Structural response of oregano stems to excess of soil copper HELEN PANOU-FILOTHEOU, GEORGE KOFIDIS and ARTEMIOS M. BOSABALIDIS* Department of Botany, School of Biology, Aristotle University, 54124 Thessaloniki, Greece Abstract Oregano plants (Origanum vulgare subsp. hirtum) were grown in soils containing increasing concentrations of Cu. High Cu concentrations exerted on plants a toxic effect which morphometrically, morphologically and anatomically comprised: a. reduction of the number of annual stems per plant. b. reduction of the stem length. c. thickening of the stem. d. decrease of the internode length. e. increase of the density of the stem non-glandular hairs. f. development of a large cavity in the center of the stem. g. disorganization of the stem cortex (chlorenchyma and collenchyma) and h. increase of the number of vessels in the xylem of the stem. Increased soil Cu concentration further resulted in a parallel increase of Cu, Fe, Mn, Mg and Ca bioaccumulation in the oregano stem. K bioaccumulation became greatly reduced.   < back .