Ascorbic acid affects short-term response of Scenedesmus quadricauda to cadmium excess

Impact of ascorbate biosynthetic inhibitor (lycorine, LYC) on short-term cadmium (Cd) action (1 h, 100 μM) was studied in the green alga Scenedesmus quadricauda with 1 h or 24 h of LYC co-application. LYC suppressed Cd-induced increase in ascorbic acid and enhanced oxidative symptoms (ROS fluorescence) by modulating activities of antioxidative enzymes after 24 h of addition (decrease in superoxide dismutase, catalase and ascorbate peroxidase activities). Prolonged (24 h) exposure to LYC also affected content of Cd and quantitative changes of thiols (glutathione and phytochelatin 2) while Cd itself revealed interesting responses in algae maintained in the buffer for various time: these data indicate that in the studies involving axenic algal cultures, transfer of cells from sterile to non-sterile conditions modulates metal uptake. Among aliphatic organic acids, α-ketoglutaric, lactic and malic acids were variously influenced by Cd or lycorine, suggesting shift in the respiration and fermentation. It is concluded that ascorbic acid is involved in the protection of cells against Cd-induced ROS over-accumulation and metabolic changes were more expressive in the samples with 24 h co-application of LYC though side impacts of LYC cannot be excluded. DESI-Orbitrap MS for the identification and visualization of lycorine was also successfully tested here for the first time.