Tissue-specific metabolic response of Acanthopanax senticosus (Rupr.et. Maxim.) Harms leaves to enhanced UV-B radiation

This study aims to investigate the physiological regulation and metabolic reprogramming mechanism in the leaves of Acanthopanax senticosus (Rupr. et. Maxim.) Harms, a widespread medicinal plant, under enhanced UV-B irradiation. Metabolomic approaches were employed to evaluate the effect of specific tissues on physiological and metabolic responses to UV-B radiation. Two-year old potted A. senticosus plants were exposed to two levels of artificially produced and biologically effective UV-B radiation: 1.972 kJ m(-2) d(-1) and 3.442 kJ m(-2) d(-1), respectively, under glasshouse-controlled conditions. Natural solar light was included as a control group, in which major effects of UV-B were observed. It was observed that UV-B enhanced the production of bioactive metabolites (especially eleutheroside B and E) within A. senticosus, however, this enhancement was accompanied by reduction in its growth. The response of leaves to UV-B radiation varied across the different parts of the plant, the upper leaves had the most intense response. Furthermore, UV-B stress response involved the regulation of multiple types of phenolic compounds, including up-regulation of UV-absorbing substances (C6C3C6-type, kaempferol and rutin) and antioxidant enzyme synergists (C6C1-type, salicylic acid) as well as down-regulation of antioxidants (C6C3-type, p-coumaric acid).