Nickel accumulation and its effects on Eichhornia crassipes.

GONZÁLEZ CI; MAINE M; SANCHEZ GC; BENAVIDES MP

Nantes

Simposio; 5th International Symposium on Wetland Pollutant Dynamics and Control, WETPOL 2013; 2013

INTRODUCTION Aquatic plants play an important role in constructed wetlands systems for the treatment of wastewaters containing metals. Nickel is an essential element for plant growth and development (Liu, 2001). However, at higher concentrations nickel is a toxic pollutant, inducing lipid peroxidation and oxidative stress. These physiological and biochemical damages can result in a dramatic reduction of the growth and productivity of plants, eventually causing death. The main aim of this work was to study the effect of nickel accumulation in Eichhornia crassipes. The responses of physiological parameters, oxidative damage and changes in antioxidant enzyme activities were evaluated in roots and aerial parts. METHODS Macrophytes were collected from natural wetlands and acclimated for one week in the laboratory (under controlled conditions of temperature, humidity and light) using dechlorinated water as culture medium. Two litres of water and one plant were added in experimental reactors. Nickel was added to obtain concentrations of 1, 2, 3 and 4 mg/L. The study was conducted over 3 days, sampling at periods of 24, 48 and 72 h. The experiments were performed in triplicate with a control in the absence of Ni. The following analytical determinations were performed: + Measurement of concentration of chlorophyll a, b and α-β carotenoids: Wellburn (1994). + Determination of lipid peroxidation: Heath and Packer (1968). + Determination of enzymatic activity of catalase: Maehly and Chance (1954) (modified). + Determination of enzymatic activity of guaiacol peroxidase: Bergmeyer (1983). + Determination of nickel in tissues: atomic absorption spectrophotometry. RESULTS AND DISCUSSION According to Fig. 1, the accumulation of nickel in roots and aerial parts increased depending on concentration and exposure. Higher levels of nickel were recorded in roots and lesser amounts were translocated to aerial parts. Nickel produced a significant increase of chlorophyll a and b, for concentrations of 3 and 4 mg/L in the first 24 h of contact. At 48 h an increase in the exposures of 1 and 2 mg/L was observed, but a decrease at all exposures was detected at 72 h. This could be an indication of growth inhibition. However, there were no significant differences among the chlorophyll concentrations between the different exposures and the control. Compared to the control, malondialdehyde (MDA), a marker of lipid peroxidation, increased significantly in the exposure of 4mg/L at 24 and 48 h in aerial parts. In roots, a significant increase of 19.2 % and 26.4 % in malondialdehyde level was found at 3 and 4 mg/L, respectively, for the period of 72 h. A significant increase of catalase activity in the aerial parts was observed in the first 24 h, with a maximum of 44.40 (nmol min-1 mg-1prot) at the concentration of 3 mg/L. After 24 h ABSTRACTS - WETPOL 2013 - October 13-17, 2013 - Nantes - FRANCE 290 the activity decreased significantly with an increasing exposure time, reaching a value below those of the control. Regarding roots, no significant differences among concentrations and exposure times were observed in the catalase enzyme activity. The guaiacol peroxidase activity increased significantly in all treatments performed both in aerial parts and in roots. This may indicate that the guaiacol peroxidise enzyme plays an important role in antioxidant defence