorded in South Lithuania, is described as S. ×snarskisii nothosp. nov. A new nothosubsection, Solidago sect. Solidago nothosubsect. Triplidago nothosubsect. nov., is proposed to accommodate this hybrid and S. ×niederederi.

IntroductionIt is important to conduct studies on the influence of environmental factors on the accumulation of secondary metabolites in plants, as well as the cultivation of plants and harvesting of their raw material.ObjectiveIn this study, we examined the influence of habitat types, soil composition, climatic factors and altitude on the content of phenolic compounds in Iris species from different populations in Latvia, Lithuania and Ukraine.MethodologyAccording to high‐performance liquid chromatography (HPLC) analysis, 25 compounds (flavonoids, isoflavonoids, isoflavonoid glucosides, xanthones, phenolcarboxylic acids) were identified in the methanol extracts of 16 samples of Iris rhizomes. The quantitative data were further analysed by principal component analysis (PCA) to reveal the impact of environmental factors on the accumulation of compounds in plants.ResultsIris pseudacorus from Latvia and Lithuania had a more diverse composition of phenolic compounds than samples from Ukraine. Sampled plants of the Iris subg. Iris had a higher content of the analysed compounds than those of Iris subg. Limniris. PCA results showed that the levels of phenolic compounds in Iris rhizomes were influenced by the content of soil nutrients. The phosphorus and potassium content had a significant impact on the levels of phenolic compounds, whereas the impact of nitrogen content was not significant. Meteorological factors had a small impact; however, sunshine duration had a significant positive effect and the amount of precipitation had a significant negative impact.ConclusionThe results of this study suggest that rhizomes of Iris species may be an important source of pharmacologically active compounds such as flavonoids, isoflavonoids and xanthones. Studies on the effect of environmental factors on the production and accumulation of secondary metabolites in Iris species are important because they contribute to knowledge of quantitative parameters of secondary metabolites in medicinal plants and could be employed for the cultivation and harvesting of raw material for medicinal purposes.

Gudžinskas Z., Petrulaitis L., Žalneravičius E., 2017: New woody alien plant species recorded in Lithuania. -Bot. Lith., 23(2): 153-168.Many woody plant species that originate from various regions of the world have been introduced in other regions or continents and are used in ornamental gardening, silviculture, erosion control, for fruit sources or other purposes. Woody plants selected for introduction usually originate from regions with similar climate conditions; therefore, after certain time lag they start to spread outside places of cultivation, become naturalized or even invasive. In addition to 77 woody alien plant species reported in Lithuania, ten new species were recorded and analysed in this paper. Information on the native and anthropogenic ranges, first record in Lithuania, size of populations, habitats, reproduction and naturalization of Aralia elata, Berberis thunbergii, Caragana frutex, Celastrus orbiculatus, Cornus alba, Cytisus austriacus, Hydrangea arborescens, Pinus strobus, Rhus typhinaand Thuja occidentalis is presented. All these species have been introduced intentionally and are used mainly in ornamental gardening. Three of the reported species, Berberis thunbergii, Hydrangea arborescens and Thuja occidentalis, currently are casual species. Remaining seven species were recognized as naturalized in Lithuania, and five of these, i.e. Aralia elata, Celastrus orbiculatus, Cornus alba, Pinus strobus and Rhus typhina as well as Berberis thunbergii, which currently is treated as a casual, have very high or high probability of getting invasive. Constant survey of potential habitats, detection of new escaped alien plants, particularly of trees and shrubs, is the best way to reveal potentially dangerous species and make timely decisions for their control or eradication, if necessary.

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