Effect of copper on physiological and cytological aspects in Lactuca sativa L.

Samenvatting

The objective of this work was to characterize the effect of copper over physiological and cytological aspects in Lactuca sativa L. Lettuce seeds were exposed to the concentrations of 50, 100, 250 and 500 µM of CuSO₄ and distilled water was used as control, using five replicates constituted of 30 seeds and 3 mL of solution per treatment for phytotoxicity and three for cytotoxicity tests. For proline, enzymatic antioxidant activity, lipid peroxidation, we used four replicates with 50 seeds and 5 mL of solution. The experimental design used was completely randomized. The copper did not influence germination and dry biomass, however, root elongation and fresh biomass were reduced according to the increase of concentration. This can be attributed to the reduced mitotic index of 29.02 % in the control treatment to 1.5 % in the concentration of 500 µM of CuSO₄. Chromosomal abnormalities did not show significant difference. The accumulation of proline in the seedlings increased depending on the concentration of the metal. Superoxide dismutase (SOD) was the enzyme main responsible for the elimination of reactive oxygen species. Ascorbate and guaiacol peroxidase, and catalase did not present significant alteration. The action of SOD along with proline attenuated lipid peroxidation in the membranes. Although the concentration of 500 µM of CuSO₄ has been cytotoxic, it was not clastogenic in the tested conditions. In addition, the copper did not influence germination and dry biomass. We also highlight that L. sativa presented efficient antioxidant system, not allowing significant damage to cell membranes.