Effects of Zinc on Growth and Antioxidant Responses in Jatropha curcas Seedlings

Jatropha (Jatropha curcas) embryos were geminated and grown in vitro under different zinc concentrations (0, 0.25, 0.5, 1, 2 & 3 mM) to investigate its influence on the growth and the changes of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and phenylalanine ammonia-lyase (PAL) activities in Jatropha seedlings. The biomass of the cotyledons, hypocotyls and radicles was increased with increasing zinc concentration and the largest increments were observed at 0.25, 0.5 and 0.5 mM, respectively. SOD activity in the cotyledons, hypocotyls and radicles was increased gradually with the increase in zinc concentrations. While POD activity in the cotyledons, hypocotyls and radicles was enhanced with increase in zinc concentrations. CAT activity in the cotyledons, hypocotyls and radicles reached the largest increments at the zinc concentrations of 0.5, 2 and 0.5 mM, respectively. PAL activity showed a similar trend compared to the changes of CAT activity. Electrophoresis anaylsis suggested a significant correlation between zinc concentrations and isoenzyme patterns of SOD. POD and CAT and these results were consistent with the changes of the activities assayed in solutions. These results suggest that SOD, POD, CAT and PAL, may play an important role in the defensive mechanisms of Jatropha curcas seedlings exposed to excessive zinc. (c) 2010 Friends Science Publishers