Manganese (Mn) uptake and toxicity in chamomile (Matricaria chamomilla) and changes of phenolic metabolites in plants grown in the soil (1000 μM Mn2+) or hydroponic culture (100 or 1000 μM Mn2+) were studied. Under soil cultivation, Mn excess reduced growth and induced symptoms of oxidative stress (including total ROS, hydroxyl radical and lipid peroxidation as detected by fluorescence microscopy), concomitantly with depletion of non-protein thiols and ascorbic acid. Total soluble phenols and individual phenolic acids were rather depleted (p-coumaric, chlorogenic, and protocatechuic acids) or unaltered (vanillic and caffeic acids). Shoot Mn content reached 2806 μg/g DW with BAF 51.0 in the soil culture. In hydroponics, tetraploid plants contained less Mn in both shoots and roots than diploid ones with bioaccumulation factor and translocation factor (diploid/tetraploid) 57.1/37.9 and 0.39/0.32 in 1000 μM Mn treatment. Plants cultured in hydroponics revealed stimulation of some phenolic acids, mainly chlorogenic acid in the shoots and p-hydroxybenzoic and vanillic acids in the roots (more extensively in tetraploid ones which contained less Mn). Data indicate that excessive Mn accumulation has negative impact not only on the growth but also on phenolic metabolites in young plants mainly. Detailed comparison of the observed metabolic changes with limited literature focused on Mn physiology is provided as well.
Keywords: Antioxidants; Fluorescence microscopy; Heavy metals; Soil pollution.
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