Effects of salt stress on growth, antioxidant enzyme and phenylalanine ammonia-lyase activities in Jatropha curcas L. seedlings

The effects of increasing NaCl concentrations on biomass, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) in Jatropha curcas L. seedlings were investigated. The fresh weights of cotyledons and radicles with increasing NaCl concentrations decreased progressively, and the fresh weight of hypocotyls reached the lowest level at NaCl concentration of 150 mmol and then increased. SOD activity in the cotyledons, hypocotyls and radicles increased gradually up to NaCl concentrations of 150, 200 and 150 mmol, respectively. The highest POD activities in the cotyledons, hypocotyls and radicles were observed at NaCl concentrations of 150, 200 and 150 mmol, respectively. CAT activity in the cotyledons, hypocotyls and radicles enhanced gradually up to 100, 200 and 150 mmol NaCl concentrations, respectively. Increased PAL activity in the hypocotyls and radicles was linearly and positively correlated with increasing NaCl concentrations, but the peak activity in the cotyledons was observed at NaCl concentration of 150 mmol. Electrophoresis analysis suggested that different patterns in SOD and POD isoenzymes depend on NaCl concentrations and organ type, and the staining intensities of these isoforms are consistent with the changes of enzyme activity assayed in solutions.