Interactive effects of nitrogen and pH on four physiological indicators of chicory

A experiment was carried out to determine the interactive effects of nitrogen and pH with on chlorophyll and malondialdehyde (MDA) content, peroxidas (POD) and superoxide dismutase (SOD) activity of chicory (Cichorium intybus) by completely random combination of three nitrogen concentrations (65.305 mgL-1, 130.610 mgL-1 and 261.122 mgL-1) and three pH levels (5.5, 7.0 and 8.5) in the sand culture. The results of this study showed the application of nitrogen did not affect the chlorophyll and MDA content but significantly affected the POD and SOD activity. The pH value significantly affected the chlorophyll but did not affected the MDA content, and increased the activity of POD and SOD. the interaction of nitrogen and pH had significant effect on chicory growth, indicating that the chlorophyll content were greatest with 65.305 mgL-1 N and pH 5.5, and it increased as N concentration increased; the MDA content were lowest with 261.122 mgL-1 N and pH 5.5, and it kept stable when only N or pH stress was applied; the POD and SOD activity were highest with 261.122 mgL-1 N and pH 8.5, and it changed significantly when only N or pH stress was applied.