Physiological Effects of Exposure to Copper and Chromium in Three Floating Aquatic Macrophyte Species

Abstract

The ability of plants to resist heavy metals is associated with the development of different ecotypes and intracellular strategies capable of dealing with the prevention, tolerance, and detoxification of heavy metal stress. This study aimed to present the physiological effects of exposure to copper and chromium in Eichhornia crassipes, Salvinia biloba, and Pistia stratiotes by measuring the activity of phytochelatins and glutathione, and oxidation-reducing enzymes (catalase, ascorbate peroxidase, and guaiacol peroxidase) and levels of chlorophyll. The experiment consisted of the exposure of 50 individuals of each species to a solution of chromium III at 150 ppm and copper II at 150 ppm, for 48 h. Chemical analysis of the metals was performed with inductively coupled plasma atomic emission spectrometry; catalase, ascorbate peroxidase, and guaiacol peroxidase and chlorophyll levels were analyzed by colorimetric method in spectrophotometry, and glutathione and phytochelatins by hyphen liquid chromatography. The changes observed in the concentrations of glutathione and phytochelatins highlight that the ascorbate glutathione cycle was activated together with the defense mechanism of the enzymes: catalase, ascorbate peroxidase, and guaiacol peroxidase. Observing the behavior of metal accumulation, and enzymes associated with the activity of the enzymes, it can be said that Eichhornia crassipes has a very efficient defense system, which makes it more resistant to copper, and an accumulator of chromium in the roots; Salvinia biloba and Pistia stratiotes accumulated and transported the two metals from the roots to the leaves; however, they had no defense mechanism and entered senescence in the last hours of the experiment.