Involvement of an antioxidant defence system in the adaptive response to heavy metal ions in Helianthus annuus L. cells

Abstract

A relationship between the antioxidant defence system and metal iontolerance in two types of sunflower callus differing in metal ion sensitivitywas studied. The antioxidant defence system of callus subjected to anadaptationtreatment of Cd(II), Al(III) and Cr(III) responded differently to 150μM of each metal compared with the corresponding controls undershock treatment. The GSH/GSSG ratio remained similar to control values for thethree metal-acclimated calli and in the chromium shock treatment, decreasingmoderately in the acute treatment with cadmium and aluminum. In contrast, theAs/DAs ratio was decreased in the two different treatments for the three metalsions, but the decrease was greater with acute stress. The antioxidant enzymesresponded differently according to the metal and treatment used. In chromiumadapted callus, all antioxidant enzymes increased except for glutathionereductase. However, in the shock treatment ascorbate peroxidase activity wasdiminished with each metal ion assayed. Guaiacol peroxidase was decreased bycadmium and chromium and remained similar to control values with aluminum.Glutathione reductase was only decreased by cadmium, and superoxide dismutaseand catalase activities were less increased than in tolerant cells. Theseresults suggest the involvement of an antioxidant defence system in theadaptiveresponse to heavy metal ions in Helianthus annuus L.cells.