High dose of urea enhances the nickel and copper toxicity in Brazilian elodea (Egeria densa Planch. Casp.)

Abstract

Selected cellular responses for urea (5 mM), Ni (100 μM), and Cu (100 μM) treatments and their combined effects on the leaves of a submerged macrophyte Brazilian elodea (Egeriadensa Planch. Casp.) were studied for 4 days. It was observed that the high dose of urea (5 mM) had a significant toxic effect on some physiological and biochemical characteristics of E. densa such as the content of chlorophyll a and the activities of catalase, ascorbate peroxidase, and guaiacol peroxidase. The elevated level of lipid peroxidation was accompanied by the accumulation of proline and ascorbate. A substantial increase in the amount of proline and urease activity was observed in Urea + Ni-treated leaves. The ascorbate content significantly increased in all the treated plants which correlated with ascorbate peroxidase activity. Urea with Cu ions affected the E. densa photosynthetic pigment system and urease activity adversely. The catalase activity was inhibited by the action of all the pollutants studied, especially in Urea + Cu-treated plants, whereas the peroxidases activity (APX and GPX) increased under the Cu and Urea + Cu action. The results presented indicate that the addition of the high dose of urea (5 mM) to the heavy metals studied may enhance the toxic effects in E. densa leaves, especially in the case of copper. © 2016, Botanical Society of Sao Paulo.