Nickel toxicity induced antioxidant enzyme and phenylalanine ammonia-lyase activities in Jatropha curcas L. cotyledons

Jatropha curcas embryos were germinated and grown in vitro under Ni concentrations of 100, 200, 400 and 800 micromol to observe the effects of high Ni concentrations on seedling growth. Biomass changes and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) in the cotyledons were monitored. The fresh weight of cotyledons in all the tested Ni conc. was lower than that of the control, but dry weight of cotyledons increased with increasing Ni conc. up to 200 micromol. SOD activity increased significantly up to 400 micromol and then decreased at 800 micromol Ni. POD activities were induced remarkably at 100 and 200 micromol, but the activity decreased with increasing Ni conc. Similarly, a negative link between CAT activity and Ni conc. was observed in this experiment. PAL activity had a positive correlation to Ni conc., the highest activity was found at 400 micromol Ni. Electrophoretic analysis suggested that a significant correlation between Ni conc. and isoenzyme patterns of SOD and POD was observed. These results were consistent with the changes of the activity assayed in solutions.