Helianthus annuus L. antioxidant responses against cadmium or copper toxicity

GROPPA MD, LASPINA NV, BENAVIDES MP, TOMARO ML

Iguazú, Misiones, Argentina

Congreso; XL Reunión Anual, Sociedad Argentina de Investigación Bioquímica y Biología Molecular, SAIB 2004; 2004

SAIB

During the last years, it has been observed a significant increase of metal soil contamination. Thus, the aim of this work was the study of cadmium and copper toxicity in sunflower plants exposed to 0.5 mM CdCl2 or CuCl2 during 16 days. Metal effect on sunflower growth was evaluated by the length of roots and shoots and the relative water content (RWC). Both metals produced an inhibition of plant growth, but RWC was only affected by cadmium. The raise in TBARS content evidenced the oxidative damage produced by these metals. Sunflower plants responded to stress increasing ascorbate peroxidase activity at day 7 and 10 in shoots and at day 16 in roots. On the other hand, cadmium and copper diminished guaiacol peroxidase activity in shoots at day 10 and 16 respectively. However, in roots, it was observed an increase of the enzyme activity. Superoxide dismutase showed a very variable behavior, depending on the metal used, the plant tissue and /or the day of treatment. Glutathione content decreased at day 10 and then increased at day 16. Polyamine and proline, reported as antioxidant metabolites, were also measured. Although putrescine increased in shoots at day 7 with both metals, it decreased the following days. In roots, it increased from day 7 of treatment. Proline content showed a raise both in shoots and roots. It is clear that sunflower is responding against the metal stress by increasing some antioxidant defenses. However, growth inhibition and membrane lipid peroxidation could not be avoided.