title: Temperature is the key to altitudinal variation of phenolics in Arnica montana L. cv. ARBO.
abstract: Plants in alpine habitats are exposed to many environmental stresses, in particular temperature and radiation extremes. Recent field experiments on Arnica montana L. cv. ARBO indicated pronounced altitudinal variation in plant phenolics. Ortho-diphenolics increased with altitude compared to other phenolic compounds, resulting in an increase in antioxidative capacity of the tissues involved. Factors causing these variations were investigated by climate chamber (CC) experiments focusing on temperature and ultraviolet (UV)-B radiation. Plants of A. montana L. cv. ARBO were grown in CCs under realistic climatic and radiation regimes. Key factors temperature and UV-B radiation were altered between different groups of plants. Subsequently, flowering heads were analyzed by HPLC for their contents of flavonoids and caffeic acid derivatives. Surprisingly, increased UV-B radiation did not trigger any change in phenolic metabolites in Arnica. In contrast, a pronounced increase in the ratio of B-ring ortho-diphenolic (quercetin) compared to B-ring monophenolic (kaempferol) flavonols resulted from a decrease in temperature by 5 degrees C in the applied climate regime. In conclusion, enhanced UV-B radiation is probably not the key factor triggering shifts in the phenolic composition in Arnica grown at higher altitudes but rather temperature, which decreases with altitude.
authors.affiliation: Abteilung Experimentelle Umweltsimulation, Institut für Bodenökologie, Helmholtz Zentrum München-Deutsches Forschungszentrum für Gesundheit und Umwelt, Neuherberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Albert
authors.forename: Vipaporn
authors.initials: V
authors.lastname: Sareedenchai
authors.forename: Werner
authors.initials: W
authors.lastname: Heller
authors.forename: Harald K
authors.initials: HK
authors.lastname: Seidlitz
authors.forename: Christian
authors.initials: C
authors.lastname: Zidorn
mesh_terms: D000531:Altitude; D000704:Analysis of Variance; D018650:Arnica / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D035264:Flowers / Q000737:chemistry*; D044949:Kaempferols / Q000032:analysis; D010636:Phenols / Q000032:analysis*; D010936:Plant Extracts / Q000032:analysis*; D011794:Quercetin / Q000032:analysis; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D044949:Kaempferols; D010636:Phenols; D010936:Plant Extracts; D011794:Quercetin