Short-term physiological responses to copper stress in Salvinia auriculata Aubl.

Abstract

AIM: To evaluate, in a short-time exposure, the physiological responses of Salvinia auriculata Aubl. under different concentrations of Cu. METHODS: The plants were exposed to treatments with 0.01, 0.1, 1 and 10 mM of Cu in a period of 2 days. Then development variables of S. auriculata (weight, photosynthetic pigments, and soluble carbohydrate), lipid peroxidation (malondialdehyde, aldehydes, and electrolyte leakage) and production of antioxidants (anthocyanins, carotenoids, flavonoids, and proline) were evaluated. RESULTS: It was observed fresh weight reductions in concentrations above 1 mM of Cu. Chlorophyll a decreased with the increase of Cu concentrations unlike chlorophyll b. The ratio chlorophyll a / chlorophyll b was changed due to the degradation of photosynthetic pigments. The reductions of carotenoids were more pronounced than that of total chlorophyll. The values of electrolyte leakage ranged from 14 to 82 % and lipid peroxidation from 7 to 46 nmol.g-1. Flavonoids and soluble carbohydrates showed reductions with the increase of Cu concentration. Anthocyanins, phenolic compounds, and proline when subjected to 0.1 mM of Cu had increased, suggesting adaptability of plant stress caused directly by metal and reactive oxygen species. In higher concentrations, degradation and/or direct modifications of these molecules possibly occurred. CONCLUSIONS: The data suggest that S. auriculata is provided with an efficient mechanism against stress caused by Cu in the concentration of 0.1 mM. As for higher concentrations (1 and 10 mM), despite its role as micronutrients, Cu was toxic to the plant due to the redox behavior of this metal, which leads to the exacerbated formation of reactive oxygen species, inducing to severe damage such as biological membrane degradation and protein denaturation.