Antioxidative response of Helianthus annuus L. against copper toxicity

M.D. GROPPA; M.L. TOMARO; M.P. BENAVIDES

Buenos Aires, Argentina

Congreso; SFRR’s 12th Biennial Meeting; 2004

Society for free radical biology and medicine

Copper is essential for normal plant growth, though is phytotoxic at high concentrations. To study copper toxicity in sunflower, we evaluated some antioxidant enzymes, polyamines and proline during the first 16 days of growth, under 0.1 and 1 mM CuCl2. Plant growth was significantly reduced by the highest copper concentration from the seventh day of treatment. Ascorbate peroxidase, superoxide dismutase, glutathione and proline showed a significant increase, in shoots and roots, under 1 mM CuCl2 from day 10. Putrescine increased in shoots and roots from the 7th day, while spermidine and spermine increased in shoots only by day 16. Guayacol peroxidase increased in roots while glutathione reductase showed an irregular pattern under 1 mM Cu2+. Catalase was not detected in roots, while in shoots it decreased from day 16 under both copper concentrations. Thiobarbituric acid reactive substances (TBARS) increased in roots and shoots only with 1 mM CuCl2. Although some antioxidant enzymes, polyamines and proline (postulated as antioxidants), raised under 1 mM Cu2+, this increase was not enough to avoid growth inhibition and to protect sunflower plants against the oxidative damage produced by 1 mM Cu2+. The precise role of enzymes and antioxidant compounds against copper-induced oxidative damage is discussed.